The Experts below are selected from a list of 102 Experts worldwide ranked by ideXlab platform
Frederic Barlat - One of the best experts on this subject based on the ideXlab platform.
-
Modeling of yield surface evolution in uniaxial and biaxial loading conditions using a preStrained large scale specimen
2018Co-Authors: Shakil Bin Zaman, Frederic BarlatAbstract:Large-scale advanced high strength steel (AHSS) sheet specimens were deformed in uniaxial tension, using a novel grip system mounted on a MTS universal tension machine. After pre-Strain, they were used as a pre-Strained material to examine the anisotropic response in the biaxial tension tests with various load ratios, and orthogonal tension tests at 45° and 90° from the pre-Strain axis. The flow curve and the instantaneous r-value of the pre-Strained steel in each of the aforementioned uniaxial testing conditions were also measured and compared with those of the undeformed steel. Furthermore, an exhaustive analysis of the yield surface was also conducted and the results, prior and post-preStrain were represented and compared. The homogeneous anisotropic hardening (HAH) model [1] was employed to predict the behavior of the pre-Strained material. It was found that the HAH-predicted flow curves after non-Linear Strain Path change and the yield loci after uniaxial pre-Strain were in good agreement with the experiments, while the r-value evolution after Strain Path change was qualitatively well predicted.
-
Deformation-induced anisotropy of uniaxially preStrained steel sheets
International Journal of Solids and Structures, 2017Co-Authors: Shakil Bin Zaman, Frederic BarlatAbstract:Abstract This article investigates the macroscopic behavior of uniaxially pre-Strained large-scale DP780 and CHSP45R sheet specimens. A novel grip system was designed for the pre-Straining of the large tensile specimens. After this first loading, the uniformly Strained gauge-section of the large-scale specimen was machined to smaller standard specimens. After pre-Strain, further uniaxial tension tests at 45° and 90° from the pre-tensile direction, compression test and in-plane biaxial tension tests at 1:1, 2:1 and 1:2 force ratios were conducted. The flow curves and the instantaneous r-values of the pre-Strained steel in the aforementioned uniaxial loading directions were compared with their monotonic response. In addition, the pre-Strained compression test was incorporated to the π-plane at several incremental offset Strains. The yield function- and isotropic hardening-based homogeneous anisotropic hardening (HAH) model (Barlat et al., 2014) was selected to predict the material response after non-Linear Strain Path change. The Swift law characterized the isotropic hardening, while the Yld2000-2d anisotropic yield function (Barlat et al., 2003a) represented the yield locus. All the coefficients of the distortional plasticity model were manually determined and validated with an optimization algorithm. The HAH-predictions of the pre-Strained flow curves and yield loci at several offset Strains were in reasonable agreement with the experimental data, while the instantaneous r-value evolution was qualitatively well captured.
-
Strain hardening response and modeling of eddq and dp780 steel sheet under non Linear Strain Path
Mechanics of Materials, 2013Co-Authors: Jinjin Ha, Frederic BarlatAbstract:Abstract The anisotropic hardening behaviors of dual phase (DP780) and extra deep drawing quality (EDDQ) steel sheets under non-proportional Strain Paths were investigated. Two-step uniaxial tension tests, which consisted of the first loading in the rolling (RD) or transverse (TD) and the second loading in every 15° from the first loading axis, were conducted. For DP780 steel, a significant Bauschinger effect accompanied by a transient hardening behavior after reverse loading was the prominent phenomenon. In contrast, EDDQ exhibited stress overshooting followed by Strain hardening stagnation with respect to the monotonic flow curve near cross-loading conditions. The extended HAH model combined with the Yld2000-2d yield function were used to reproduced the anisotropic hardening behavior of the two materials. For DP780, the extended HAH model could capture the Bauschinger effect and transient hardening behavior well for tension reloading at 0°, 15°, 75° and 90° from the RD or TD preStraining direction. However, the predictions at 30°, 45° and 60° were slightly different from the experiments. For EDDQ, this approach reproduced the Strain hardening anisotropy well including flow stress overshooting followed by a stage of Strain hardening stagnation.
-
Plastic Instability in Complex Strain Paths Predicted by Advanced Constitutive Equations
2011Co-Authors: M.c. Butuc, Frederic Barlat, José Grácio, Gabriela VinczeAbstract:The present paper aims at predicting plastic instabilities under complex loading histories using an advanced sheet metal forming limit model. The onset of localized necking is computed using the Marciniak-Kuczinsky (MK) analysis [1] with a physically-based hardening model and the phenomenological anisotropic yield criterion Yld2000-2d [2]. The hardening model accounts for anisotropic work-hardening induced by the microstructural evolution at large Strains, which was proposed by Teodosiu and Hu [3]. Simulations are carried out for Linear and complex Strain Paths. Experimentally, two deep-drawing quality sheet metals are selected: a bake-hardening steel (BH) and a DC06 steel sheet. The validity of the model is assessed by comparing the predicted and experimental forming limits. The remarkable accuracy of the developed software to predict the forming limits under Linear and non-Linear Strain Path is obviously due to the performance of the advanced constitutive equations to describe with great detail the material behavior. The effect of Strain-induced anisotropy on formability evolution under Strain Path changes, as predicted by the microstructural hardening model, is particularly well captured by the model.
