Conversion of a User-Defined Bone Material Model from Abaqus to LS-DYNA

DEVCOM Army Research Laboratory researchers had previously developed Abaqus user-defined material models for human bone that could capture the failure behavior observed from experiments. This study aims to translate these materials for use with the LS-DYNA finite element software in support of broader use and validation efforts. After successful translation, four test cases were simulated in LS-DYNA to demonstrate the equivalence between the LS-DYNA and Abaqus material model. These four test cases were a combination of one of two specimens (a cuboid bone block and a hemispherical section of parietal skull) and material model implementations (VUMAT A or B). The simulations with VUMAT A agreed well with the previously published Abaqus results in peak force, time of failure, and extent of failure cascades. The simulations with VUMAT B were very similar as well, with dependencies on the contact implementation and time-step control identified as possible causes for the variations in force-displacement response. The linear crack initiation and propagation behavior was successfully reproduced in both VUMATs. Several appendixes provide further instruction in compiling and using the new LSDYNA materials in other applications.