Research On Ultrasonic Assisted Forming System And Ultrasonic Assisted Compression Test

As modern science and technologies advanced,the increasing need of micro parts in high-tech products has posed a great challenge before the manufacturing technology.Micro forming technology,which is known for its high manufacturing efficiency,plays an important role in the mass production of micro parts.Nevertheless,the size effect that emerges as the workpiece size shrinks from macro scale to micro scale in micro forming process,needs newly developed process and equipment.By applying ultrasonic vibration to forming process,the forming force as well as the interfacial frictional force can be lowered,which can improve micro forming process to a certain degree.However,the mechanism of ultrasonic vibration during forming process is still unclear,thus no general scientific theory can be adopted in the process of engineering practice.In order to solve the problem described above,this paper conducted researches on the ultrasonic assisted forming process on the basis of developed ultrasonic assisted forming system.Firstly,the need of ultrasonic assisted forming process was analyzed,and key designing points and main parameters were determined.The mechanical structure of the forming system was designed and the finite element method(FEM)model was then developed to analyze its static characteristics under external load.By analyzing the mechanical structural modes and amplification coefficient with FEM software,the booster was designed and optimized.The control system was designed and host control software was programmed with Visual Basic,which provides the functionality of overall system control.By measuring the relevant static and dynamic responses of the system,the forming capability under high frequency vibrational conditions was verified.Ultrasonic assisted compression tests of pure copper specimens were implemented.By applying ultrasonic vibration with different amplitudes for the same period of time during compression tests,the influence of ultrasonic amplitudes on compression tests were investigated,the results of which showed that the forming force reduction is positive relevant to the ultrasonic amplitude.By respectively applying ultrasonic with amplitude of 50%P for different periods of time,the influence of ultrasonic applying time was investigated,the results of which showed that longer application of ultrasonic doesn't change the forming force reduction significantly.By measuring the change of the shape and the surface roughness,the influence of ultrasonic vibration on compression test was analyzed,and the results showed that specimen end surface underwent abnormal shape change when ultrasonic amplitude is larger than 60%P,and that the surface quality was optimal at 45%P?50%P range.Simulation of ultrasonic assisted compression test was carried out.By incorporating the experimental data of compression test without ultrasonic vibration,the elastic model of upper mold was established,and the interfacial frictional coefficient and plastic parameters were computed by data fitting approach.Compression tests with different ultrasonic amplitudes and different frequency were simulated relevant forming force and deformation data were extracted.By comparing the forming force and deformation change under different conditions,the reason for the forming force reduction was investigated,and the law of influence of vibration energy absorbed by elastic mold under high frequency conditions on the acoustic softening during ultrasonic assisted compression test was uncovered.