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Kengo Yoshida - One of the best experts on this subject based on the ideXlab platform.
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micromechanical modeling of the work Hardening Behavior of single and dual phase steels under two stage loading paths
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2011Co-Authors: Kengo Yoshida, Renald Brenner, B Bacroix, S BouvierAbstract:Work-Hardening Behavior of single-phase steel and dual-phase steel which is made of hard martensite surrounded by soft ferrite is analyzed by using an elastoplastic crystal plasticity model in conjunction with the incremental self-consistent model. Two-stage loading paths consisting of uniaxial tension, unloading and subsequent uniaxial tension/compression for various directions are applied. Bauschinger effect and transitional re-yielding Behavior, which depends on the direction of the second loading path, are predicted and analyzed with respect to the distribution of the residual resolved shear stresses within the material. These features, which are caused by the inhomogeneity of the residual stress field, are especially pronounced in the case of the dual-phase steel because of the strong mechanical contrast between ferrite and martensite phases.
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forming limit stresses predicted by phenomenological plasticity theories with anisotropic work Hardening Behavior
International Journal of Plasticity, 2008Co-Authors: Kengo Yoshida, Noriyuki SuzukiAbstract:Abstract Forming limit stresses of sheet metals subjected to linear and combined stress paths are analyzed using the M-K model in conjunction with two anisotropic work-Hardening models: a work-Hardening model which is capable of describing Bauschinger and cross-Hardening effects, and a work-Hardening model which cannot predict the cross-Hardening effect. It is found that the forming limit stress is path-independent when the stress–strain curves for the linear and combined stress paths agree well with each other. On the other hand, the forming limit stress for the combined stress path depends on the strain path when the prestrain changes the subsequent stress–strain relation. We conclude that the stress-based forming limit criterion is efficient only for a material with a work-Hardening Behavior that is not affected by strain path change. The influence of the work-Hardening Behavior on the forming limit stress is discussed in detail.
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Effect of strain Hardening Behavior on forming limit stresses of steel tube subjected to nonproportional loading paths
International Journal of Plasticity, 2007Co-Authors: Kengo Yoshida, Toshihiko KuwabaraAbstract:Abstract The strain path dependence of forming limit strains and stresses of a steel tube subjected to combined axial load and internal pressure are investigated for linear and combined stress paths using a tension–internal pressure testing machine. The combined stress paths consist of two (first and second) linear stress paths and include unloading between the first and second loadings. The strain Hardening Behavior of the steel tube for many linear and combined stress paths is observed in terms of equivalent stress–equivalent plastic strain ( σ ¯ – e ¯ ) curves. The forming limit stresses for the linear and some combined stress paths fall on a single curve in stress space irrespective of the stress paths when the corresponding σ ¯ – e ¯ curves observed for the given stress paths are on a single curve. On the other hand, the forming limit stresses for some combined stress paths are lower than those for the linear stress paths when the specimen exhibits a low strain Hardening rate immediately after the change in stress paths. It is, therefore, concluded that the forming limit stress of the steel tube is not fully path-independent, and that the path dependence of forming limit stress is strongly affected by the strain Hardening Behavior of the material for given loading paths.
Myoung-gyu Lee - One of the best experts on this subject based on the ideXlab platform.
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enhancement in the modeling of temperature and strain rate dependent plastic Hardening Behavior of a sheet metal
Steel Research International, 2015Co-Authors: Dohyun Leem, Frederic Barlat, Myoung-gyu Lee, Hyukjong Bong, J H Song, Daeyong KimAbstract:In the present study, viscoplastic Hardening Behavior of aluminum alloy 3003 sheet was measured and existing Hardening models were evaluated in terms of the accuracy for predicting strain rate and temperature-dependent flow Behaviors. Moreover, a modified Hardening model was proposed to capture the flow stress–strain responses under various strain rates and temperatures with enhanced accuracy. Mechanical responses of the material were measured by using uniaxial tensile test at various temperature (≈25–250 °C) and strain rates (≈0.001–0.3 s−1), and the split Hopkinson pressure bar (SHPB) test was also conducted to obtain flow Behavior at the strain rate over 700 s−1 at room temperature. Based on these experimental data, two well accepted viscoplastic constitutive models—Johnson–Cook and Khan–Huang–Liang—were evaluated. Finally, the Hollomon/Voce type model was further developed, which resulted in significant improvement in predicting the flow stress curves under wide range of strain rate and temperature.
