Gas turbine blades are important parts of a power plant, and thus, it is necessary to be able to predict the low-cycle fatigue life of the blades. In this study, a low-cycle fatigue test of In738LC, which is used primarily in gas turbine blade manufacture, was performed at various high temperatures (750oC, 800oC, and 850oC). From the test results, the stressstrain curve and the stress-strain hysteresis loop were obtained. It was established that In738LC has no strain hardening or softening. The life prediction equations for low-cycle fatigue were derived using the Coffin-Manson equation and the energy model. In conclusion, one equation for predicting the life low-cycle fatigue was obtained using the energy level with temperature as the varying factor.

The differential gear distributes the power from the transmission shaft to both wheel axles and automatically ensures rotational difference to maintain the speed difference between the two axles. However, when the vehicle travels on a slippery road surface, a slip in the wheel induces improper transmission of the driving force. Therefore, the limited slip differential limits the function of the differential gear by transmitting the driving force to the normal wheel without the slip. The hydraulic differential limiting device is based on the principle that the fluid between the inner and the outer rotors is compressed by the rotation of the trochoidal gear, and the compressed fluid moves to the cylinder to generate sufficient pressure in the side pinion gear to limit the differential. In this study, the pressure is predicted by variation in viscosity and rotational speed through flow analysis.

The hot curvature forming of large aluminum plates is a process used to produce spherical liquefied natural gas (LNG) tanks. In this study, we describe a method to determine the optimum shape of blanks to minimize the root gap in the forming process. The method proposed in this study was applied to a small-scale model for thick plates with a curvature of 1500 mm and thickness of 6 mm. First, the shape of the curved shells was determined as the target shape, and then a coordinate transform was used to determine the optimum blank shape, which was then iteratively modified using the results of finite element method (FEM) simulations, including heat transfer, until the shape error was minimized. Experiments in forming using Al5083 thick plate were carried out, showing that the method can determine the optimum blank shape within an allowable root gap of 0.1 mm.