Approaches to Modeling the Dynamic Interaction for an Automotive Seat and Occupant System

There are a wide variety of approaches to model the automotive seat and occupant interaction. This paper traces the studies conducted for simulating the occupant to seat interaction in frontal and/or rear crash events. Starting with an initial MADYMO model, a MADYMO-LS/DYNA coupled model was developed. Subsequently, a full Finite Element Analysis model using LS/DYNA was studied. The main objective of the studies was to improve the accuracy and efficiency of CAE models for predicting the dummy kinematics and structural deformations at the restraint attachment locations in laboratory tests. The occupant and seat interaction was identified as one of the important factors that needed to be accurately simulated. Quasi-static and dynamic component tests were conducted to obtain the foam properties that were input into the model. Foam specimens and the test setup are discussed. Different material models in LS/DYNA were evaluated for simulating automotive seat foam. Some of the run-time difficulties with using solid elements for the simulation are also addressed. Penetration issues of the dummy to the seat finite element analysis model can be resolved using a settling run or morphing techniques. Additional parameters that could affect simulation results include the dummy positioning, friction between the contact surfaces and seat belt properties. In addition to the cushion, there is compliance from the supporting structure, which includes the seat mat and the springs that connect to the seat frame. The conclusion from these studies is that a full finite element analysis code is best suited for modeling the details of the seat structure and the seat foam material as well as the dummy components. Some level of component testing is required for validating and advancing the prediction capability of CAE models.