Absolute determination of the isochromatic parameter by load-stepping photoelasticity |
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Authors: | M J Ekman A D Nurse |
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Institution: | (1) Department of Mechanical Engineering, Loughborough University, LE11 3TU Loughborough, U.K. |
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Abstract: | A new approach to full-field automated photoelasticity is presented in which a circular polariscope is used to enable the isochromatic phase value ( ) to be determined unambiguously and without input of a known isochromatic value obtained using an auxiliary technique. Values of cos are obtained from light-field and dark-field images for three loads of small incremental steps. Using a relatively straight-forward procedure, ramped phase maps for are produced which can be unwrapped using conventional techniques. The resulting distribution of is then found absolutely using information provided by which ![delta](/content/q7g0330067424m25/xxlarge948.gif) is the incremental change in the isochromatic phase value between the load steps. The results obtained for disk-in-compression tests presented here in comparison with theoretical solutions demonstrate that the technique is both simple to use and very accurate. A similar approach may be adopted using three wavelengths instead of three load steps. |
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Keywords: | Automated photoelasticity isochromatics contact stresses circular polariscope |
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