Ultrasonic Testing Of Surface Residual Stress Of 20CrMnTi Carburizing Quenching Gear

Gear is one of the parts that is subjected to alternating fatigue load, which surface quality is very important. The distribution of residual stress on the surface has a great influence on the fatigue strength, and the disadvantage of the stress distribution will cause the fatigue failure of the gear. This paper takes 20 CrMnTi carburizing quenching gear as research object, trying to study on the distribution law of residual stress on gear surface by Critically Refracted Longitudinal Wave method, and to provide the basis for surface quality detection of transmission components with special structure.Designing LCR wave probe in this paper, and verifying the accuracy and reliability of the design plan by CIVA simulation and experiment. This paper systematically studies the characteristics of LCR wave, the law of attenuation and penetration depth, and the influence of incident angle on LCR wave. Designing and building the testing system of gear surface residual stress, including the probe design, development of hardware system and software system. Establishing the experimental scheme for the calibration of ultrasonic stress coefficient and obtaining the stress coefficient of gear. Detecting the distribution of residual stress on the surface of 20 CrMn Ti carburizing quenching gear by partition method, and analyzing the influences. Verifying the rationality of the residual stress on the gear surface by the X-ray diffraction method.Research shows that the LCR wave probe designed in this paper has good accuracy and reliability, simulation and experiment are consistent with the theory. The change of propagation time is approximately linear with the change of stress in the direction of propagation of LCR wave. The residual surface stress of the measured whole 20 CrMnTi carburizing quenching gear is mainly compressive stress, which uniforms distribution theory, and meets the general requirements of gear preparation. The residual stress caused by local stress concentration is relatively large. The thin and mild abrasion of the carburizing layer leads to the existence of residual tensile stress in the surface. The root surface of the tested gear is quenched and hardened, and the bending fatigue property of the gear is improved. The external factors such as coupling condition and temperature have a certain effect on the test results. The rationality of the results of the residual stress on the gear surface by ultrasonic testing method is verified by X-ray diffraction method in the qualitative analysis.In this paper, the design of the gear stress detection method and theory has a good feasibility, the research results provide reference for nondestructive and efficient quality inspection of gear surface.