Photoelasticity is one of the most widely used full-field methods for experimental stress analysis. However, the collection of photoelastic parameters can be a long and tedious process. The advent of automated photoelastic systems has allowed the experimentalists to speed up the rate of analysis and to perform more complex investigations.This paper provides a survey of recent methods of automated photoelasticity developed in the last 20 years, i.e. methods of the fringe centres, half-fringe photoelasticity, phase-stepping photoelasticity, methods based on the Fourier transform, spectral content analysis (SCA) and RGB (red, green, blue) photoelasticity.

A review of automated methods for the collection and analysis of photoelastic data

Digitally whole-field analysis of isoclinic parameter in photoelasticity by four-step color phase-shifting technique

A novel instrument is described for the simultaneous observation and capture of four phase-stepped photoelastic images. A theoretical description of the optics of the instrument is presented for the first time. Three examples are given of the use of the instrument in reflection photoelasticity to generate full-field maps of isochromatic and isoclinic parameters. The results from these experiments show close correlation to results from both theoretical analyses and manual measurements. The instrument can be used in either reflection or transmission mode and it is concluded that the new instrument significantly enhances the potential for real-time studies using reflection photoelasticity.

Simultaneous observation of phase-stepped images for automated photoelasticity

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.

Digital photoelasticity – A comprehensive review

In recent years phase-measuring techniques have been applied to the problem of extracting information of photoelastic data. We present a new phase-measuring algorithm for extraction of the isochromatics of photoelastic fringe patterns. The algorithm permits the extraction of the isochromatic phase with almost no influence from the isoclinics, thus avoiding the usual problems of low-modulation areas associated with isoclinics. The isochromatic phase map obtained with this algorithm is well suited for a full separation of the stress components in a sample. The algorithm can be used with any commercial diffuse-light circular polariscope.

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Phase measuring algorithm for extraction of isochromatics of photoelastic fringe patterns

A new computerized method for the whole-field determination of isoclinic and isochromatic parameters in a stressed photoelastic model is presented The intensity data obtained from the fringe pattern at three analyzer positions (0, 45, and 90 degrees) in a plane polariscope, are used for the computations The relationships between the intensity values and the photoelastic parameters are derived using Stokes representation of polarized light The experiments were carried out using a computer-based image-processing system The accuracy achieved is assessed by comparing the theoretical and measured values Accuracies of within ±3 degrees for isoclinics and ±005 fringe for isochromatics are shown to be possible

Computerized image processing for whole-field determination of isoclinics and isochromatics

This book follows a simple approach, and introduces analytical procedures to analyze various structural members subjected to different types of loading with step-by-step problem-solving procedure is discussed.The book covers some advanced topics like curved beams, shear center, unit load method. Aa exclusive chapter on "Solving through ANSYS" covers the approach and usage of ANSYS software. Note: T& F does not sell or distribute the Hardback in India, Pakistan, Nepal, Bhutan, Bangladesh and Sri Lanka. 

T. K. Varadan

Papers

Computerized image processing for whole-field determination of isoclinics and isochromatics

Strength of Materials

Detection and characterization of tight cracks by using photoelastic coatings