Recent LS-DYNA Developments in the Structural Conjugate Heat Transfer Solver

Increasing demands for the simulation of complex, multi-physics problems in crashworthiness and manufacturing process analyses have necessitated new developments in the structural conjugate heat transfer solver in LS-DYNA®. Some of the most recent extensions and new implementations are presented and discussed in this contribution. The first block addresses the relatively new field of battery abuse simulations. Focus is put on a novel thermal composite thick shell element that is defined using *PART_COMPOSITE_TSHELL. On the one hand, the implementation allows for a relatively easy input definition. On the other hand, the formulation adds new temperature degrees of freedom for each layer of the composite structure and, thus, accurately resolves the internal lay-up of the structure, i.e. the battery cell. The reconstructed lay-up is also accounted for in the thermal contact routines. Consequently, the heat transfer through a stack of solid elements can be reproduced exactly by a single composite thick shell element with the corresponding lay-up definition. The second block presents the work on different thermal boundary conditions. A recent enhancement enables the “standard” boundary conditions (convection, radiation, and flux) to be transferred to newly exposed surfaces after element erosion. In general, this is sufficient for modeling laser cutting with a flux boundary condition, but the input of such a model can become very complex. Therefore, a new thermal boundary condition *BOUNDARY_FLUX_TRAJECTORY is introduced in the second part of this block, which is tailored for moving heat sources acting on the surface of a structure. In contrast to the standard flux boundary condition, the new implementation also accounts for the tilting of the heat source. The boundary condition is applicable in coupled thermal-structural and thermal-only simulations. The second block is completed by the presentation of a new temperature boundary condition *BOUNDARY_TEMPERATURE_RSW that is devised as a simplified modeling strategy for resistive spot welds (RSW). With the keyword, the temperature distribution in a weld nugget is defined directly.