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Finite element modeling has been used extensively nowadays for predicting the noise and vibration performance of whole engines or subsystems. However, the elastomeric components on the engines or subsystems are often omitted in the FE models due to some known difficulties. One of these is the lack of the material properties at higher frequencies. The elastomer is known to have frequency-dependent viscoelasticity, i.e., the dynamic modulus increases monotonically with frequency and the damping exhibits a peak. These properties can be easily measured using conventional dynamic mechanical experiments but only in the lower range of frequencies. The present paper describes a method for characterizing the viscoelastic properties at higher frequencies using fractional calculus. The viscoelastic constitutive equations based on fractional derivatives are discussed. The method is then used to predict the high frequency properties of an elastomer.

The Plastic Valve Cover System (PVCS) should provides a leak proof seal to the cylinder head under engine temperature, isolate the vibrations transmitted from the engine through the cover to the environment, control the crankcase pressure and house the device to separate oil from the blow-by gas. In order to increase the stiffness of PVCS, short glass fibers and minerals are added during the injection molding of the plastic valve cover. The presence of the fibers results in a component with highly anisotropic thermo-mechanical properties that was not accounted in the previously approach [1]. This paper describes the updated CAE approach with the incorporation of the short fiber anisotropy into the design of cylinder head valve covers.