CAE Virtual Design Validation Tests of Automotive Engine Mount Systems 2009-01-0404

This paper presents a CAE virtual test procedure for automotive engine mount systems, which evaluates NVH and durability performance of an engine suspension design. Engine mount systems are virtually tested in terms of noise and vibration response characteristics, mount structural strength and fatigue durability, under the defined engine load conditions. The proposed procedure incorporates several CAE modeling and simulation technologies, including the definition of engine test loading environment, the modeling of nonlinear rubber bushings for their stiffness and damping properties, the frequency domain dynamic simulation, and fatigue damage prediction technologies. First, the test engine load specifications are defined from the measured engine vibration raw data with respect to engine speeds, and the engine speed duty cycle statistics. Secondly, the nonlinear rubber bushing properties are modeled as equivalent stiffness and damping elements in each of the mount directions, based on the measured dynamic bushing parameters, in the frequency domain. The dynamic simulations are then realized by using the frequency response analysis technique, for both NVH and durability performance tasks. The engine NVH performance is evaluated in terms of engine vibration isolation and noise transmission characteristics. For the mount bracket strength and durability, a method of fatigue damage prediction in frequency domain is introduced. The dynamic stresses of brackets are first simulated and sorted for potential high stress spots. The durability of each bracket structure then is evaluated based on the simulated stress and the corresponding material damage model. Automotive engine mount examples are provided to illustrate applications of the proposed virtual test procedure and associated techniques.