Study On Hydroforming Process And Parameter Optimization Of 304 Stainless Steel T-shaped Tube

Tube hydroforming technology is a new advanced manufacturing technology of hollow lightweight structural parts,which is developed under the background of structural lightweight and has wide application prospects.In this paper,304 stainless steel T-shaped tube is taken as the research object,and ABAQUS finite element software is used for numerical simulation.The plastic deformation law(stress and strain,wall thickness distribution and metal flow)of T-shaped tube is discussed.The effects of process parameters such as internal pressure,axial displacement and equilibrium pressure on the branch height and wall thickness distribution of T-shaped tube were studied.It is of great engineering significance to study the forming process of T-shaped tube,analyze the influence of various influencing factors on the forming results,and realize the optimization of controllable factors,which is also the key research topic of engineers in various countries.The main contents of this paper are summarized as follows:1.In the hydroforming of T-shaped tube,the main tube is subjected to axial compressive stress and the branch tube is subjected to axial tensile stress;Only the top of the branch tube is thinned,but the transition fillet,both ends of the main tube and the bottom of the main tube center are thickened seriously;The displacement of both ends of the main tube is the largest under the action of the feed punch,and the material at the bottom of the main tube center hardly flows.2.The matching between internal pressure and axial displacement directly affects the forming quality of T-shaped tube.When the internal pressure is too small and the axial displacement is too large,the branch height of T-shaped tube increases significantly,but the wall thickness is not uniform,and the tube is prone to wrinkle;When the internal pressure is too large and the axial displacement is too small,the height of the branch tube is also improved,but the effect is not as obvious as the axial displacement,and the branch tube is prone to fracture;When the internal pressure is loaded by convex broken line and the axial displacement is loaded by concave broken line,the quality of T-shaped tube is better.3.The radial equilibrium pressure is applied to the branch bulging area of T-shaped tube,which improves the stress state of the branch bulging area and the forming limit of the material.The height of branch tube is greatly reduced by excessive equilibrium pressure,and the small equilibrium pressure will make the top of branch tube thin and easy to break;When the equilibrium pressure rises slowly in the early stage of forming and the latter is rising rapidly,the height of the branch tube is relatively high and the wall thickness is relatively uniform.4.The radius of transition fillet and friction coefficient affect the fluidity of materials.The height of T-shaped tube branch is lower and the branch tube thinning is serious when the radius of transition fillet is too small;When the radius of transition fillet is too large,the branch height increases significantly,but the wall thickness is very uneven.The smaller the friction coefficient,the higher the branch height and the uniform wall thickness distribution of the formed T-shaped tube.5.The process parameters of T-shaped tube loading path are analyzed and optimized by response surface method.Taking the intermediate internal pressure P₁,the internal pressure change time T₁,the intermediate displacement S,the displacement change time T₂ and the equilibrium pressure P₂ as the design variables,the thinning rate and the branch tube height as the response objectives,and fitting the regression equation to obtain the response surface model.Finally,the global optimal solutions of five design variables are obtained.