Residual stress nondestructive testing for pipe component based on ultrasonic method

Residual stress has significant impacts on the performance of the pipe components, especially on its strength, fatigue life and corrosion resistance and dimensional stability. It has been a difficulty and hot issue that how to evaluate the residual stress status of the surface or a certain depth of tube components quickly, non-destructively and accurately. Based on acoustoelasticsticity theory, the relationship between velocity and direction of ultrasonic propagation and stress is researched. The sensitivity of different types of ultrasonic to stress are compared, and it is found that velocity of longitudinal wave propagation along the stress direction is mostly affected by residual stress. Residual stress ultrasonic testing system for pipe components is built. Using one transmitting-one receiving and oblique incidence way excite critically refracted longitudinal wave (L_CR wave) in a certain depth (the depth which is related to the transducer frequency) in the material tested. Acoustic wedges for testing residual stress in pipe components are designed. Using tensile and compression testing machine calibrate the testing of axial residual stress. Adapt C style ring to calibrate the testing of circumferential residual stress. By testing residual stress nondestructively in pipe components in service condition, the accuracy and practicability of the ultrasonic method can be verified.