Ultrasonic Detection of Residual Stress Field of Barrel Inner Wall

Residual stress has a significant impact on the service performance of mechanical components, especially in terms of strength, fatigue life, and dimensional stability. It has long been a key difficulty to evaluate the residual stress state on the surface or at a certain depth of members in a rapid, nondestructive, and accurate manner. To address the problem, this paper explores the correlations of ultrasonic speed and direction with stress, and compares the sensitivity of different ultrasounds to stress, with the help of acoustic elasticity theory and ultrasonic nondestructive detection technology. The comparison shows the speed of the longitudinal wave propagating along the stress direction suffers the greatest influence from stress. Next, a residual stress ultrasound detection system was constructed: a critically refracted longitudinal wave (LcR wave) was excited by pitch-catch oblique incidence within a certain depth of the measured material, and the residual stress was derived from the variation of propagation time in a fixed propagation distance. On this basis, a curved acoustic wedge was designed for tubular members. Considering the stability of the coupling layer and the bottom echo, a precise propagation time measurement algorithm was proposed. Finally, ultrasound detection was carried out excellently on the self-compacting stress field of the inner wall of in-service tubular members. The research lays the foundation for applying the ultrasonic method to stress field detection of similar members.