BASIC STUDIES ON SCORING OF SPUR GEARS : 2ND REPORT, EXPERIMENTAL RESULTS USING POWER CIRCULATING GEAR TEST RIG

Abstract

The authors previously cleared from the experimental results which are derived from the four-ball test and the roller test that the condition or scoring could be anticipated by the surface temperature rise, and discussed how the thermal conductivity in the surface layer of material affects the surface temperature rise. In this report, the effects of the following factors on scoring are discussed ; the material and the hardness of gear, the viscosity of lubricant and the surface roughness of gear tooth. The results for scoring test are summarized as follows ; on both the normalized gears and the hardened gears, the progress of wear is especially remarkable in the zone of single pair of contact and the tendency of the increase of wear depth on the tooth surface well coincides with that of the weight loss due to wear. When the scoring failure of the hardened gear is compared with that of the normalized gear, the scar of the hardened gear tooth looks like a number of the micro fragments of the welding material gathered, and the size of the wear particles of the hardened gear is smaller than that of the normalized gear. As the thermal conductivity fall, the scoring limit decreases. Though the effect of the hardness on the scoring limit is larger than that of the thermal conductivity, the influence of the hardness of gear is inseparable from the scoring limit because the thermal conductivity and the hardness interact each other. Lastly, as the viscosity of lubricant grows higher, the scoring limit increases. In the lubricating condition of 140-Turbine oil, the index values of the flash surface temperature in AGMA Standard which were calculated by the measurement value of the surface roughness after running in, are within 161172°C on the carburized gear which consists of SCM22H material, and the mean value of the flash temperature is about 168°C.