Identification of lumped parameter automotive crash models for bumper system development

During the design and development process of bumper systems for the automotive industry, information about the future car model is limited. Normally, iterative finite element (FE) analyses of different crash loading tests are used to find an appropriate bumper system to the coming car model. Because of the lack of information, only a rough model of the car is normally utilised in the FE simulations. This leads to uncertainties in the bumper design since the dynamic response of the car is dependent on the load case and the properties of the actual bumper system. This paper presents a method for identification of lumped parameter models based on results from crash tests of a Volvo S40. The ability to predict the measured results for models with different number of degrees of freedom (DOF) is investigated. Also, a validation of the model together with an FE mesh of the bumper system is presented. The results clearly show that a linear mass spring damper model with 2 DOF can be used to predict the response from the measurements in case of symmetric loading. Further increase of the number of DOF only causes small or no improvements of the agreement between the predicted and measured crash response.