Study On The Improvement Of Ultrasonic Strengthening Device Based On Giant Magnetostrictive Transducer

As a new technology, ultrasonic vibration enhancement has a special advantage over improving the surface quality of machined parts. Compared with surface rolling strengthening and shot peening which bear some disadvantages like shallow strengthening layer, low hardness of components and low size accuracy respectively, ultrasonic enhancement can better improve the surface quality. As a core component of ultrasonic enhancement system, transducer has been a key factor determining the performance of ultrasonic enhancement process.The present thesis attempts to conduct a research on the principle of ultrasonic enhancement and the characteristics of Giant Magnetostrictive Material (GMM) so as to provide a theoretical foundation for designing and developing Giant Magnetostrictive transducer. It then makes a detailed analysis of the dynamic output characteristics of transducer and design calculation of its structure size will also be done according to the technical requirements of ultrasonic enhancement aiming to develop and improve giant magnetostrictive transducer prototype and the ultrasonic power.Through the theoretical analysis of magnetic field of giant magnetostrictive transducer, a distribution model of magnetic field will be created. It will then conduct a simulation analysis of its magnetic field by ANSYS finite element analysis so as to validate the rationality of structure design and optimize the structure of giant magnetostrictive transducer.The thesis then creates an experimental platform testing hysteresis losses in order to calculate all the transducer losses including eddy current losses, hysteresis losses and resistance losses. Through the above analysis, the thesis proposes approaches to reduce energy losses. It is quite difficult to test the internal temperature of the transducer by using conventional methods. The present thesis adopts finite element analysis to simulate the temperature field of transducer and the actual temperature distribution shows that the maximum internal temperature rise is 71℃ which can satisfy the needs of long-time ultrasonic enhancement.After testing, it is found that the maximum output amplitude of the transducer reaches 253μm and the output of the transducer shows greater stability. The bias magnetic field designed in the present thesis meets the requirements of eliminating frequency-doubling effect under different frequencies. The orthogonal test of three factors at three different levels is designed to probe into the influence of the three parameters such as extrusion, feeding rate and rotating speed of workpiece on ultrasonic enhancement. It is found that the most significant factors affecting the surface roughness and hardness are feeding rate and extrusion respectively. Through the ultrasonic enhancement process, the surface roughness decreases by 80% and the hardness increases by 28.5%.