Shape memory alloys have attracted a lot of attention due to their various features but have also led to some reluctance in application due to the complexity of understanding and thus handling of their constitutive behavior. This paper tries to explain how such a complexity can be managed by simply considering a SMA's configurable passive damping behavior in a first step. The whole process chain from analytically handling a SMA, its integration into a SMA composite, the SMA performance with regard to damping, manufacturing of the SMA composite up to design, and manufacturing and performance of a SMA composite aerodynamic profile will be discussed. Rise will also be given as to how algorithms for structural optimization can be better used for identifying optimum configurations of smart composites leading to a true light weight design.

An important aspect of the evolving smart structure concept is the development of automated health monitoring of structures. Monitoring particularly deals with the tracking of particular characteristics of some critical parameters of a structure using one or more technologies. The aim of the present paper is to examine the role of MEMS and Photonics technologies in SHM and review the current status. Also presented are some aspects of work done at IISc, particulary in regard to Bragg Grating Sensors.

Rare-Earth (RE) was implanted to GaN epitaxial layer. Eu-implanted GaN films were annealed at the temperature range of 950 - 1100°C to reduce the implantation damages. Photoluminescence (PL) properties were measured, and strong emission at 621 nm corresponding to the transition from ⁵D₀ to ⁷F₂ states of Eu³⁺ was observed. The thermal quenching of PL intensity was very small and the peak position was not shifted. Large hardness for high energy electron-induced damages was observed.

The microelectronics industry has seen explosive growth during the last thirty years. Extremely large markets for logic and memory devices have driven the development of new materials, and technologies for the fabrication of even more complex devices with features sizes now down at the sub micron and nanometer level. Recent interest has arisen in employing these materials, tools and technologies for the fabrication of miniature sensors and actuators and their integration with electronic circuits to produce smart devices and systems. This effort offers the promise of: (1) increasing the performance and manufacturability of both sensors and actuators by exploiting new batch fabrication processes developed including micro stereo lithographic and micro molding techniques; (2) developing novel classes of materials and mechanical structures not possible previously, such as diamond like carbon, silicon carbide and carbon nanotubes, micro-turbines and micro-engines; (3) development of technologies for the system level and wafer level integration of micro components at the nanometer precision, such as self-assembly techniques and robotic manipulation; (4) development of control and communication systems for MEMS devices, such as optical and RF wireless, and power delivery systems, etc. A novel composite structure can be tailored by functionalizing carbon nano tubes and chemically bonding them with the polymer matrix e.g. block or graft copolymer, or even cross-linked copolymer, to impart exceptional structural, electronic and surface properties. Bio- and Mechanical-MEMS devices derived from this hybrid composite provide a new avenue for future smart systems. The integration of NEMS (NanoElectroMechanical Systems), MEMS, IDTs (Interdigital Transducers) and required microelectronics and conformal antenna in the multifunctional smart materials and composites results in a smart system suitable for sending and control of a variety functions in automobile, aerospace, marine and civil strutures and food and medical industries. This unique combination of technologies also results in novel conformal sensors that can be remotely sensed by an antenna system with the advantage of no power requirements at the sensor site. This paper provides a brief review of MEMS and NEMS based smart systems for various applications mentioned above. Carbon Nano Tubes (CNT) with their unique structure, have already proven to be valuable in their application as tips for scanning probe microscopy, field emission devices, nanoelectronics, H₂-storage, electromagnetic absorbers, ESD, EMI films and coatings and structural composites. For many of these applications, highly purified and functionalized CNT which are compatible with many host polymers are needed. A novel microwave CVD processing technique to meet these requirements has been developed at Penn State Center for the Engineering of Electronic and Acoustic Materials and Devices (CEEAMD). This method enables the production of highly purified carbon nano tubes with variable size (from 5 - 40 nm) at low cost (per gram) and high yield. Whereas, carbon nano tubes synthesized using the laser ablation or arc discharge evaporation method always include impurity due to catalyst or catalyst support. The Penn State research is based on the use of zeolites over other metal/metal oxides in the microwave field for a high production and uniformity of the product. An extended coventional purification method has been employed to purify our products in order to remove left over impurity. A novel composite structure can be tailored by functionalizing carbon nano tubes and chemically bonding them with the polymer matrix e.g. block or graft copolymer, or even cross-linked copolymer, to impart exceptional structural, electronic and surface properties. Bio- and Mechanical-MEMS devices derived from this hybrid composites will be presented.

This paper deals with the development of a general finite element formulation of the layerwise theory that was proposed and advanced by the first author for laminated plate structures with piezoelectric materials (layers or patches). The formulation includes full electromechanical coupling. Several approximations are used for the primary variables of the theory in the thickness direction and different interpolation schemes are considered in the surface directions. A very good agreement is obtained for the models using cubic approximation in the thickness direction. The advantages of these models on the prediction of layer stresses are fully illustrated.

Carbon Nanotubes (CNTs) can be considered as a sheet of graphite rolled in to a seamless cylinder, which exhibits unique electrical and mechanical properties. Based on the way of rolling the graphene sheets, there are three types of CNTs, armchair, zigzag and chiral tubes. Both the diameter and chiral angle determine the electronic properties of these nanostructures. In this paper we have studied the variation of the band gap as a function of chiral angle for various sets of lattice indices. The energy expression in the tight binding approximation is also obtained for the 2D graphene sheets with hexagonal lattice. In order to analyze the role of impurity, we have considered the impurity confined within these one-dimensional structures. By taking a suitable one-electron wave function we have obtained the <H>_min. For an impurity confined in CNTs.

9,10-Anthraquinone films have been prepared by hot wall epitaxy technique onto the glass substrate kept at different temperatures in a vacuum of 10^-5 Torr. The experimental conditions are optimized to obtain better crystallinity of the films. The films so prepared have been studied for their structural, optical and electrical properties. The IR and NMR studies confirmed the formation of 9,10-anthraquinone films. Crystallites as large as 0.61 μm are observed in the case of films deposited at 348 K. Observations reveal that the crystallinity of the films increases with increase in substrate temperature. The conduction in these films is found to be ohmic in nature and appears to take place by thermally activated hopping above intermolecular barriers. The electrical conductivity, carrier concentration and drift mobility of the films increase with increases in substrate temperature, whereas activation energy decreases. Analysis of optical absorption measurements on the films indicates that the interband transition energies lie in the range 3.16 - 3.44 eV.

Various oxides have been reported to be sensitive to humidity of the environment. Recently ceramic type humidity sensors using aluminates and ferrates are widely reported as stable sensors. The change in electrical resistance due to change in humidity is considered due to adsorption of water molecule in the pores of material. If the material has more active centers, it will yield better results. It is suggested that the protonic conduction is possible due to pores where H₃O⁺ and OH^- ions are formed due to moisture adsorption. The formations of protonic ions are possible if electrically active centers are present which will help to increase the sensitivity. It ^αis expected that in porous structure/surface the presence of dangling bonds may act as electrically active centers and facilitate the increase in sensitivity of the humidity sensor. The present paper reports the measurement of spin density of ferrates fired at different temperatures and correlates its humidity sensitivity with spin density. This explains that dangling bonds act as active centers and if the process of fabrication of humidity sensor increases the dangling bonds, it is possible to increase the sensitivity of the sensor.

Cadmium doped Tin Oxide Thin Films have been prepared by Spray Pyrolysis Method on glass substrates at 350°C. Structural, electrical and optical properties have been measured. From XRD it is found that films deposited are crystalline in nature with tetragonal structure having lattice constant a=b=3.86 A° and c=5.62A°. Hall effect measurements show that films prepared are of n-type and the carrier concentration (≈10¹⁸ cm^-3) and room temperature conductivity decreases with the increases in cadmium concentration in the films. Activation energy has been calculated from conductivity measurements and it was found that conduction within the temperature range we have measured is due to hoping of carriers through the spectrum of localized states. Band gap of the un-doped films calculated from transmission spectrum is about 3.1 eV and the value decrease slightly with the addition of cadmium. The refractive index, extinction coefficient, real and imaginary parts of the dielectric constant have been calculated from the optical spectra. The refractive index decreases with photon energy and also decreases slightly with cadmium concentration while extinction coefficient increases with photon energy.

The latest development of materials and technology for building smart chemical sensors has been presented. Different kinds of chemical sensors working on the principle of chemical and physical transductions have been individually discussed. The sensor mechanism in each case of detection of inorganic and organic vapors has been indicated. The merits and demerits of different materials and sensors structures have been mentioned. Finally the strategic applications of some innovative chemical sensors have been clearly cited.

Preparation and characterization of gas sensors based on thin films of SnO₂:Pd to monitor trace amounts of H₂S in air are reported. Sensors have been exposed to 100% relative humidity to study the incorporation of hydroxyl group (-OH) in the film and its effects on gas sensing properties. Films have been subsequently treated with dilute sulphuric acid and characterized using different techniques such as X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, IR spectroscopy and electrical resistance measurements. IR studies reveal the presence of two types of hydroxyl groups (-OH) in the film; as 'free surface -OH' and hydrogen bonded -OH. The two types of -OH have been found to affect the gas sensing properties in different ways. Chemical treatment of films with dilute sulphuric acid has been found to improve the H₂S sensing properties of the sensor by modifying the concentrations of the two types of hydroxyl groups.

Lanthanum modified lead titanate thin films with 20% of lanthanum content (PLT20) were prepared by laser ablation deposition technique. For the films deposited at 300°C, crystallization was induced by Rapid thermal annealing (RTA) process. The dielectric and electrical properties of PLT20 films were studied. The pyroelectric current was measured using Byer-Roundy technique. The RTA annealed films showed a dielectric constant of 482 and a loss factor of 0.033 at room temperature at 100 kHz frequency. The RTA annealed and insitu films showed 1100 x 10^-6 Cm^-2 K^-1 and 609 x 10^-6 Cm^-2K^-1 as pyroelectric coefficients respectively. A large pyroelectric coefficient of value 35000 μ Cm^-2 K^-1 was observed for the in-situ grown films at transition temperature. The figures of merit of current (F_i), voltage (F_v) and detectivity (F_D) were calculated for both the films and the obtained values for the in-situ grown thin films were 1.9 x 10^-10 CmJ^-1, 0.088 m² C^-1, 5.38 x 10^-5 pa^-1/2 respectively. The difference in the pyroelectric properties for the films was discussed and the effect of temperature on dielectric and pyroelectric properties were studied to understand the suitability of these thin film composition for the application of pyroelectric detectors.

A simple procedure has been employed for synthesis of ultra fine nanosized mesoporous TiO₂ in the anatase and both phases (i.e. anatase and rutile) using polyethylene glycol (PEG) as gelling, dispersion and filming agent in aqueous media. Inorganic titanate rather than alkoxide or organic metal complexes were used as precursors. The reaction temperature of 100°C was employed to produce mesoporous TiO₂. These moderate reaction conditions are attributed to utilizing PEG as a gelling agent for formation of TiO₂. Thus the TiO₂ powder prepared in this way was ultra fine (approximately 4 nm) and crystallized Anatase phase with a BET surface area as high as 299m²/g. Pore size is measured to be approximately 3.5 nm, a value in good agreement to that indicated by crystallite size calculated from XRD spectra using Scherrer's equation. Although the mesoporous structure of the TiO₂ powder was not thermally stable enough, and both the pore volume and surface area decreased after calcination at elevated temperature but ordered mesoporous structure still remained even after calcinations at 600°C along with large surface area of 66.3 m²g^-1. The TiO₂ sensor prepared in the present study exhibited higher H₂ and CO sensitivities than the sensor fabricated with commercial TiO₂ powder. Thus it was confirmed that the ability of TiO₂ powder as a sensor material could be improved by controlling the mesoporous structure.

