PRESSING HI-TECHS IN MECHANICAL ENGINEERING, AVIATION AND TRANSPORT

Abstract. Results of workpiece thickness variations due to sheet metal stamping job, that is: tube bending, pressing, stretching, drawing-out, ironing are presented in the paper. The necessity in such work is fuelled by the contemporary increasing requirements for parts strength resulted from sheet metal stamping. Much attention is paid to tube bending, for it is bending that changes not only form of the section of the tube billet, but also leads to a thickness loss in a tensile layer together with an increase in thickness of a compression zone. The methods of reducing tube thickness variation are proposed. Results of changes in workpiece thickness under drawing-out are given. It is shown that increasing the punch radius can reduce the thickness variation by 10 %. In most studies on sheet stamping, the thickness of the primary blank and rolled iron is not taken into account, while the primary part thickness can vary by 20 % when ordering metal of single precision. A thick-sheeted drawing-out in the AutoForm program is simulated in order to determine the possibility of the program in predicting changes in the shape of the sheet and thickness due to the action of bending. It is shown that AutoForm models the shape of the part well enough after stamping. According to the specification, AutoForm and the experiment showed similar results in thickness and also revealed areas with minimal thickness. For the selected stamping parameters, the minimum thickness is observed at the point of transition of the cylindrical surface to the punch radius and at the point of transition of the punch radius to the bottom plate. Since most metals subjected to sheet stamping have anisotropy properties, it has been shown by experiments and has its theoretical proof that thickness can vary significantly along the perimeter. It has been proven that the thickness variation along the perimeter of the part may exceed 35 %

sheet stamping, thickness variation, tube bending, drawing-out