Deformation And Damage Behaviour Of Aluminium Alloy Automobile Component

As result of the need to save energy and protect the environment, the use of aluminium alloy space frames are increasing. Aluminium alloy exhibits the property of high specific strength and low specific stiffness compared with steel.Meanwhile Aluminium alloy has good ductility, which being manufactured in complicated cross-section component and space-frame by extrusion, stamping, die-casting and welding. The use of aluminium alloy not only reduces the weight of space-frame but ensure stiffness as well. At the same time, advanced aluminium alloy space-frame body is the development direction of transportation means in the future. This paper studied deformation and damage behaviours of aluminium-alloy component, focus on extrusion-complicated component under axial compression and tubular T-joints component under plane bending combining tests with FEM (finite element method).In this paper, the series of 6000 (AA6014,6061,6063) aluminium-alloy were characterized under tensile and shear loadings including strain-rate dependence, anisotropy effects and processing influences. At the same time, stress states also considered when choosing the damage model for the damage behaviour of the components depended strongly on the stress triaxiality. Fracture strain decreased remarkably with increasing triaxiality and damage mechanisms could be quite different at high and low triaxiality. Therefore, it was necessary to characterize the influence of stress triaxiality on damage beahviour with relevant experiments then to simulate it with a verified damage model. The results showed:at low stress triaxiality, Johnson-cook damage model gave good result, while high stress triaxiality, Gurson model gave good result. In addition, damage parameters depended on size of mesh, damage parameters reduced with mesh size increasing. Macroscopic test showed that fracture strain of plate tension was larger than that of notched plate tension; yield stress of plate tension was lesser than that of notched plate tension. Furthermore, fracture strain of pure shear was much larger than that of plate tension. Moreover, the fracture graphic analysis suggested that the fracture appearance in 6061 and 6063:dimple mechanism was increasing and shear mechanism was decreasing with stress triaxiality enhancing. Fracture mechanism of notched plate tension was dimple, but large shear dimple and shear facet were observed in shear test,but shear fracture mechanism and tension fracture mechanism mixed for plate tension test, shear fracture occurred on width or thickness in microscopically. Tension fracture occurred in notch tension test.Fellowed that fracture path of 6063 tension test has been implemented in FORTRAN and introduced in ABAQUS by user subroutine.An extensive experimental research project has been carried out to study the crash behaviour of a complicated cross-section with different thicknesses of aluminium extrusions subjected to axial loading. Test specimens were'made of the aluminium alloy AA6014. Tempers T7 and provided by Daimler Chrysler. Prediction of the deformation and damage behaviour was carried out with the material properties, which were acquired in above. To sum up, deformation damage parameters received combining the test with simulation. Because damage model dependented on stress triaxiality, the appropriate damage model should be chose to simulate deformation and damage behaviour under different type loadings, the finer the element-size, the better the calculation and simulation result, however the calculation will cost a lot of time. Therefore, appropriate element-size not only ensured the precision of results, but saved time as well. Damage parameters depended on element-size, and the element size is coarser in components than in specimens. Thus to the component, it is necessary to adjust the damage parameters according to the element size. The effects of the inhomogeneous material properties on the component behavior depended on loading situation. In future work, a link between extrusion simulation, microstructure simulation and crash simulation will be an important step to crashworthiness assessment.Characterization of aluminium alloy welded joint was carried out. A test method called double-hole micro-shearing was proposed without small specimens. Two through holes beside the measured zone were acquired. Micro-shearing test was performed to get local intensity, deformation, and damage behaviour of local material. Then radius of holes and distance of bridge were changed to study deformation and damage behaviour of local material under different stress states. TIG (Tungsten inert Gas) welding was applied in 6061 and 6063 aluminium alloy joint, then inhomogeneous of organization and mechanical properties of welded joint were studied. To butt welded joint, base material is 6061 and 6063, while T welded joint is 6063. A lot of experiments proved that reservation clearance affected molding of weld in large degree. Weld shape was good when the right clearance was selected. The results showed that the lager one resulted in destroy of weld, on the contrary, the lesser one, more quantity of heat, which would lead the wider of HAZ that deduced the intensity of weld joint. To the T welded joint, because of thin plate need less welding current, therefore weld penetration depth, which was hardly, influenced by clearance and slope, on the contrary which resulted in weld sag and cold joining. So weld penetration depth was ignored when considered strength calculation in this paper. In order to characterize the properties of welded joint correctly, inhomogeneous of organization and mechanical property which would be indicated by metallographic and hardness test must be considered in detail. Combining simulation with micro-shearing test was applied in T welded joint too, true strain and true stress of different zones on welded joint were acquired. Plate tension tests and simulations of butt joint were performed based on the above result. Deformation and damage behaviour of butt joints with melt welding under static and dynamic loadings were studied. Then influence on properties of joint in over-match and under-match and width of weld under different match based on Gurson and Johnson-cook model were investigated. Fracture intensity and strain were higher under dynamic tension loading than that under static tension loading, the two parameters increased with increasing of strain ratio. The samples in the same weld techniques and no lacuna, the dynamic tension results showed that fracture intensity and strain of 6061 were higher than that of 6063. It certificated that mechanical of 6061 was better than that of 6063, Different sample method of same material (including vertical and along weld direction) test results showed, fracture intensity and strain of samples which along weld direction were better than that of vertical weld direction. Combining Double-hole micro-shearing experiment with simulation were performed on welded joint to get the material mechanical and damage parameters. Then the parameters were used to simulate static plate tension tests. Good results mean correct model and precision test; In addition, based on the correct model influence of mechanical mismatching on the failure of welded joints were studied. The results showed the damage of under-matched joints mainly occurred in HAZ, the narrower the joint, the lower the damage resistance of the specimen, based on this result, a reasonably wide weld should be chosen for under-matched welded joints. While, to the over-matched joints, the damage mainly occurred in the base metal area adjacent to the joint, the narrower the joint, the higher the damage resistance of the joint. A reasonably narrow weld should be chosen for over-matched welded joints.Tests and simulations of T welded joint were performed. Deformation and damage behavior of 6063 T welded joint under plane bend were researched combining tests with simulations. Designed T welded joint samples, which can be used to study deformation, and damage behaviour of corner weld under different stress states. Two damage models (Gurson& Johnson-cook) predicted the damage behaviour, the former give better result than the later. To the S type weld, crack began in melt line then enlarged to HAZ, the marco-crack formed in HAZ in the end. To the U type, weld crack origin nated in weld material, then enlarged to HAZ, simulation gave good prediction for this process.