Study On Uniform Corrosion Failure Behavior And Fracture Criterion Of 6061 Aluminum Alloy

In recent years,corrosion has caused huge economic losses and waste of resources in various engineering applications,so the research on metal corrosion is of great significance.Aluminum alloy is widely used in high-end manufacturing industries such as ocean engineering,automobile manufacturing,aerospace and so on because of its light weight,high specific strength and strong plasticity.Due to the low surface hardness of aluminum alloy,uniform corrosion is easy to occur when it is used in marine,severe weather,space and other complex environments.At present,a large number of scholars have devoted themselves to the prediction of structural damage based on uniform corrosion,and put forward many prediction models.However,due to the difficulty of experimental verification model and the difficulty of solving parameters,there is still room for further exploration in this field.Finite element analysis of aluminum alloy failure behavior in corrosive environment has the advantages of high precision and low cost.It has important academic significance and good application prospects for evaluating the strength and service life of aluminum alloy materials.In this paper,the corrosion behavior of 6061 aluminum alloy in the surrounding environment is studied by means of scanning electron microscope,electrochemical workstation and microhardness tester.The effects of different corrosion solution on the mechanical properties of the materials are studied in two aspects,The effect of size on the failure behavior of aluminum alloy after uniform corrosion was also studied.The stress triaxial degree is chosen as the stress state parameter of 6061 aluminum alloy.The tensile sample,notch sample and shear sample are designed to make the material in different stress states.Combined with digital image correlation(DIC),quasi-static tensile test is carried out at room temperature;The quasi static compression test is carried out for the thin-walled structure of aluminum alloy.The uniform corrosion failure behavior of 6061 aluminum alloy was analyzed by finite element method.The results show that:(1)6061 aluminum alloy has uniform corrosion in different corrosion solutions,and the surface morphology of the material changes after corrosion.By the depth statistics of the 3D roughness reconstruction of the corrosion surface,it is found that the number of micro pits in uniform corrosion obeys the logarithmic normal distribution.Combined with the criterion of Cockcroft Latham ductile fracture,the finite element simulation analysis of single pit is carried out with the maximum size of corrosion sample,and the ratio of the integral amount of strain energy and the non corrosive sample is in high agreement with the calculated strain energy integral.(2)The corrosion rate of 6061 aluminum alloy increases with the increase of sample size in the same corrosion solution,and uniform corrosion has an effect on tensile,shear and compression properties of different size samples.The stress triaxial degree of tensile specimens with conventional and mesoscopic dimensions was basically unchanged before and after corrosion,and the failure strain of the conventional size tensile specimens decreased by 58%,but the tensile specimens with mesoscopic size decreased by 69%.The effect of uniform corrosion on failure strain of conventional shear specimen is small,which reduces the failure strain by 66%.(3)The fracture strain and triaxial stress of the samples with different stress states were extracted by LS DYNA finite element method.The fracture behavior of 6061 aluminum alloy mesoscopic size specimens and conventional size specimens with different triaxial stress were studied respectively,and the MMC fracture curves were obtained.The corresponding numerical simulation model is established by gissmo fracture failure criterion.The simulation results are in good agreement with the experimental results,and the uniform corrosion failure behavior of 6061 aluminum alloy can be accurately characterized under different stress conditions.The failure model has the advantages of convenient parameter solving and high simulation consistency,which lays a foundation for failure prediction of uniform corrosion aluminum alloy with mesoscopic size and conventional size.