Photoelastic analysis of stress frozen slices using five-step method
04 Dec 2009-Vol. 7522, pp 752209
TL;DR: In this paper, stress frozen 3D models are sliced mechanically and the whole field principal stress differences (Isochromatics) and principal stress directions (Isoclinics) are evaluated by capturing only five images using the standard optical arrangements of a conventional polariscope.
Abstract: Digital photoelasticity is a whole field experimental technique which can analyze both 2-D and 3-D models. In this paper, stress frozen 3-D models are sliced mechanically and the whole field principal stress differences (Isochromatics) and principal stress directions (Isoclinics) are evaluated by capturing only five images using the standard optical arrangements of a conventional polariscope. The wrapped isoclinic values obtained by processing the first four colour polarization stepped images in the range -π/4 to +π/4 are unwrapped using adaptive quality guided phase unwrapping algorithm to get isoclinics in the range of -π/2 to +π/2. The total fringe order is evaluated by three fringe photoelasticity or RGB photoelasticity with its latest developments like colour adaptation combined with refined three fringe photoelasticity. The methodology is validated for two slices cut from aero-structural components.
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TL;DR: This review thematically classifies all the developments in digital photoelasticity and highlights the relative merits and drawbacks of the various techniques to allow an end-user to make an informed choice on the type of technique to be used in a particular situation.
Abstract: Digital photoelasticity has rapidly progressed in the last few years and has matured into an industry-friendly technique. This review thematically classifies all the developments in digital photoelasticity and highlights the relative merits and drawbacks of the various techniques. The overall objective is to provide enough information and guidance to allow an end-user to make an informed choice on the type of technique to be used in a particular situation.
78 citations
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TL;DR: In this paper, a ramped phase map for the isochromatic parameter is produced in the range -?
Abstract: The new approach to phase-stepping photoelasticity known as ‘‘load stepping’’ is used to determine automatically the isochromatic parameter a and the isoclinic angle ?. There is no need for the user to calibrate the results other than to convert the isochromatic parameter into a principal stress difference using the material fringe constant. Four phase-stepped images are collected using a circular polariscope for each of three load steps, which differ by small equal increments. A ramped phase map for the isochromatic parameter is produced in the range -?
32 citations
TL;DR: In this paper, a comparative study has been conducted on the performance of these methods both qualitatively and quantitatively, and theoretically simulated and experimentally recorded images for a ring under diametral compression is used.
Abstract: With the advent of PC-based digital image processing systems, automation of parameter estimation based on intensity processing from the entire field has now become simpler. Various methods for obtaining the isoclinic parameter using plane, circular, and mixed polariscopes have been reported in the literature. A comparative study has been conducted on the performance of these methods both qualitatively and quantitatively. The focus of the study is on how these algorithms provide the basic isoclinic data. To illustrate the performance, theoretically simulated and experimentally recorded images for a ring under diametral compression is used. The role of background light intensity and quarter-wave plate mismatch on the experimental evaluation of isoclinic data is brought out.
25 citations
"Photoelastic analysis of stress fro..." refers background in this paper
...2 2 2 2 2 ( ) ( ) ( ) ( ) e c e c e c p e R R G G B B N N K = − + − + − + − × (3) where Np is the fringe order obtained for the neighbourhood pixel to the point under consideration in the generic specimen and N is the fringe order at the current checking point of the calibration table....
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...(3) and the magnitude of K has to be selected iteratively....
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TL;DR: In this paper, a new method is developed, which uses a dark field image for ambiguous zone identification and its correction, and the performance of the new methodology is demonstrated by using the problem of a ring under diametral compression and a slice cut from a stress frozen model.
Abstract: Phasemaps obtained by phase shifting techniques in digital photoelasticity contain ambiguous zones. To obtain total fringe order by phase unwrapping, the phasemap should be free of ambiguous zones. A new method is developed, which uses a dark field image for ambiguous zone identification and its correction. This methodology is explained and validated by solving a benchmark problem. As ambiguous zones are of arbitrary shape, an advanced boundary extraction method developed in-house is used for effecting the correction in practical problems. The performance of the new methodology is demonstrated by using the problem of a ring under diametral compression and a slice cut from a stress frozen model.
17 citations
15 citations
TL;DR: Using a monochromatic light source for illumination, a new approach which uses two different loads to get continuous isoclinic fringes is proposed in this article, and a new set of optical arrangements in a plane polariscope setup is proposed for this purpose.
Abstract: Using a monochromatic light source for illumination, a new approach is proposed which uses two different loads to get continuous isoclinic fringes A new set of optical arrangements in a plane polariscope setup is proposed for this purpose The intensity equations are obtained by Jones calculus The methodology is verified for the problem of a disc under diametral compression
14 citations