Stable crack growth in Al-Cu-Mg alloy under various stiffness of loading system in bodies with concentrators

Abstract In the present work, the influence of the stiffness of the loading system on regularities of inelastic behavior and on processes of the equilibrium crack growth during uniaxial tension in bodies with stress concentrators was studied. Flat specimens (Al-Cu-Mg alloy) with a center notch and initial fatigue crack were extended with a biaxial servo-hydraulic testing system Instron 8850 at room temperature. The mechanical tests were complemented by a digital image correlation (DIC) and an infrared thermography. By using the 3D DIC-measurement system Vic-3D and the software module ‘virtual extensometer’, it was possible to evaluate the crack opening value, to analyze the evolution of heterogeneous strain fields during the initiation and propagation of cracks. It was revealed that with increasing stiffness of the loading system (by decreasing the gauge length of specimens), the realization of the stable postcritical deformation stage is increasing as well as the inhomogeneity of plastic flow and temperature in the crack tip.