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A piston in a diesel engine is subject to the high pressure and the high thermal load. The high structural reliability is required to the piston in the automotive diesel engine and it is important to confirm the design parameters of piston in initial design stage. There are lots of research works proposing new geometries, materials and manufacturing techniques for engine pistons. But, the failures of piston occur frequently in development stage. Failure mechanisms are mainly fatigue related. This paper presents failure mechanisms of the high cycle fatigue and low cycle thermal fatigue cracks which occur on the piston during durability test using engine dynamometer. In this study, FE analysis was carried out to investigate the root cause of piston failure. The analysis includes the FE model of the piston moving system, temperature dependent material properties, mechanical and thermal loadings.

In order to cope with new exhaust emission regulations, automotive industry is interested in research and development of HSDI (High Speed Direct Injection) diesel engines with common rail systems. Since HSDI diesel engine operates under highly loaded condition due to increased power output, cylinder head of HSDI diesel engine is susceptible to high cycle fatigue cracks. In this study, FE analysis was used to find the mechanism of high cycle fatigue crack in the HSDI diesel cylinder head. In order to improve the durability of HSDI diesel cylinder head, the modifications of cylinder head and head bolt pre-load were investigated. Experiments were performed to prove the existence of residual stress created during the heat treatment of cylinder head. The results of experiments showed that residual stress can affect the durability of HSDI diesel cylinder head.

The main role of the connecting rod in the engine is to deliver the firing load to the crankshaft. In order to carry out successfully the function, it is need to grasp the rotating crankshaft and also to keep the good stiffness of the big-end of the connecting rod in acceptable ranges during engine operation. When the stiffness of the big-end is needed to be reinforced, in general, some geometric dimensions are simply increased without consideration of their complex effects on deformation. Sometimes the reinforced geometry causes negative effects on the stiffness. This paper focuses on the effect of geometric parameters on stiffness in the big-end structure of connection rod by using Taguchi method. It is found that the side flange is the most influencing parameters. The FEA simulated results are compared with experiments.