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Published April 2009 | public
Journal Article

Phase shifting full-field interferometric methods for determination of in-plane tensorial stress


A new method that combines phase shifting photoelasticity and transmission Coherent Gradient Sensing (CGS) is developed to determine the tensorial stress field in thin plates of photoelastic materials. A six step phase shifting photoelasticity method determines principal stress directions and the difference of principal stresses. The transmission CGS method utilizes a standard four step phase shifting method to measure the x and y first derivatives of the sum of principal stresses. These stress derivatives are numerically integrated using a weighted preconditioned conjugate gradient (PCG) algorithm, which is also used for the phase unwrapping of the photoelastic and CGS phases. With full-field measurement of the sum and difference of principal stresses, the principal stresses may be separated, followed by the Cartesian and polar coordinate stresses using the principal stress directions. The method is demonstrated for a compressed polycarbonate plate with a side V-shaped notch. The experimental stress fields compare well with theoretical stress fields derived from Williams solution for a thin plate with an angular corner.

Additional Information

© 2009 Society for Experimental Mechanics. Received: 7 September 2008 / Accepted: 29 January 2009 / Published online: 27 February 2009. We gratefully acknowledge the support of the National Science Foundation (DMR # 0520565) through the Center for Science and Engineering of Materials (CSEM) at the California Institute of Technology, of the American Society for Engineering Education National Defense Science and Engineering Graduate (NDSEG) Fellowship Program, and of the National Science Foundation Graduate Research Fellowship Program. We thank Prof. E.A. Patterson for valuable discussions during this project.

Additional details

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