Smart materials respond to environmental stimuli with particular changes in some variables (for example temperature, pressure and electric field etc), for that reason they are often called responsive materials. In the present work, we have synthesized thermochromic polymer based on poly acrylic acid cobalt chloride (CoCl₂) and phosphoric acid (H₃PO₄) that visually and reversibly changes color in the temperature range (70 - 130°C). These thermochromic materials can be used as visual sensors of temperature. Thermochromic polymers are based on polyacrylic acid and CoCl₂ complex.

A series of polyesters containing donor-acceptor π-conjugated polar segments (4,4'-azobenzene dicarbonyl chloride) and chiral building units [L(+)-diethyl tartrate] in the main chain were synthesized and characterized by spectroscopic (IR, UV-Vis, ¹H NMR, ¹³C NMR), thermal (TG/DTG, DSC), and optical (refractive index, optical rotation techniques). Chiral order was induced with a preferred helical sense to attain noncentrosymmetric ordering of dipoles (polar order) in macroscopic dimensions by chemical synthesis (chemical poling). A comprehensive attempt has been made to correlate the polar order of the polymer chains with the chiral order arising out of a preferred helical sense of the chains. This has been achieved by adopting four different theoretical models and comparing the results with the experimentally observed values of the second order polarizability tensor β. The models used are (1) Logarithmic Law of Mixing (LLM), (2) the Extended Boundary Condition Method (EBCM), (3) The Random Field Ising Model (RFIM) and (4) Semiempirical Computational Model (SCM). The results of the theoretical predictions are compared with the experimentally determined values of β.

The paper was revealed a fatigue in the alumina-chrome carbide composite. The trapped crack front resembles a collinear array of microcracks interspersed by grains rich in transformable precipitates. This micromechanical model provides a reasonable explanation for the observed fatigue crack growth. A numerical procedure similar to the one used in the analysis of the array of collinear cracks, based on complex potentials and dislocation formalism is also used to simulate fatigue of composite coatings based on oxide ceramics and chrome carbide. Assuming power-law crack growth, it is found that the crack growth rate decreases with the applied stress intensity factor in the initial stage of fatigue crack growth. Depending on the applied load and the amount of transformation, the growth rate either goes through a minimum before increasing to the normal crack regime, or the rate continues to decrease until the crack is arrested. A detailed parametric study of the phenomenon of fatigue crack arrest in composite coatings based on oxide ceramics and chrome carbide reveals that the combination of transformation strength parameter and applied load determines whether or not crack arrest will occur, irrespective of the initial crack length. Based on the parametric study a simple linear relationship between the applied load and the minimum transformation strength parameter necessary to cause crack arrest has been developed. it will be found useful in the design against fatigue by predicting the maximum toad at which crack arrest can be expected.

This paper deals with the rate and time dependent electrical and mechanical properties of Biaxially stretched Form I PVDF and modeling those properties. Experiments have been done to characterize the rate and time dependent mechanical behavior of PVDF and the rate dependent electrical properties of PVDF. The rate dependent mechanical property of PVDF has been modeled through a Kelvin solid with fractional dashpot and nonlinear spring assuming incompressibility. It is shown in this paper using the model, that the viscoelastic behavior of PVDF is similar to that of a Non-Newtonian fluid. The model predicts the response of PVDF properly within the range or 12% strain. The time dependent behavior of PVDF is modeled through a power law model.

Polycrystalline samples of alkali ions doped PLZT ceramics were synthesized by Sol-Gel process. The doped ions were Li, Na and K. Structural properties of the compounds were examined through X-ray diffraction technique. The pellets of the compounds were sintered at four different temperatures. The effects of sintering temperature on the dielectric properties of the ceramics were examined. Studies reveal that the dielectric properties of the compounds are very sensitive to the method of preparation and the sintering temperature.

Thin films of (1-x)Pb(Mg_1/3Nb_2/3)O₃ - xPbTiO₃ (x = 0.1 to 0.3) (PMN-PT) were grown on the platinum coated silicon substrate by pulsed excimer laser ablation technique. The composition and the structure of the films were modulated via proper variation of the deposition parameters. A room temperature dielectric constant varying from 2000 to 4500 was noted for different composition of the films. The dielectric properties of the films were studied over the frequency range of 100 Hz - 100 kHz over a wide range of temperatures. The films exhibited the relaxor- type behavior that was characterized by the frequency dispersion of the temperature of dielectric constant maxima (T_m) and also diffuse phase transition. This relaxor nature in PMN-PT thin films was attributed to freezing of the dipole moment, which takes place below a certain temperature. This phenomenon was found to be very similar to spin glass systems, where spins are observed to freeze after certain temperature. Antiferroelectric lead zirconate (PZ) thin films were deposited by pulsed laser ablation technique on Pt coated Si substrates. The films that were deposited at a lower temperature of 300°C with subsequent post annealing at 650°C for 5 min. (ex-situ films) exhibited polycrystalline multi-grained microstructure, whereas the films that were deposited at a higher substrate temperature (in-situ films) of 550°C exhibited highly oriented (110) columnar microstructure. The antiferroelectric nature of the PZ films was confirmed by the double hysteresis behavior in polarization vs. applied electric field characteristics. These two films showed a difference in the dielectric and electrical properties and were attributed to the difference in their microstructure.

Alumina coating modified by ultra-dispersed diamonds (UDD) have been produced by combination of thermal flame spraying and micro arc oxidizing technologies on sprayed aluminum substrate was. Structures of alumina-based ultra dispersed diamond particles composite coatings were investigated in detail by transmission electron microscopy and SEM imaging. The particles were deposited with alumina layer on aluminum substrates under various conditions and have different levels of strength, hardness and internal stresses. It was revealed that by UDD strengthening the coating is to have high microhardness of 22 - 26 GPa, fine structure and smooth surface. Diamonds was found to be conglomerated in clusters along the interface obtained with high current density, but it disappeared when deposited with lower current regimes of alternating pulse current. On the other hand, the failure of crystal diamonds became smaller with decreasing current density concentrations. From the correspondence between the structures and the hardness of the composite, it was suggested that the effect of ultra dispersed diamonds resulted in the complicated trend of hardness, strength and fine structure with respect to current density and diamonds concentration in the electrolyte. In view of technological setup pulse current regime at high current frequency improve microhardness and roughness of the coatings. Potential application of the coating is sliding bearings, insulators, aerospace units.

Ta(N) film was synthesized by implanting the nitrogen ions in Ta films employing Plasma Immersion Ion implantation (PIII) technique. Silicon wafers coated with Ta were implanted with nitrogen at two different doses. Nitrogen ions implanted in the film render it to become Ta(N), which in effect hinders the grain boundary diffusion. The ion implantation was carried out for two doses 10¹⁵ions/cm² and 10¹⁷ions/cm² corresponding to low and high dose regime. Thereafter a copper layer was deposited on the samples to produce Cu/Ta(N)/Si structure. To evaluate the barrier properties of Ta(N) these samples were annealed up to 700°C for 30 minutes. Sheet resistance, X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM) measurements were carried out to investigate the effect of annealing.

Smart fluids such as magnetorheological and electrorheological fluids which respond to magnetic and electric stimuli have been known for the last few years. The present paper reports development of a new magnetorheological fluid based on an agro seed oil. Carrier fluid based surfactant has been used to stabilize magnetic particles in the fluid. The fluids initial viscosity is around 300 CPs and when a magnetic field of approximately 0.7 tesla is applied, the viscosity rises to 1.3 x 10⁷ CPs. A variable torque transfer hydraulic coupling device has been developed using this new magnetorheological fluid. The torque transferred can be controlled as a function of the applied magnetic field around the fluid. The paper discusses the general fluid formulation, the influence of magnetic field on the viscosity of the fluid, the relationship between shear stress and applied magnetic field, torque transfer and applied magnetic field, torque transfer and initial viscosity of the fluid etc. Photographs showing experimental set up for the viscosity measurements, and hydraulic coupling device developed are included.

Single crystals of the relaxor ferroelectric solid solution family Pb(Zn_1/3Nb_2/3)O₃-PbTiO₃ (PZN-PT) have been shown to produce very high levels of electric field induced strains with large electromechanical coupling coefficients when poled aong the <001> direction. These materials also exhibit a high dielectric permittivity and they are therefore very promising materials for transducer and actuator applications. We have carried out a systematic investigation of the dielectric and piezoelectric properties of different compositions, using specimens manufactured by TRS Ceramics Inc. Both the dielectric and piezoelectric strain responses of these crystals have been studied as a function of temperature and applied electric field. The applied field and temperature dependences of the rhombohedral to tetragonal and the tetragonal to cubic phase transitions have been determined. Our results suggest that a DC bias field can be used to stabilize the tetragonal phase. The strain measurements have been used to determine the d₃₃ values in both phases as a function of temperature. The PZN-PT crystals have their polar direction along the <111> axis but not much has been reported on the piezoelectric properties of crystals poled in this direction. We have used laser Doppler interferometry to measure the piezoelectric strains as a function of DC bias field applied in the <111> direction in PZN-PT crystals and we have determined values of the piezoelectric coefficients as a function of the DC bias field. High d₁₅ values over 3000 pC/N have been observed along <111> direction.

Equations, in the IEEE Standard, for finding the coefficients of piezoelectric materials are based on one-dimensional models of slabs, rods, and discs. In the Standard, recommendations are also made for the sizes of samples to be used for characterization. The errors in the coefficients of samples determined using the Standard are presented here. The errors are, in effect, determined by using three-dimensional finite element models to determine the coefficients and comparing them with those determined using the Standard equations. It is difficult to find the piezoelectric coefficients using a three-dimensional model and measured quantities such as the input electrical admittance. Therefore, the quantities that are required as input to the Standard equations are first computed using a set of piezoelectric coefficients and a three-dimensional finite element code, ATILA. These quantities are then used to find the coefficients. The difference between the coefficients input to ATILA and those obtained from the Standard equations is the error. The error is computed for slabs, rods, and discs of various sizes. Some sizes satisfy the Standard recommendations but most do not. The error is small in several cases. This is of significance for transducer developers who use samples of non-Standard size.

Lead zirconate titanate, Pb(ZrTi)03 (PZT), a solid-solution of ferroelectric PbTiO3 (Tc=490°C) and antiferroelectric PbZrO3 (Tc=230°C), with varying Zr/Ti ratios has wide industrial applications. The variation of Zr/Ti ratio and the suitable substitutions at A/ or B sites influence the physical properties and/or device parameters of PZT to a great extent. The La modified PZT (PLZT) of different Zr/Ti ratios and La concentrations has been studied extensively using various methods. It is therefore interesting to explore the possibilities of fine-tuning the characteristics of PLZT (8:60:40) with the help of an additional dopant at the La site. Here we report our work on synthesis and characterization of La, Bi ions doped PZT piezo ceramics.

The structural, dielectric and piezoelectric properties have been studied in detail for the samarium modified PZT system. The samples, with chemical formula Pb_1-xSm_xZr_0.52Ti_0.48O₃ with x varying from 0 to 0.02 in steps of 0.0025, were prepared by standard double sintering ceramic method. XRD analysis showed all the samples to be of single phase with tetragonal structure. Tetragonality (c/a) decreases gradually with samarium concentration (x) and the experimental density increases with x. Dielectric properties were studied as a function of temperature and frequency. All the samples show well-defined ferroelectric behavior. The remanance ratio (P_r/P_s) was found to increase with increasing Sm³⁺ concentration. Piezoelectric charge coefficient d₃₃ decreases with x.

