Computer simulation of crystallographic orientations influence on earing during drawing

The practical implementation of the user material model, which takes into account the ideal crystallographic orientations, is illustrated in terms of drawing process simulation. The material model consists of the following elements: yield criterion, which takes into account explicitly the parameters of crystallographic orientation and the crystal lattice constants; linear isotropic hardening model; the tangent cutting plane algorithm for updating stresses. The model is implemented on the FORTRAN programming language as user material UMAT 47 for the software LS-DYNA. The drawing of caps made of 8011A aluminum alloy is simulated using the model. The blank texture consists only of one ideal crystallographic orientation: {124}<123>, {230}<231>, {135}<130> and {100}<100>. It is found that the stress-strain state of anisotropic axisymmetric blank during drawing changes both in the radial and tangential directions. In the direction of the minimum values of tensile radial strains the blank thickening occurs more intensively. Whereby a significant portion of the flange metal moves in the thickness and leads to the formation of cavities. In the places with maximum values of the radial strains the flange thickening is significantly less. Hence, the metal goes on increase of the cap height, forming an ear. It is determined that ideal crystallographic orientation {124}<123> causes formation of 4 ears at angle 45° to rolling direction, while orientations {230}<231>, {135}<130>, {100}<100> causes ears at rolling and transverse directions. Also it is shown that one possible combination of ideal crystallographic orientations, which eliminates earing and non-uniform thickness of cap, is the following: {124}<123> - 43,9%; {135} <130> - 29,2%; {230}<231> - 25,6%; {100}<100> - 1,3%. In addition, the influence of the ideal crystallographic orientations on the drawing force is studied. It is found that the drawing force of blanks with different orientations changes by more than 20% ({100} <100> - maximum force; {230} <231>, {135} <130> - minimum force).

LS-DYNA, simulation, drawing, earing, crystallographic orientation, material model, LS-DYNA