Light weighting in modern automotive powertrains call for use of plastics (PP, PA66GF35) for cam covers, intake manifolds and style covers, and noise encapsulation covers. Conventionally, in early stage of design these components are evaluated for static assembly loads & gasket compression loads at component level. However, engine dynamic excitations which are random in nature make it challenging to evaluate these components for required fatigue life.
In this paper, robust methodology to evaluate the fatigue life of engine style cover assembly for random vibration excitations is presented. The investigation is carried out in a high power-density 4-cylinder in-line diesel engine. The engine style cover (with Polyurethane foam) is mounted on cam cover and the intake manifold using steel studs and rubber isolators to suppress the radiated noise. The style cover mounting ribs experience higher dynamic bending stresses due to the overhang of the mounting bosses from cam cover and intake manifold. The random vibration fatigue analysis provides good assessment for fatigue life of these components. The Computer Aided Engineering (CAE) results show good correlation with durability testing.
The present work also covers the FE modelling techniques, material data and damping consideration in simulation for plastics for vibration fatigue analysis.