Studies on the effect of 10 - 50 atomic % Ca doping on structural distortions are reported in the present work. Bismuth layered structured ferroelectrics oxides of the composition Sr_1-xCa_xBi₂Nb₂O₉; with x = 0.0 - 0.5 were synthesized by the solid-state reaction method. X-ray diffraction analysis revealed the formation of perovskite ferroelectric ceramic sample and a few additional peaks were observed as concentration of calcium varied from 10 to 50%, gradual shift in peaks with doping is discussed with respect to observed anomalous change in lattice parameters. Also, transformation of structure from pseudo-orthorhombic to pseudo-tetragonal phase is observed at room temperature as concentration of calcium is increased. This suggests that structural distortions are pronounced in such a manner so as to stabilize the structure of unit cell, which may lead to high value of Curie temperature and remanent polarization useful in non-volatile random access memory (NvRAM) devices.

Ethanol sensitivity of bismuth molybdate thick films and sintered pellets were investigated. Sintered pellets were prepared by traditional ceramic processing. Thick films were prepared by metallorganic decomposition process. Ethanol gas sensitivity was measured at various temperatures and concentrations. Thick films of alpha phase bismuth molybdate prepared by spray pyrolysis showed a very fast response to ethanol detection. The response time for the bulk samples is about 40 sec which decreased to about 6 sec for thick films at an operating temperature of 300°C. An extremely low level approximately 10 ppm detection and fast response makes this technique ideal for sensor element fabrication for detection and estimation of alcohol in breath-analyzer. Unlike SnO₂, the resistance of these sensors is not affected by humidity at the operating temperature.

This paper presents a comprehensive description of the physical interactions in a piezoelectric material used in development of smart structures. The governing electro-thermo-elastic equations for the analysis of smart structures have been developed from the fundamental laws of conservation and thermodynamic principles. A brief description of the application of smart technology to rotorcraft is also presented.

Coupled electro-thermo-elastic equations applicable for the analysis of smart structures have been derived. These governing equations have been used to obtain the deformation of a smart beam under the action of external mechanical load and an electric potential. The results of the present study have been compared with those available in literature. The present study brings out the essential difference between sensing and actuation phenomena by solving for the electric potential and the deformation variables in the piezo material.

With present day scenario on enviornment and living, unanticipated loads from natural and man-made causes are on the rise, defying any rationality or scientific reasoning for anticipation. This aspect, coupled with the interest in creating slender and sleek structural systems, has assumed greater significance in designing structures with 'smartness' -- either in-built or externally activated or through evolution to a different configuration -- for tackling loads which do not get bracketed in conventional or limit state approaches. The definition of smartness under these circumstances can be termed as the ability to carry unanticipated loads over and above the designed one. Although the design methodology is confined within the boundaries of codal and functional requirements, a "buffer" needs to be built in the design so that an extra reserve is available over and above that prescribed by normal approach. This might seem misleading and here only the present day computing methods provide the turn-around by shifting the paradigm from "design-for-requirement" to "requirement-from-designs," an Object Oriented Approach. Thus the focus on present paper is on choosing from different designs to satisfy "buffer requirements" to bring in "smartness" in the design choice. Reinforced concrete section under bending is the emphasis to highlight this aspect, even though the concept is expandable. For a given span, and design/ultimate moment, sections are chosen to provide buffer and compared with conventional designs. Nonlinear behavior is modeled so that failure state is kept as the endpoint. From the studies it is observed that for a given span, moment -- either ultimate or design state -- and given strengths, number of "smart designs" with buffer indications can be generated to satisfy different criteria. This is illustrated with some examples for a typical span and given external moment, modeling either a bridge section or part of a frame member. It was also observed from the studies that there is no unique design that satisfies all parameter simultaneously. A section that performs well in terms of cost and weight may yet fail in terms of buffer or utilization of steel upto its limit. Whereas a section that performs moderately in every one of the parameter may still be a better option. Depending upon the requirement, weightages for performance with respect to resisting moment, cost weight and additional buffer capacity must be specified. The section that best satisfies all the above criteria could be chosen as the ideal section. Section design done by varying other parameters such as grade of steel and concrete can also be studied. Strain hardening in steel can also be investigated to arrive at the greater carrying capacity of the sections. For example, it may even be possible for a structure to be designed purely for dead load and live load. But inherent smartness can be induced to take care of seismic loads either partly or even completely.

The electro-mechanical (EM) impedance method is gradually emerging as a widely accepted technique for structural health monitoring and systems identification. The method utilizes smart piezoceramic (PZT) transducers intimately bonded to the surface of a structural substrate. Through the unique electro-mechanical properties of the PZT transducers, the presence of damage, as well as the dynamical properties of the host structure are captured and reflected in the electrical admittance response. In the present work, the effect of the bond layer on the electro-mechanical response of a smart system is being studied. Experiments with the EM impedance method were performed on laboratory-sized beams. Consequently, the effects of shear lag due to the finite thickness bond layer were successfully identified. This was followed by the theoretical analysis of shear lag effects. It was found that the induced strain behavior of the structural specimen in question is inevitably modified by the presence of shear lag between the PZT transducer and the structural substrate. Subsequently, the EM admittance response of the beam specimens were simulated based on the results gathered from the theoretical analysis. Incidentally, it was found that the theoretical model clearly depicts the trends of the measured response.

Magneto-optic imaging (MOI) is a relatively new technology that produces analog images of magnetic flux leakage from surface and subsurface defects. An alternating current carrying foil serves as the excitation source and induces eddy currents in a conducting test specimen. Under normal conditions, the associated magnetic flux is tangential to specimen surface. Anomalies in the specimen result in generating a normal component of the magnetic flux density. The magneto-optic sensor produces a binary valued image of this anomalous magnetic field. The current system has two shortcomings. First, the presence of a textured background due to the domain structures in the sensor makes detection of third layer cracks and corrosion difficult. Second, the qualitative nature of the MO images does not provide a basis for making quantitative improvements to the MOI system. The availability of a theoretical model that can simulate the MOI system performance is extremely important for the optimization of the MOI sensor and hardware system. This paper presents a finite element model and its use in understanding the capabilities of the MOI system. In addition the paper also presents signal-processing methods for eliminating the background noise.

This paper discusses about the extension of Gabor Expansions to the optical domain and the design of an efficient filter bank to provide adaptive equalization in the light of Optical Signal Processing. The isomorphism between this localized linear operator and the filter design fundamentals are examined in the framework of image sequence compression. A new and efficient technique to perform Gabor expansion of Optical signals is introduced. The multi-resolution representation of data is considered in particular. A new approach to filter bank design in optical domain, using matrix formulation is introduced. Using this approach, an efficient optical filter bank with low complexity and good frequency response is designed. It is interesting to note that this design is a mathematical model of the quincunx filter bank. The characteristics of this optical filter bank are compared with that of other commonly used short kernel filter banks, for video compression applications. The approach is based on multi-resolution representation of data, which is generated by the filter bank proposed in this work. The use of multi-resolution data structure in conjunction with other components of the system allows a simple and efficient implementation. Simulations on typical image sequences show that it is possible to perform generic coding with reduced complexity and good efficiency.

In recent years, the piezoelectric-ceramic (PZT) patches are increasingly been used as impedance transducers for non-destructive evaluation (NDE) of structures. In this application, the electrical admittance of a PZT patch surface bonded to the structure is utilized as a diagnostic signature of the structure. The operating frequency is typically maintained in the kHz range for optimum sensitivity in damage detection. The electro-mechanical interaction between the host structure and the bonded patch is key to the detection of damage in this NDE technique. Although the method is well established for a wide variety of structures and material types, very little research has focused on the fundamental structure-PZT interaction. This paper reviews the fundamental electro-mechanical coupling between the structure and the PZT patch and introduces a new concept of 'active' signatures, whereby it is possible to utilize the direct interactive component of the signature for NDE afte filtering the 'inert' component. Consequences of this concept, which include increased sensitivity to damage and reduced influence of temperature fluctuations on signatures are highlighted.

The proposed shock isolator is a single degree of freedom model where the payload mass is isolated from base disturbances by varying the stiffness of the spring. One spring always forms an interface between the mass and the base. The other spring makes or breaks contact with the base with the help of magnetorestrictive actuator depending upon the magnitude of the relative velocity. The actuator develops the required force that acts normal to the sliding surfaces of the spring and the base to produce the necessary coulomb friction force for locking the spring with the base thus altering the stiffness. The magnetorestrictive material considered here is Terfenol-D that responds to an external magnetic field proportional to the surrounding coil current. The actuator is switched on/off depending upon the magnitude of the relative velocity which in turn reduces or increases the stiffness of the isolator and thus provides the control on response. The performance of the proposed isolation and control scheme is evaluated in terms of the shock acceleration ratio and the relative displacement ratio across the isolator. A mathematical model for the proposed shock isolation system is developed and simulation results show that the performance of the proposed scheme is better when compared with that of a passive isolator for rounded pulse and rounded step displacement excitations at the base.

Buckling frequently governs the strength of weight sensitive aerospace structures. Conventional designs use adequate mass of material located appropriately to obtain adequate buckling strength. The smart control and material technologies have created a new paradigm in design. In this smart structures, energy to control their behavior and appropriate control strategies are used to design against buckling failure. In this paper the state-of-the-art of smart control of buckling is reviewed and finite element analysis results of an approach to control buckling of struts under compression is discussed.

The problem of modeling and control of displacement, force excited single degree freedom structure and displacement excited two degree of freedom structure with ER fluid damper is presented. A Sliding Mode Controller (SMC) is designed and applied to control seismically excited vibrations in these structures. The performance of SMC is compared with Lyapunov's direct method based controller.

In an attempt to develop piezoelectric sensor and actuator for smart board, complex piezoelectric fibers with metal core were fabricated by both hydrothermal method and extrusion method. The insertion of metal core was significant in view that the fragility of ceramics is overcome and electrodes are not required in the use as sensor and actuator. In order to evaluate the sensor and actuator abilities of these new-type fibers, a cantilever structure was constructed by embedding them into the surface of CFRP composite board. As a result of vibration of this CFRP board by electromagnetic vibrometer, it was found that the fiber has an obvious sensor function, since electric charge was output from the fiber in proportion to the vibration amplitude. On the contrary, it became also evident that the fiber functions as actuator, since the CFRP board was vibrated by applying an AC voltage between the metal core and CFRP matrix. It seemed likely that the hydrothermal fiber is adequate to sensor use, while the extruded fiber is suitable for actuator use because of the higher actuator power.

In this work, the shape control of curved beams using symmetric surface bonded piezoelectric actuators, excited out of phase, is studied. To predict the deflections accurately, a finite element model using a three-noded isoparametric curved beam element has been implemented. To model the piezoelectric layers, coupled finite element equations have been used and solved using iterative approach. Closed form expression for deflection has also been derived and compared with FEM and experimental results. The closed form solution based on linear strain variation is used for the static shape control of curved beams. Shape control is achieved by minimizing an objective function, which takes into account the error between actual and desired shapes as well as energy consumed by the actuators.

This paper summarizes the studies on meshfree point interpolation method (PIM) for static and dynamic analysis of piezoelectric structures. In the PIM methods, the problem domain is represented by a set of properly scattered nodes. The displacements and the electric potential of a point are interpolated by the values of nodes in its local support domain using shape functions derived from point interpolation scheme. Galerkin formulation is used to establish a set of system equations for arbitrary-shaped piezoelectric structures. Numerical examples are presented to demonstrate the validity and convergence of the present method and their results compare well with the conventional FEM results from ABAQUS as well as the experimental ones.

