Determination Of The In-plane Anisotropy Of Aluminum Alloy Tube By Deep Drawing

Aluminum alloy tubes are usually prepared by multi pass extrusion and rolling.Aluminum alloy tubes prepared by complex processes form specific microstructure and texture distribution,so aluminum alloy tubes have obvious in-plane anisotropy.The existing anisotropy testing methods for tubes mainly include axial tensile test,circumferential tensile test,free bulging test and biaxial controllable loading bulging test.The above method can only test the anisotropy and plastic flow characteristics in the direction of the main axis of the tube,but can not directly test the mechanical properties in the direction of the non main axis of the tube at present.In order to solve the above problem,this paper establishes a local deep drawing test method for tubular samples,determines the steps of the deep drawing test method,and designs a special deep drawing device to test the in-plane anisotropy of aluminum alloy tubes.The steps of the deep drawing test method mainly include:1.Determine the shape and size of the sample and intercept the local tubular sample.2.The corresponding drawing device is designed according to the shape and size of the sample to be tested.3.Carry out the drawing test of local tubular specimen.4.The in-plane anisotropy of the tube was determined by analyzing the outline dimension of the specimen after deep drawing.The mechanical properties of AA2219 blank are measured through uniaxial tensile test.The rolling direction（RD）is 0°and the transverse direction（TD）is 90°.The plastic strain ratio r₀=0.44,r₄₅=0.89 and r₉₀=0.39 are measured.The local deep drawing finite element simulation and test of AA2219 tubular specimen are carried out through the above blank bending tube.The results show that when the rolling direction is along the hoop or axial direction of the tubular specimen,the earing is produced in the 45°direction of the tubular specimen;When the rolling direction is along the 45°direction of the tubular sample,earings are generated in the direction of the main axis of the tubular sample.By changing the in-plane anisotropy of the tubular specimen,the deep drawing specimens with different contour shapes are obtained,and the feasibility of determining the in-plane anisotropy of the tubular specimen by analyzing the contour shape of the local deep drawing of the tubular specimen is verified.Furthermore,the local deep drawing deformation characteristics of tubular specimens are explored through finite element simulation,and the influence of die structure,process parameters and friction coefficient on drawing deformation are analyzed.By using flat bottomed punch for deep drawing,the flow of tubular sample is more sufficient and uniform;Too large or too small fillet radius of punch and die is not conducive to uniform deformation of material.In the process of deep drawing,the flange area is thickened,and there is a critical value of the blank holder gap.When the blank holder gap is near the critical value,it has a significant impact on the plastic flow of the material.When the blank holder gap is too large,the plastic flow of the material is not sensitive to the blank holder gap.The friction coefficient has no obvious effect on the material flow in the range of 0.08-0.17.When the friction coefficient is small or large,it will aggravate the plastic flow difference between different directions of the material.A special drawing device was designed to carry out the drawing test of local tubular samples to explore the in-plane anisotropy of AA6061 extruded tube.The test results show that the earings are made in the axial and circumferential directions of the original tubular sample,indicating that the AA6061 extruded tube has obvious in-plane anisotropy.Combined with the drawing results of the known performance samples and the axial uniaxial tensile test results of the extruded tube,the in-plane anisotropy coefficient of the AA6061 extruded tube is determined according to the obtained sample contour shape after drawing.