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evaluating the significance of Hardening Behavior and unloading modulus under strain reversal in sheet springback prediction
International Journal of Mechanical Sciences, 2013Co-Authors: Shunlai Zang, Myoung-gyu Lee, Ji Hoon KimAbstract:Abstract Springback is one of the most important problems that should be compensated in sheet metal forming process with the increasing application of advanced high strength steels and light-weight alloys. In the finite element analyses for the springback, accurate modeling of Bauschinger effect, transient Behavior and permanent softening under cyclic loading has been recognized as the most critical Hardening Behavior in the constitutive modeling aspect. However, if parts of these Hardening Behavior are not well modelled, is the accuracy of springback prediction seriously deteriorated? To answer this question, in this paper the significance of Bauschinger effect and transient Behavior, permanent softening and unloading modulus in springback prediction were estimated using the springback problem of U-draw/bending simulations proposed at Numisheet2011 Benchmark. A recent anisotropic non-linear kinematic (ANK) model [Zang S, Guo C, Thuillier S, Lee M. A model of one-surface cyclic plasticity and its application to springback prediction. Int J Mech Sci 2011;53:425–35.] was adopted to estimate the significance of Hardening Behavior and unloading modulus because of its special feature. The ANK model can predict exactly the same monotonous stress–strain curves for different Hardening schemes, while different Bauschinger effect and transient Behavior under one-dimensional cyclic loading can be also modelled. This feature is quite suitable to quantitatively evaluate the effects of the aforementioned Hardening Behaviors in springback prediction. Initial anisotropy is described by the anisotropic yield function Yld2000-2d. The unloading Behavior is also considered by defining Young's modulus as a function of equivalent plastic strain. Several quantitative analyses were carried out to distinguish the effect of each Hardening component and unloading elastic modulus scheme. Finally, the predicted springback by different models were compared with experiments for both as-received and pre-strained DP780 steel sheets.
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Characterization of the post-necking strain Hardening Behavior using the virtual fields method
International Journal of Solids and Structures, 2013Co-Authors: Jin-hwan Kim, A. Serpantié, Fabrice Pierron, Myoung-gyu LeeAbstract:AbstractThe present study aims at characterizing the post-necking strain Hardening Behavior of three sheet metals having different Hardening Behavior. Standard tensile tests were performed on sheet metal specimens up to fracture and heterogeneous logarithmic strain fields were obtained from a digital image correlation technique. Then, an appropriate elasto-plastic constitutive model was chosen. Von Mises yield criterion under plane stress and isotropic Hardening law were considered to retrieve the relationship between stress and strain. The virtual fields method (VFM) was adopted as an inverse method to determine the constitutive parameters by calculating the stress fields from the heterogeneous strain fields. The results show that the choice of a Hardening law which can describe the Hardening Behavior accurately is important to derive the true stress–strain curve. Finally, post-necking Hardening Behavior was successfully characterized up to the initial stage of localized necking using the VFM with Swift and modified Voce laws
Nader Parvin - One of the best experts on this subject based on the ideXlab platform.
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the effect of intercritical heat treatment temperature on the tensile properties and work Hardening Behavior of ferrite martensite dual phase steel sheets
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2009Co-Authors: P Movahed, M Pouranvari, S Kolahgar, S P H Marashi, Nader ParvinAbstract:Abstract This paper aims to investigate tensile properties and work Hardening Behavior of dual phase (DP) steels. A series of DP steels containing ferrite and martensite with different volume fractions of martensite ( V m ) were produced by intercritical heat treatment. Microstructural investigations, hardness test and tensile test were carried out. Hardness, yield strength, ultimate tensile strength, ductility and fracture energy were correlated to martensite volume fraction. The experimental results showed that dual phase steels with an equal amount of ferrite and martensite have excellent mechanical properties in terms of tensile strength, ductility and fracture energy. A further increase in V m was found to decrease tensile strengths and ductility. The increasing and then decreasing trend in tensile strength is in contrast to the law of mixture. These unusual Behaviors are discussed and explained. Work Hardening Behavior was analyzed in terms of Holloman analysis. Results showed that in DP steels with less than 50% V m , the work Hardening took place in one stage and the work Hardening exponent increased with increasing V m . By increasing the volume fraction of martensite ( V m > 50%) two work Hardening stages were observed in the Hollomon analysis.