A new element is developed for the analysis of laminated/sandwich beams incorporating piezoelectric layers. Beam theory employed here satisfies the interface stress and displacement continuity and has zero shear stress on the top and bottom surfaces of the beam. Piezoelectric layers can be placed arbitrarily and can act as sensors and actuators. The transverse shear deformation in the form of trigonometric sine function is incorporated to define the transverse shear strain. The displacement and stress variations along the length and thickness obtained are presented.

Piezoelectric materials are being explored for shape and vibration control. In this paper Finite Element formulation for analyzing general shell structures under the influence of piezoelectric actuators is presented. Reduced integration is carried out to overcome problem of shear locking, and integration is carried out numerically in all three directions to obtain accurate results. The FE formulation is compared with the current literature. Experiments are conducted on curved beams and experimental results are compared with the current Finite Element formulation. Non-linearity is observed at higher voltages. Typical FEA results on a doubly curved hemispherical shell are also presented.

This paper presents Finite Element analysis of structures with surface bonded piezoelectric patches. The objective of the present investigation is to develop layered piezoelectric elements which can be combined with the plate bending elements in a general purpose software such as MSC/NASTRAN, as a sensor/actuator for the analysis of smart structures. After thorough validation, numerical results are generated for various piezo-electric parameters.

This paper mainly reviews the current status of the LIGA fabrication technology for use in microfluidics applications. It also presents the work that the group is involved in the fabrication of 3-D high aspect ratio structures. This work explored the possibility of using LIGA and excimer laser micromachining as complimentary processes in two sequential steps for making some of the components required for fluidic applications. A microflask is designed and fabricated using this combination of processing technology. The details of the design and fabrication technology are presented in this paper.

Optics/opto-electronics has already proved its successfulness over electronics in the field of computation. There are lots of proposals reported in this field exploiting the inherent advantages of optics. Here in this communication we report an opto-electronic and all-optical 'flip-flop' used as memory/storage unit for developing a super-fast computing system by the exploitation of proper non-linear character of some materials.

A large number of single crystal Si micro-probes on Si(111) were fabricated selectively using VLS (Vapor-Liquid-Solid) growth method after IC process. The Si probes can be grown with a high aspect ratio more than a few hundreds. A diameter of the probes can be controlled from sub-micron to a few hundred microns. The Si probe position on the chip is also controlled and the chip with IC circuits can work even after the Si probe growth. Conductivity of the Si probes was controlled by using phosphorous diffusion, resulting in a resistivity of 10^-2 Ω•cm from 10⁴ Ω•cm for a diffusion temperature of 1100°C. In in-vivo studies, penetrating micro-probe array of low impedance such as the VLS growth Si probes has been desired, therefore electrical and mechanical properties were studied detected successfully.

Anisotropic etching of (100) single crystal silicon (SCS) in potassium hydroxide (KOH) -- water solutions and Ethylene diamine pyrocatechol (EDP) -- water solutions has been investigated for fabrication of a seismic mass -- spring structure used in inertial accelerometers. The vertical anisotropic etching rate and lateral undercut rates have been experimentally determined in both the cases. For EDP the effect of temperature on the etching rates have been found to follow an Arrhenius type of temperature dependence. The activation energies vary from 0.17 eV to 0.58 eV for EDP solutions of varying concentration. The effect of addition of iso-propyl alcohol to KOH have resulted in reduction of etching rates. The basic design rules for etching a seismic mass structure with vertical end walls on (100) silicon wafer are highlighted.

Polysilicon layers deposited by Low Pressure Chemical Vapour Deposition (LPCVD) on sacrificial oxides are used for surface micromachined structures. Stiction is a major problem in surface micromachining both during processing and in use. Contact angle measurements on surfaces can give indication on the adhesivitiy of the surface. In this paper, contact angle measurements on polysilicon surface after different treatments are reported with a view to understand their stiction behavior. We also report on surface roughness measurements on these samples.

The structural and dielectric properties of Ba_1-xSr_xFe_0.01Ti_0.99O₃ with x = 0.30 were investigated and compared following different sintering techniques (conventional and microwave) in order to optimize the materials for tunable microwave applications. The microwave sintering has been advantageous over the conventional sintering because it has very fast heating rate and thus saving processing time. In the present study, it has been found that the tunability of the conventionally sintered samples is higher than the microwave sintered ones. It can be explained due to the fact that the grain size is larger for the conventionally sintered specimen. The internal stresses among the grain affect the macroscopic value of the dielectric constant above the Curie point. The tunability is larger for the larger grain size samples as the effect of internal stress is less in this case.

Non-ionic dielectric polymers have not been considered adequate for electroactive actuator materials because of their poor reaction to the electric field. As electroactive polymeric materials, the polyelectrolytes and conductive polymers have been investigated intensively, since they can show large deformation in aqueous media or in the presence of water as an additive. In this paper, the author will show the non-ionic polymeric materials can be used as electrically active materials. The electrically induced deformation phenomena that will be shown are contraction and relaxation, bending by solvent drag in the gel, crawling deformation, and "electrotactic" amoeba-like creep deformation. And the controlling factors of bending of elatomers. The materials that will be treated in this presentation covers from highly swollen dielectric gels through plasticized polymers to non-solvent type elastomers. Characteristics of the actuations are particularly large deformation or huge strain under much smaller energy dissipation compared to the conventional polyelectrolyte or conductive polymer actuators. Applications of the materials for pumping, valve, artificial pupil etc. will be demonstrated.

Magnetorheological fluid, Electrorheological fluid and ferro fluids are the smart fluids known today. These fluids are either electrically conductive or non conductive. They do not exhibit variable electrical resistance or switching behavior. Of recent interest to researchers has been the development of new types of magnetoresistive materials. Such materials can be of large practical importance, as they will change their electrical resistance in the presence of a magnetic field. However, most materials only exhibit appreciable magnetoresistance under extreme conditions, such as high magnetic fields or low temperatures. A smart fluid whose electrical resistance can be varied by several orders of magnitude under nominal level of magnetic field is reported in this paper (designated MARSONPOL). In the absence of a magnetic field the fluid is an insulator having electrical resistance in the order of 10⁸ ohm-meter and in the presence of a magnetic field the resistance of the material reduces to less than 1 ohm-meter, at room temperature of 30°C. The sharp and reversible change in resistivity makes the material transform from an insulator to conductor, rendering properties characteristic of either state, within a fraction of a second. Fluids with such characteristics are not reported in the literature making this development a breakthrough and opening up potentials for the development of several smart devices. One such device is the magnetic field sensor probe currently under development at NPOL. A capsule of MARSONPOL forms the basic sensor element. Depending on the strength of the Magnetic field, the electrical resistivity of the capsule undergoes changes. The present paper will discuss details of the smart fluid as well as features of the magnetic field sensor.

Polycrystalline Si (poly-Si) films can be deposited at low substrate temperature by means of a pulsed discharge sputtering of a Si wafer target in pure hydrogen at high gas pressure of about 13 Torr, and microstructures of the films are investigated by using transmission electron microscope. Stable discharge at high gas pressure become possible by the pulsed discharge method. The discharge and non-discharge time at each period of the pulse in the present experiments are 0.35 and 2 ms, respectively. When the deposition time is 0.5 h, both an amorphous SiO₂ parent phase and poly-Si grains are exist in the film, and these structures changes to the poly-Si film at longer deposition time due to not only growth and aggregation of the crystalline grains but also structural change of the parent phase. The film is not deposited when the sputtering is performed with an argon gas instead of the hydrogen. These results suggest that the poly-Si is grown by the reactions of SiH_x species formed by reactions between the Si target and the atomic hydrogen and elimination of amorphous components by atomic hydrogen.

Insects are blessed with a very efficient yet simple visual system which enable them to navigate with great ease and accuracy. Though a lot has been done in the field of insect vision, there is still not a clear understanding of how velocity is determined in biological vision systems. The dominant model for insect motion detection, first proposed by Hassentein and Reichardt in 1956 has gained widespread acceptance in the invertebrate vision community. The template model, proposed later by Horridge in 1990, permits simple tracking techniques and lends itself easily to both hardware and software. Analysis and simulation by Dror suggest that the inclusion of additional system components to perform pre-filtering, response compression, integration and adaptation, to a basic Reichardt correlator can make it less sensitive to contrast and spatial structure thereby providing a more robust estimate of local image velocity. It was found from the data obtained, from the intracellular recordings of the steady state responses of wide field neurons in the hoverfly Volucella, that the shape of the curves obtained, agreed perfectly with the theoretical predictions made by Dror. In order to compare it with the template model, an experiment was done to get the velocity response curves of the template model using the same image statistics. The results leads us to believe that the fly motion detector emulates a modified Reichardt correlator.

This paper presents architecture of a low power digital clinical ASIC based on NTC thermistor for body temperature measurement. The thermistor coupled externally to a low power astable multivibrator modulate its pulse width. The modulated pulse width is detected in terms of the number of clock pulses counted by a counter. He counter output is processed by on chip processor to display temperature. The ASIC supports many advanced features like self configuration, prediction and self calibration and correction.

Stereolithography is the most popular RP process in which intricate models are directly constructed from a CAD package by polymerizing a plastic monomer. The application range is still limited, because dimensional accuracy is still inferior to that of conventional machining process. The ultimate dimensional accuracy of a part built on a layer-by-layer basis depends on shrinkage which depend on many factors such as layer thickness, hatch spacing, hatch style, hatch over cure and fill cure depth. The influence of the above factors on shrinkage in X and Y directions fit to the nonlinear pattern. A particular combination of process variables that would result same shrinkage rate in both directions would enable to predict shrinkage allowance to be provided on a part and hence the CAD model could be constructed including shrinkage allowance. In this concern, the objective of the present work is set as determination of process parameters to have same shrinkage rate in both X and Y directions. A genetic algorithm (GA) is proposed to find optimal process parameters for the above objective. This approach is an analytical approach with experimental sample data and has great potential to predict process parameters for better dimensional accuracy in stereolithography process.

We report the design, fabrication and performance of the 5 x 2 pixel uncooled microbolometer array. The test microbolometer utilizes pulsed laser deposited vanadium oxide film at room temperature as the IR sensitive layer. The microbolometer was fabricated without air-gap thermal isolation structure and the pixel area of about 200 x 800 μm². The observed change in bolometer resistance with respect to temperature (dR/dT) as high as 9.3 x 10³ Ω/°C and temperature coefficient of resistance (TCR) of about 5%/°C at room temperature, implies an excellent bolometric response. The room temperature deposition of the IR sensing layer facilitates their integration with the existing complementary metal-oxide-semiconductor (CMOS) technology for better signal processing. IR response of the device was evaluated in the spectral region 8 - 15 μm. The preliminary IR characterization revealed that the test microbolometer exhibits responsivity (R_v) and detectivity (D*) approximately as 36 V/W and 6 x 10⁵ cm²Hz^1/2/W at chopper frequency of 10 Hz for 50 μA bias current. Provided with the air-gap thermal isolation structure, the microbolometer will exhibit responsivity (R_v) over 1.2 x 10⁴ V/W, which compares well with the reported values.

Incorporation of sensors into structures and machines provide valuable information about their performance and reliability in real time. Fiber Optic Polarimetric Sensor (FOPS) for the smart structure applications is designed, developed and applied to different applications. The sensor monitors the change in the state of polarization of the light beam traversing through the fiber under various loading conditions. This paper describes the characterization, optimization and evaluation of the performance the fiber sensor. It also discusses the different applications of a prototype FOPS system that was developed.

