Research On New Technology And Theoretical Of Solid Granules Medium Forming

This study comes from the project of Hebei Province natural science fund "Solidgranules medium forming technology and theoretical research (No. of the project:502177) ". On the basis of the thorough analysis and research on traditional forming, solidgranules medium forming technology (SGMF) is advanced in this paper. It is a newtechnology which adopts solid granules medium instead of rigid punch (or elastomer,liquid) to achieve the bulge forming of tube. It distinguishs the conventional soft-toolforming not only from the sort of the pressure medium used, but also from forming lawsbecause of the difference of the medium. The technology and its theoretical research hadnot been reported over the world. It would have wide applications in the fields of plane,space craft, and car manufacturing industry. The experiment of solid granules medium pressure and the testing equipment wasdesigned and manufactured in this paper. The pressure distributing laws are obtained forthe first time through the experiment. The power law of the solid granules' volume–compressibility is presented;and the load model under the nonuniform inner-pressure——the linear load model and cosine load model. Elastic loading of tube that subjects to thenonuniform inter-pressure is analyzed by elastomechanics and the formulas forcalculating the deformation and stress distribution of initial yield state are gained.The six kinds of typical workpieces and die was designed, experimental testing wasaccomplished, and desired workpieces was obtained by conducting the experiment. Amultitude of experimental data had been obtained for the practical application and thetheoretical analysis of the technology. By plasticity theory research of the forming , theforming model of the thin-walled tube under the nonuniform inter-pressure is known, andanalysis of the stress and the strain of the free forming areas was accomplished, the freeforming area's stress and strain and the laws of the wall thickness had been derived. Totake stainless steel 304 as an example, a comparison between the data gained fromcalculation and those gained from experiment is made. According to the local forming characteristic of the circular arc, the paper proposes twocalculational models of angle-part of keeping close to the die to describe the laws ofangle-part forming. They are slip model having no friction and that having friction.Besides it also bring forward the inner-pressure calculation formulas of the angle-part ofkeeping close to the die when the part of the thin-walled tube deformed. For the first time,it is proved academically that the circular arc radius of the tube had the minimum value asthe tube forming in the quadrate die, i.e. the radius of the circular arc would not be zero,and the calculation formulas are given. According to the elasticity theory, Swift's diffuseinstability theory and Hill's local instability theory, the tube forming limits for wrinkling,buckling and bursting were attained. The bursting limit criterion of short tubes undernonuniform pressure is first time suggested. The theoretical analysis indicates that thedeformation model of long tube only represents that of short tube in the condition that ρ=∞ (ρ is the ration of the length to the radius). The conclusion would be common bysignificant.The experiment of the solid granules medium pressure and the tube forming indicatesthat the theoretical calculation is in good accordance with the practical experiment so thatthe theoretical analysis in the paper is correct. As the reliable basic work for the practicalapplication of solid granules medium forming, it is significant both theoretically andpractically. The experiment has proved that the technology provides an effective approachto solve the problem of tube forming that had low plasticity and is difficult to deform. It ispredicted that the practical application of the technology would bring benefiteconomically to the society.