Simulation Study On Void Closing During 3-D Deformation

In this paper numerical simulation and physical simulation were used conjointly to study the process of void closure in ingot during hot upsetting. The results of study deepened understanding of the complicated problem and there is certain reference value by making use of reasonable processes to eliminate void defects in ingot.3-D finite element method for large deformation is applied in numerical simulation to investigate the process of hot upsetting on about 50 cases of steel cylinder ingots with single or multiple voids which are different in dimension or location. Upon the numerical results, during closure process the shape of the voids are pellet- ellipse- aperture in turn and at last the voids closed. The ratio of compressing on cylinder ingots with void which is close to outer surface is larger than that which is removed. Strain and stress centralize dinstinctly around the voids and in general the shape of centralized area present analogous rose curve. The part of analogous rose curve which is closed to the center of cylinder is larger than the another part if the void in cylinder is not in middle part of cylinder. When more than one voids are in cylinder (two voids for instance), the area of concerfration around the big one is larger than the small one. During hot compressing there are close area of strain andstress in middle part of cylinder with two same dimension voids in it on the whole.An artif ical method of producing successive model with void from grain materials of polycarbonate(PC) through controlling the heating temperature and the speed of temperature elevating was carried out. By appling the photoplastic simulation the way in which the void was closed was described and also pointed out that there was an influented zone around the void whose range was 1-3 times larger than that of the void and the strain distribution within the zone was inhomogeneous on cross section, on longitudinal section the influented zone around the void was analogous rose curve. These deformation characteristic have a good accordance with the results of numerical simulation. The results of 3-D numerical simulation which make use of PC also proved by the results of physical simulation. The combinableness of two kinds of simulation study promote effectively the study about the problem.