Russian Technological University “MIREA“, Moscow, Russia

V. A. Kadymov, Dr. Phys.-Math., Prof., Dept. of Higher mathematics and Programming

University of Science and Technology MISIS, Moscow, Russia
N. L. Lisunets, Cand. Eng., Associate Prof., Dept. of Metal Forming, e-mail: lisunec@yandex.ru

Moscow State Technological University “STANKIN“, Moscow, Russia
E. A. Yanovskaya, Cand. Eng., Associate Prof., Dept. of Applied Mathematics

In the process of manufacture of large–sized parts from sheet materials, such processes as straightening of sheets by stretching, bending with stretching, and fitting according to templates in special hydraulically driven stretch-forming machines are in demand. Absence of metal billet slippage under the grips (on the one hand) and unacceptable critical compression forces of the grips (on the other hand) are considered as important circumstances. Such critical compression forces can cause plastic deformations of billet sections located in the areas of action of the grips. Therefore, the analysis of the power characteristics of the process is an urgent task. The article presents formulation and solution of the flat problem on compression of a plastic strip between two parallel rough planes of grips, complemented by asymmetry of the conditions at the spreading ends. An upper estimation value of the total compression force is found by grips at the end areas of the plastic stretching strip, at which, plastic upsetting of its end parts occurs together with plastic stretching of the strip. It is shown that consequent deformation finalizes in thinning and tearing-off not in the middle stretching part, but near the inner boundary of contact with the grips.

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