This paper describes the configuration and system design of a single axis silicon micromachined fiber optic accelerometer for inertial navigation systems in spacecraft. The interferometric detection scheme employed to measure the acceleration and the design parameters to be optimized for achieving the required performance of the accelerometer are discussed. The open loop sensitivity of the accelerometer is in the order of milli-g with a dynamic range of ± 1.2 g.

Pressure sensors have widespread applications in medicine and automotive industry. Specific designs and mounting arrangements vary considerably, ranging from small, sensitive catheter-tip transducers used within the heart to the bigger, rugged devices needed for industrial process control. A capacitive type of pressure sensor has been made using bulk silicon micromachining. It converts the diaphragm deformation, corresponding to pressure, into a change of capacitance. The total change in capacitance is the integral of the change of capacitance of each small area on the diaphragm. The change of capacitance δC/C is measured as a function of deformation or pressure. The diaphragm deflection has been modelled using Intellisuite sofware.

Porous Silicon (PS) based sensors are amenable to Silicon IC processing technology. This ushers in the concept of integrated on-chip sensors in which the sensor and its signal conditioning can be integrated on a single chip. The dielectric constant of the porous layer changes under external stimuli like ambient humidity, pressure, etc. Thus a phase sensitive signal conditioning unit that can be integrated with the transducer on the same chip can form an integrated sensor that can detect humidity, pressure, etc. In order to develop the ASIC design for such a phase detecting signal conditioning unit and to peform CAD simulations and verify our design we have also developed a model for the PS transducer that can be used as a device library at runtime during simulation. In this paper we shall discuss the ASIC design of the signal conditioning unit required to develop an integrated humidity sensor and developing a SPICE device model library of the PS transducer for simulation and implementation of a SMART integrated Sensor.

Today, vibration sensors with low and medium sensitivities are in great demand. Their applications include robotics, navigation, machine vibration monitoring, isolation of precision equipment & activation of safety systems e.g. airbags in automobiles. Vibration sensors have been developed at SSPL, using silicon micromachining to sense vibrations in a system in the 30 - 200 Hz frequency band. The sensing element in the silicon vibration sensor is a seismic mass suspended by thin silicon hinges mounted on a metallized glass plate forming a parallel plate capacitor. The movement of the seismic mass along the vertical axis is monitored to sense vibrations. This is obtained by measuring the change in capacitance. The movable plate of the parallel plate capacitor is formed by a block connected to a surrounding frame by four cantilever beams located on sides or corners of the seismic mass. This element is fabricated by silicon micromachining. Several sensors in the chip sizes 1.6 cm x 1.6 cm, 1 cm x 1 cm and 0.7 cm x 0.7 cm have been fabricated. Work done on these sensors, techniques used in processing and silicon to glass bonding are presented in the paper. Performance evaluation of these sensors is also discussed.

Capacitive type vapour sensor based on porous silicon (PS) transducer has been presented. Sensing mechanism of ambient vapour concentration by PS has been modeled with an effective medium approximation (EMA) considering adsorption-diffusion-condensation kinetics of vapour molecules inside the porous bulk. Optimized pore size and pore morphology for sensing of different vapours having widely different molecular weight and volume selectively have also been studied.

One of the major programs being undertaken in our unit is, development of actuator materials and conversion of these materials into multilayer actuator devices. In order to achieve this objective, development of piezoelectric and electrostrictive materials are also being attempted. A simple and novel chemical precipitation route has been adopted for the synthesis of nano-actuator materials. Lead Zirconate Titanate (PZT) powder, free of agglomerates, phase pure, good chemical homogeneity and of 50 - 75 nm size has been synthesized. Synthesis of nano Ba(Sn,Ti)O₃ which shows linear, nearly hysteresis free strain curve is also discussed. Phase pure electrostrictive Lead Magnesium Niobate-Lead Titanate (PMN-PT) powder with a dielectric constant of 25,000 and a Tc of 38°C was prepared through double-step process. C-MET has state of the art facility for multilayer (ML) ceramic processing. These Nano-PZT powders have been converted into 50 micron green tapes through tape casting technique. Characteristics of these synthesized materials and the fabrication of ML actuators there from are presented.

Thin films of (1-x)Pb(Mg_1/3Nb_2/3)O₃-xPbTiO₃(x = 0.1 to 0.3) (PMN-PT) were successfully grown on the platinum coated silicon substrate by pulsed excimer laser ablation technique. A thin template layer of LaSr_0.5Co_0.5O₃ (LSCO) was deposited on platinum substrate prior to the deposition of PMN-PT thin films. The composition and the structure of the films were modulated via proper variation of the deposition parameter such as substrate temperature, laser fluence and thickness of the template layers. We observed the impact of the thickness of LSCO template layer on the orientation of the films. The crystallographic structure and compositional variation were confirmed with x-ray diffraction and energy diffraction x-ray (EDX) analysis. A room temperature dielectric constant varying from 2000 to 4500 was noted for different composition of the films. The dielectric properties of the films were studied over the frequency range of 100 Hz - 100 kHz over a wide range of temperatures. The films exhibited the relaxor-type behavior that was characterized by the frequency dispersion of the temperature of dielectric constant maxima (T_m) and also diffuse phase transition. This relaxor nature in PMN-PT thin films was attributed to freezing of the dipole moment, which takes place below a certain temperature. This phenomenon was found to be very similar to spin glass system, where spins are observed to freeze after certain temperature.

Polycrystalline thin films of Ba(Sn_0.1Ti_0.9)O₃ were deposited on pt coated silicon substrates by pulsed excimer laser ablation technique. The room temperature dielectric constant of the Ba(Sn_0.1Ti_0.9)O₃ films was 350 at a frequency of 100 kHz. The films showed a slightly diffused phase transition in the range of 275-340 K. The polarization hysteresis behavior confirmed the ferroelectric nature of the thin films. Remanent polarization (P_r) and saturation polarization (P_s) were 1.1. μC/cm² and 3.2μC/cm² respectively. The asymmetric capacitance-voltage curve for Ba(Sn_0.1Ti_0.9)O₃ was attributed to the difference in the nature of the electrodes. Dispersion in both the real (ε_r') and imaginary (ε_r") parts of the dielectric constant at low frequencies with increase in temperature was attributed to space charge contribution in the complex dielectric constant.

A modified-CVD method was developed to deposit thin films of oxides for device applications. ZnO thin films were deposited on various substrates after optimizing the growth parameters. The quality of the ZnO films was investigated using x-ray diffraction and scanning electron microscopy. The same ZnO film deposited on quartz substrate has been used for sensing hydrogen gas at 400°C.

Nonlinear equations of motion for elastic bending and torsion of isotropic rotor blades with surface bonded piezoceramic actuators are derived using Hamilton's principle. The equations are then solved using finite element discretization in the spatial and time domain. The effect of piezoceramic actuation is investigated for bending and torsion response of a rotating beam. It is found that the centrifugal stiffening effect reduces the tip transverse bending deflection and elastic twist as the rotation speed increases. However, the effect of rotation speed on the tip elastic twist is less pronounced. The importance of nonlinear terms for accurate prediction of torsion response is also shown.

This paper presents a vibration control methodology that is useful in practical applications where the system to be controlled is difficult to model due to the presence of uncertainties or complex boundary conditions. The impedance control method uses a power flow approach wherein the controller is designed such that power flow into the structure is minimized. This is accomplished by using the dereverberated point impedance function at the actuator location for the design of the controller. The method is implemented and simulated for a cantilever beam with piezoceramic actuators. As a preliminary step towards real-time implementation of impedance control a simple state feedback algorithm is implemented using a dSPACE digital signal processor (DSP) card.

In many applications where operations based on computing signal or image derivatives are applied, impulsive noise in the signal or image can result in serious errors. Noise elimination is a main concern in Signal and Image Processing. Wavelets introduce new classes of basis functions for Time-Frequency signal analysis and have properties particularly suited to the transient (impulse like) components. Due to its Time-Frequency localization one can detect and remove impulsive noises. The conventional linear filters, which consist of convolving the signal with a constant matrix to obtain a linear combination of neighborhood values may produce poor feature localization resulting in incomplete noise suppression. The linear filters consider any low frequency structure to be noise, but they fail to efficiently remove impulsive noises. To mitigate this problem novel non-linear filter using wavelet transform is proposed. The proposed non-linear algorithm recognizes high-amplitude, high-frequency and low-amplitude, low-frequency structures as signals. This recursive nonlinear filter is composed of conditional rules, which are applied independently, in any order. It identifies noisy items by inspection of their surrounding neighborhood, and replaces their values with most conservative ones out of their neighbors' values. The simulation was performed using MATLAB 5.1. The results are presented with various parameters like percentage of image spoiled, percentage of noise removed, Peak Signal to Noise Ratio (PSNR) in dB and execution time in sec. The performance of the proposed algorithm is compared with the conventional median filter.

In the present work a novel approach for Active Noise Control (ANC) is attempted. A structural panel used as a secondary source for active noise control in a rectangular duct is developed and tested. The structural panel is a square Aluminum trim panel, which is fixed on a steel frame vertically and excited by an electrodynamic exciter. The structural panel has many merits as an acoustic source over traditional loud speakers: it is simple in geometry, lower mass, easy in construction and requires only a simple modification of materials already installed on the duct. The vibration response and acoustic radiation response of the structural panel are studied for a simply supported boundary condition, when panel is subjected to less than 350 Hz harmonic excitation. Real time active noise control experiments are performed in a laboratory using the active structural panel as secondary source. Local attenuation of sound pressure levels of upto 45 dB is realized, in a particular location of the duct when its enclosure was excited by 210 Hz pure tone of harmonic sound.

Instrumentation, electronics, digital signal processing and related software form the basic building blocks of a system for implementation of Active Vibration Control (AVC) for smart aerospace structures. This paper essentially deals with the design, development and implementation of a 4 channel analog input sub-system essentially consisting of charge amplifiers, filters, gain amplifiers & Analog to Digital Converters (ADC), the subsequent Digital Signal Processor (DSP) hardware for implementation of the controller and finally a 4 Channel analog output subsystem consisting of Digital to Analog Converters (DAC), reconstruction filters & high voltage amplifiers. This system essentially interfaces to a structure with piezo-ceramic sensors and actuators for implementation of real time AVC on a smart beam. The paper also highlights some of the new ideas that have been incorporated into the system design.

The present work presents a fuzzy logic based controller with a compact rule base, for active vibration control of beams. The controller was implemented experimentally on a test beam and the results were found satisfactory. The test system consists of a cantilevered beam with two piezoelectric patches mounted near its root in collocated fashion. This piezo-beam system was modelled using Finite Element Method. To derive the equations of motion, Hamilton's principle was used. Electro-mechanical interaction of the piezoelectric patch with the beam was modelled using linear constitutive equations for piezoceramics, which relate strain and electric displacement to stress and electric field. The fuzzy logic controller is based on modal velocity of the beam. The basis for generating the fuzzy logic rule base of this controller is obtained from negative velocity feedback control. Modal velocity of the beam acts as an input to the fuzzy controller and actuation force is the output from the inference engine. Linear decay of vibratory amplitude is observed in case of fuzzy logic controller as opposed to logarithmic decay in case of negative velocity feedback control Present controller has just three rules. This is an important achievement because bulky fuzzy logic controllers for active vibration control require fast processors for real time implementation (Kwak and Sciulli and Mayhan and Washington).

It is becoming increasingly important to add damping to structures for vibration and noise control purposes. Most damping falls in two categories: passive damping and active damping. Recently, a new subset of damping was created by combining passive and active damping, thereby producing a hybrid damping treatment. This paper is a review of these damping treatments including the recent advances in the hybrid damping using active constrained layer damping (ACLD) treatment.

