Fretting Damage Analysis and Predicting of Engine Head and Block

Today engine downsizing, weight reduction, boosting, etc. are widely used in modern combustion engine designs in order to increase power output, improve fuel economy, and reduce emission. However utilizing of these advanced technologies is making the engine less rigidity and resulting in potential fretting damages on any contact surfaces of engine components due to higher cyclic relative motions. The leakage failure of the cylinder-head sealing system induced by fretting damage on engine head and block deck surfaces is the one of major failure modes in the modern combustion engine. In this paper, the characteristics and failure modes of the MLS head gasket sealing system is introduced first. The fretting mechanism between MLS head gasket and engine head and block is then investigated and a fretting damage parameter and a damage criterion as well are defined and established to evaluate the crack nucleation or wear initiation. Also it is important to identify two types of loads during engine operation in the fretting damage calculation. The developed methodology is successfully verified through a good correlation between CAE analysis and actual engine thermal shock tests. This approach and results discussed in this paper provides a good guidance for the fretting damage analysis, assessment, and predicting of engine head and block deck surfaces.