Finite Element Model refinement of powertrain mount brackets for estimating natural frequencies

Abstract

Natural frequencies of powertrain mount brackets have great influences on NVH (Noise, Vibration, Harshness) performances of a Powertrain Mount System. Usually, large relative error between the measured- and the estimated natural frequencies using finite element analysis existed. In this paper, a methodology to refine the mount bracket finite element model is proposed based on global response surface method and optimization methods. The material parameters uncertainty and the constraint boundary (bolt joint) are taken into account for model update parameters, since they are the main factors affecting the accuracy of the calculated natural frequencies of bracket. The material parameters are optimized by minimizing the errors between calculated and measured un-constrained natural frequencies of the mount bracket. The bolt joint are modeled using the equivalent stiffness of spring element that are optimized by minimizing the deviations between the calculated and measured constrained natural frequencies of the bracket. Another mount bracket is used to obtain natural frequencies calculated using the refined finite element model and measured, and the comparisons of the calculated versus the measured natural frequencies shown that the refined finite element model of mount bracket with identified material parameters and boundary stiffness values exhibits high prediction precision for estimating natural frequencies of the brackets. This indicates that the proposed finite element model refinement methodology for mount bracket is effective and can help the NVH engineers to design larger natural frequencies of mount brackets.