Study on Load Bearing Capacity of Gears in Special Environment

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The impact and bending fatigue strengths of case-hardened gears with various case depths at low temperature (-60ﾟC) were investigated. For this experiment were used gear impact testing equipment and a gear bending fatigue testing machine of hydraulic loading type with a cooling chamber. The impact and bending fatigue strength of case hardened gears at room and low temperature, and the effects of case depths on these strengths were clarified considerably.The friction and wear characteristics of gears in vacuum were also investigated. The gear testing machine of power circulating type with a vacuum chamber was developed, in which the coefficient of friction between the contacting tooth surfaces, and the temperatures of the gear teeth and the shaft can be measured under various running conditions. The running tests for S45C, MoS_2 coated SUS440C, Duracon and Nylon gears were carried out in air and vacuum environment by using the gear testing machine, and the coefficient of friction betwee … More n the contacting tooth surfaces, the wear of the gear teeth and temperature changes of the gear teeth, the shaft, etc. were measured. On the basis of these results, the friction and wear characteristics of gears in vacuum were clarified to a considerable extent.The main results obtained from this investigation are summarized as follows.1. The bending fatigue strength of case-hardened gears at low temperature (- 60ﾟC) is larger than that at room temperature, but the impact strength at low temperature is smaller.2. The optimum case depth exists for the bending fatigue strength of case-hardened gears at low and room temperatures. The impact strength decreased with an increasing case depth.3. The coefficient of friction of S45C gears in vacuum is larger that in air, but those of MoS_2 coated SUS440C, Duracon and Nylon gears in vacuum are almost equal to those in air.Thus the load bearing capacity of gears at low temperature and in vacuum was clarified, and the useful data for the design of gears in special environment were obtained from this investigation. Less