http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Latypov, M.I.,Shin, S.,De Cooman, B.C.,Kim, H.S. Elsevier Science 2016 Acta materialia Vol.108 No.-
<P>In the present contribution, a phenomenological constitutive model of medium manganese steels, in which both twinning-induced (TWIP) and transformation-induced (TRIP) plasticity enhancing mechanisms are activated, is implemented in the finite element framework. The implementation is utilized for the analysis of the full-field strain partitioning in dual-phase microstructure maps obtained from electron backscattering diffraction. The results of the finite element analysis suggest that the strain localization in the studied steel has an alternating character. Specifically, in the low strain region, most of the externally imposed deformation is accommodated by the initially softer austenite. The higher strain hardening rate of austenite due to deformation twinning (TWIP effect) and the mechanically-induced transformation to martensite (TRIP effect) results in a shift of the strain localization to ferrite. This alternating strain localization is a key feature that distinguishes the medium manganese TWIP+TRIP steel. It is shown that this alternating strain localization contributes to the superior mechanical behavior of medium manganese TWIP+TRIP steel reported in the literature. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.</P>
Simple Shear Model of Twist Extrusion and Its Deviations
Marat I. Latypov,이명규,Yan Beygelzimer,Roman Kulagin,김형섭 대한금속·재료학회 2015 METALS AND MATERIALS International Vol.21 No.3
Twist extrusion (TE) is a severe plastic deformation method with a potential for commercialization. Advancing TE toward industrial use requires in-depth understanding of deformation during the process and its dependence on processing factors. The helical flow model introduced with the concept of TE provides for a concise description of deformation in the process. To date, however, it was unclear under which conditions the helical flow model yields accurate predictions of deformation in TE. This paper presents a systematic finite-element study performed to identify effects of some key process and material factors on deformation in TE and its departure from the ideal deformation described by the helical flow model. It was found that high strain-hardening rate and friction lead to violations of the assumptions of the helical flow model and that these violations result in departure from the ideal deformation. Deviations from the ideal deformation tend to increase on decreasing the length of the twist channel. Friction effects appear especially critical to be considered for accurate prediction of deformation in TE. Finite-element simulations taking friction into account show good qualitative agreement with earlier marker-insert experiments. The results of the present finite-element study allowed for defining the simple shear model of TE.
Kim, J.G.,Latypov, M.,Pardis, N.,Beygelzimer, Y.E.,Kim, H.S. Scientific and Technical Press ; Elsevier Science 2015 Materials & Design Vol.83 No.-
Recently, simple shear extrusion (SSE) and twist extrusion (TE) are introduced to fabricate ultrafine grained bulk rod metallic materials. The SSE and TE processes generate significant deformation inhomogeneity, with higher and lower strains in the center, respectively, which easily causes mechanical instability of the materials. In this study, to overcome this deformation inhomogeneity problem in SSE and TE, a tandem process of SSE and TE (TST) is suggested. The finite element method is applied for plastic deformation behavior during the TST process. The results demonstrate that the TST process can produce relatively homogeneously deformed materials. In particular, the effects of back pressure and processing order on the plastic deformation behaviors in the TST process are systematically analyzed.
Off-Axis Twist Extrusion for Uniform Processing of Round Bars
Yan Beygelzimer,Roman Kulagin,Marat I. Latypov,Viktor Varyukhin,김형섭 대한금속·재료학회 2015 METALS AND MATERIALS International Vol.21 No.4
The present paper introduces a twist extrusion (TE) process capable of processing of round bars with uniform deformation and reports physical, analytical, and numerical modeling of the process. It is shown that the ability to treat round bars can be achieved by design of special off-axis TE dies in which the axis of the twist surface is displaced from the central axis of the bar being processed. Physical modeling conducted in the current study with plasticine demonstrates the feasibility of off-axis TE. A marker insert technique employed in the physical model reveals that tool-controlled flow (ideal helical flow) of the material is dominant in the process. Analytical model developed in the present study explains why using off-axis TE dies leads to uniform deformation and how this deformation uniformity depends on the die geometry. The main conclusions made upon analytical modeling are confirmed with complement finite element simulations. The simulations also show that the main deformation mode in off-axis TE is simple shear at the intersection planes between the twist and the straight channels of the die. The present paper introduces a twist extrusion (TE) process capable of processing of round bars with uniform deformation and reports physical, analytical, and numerical modeling of the process. It is shown that the ability to treat round bars can be achieved by design of special off-axis TE dies in which the axis of the twist surface is displaced from the central axis of the bar being processed. Physical modeling conducted in the current study with plasticine demonstrates the feasibility of off-axis TE. A marker insert technique employed in the physical model reveals that tool-controlled flow (ideal helical flow) of the material is dominant in the process. Analytical model developed in the present study explains why using off-axis TE dies leads to uniform deformation and how this deformation uniformity depends on the die geometry. The main conclusions made upon analytical modeling are confirmed with complement finite element simulations. The simulations also show that the main deformation mode in off-axis TE is simple shear at the intersection planes between the twist and the straight channels of the die. The simulations also show that the main deformation mode in off-axis TE is simple shear at the intersection planes between the twist and the straight channels of the die.
Jung, J.M.,Kim, J.G.,Latypov, M.I.,Kim, H.S. Scientific and Technical Press ; Elsevier Science 2015 Materials & Design Vol.82 No.-
The local microtexture developments of Cu near the interface of Al-core/Cu-sheath composites during multi-pass caliber rolling are investigated using the finite element method in conjunction with a visco-plastic self-consistent model. Two models with different interfacial conditions between Al and Cu are used in order to investigate the effect of the interfacial condition. The resulting inverse pole figures and difference in ODFs for the different numbers of caliber rolling passes indicate that the Coulomb frictional contact condition between Al and Cu represents the final microtextures better than the fully bonded interfacial condition.