Plastic strain of powder components in unclosed volumes
Tóm tắt
During free compaction, extrusion, and bending of powder blanks, the material is under conditions of nonuniform stress and strain and is subject to compression and tension. A form of plasticity theory is developed for such a body that includes the tension and compression applied to the material. The trends in this theory form the basis for three technological hot-pressing processes. They have been used to prepare spherical layers for tractor hydraulic pump systems (the component is formed by compaction and at various stages is subject to various deformation schemes: uniaxial tension, free compaction, and hydrostatic nonuniform compression), and the same basis has been applied to gear forks for tractors (forming in a semi-open die in two stages: in the first, the state of stress varies from hydrostatic compression to uniaxial, while in the second the material is densified under conditions of hydrostatic compression), as well as to the polar sprocket for an automobile alternator (the process involves plastic bending of the flat elements, with changes produced under tension and adjustment of the material on a convex free surface followed by compression and densification on a concave one).
Tài liệu tham khảo
G. G. Serdyuk and O. V. Mikhailov, “Simulating plastic strain in powder materials in the presence of a free surface,” Poroshk. Metall., No. 4, 18–22 (1986).
M. B. Shtern, “A model for the deformation of a compressible material with allowance for pore formation. Part 1. Defining equations and loading surface,” Ibid., No. 5, 28–34 (1989).
O. V. Mikhailov and M. B. Shtern, “Incorporating variations in tensile and compression resistance in theories of porous-body plasticity,” Ibid., No. 5, 11–17 (1984).
O. V. Mikhailov, Analysis of the States of Stress and Strain in Powder Blanks during Plastic Deformation in Unclosed Volumes and Optimizing the Technology for Making Complicated Components: Ph. D. Thesis [in Russian], Inst. Probl. Materialovedeniya AN Ukr. SSR, Kiev (1986).
G. G. Serdyuk, B. N. Tashlyk, O. V. Mikhailov, et al., “Analysis of the state of stress and strain in a powder blank on plastic bending and optimizing the technology for making components of complicated shapes,” in: New Powder Materials and Technologies in Engineering [in Russian], Inst. Probl. Materialovedeniya AN Ukr. SSR, Kiev (1988), pp. 20–27.
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I. D. Radomysel'skii, G. G. Serdyuk, E. L. Pechentkovskii, et al., “Hot pressing in making components for engineering,” Poroshk. Metall., No. 12, 46–51 (1979).
N. É. Kortsenshtein, Analysis of the State of Stress and Strain and Development of the Technology for Hot Pressing of Powder Components having Spherical Surfaces: Ph. D. Thesis [in Russian], Kiev (1991).
A. M. Burov, Trends in Consolidation and Forming during Hot Pressing of Powder Blanks in Semi-Open Dies and Use for Making Components with Complicated Shapes: Ph. D. Thesis [in Russian], Kiev (1992).