The stress intensity of mixed mode cracks determined by digital image correlation

Abstract

A generalized approach for determining the stress intensity factors (SIFs) K I and K II for any mode mixity directly from displacement fields obtained by digital image correlation is presented using a centre fatigue cracked aluminium plate as an example problem. It was found that the crack-tip position could be determined on average to within 50 per cent of the displacement vector spacing (60 μm). The approach has been shown to be fairly robust, both in terms of the stability of the SIFs thus obtained and their sensitivity (less than 0.07 MPa

Characterisation of overloads in fatigue by 2D strain mapping at the surface and in the bulk

“…The accuracy of DIC to measure elastic strain is debateable, but its capability to measure total strain (considering that plastic strains are normally few times bigger than elastic strains) is unrivalled [12]. DIC has found increasing application for the study of crack-tip strain fields [13] and it has been possible to extract fracture mechanics information such as closure stresses [14,15], plastic zone sizes [16], crack-tip opening displacements (COD) [17] and effective stress intensity factors at the crack-tip, K eff [12,16,[18][19][20].…”

Williams expansion-based approximation of the stress field in an Al 2024 body with a crack from optical measurements

“…When the crack is subjected to mixed-mode loads [19], Eq. 2 and 3 also include a shear mode component that allows the shear mode SIF to be estimated [20], [21].…”

Mid-thickness studies of the stress intensity factor in the bulk of bainitic steel

“…he experimental characterisation of crack tip fields is normally done using surface techniques such as photoelasticity [1], Moiré interferometry [2], thermo-elastic stress analysis [3], electronic speckle pattern interferometry [4] or digital image correlation [5,6]. For thin components, the surface behaviour is normally representative of the T complete behaviour [7].…”