Experiment Research On Surface Enhancement Of Ultrasonic Impact Treatment With Spinning Pin Array

Ultrasonic shot peening(USP) technology is a new type of surface strengthening which is more efficient, environment cleaning and energy saving than traditional mechanical shot peening. It is of smaller size with more flexibility. Ultrasonic shot peening, which can eliminate harmful tensile stress on the surface of the part and introduce beneficial compress stress, is able to improve the fatigue resistance, hardness and grain refinement of workpiece.Ultrasonic impact treatment(UIT), which modifies the shot medium from spherical to cylindrical pins with certain shape is a transformation of ultrasonic shot peening. It can treat the workpiece from different degrees with more flexibility and is simple and efficient without projectile reloading. However, the existing UIT equipment can not obtain the 100%coverage rate unless after multiple processing due to its fixed single pinor multiple pin arrays.To surmount disadvantages referred to above, this paper present the ultrasonic impact treatment with spinning pins. It mainly combines the ultrasonic impact system with servo motor to improve its manner of working. The equipment realizes high efficient processing. The main research content as follows:1. Basing on research of traditional wave theory and designing method of ultrasonic horn, spline curve ultrasonic horn with large amplification factor and form coefficient is designed using the optimal design method of finite element software ANSYS. The new type of ultrasonic realizes experimental requirements. The node point of new type of ultrasonic horn is designed using ADPL optical design method of finite element software ANSYS. Experiment result shows that ultrasonic horn designed is suitable and reliable.2. Mechanism of ultrasonic impact treatment is analyzed basing on elastic-plastic mechanics, contact mechanics and dynamic plastic mechanics. The distribution of residual compression stress under condition of certain parameters is derived. The result of residual stress is close to finite element simulation value. The impact force of theoretical analysis is very close to experimental result.3. The principle of beneficial effect on coverage rate of ultrasonic impact treatment with spinning pin array device is analyzed. The deviceis designed and manufactured basing on theory above. The pin array spins while impacting the moving workpiece with certain speed.4. Ultrasonic impact force measurement system is established and the impact force under condition of different impact distances is measured. The experiment result shows that impact force increases with decrease of impact distance. And experimental value of impact force agrees with theoretical value and simulation value when impact distance is 1mm. Orthogonal experiment was carried out with different moving speed and motor speed. Roughness and hardness of workpiece are measured after ultrasonic impact treatment. The experiment results show that the maximum hardness increase is 24%, hardness of workpiece increases with decrease of moving speed.5.Process of impact action of spinning pin arrays is simulated under condition of different rotational speed and moving speed. The influence of moving speed and spinning speed on residual compress stress and coverage rate is analyzed.