Papers by Keyword: Equivalent Strain

Abstract: Torsion tests allow studying the rheological properties of materials over a wide range of strain and strain rate values, as well as temperature. A key moment in construction of hardening curves is the interpretation of experimental data, which are usually the torque – angle of twist curves. However, there is a number of independent methods to obtain interpretation of experimental data. In addition, there is no single approach to determining the degree of equivalent strain in torsion test. The aim of this paper is to review existing hardening curves definition methods in torsion test and to examine them with the use of finite element modelling.

Abstract: Commercially pure Al wires are drawn through equal channel angular dies with simultaneous torsion. The wires are deformed up to an equivalent strain of 1 to 4 at room temperature after several passes. The microstructure evolution of the wires is investigated using optical microscopy at both longitudinal and transverse cross sections. A grain refinement to a mean grain size of 10 to 15 μm is achieved by using this process. Finer grain structure is observed at the edge area of the wires due to the non-uniform strain distribution. The micro-hardness measurement indicates that the hardness distribution is inhomogeneous and increasing from a minimum value at the wire centre to a maximum value at the wire edge. Finite element (FE) results show that by using a channel angel of 160° and an initial wire diameter of 4 mm during one pass, an equivalent plastic strain of about 0.4 at the wire centre and 0.9 at the wire edge can be achieved. The most important advantage of this process is the ability to impose continuous severe plastic deformation to wires. This new hybrid process could be used as an industrial method for continuous grain refinement of wires.

Abstract: The Finite Element Method (FEM) is used to analysis multiply asperity sliding contact surface. The various distributions of stress and strain along the asperity contact profile are shown for various pressure, roughness, sliding velocity, friction coefficient, and thermal conductivity. The results show that equivalent strain increases as the friction coefficient decreases. Similar results are found for the shear stress. However, the maxima equivalent stress at the center peak increases as the roughness, thermal conductivity, or loading force increases. Instead of the peak point, maxima equivalent stress and strain can be found at the contact/non-contact interchange point of the contact profile. The equivalent stress and strain increase as the loading force increases. In addition, the normal stress increases as the friction coefficient and loading force increase. The maxima normal stress can be found at the center peak point.

Abstract: Materials with ultrafine grain structure and unique physical and mechanical properties can be obtained by methods of severe plastic deformation, which include asymmetric rolling processes. Asymmetric rolling is a very effective way to create ultrafine grain structures in metals and alloys. Since the asymmetric rolling is a continuous process, it has great potential for industrial production of ultrafine grain structure sheets. Basic principles of asymmetric rolling are described in detail in scientific literature. Focus in the well-known works is on the possibility to control the structure of metal sheets. However the systematic data on the influence of the process parameters (e.g., ratio of rolls velocity mismatch, reduction per pass, friction and diameter of rolls), and the shear strain rate required to achieve a significant grain refinement in asymmetric rolling are lacking. The influence of ratio of rolls velocity mismatch, reduction per pass, friction and the rolls diameter on the distribution of shear strain through the sheet thickness in asymmetric rolling has been studied in DEFORM 2D. The results of the study will be useful for the research of evolution of ultrafine grain structure in asymmetric rolling.

Abstract: In order to increase the useful life of sleeve, improve the organizational structure and reduce costs, ZA alloy materials can be used as a raw material using cold extrusion technology for production. The main content of this paper is simulating the change rules of the equivalent plastic strain, the equivalent stress and the flow in the forming process of ZA alloy in different extrusion speed and friction coefficient condition by finite element technology, making a contrastive study with the extrusion theory, and finding out the most appropriate extrusion processing parameters. The results not only provide sufficient theatrical support for the cold extrusion process of sleeve of ZA alloy, but also offer some new thoughts for the design of extrusion mold.

Abstract: In order to guarantee organization and performance requirements of H-beam, a certain compression ratio is needed from stock to products. This paper choose blank special-shaped billet, using DEFORM finite element software, simulated and analyzed change rule of H-beam equivalent strain when beam blank is cogging. Simulation results show that:The compression ratio is 10.78 from stock to products. The stock dimension meet requirements of from A hole to CCS rolling after BD cogging. The equivalent strain rule during the entire process of beam blank cogging is mainly focus waist and haunch joint.

Abstract: This study with constant shear friction uses DEFORM 2D software to perform FEM simulation of backward extrusion, and compares to SUPERFORM FEM simulation to realize the variations of forming conditions with the punch force and the final cup height. Effects of frictional factor, punch nose face angle, punch nose radius, and punch seizing length on equivalent stress, equivalent strain, velocity field, punch force, and deformed shape can be explored. Meanwhile using both FEM softwares to simulate can realize variations of both models in order to provide the reference of backward extrusion.

Abstract: Obtains the best deep product for the choice suitable blank dimensions, process structure and profile of the oil tank part has been analyzed, and has carried on numerical simulation target-oriented of the box bulkhead by the MSC.SuperForm software. Has studied the influence on blank with different radius of curvature and length to equivalent strain and drawing strength of 304 stainless steels, the optimization obtained the best size, voided flaw arousing because of blank size

Abstract: The low cycle fatigue behavior was experimentally studied with the 3-dimension notched LD8 aluminum alloy specimens at 300°C. The 3- dimension stress-strain responses of specimens were calculated by means of the program ADINA. The multiaxial fatigue life prediction was carried out according to von Mises’s equivalent theory. The results from the prediction showed that the equivalent strain range can be served as the valid mechanics for predicting multiaxial high temperature and low cyclic fatigue life.

Abstract: The high temperature & low cycle fatigue were experimentally studied with the 3-dimension notched 2.25Cr—1Mo steel specimens. The 3-dimension stress-strain responses of specimens were calculated by means of the program ADINA. The prediction method of 3-dimension fatigue life was discussed according to the theory of high temperature strength. The results of experiments and calculations showed that the equivalent strain range can be served as the valid mechanics for predicting fatigue life.