Evaluación experimental del fenómeno de 'crack shielding' inducido por plasticidad empleando técnicas de campo completo para la medida de tensiones y deformaciones

Resumo

The current thesis presents the eva luation and quantification of plasticity-induced crack shielding on fatigue crack growth in mechanical elements . For that, three full-field experimental optical techniques have been employed : transmission photoelasticity, digital image correlation (DIC) and electronic speckle pattern interferometry (ESPI) . Thus, the crack shielding effect has been evaluated from the analysis of the stress intensity factors (SIFs), for which an experimenta l methodology for SIF calculation has been developed . This analysis has been conducted by studying four different models to describe crack tip stress and displacement fields, namely Westergaard 's, Williams's, Muskhelishvili's and CJP models. The methodology has been successfully implemented by conducting severa ! fatigue tests on CT specimens . Results obtained with DIC have been compared with those obtained by standard techniques.