Justification of the effect of transitional modes on the quality of ready-made products when their treatment is used by plastic deformation methods from the position of the wave and auto vibration processes

Abstract

Purpose. Substantiation of the role of longitudinal and transverse wave processes in the surface layers on the quality of finished products obtained by plastic deformation methods, such as cold rolling, stamping, running in, drawing and others. Research methodology. In the work, to describe the transients at the beginning of the interaction of the tool with the workpiece, a computational model was applied in which the surface layers of the workpiece are represented as a beam on an elastic base, loaded with suddenly applied tangential forces, often exceeding their critical values. The reasons for the occurrence of unstable dynamic states of such a beam, in which the integrity of the surface layers of the workpiece and parts may be disturbed due to the occurrence of supercritical stresses and deformation in the material of the outer layers, are investigated. Findings. The results were obtained on the definition of hazardous states of the surface layers of the workpiece, under the action of suddenly applied loads at the initial moments of the capture of the workpiece, as well as at the moments when the tool slips over the workpiece during the alignment of their speeds. Originality. It consists in the fact that the first dynamic problem was set and solved for the surface layers of the workpiece, represented as a two-support beam on an elastic base loaded with a suddenly applied longitudinal force, which can significantly exceed its critical value. Denoted areas of dynamic instability of the surface layers of the workpiece. The practical value of the work lies in the fact that the modes of operation of the metal forming machine and the parameters of the workpiece were identified under which conditions for obtaining products of insufficient quality may arise. As well as developed recommendations for improving the quality of finished products. Key words: metal forming, transients, longitudinal wave, shear wave, billet, loaded layer, overload coefficient, dynamic buckling, tool, rolling, knurling, drawing, hypothetical beam, impact, elastic wave propagation velocity.