Study On The Effect Of Cushion In Hydro-Mechanical Bending Of Thin-Walled Tube

With the development of advanced manufacturing technology of plastic processings in recent years, there are higher demands for the tube forming and srtuture lightweight of parts in industries of aerospace, automobile etc. Thin-walled Aluminum alloy tube plays an increasingly important role in those industries and thus hydro-mechanical bending is proposed in such a context. Hydro-mechanical bending of thin-walled tube is a brand-new subject, but it still has some defects, in light of which, this paper proposes that the forming deficiencies can be overcome by using cushion.Based on the hydro-mechanical bending, hydro-mechanical bending of thin-walled tube with cushion is a forming scheme in which a cushion is put between the tube and the die so that the technology of hydro-mechanical bending of thin-walled tube can be optimized. Through the finite element analysis and experimental research, the paper obtains the law how the cushion affects the forming of hydro-mechanical bending of thin-walled tube, which provides theoretical foundation for the optimization of this technology.The paper conducts a finite element simulation of hydro-mechanical bending of 5A02 aluminum alloy tube with cushion, which is carried out by using a set of device with one cushion on the tube and the other under the tube. Then the paper analyzes the defects of the tube forming, including wrinkling, section distortion and wall thinning, and studies the effect of cushion's performance parameters, such as friction coefficient, hardness, indentation depth as well as the geometric shape and size of the cushion, on the forming deficiencies. The paper points out that with the increase of friction coefficient and indentation depth, the degree of outwall thinning will decrease; the lower hardness of the cushion is, the lower the degree of section distortion is.Then the paper illustrates mechanism of the cushion used in hydro-mechanical bending and notes the role of the cushion in overcoming the forming deficiencies of 5A02 aluminum alloy tube.Finally, hydro-mechanical bending experiment of 5A02 aluminum alloy tube with cushion is carried out, in which the same set of device as that used in simulation is adopted. Based on the experiment, the paper studies the effects of cushion's parameters on tube bending and compares the experiment results with that of simulation, with a conclusion that the two results are similar. Compared with hydro- mechanical bending without cushion, the paper concludes that with cushion, the quality of bending forming can be greatly improved.