Publication

In order to obtain reliable and realistic results for a human body model in a car crash simulation, having a suitable constitutive model for muscle tissue with both passive and active properties, is of great importance. Skeletal muscles have experimentally shown to have mechanical features including Anisotropy of the muscle; Contraction of the muscle bers due to external stimuli, known as activation, which is also length and velocity dependent; Non-linear and rate dependent behavior also without activation. A literature study was conducted, and many previous studies describing the active and passive muscle behavior in context of continuum mechanics were investigated. Some suitable modeling approaches were selected; then, an explicit FE formulation based on large deformation was developed, and implemented in a Matlab environment. The simulation results of the dierent approaches were assessed, and the most promising material model was chosen. This model is supposed to be implemented as a user material routine in LS-DYNA software using Fortran code. The implemented model used a Hill-type relation for the active muscle behavior. For the numerical solutions in the FE analysis, the central dierence scheme as an explicit method was mainly focused on. One of the main problems in the FE analysis was instabilities occurring during the time iterations which is mainly due to the nearly incompressible material property of the muscle. In some cases, by assigning appropriate parameters and adjusting constants this problem was solved. Methods for treating such problems was tested; for instance, the reduced selective method was implemented in this thesis project, but satisfying results were not achieved.