Fracture Prediction of Inconel Sheet Deformed under Different Stress States

Abstract

The present work focuses on the prediction of onset of fracture for thin-walled metallic sheets used for forming complex shape and lightweight components for aerospace applications. The Lou-Huh ductile damage model has been used along with Barlat 1989 anisotropic yielding function for the prediction of fracture limits of Inconel alloy in different stress states, namely, pure shear, uniaxial tension, pure strain and equi-biaxial tension. Nine different types of specimens have been deformed experimentally till the occurrence of fracture using simple tensile test and stretch forming setup. The principal stresses at the onset of fracture have been determined experimentally and numerically and plotted in the major-minor strain space and, further, have been transformed into the effective plastic strain to fracture vs. stress triaxiality space. The fracture sites in the numerical simulations have been found to be consistent with the experimental results. Cockcroft-Latham, Brozzo, Oh and Rice-Tracey model have also been used for determining the fracture locus but the Lou–Huh model has only been found to accurately predict the fracture limit in all the stress states for a wide range of stress triaxiality as it considers the effect of shear-linkage of voids.