INVESTIGATION OF THE EFFECT OF THE INITIAL ANISOTROPY OF THE MECHANICAL PROPERTIES OF ALUMINUM ALLOY SHEETS 8011А ON THE CRITICAL ANGLE OF INCREMENTAL FORMING

The results of an experimental study of the effect of anisotropy of the mechanical properties of sheet blanks on the limiting angle of incremental shaping are presented. According to the developed cold rolling routes in combination with heat treatment of aluminum alloy 8011A sheets, samples with different coefficients of transverse deformation were obtained. The average value of the anisotropy indicators in the plane of the sheet and the coefficient of planar anisotropy are calculated. The values of the limiting angle of incremental shaping were obtained on a special stand consisting of an industrial robot KR 160 R1570 nano, a frame for fixing the workpiece and a non-contact optical deformation measurement system Vic 3D. Based on the obtained values, the dependences of the distribution of the main deformations e1 and e2 in the direction of rolling along the generatrix for sheets with different anisotropy indices were constructed. It is determined that the nature of the strain distribution is the same for the samples under consideration. From the center to the edge of the workpiece, the deformations increase to the maximum value (the section of the curved generatrix), and then decrease to zero (the transition area from the generatrix to the bottom). However, the main deformation and the position of the maximum for sheets with an anisotropy index Δμ > 0 is higher than for sheets with Δμ < 0. Then, for the manufactured sheets, the limiting angle of incremental shaping was determined, equal to 67.8° for samples with a positive index of planar anisotropy and 47.6° for samples with a negative one. The obtained results, together with the position of the crack on the conical parts, indicate a significant influence of the anisotropy of mechanical properties on the process of incremental shaping.

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