Abstract:

In this paper, the thermoelastoplastic theory of plane strain was adopted to analyze the variations of stress and strain in the stretching-fixation milling process and to reveal the relationship between the initial strain and the residual stress. Then, a strain superposition model was proposed, which recognized the increase in residual compressive stress only when the stretching fixation produced positive initial strain. Moreover, the stretching-fixation milling of TC4 titanium alloy was performed at a milling speed of 38 - 566 m/min and an initial strain of 0 - 0. 003. Finally, the residual stresses on the machined surface were measured in the directions of 0, 30, 90 and 120 degrees from the stretching direction, respectively. Experimental results indicate that the variations of the residual stresses measured in the four directions are consistent with the initial elastic strains, thus demonstrating the correctness of the proposed strain superposition model.

Key words: titanium alloy, stretching-fixation milling, residual stress