Papers by Keyword: Plastic Flow

Abstract: Stress-strain behavior of austenitic stainless steel grade AISI 304 was investigated by means of uniaxial tensile tests and magneto-phase analysis. The test materials were strained in tension within the temperature range of-100 ≤ T ≤ +100 °C. According to the results, intensive strain hardening occurs in austenitic stainless steel when strain-induced α’- martensite is present in the material, and stress-strain behavior is associated with the increase yield strength and tensile strength with decreasing temperature. The analysis of the hardening kinetics reveals that kinetics are affected by the temperature and by the amount of α’- martensite content.

Abstract: The potential of KOBO unconventional extrusion of metallic materials based on phenomenon of changing the path of plastic deformation with use of cyclic oscillation of the die by given angle and frequency has been presented in this paper. This process is used to change material properties by fragmentation of grains without preheating the billet and press parts with significantly lower extrusion force in comparison to conventional process. Various types of billets (various metallic materials in the form of: solid initial material, condensed chips, layered composite material) were used during the experimental tests to analyze the plastic flow of the material and the possibility of plastic deformation of various metallic materials such as aluminum alloys, magnesium alloys and copper in order to obtain a product with a complex shape in the KOBO process, using dies with different geometries. Mechanical properties, microstructure, scheme of plastic flow and extrusion force were examined during experimental work. KOBO extrusion can be considered as a more cost-effective process than conventional extrusion.

Abstract: The metal workpiece Surface Layer (SL) Residual Stresses (RS) modeling and computational algorithms creation relevance is shown. The RS forming discrete elastoplastic finite element model at Surface Plastic Deformation (SPD) hardening treatment, including technological inheritance effect, is presented. A model feature is the complex non-monotonic types of metal loading and subsequent unloading and hardened body effect consideration, as well as residual stress tensor components evaluation as a result of these effects. Residual stress tensor components calculations in the workpiece hardened surface layer after treatment with different routines are performed. The metal hardening effect on the residual stresses values and distribution is established. The correlations between the residual stress tensor components and the main treatment routine parameters - the roller tension and profile radius are established.

Abstract: On the basis of previously accumulated irreversible deformations, and, consequently, residual stresses, the process of removing residual stresses in metal workpieces under the action of low and high temperatures is simulated. Boundary value problems are solved and here are described regularities that are responsible for removing residual stresses for processing modes: high-temperature heating - cooling, high-temperature heating - holding - cooling, low-temperature heating - holding - cooling. The holding stage is modeled, taking into account the creep properties of materials under Norton creep conditions. According to the dependences of the obtained exact solutions, it is shown that it is the holding process that leads to the relaxation of residual stresses.

Abstract: The paper presents the study of the effect of hydrogenation on the mechanical properties of commercially pure titanium. It has been found that the localized deformation zones occurring in the plastically deforming Ti samples are stationary dissipative structures. The kinetics of dissipative structure evolution was studied. The hydrogenation treatment is found to enhance a tendency to strain localization in as-treated material, which affects significantly material strength properties.

Abstract: The problem of shock deforming of elastic-plastic half-space with large deformation was examined. We have obtained that the deformation state can be changed in two types of simple plastic waves and two types of shock elastic waves in the case of self-similar medium motion. The speeds and characteristics of plastic waves were examined. The numerical solution of boundary value problem was found.

Abstract: Low-temperature technological process of residual stresses relief in metals is modeled. The paper presents the mode of a slow heating stage, holding stage at a constant temperature and slow cooling stage. The holding stage is simulated with creeping properties of materials. Boundary problems are examined and patterns that are responsible for the removal of residual stresses are described. In Norton creep conditions we obtained analytical solutions.

Abstract: The effect of hydrogen embrittlement on the localized plastic deformation of aluminum alloy D1 was investigated. The studies were performed for the test samples of aluminum alloy subjected to electrolytic hydrogenation. It is found that the mechanical properties and localized plastic deformation parameters of aluminum alloy are affected adversely by hydrogen embrittlement. The hydrogenated counterpart of alloy has a lower degree of ductility relative to the original alloy; however, the plastic flow behavior of material remains virtually unaffected. The deformation diagrams were examined for the deformed samples of aluminum alloy. These are found to show all the plastic flow stages: the linear, parabolic and pre-failure stages would occur for the respective values of the exponent n from the Ludwik-Holomon equation. Using digital speckle image technique, the local strain patterns were being registered for the original alloy D1 and the counterpart subjected to electrolytic hydrogenation for 100 h.

Abstract: This study aims to develop a cutting method, which enables to generate a localized hydrostatic pressure field in the vicinity of cutting zone in order to improve the machined surface integrity without causing unnecessary plastic deformation. In the previous work, a molecular dynamics simulation was performed using a newly developed cutting tool equipped with a planer jig with a rectangular hole for the cutting chip elimination, and it was confirmed that the developed cutting tool has advantages in giving a relatively high-hydrostatic stress field in the vicinity of the cutting zone and in suppressing the burr formation. In this report, further molecular dynamics simulation was performed in order to clarify the influence of jig shape on the cutting phenomena and machined surface integrity. As a result, it is found that a cutting tool of which front and side except for the rectangular hole are covered by the planer jig is the most advantageous for supplying high hydrostatic pressure and suppressing burr formation.

Abstract: Paper deals with simulation analysis of thermoplastic flowing in plastics product. As there is a demand in plastic products, plastic industries are growing in a fastest rate. Hence plastic injection molding process begins in manufacturing of complex shapes, in this process optimum gate location is one of the important criteria in mold design. Knowledge of ideal flow properties of thermoplastic materials give us a very good starting position for design of thermoplastics products which will be made by injection molding. By simulation software Plastic Advisor was compared injection parameters for the mold with varying gate locations. Simulated thermoplastic product is made from polycarbonate and is using for the drum washing machine as console window.