One end of an axle shaft containing the integral spur pinion was submitted for examination, along with the report of a tooth pitting failure. The spur pinion, integral to the axle shaft, operated in a medium-size, off-highway truck at an open-pit mine, for “a relatively short time.” Only the pinion head had been returned. The shaft portion had been torch-cut away. Chemical analysis along with the microstructure confirmed the specified material was SAE 43BV12 Ni-Cr-Mo alloy steel. The mode of failure was surface contact fatigue through the shear plane subsurface at the lowest point of single-tooth contact. The cause of failure was tooth-tip interference from the mating gear teeth. Because the mating parts within the assembly had not been returned or examined, unanswered questions remained.
Lester E. Alban, Contact Fatigue Failure of an Axle Shaft Spur Pinion, ASM Failure Analysis Case Histories: Automobiles and Trucks, ASM International, 2019, https://doi.org/10.31399/asm.fach.auto.c9001498
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