Numerical Simulation Research On Concave Bottom Box Forming By Hydrodynamic Deep Drawing

Automotive lightweighting is the main direction of the current development of the automotive industry worldwide.Due to its advantages such as light weight,high strength,and excellent corrosion resistance,aluminum alloy materials earned a great attention in promoting the lightweighting of automobiles.Among existing automotive parts,there are many parts with complex cross-sectional shapes and complicated processes.How to produce such parts with aluminum alloy materials is one of the problems currently facing the automotive industry.This article takes the thin-walled cone-bottomed cylindrical part as the research object,summarizes the non-isothermal hydroforming rules of aluminum alloy thin-walled complex parts,and provides a reference for other types of complex stamping production.Definition of material properties is a cornerstone for numerical simulation,that is,a flow stress constitutive model of the material needs to be obtained before the simulation.In order to establish the flow stress constitutive model of 6061-T6 aluminum alloy,this paper conducts unidirectional tensile tests on 6061-T6 aluminum alloy plates at multiple temperatures and multiple strain rates to obtain its stress-strain curves.Based on the curves and related data,the mathematical expressions of the Fields-Backofen constitutive model for 6061-T6 aluminum alloy are obtained through calculation in this paper to describe the flow stress,and in consider of the characteristics of 6061-T6 softening at high temperature,FieldsBackofen constitutive model under high temperature was modified by introducing softening factor.Finally,the mathematical expression of model calculated is verified for reliability.In the simulation,this paper first introduces the 6061-T6 aluminum alloy flow stress constitutive model to establish the material properties,and then studies the effects of different values of liquid chamber pressure,stamping speed,and friction coefficient on the forming of the part.Aiming at the anti-expansion behavior of the sheet due to the pressure of the liquid chamber in the beginning of liquid-filling deep drawing,a method of increasing the forward pressure was proposed,and the effect of the positive pressure on the anti-expansion behavior of the sheet was studied.Since then,the influence of the differential temperature environment on the forming quality has been studied.The research is on the performance of the strength of the straight wall of the sheet,the fluidity of the flange region,and the thickness reduction and uniformity under differential temperature conditions.According to the simulation results,the deep drawing performance of 6061-T6 aluminum alloy with different temperature filling liquid was summarized in the form of visual data,and the optimal values of various process parameters were pointed out.