Experimental Study And Numerical Modeling Of Aluminum Alloy Sheets’ Mechanical And Constitutive Characteristics Under Different Pre-Strain And Baking Conditions

The application of aluminum alloy in automotive industry is booming since thetrend of automobile lighting.6000series aluminum is widely used in automotive bodyshell with its outstanding comprehensive performance.Original property of material is changed in the manufacturing process and vehicleperformance assessment needs more accurate and truthful constitutive model andmechanics performance of materials. Funded by the University Research Project ofFord Motor Company, material constitutive model and mechanical performance ofA6111aluminum alloy is studied under different pre-strain and baking conditions.Following experiments are conducted. T4P heat treatment of materialâ†'Pre-strain ofdifferent level and directionâ†'Baking treatment of different profileâ†'Uni-tensile testsof different directions. Total number of tensile test is880and this research has drawnthe following conclusions.1) Pre-strain and baking’s influence on the yield strength, tensile strength and bakehardening effect of A6111material is analyzed.Yield strength, tensile strength and bake hardening value increase with addingpre-strain level, higher baking temperature and longer baking duration.The increased value of tensile strength to adding pre-strain is not as remarkable asthat of yield strength, which leads to higher yield ratio when adding pre-strainlevel.Increasing both baking temperature and duration will lead to increase in the bakehardening (BH) value and effect of temperature is more prior. Largest BH value isobtained after the profile of baking at170°C for30minutes.Significant bake hardening response appears only with pre-strain.2) Anisotropy behavior of A6111aluminum alloy after pre-strain and baking is studied.R-value of different directions are tested and it is highest in45°and30°direction, followed by60°and90°direction and lowest in the0°direction.Pre-strain prior to loading causes intensified anisotropy. The increase of yield andtensile strength is much more significant when pre-stretching and tensile test arein the same direction. Yield ratio tested when pre-strain and tensile test in samedirection is larger than that of different directions.3) Signs of PLC effect are observed.PLC effect could be intensified by pre-strain and it is more significant whenpre-stretch and tensile tests are in the same direction.4) New flow stress model of aluminum alloy related to pre-strain, baking andanisotropy is built.Flow stress curves obtained under different conditions are fitted with differentmodels and H-S flow stress model is selected.Key factors’influence on the fitting parameters in H-S model is analyzed with themethod of inductive statistics based on experiment results.Pre-strain level and baking temperature is introduced into H-S model and newmaterial constitutive model is built.