Study On The Connection Performance And Numerical Simulation Of 6063 Aluminum Tube And 304 Steel Tube By Electrohydraulic Bulging

Electrohydraulic expansion is a kind of plastic connection technology based on electrohydraulic forming.Its connection performance is reliable and adaptability is high,so it has a broad application prospect in the fields of aircraft engine and automobile frame.In order to solve the connection problem of different high strength materials,304 stainless steel and 6063 aluminum tube are used as test materials in this paper.The mechanical properties of the joint are studied from the aspects of numerical simulation,connection performance,macro and micro morphology.First,the LS-DYNA commercial software was used to simulate the wire explosion and the deformation of the inner tube during the electro-hydraulic expansion.The numerical simulation model took the energy deposition curve as the input energy to analyze the velocity and stress distribution of the key nodes of the axial and radial sections of the inner tube.The velocity analysis of the inner tube in the expanding process showed that the inner tube material reaches a maximum value of 47m/s at 42?s.The velocity distribution at the same level is the same,and the corresponding deformation is also very uniform.At about 45 ?s,the equivalent stress on the surface of the inner tube reached the maximum value of 235.8 MPa,and most of the materials with obvious deformation were embedded in the grooves of the outer tube.The expressions of the average deformation and the embedding rate of the inner tube were defined.It was found that the deformation of the inner tube increases with the increase of the discharge voltage.The wider the notch of the outer tube is,the easier the inner tube material will flow into the corresponding groove.Under the same discharge voltage,the wider the notch of the outer tube is,the greater the deformation of the inner tube will be.Because the opening of the 4 mm notch is narrow,the increase of the discharge voltage can not increase the deformation of the inner tube very well.The larger the opening of the 8 mm notch is,the lower the energy utilization ratio,so the research object of the process test was determined to be the 6 mm notch.Then comparing the connection performance of different process parameters,it was found that the thinner the wire,the shorter the length and the larger the discharge voltage are,the higher the peak load is,the better the mechanical properties of the joint are.The central composite design method was used to optimize the three test parameters and established the response surface and regression equation.The actual value of the peak load was distributed in the regression equation to fit the straight line.It could be seen from the three-dimensional response surface that the interaction between the discharge voltage and the wire length on the connection performance is weak.The nonlinear interaction between the discharge voltage and the wire diameter as well as the wire diameter and length was obvious.Finally,when the discharge voltage is 10 k V,the wire length and diameter were 5.16 mm and 1.12 mm respectively,the optimal peak load was 25.89 k N.At last,the macro and micro characteristics of the joint under different process parameters were studied.The error could be controlled within 5% by comparing the deformation degree of the inner tube with the standard finite element model.The displacement of the inner tube in the radial direction had a great influence on the joint performance during the process of the joint.The deformation angle of the inner tube and the contact length of the inner tube were defined.The larger the deformation degree of the inner tube is,the smaller the corresponding ? angle is,and the larger the contact length ? is,the better the joint performance is.Through the analysis of the change of grain characteristics before and after the inner tube deformation,it could be found that the elongation and refinement of grain along a specific direction makes the material in this area harden,thus increasing the joint performance.Based on the actual process test,two different failure modes of the joint were established,and the change of the inner tube in the process of pulling off failure was analyzed by the finite element model.The process test and numerical simulation could be well consistent.