Ultrasonic Testing And Calibration Technique For Residual Stress Of Gear Root

Gear is the important component of the machinery equipment, which cantransmit the movement, change speed and direction of movement. Gear occurs residual stressin tooth root after machining and heat treatment inevitably. The existence of the residualstress is the main cause of the failure of gear tooth. The traditional methods are difficult tomeasure residual stress in the tooth root accurately and fast due to the complexity of the shapein the gear root. This paper proposed tooth root residual stress testing method based on theultrasonic LCRfirstly.The basic principle of LCRmeasuring residual stress is researched. The relationshipbetween the stress variation and the time variation is derived in the uniaxial stress material.LCRis most sensitive wave to the residual stress whose direction parallels the direction ofpropagation through theoretical derivation.This paper built a set of automated testing system used the detection of tooth rootresidual stress based on ultrasonic and proposed a calibration method of residual stressultrasonic testing system. Automated testing system mainly includes the motor, gearholding mechanism, screw feeding mechanism, sensor holding mechanism, sensors,ultrasonic stress testing system. Ultrasonic stress testing system interface used VC++/MFC.The calculation of the residual stress used the lagrange interpolation algorithm, the cross-correlation algorithm. Calibration system mainly includes the tensile testing machine,amplifier, acquisition card, ultrasonic stress testing system. Calibration system interface usedMATLAB/GUI. Detection system is qualified by comparing standard stress value to theultrasonic stress value.The tooth root residual stress is measured through the combination of the specific sensor,automatic detection device, ultrasonic stress testing system. The feasibility and stability ofthe ultrasonic testing system is proved by real-time monitoring and repeated measurement.The influence factors of the measurement, which include the material, the thickness, the angleof incidence, the temperature, the curvature of structures, surface roughness and the couplant,are analyzed. Compensation techniques are used to improve the accuracy of measurementresults.