The paper presents the research of plastic expansion of a pipe workpiece by punches of various configurations. It is shown that interest in this process is caused by the development of oil production, where there is a need to increase the diameter of well pipes, the automobile industry, where the protection of the driver and passengers in case of accidents comes first. Here, stable plastic deformation plays an important role as a good absorber of kinetic energy, etc. Data on the problems of expanding pipe ends are given, where special attention is paid to the destruction of the end in the form of localization of deformations and appearance of a longitudinal crack. To eliminate this phenomen onvarious technological methods are used. Here the influence of the design and shape of the punch on the localization of deformations along the thickness of the workpiece is researched. Several spatial outlines of the tool are proposed to create an effective reloading of the pipe workpiece in the deformation zone. Based on numerical modeling, the distribution of stresses according to Mises, the displacement of the end of the semi-finished product and logarithmic deformations in the radial direction is shown for each standard size of the punch. Comparative results reveal an increase in the thickness of the workpiece in the dangerous section for all presented punches. The comparison was carried out with a reference tool that has a straight generatrix of a tapered surface. The best results are shown by a punch with an enlarged generatrix at the end of the working stroke. Attention is focused on conducting further research in order to study the possibility of overcritical deformation by the proposed tool.

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This paper shows that the technological preparation of production accounts for 20‒70 % of the total labor intensity of technical preparation. An important role belongs to the applied programs of finite-element modeling. However, such software packages often cannot be purchased by small-scale industrial enterprises for various reasons. Therefore, special empirical and analytical calculation models are used, which have proved to be quite effective in typical metal processing processes. Drawing a cylindrical hollow part was used as an example of the improved analytical dependence to calculate meridional tensile stresses. Existing analytical models of the process accounted for the bending moment through additional stresses. However, this approach only roughly described the deformation process. It was possible to refine the existing analytical dependences by introducing a term into the differential equilibrium equations that takes into consideration the bending moment that acts in the meridional direction when a workpiece passes the rounding on the matrix edge. Analysis of the obtained expression revealed that the bending of a workpiece gives rise to the stretching meridional stresses, which depend on the ratio of the squares of the thickness of the workpiece and the radius of the matrix rounding. The results of the estimation data from the numerical and theoretical models coincided for small values of the radius of the matrix rounding of 1‒2 mm, which confirms the adequacy of the analytical solution. In the numerical model, there is an extreme point where the tensile stresses have a minimum and, after it, begin to increase; this corresponds to the matrix rounding radius of 5 mm

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