Moscow Polytechnic University, Moscow, Russia

M. A. Petrov, Cand. Eng., Associate Prof., Dept. of Materials Forming and Additive Technologies, e-mail: petrovma_mospolytech@mail.ru
E. V. Krutina, Cand. Eng., Associate Prof., Dept. of Materials Forming and Additive Technologies, e-mail: lenakrutina@mail.ru

Production of small-diameter tubes and pipework is an essential task. They are used in all areas of mechanical engineering, and production processes are constantly improving. The present study deals with the numerical modeling of dornless cold bending of a 30 mm diameter stainless steel pipe. The process parameters, such as bending radius, thinning coefficient and spring back angle, are computationally determined. Through finite element simulation, the directions of preferential thinning of the tube wall were established and defects, such as ovality of the crosssection, fracture and wrinkles, were identified. For the considered bending angle of 90° and at the bending radii, no material failures were found. However, there are areas with elevated values of principal stresses, which indicate significant tensile stresses. The deformation force varies in proportion to the wall thickness, which shows the major influence of the geometric factor and the minor influence of the technological indicator. The flattening factor depends on both the thinness factor and the bending radius. In order to avoid excessive reduction of the overall tube stiffness, this must be taken into consideration. When determining the springing, a significant discrepancy between the theoretical and calculated values was revealed, which shows the need to conduct experiments. Based on their results, reliability of the theoretical and numerical results can be determined, and their correction can be carried out.

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