Division of Information Technology, Engineering and the Environment
School of Advanced Manufacturing and Mechanical Engineering
School of Advanced Manufacturing and Mechanical Engineering
Thesis Abstract
With the increasing completion in the automotive market, development of more comfortable seats is becoming of higher value to OEMs and seat producers. Using tradition development techniques of prototype building and physical testing, the development of an automotive seat tend to be very costly and time-consuming. On the contrary, more efficient techniques can be developed if the digital modelling domain was exploited by the automotive industry. In this study, a Finite Element (FE) model of a seat cushion and a butt-shaped indenter was developed in ANSYS WorkBench v13.0. The seat cushion was modelled as an Ogden Hyperelastic material, where the foam used to build the seat cushion was assumed to be open-cell foam, and was modelled to have a density of 39 kg.m-3 and a Young’s modulus of elasticity of 20kPa. Additionally, Poisson’s effect was considered to have minimal influence over the foam behaviour and so, Poisson’s ratio was assigned a zero value in the model. The seat structure and the trampoline-like cushion supports were assumed to behave within their elastic region and were modelled as linear elastic isotropic steel with density of 7.8 *103 kg.m-3, Young’s modulus of elasticity of 200 MPa and Poisson’s ratio of 0.3 [1]. Previous trials to include butt-shaped indenters were done by Shin and Vertiz [2] and Verver [3], however both studies used a wooden butt-shaped indenter. While this approach may seem like an accurate replication of what happens when a driver settles in a seat, in reality it provides poor approximation for part of the load range [4]. This is because the shape of the driver’s buttocks is influenced by the foam hardness and may change under different loading conditions. To obtain an accurate representation of a driver’s buttocks, the indenter used in this study had a butt-shaped solid structure surrounded by Neoprene foam on the outside. The Neoprene foam reflected the hyper elastic properties of soft-tissues, whereas the solid structure represented the bony-skeleton underlying the soft-tissues in a human body. The model was correlated against test data supplied by an automotive seat manufacturer.
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