Abstract
This paper presents a technique for the experimental measurement of stress intensity factors in cracked specimens under mixed-mode loading. This technique is based on full-field measurement using digital image correlation and an interaction integral. Such domain-independent integrals are often used in the finite element method to calculate stress intensity factors. The main advantage of this technique is that the errors made in the estimation of the measured displacement field near the crack’s tip do not affect the measurement of the stress intensity factors. The capabilities of the method are illustrated through fracture measurements on compact tension specimens made of maraging steel. Another test under mixed-mode loading is presented.
Highlights
Over the past few years, digital image correlation has been developed for the measurement of displacement fields on plane surfaces (Sutton et al, 1983, 1986; Touchal-Mguil, 1997)
Improvements in the numerical computation of stress intensity factors were achieved in the framework of the finite element method: several techniques were proposed to estimate the energy release rate (Irwin, 1957) or the J -integral (Rice, 1968) and the stress intensity factors by computing domain-independent integrals using the concepts of virtual crack extension (Destuynder et al, 1983; Moran and Shih, 1987) and auxiliary fields (Bui, 1978)
First, we briefly presented the digital image correlation technique used for the measurement of displacement and strain fields
Summary
Over the past few years, digital image correlation has been developed for the measurement of displacement fields on plane surfaces (Sutton et al, 1983, 1986; Touchal-Mguil, 1997). Improvements in the numerical computation of stress intensity factors were achieved in the framework of the finite element method: several techniques were proposed to estimate the energy release rate (Irwin, 1957) or the J -integral (Rice, 1968) and the stress intensity factors by computing domain-independent integrals using the concepts of virtual crack extension (Destuynder et al, 1983; Moran and Shih, 1987) and auxiliary fields (Bui, 1978) These techniques make the determination of local characteristics (stress intensity factors) possible using global quantities (domain-independent integrals). The capabilities of the method are illustrated through several examples
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