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

摘要

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.