Abstract: Gear has been widely used in each field, such as equipment manufacturing, due to its important role in mechanical transmission. With the development of defense industry, the higher performance requirements of gears, such as fatigue life, transmission efficiency and reliability, are raised. Gear always fails in its service life. The fatigue pitting and fatigue crack are two main fatigue failure modes of gear. The two fatigue failure modes seriously influence the transmission performance and reliability. The residual stress is one of the main factors of fatigue failure. The traditional methods are difficult to measure the residual stress accurately and fast due to the complex shape of gear and the limited space. A new method is proposed to measure the gear residual stress by using L_CR. Propagation laws of critically refracted longitudinal wave on the tooth surface and near the tooth root are studied, and a special transducer and an automatic detection device for measuring the residual stress are designed. The experimental results indicate that the residual stress of gear can be measured accurately and fast with L_CR.

Key words: manufacturing technology and equipment, non-destructive testing, residual stress, ultrasonic, gear