KEYWORDS: Digital image correlation, Aluminum, Thermal modeling, 3D metrology, High power lasers, Numerical simulations, Cameras, Statistical modeling, Finite element methods, 3D image processing
The paper presents the new approach to the analysis of interaction between a high power laser beam and matter. The method relies on the combined experimental-numerical spatio-temporal analysis of temperature, displacement and strain maps which are generated at a surface of an object illuminated by a high power laser beam. Transient heat transfer numerical simulations were carried out applying the FVM, while the quasi-transient structural analyses were performed with the aid of the FEM. The displacement maps were captured by means of 3D Digital Image Correlation method, and temperature maps were provided by a high speed IR camera. The experimental data are compared to the initial model of laser induced heat transfer in an object and resulting displacements/strains. The first approach to hybrid experimental-numerical method which aims in indirect determination of laser beam profile is described. The monitoring of displacement/strain maps directly at an illuminated object may be also used for a structural integrity analysis of a target. In the paper at first the numerical simulations applied to model laser beam thermal interaction with solid bodies are presented. Next the laboratory experimental stand is described and the results of the initial tests performed at aluminum and bronze samples are shown and compared with numerical simulations. The advantages and disadvantages of the proposed methodology are discussed in relation to the two applications mentioned above.
Many building structures due to complex geometry and nonlinear material properties are difficult to be analyzed with FEM methods. A good example is a self-supporting metal plates structure. Considering uncommon geometry and material characteristic of a metal plate (due to plastic deformations, cross section of a trough, a goffer pattern), the local loss of stability can occur in unexpected regions. Therefore, the hybrid experimental-numerical methodology of analysis and optimization of metal plates structures has been developed. The methodology is based on three steps of development and validation of a numerical model with utilization of Digital Image Correlation measurements. In each step, the measurements are performed in different environments, with different accuracies and different scales. In this paper, the results of analysis performed with Digital Image Correlation, that enabled development and validation of FEM model are presented. The performed modification of a measurement setup is also described.
KEYWORDS: Digital image correlation, 3D metrology, Temperature metrology, 3D modeling, Annealing, 3D image processing, Metals, Cameras, Imaging systems, Calibration
Recently the demand and number of applications of full-field, optical measurement methods based on noncoherent light
sources increased significantly. They include traditional image processing, thermovision, digital image correlation (DIC)
and structured light methods. However, there are still numerous challenges connected with implementation of these
methods to in-situ, long-term monitoring in industrial, civil engineering and cultural heritage applications, multimodal
measurements of a variety of object features or simply adopting instruments to work in hard environmental conditions.
In this paper we focus on 3D DIC method and present its enhancements concerning software modifications (new
visualization methods and a method for automatic merging of data distributed in time) and hardware improvements. The
modified 3D DIC system combined with infrared camera system is applied in many interesting cases: measurements of
boiler drum during annealing and of pipelines in heat power stations and monitoring of different building steel struts at
construction site and validation of numerical models of large building structures constructed of graded metal plate
arches.
KEYWORDS: Digital image correlation, 3D metrology, Temperature metrology, 3D image processing, Diagnostics, Cameras, Thermal engineering, Infrared cameras, Standards development, Imaging systems
In the paper we present implementation of 3D DIC method for in-situ diagnostic measurements of expansion
bellows in heating chambers. The simultaneous measurements of a supply and a return pipeline were carried out
in a heating chamber in Warsaw at the peak of the heating season in cooperation with Dalkia Warszawa. Results
of the measurements enabled assessment of the risk of failure of expansion bellows. In-situ measurements were
preceded by feasibility tests carried out in the Institute of Heat Engineering of Warsaw University of Technology.
Potential implementations and a direction of future works are discussed in conclusions.
KEYWORDS: Digital image correlation, 3D metrology, Sensors, Finite element methods, 3D modeling, Data modeling, Metals, Structural engineering, Cameras, Cultural heritage
Optics as the enabling technology is applied in many applications of engineering, medicine, multimedia and conservation
of cultural heritage. Most of these applications require close cooperation with the end user and often they enforce
modification and enhancement of an optical tool. In the paper we show how optical metrology, specifically the
application of digital image correlation method is implemented to two completely different tasks: performing preoperating
tests of low cost building structures subjected to loading conditions which simulate the natural load e.g.
introduced by the weight of snow and monitoring of canvas paintings for tracking humidity-induced deformations,
which may appear in museum (or other location of a piece of art e.g. church).
The presented examples are the background for a general discussion on different measurement scenarios with application
of DIC method, as well as the required enhancements and modifications which have been introduced.
KEYWORDS: Digital image correlation, Humidity, 3D image processing, Climatology, Cameras, 3D modeling, 3D metrology, Climate change, 3D acquisition, Data modeling
A non-invasive and non-contact optical method for tracking overall and local deformations of canvas painting is
presented. The technique was tested on a model painting on canvas with inhomogeneities introduced by infilling gaps,
mending tears, and applying patches on the reverse of the canvas. The deformation of the sample was induced by
changes of relative humidity. The feasibility of 3D Digital Image Correlation technique for evaluation of conservation
methods is discussed.
The data from a monitored structure/object should be easy acquired, processed and sent to the user, who can assess the
health of a structure in short time and schedule necessary maintenance in order to prevent accidences. Systems which
provide such information are fundamental for Structural Health Monitoring (SHM).
In the paper novel optical sensor designed for in-plane displacement and strain monitoring in crucial points of a big
engineering and civil structures is presented. It combines two techniques: Grating Interferometry (GI) and Digital
Speckle Pattern Interferometry (DSPI).
GI requires specimen grating attached to the surface of an object under test. It is the unique technique which may provide
the information about fatigue process and increased residual stresses.
DSPI works with a rough object surface but due to differential measurements cannot be simply used for long time
monitoring but to explore the actual behavior of a structure.
The sensor which combines these techniques provides user with wide possibilities concerning functionality, measuring
range, object surface and environmental conditions.
The crucial issue in implementation of this sensor is the choice of its location(s) at the investigated structure. Therefore
it is proposed to be as one of the elements of hierarchical sensors net, which gives complete information about structure
state. As the method for supporting the choice of GI/DSPI sensor location we proposed the system based on 3D digital
correlation method.
The paper presents mechanical and optical sensor design along with laboratory tests of main component such as sensor
heads in form of monolithic (plastic) and cavity waveguides. Finally the possible application of proposed sensor in
combination with 3D DIC system is presented.
In this paper a distributed intelligent system for civil engineering structures on-line measurement, remote monitoring,
and data archiving is presented. The system consists of a set of full-field optical displacement sensors connected to
a controlling server. The server conducts measurements according to a list of scheduled tasks and stores the primary data
or initial results in a remote centralized database. The description of an exemplary set of full-field sensors including IP
and thermovision camera, 2D and 3D digital image correlation systems, and grating interferometry based extensometers
is provided. Three different measurement tasks performed by means of this systems are presented in details.
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