Search Results

The reduction of engine weight is today a widely used and effective approach to increasing automotive fuel efficiency . However, the realization of weight savings in the engine can increase deformation of the crankshaft and cylinder block, resulting in fretting fatigue of the contact surfaces of the bearing caps and the cylinder block. Although researchers have identified the mechanism of fretting fatigue on the cylinder block, as yet there is no effective method of addressing the issue in the development stage. The research discussed in this paper applied quality engineering methods to investigate a variety of factors considered to influence fretting fatigue in unit test equipment. The results of the study indicated a good correlation between unit tests and actual engine tests. The paper will also discuss analytic methods for obtaining basic materials data, and methods of prediction of fretting fatigue at an early design stage.

The independent bearing cap is a cylinder block bearing structure that has high mass reduction effects. In general, this structure has low fastening stiffness compared to the rudder block structure. Furthermore, when using combination of different materials small sliding occurs at the mating surface, and fretting fatigue sometimes occurs at lower area than the material strength limit. Fretting fatigue was previously predicted using CAE, but there were issues with establishing a correlation with the actual engine under complex conditions, and the judgment criteria were not clear, so accurate prediction was a challenge. This paper reports on a new CAE-based prediction method to predict the fretting damage occurring on the bearing cap mating surface in an aluminum material cylinder block. First of all, condition a fretting fatigue test was performed with test pieces, and identification of CAE was performed for the strain and sliding amount.