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Digital Photoelasticity: Advanced Techniques and Applications

K. Ramesh1, G Lewis2•
Indian Institute of Technology Kanpur1, University of Memphis2
01 Jan 2000-
TL;DR: In this article, phase shifting, Polarization Stepping and Fourier Transform Methods are used for phase unwrapping and Optically Enhanced Tiling in digital photoelasticity.
Abstract: Transmission Photoelasticity.- Reflection Photoelasticity.- Digital Image Processing.- Fringe Multiplication.- Fringe Thinning and Fringe Clustering.- Phase Shifting, Polarization Stepping and Fourier Transform Methods.- Phase Unwrapping and Optically Enhanced Tiling in Digital Photoelasticity.- Colour Image Processing Techniques.- Evaluation of Contact Stress Parameters and Fracture Parameters.- Stress Separation Techniques.- Fusion of Digital Photoelasticity, Rapid Prototyping and Rapid Tooling Technologies.- Recent Developments and Future Trends.
Citations
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Dissertation•
A Study on Experimental Determination of Mixed-Mode Sif’s Using Digital Photoelasticity and DIC

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Veerkar, Ramji M
01 Jan 2012
TL;DR: In this paper, an over-deterministic nonlinear least square approach has been used for the estimation of mixed-mode SIFs for different specimen configurations using digital photoelasticity and DIC.
Abstract: Several experimental techniques can be used for the estimation of mixed-mode SIF’s. Out of these, digital photoelasticity and digital image correlation (DIC) have evolved as the most preferred techniques for the evaluation of fracture parameters. The present study attempts to evaluate SIF’s for different specimen configurations using digital photoelasticity and DIC. For photoelastic determination of SIF’s, an over-deterministic nonlinear least square approach has been used. Isochromatic fringe order has been evaluated over the entire model domain by using ten-step method. Using the techniques of digital image processing, data required for evaluation of SIF’s has been collected in an automated manner. The methodology has been applied for the extraction of SIF’s for two different specimen configurations, single edge notched (SEN) panel and interacting parallel edge cracked panel. The experimental results have been compared with analytical and finite element (FE) estimates. For the estimation of mixed-mode SIF’s using DIC, required displacement data has been obtained using 3D-DIC. Using this data as an input, over-deterministic nonlinear least square approach has been implemented in modified form for reliable and better convergence of solution. For this purpose, MATLAB program has been written. In order to ensure the sufficiency of number of parameters, displacement field has been reconstructed theoretically to compare it with the experimentally obtained displacement distribution. The presented methodology has been used to extract mixed-mode SIF’s for various specimen configurations. The experimentally obtained results are compared with the analytical solutions available in the literature.

2 citations

Cites background or methods from "Digital Photoelasticity: Advanced T..."

  • ...[15, 35] and are summarized here for completeness....

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  • ...In phase shifting techniques, specific phase shifts are introduced between the recorded images for a given experimental situation using specific arrangement of the optical elements [35]....

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  • ...Two-dimensional stress field equations introduced by Atluri and Kobayashi, [15, 35] for the general mixed-mode case, are given below and the same have been used in the present work....

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Journal Article•DOI•
Error analysis and correction equations for a real-time phase-shifting method using circular polariscope-based photoelasticity

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Yang Gao, Xinjun Wan, Shu-Yun Xie, Jiaxing Tao
01 Jun 2022-Optik
TL;DR: In this paper , the authors proposed error correction equations for the instantaneous phase-shifting method based on theoretical analysis and simulation of a diametrically stressed disc, where the error distributions of the stress direction angle and phase retardation are discussed, and correction equations of the isochromatic and isoclinic lines are deduced.

2 citations

Journal Article•DOI•
Plotting of Isoclinic Phasemap from Finite Element Results and its Use in Digital Photoelasticity

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K. Ashokan1, K. Ramesh2•
Indian Institute of Technology Madras1, Indian Institutes of Technology2
01 Aug 2007-Applied Mechanics and Materials
TL;DR: In this paper, a method is developed to plot the simulated wrapped and unwrapped isoclinic phasemap from 2D finite element (FE) results so that one can use this as a convenient tool for identification and correction of inconsistent zones.
Abstract: Digital photoelasticity is an experimental method for determining stresses in 2D and 3D models. In digital photoelasticity one gets a wrapped isoclinic phasemap. The main issue with wrapped isoclinic phasemaps is that the isoclinic values obtained do not uniformly represent the principal stress direction of one of the principal stresses consistently over the entire domain. These zones are labelled as inconsistent zones. Such zones need to be identified and corrected to get unwrapped values of continuous isoclinic phase values. In this paper, a method is developed to plot the simulated wrapped and unwrapped isoclinic phasemap from 2D Finite Element (FE) results so that one can use this as a convenient tool for identification and correction of inconsistent zones in isoclinic phasemaps obtained experimentally for complex problems. The method is explained by using the problem of a circular disc under diametral compression. The application of this method for handling complex problems is demonstrated by solving the cantilever bending of a binocular specimen.

1 citations

Cites background or methods from "Digital Photoelasticity: Advanced T..."

  • ...Introduction Digital Photoelasticity is a whole field experimental technique, which provides the principal stress difference (isochromatic) and principal stress direction (isoclinic) at every pixel in the image domain based on intensity processing [1]....

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  • ...To get a quantitative comparison, the variation of unwrapped values of θ obtained by FE and experiment are plotted along with the θ calculated theoretically [1] for the line y/R = 0....

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  • ...1e by FE, experiment (after smoothing) [10] and theory [1] T h et a (θ ) A B...

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  • ...The isoclinic values are obtained using a plane polariscope based algorithm of Mangal and Ramesh [1]....

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  • ...In isochromatic phasemaps, one can identify the ambiguous regions from the results of photoelasticity itself by comparing the nature of the phasemap with the dark field image [1]....

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Journal Article•DOI•
Aberration Problem within the Process of Automation of the Photoelastic Measurement of the Stresses

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Oskar Ostertag1, Eva Ostertagová, Peter Frankovský1•
Technical University of Košice1
01 Dec 2014-Key Engineering Materials
TL;DR: In this article, the authors used the tools of the photoelasticity and the effects of the isolines' field recorded through the recording medium to automate the determination of isotropic and orthotropic background stresses.
Abstract: The aim of the paper is the automation of experimental determination of isotropic and orthotropic background stresses by the tools of the photoelasticity and by the effects of the isolines’ field recorded through the recording medium.

1 citations

Cites methods from "Digital Photoelasticity: Advanced T..."

  • ...In addition, the solution was required to be integrated with the program identifying the level of RGB (Red, Green, Blue) components of the isochromatic curves color spectrum moving within the interval of units from 0 to 255 [5, 6, 7, 8, 9]....

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Journal Article•DOI•
The Refraction Indices and Brewster Law in Stressed Isotropic Materials and Cubic Crystals

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Daniele Rinaldi, P. P. Natali, L. Montalto, Fabrizio Daví
10 Sep 2021
TL;DR: In this paper, the authors studied the elasto-optic behavior of stressed cubic crystals and isotropic materials (e.g., glasses) and obtained the explicit dependence of the refraction indices on the stress (either applied or residual).
Abstract: We study the elasto-optic behavior of stressed cubic crystals (all classes) and isotropic materials (like e.g., glasses). We obtain the explicit dependence of the refraction indices on the stress (either applied or residual), as well as a mild generalization of the Brewster law for cubic crystals. We show also that the optic indicatrix and the stress ellipsoid are coaxial only in the isotropic case. This theory allows the improvement of the measurement techniques, as photoelasticity, on cubic crystals and optically isotropic materials.

1 citations

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