Papers by Keyword: Intensive Plastic Deformation

Abstract: Copper nickel (Cu-Ni) coatings on products from instrumental steel H12M were drawn and they were subjected to subsequent intensive plastic deformation under stresses 3.0; 3.5; 4.0 and 4.5 GPa. The nanostructured surface, formation grains size of 13...173 nm with high-angle (at 3.0; 4.0; 4.5 GPa) and low-angle (dislocation) borders of grains (at 3.5 GPa), influencing redistribution of alloying elements and tribological properties was shown by means of methods of light and electronic microscopy, X-ray diffraction and micro-ray spectral analysis, and also tribological tests.

Abstract: The article considers a new method of sliding bearings inner surface hardening by plastic deformation in complex local loading of deformation zone conditions. The main aspects of experimental equipment construction and experimental research preparation are reviewed. The laboratory research results are presented.

Abstract: Considerable shear strain is necessary for manufacture of metallic materials with ultramicrograin structure. For flat rolling shear strain intensity is determined by two components: compression strain and shear strain . The vertical asymmetric sheet rolling process in rolling-drawing mode was investigated with the purpose of shear strain implementation. Calculation results show that during asymmetric rolling mode a vertical cross-section inclination takes place being especially pronounced with the total amount of deformation of 50% and more.

Abstract: Theoretical solutions for several rigid plastic models used to describe plastic flow in metal forming processes are singular in the vicinity of maximum friction surfaces. In particular, velocity gradients and the equivalent strain rate approach infinity near such surfaces. Such singular behavior can be excluded from consideration by choosing another friction law or material model. However, a different approach is proposed in the present paper. The starting point of this approach is that many experiments show that velocity gradients are very high in the vicinity of surfaces of high friction and that a narrow material layer is formed near such surfaces whose properties are very different from the properties in the bulk. Taking into account that the equivalent strain rate has a significant effect on the evolution of material properties, this experimental fact suggests that a theory based on the singular plastic solutions can be developed to describe the formation of the aforementioned material layer. In the present paper such a theory is proposed to describe the evolution of grain size. It is assumed that, in addition to the equivalent strain rate, the material spin has an effect of the evolution of grain size. It is then shown that the solutions for the material spin are singular as well. The interrelation between the present theory and strain gradient theories of plasticity is discussed. It is shown that it is necessary to account for the strain rate gradient to propose a more adequate theory to deal with the material flow near surfaces of high friction. Some experimental results on the formation of the narrow layer of ultra-fine grains in the vicinity of the fraction surface in extrusion are presented. An illustrative example to relate these experimental results and the new theory is given.

Abstract: Object of researches in the given paper is the technological process of obtaining from carbon steel method equal-channel angular extrusion (ECAE) on one pass. The purpose of theoretical research is the working of recomdations on projection of the process with the help of a designed technique of simulation of process ECAE in CAE systems. Calculations were done under variable conditions ECAE over the range changes of parameters: a corner of intersection of channels Ф from 90 up to 150 grades, speed of driving press from 0,05 m/s up to 0,2 m/s, temperature from 20°С up to 600°С. As a result quantitative links of local parameters (stresses, strains and temperature) are established with geometrical and technological ECAE parameters to one separate pass. Regularities of change of parameters to ECAE process of cylindrical preforms in diameter of 20 mm and 30 mm are established (steel 0,15%С), are investigated; character of change of a tension in the instrument and power conditions of the process was studied.