| There are many advantages when use tailor-welded tube with dissimilar material andthickness to form reducerpipe,and in order to design tailor-welded tube reasonably, usingthe finite element analysis method to study the plastic deformation and the difference instress and strain states between thinner and thicker tubes during tailor-welded tubehydroforming, analysed the effect of different factors on the distribution of the thinningratio and the amount of weld-seam movement, optimized the structure of tailor-welded tubewith dissimilar material and thickness which based on orthogonal experiment at the sametime.The research results showed that the low intensity thicker tubes deformed firstlyduring the bulging process and the plastic deformation zone extended towards two endssimultaneously from the middle of thicker tubes. When changing the strength ratio, thedeformation order of thinner and thicker tubes and the moving direction of the weld-seammay be changed. Both stress states of thinner and thicker tubes were biaxial tensile stress,and both the hoop stress increased with the increase of the axial stress. The strain state inlongitudinal direction of thinner and thicker tubes, respectively, was compressive strain andtensile strain, but both hoop strains were tensile strain state, and the hoop strain of thinnertube increased with the decrease of the axial strain, while the hoop strain of thicker tubeincreased with the increase of the axial strain.The thickness distribution of forming parts which formed with tailor-welded tube withdissimilar material and thickness was studied. The simulation results showed that thethickness of the bulging zone was thinned, and the uniformity of thickness distribution ofthicker tube was better than thinner tube. The thinning ratio of thinner tube increased withthe increasing of strength ratio and thickness ratio, while the thinning ratio of thicker tubedecreased with the increasing of strength ratio and thickness ratio, and the difference ofthinning ratio between thinner and thicker tubes was decreased firstly and then increased.Both thinning ratios of thinner and thicker tubes decreased with the increasing length ratio,but the changes were minor, the difference of thinning ratio between thinner and thickertubes was minor too. The effect of friction coefficient on thinning rate of bulging districtwas not obvious. The effect of different factors on the amount of weld-seam movement of forming partswas studied. The results indicated that the weld-seam movement mainly occurred when thezone near the weld of the thinner tube formed during bulging process, and the amount ofweld-seam movement increased with increasing expansion rate. When strength ratio andthickness ratio, respectively, was0.7and1.1, the weld-seam moved from thicker tube tothinner tube. But when the strength ratio and thickness ratio, respectively, was greater than1.0and2.3, the weld-seam moved from thinner tube to thicker tube, and the amount ofweld-seam movement increased with increasing strength ratio and thickness ratio. Thedirection of weld-seam was constant when the length ratio and friction coefficient changed.The amount of weld-seam movement increased firstly and then decreased when the lengthratio increased, but only existed0.1mm fluctuation, which had little effect on theweld-seam movement. The amount of the weld-seam movement decreased with theincreased friction coefficient, and existed0.32mm fluctuation.Based on the results of the orthogonal experiment, the primary and secondary factorswhich affected the thinning ratio of the zone near the weld of the thinner tube followed bythe thickness ratio, the strength ratio, the length ratio and the friction coefficient, and thethinning ratio reduced to13.47%at the condition of superior level combination, whichoptimized structure of tailor-welded tube with dissimilar material and thickness. |
