Ultrasonic Nondestructive Testing Technology Of The Distribution Of Residual Stress For Tiny Component

Tubules, bolts, small diameter screw, spline gear and other tiny components are widely used in daily life. Residual stress concentration phenomenon will be inevitably produced during the process of producing and using, and reduce the fatigue life of the components. In order to ensure the safety of these components, it is necessary to detect the residual stress in the key parts of the components.The existence of residual stress affects the propagation velocity of ultrasonic wave in the material. In the stress of solid material, the change of sound velocity can reflect the change of stress, and can be displayed through the detection of sound-timing. According to this rule, the size of the residual stress can be obtained by measuring the size of the acoustic time. In order to detect residual stress of tubule and spline gear, this paper proposes a detection method of residual stress of small components based on the critically refracted longitudinal. And the method is used the mode of one sending and one receiving through the residual variation in acoustic time. In order to detect the residual stress of the bolt, this paper proposes a detection method of residual stress based on the combination of shear wave and longitudinal wave. And the axial residual stress of the bolt and other components is detected by the mode of self-sending and self-receive by detecting the acoustic time of ultrasonic wave propagation.This paper has built two detection systems of residual stress, one is the mode of sending and receiving detection system of ultrasonic tubule and spline gear residual stress based on the critically refracted longitudinal and the other is the mode of self-sending and self-receive detection system of ultrasonic axial residual stress of bolts and small diameter screw based on the on the combination of shear wave and longitudinal wave.The influences of many factors on the residual stress measurement are analyzed in detail, including the incident angle, the component material, the thickness of the component, the distance of the sensor, the temperature, the curvature of the component, the surface roughness and the coupling agent. Through the analysis and experiments, the corresponding compensation technique is proposed to reduce the error and improve the accuracy of the detection results. And through the residual stress detection experiments of the tube and bolt, the feasibility of ultrasonic testing method is verified.