Lipeng Ding - One of the best experts on this subject based on the ideXlab platform.
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effect of ag and cu additions on natural aging and precipitation Hardening Behavior in al mg si alloys
Journal of Alloys and Compounds, 2017Co-Authors: Yaoyao Weng, Lipeng DingAbstract:Abstract The effects of Ag and/or Cu additions on the natural aging and precipitation Hardening Behavior of Al-Mg-Si alloys were investigated by using hardness test, differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). Both Ag and Cu additions enhanced the Hardening kinetics of Al-Mg-Si alloys during natural aging (NA) and artificial aging (AA) treatments. The strong interaction of Cu, Ag and Mg atoms is responsible for the improved precipitation kinetics of these alloys, resulting in a refinement of clusters and precipitates. The stronger interaction between Ag and Mg results in lower T4 hardness and higher AA hardness, compared to Cu. This is potentially beneficial for automobile applications where rapid Hardening during paint baking is required. Both Ag and Cu additions reduce the detrimental effect of NA on subsequent AA, due to the formation of Ag or Cu-containing clusters. The clear advantage of Ag addition, compared to Cu, is the improvement of precipitation Hardening response of Al-Mg-Si alloys.
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effect of ag and cu additions on natural aging and precipitation Hardening Behavior in al mg si alloys
Journal of Alloys and Compounds, 2017Co-Authors: Yaoyao Weng, Lipeng DingAbstract:Abstract The effects of Ag and/or Cu additions on the natural aging and precipitation Hardening Behavior of Al-Mg-Si alloys were investigated by using hardness test, differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). Both Ag and Cu additions enhanced the Hardening kinetics of Al-Mg-Si alloys during natural aging (NA) and artificial aging (AA) treatments. The strong interaction of Cu, Ag and Mg atoms is responsible for the improved precipitation kinetics of these alloys, resulting in a refinement of clusters and precipitates. The stronger interaction between Ag and Mg results in lower T4 hardness and higher AA hardness, compared to Cu. This is potentially beneficial for automobile applications where rapid Hardening during paint baking is required. Both Ag and Cu additions reduce the detrimental effect of NA on subsequent AA, due to the formation of Ag or Cu-containing clusters. The clear advantage of Ag addition, compared to Cu, is the improvement of precipitation Hardening response of Al-Mg-Si alloys.
Ranjit Kumar Ray - One of the best experts on this subject based on the ideXlab platform.
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a new empirical equation to describe the strain Hardening Behavior of steels and other metallic materials
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2021Co-Authors: Avala Lavakumar, Soumya Sourav Sarangi, Venkat Chilla, D Narsimhachary, Ranjit Kumar RayAbstract:Abstract The strain Hardening Behavior of five different steels of varying carbon content, ranging between 0.007 and 0.71%, such as an Interstitial free (IF), a microalloyed, and a low, medium and high carbon steels, have been critically examined using tensile loading. The test results for the IF and the microalloyed steels having only ferritic structure, exhibit a two-stage strain Hardening Behavior. On the other hand, the low, medium, and high carbon steels having a two-phase microstructure (ferrite-pearlite/cementite) exhibit three-stage strain Hardening. A number of existing and frequently used empirical equations, such as the Hollomon, Ludwik, Ludwigson and Voce were used to explain the strain-Hardening characteristics of these steels; however, none of the above could fully and satisfactorily explain the flow Behavior especially at high strain region. In order to remedy this deficiency, a modification to Ludwigson equation has been suggested by the authors by introducing an extra exponential term to the existing Ludwigson equation. The modelled flow curves, on the basis of this proposed new equation, could explain the strain Hardening Behavior of these steels very satisfactorily over the entire strain range. In addition, the excellent matching of the flow curves, based on the proposed equation with the experimental flow curves of a number of metallic materials, as diverse as multiphase steel, TRIP-assisted steel, dual-phase steel, stainless steel (316L), Mg-alloy, Ti-alloy and a high entropy (Cantor) alloy, indicates its wider applicability.
