Abstract
In the current paper a new method for calculating the stress intensity factor from isochromatic data is proposed. The method is based on the calculation of a map of the retardation using only the light- and dark-field images of a crack from a circular polariscope. The experimental retardation is compared with the theoretical one predicted by Westergaard’s model using between 700 and 800 data points in an array around the crack tip region. In this way, the necessity of unwrapping and calibrating the isochromatic fringe order distribution is avoided and a large potential source of error is eliminated. Subsequently, KI, KII and σox are inferred by minimizing an error function. To show the potential and efficacy of the method, K values have been obtained from photoelastic images captured during fatigue tests conducted in a polycarbonate Center-Cracked-Tension (CCT) specimen. Results show an excellent level of agreement with those predicted from theory, highlighting the potential of the proposed methodology.
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Acknowledgements
This work has been conducted with the financial support of the Spanish Ministerio de Educación y Ciencia through the research project MAT2006-09350 del Plan Nacional de I + D. The authors also gratefully acknowledge the support provided by the research mobility program José Castillejo. The generosity of the Department of Mechanical Engineering at Michigan State University in providing laboratory facilities is gratefully acknowledged.
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Diaz, F.A., Patterson, E.A. & Siegmann, P. A Novel Experimental Approach for Calculating Stress Intensity Factors from Isochromatic Data. Exp Mech 50, 273–281 (2010). https://doi.org/10.1007/s11340-009-9282-1
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DOI: https://doi.org/10.1007/s11340-009-9282-1