| The drawing times of stepped cylindrical part are traditionally estimated by the ratio of its two adjacent steps diameter without consideration each step height, which has big errors and is not convenient to provide guidance to production. Thus, it is important to accurately and efficiently predict the drawing times of the stepped cylindrical part for optimizing the deep drawing process parameters, reducing manufacturing cost and improving the product quality.Firstly, the material parameters and the true stress-strain curves of 08A1 were obtained by the tensile experiments of 08A1 sheet metal with thickness of 1.0 mm in this paper. After the forming coefficient w of 08A1 two-step cylindrical part was defined basing on the forming limit diagram of 08A1 steel, and the maximum forming coefficient wmax?1.0 was used as pull crack criteria, the drawing processes of 08A1 two-step cylindrical parts were simulated with the Abaqus FEM. Then the influences of the part geometry parameters such as small-step height h2, big-step height h1 and small-step diameter d2 on the maximum forming coefficient wmax were analyzed, and the distribution law and size variations of the maximum forming coefficient wmax were obtained, and the drawing times of 08A1 two-step cylindrical parts with different ratios of h1/d1, h2/d2 and d1/d2 were predicted. Lastly, the prediction results were verified by drawing experiments of 08A1 two-step cylindrical parts. The main results are as follows:1) The Young's modulus and yield stress of 08A1 obtained by tensile experiments are 194.0 Gpa and 200.0 MPa, respectively.2) The maximum forming coefficients wmax of the 08A1 two-step cylindrical parts always appeared in the small step, and transferred from the small step wall to its bottom corner with the increase of drawing depth. The danger area still located at the junction of the small step bottom fillet and its wall.3) The size of the maximum forming coefficient wmax increased with the degree of drawing deformation, and increased rapidly when the danger area was about to crack, namely when the maximum forming coefficient wmax of the two-step cylindrical part was close to 1.0.4) Drawing times of 08A1 two-step cylindrical parts were obtained by FEM numerical simulations as:when h1/d1?0.184 and h2/d2?0.681 and d1/d2?1.323, or h1/d1?0.478 and h2/d2?0.292 and d1/d2?1.323, or h1/d1?0.184 and h2/d2?0.45 and d1/d2?2.04, the drawing times were 1, where h1, d1, h2, d2 were the height and the diameter of the big step and the small step, respectively. When h1/d1=0.184 and 0.681<h2/d2?<0.875 and d1/d2=1.323, or 0.478<h1/d1?0.723 and h2/d2=0.292 and d1/d2=1.323, or h1/d1=0.184 and 0.45<h2/d2?0.563 and 2.04<d1/d2?2.55, the drawing times were 2. In other cases, a number of drawing times were needed.5) The drawing experiments were completed by setting different small-step heights h2, and the drawing times obtained by experiments were consistent with the simulation results, which verified the feasibility of the simulation prediction and the reliability of the results. |
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