Effect of Case Depth on Fatigue Strength of Case-hardened Gear

Abstract

In order to elucidate the effect of case depth on fatigue strength and failure of case-hardened gears, fatigue tests were performed using a power circulating gear testing machine. Case-hardened gears with three different case depths including an optimum case depth for surface durability which was determined by a calculating method derived from roller tests were used in the tests. It was revealed that the type of tooth breakage caused by bending fatigue or surface fatigue depended upon the case depth and that the above mentioned calculating of optimum case depth was valid also in gear design.