Journal ArticleDOI
Completely automated determination of two-dimensional photoelastic parameters using load stepping
Matthew J. Ekman,Andrew D. Nurse +1 more
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In this paper, a ramped phase map for the isochromatic parameter is produced in the range -?<??? that can be unwrapped using conventional techniques, and the value of the isoclinic angle is automatically determined in the correct range without unwrapping.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 -?<??? that can be unwrapped using conventional techniques. Calibrated values of a can then be calculated using the phase map of ??, which is the incremental change in the isochromatic value between the different steps. The value of the isoclinic angle is automatically determined in the correct range -?/2<?????/2 without unwrapping. The results obtained from experimental testing of a disk-in-compression specimen using transmission photoelasticity presented in comparison with theoretical solutions demonstrate the accuracy of the new approach. In another test performed on a bar in torsion using reflection photoelasticity we demonstrate how determination of the isoclinic angle in the range -?/2<???/2 gives results superior to those obtained if the isoclinic angle is determined in the wrapped range -?/4<???/4 .read more
Citations
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Journal ArticleDOI
Whole field evaluation of stress components in digital photoelasticity—Issues, implementation and application
TL;DR: In this paper, a quality guided approach for isoclinic unwrapping is developed, which uses a ten-step phase shifting approach to obtain a smooth variation of the digital photoelastic parameters over the domain.
Journal ArticleDOI
Digital photoelasticity – A comprehensive review
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.
Journal ArticleDOI
Adaptive Quality Guided Phase Unwrapping Algorithm for Whole-Field Digital Photoelastic Parameter Estimation of Complex Models
TL;DR: In this article, a 10-step phase-shifting methodology is proposed and a new strategy for obtaining the isochromatic phasemap free of ambiguity is demonstrated.
Journal ArticleDOI
Improved method for isochromatic demodulation by RGB calibration.
TL;DR: This work has improved the standard demodulation algorithm used in RGB calibration by changing the Euclidean cost function to a regularized one in which the fidelity term corresponds to the Euclidan distance between RGB triplets; the regularizing term forces piecewise continuity for the isochromatic retardation.
Journal ArticleDOI
Dynamic phase-shifting photoelasticity.
TL;DR: Use of a Multispec Imager is introduced into digital photoelasticity for the first time to the authors' knowledge, which enables splitting the optical energy of an object into four identical paths, thus permitting recording of the required four phase-shifted images.
References
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Journal ArticleDOI
Robust two-dimensional weighted and unweighted phase unwrapping that uses fast transforms and iterative methods
TL;DR: In this article, a robust method for 2D phase principal values (in a least-squares sense) by using fast cosine transforms was developed, which can be used to isolate inconsistent regions (i.e., phase shear).
Journal ArticleDOI
Towards full field automated photoelastic analysis of complex components
Eann A. Patterson,Z F Wang +1 more
TL;DR: The design of a automated system for photoelastic analysis of complex components and the potential of the system for providing detailed data over the full field of view is demonstrated by the analysis of a slice from a model of a bolt.
Journal ArticleDOI
New approaches to the full-field analysis of photoelastic stress patterns
C.H. Buckberry,David P. Towers +1 more
TL;DR: Two new methods are presented that provide a complete solution for the automatic fringe analysis of photoelastic data and a new method is proposed that removes the areas of 2π ambiguity in an isoclinic phase map by cross-correlating regions of low modulation at two different wavelengths.
Journal ArticleDOI
Use of phase-stepping with demodulation and fuzzy sets for birefringence measurement
Z.F. Wang,Eann A. Patterson +1 more
TL;DR: A new strategy for processing phasestepped data from birefringent materials is proposed and involves demodulation of intensity signals and the classification of periods of data using fuzzy sets.
Journal ArticleDOI
Completely automated photoelastic fringe analysis
TL;DR: Results show that the analysis carried out with the combined system of photoelastic analysis, incurred errors no longer than those of each system working independently.
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