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ASM Failure Analysis Case Histories

ASM Failure Analysis Case Histories: Rail and Rolling Stock

ASM International
ISBN electronic:
978-1-62708-231-0
Publication date:
2019
Book Chapter

Tooth Bending Fatigue Failure of a Spiral Bevel Gear

By
Lester E. Alban
Lester E. Alban
Metallurgical Engineer, Fairfield Manufacturing Company, Inc., Subsidiary of Rexnord, Inc.
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Published:
2019

Abstract

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 gear from the reverse direction near the toe end. The cause of failure was a crossed-over tooth bearing condition that placed loads at the heel end when going forward and at the toe end when going in reverse. The condition was too consistent to be a deflection under load; therefore, it most likely was permanent misalignment within the assembly.

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Lester E. Alban, 2019. "Tooth Bending Fatigue Failure of a Spiral Bevel Gear", ASM Failure Analysis Case Histories: Rail and Rolling Stock

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