A Wrapper Enabling a VUMAT User Subroutine Originally Developed for Simulating Skull Fracture in Abaqus to be Used in LS-DYNA

This report is a guide for using in LS-DYNA the custom vectorized user material (VUMAT) subroutine we previously developed for simulating skull fracture in Abaqus. Our motivation was that computational simulation of head injury requires knowledge of multiaxial stress thresholds to identify the start of functional impairment, but identifying such thresholds continues to be an ongoing area of research. Therefore, we proposed that skull fracture could serve as an interim indication of injury and developed a microstructurally inspired, mechanism-based Hybrid-Experimental-Modeling-Computational (MIMB-HEMC) concept for finite element simulation of skull fracture. The advantages of a MIMB-HEMC approach were demonstrated by close resemblance between numerical and experimental skull fracture patterns, thus generating substantial interest in the MIMB-HEMC concept within the research community. The concept was originally run with a VUMAT in Abaqus/Explicit. This report provides step-by-step directions for using a wrapper to run the VUMAT in LS-DYNA. It also documents simulations that were run to verify the wrapper implementation. Included is a skull indentation simulation with simplified boundary conditions, showing correspondence between the Abaqus and LS-DYNA computations particularly with respect to failure patterns. Finally, the guide highlights how the present wrapper could be extended for use with other Abaqus VUMATs.