Experimental And Simulation Study On Damage Behavior Of Aluminum Alloy Plate Considering Temperature And Strain Rate

Aluminum alloy has been widely used in aerospace,navigation,automobile manufacturing,and other fields because of its excellent specific strength and specific stiffness.However,the plastic deformation ability of aluminum alloy at room temperature is poor,the plastic forming mechanism assisted by high temperature is not clear and the control method is not systematic,which limits its application in key industrial fields.As an important design and analysis method in the field of plastic processing,finite element simulation technology can accurately simulate the plastic forming process and defect prediction of metal materials.However,with the help of finite element simulation,it is very important to predict and optimize the processing and forming process of aluminum alloy under different temperatures and deformation conditions,and accurately construct the constitutive model of the aluminum alloy materials.In this paper,the strength and uncoupled damage constitutive models of aluminum alloy under the complex machining environment are sorted out.In view of the shortcomings of existing models,a new material damage model is constructed based on the mechanical experimental results of 7055 aluminum alloy plates under different strain paths,strain rates and temperatures.The accuracy of the proposed damage model is verified by the comparative analysis of experimental and simulation results.The main research contents are as follows:(1)A series of mechanical experiments of aluminum alloy sheets are carried out,including uniaxial tensile tests at room temperature,notch tensile tests,variable path tensile shear tests,and tensile tests and bulging tests at different temperatures and strain rates.In tensile tests at room temperature,the DIC three-dimensional speckle system is used to obtain the fracture strain of 7055 aluminum alloy under different stress states,and output the force-displacement curve of uniaxial tension.Three different temperatures and rates are selected for hightemperature tensile and bulging experiments,and force-displacement curves and equivalent stress-strain curves obtained from high-temperature tensile experiments are output.The parameters of the hardening equation are solved by combining equivalent stress-strain curves.(2)An uncoupled damage model considering the effects of temperature and strain rate is constructed.The correction terms of temperature and strain rate are added based on LOU and MMC fracture criteria.The correction terms are used to couple temperature and strain rate.The J-C hardening model and Swift hardening model are modified,and two new hardening equations suitable for LOU and MMC fracture criteria are proposed.Combining the J-C hardening model and the modified J-C hardening model with the LOU fracture criterion respectively,the uncoupled damage models(JC-LOU and MJC-LOU)are constructed.Combining the Swift hardening model and the modified Swift hardening model with the MMC fracture criterion respectively,the uncoupled damage models(S-MMC and MS-MMC)are constructed.(3)Identify damage model parameters.Through the equivalent stress-strain curves obtained from experiments at different temperatures and different strain rates,the parameters of the hardening equation are fitted based on the least square method.The parameters of LOU and MMC fracture criteria of 7055 aluminum alloy at room temperature are fitted in the form of nonlinear surfaces through fracture strain values obtained by DIC equipment.Combined with the parameters of temperature term and strain rate term obtained by the least square method in the hardening equation at high temperature,all parameters of four uncoupled damage models of 7055 aluminum alloy are finally obtained.(4)Research on finite element simulation.After completing the construction of damage models and the identification of damage model parameters,the finite element simulation model is established according to the size of each experimental sample(1:1),and the boundary conditions of simulation are defined according to the loading conditions in each experiment.Through the finite element simulation software,combined with the proposed damage model,the finite element simulation of 7055 aluminum alloy under high-temperature tension and hightemperature bulging is carried out.Comparing the simulation results with the experimental results,the accuracy of the damage model is verified,and the applicability of the model for different paths is analyzed.