繰り返し摺動発熱による二輪車用ブレーキディスクに設けられた小孔からのき裂発生について(機械要素,潤滑,工作,生産管理など)

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Dissimilarly to brake discs for trains and automobiles, several tens of small holes are opened in the brake discs for motorcycles for ventilation and cleaning the pad surfaces. When an extreme braking torque is cyclically applied to the disc, some tinny cracks occur from several holes. In this study, durability tests under extreme braking conditions were conducted on the dynamometer to observe the crack initiation process in detail. A coupled analysis between heat transfer and thermal stress was also performed by using the general nonlinear 3D FE program. It was found from the durability tests that the surface hardness of the disc decreased since the disc was subjected to the tempering effect due to braking heat. Decrease in hardness makes the disc material weak. Consequently, the thermal stress cyclically exceeded the critical stress causing the cracks around the holes and driving them greater. The stress-strain history of the disc material at the point where a crack initiated, was successively calculated considering the material softening for the brake disc while the decrease in material strength of the brake disc was taken into account for the FE analysis. These results indicated that tensile stress occurred around the holes and fluctuated in correspondence with the heat cycle. Then, cracks initiated and growing around the small holes, were due to cyclic thermal stress in tension, namely thermal fatigue in conjunction with the decrease of yield stress and hardness of the disc material due to heat accumulation.
社団法人日本機械学会の論文
2007-03-25

繰り返し摺動発熱による二輪車用ブレーキディスクに設けられた小孔からのき裂発生について(機械要素,潤滑,工作,生産管理など)

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