Paper Title:

Failure Analysis of a Herringbone Gear

Periodical Key Engineering Materials (Volumes 462 - 463)
Main Theme Fracture and Strength of Solids VII
Edited by Ahmad Kamal Ariffin, Shahrum Abdullah, Aidy Ali, Andanastuti Muchtar, Mariyam Jameelah Ghazali and Zainuddin Sajuri
Pages 366-371
DOI 10.4028/www.scientific.net/KEM.462-463.366
Citation Samroeng Netpu et al., 2011, Key Engineering Materials, 462-463, 366
Online since January, 2011
Authors Samroeng Netpu, Panya Srichandr
Keywords Failure Analysis, Fracture, Gearbox Failure, Herringbone Gear Failure, Manufacturing Defect
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Herringbone gears are extensively used in numerous engineering applications including gearboxes. Premature failures of such gears could lead to many serious consequences such as process downtime and late delivery which are critically important in this day and age of intense competition. This paper reports the results of failure investigation of a herringbone gear in a reduction gearbox used in a hot rolling steel re-bar mill in Thailand. The gear fractured after only 24 hours of service. The fractured gear was inspected visually and macroscopically, and all critical dimensions were measured. Chemical compositions of the materials were analysed. Fracture surfaces and microstructure of gear material were examined, and microhardness measured. Stress analysis was performed using finite element methodology. It was found that the premature failure of the gear, which appeared as a longitudinal crack, was due to excessive stress. The crack originated at the root of the keyway. Careful examination revealed that there was a slight misalignment between the key and the keyway which resulted in excessive stress. The lesson learned from this failure is that manufacturing defects, however slight, could lead to premature failures of key components such as gears, and could be very costly. It is recommended that apart from proper designs of components, good manufacturing practices are also necessary to minimize the chance of premature failures.

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