FORMATION OF QUALITATIVE INDICATORS OF PRODUCTS BY ROLLING STAMPING PROCESSES

The influence of rolling stamping on the service characteristics of products is investigated in the work. Based on the analysis of deformation kinematics, stress-strain state, microstructure and evaluation of deformability of workpiece material, ways to increase geometric accuracy, vacuum tightness, electrolytic stability and mechanical characteristics of product material, as well as ways to improve the material of workpieces for their subsequent processing. The influence of active friction forces on the nature of the material flow during SHO was established, which contributed to the development of new processes that allow to bring the shape and dimensions of the workpiece as close as possible to the finished part. Thus accuracy of the sizes of details corresponds to 7-11th qualities of accuracy, and roughness of the processed surfaces makes Ra = 2,5… 0,63 microns. The process of reshaping the square billets into round ones by the method of SHO is effective, which increases the utilization factor of the metal and reduces the anisotropy of its mechanical properties. The characteristic of flat anisotropy λr, adopted in sheet metal stamping as a characteristic of the ability of the material to form scallops, decreases as a result of reshaping by 70-80%. The relative difference in yield strength in the plane of the sheet decreases from 0.10-0.15 to 0.03-0.05. The ultimate tensile strain increases by 8-10%, and the uniform uniform strain - by 5-8%. This improvement in the characteristics of the material reshaped by rolling blanks leads to the fact that when drawing cylindrical products, the value of scallops decreases by 2-2.5 times, and the value of the maximum degree of drawing increases by 10-15%. This reduces the relative difference in wall thickness along the perimeter of the elongated workpiece, and the change in wall thickness along its height becomes linear. Thus, the use of SHO processes significantly improves the quality characteristics of products.

ELASTIC WAVE PROPAGATION IN A CYLINDER WITH EXTERNAL ACTIVE FRICTION

Рассматривается распространение волн в упругом цилиндрическом теле, взаимодействующем с внешней движущейся абсолютно недеформируемой средой (обоймой) при ударной нагрузке на передний торец. Сила трения, возникающая на контактной поверхности, прямо зависит от параметров распространяющихся волн и в силу движения внешней среды - она является активной. Поставленная одномерная задача решается аналитически методом характеристик. Получены точные решения распространения волн напряжений в цилиндре. Обнаружено увеличение параметров волн со временем и с расстоянием, определено влияние параметров внешней нагрузки и физико-механических характеристик цилиндра на параметры увеличения распространяющихся волн. Обсуждены место и время выравнивания скоростей частиц цилиндра и движения внешней среды, а также напряженное состояние частиц цилиндра.

Numerical analysis of porous blank die forging in the die with the implementation of active friction forces

The paper provides the results of simulating the hot die forging of porous powder preforms with active friction forces applied along the lateral surface of the deformable blank by means of internal cohesion in the die-material system. The study covers the evolution of relative density distribution over the blank cross section at different stages of deformation, stress-strain state and total strain force while varying the loading boundary conditions by changing the initial compression force applied to elastic elements that prevent the die from displacement. It is shown that active friction forces acting on the periphery of the forging adjacent to the die inner side result in areas with a significantly higher deformation intensity compared to deformations in the center of the blank volume. At the same time, the volume of the high deformation intensity area and maximum values of deformation increase with a decrease in the spring initial compression force and, accordingly, with an increase in the die displacement value during deformation. Automatic die displacement due to internal cohesion in the die-deformable material system leads to a decrease in the total deformation force, and with a decrease in the die displacement value during deformation, the deformation force increases.

Reverse extrusion of bar stock with active friction and end swell stretching

A combined process of shaping is considered which consists in the combination of reverse extrusion of bar stock and thinning an end swell in a part by means of matrix displacement in the direction opposite to the punch stamp motion. The investigations are carried out in the DEFORM complex. In the course of investigations there is defined a character of a metal flow, force characteristics of the process are defined.