| The surface integrity produced by different machining procedures can significantly affect fatigue performance of workpiece, and surface roughness and residual stress are the important parameter of surface integrity. It is a good method to improve the fatigue life by getting enough compressive residual stress on the surface of the workpiece through machining. The forthgoers have proved in theory and practice that the pre-stretched machining was an efficient way to obtain compressive residual stresses on the surface of workpiece. In this paper, pre-stretched fixation is applied into HSM (high speed machining) to take the advantage of both pre-stretched machining and HSM, so that compressive residual stresses on the workpiece surface can be obtained. Ti- alloy is used as workpiece material , and FEA simulation and experiments are carried out.Firstly, it was discussed how the residual stress produces after machining. FEA software of ANSYS was used to simulate the generation process of the residual stress. Main factors which influence the generation and distribution of the residual stresses and how they work were analyzed.A pre-stretched fixture is designed and manufactured based on modification of hydraulic vice to obtain a uniformity stretched-stress in workpiece. With this fixture, a full factorial experiment of pre-stressed high speed flank milling of TC4 workpiece is performed. Strain gauge was used to measure the distortion of the workpiece. Milling parameters were changed to investigate their effect. In this paper, X-ray diffractometer was used to measure the residual stress on the workpiece surface machined by high speed milling under stretched fixation and surface roughness was also studied. Results of the measurement and the simulation were compared.It is shown that the residual stress in the machined surface can be controlled effectively, and ideal compressive stress can be obtained in the workpiece surface by means of milling under pre-stretched fixation. |
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