Finite Element Model Modification of the Mount Bracket Based on Modal Test

The mount bracket is an important part of the mount system, and its dynamic characteristics will affect dynamic characteristics of the mount system, which means it will affect NVH(Noise, Vibration, Harshness) of the vehicle. Based on the large error between the test result and the finite element analysis(FEA) result, the dynamic finite element model of the mount bracket can be modified from the material parameters and the equivalent boundary of the bolt joint. In this paper, a method to identify the parameters of the mount bracket model by combining modal test, FEA, and the mathematical optimization model was presented. Firstly, based on HyperStudy platform, the optimization objective was minimizing the natural frequency error between FEA and free mode test, and the material parameters of the bracket to be identified were used as design variables to build the optimization function. The global response surface method was used for iteration to complete the identification. Then, because the dynamic characteristic parameters of the bolt joints of the mount bracket have an important influence on the test results, an equivalent model using spring element to simulate the stiffness of bolt joints was established. Again, based on the equivalent model and the parameter identification method, the optimization objective was minimizing the natural frequency error between FEA and modal test under constraint conditions, and the stiffness parameters of spring elements were identified by iterative optimization to finish the modification of the mount bracket boundary model. At last, the modified finite element model was applied to the dynamic characteristics analysis of two different mount brackets. The results showed that the maximum error of natural frequency between the simulation value and the test value could satisfy the engineering requirement well, which indicated that the modified model had a good prediction accuracy and engineering application.