||January 1, 2008
Finite element modeling has been used extensively in designing automotive engines and subsystems for evaluating the sealing and NVH (noise/vibration/harshness) performance. The elastomeric components exhibit the nonlinear stress-strain responses and frequency-dependent viscoelasticity, and often have contact interferences with mating components. Directly including detailed elastomeric components into the three-dimensional finite element models of the engines or subsystems has been impractical. Therefore, the elastomeric components at the interfaces are often omitted in the system finite element models because of the lack of computationally “effective” elements. The paper presents a methodology to model the elastomeric components for sealing and NVH applications using newly developed viscoelastic gasket elements. The viscoelastic gasket element is a one-dimensional element with load and deflection defined in the thickness direction only. Thus it has great computational efficiency. In addition, this element has the ability to incorporate the frequency-dependent viscoelastic properties of the materials and thus can be used to analyze the NVH performance of the engines and subsystems. In the present study, an elastomer isolated engine cylinder-head cover assembly is used as an example. The finite element modeling includes two steps. First, detailed local finite element analyses are performed on elastomeric gaskets and grommets to capture their nonlinear load-deflection and contact interferences. Secondly, a global finite element model of the cover assembly is constructed where the gaskets and grommets are remodeled with one-dimensional, viscoelastic gasket elements. The forced response dynamic analysis is performed to compute the vibration at the cover surface. The results are consistent with the experimental measurements and with the work done earlier using viscoelastic shell elements.