Experimental And Simulation Study On Tube Hydroforming Of Car Sub-frame

With the rapid development of automotive industry,more and more people began to focus on reducing the weight of the structure to achieve material conservation and reduce energy consumption.Reducing body weight on the one hand can save the use of materials;on the other hand can reduce fuel consumption and vehicle exhaust emissions.The hydroforming technology is one of the main ways to reduce the body weight from the manufacturing process in the condition of ensuring the safety performance and structural strength of the car.Taking the hydroforming of sub-frame as research object,the method of experiment,simulation is used to study the hydroforming law of sub-frame.We choose the wall thickness characteristics of formed parts as the discussion object.As most of the subframe cross section is rectangular,We study the hydroforming characteristics of the circular tube bulge to the rectangular tube firstly.Based on this,to study the forming law of sub-frame.In order to study the forming rule of the forming pipe in the rectangular shape mold,a small internal high pressure experiment platform was set up and the design,and then completed the hydroforming experiments of rectangular tube.The material tensile test was carried out to obtain the mechanical properties parameters.Based on this,the influence of the internal pressure,frictional force and load path of internal press on wall thickness of the hydroforming part are further studied by nonlinear finite element software.Firstly,we analysis the sub-frame hydroforming,Base on this,we used the nonlinear finite element software is used to simulate the whole process of the sub-frame hydroforming.Based on the numerical simulation results,the test results of the sub-frame forming samples were carried out by means of large-scale hydroforming equipment.The experimental results were compared with the simulation results to verify the correctness of the simulation.Then study the influence of the conditions such as the friction coefficient between the forming pipe and the contact surface of the mold,the loading method of the bulge pressure and the annealing treatment on the wall thickness of the hydroformed subframe.In this paper,the experiment and simulation analysis of the hydroforming of the rectangular tube and the sub-frame are completed,then the influence of the main parameters on the forming of the rectangular pipe and the sub-frame is obtained.The results show that the thickness of the sub-frame is reduced with the decrease of the friction coefficient between the contact surface with the mold cavity in the process hydroforming.In the middle of the sub-frame forming,the loading path of internal pressure increase slowly,is conducive to reduce the sub-frame wall thickness reduction.At the same time,when it completed the material feed,the tube appeared plastic deformation but the pipe is not completely die.The maximum thinning rate of the wall thickness is smaller.In the process of sub-frame hydroforming,the low-temperature annealing process can make the part wall thickness distribution is more uniform.In this paper,the hydroforming law of sub-frame was analyzed through the method of experiment and simulation,which can provide reference for the practical application of car sub-frame hydroforming.