Abstract
Structural failure by fatigue of automotive engine cover is discussed. Fatigue properties of mineral/glass reinforced polypropylene compounds, as an alternative material for engine cover, were measured by experiments. The use of polypropylene compounds offers weight as well as cost reduction. Finite element analysis (FEA) has been performed to investigate the fatigue behavior of the engine cover. Assembly load due to the tightening of the bolts as well as the vibration load was considered to describe the actual loading conditions in durability test. Natural frequency of the system was extracted considering the damping effect of the structure. Dynamic time history of engine cover under vibration load was calculated based on the extracted natural frequency of the system and stress distributions at each load condition were predicted. Experimental modal analysis (EMA) was performed to identify the modal parameters and measurements of strains were performed to verify the results of the analysis. Based on the S-N curve data for engine cover material, distribution of safety factor was predicted by using the FE analysis results. The calculated results were verified by experimental durability tests. Analysis results showed that contribution of the assembly load is not negligible to predict the fatigue failure of the engine cover.
