Development of Evaluation Method for Low-Cycle Fatigue Breakdown on HSDI Diesel Cylinder Head
With a growing demand for high-power diesel engines, a key issue in engine development is to create efficient methods for developing highly durable cylinder heads, without having to repeat trial-and-error testing. Especially, it was difficult to accurately predict the occurrence and origin of cracks on the surfaces of cylinder heads in hot and cold cycle engine operation. This paper describes a thermal fatigue evaluation method developed by analyzing areas around the glow plug hole where cracks often occur during hot and cold cycle engine operation. To reveal the conditions of edges from which cracks were formed under engine durability tests, we used two procedures. One was estimating local temperature of edge areas based on material hardness determination, in order to compensate for the accuracy of the thermal analysis. The other was analyzing the strain amplitudes on the cylinder head surface using computer simulation.