Research On The Hydroforming Process Of Micro Stainless Steel Tube And Copper Tube

Currently,the demand for micro-tubes in the electronics,medical and micro-device industries is increasing,forcing the micro-tube hydroforming process to become one of the current research priorities.The existence of scale effect makes the hydroforming ability of microtubules low.In order to improve the microtubule forming ability and make the microtubule hydroforming process better applied to the actual production.In this paper,SS304 and H65 microtubules were used as research objects,and the following related studies were carried out.Firstly,the H65 microtubes of the size specification(diameter*wall thickness)2*0.3mm and 2*0.15 mm are subjected to annealing and recrystallization heat treatments at 400°C,450°C,and 500°C.Then the tensile test was carried out to obtain the mechanical properties of different H65 microtubule materials and to study their scale effects.Scale effect studies show that the plasticity of H65 microtubule deteriorates with decrease of wall thickness while the flow stress increases with decrease of wall thickness.Secondly,hydraulic free bulging test of axial feeding about SS304 and H65 microtubes was carried out.The test results show that the bursting pressure and the maximum diameter of microtubes show obvious dispersion.In a certain axial feeding range,the axial feeding process can significantly improve the microtubular bulging ability.Thirdly,GTN and five kinds of ductile fracture damage models were used to simulate the axial feeding of SS304 and H65 microtubules.For SS304 microtubules,GTN model and Ayada criterion can well simulate the relationship between axial filling and bursting pressure.Brozzo fracture criterion is superior to other criteria in predicting the maximum diameter of tube bulging when axial feeding is carried out in the range of 0.6-1.5mm.For H65 microtubules,GTN model can well simulate the bursting pressure and the maximum diameter of microtubules.Finally,the 30% bulging test and numerical simulation of H65 microtubule were carried out.Experiments show that 30% bulging microtubules are fewer in the case of hydraulic bulging without feeding.Experiments show that 30% bulging of microtubules is less without feeding,while 30% bulging of tubular parts is generally achieved in the case of 1.4mm axial feed.So the axial feeding process has a positive effect on the formation of microtubules.The numerical simulation results show that with the increase of axial feeding,the wall thickness at both ends of the tube in the guide zone increases,the wall thickness of the forming zone is improved,and the performance of microtubule hydroforming is obviously improved.