Piezoceramics are potential sensors and actuators for a wide range of applications in smart structures and systems, including shape control of radar and satellite antennas, mirrors and MEMS actuators. Piezoceramic materials are ferroelectric, and they fundamentally exhibit hysteresis characteristics when displacement is plotted against an applied electric field. The maximum error due to hysteresis is found to be as much as 10 - 15% of the path covered if the actuators are run in an open-loop fashion. These errors affect the performance of the systems in which they are used as actuators. For example, when piezoceramic actuators are bonded with flexible structures for structural shape control purposes, errors of such magnitudes are not desirable. Thus, the nonlinear hysteretic input-output behavior leads to performance degradation of the system in the applications mentioned above. Hence, this work considers modeling of the hysteresis of a piezoceramic-actuated system with a view to develop model-based control algorithms to improve the performance of systems using these elements. Piezoceramic hysteresis has only recently been modeled effectively using the Preisach mathematical model. The system for which hystersis is modelled is a cantilever beam on which two piezoceramic actuators are bonded and the beam's tip displacement is used as the output parameter. The end purpose is shape control where input variations are quasi-static, hence only the static case of input variation is considered. The predicted results using the model obtained for this system, in general, are in agreement with the experimentally measured values. This work would pave the way for use of the model for active vibration control purposes, where the input variation is dynamic, using a variant of the Preisach model for the case of dynamic input variation.

In the present paper, the active-passive hybrid vibration control performance due to Enhanced Smart Constrained Layer Damping (ESCLD) treatment as proposed by Liao and Wang on plate like structures has been considered. This treatment consists of a viscoelastic layer constrained between a smart piezoelectric layer and the base structure being controlled. Also, the smart constraining layer is clamped to the base structure. This type of damping treatment has got both active and passive component of damping. The passive damping is through cyclic shearing of viscoelastic constrained layer which is further enhanced by activating the smart piezoelectric constraining layer and the active component of the damping is through the transfer of control moments from the piezoelectric layer to the base structure through the viscoelastic layer and also bypassed through the clamps. A plate finite element has been formulated using first order shear deformation theory, including the effect of transverse shear and rotary inertia. The effect of the viscoelastic shear layer and piezoelectric constraining layer on the mass and stiffness has been included in the model. The viscoelastic shear layer is modeled usig Golla-Hughes-McTavish (GHM) method, which is a time domain approach. The clamps (edge elements) are modeled as equivalent springs connecting the smart piezoelectric constraining layer with the structure to be controlled. LQR optimal control strategy is used to obtain optimal control gains. The effect of the viscoelastic material properties (shear modulus and loss factor) on the hybrid vibration control performance is studied for both SCLD (without edge elements) and ESCLD systems.

This paper deals with experimental work concerning active vibration control of structures. Experiment is conducted considering a cantilever beam undergoing transverse motion. Piezoelectric patches are used for sensing the response and actuating the system.

Traditional approach to vibration control uses passive techniques, which are relatively large, costly and ineffective at low frequencies. Active Vibration Control (AVC) is used to overcome these problems & in AVC additional sources (secondary) are used to cancel vibration from primary source based on the principle of superposition theorem Since the characteristics of the vibration source and environment are time varying, the AVC system must be adaptive. Adaptive systems have the ability to track time varying disturbances and provide optimal control over a much broader range of conditions than conventional fixed control systems. In multi channel AVC vibration fields in large dimensions are controlled & is more complicated. Therefore to actively control low frequency vibrations on large structures, multi channel AVC requires a control system that uses multiple secondary sources to control the vibration field simultaneously at multiple error sensor locations. The error criterion that can be directly measured is the sum of squares of outputs of number of sensors. The adaptive algorithm is designed to minimize this & the algorithm implemented is the "Multiple error LMS algorithm." The best known applications of multiple channel FXLMS algorithm is in real time AVC and system identification. More wider applications are in the control of propeller induced noise in flight cabin interiors. In the present paper the results of simulation studies carried out in MATLAB as well as on TMS320C32 DSP processor will be brought out for a two-channel case.

In this paper an effort has been made to model and damp a rotating flexible beam with a rotary joint. In this work bending of flexible beam is considered using Euler-Bernoulli beam theory. To model a flexible beam, which is esentially a continuous system, it is discretized by using finite element method. After finding the expression for displacement at any point using finite element method, the dynamic equations of motion are derived using Lagrangian formulation. Time response results are obtained for undamped and viscous damped systems. Finally flexible beam is modelled as a typical laminated composite beam made up of number of layers of passive damping coating and a magnetostrictive material. A combined passive and active damping strategy in hybrid mode using combination of layers of ferromagnetic (passive) and smart (active) magnetorestrictive (Terfenol-D) materials is proposed.

Active continua with integrated sensor and actuator have proved effective in damping the vibrations of any dynamic system. This work deals with experimentally implementing control algorithms, namely negative velocity and Lyapunov control to actively damp the vibrations of a cantilever beam. A Finite element scheme is used to predict the dynamic response of the beam to transient electrical signals and to compare them with the experimentally obtained results. A distributed PVDF Polyvinylidene fluoride) actuator is used for actuation and an accelerometer is used as a tip velocity sensor.

The present study deals with the application of two different control Strategies viz. Direct Velocity Feedback (DVF) and Modified Independent Modal Space Control (MIMSC) to control the flexural vibrations of a cantilever beam mounted with piezoelectric patches. These two control strategies belong to two different categories viz. coupled control (DVF) and modal control (MIMSC). In case of DVF, the collocated system is inherently stable with respect to sensor/actuator (S/A) locations. For non-collocated system configuration, DVF is not considered to be suitable as stability of the system depends on S/A locations. With the help of root locus, it is shown that it is possible to achieve the stability of different modes provided the S/A locations are chosen properly. Also a comparison of DVF and MIMSC is carried out on the basis of two different criteria.

We present some discrete-time perspectives on the active vibration control of a simple acausal system subjected to deterministic but broadband excitation. Here, exact vibration cancellation is not possible with bounded control forces. However, on penalizing high control forces using a weighting factor, we obtain a one parameter family of finite-time optimal feedforward (FTOF) controllers that substantially reduce vibration levels through bounded control forces. These controllers require knowledge of the future of the forcing, and are thus acausal. However, only a finite amount of the future needs to be known for practical purposes. These future values are predicted using a neural network. The FTOF controllers perform better than a direct application of the standard LMS algorithm. An LMS algorithm which uses several future values of the forcing performs better still. Some recommendations are made for practical applications.

Sandwich composites find increasing use as flexural load bearing lightweight sub-elements in air/space vehicles, rail/ground transportation, marine and sporting goods. The core in these applications is usually balsa wood, foam or honeycomb with laminated carbon or glass facesheets. A limitation of traditional sandwich onfigurations is that the space in the core becomes inaccessible once the facesheets are bonded in place. Significant multi-functional benefits can be obtained by making either the facesheets or the core, space accessible. Multi-functionality is generally referred to as value added to the structure that enhances functions beyond traditional load bearing. Such functions may include sound/vibration damping, ability to route wires or embed sensors. The present work reviews recent work done in enhancing the functionality of the core by use of the space in the core. The damage created by impact to sandwich constructions is always a limiting issue in design. In the present work, low velocity impact (LVI) response of newer/multi-functional sandwich constructions has been studied. Concepts of increasing sandwich core functionality have been reported.

This paper explores concepts for new smart materials that have extraordinary properties based on nanotechnology. Carbon and boron nitride nanotubes in theory can be used to manufacture fibers that have piezoelectric, pyroelectric, piezoresistive, and electrochemical field properties. Smart nanocomposites designed using these fibers will sense and respond to elastic, thermal, and chemical fields in a positive human-like way to improve the performance of structures, devices, and possibly humans. Remarkable strength, morphing, cooling, energy harvesting, strain and temperature sensing, chemical sensing and filtering, and high natural frequencies and damping will be the properties of these new materials. Synthesis of these unique atomically precise nanotubes, fibers, and nanocomposites is at present challenging and expensive, however, there is the possibility that we can synthesize the strongest and lightest actuators and most efficient sensors man has ever made. A particular advantage of nanotube transducers is their very high load bearing capability. Carbon nanotube electrochemical actuators have a predicted energy density at low frequencies that is thirty times greater than typical piezoceramic materials while boron nitride nanotubes are insulators and can operate at high temperatures, but they have a predicted piezoelectric induced stress constant that is about twenty times smaller than piezoceramic materials. Carbon nanotube fibers and composites exhibit a change in electrical conductivity due to strain that can be used for sensing. Some concepts for nanocomposite material sensors are presented and initial efforts to fabricate carbon nanocomposite load sensors are discussed.

We have used a modal control approach to suppress the vibration amplitude of a laminated composite plate. The monolithic piezo crystals are employed as distributed actuators, sensors and are surface bonded at 0°, 45° positions on the plate. Optimal control gain estimated off-line is converted as feedback voltage and is implemented in an analog control system. The piezo actuators placed at 45° position are found efficient in controlling the torsion mode, however 0° crystals are observed effective in bending modes control. The displacement and velocity of the system are used in the closed loop feedback control as actuation signals. The displacement control is observed to be comparatively better in controlling all the three elastic modes than velocity control.

The concept of using the actuators and sensors to form a self controlling and self monitoring smart system in advanced structural design has drawn considerable interest among the research community. The smart system has large number of active, light weight, distributed sensors and actuators either bonded or embedded in the structure for the purpose of vibration suppression, shape and acoustic controls as well as fault detection and mitigation. The present study addresses the issues related to the active vibration control schemes for the smart composite panels, with substrate as the fiber reinforced composite laminate and the piezo ceramic layers as the actuators and sensors, using LQR algorithm. The study involves the structural modelling, controller design, open and closed loop system response analysis. For this purpose, an eight noded isoparametric finite element with seven degrees of freedom, viz., three translations, two section rotations and two potential differences corresponding to the actuators and sensors is developed. The piezo-ceramic actuator and sensor layers are also considered as the load bearing components in the panel. The finite element equations are first transformed into the modal state space form and then are used to obtain the constant controller gains. These are used to obtain the closed loop responses.

A finite element formulation based on higher-order shear deformation theory is presented for modeling the behavior of laminated composite plates with piezoelectric elements under static and dynamic loadings. This model is valid for both continuous and segmented piezoelectric elements that are either surface-bonded or embedded in the laminated plate. Voltage is not introduced as an additional degree of freedom in the present model and the piezoelectric elements on the upper and lower surfaces of the plate are used as actuators. The effect of actuator voltage on the static and dynamic behavior of such plates having different edge conditions and width-to-thickness ratio has been studied.

The optimal utilization of smart sensors and actuators in complex aerospace structure largely depends on the position of the actuators and sensors. Since piezo-ceramic material for active component have inferior specific strength compared to host structure, it is desirable to use patches of active materials instead of distributed actuation throughout the structure. In the present paper, the cost function for selecting the best actuator and sensor positions are found from the orthogonal projection of structural modes into the intersection subspace of the controllable and observable subspaces corresponding to any actuator and sensor locations. The cost function depends on the observability and controllability grammians. The observability and controllability grammians are found for the reduced order state space model (total number of states = 2n = 6). The '2n' state space model is found after reduction of full-order finite element model (total number of nodal DOFs = N = 140) through modal truncation. The optimal positions of actuator and sensor are found in two stages. First few actuator and sensor positions (8 actuator and 8 sensor positions) are selected from modal projection of three lowest transverse modes, with one actuator and one sensor at a time. After selection of the set of possible actuator and sensor positions the process of modal projection is repeated with two actuators and two sensors at a time. The first stage selection leads to ⁸C₂ x ⁸C₂ possible positions from which the best two actuator and two sensor positions are found in the next stage search process. The two stage search process helps in substantial reduction of computational time in a repetitive search in a large pool of admissible actuator-sensor locations. To ilustrate the optimal placement method, numerical simulation is performed for thin-walled composite I-beam.

