| Sintered powder metallurgy materials made by means of a compacting and sintering process from metal and non-metal powders are widely used in many industrial departments. Plastic deformation is a primary way to improve its performance and obtain the final product. Both volume and shape of deformation body will be changed in the course of plastic deformation for sintered powder metallurgy materials. In the paper, based on theoretical analysis and experiments Generalized Upper Bound Element Technique (GUBET) was ascertained for 3D deformation of sintered powder metallurgy materials.Strain-displacement equation and constitutive relationship were introduced and induced respectively. Laws of deformation and densification were analyzed because the volume of deformation body may be compressed. Factors such as deformation strengthening, instantaneous and initial relative densities etc. on the subsequent yield strength are studied, and an approach to determine the plastic stress coefficient and hardening exponent is derived, which is based on the yield criterion and the strengthening laws of plastic deformation of sintered powder materials as well as on a uni-axial compression experiment of a sintered powder material cylinder specimen. A unified form of the yield criterion function is obtained, in which the initial and the subsequent yields of sintered powder materials are expressed.Based on characters of the materials and laws of plastic deformation, Drucker postulate was introduced and Maximum Plastic Work Principle was confirmed for sintered powder metallurgy materials. The extremum theory of plastic deformation was induced. So, theoretical groundwork of GUBET was established.Through analyzing density discontinuity, the conclusion was obtained which the normal velocity discontinuity will occur in the course of deformation of sintered powder metallurgy materials and the influence to energy equation was analyzed from velocity discontinuity, the energy equation is not deal with stress discontinuity, both tangential and normal velocity discontinuity must be expressed in energy equation According to basic definition of GUBET and process characteristics of axisymmetric and non-axisymmetric deformation body respectively, applied field of each kind of element patterns was analyzed under different coordinate system. The localizations of elements under cylindrical coordinate system were pointed out for analyzing non-axisymmetric 3D deformation. Based on mass constancy condition, the kinematically admissible velocity fields of seven types of elements were constructed including cubic and triangular prismatic element under Cartesian coordinate system for 3-D plastic deformation.Total power dissipation model of GUBET were studied and an approach and formula to compute power dissipation due to deformation, shear and friction respectively were obtained for elements of different azimuth and shape. The ways to compute magnitude of tangential and normal velocity discontinuity were suggested.Optimization techniques to flow pattern and boundary condition of element were put forward. Ways were introduced to use mathematical tool in order to optimize expediently velocity fields of GUBET so as to minimize total upper bound power dissipation. Approaches and ways were expressed to solve process problems with GUBET in the engineering fields for example process simulation, densification prediction, forming load programming, etc. An experiment with upsetting of sintered copper cylinder specimen were carried out to verify theoretical predictions with GUBET, the theoretical predictions were in good agreement with experimental values.Analysis and computation pattern were established for hexahedron body upsetting deformation of sintered ferrous materials with GUBET, an experiment was carried out in same materials and process at room temperature. The theoretical solution was in good agreement experimental result, the reliability and feasibility were validated on GUBET.
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