FEM for Impact Energy Absorption with Safety Plastic
For the engineering design process to benefit from finite element modeling (FEM), it must adequately represent any condition being studied. This paper presents methodologies for using the LS-DYNA non-linear finite element solver to model a patented energy absorbing technology called SafetyPlastic®. SafetyPlastic® offers a performance, cost, and mass competitive energy management solution, and has been embraced by the automotive industry in both head and side impact occupant protection applications. It is characterized by a connected plurality of structural recesses that repeatedly give resistance, and then buckle when impacted. Due to the nature of SafetyPlastic® and its preferred manufacturing method, a somewhat unique FEM challenge presents itself. The paper provides details related to: • Modeling the strain rate dependent polymeric materials used in SafetyPlastic® • Using a proper mesh size; • Specification of the mesh pattern suitable for the assumptions made when manually inputting thickness profile; • Predicting the wall thickness profile for thermoformed designs via FEM with T-SIM® software; • Transferring and mapping data between T-SIM® and LS-DYNA for FEM; • Selecting the proper responses to evaluate the FEM versus experiment results; • Validating the FEM via quasi static and dynamic impacts with a flat plate; • Validating the FEM via dynamic impacts with a free motion headform; • Assessing the correlation of FEM with experimental results; • Optimizing the size and shape of recesses to promote annular buckling. The data presented show that FEM with LS-DYNA can be performed today with a degree of accuracy that will aid upfront SafetyPlastic® design. This leads to the prospect of conducting optimization studies via design of experiments or otherwise without prototype tooling expenses. However, there is room to improve the overall synchronization of a simulated SafetyPlastic® impact response with a real one. Work to refine and better the FEM methodology is an ongoing effort.
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FEM for Impact Energy Absorption with Safety Plastic
For the engineering design process to benefit from finite element modeling (FEM), it must adequately represent any condition being studied. This paper presents methodologies for using the LS-DYNA non-linear finite element solver to model a patented energy absorbing technology called SafetyPlastic®. SafetyPlastic® offers a performance, cost, and mass competitive energy management solution, and has been embraced by the automotive industry in both head and side impact occupant protection applications. It is characterized by a connected plurality of structural recesses that repeatedly give resistance, and then buckle when impacted. Due to the nature of SafetyPlastic® and its preferred manufacturing method, a somewhat unique FEM challenge presents itself. The paper provides details related to: • Modeling the strain rate dependent polymeric materials used in SafetyPlastic® • Using a proper mesh size; • Specification of the mesh pattern suitable for the assumptions made when manually inputting thickness profile; • Predicting the wall thickness profile for thermoformed designs via FEM with T-SIM® software; • Transferring and mapping data between T-SIM® and LS-DYNA for FEM; • Selecting the proper responses to evaluate the FEM versus experiment results; • Validating the FEM via quasi static and dynamic impacts with a flat plate; • Validating the FEM via dynamic impacts with a free motion headform; • Assessing the correlation of FEM with experimental results; • Optimizing the size and shape of recesses to promote annular buckling. The data presented show that FEM with LS-DYNA can be performed today with a degree of accuracy that will aid upfront SafetyPlastic® design. This leads to the prospect of conducting optimization studies via design of experiments or otherwise without prototype tooling expenses. However, there is room to improve the overall synchronization of a simulated SafetyPlastic® impact response with a real one. Work to refine and better the FEM methodology is an ongoing effort.
05-7.pdf
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