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ADC12 is one of the common aluminum alloys for automobiles because it has suitable for casting and machining. However, the corrosion resistance of ADC12 is insufficient in comparison with other aluminum alloys. The corrosion depends on chemical composition of aluminum and circumstance around aluminum. It was considered that a crevice such as a seal gap accelerates corrosion rate. Therefore, the corrosion at a sealing gap between ADC12 and rubber gasket was investigated. Salt water corrosion tests were carried out with an o-ring compressed between ADC12 plate and plastic plate. Corrosion depth and corrosion area at sealing surface were measured with a microscope. The corrosion depth at the sealing surface was deeper than that outside it. Since smooth surface of aluminum prevented the sealing surface from corrosion, it was considered that the narrow sealing gap enabled to decrease in the corrosion rate.

To create a society based on hydrogen energy in the near future, it is necessary to clarify the influence of hydrogen on the mechanical, physical and chemical properties of the materials used for hydrogen energy systems. The rubber O-rings used in the high-pressure sometimes suffer from the decrease in durability due to decompression failure, which is influenced by several factors. From this viewpoint, sensitive factors for the durability of rubber O-rings were evaluated by using a L18 orthogonal array. A high-pressure durability tester, which enables the rubber O-rings to expose repeatedly high-pressure hydrogen gas at arbitrary test conditions, was employed.

The flow behavior of rubber compounds inside a mold is very complicated including various phenomena such as heat transfer from the mold, wall slip and swell at the divergent cavity. A slit rheometer which can measure the flow behavior inside a mold during curing was developed. The rheometer has a window which enables the observation of the flow behavior directly under 50 MPa. The pressure loss gradient along the flow direction and shear viscosity were found to be independent on the degree of cure but wall slip was observed. The wall slip phenomena could not be explained by slip analysis, because plug flow occurred due to little effects of the poiseuille flow. The pressure behavior inside the slit could be well predicted by using the equation obtained by assuming stress relaxation of visoelastic fluid occurs without share along the wall. The stress relaxation phenomena were predicted by taking into account the short and log relaxation time.

NBR (acrylonitrile butadiene rubber) has been used for the oil seal equipped on a power steering. However, lack of heat resistance was occasionally observed for NBR, with the recent trend of customer's demand for increasing the life of oil seals in high temperature environmental condition. We developed an oil seal with H-NBR material, which could exhibit the superior performance in the heat resistance; however, it had a weak point in low temperature environment. We have developed HNBR1, the new H-NBR, which has been improved in the performance for low temperature [1]. HNBR1 has been applied for power steering seals as the rubber material, which has superior heat resistance, cold resistance and oil resistance.

Regarding the polyester thermoplastic Elastomer (TPEE) boot used in a Constant Velocity joint(CVJ), it is effective to adopt soft and low frictional coefficient (μ) TPEE material which achieves compact size, low frictional noise and easy assembling. However, in the conventional low hardness TPEE, both grease resistance and heat resistance deteriorate, so it was necessary to improve the structure of TPEE polymers. We developed the new soft TPEE CVJ boot, focusing on the improvement method of TPEE polymers and design factors to achieve the compact and low frictional noise boot.

In a diaphragm used for an accumulator, the relationship between design factors and durability in low temperature is discussed from the occurrence of buckling phenomenon through the observation results. The durability of the diaphragm which has a sandwich structure of rubber and resin films, is greatly influenced by the buckling phenomenon which occurs during deformation of the diaphragm when used for an accumulator in low temperature condition.

The characteristics of the elastomer material and the fiber cloth reinforcing material have been analyzed as related to diaphragm durability. Investigated were diaphragms used for waste gate actuators for controlling the boost pressure of turbochargers. In this presentation, the authors verify the importance of the elastomer material fatigue resistance under high temperatures and the elongation properties, including directional properties of the fiber cloth reinforcing material for the durability of the diaphragms.

Upgrading of the performance and the durability of bellow boots used to seal constant-velocity joints are essential to seet the demand for higher performance and longer life automobiles. In this discussion about bellows boots for sealing constant-velocity joints, examples and analysis results of bench tests for studying wear and fatigue durability are presented.