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.

Displacement ductility and rotational ductility are used, to verify the performance of blast doors subjected to explosive loads. The values of these performance items are calculated by measuring the maximum elastic displacement in the laboratory, and the maximum displacement during the explosion test. To attain the maximum elastic displacement, the finite element analysis and the load distribution method are applied. In applying the load distribution method, the behavior of a blast door along a width direction is converted to a cantilever beam and along a height direction to a simply supported beam. The results by the load distribution method are verified by a finite element analysis and compared with those by a plate theory.

Micro-dimples on sliding surfaces have been investigated to reduce the frictional forces on metal bearing surfaces; however, for an elastomer, such as thermoplastic polyurethane (TPU), this has not been studied. The material properties of an elastomer are affected by temperature, and this can shorten the life of the elastomer. In this paper, micro-dimples were applied on the surface of an elastomer in order to reduce the frictional heating, which was experimentally investigated using pin-on-disk apparatus while the surface temperature was measured. To obtain optimal design parameters, the design of the experiment was applied, and the shape of the section, size, depth and density of micro-dimples were selected as the design parameters. The results show that the size of the dimple is the most important design parameter.

The roll forming process is commonly used for the conventional 'Fe' metal products such as a furniture drawer guide or an up-down slide guide. Recently its applications are variously expanded to the sanitary facilities or electronic devices. It is essentially required the cleanness for the high technology application and any corrosion or rust are not allowed. Therefore, in those applications the stainless steel materials are strongly demanded as the substitution of ‘Fe’ steel. However the mechanical properties of stainless steel are not suitable for forming process compared with those of ‘Fe’ steel. Up to now, the conventional F.E.M.(Finite Element Method) has been used to analyze and design the roll forming process. The purpose of this research is to obtain the proper production process and the shape of rolls to manufacture the high precision slide rails made of stainless steel material. The commercial program, SHARPE-RF, is used to analyze the entire roll forming process. The results show that the rolling process and the roll design by F.E.M. are useful from the good agreement between the shapes of products estimated by F.E.M. and those of the actual products.