This paper examines the use of continuous sensors to detect damage in composite materials. Continuous sensors contain multiple interconnected sensor nodes that can be integrated into an artificial neural system as an array of sensor nerves. The advantage of this passive health monitoring approach is that the sensor system is highly distributed and uses parallel processing allowing large structures to be monitored for damage using a small number of channels of data acquisition. In the paper, the continuous sensor system is modeled and simulated by solving the elastic response of a plate and the coupled piezoelectric constitutive equations. The model and simulation allow the sensor system to be optimized for a particular material and plate size. The simulation predicts that acoustic waves representative of damage growth can be detected anywhere in the plate using a simple artificial neural system. To improve the sensitivity of the continuous sensor, unidirectional active fiber composite sensors were built from piezoceramic ribbon preforms. Manufacturing of the active fiber composite sensors is also discussed in the paper. The continuous sensors were evaluated in a realistic test to show their ability detect acoustic emissions caused by damage to a composite material. The sensors were mounted on narrow glass fiber plates and tested to failure in a mechanical test machine. Results from the experiments are presented.

Major civil engineering structures, such as bridges constitute a significant portion of national wealth, and the cost of maintenance of these structures is very high. Structural health monitoring is a cost effective method of maintenance, and it predicts the structural integrity by early detection of degradation of health of the structure. One of the best ways of structural health monitoring is by the use of fiber optic strain sensors, which are eminently suitable for long term monitoring. However, the apparent strain due to variations in temperature at different measurement times may be very large and has to be accounted for. The apparent strain calibration curves of fiber optic strain sensors bonded to three structural materials, namely, steel, aluminum and concrete are obtained from laboratory experiments which can be used for correcting the temperature induced apparent strain from the total strain measured in the structures.

Detection of damages and progressive deterioration in structures is a critical issue. Visual inspections are tedious and unreliable. Incipient damages are often not discernible by low frequency dynamic response and other NDE techniques. Smart piezoelectric ceramic (PZT) transducers are emerging as an effective alternative in health monitoring of structures. The electro-mechanical impedance method employs the self-actuating and sensing characteristics of the PZT, without having to use actuators and sensors separately. When excited by an ac source, the PZT transducers bonded to the host structure activates the higher modes of vibration locally. Changes in the admittance response of the transducer serves as an indicator of damage around the transducer. In this paper, the effectiveness of PZT transducers for characterizing damages in concrete, in terms of the damage extent and location, is experimentally examined. The root mean square deviation (RMSD) index, adopted to quantify the changes in the admittance signatures, correlates with the damage extent. The damages on the surface that is not mounted by the PZT are also discernible. An array of transducers proves effective in detecting the damaged zone. The progressive incipient crack can be detected much before it actually becomes visible to the naked eye.

Smart Composite laminates with multiple magnetorestrictive patches have been fabricated, one patch is for actuation and the other patch is for sensing. Horse-show type coil arrangement is used for actuation and sensing, which contains two arms, one arm is used for actuation and the other arm for sensing. Delamination sensing is carried out for composite laminated beam specimens, one with delamination and the other without any defect or damage. Actuation coil is used to induce stress in the magnetostrictive material, sensing coil is used for sensing to measure the induced open circuit voltage. Due to delamination, the stress produced in the magnetostrictive patch changes and that alters the magnetic flux through the sensing coil. This causes a change in the induced open circuit voltage across the sensing coil. The paper presents, the sensing of delamination in composite laminates using multiple magnetostrictive patches with horse-shoe type coil arrangement. The difference in the open circuit voltage with and without delamination is treated as delamination sensing voltage. For theoretical modeling, different models of the laminated composite beams with magnetostrictive sensors and actuators have been developed for the beams with and without delamination. Finite element analysis is carried out using NISA finite element software. Numerical values of open circuit voltage verses actuation current for both the experimental and computational studies are presented. Comparison of experimental and the computational studies shows that there is a good agreement between both the results obtained. Hence, the modeling method is very efficient and may be very much useful for the further studies related to the smart structures with intelligent materials.

The ability of Lamb waves to travel long distances can be harnessed to monitor damage in large structures, such as those used in aerospace applications. This paper reports on studies of the propagation of Lamb waves in composite structures the signal processing techniques used to get information from Lamb wave data. The Short Time Fourier Transform (STFT) is used as a tool for signal processing on Lamb waves. The energy of the Lamb wave signal is employed to reconstruct the image using iterative tomographic algorithms.

A new finite element formulation was derived for structural health monitoring of laminated composite beam containing embedded magnetostrictive patches, which will act both as sensors and actuators. Coils are considered to activate patches and/or to sense the changes in stress in patches. When the actuator patch is excited dynamically by passing alternating current through the actuation coil, it introduces stress in the structure due to magneto-mechanical coupling effect, which in turn produce magnetic flux in the sensing patches. This magnetic flux generates open circuit voltage in the sensing coils. Measurements of open circuit voltage before and after the damage (delamination) occurrence provides a diagnostic to indicate the presence of the damage. Numerical results have been obtained for one combination of actuator and sensor locations.

This paper introduces a spectral element model-based frequency-domain method of structural damage identification. The appealing features of the present damage identification method are: (1) it requires only the frequency response functions experimentally measured from damaged structure as the input data, and (2) it can locate and quantify many local damages at the same time. The feasibility of the present damage identification method is tested through some numerically simulated damage identification analyses and then experimental verification is conducted for a cantilevered beam with damage caused by introducing three slots.

A hierarchical Genetic Algorithm (GA) is implemented in a high peformance spectral finite element software for identification of delaminations in laminated composite beams. In smart structural health monitoring, the number of delaminations (or any other modes of damage) as well as their locations and sizes are no way completely known. Only known are the healthy structural configuration (mass, stiffness and damping matrices updated from previous phases of monitoring), sensor measurements and some information about the load environment. To handle such enormous complexity, a hierarchical GA is used to represent heterogeneous population consisting of damaged structures with different number of delaminations and their evolution process to identify the correct damage configuration in the structures under monitoring. We consider this similarity with the evolution process in heterogeneous population of species in nature to develop an automated procedure to decide on what possible damaged configuration might have produced the deviation in the measured signals. Computational efficiency of the identification task is demonstrated by considering a single delamination. The behavior of fitness function in GA, which is an important factor for fast convergence, is studied for single and multiple delaminations. Several advantages of the approach in terms of computational cost is discussed. Beside tackling different other types of damage configurations, further scope of research for development of hybrid soft-computing modules are highlighted.

Over past few years, the concept of structural health monitoring has been emerging as a new area of research. Fiber Bragg grating (FBG) based sensor offers a new sensing approach with a number of advantages over conventional sensors. This new sensing technology is suitable for the harsh environment of construction industry due to its robustness, ruggedness and ease of installation. Two unique advantages of FBG based sensors are immunity to electromagnetic interference and multiplexing capability. This paper reports some of the results of a multi-disciplinary program on the FBG based sensors involving the School of Electrical and Electronic Engineering and the School of Civil and Environment Engineering at Nanyang Technological University, Singapore.

Fiber reinforced structures and machines are becoming increasingly popular in recent years, as they facilitate nondestructive damage detection in these systems. Fiber Optic Polarimetric Sensor (FOPS) is an interesting device in real time structural health monitoring. In this paper the authors present their experimental results on the health monitoring of aluminum, concrete and composite structures using FOPS. The sensor monitors the change in state of polarization of the light beam traversing in the fiber under dynamic loading. The dynamic response of high-birefringence fiber has been evaluated for the three types of structures by embedding the fiber into the specimen. The performances of FOPS is damage detection of the three smart structures under impact loading condition are compared.

In this paper we present a modified design based on thermal characterization of the membrane of microbolometer based infrared detectors. Theoretical calculations show that the thermal conductance should be of the order of 10^-5 W/K for 100 μm x 100 μm membrane size with the hinges of length 2 μm whereas our experimental results show that it is of the order of 10^-7 W/K. These results are explained on the basis of reduced value of the thermal conductivity of thin films compared to their bulk value. A model has been presented to explain the results.

MEMS device structures, particularly those made using Surface-Micromachining, consist of thin layers of insulator, silicon, silicon dioxide, silicon nitride, metal or poly-silicon held at few points onto a thick silicon substrate. These heterogeneous layers resemble closely to laminas of composites used in building structures. For these heterogeneous material systems, involving Metal-Insulator-Semiconductor layers, there is usually an inherent two dimensional thermal contraction of the various layers upon cooling from a growth temperature of 1000 to 1200 C down to room temperature. The thermal stress, so developed, could result in static deformation as well change the dynamic characteristics of the micro-parts. Thin heteroepitaxial layers, with lattice mismatch with the single crystal substrate, can also result in a built in stress. External effects like electrostatic potentials and magnetic fields applied to a layered structure can also result in contractions or extensions of specific layers that respond to applied fields. A generic formulation of governing equations of equilibrium and compatibility has been developed for laminated structures with various in-built stress effects like difference in temperature of formation and use; difference in lattice constants of heteroepitaxial layers; effects that involve dimensional changes like piezoelectric effect and magnetostriction. This paper aims at demonstrating, through simulations of a test structure of a doubly suspended resonator, how these multi-layer structures could exploit the static deformations to result in a robust (temperature-insensitive) dynamic response. The static deformation for temperature changes in a bi-layer of aluminum and silicon dioxide is simulated on ANSYS. The results of ANSYS match very well with a fabricated test device.

Integrated optics combined with micro-electro mechanical system (MEMS) technology offer enormous potential to improve sensitivity and performance capabilities of new sensors. In this paper, an analysis is carried out to find the feasibility and design concept of a Micro-Opto-Electro-Mechanical (MOEM) accelerometer consisting of integrated optic Mach-Zehnder interferometer, whose sensing arm is attached to a micromachined vibrating cantilever or a bridge. The analysis consists of determining changes in phase shift due to acceleration-induced refractive index and optical path length variation of MachZehender interferometer. A noise analysis is carried out to find the fundamental performance limit of different sensor configurations.

Transparent conducting tin-doped indium oxide (ITO) thin films were deposited on Teflon and glass substrates using RF magnetron sputtering technique from an ITO ceramic target. The substrates were loaded on a cylindrical drum maintained at a temperature of 15 ± 2°C and rotated at a constant rate of 6 rpm. At the optimal deposition condition, the ITO thin films with maximum transmission of 93% and a minimum sheet resistance of 10Ω/∠ was achieved.

The focus in MEMS technology is now slowly changing from process-centric research to design. More and more mechanical designers are entering MEMS field. However, most designers have intuitive feel for macro-scale designs, but not for micro-scale design. Intuition is an indispensable tool in design that cannot be replaced by brute force simulation. This paper is about some of the issues in mechanical design of MEMS transducer elements that are not yet a part of a designer's intuition. We discuss, through examples, why these issues belie our intuition at the micro-scale.

A MEMS based switchable CPW fed slot antenna is designed and characterized. MEMS shunt switch designed for switching the slot antenna has been simulated using HP EEsof. The return loss has been obtained.

Recent developments in Micro Electro Mechanical Systems (MEMS), promises to solve several technological limitations that have plagued the wireless electronics for decades. This paper reports the applicability of MEMS technology in the implementation of RF switches for the realization of switchable low pass filter. The switch and filter are designed and simulated for 2 GHz, 3 GHZ using HPEEsof simulator.

