Journal of Failure Analysis and Prevention

, Volume 15, Issue 3, pp 441–444 | Cite as

Examination of a Helicopter Main Transmission Spiral Bevel Gear Fractures Due to Intergranular Attack and Fatigue

  • Aaron Slager
Technical Article---Peer-Reviewed


A gear tooth from a helicopter main transmission spiral bevel gear fractured as a result of fatigue that originated from the drive side root radius. However, this fatigue fracture was secondary. The primary fatigue fracture originated adjacent to the fractured tooth at a bolt hole location that attached the spiral bevel gear to a gear shaft. Intergranular features were observed at the primary fatigue origin, which resulted from residual stress induced by abusive machining and a subsequent chemical treatment during manufacturing.


Gear tooth fracture Fatigue Intergranular Chemical attack Residual stress 


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Copyright information

© ASM International 2015

Authors and Affiliations

  1. 1.Bell HelicopterHurstUSA

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