Strength Analysis of a Cylinder Head Gasket Using Computer Simulation 2009-01-0197
The properties sought in a multi-layer steel cylinder head gasket include cylinder pressure sealing and fatigue strength in order for there to be no damage while the engine is in operation. Diesel engines, in particular, have high cylinder pressure and a high axial tension by the cylinder head bolt demanding severe environment to the gaskets. As engine performance is enhanced, there are cases when cracks develop in the gasket plate, necessitating countermeasures. The cause of cracking in a flat center plate, in particular, has not yet been explained, and no method for evaluation had previously existed. Three-dimensional non-linear finite element calculation was therefore performed to verify the cause. First, a static pressurization rig test was used and the amount of strain was measured to confirm the validity of the calculations. Then the same method of calculation was used to verify the distribution of strain, with a focus on the plate position. This showed that strain occurred in the direction of cracking depending on the relative positions of the plates. Estimates were then calculated using a model equivalent to an actual engine endurance test. These yielded high strain, indicating that the cause of cracking was a gap of plate position. The method of calculation created here showed that when the center plate thickness was varied, increasing that thickness was effective in reducing strain. Optimization of the center plate thickness made it possible to complete endurance testing of an actual engine without cracking.