Experimental Investigation on the Influence of Surface Defects on High-Speed Gear Performance

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The Ohio State University

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Gear tooth surfaces may contain undesirable defects for various reasons. One class of defects, surface scratches, are primarily related to manufacturing and assembly errors. The durability consequences of scratches have yet to be investigated. In this study, singular calibrated scratches varying in location and orientation are applied to the tooth surfaces of three otherwise high-quality, aerospace grade spur gears. These gears, along with a baseline undamaged control gear pair, are put through staged scuffing experiments that incrementally increased torque, operating speed, and bulk lubricant temperature at aerospace operating conditions. Gear coordinate measurements are performed initially to verify scratch location and that gear geometries and micro-geometries are within the specifications. Throughout testing, nondestructive metrology techniques involving microscope imaging and probe roughness traces are used at various sites along the scratch to track scratch-induced surface damage and changes in scratch geometry. All three gear pairs with scratched pinions are shown to experience scuffing failures in the early stages of tests in comparison to the scratch-free baseline gear. It is concluded that (i) surface scratches indeed impact the scuffing performance, (ii) the positive material generated during scratching has little influence on scuffing performance, and (iii) that there is no evidence of scratches healing or wearing away during operation.



geared transmission, gear contact durability, tribology