Impact defects are generally caused by heavy loads caused by rough handling. It usually occurs at or near the root of tooth, and the broken surface is gray granular, without the trace of defect development process.
As shown in the figure, the tooth angle of carburized gear is broken and broken. Before breaking, the tooth angle is repeatedly impacted, leaving many characteristics of surface fracture. It’s mostly due to improper shifting.
The hardened gear as shown in the figure is a typical impact defect with gray granular appearance on the section. It has no characteristic of smooth appearance of fatigue fracture. Most of the defects are caused by more than proper clutch operation or improper shifting.