A failed spiral gear and pinion set made from 4320H Ni-Cr-Mo alloy steel operating in a high-speed electric traction motor gear unit driving a rapid transit train were submitted for analysis. The pinion was intact, but the gear had broken into two sections that resulted when two fractured areas went through the body of the gear. Wheel mileage of the assembly was 34,000 miles at the time of failure. All physical and metallurgical characteristics were well within specified standards, and both parts should have withstood normal loading conditions. The primary mode of failure was tooth bending fatigue of the...
Lester E. Alban, Tooth Bending Fatigue Failure of a Spiral Bevel Gear, ASM Failure Analysis Case Histories: Rail and Rolling Stock, ASM International, 2019, https://doi.org/10.31399/asm.fach.rail.c9001496
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