Experimental Study On The Influence Of Technological Parameter On The Result Of Ultrasonic Vibratory Stress Relief

In the process of actual production, the surface and inside of metal parts will exist residual stress after the hot working or pressure processing. The existence of the residual stress in the artifacts in the unstable state, is the main reason for cracks or deformation. In order to eliminate the residual stress of workpiece, there are three kinds of methods which are natural stress relief (NSR), thermal stress relief (TSR) and vibratory stress relief (VSR). And the vibratory stress relief (VSR) has many advantages, such as low energy consumption, higher efficiency and low cost, and is quickly replace the natural stress relief (NSR) and thermal stress relief (TSR).The present study about vibration stress relief (VSR) focus on the frequency less than200Hz. For small workpieces, their inherent frequency is very high (generally above15KHz).When the workpieces’ resonance frequency beyond the range of low frequency vibrator, the vibration stress relief (VSR) is not effective on treatment of small workpieces. The vibration frequency of ultrasonic vibratory stress relief is generally above15KHz, so ultrasonic vibratory stress relief treatment of small parts can be achieved. The amplitude of ultrasonic vibratory stress relief is very small and the workpieces not easy generates fatigue damage and dimension stability is also better. But study on ultrasonic vibration aging is still in its infancy, the mechanism of eliminating stress remains unclear and the choice of process parameters no unified standard.The purpose of this study is combined with the mechanism of ultrasonic vibratory stress relief eliminate residual stress of the metal, then carry on experimental feasibility analysis of the experiment according to ultrasonic vibration stress relief principle. Finally, carry on the experimental analysis of the effect of ultrasonic vibratory stress relief. For the theoretical and experimental research on the ultrasonic vibratory stress relief and promotion play a reference role. The main content of this paper is as follows:(1)The choice of ultrasonic vibratory stress relief parametersIn the practical application of ultrasonic vibratory stress relief and experiments, many parameters influencing the process, some important parameters are:the vibration amplitude, vibration frequency and vibration time and vibration control nodes, etc. This paper experiments of the choice of excitation amplitude and excitation frequency of system analysis, and different vibration time of ultrasonic vibratory stress relief treatment workpiece. Experimental results show that ultrasonic vibratory stress relief along with the increase of the processing time for a period of time, to eliminate the residual stress also increased. However, ultrasonic vibratory stress relief system to provide the maximum vibration amplitude is certain, that is the maximum vibration stress must, when vibration superposition of stress and residual stress of the largest fails to reach the yield limit of material, even increase vibration time can’t eliminate residual stress.(2) Research on Elastic-plastic lateral bending theoryThis topic the elastic-plastic lateral bending theory is first used in the study of the theory of ultrasonic vibratory stress relief. Using the theory of elastic-plastic lateral bending on the calculation of residual stress in the bar, can choose for ultrasonic vibration aging experiments of ultrasonic generator and ultrasonic transducer, and for the design of ultrasonic provide numerical basis, such as the amplitude of ultrasonic vibration stress calculation of the ultrasonic vibration aging experiments of bar can be determined the range of a concentrated load. It provides certain guiding role for ultrasonic vibratory stress relief after theoretical and experimental research.(3) Measurement of residual stress in the exploration of new methodsThis topic combined with elastic-plastic lateral bending residual curvature theory proposed the new method for calculating residual stress. During the experiment using the press in the middle of the test bar on concentrated load, make its produce elastic-plastic deformation, to simulate the practical production process in the formation of residual stress of metal components. In experimental analysis, using large tool microscope measuring the maximum deflection of bending bar and then in the ultrasonic vibration device for ultrasonic vibratory stress relief treatment, to bar measuring maximum deflection value after treatment, and calculate the residual curvature. Finally, the topic use the residual curvature to calculate residual stress for analyzing the experimental result.