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In motorcycles, the materials of frame have been switched from steel to aluminum for the purpose of reducing weight while improving the rigidity of chassis. It was made possible to use aluminum frames for a number of commodity categories, by the development of technology through new structural designs to make the most of the characteristics of aluminum, the advancement of computer simulation system and the progress in material and production engineering. As the result of adopting aluminum for the frame, much higher performance has been realized by achieving a 40% reduction in the developed frames consisting of extrusions and castings for sports-oriented motorcycles and by suppressing the increase in fuel consumption. For low-priced utility vehicles such as scooters, the manufacturing process has been simplified by the development of the die cast two-split module frame.

When using aluminum for vehicle body parts to reduce weight, the high pressure die casting (HPDC) is widely applied due to its adaptability to thin-wall products, near-net-shape castability, and short casting cycle time. Since a hollow construction is advantageous to increase stiffness of body parts, there has been a need of development of techniques for casting of hollow parts by HPDC. So far, hollow casting by HPDC has been realized for small parts using sand cores. When applying that method to large parts, however, it is necessary to increase filling speed. When the filling speed is increased, the core tends to break. In this project, we have developed a method to estimate changes of pressure distribution when filling molten metal by the casting simulation in order to analyze damages to the core. Through the analysis, we discovered occurrence of impulsive pressure waves.