The Ultrasoni Technical Research Of Metal Material’s Residual Stress

The processing property and the service performance of metal components are closely related to the internal residual stress of the metal material. During the using and processing of metal components, the deformation, cracking, brittle fracture or fatigue damage are all closely related to the internal residual stress of the metal material. So it has important practical significance to reduce operating risk devices, to ensure the reliability of material use, and to study on structural integrity for characterization of residual stress, especially the qualitative and quantitative determination for complex distribution of residual stress in welded joint.The propagation velocity of ultrasonic wave is related to elastic properties while spreading in elastic metal polycrystalline, but the presence of residual stress and microstructure of material will affect the elastic properties. With the development of science and industry, ultrasonic velocity can be accurately obtained. By studying a large numbers of literatures, it chooses a kind of ultrasonic measurement, which is the most effective. Based on the acoustic theory of elasticity, we will use the technology of ultrasonic wave to characteristic the change of residual stress around the relationship with the residual stress, the elastic properties of material and sound propagation velocity. However, the existing method and research still has many deficiencies, such as the measured stress in the mean stress of wave propagation direction, the sound material elasticity, the low precision of sound propagation in a short distance and ultrasonic measurement in the state of complex stress.To solve the above problems, the main content is the ultrasound measurement of residual stress of the metal material in complex state for the welded joints of Q345R steel. And by using the combination method of ultrasonic longitudinal and shear wave speed, we characteristic the absolute or relative value of residual stresses of two-dimensional direction. The amendments to the sound of the theory of elasticity formula are proposed by analyzing on different microstructure areas of the weld structures; for the accurately measure of short distance, we propose the "phase-frequency" method to measure the acoustic propagation time; by using the hot rolled steel plate as tested object, we verify the applicability of the method of using Ritec ultrasonic system and calculating velocity with "phase-frequency"...