Understanding the effect of anisotropic material model parameters for tube hydroforming simulations

The complete parameterization of complex anisotropic material models for forming simulation of tubes presents signifi cant challenges due to the inherent limitations of tube material testing. Furthermore, the impact of anisotropic material behavior on the hydroforming process, along with the relevance of specific parameters, remains inadequately understood. This study aims to investigate how selected parameters within elastic-visco-plastic anisotropic material models influence hydroforming simulations. Sensitivity analyses are conducted across three distinct characteristic hydroforming geometries, employing a zone-based approach to enable systematic comparison of parameter sensitivities and their correlation with the underlying hydroforming geometries. The results reveal substantial variations in sensitivity driven by differences in plastic strains, diverse strain or stress states, and interactions between neighboring zones. For accurate material modeling of E235 carbon steel tubes in hydroforming applications, determining the true stress-strain curve is basically important. Additionally, experimental quantification of strain rate sensitivity p, uniaxial yield stress σ90, and biaxial yield stress σb is essential for ensuring simulation precision.