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The performance of a large diesel engine piston has been investigated to determine a mechanism for the failures encountered during engine research testing. During engine testing, it was found that the pistons were failing to retain the ring groove insert and fracture of the top land above the insert was observed. The finite element analysis was performed on the piston to ascertain the combined thermal and mechanical stresses on the piston and its ring groove insert. Finite element models were employed to study the effects of a crack growing in the Alfin bond between the ring groove insert and the aluminum alloy of the piston. The data showed that as a crack in the bond between the ring groove insert and the aluminum alloy of the piston grows, the stresses in the bond area drastically increase.

During engine durability testing of a large diesel engine, several pistons were found to have experienced fatigue cracks along the combustion bowl edge directly over the pin bores. In order to determine the optimum design solution to this piston combustion bowl edge cracking problem, the performance of several power cylinder assemblies have been investigated to determine their effects on piston combustion bowl edge stresses. The power cylinder design variables examined in this analysis were piston skirt section thickness, piston compression height, pin inner and outer diameters and connecting rod end designs (Tee-Pee vs. straight). A finite element analysis of each power cylinder assembly was performed to ascertain the stresses existing on the piston combustion bowl edge. This finite element analysis found combustion bowl edge stresses from the thermal expansion effects only loading as well as those from the combined thermal expansion and combustion pressure loading.