This paper presents and applies the concept of micro-boundary conditioning to the design synthesis of microsystems in order to quantify the influence of inherent limitations of the fabrication process and the operating conditions on both static and dynamic behavior of microsystems. The predicted results on the static and dynamic behavior of a capacitive MEMS device, fabricated through MUMPs process, under the influence of the fabrication limitation and operating environment are presented along with the test results. The comparison between the predicted and experimental results shows a good agreement.

We describe a planar MEMS silicon structure to record ion-channel currents in biological cells. The conventional method of performing an electrophysiological experiment, 'patch-clamping,' employs a glass micropipette. Despite careful treatments of the micropipette tip, such as fire polishing and surface coating, the latter is a source of thermal noise because of its inherent, tapered, conical structure, which gives rise to a large pipette resistance. This pipette resistance, when coupled with the self-capacitance of the biological cell, limits the available bandwidth and processing of fast transient, ion channel current pulses. In this work, we reduce considerably the pipette resistance with a planar micropipette on a silicon chip to permit the resolution of sub-millisecond, ion-channel pulses. We discuss the design topology of the device, describe the fabrication sequence, and highlight important critical issues. The design of an integrated on-chip CMOS instrumentation amplifier is described, which has a low-noise front-end, input-offset cancellation, correlated double sampling (CDS), and an ultra-high gain in the order of 10¹²V/A.

With the established technique of LIGA process, fabrication of three dimensional structure in micron and submicron order has become feasible. High aspect ratio microstructure technology (HARMST) have been studied uisng synchrotron radiation microlithography and etching (SMILE). Plane-pattern to cross-section transfer (PCT) technique, has been applied for forming of three-dimensional microstructures with novel shapes using deep X-ray lithography. On the other hand, a new approach of three-dimensional (3-D) micromachining without using any masks is proposed. This approach is a direct writing using synchrotron radiation (SR) etching. A few results of 3-D micromachining of PTFE using SR etching in vacuum and under an atmospheric pressure of He are also demonstrated.

In this paper, we outline the process leading from technologies to successful products in the MEMS (Microelectromechanical Systems) and MST (Microsystems Technology) field. The development of new products involves a lot of factors, such as mature technologies, interdisciplinary team, identifying the right business potential and long term oriented investors. The paper summarizes a survey of different technologies and point out that packaging, test and calibration are still major shortcomings for the concerned industries.

In this paper, it is shown that Silicon-On-Insulator (SOI) wafers with good surface finish and thickness control can be realized using Silicon Fusion Bonding along with an optimized ethylenediamine-pyrocatechol-water (EDP) etching approach. Single crystal diaphragms of 11 μm thickness have been fabricated using these SOI wafers. These diaphragms were tested and found to withstand N₂ gas pressures in excess of 260 psi without rupturing.

Similar to silicon integrated circuits, the reliability improvement in MEMS devices starts with the very design and is a process involving all stages of manufacture and test. This process of building-in reliability is the resultant of various physical analyses to understand the failure mechanisms and to provide feedback to each stage for appropriate corrective actions. But, due to the structural uniqueness, the analysis of MEMS devices faces many challenges. Eventhough, a number of tools used for ICFA are being used for MEMS failure analysis, the methodology and application differs. An overview of the analysis issues for building-in reliability in MEMS devices is discussed.

In this paper, the design and fabrication of polysilicon piezoresistive pressure sensor are presented. The design considerations such as the membrane thickness and the arrangement pattern of polysilicon piezo-resistors on the membrane are discussed with emphasis on the use of SOI approach. The results obtained on the pressure sensors and the temperature coefficient of resistivity of polysilicon resistors are presented. The results presented include the electrical trimming of polysilicon resistors for compensating zero offset voltage in the pressure sensors.

The roles of microfabricated components for miniaturized chemical analysis systems are reviewed and the fundamental advantages of these components are illustrated in typical analysis and separation systems, including mass spectrometry, electroanalytical chemistry, capillary electrophoresis, and chromatography. In each instance the scaling laws that affect the resolution of the miniaturized instrument are supported by key enabling micromachined components. Micromachined components are also enabling elements for system integration and for coupling multiple techniques together in parallel or cascade.

Developmental work in the fabrication of microsystems with integrated optics and fluidics is described. For application such as blood flow and blood cell deformability studies, microparticle identification and manipulation, and on-chip chemical analysis, microchannels and waveguides with inner dimensions in the range of 30 - 50 μm are required. Two integration strategies are described: laser-writing of channels and waveguides in UV-curable polymers and fabrication of silver ion-exchange waveguides in glass microchannel biochips. A fiber-fed photomultiple detection system is also discussed.

Shape memory alloys (SMAs) are a promising class of advanced materials with interesting properties, which make them suitable for a variety of engineering applications. The uses of SMAs in engineering applications have extended year by year. SMAs are being used in a number of industrial applications such as aerospace, automotive, biomaterial, chemical-sensor, construction, electronics, metal forming, storage and retrieval of information, optics etc. This paper highlights some of these engineering applications of SMAs. This also includes the recent research on the possible use of SMAs in smart structures. The important properties of SMAs that provide the impetus for using these materials in innovative applications are (1) shape memory effect, (2) pseudoelasticity and (3) high damping capacity. For a better appreciation, some of the basic principles and properties related to the unique behavior of this class of materials are also discussed.

Electrical resistivity and Strain recovery measurements have been used for the study of the stability of R-phase in NiTi shape memory alloy upon thermal cycling under a constant tensile stress of 100 MPa. Two samples are chosen for the study of which one sample heat-treated at 560°C exhibits a pure martensitic phase at ambient temperature and the other heat-treated at 380°C consists of a mixture of R-phase and martensitic phase at ambient temperature. In the case of the sample heat-treated at 380°C, under the applied stress of 100 MPa, heating part of the cycle also shows the presence of R-phase unlike the case of stress free condition where only cooling part exhibits the R-phase. For the sample heat-treated at 560°C, the thermal cycling under tensile stress of 100 MPa initiates R-phase in the first cycle itself whereas under stress free condition it requires about 15 cycles to initiate R-phase. The sample heat-treated at 560°C exhibits more recoverable strain in the initial cycles than that of the sample heat-treated at 380°C, but after large number of thermal cycles of the order of 1000 the recoverable strain in both samples is found to be almost the same. The sample heat-treated at 380°C is found to be more stable against plastic deformation with thermal cycling and hence can be preferred over the sample heat-treated at 560°C for the two-way applications of SMA.

Copper-based shape memory alloys (SMAs) are prone for grain growth during thermomechanical and betatising treatments. The grain growth of the alloy leads to intergranular cracking on quenching to form martensite in the alloy, which in turn leads to poor mechanical properties including corrosion resistance of the alloy. In the present work, grain refinement of a CuZnAl shape memory alloy was done by adding 0.2 to 0.4 wt% of zirconium, titanium and boron as grain refiners. The effect of these additions on the microstructure and shape memory properties of the alloys were studied. The results show that the Zr and Ti additions reduce the grain size from 1.5 mm to 200 μm and 500 μm, repectively. The Zr-added alloy shows good strain recovery and corrosion resistance compared with the alloy in the other conditions.

While the experimental use of shape memory alloys (SMAs) is widespread in aerospace integrated actuation systems, much of the practical value of SMA technology is realized in linear and rotary actuators. This report will introduce an attempt to develop a full-scaled SMA based actuator to replace electro-mechanical actuator for flap actuation of a Remotely Piloted Vehicle (RPV). At the heart of this actuator there is thermally sensitive wire that, when heated, contracts and provides useable mechanical energy. This linear actuation is converted into rotary, for the required actuation of flap. The actuator configurations were sized to fit inside the wing of the RPV where presently the electro-mechanical actuator is housed. The torque supplied to the flap is similarly calculated from full-scale requirements. Using common engineering principles, this design will demonstrate how to design a typical SMA actuator. Test of the actuator performance (stroke, force movement) is done on special test fixture.

Shape memory alloy (SMA) is being widely used to implement smart concepts such as shape control and vibration suppression of aerospace structures. Shape memory alloy wires while undergoing phase transformation from martensite state to austenite state produce large strains. While doing so they serve as actuators and generate large forces when constrained while recovering their pre-defined shape, imparting this force to the structural component on which they are mounted which results in its movement. While designing the electronic system to energise an aerospace structure with shape memory alloy based actuators the amount of current and time for which this current is passed through the shape memory alloy wire are important considerations. It is equally important to design very efficient and miniature power sources (constant voltage as well as constant current) and control system to achieve fine and steady positioning of the structural component. This paper discusses different issues involved, as well as design and development of the electronics and control system for actuating and controlling a typical aerospace structural component with SMA actuators.

This paper present a thermo-mechanical one dimensional constitutive model based on the use of strain and temperature as control variables and able to reproduce the basic responses of shape memory material such as super elasticity, shape memory behavior, pseudoelasticity, single variant martensite reorientation process. The model time integration is performed and a robust algorithm for solution of the time discrete model is addressed together with algorithmically consistent tangent. The model is implemented in NITINOL wire (Ni-Ti-6% Cu) which is used to simulate the above mentioned responses. The Thermomechanical response at different temperatures compare well with experimental and numerical results.

The Brinson-Lammering constitutive model is modified to account for the nonlinear shape memory alloy behavior. The model is divided into three modules by keeping each of the three parameters of stress, strain and temperature constant. Experiments were conducted with a NiTiCu material to obtain the model constants. The constants were then incorporated in the model and the behavior predicted. A good correlation is obtained between the theory and experiments.

In this paper; first a comprehensive understanding of temperature and stress induced phase transformation is presented and a thorough interpretation of martensitic phase transformation is presented. A numerical study of Brinson's model is then presented, in order to explain the capability of the model in reproducing the SMA characteristics under quasi-static thermomechanical loading. A MATLAB code was developed for the Numerical Simulation of Brinson's Constitutive Model. The stress strain curves obtained by the Brinson's model were used to simulate the behavior of SMA wires and Beams under Quasi-static thermo-mechanical loading. Later in the end the applicability of Brinson's model for Hysteresis effects was studied by subjecting the beam model to two cycles of loading and unloading and then the Shape Memory Effect was studied. It was observed that the Brinson's Model needs some modifications for expressing Hysteresis Effects. However for one cycle of loading and unloading, the model well predicted the Super Elasticity and Shape Memory Effects.

An all composite bridge with integral sensor network has been designed and built at the University of Missouri-Rolla (UMR). An extensive experimental study and finite element analysis were carried out to obtain and compare properties (stiffness, strength, failure modes) of 76 mm (3 in) square hollow pultruded Fiber Reinforced Polymer (FRP) tubes and their assemblies. Tube assemblies were used in the fabrication of bridge deck designed for H-20 truckloads as specified by the American Association of State Highway and Transportation Officials (AASHTO). The bridge is 9.14 m (30 ft) long and is 2.74 m (9 ft) wide. All the coupons were tested under three- or four-point bending. Experimental results show excellent linear elastic behavior up to failure and are in good agreement with finite element solutions. A quarter portion of the full-sized bridge deck was then tested for its structural performance under design and fatigue loading and also for ultimate load capacity to evaluate the bridge response. The characteristics of the full-size bridge deck were determined by analyzing the performed tests. The test sample showed almost no reduction in stiffness or strength after 2 million cycles of fatigue loading in excess of the design load. The bridge was installed at the UMR campus in July 2000. The bridge is equipped with fiber optic sensors, and the response of the bridge will be remotely monitored.