Study On Deformation In Open Punching Process

The open punching is a basic step in the free forging production process, is one of necessary step for many circular cross-section hollow forgings. By means of numerical simulation and physical simulation, this paper researched the cylindrical billetes’deformation that punching with circular or square solid punches in the free forging process.The major work and results this paper have done are as follows:(1) Simulated the round hole workpiece’s deformation in forming process of the aperture ratio Do/d (the diameter ratio between the cylindrical billet and punch) range from1.50to5.00. Use reverse-solving method, proposed pre-forming solutions for the purpose of improving the round hole workpiece’s forming defects, designed the preform billet’s geometry as "Concave convex+concave arc surface of revolution". Physical simulation experiments verified the reasonableness of the preform billet.(2) Use point-tracing method studied the square hole workpiece’s deformation characteristics systematically for different Do/a (ratio between cylindrical billet’s diameter and square punch’s side length), then verified by physical experiments. The results show that:its height keeps increases when Do/a=12.0, when Do/a<6, the height decreases first and then increase,the height inflection point have different h/H0value all along the punching process. The upper end face is of pull-shrink, the degree of the outer edge’s height and the orifice edge’s collapse on the upper end face have a cyclical fluctuation in the circumferential direction. The outside surface has a larger bottom dimension, the outer contour of the cross section which perpendicular to the workpiece’s center axis is no longer a circle, but a periodic variation curve. The hole dimension first gradually increases from the bottom of the square hole, and later gradually decreases. The bottom face was higher raised corresponding to the normals of the midpoint on the punch’s side than to the transition angle of the punch’s walls.(3) Studied the workpieces’deformation features when the square punch’s fillet (fillet among the walls R1and fillet between the walls and the bottom plane R2) changes, verified by physical experiment, then measured and analyzed the experimental results. The results show that:with the increase of the fillet R1, the deformation state change to round workpiece’s gradully; With the increase of the fillet R.2, the height of the workpiece, the bottom diameter and the maximum diameter of the outside surface were all reduced, the upper end diameter increased, the differential of the hole wall thickness from the top to bottom decreased, the amount the billet’s material transferred to the surrounding increased.This article studied and suggested improvements for the round hole workpiece’s forming defects have an obvious practical significance; Study the square hole workpiece’s deformation law systematically has theoretical significance.