Optimal analysis procedure for dynamic FE simulation of car door close cycle

Abstract

The Durability Department of Volvo Cars (Gothenburg) is interested in modifying its approach to the finite element (FE) analysis of the door sealing system. The sealing system is a complex and important component in a door closing event. Volvo Cars currently uses an implicit FE solver in a model in which nonlinear spring elements describe the relationship between the forces and displacements in the sealing system. Volvo Cars has proposed to switch to using LS-Dyna which has an explicit solver. Explicit solvers are more computationally effective than implicit solvers and it enables Volvo Cars to use the same FE-software for the analysis of different loading situations, and also to be able to use a better geometric and material model for the sealing system. Volvo Cars has expressed that with the use of LS-Dyna, dependency on the physical testing could be reduced. The development of a working explicit model of a Volvo car door that captures the static and dynamic behaviour of the sealing system during a door closing event is presented. It is developed for LS-Dyna based on existing knowledge from the implicit solution and data received from the implicit model. To model the rubber sealing system in an explicit solver, both the static and dynamic behavior of the sealing system are needed. The static behaviour for the rubber sealing is estimated using a hyper-elastic material with Yeoh material model. Three material constants in the Yeoh material model (C10, C20 and C30) that affect the stiffness of the sealing system are determined using a quasistatic simulation of a section of the sealing with a prescribed motion of the door closing event. The constants are selected using a curve fit analysis. To capture the dynamic behaviour of the sealing system an existing LS-Dyna airbag model is used. The airbag model made it was possible to estimate the evacuation of the airflow out from the sealing system during the closing event. The unknown parameter that had to be established in the airbag model was the shape factor. The shape factors will be determined by comparing the measured acceleration signals provided by Volvo Cars to the simulated acceleration signals. By comparing the acceleration signals it is possible to determine which values of the shape factors gives the best signal correlation. Finally, it is concluded that the evacuation of air from the sealing system during a door closing event can be estimated by the working explicit model of a Volvo car door. It is recommended that additional studies be carried to determine the applicability of the model to a variety of doors and sealing geometries.