For the hydraulic cylinder system of construction equipment to function normally, the hydraulic oil should not leak under high pressure, and the leakage begins with various seals of damage. The frictional heat caused by the reciprocating motion inside the cylinder increases the temperature of the oil, which affects the aging of the seal materials inside the cylinder, thereby accelerating seal damage. The purpose of this study is to confirm the effect of reducing heat generation by applying umbrellatype micro-dimples on the surface of a wear ring, and to find out the performance according to changes in shape and density of the dimples. Dimples were manufactured by injection molding and the core for injection was made by profile grinding processing. The structural safety of the wearing with dimples was examined by structural analysis, and the temperature changes of the dimple were measured during pin-on-disc friction experiments. It was confirmed that the dimple was effective in reducing the amount of heat generated, and the heat generation decreased as the size and density of the dimple increased.

Transportation machine manufacturers are putting in efforts on research based on weight reduction. One of the representative materials for weight reduction is Fiber Reinforced Plastic (FRP). Increased used of FRP, glass fiber and carbon fiber could be a way of weight reduction. It is almost unavoidable to generate holes or notches during structural design. Little research have been carried out based on cracks with respect to materials used for design. The utilization of finite element analysis and the reliability of the analysis methods are increasing in order to promptly cope with the damages in materials. In this study, Compact Tension (CT) model based on ASTM E647 was designed using SM45C, steel for structural use, short fiber Glass Fiber Reinforced Plastic (GFRP), and woven type Carbon Fiber Reinforced Plastic (CFRP). In addition, J-Integral, which is a factor for determination of growth of crack that appears in cracks, was applied to general structure analysis. J-Integral is an equation of the body force of the material and strain energy in accordance with the loading force, and illustrates the crack growth using energy release rate. J-Integral values of SM45C, short fiber GFRP and woven type CFRP were found to be approximately 74,978 mJ/mm², 7492.3 mJ/mm² and 6222.4 mJ/mm², respectively.