Localization prediction in tension-and shear-dominated stress states in aluminum tension-torsion tests using coarsely meshed shell elements

Abstract

An important challenge associated with evaluating the crash energy absorption capacity of large thin-walled structures such as ships in numerical simulation is the use of large shell elements. Due to their large size, they cannot capture the formation of strain localizations, which often precedes ductile fracture. The prediction of localization formation under tension-dominated stress states is well-researched area given its application in metal forming, reflected by the accuracy and variety in localization prediction models. However, localization prediction under shear-dominated stress states has received significantly less attention. The objective of this work is to predict localization formation under a wide range of stress states, including both tension- and shear-dominated stress states. This work is based on prior experiments on aluminum tension-torsion samples, with a stress triaxiality (denoted η) varying between 0 and 1/√3. These experiments are first replicated in ABAQUS using both high-fidelity axisymmetric elements and shell elements of various sizes. It is found that the application of Hill’s localized necking criterion using a cumulative damage formulation in shell elements gives good agreement for all tested stress states and shell element sizes. The use of Hill’s criterion as a surrogate fracture criterion in numerical simulation should be further investigated for common marine materials.