Vadim V. Silberschmidt - One of the best experts on this subject based on the ideXlab platform.
-
Computational assessment of residual formability in sheet metal forming processes for sustainable recycling
International Journal of Mechanical Sciences, 2016Co-Authors: Javad Falsafi, Emrah Demirci, Vadim V. SilberschmidtAbstract:This paper introduces a new computational scheme addressing a problem of cold recyclability of sheet-metal products based on the assessment of their post-manufacture residual formability. Formability of sheet metals has been studied for several decades, and various techniques were suggested since a Forming Limit Diagram was first introduced in the 1960s. At the same time, cold recycling, or re-manufacturing, of sheet metals is an emerging area studied mostly empirically; in its current form, it lacks theoretical foundation. In order to address the challenge of residual formability for sheet-metal products, a reformability index is introduced in this study. The proposed method takes advantage of the latest developments in the area of evaluating multiple-Path formability and introduces a quantitative reformability index for the manufactured material. This index represents possible levels of Strains for deformation along different Paths, based on Polar Effective Plastic Strain (PEPS). PEPS provides robustness against non-Linear Strain-Path effects, thus making a reliable basis for such analysis. Based on residual formability, a predictive model was sought to assess a degrading effect of the flattening process. Taking advantage of extensive numerical simulation, a wide range of geometrical parameters in an unbending process, as a predominant mechanism in flattening, was studied. The reformability index alongside prediction of degradation in flattening allows evaluation of prospective re-manufacturing. The significance of this research is its advancement towards recycling of sheet-metal products without melting them by facilitating design for sustainability. The proposed scheme also provides a subroutine friendly framework for numerical simulations.
D. Guines - One of the best experts on this subject based on the ideXlab platform.
-
Effects of Strain Path Changes on the Kinematics and the Intrinsic Dissipation Accompanying PLC Bands in Al-Mg Alloys
Experimental Mechanics, 2019Co-Authors: L. Leotoing, E. Robin, D. Guines, J.-b. CamAbstract:Plastic instabilities, such as the Portevin-Le Chatelier (PLC) effect, reduce material ductility and induce surface roughness during sheet metal forming. The formation and propagation of PLC bands have been extensively studied by using the uniaxial tension test. However, this Strain state differs from the complex Strain Paths encountered in most metal forming operations. In this work, the Linear and non-Linear Strain Path effects on the kinematics of PLC instabilities are investigated in an AA5086-H111 Al-Mg alloy, at Strain rates between 0.1 and 0.5 s− 1. This is the first study on the spatio-temporal distribution analysis of heat produced by PLC bands during non-Linear loadings. Non-Linear Strain Paths are generated with an innovative one-step procedure, without unloading. The Strain Path changes are controlled by the displacements along the two perpendicular directions of a cruciform specimen loaded with a planar biaxial tensile device. For a given Linear or non-Linear Strain Path, full kinematic and thermal fields on the specimen surface were characterized by using Digital Image Correlation (DIC) and infrared thermography (IRT). Heat source fields were reconstructed from the temperature fields and the heat diffusion equation. The calorimetric response, which mainly corresponds to the intrinsic dissipation produced by the material, permits the kinematics of PLC bands to be investigated. It is shown that the Strain state (uniaxial, plane Strain or equibiaxial) strongly affects the formation and propagation of such plastic instabilities. For each Strain Path, a band typology is clearly identified. For two-step non-Linear Strain Paths, the change in the Strain state induces an instantaneous modification of the kinematics. The band kinematics is directly linked to the current Strain Path and the plastic deformation history does not appear to influence the typology of bands.
-
investigations of the effect of Strain Path changes on forming limit curves using an in plane biaxial tensile test
International Journal of Mechanical Sciences, 2015Co-Authors: L. Leotoing, D. GuinesAbstract:Optimization of sheet metal forming processes requires a very good knowledge of material forming ability, more especially for aluminum alloys which generally exhibit a poor formability at ambient temperature. During the forming of industrial parts, very complex Strain Paths are usually observed and can affect the formability of the sheet. In this work, in order to investigate Strain Path effects on formability, an innovative one-step procedure is proposed to control the Strain Path changes with a single test, without unloading. The test is based on the use of a cruciform shape loaded with a planar biaxial tensile device. Strain Path is controlled by the displacements in the two main directions of the cruciform specimen. For a given non-Linear Strain Path type, experimental forming limit points are greatly influenced by the level of preStrain which can either improve or reduce formability. The same tendency is observed when using a predictive tool based on a finite element model of the same cruciform shape and a rather good correlation is observed between experimental and numerical results.
Javad Falsafi - One of the best experts on this subject based on the ideXlab platform.
-
Computational assessment of residual formability in sheet metal forming processes for sustainable recycling
International Journal of Mechanical Sciences, 2016Co-Authors: Javad Falsafi, Emrah Demirci, Vadim V. SilberschmidtAbstract:This paper introduces a new computational scheme addressing a problem of cold recyclability of sheet-metal products based on the assessment of their post-manufacture residual formability. Formability of sheet metals has been studied for several decades, and various techniques were suggested since a Forming Limit Diagram was first introduced in the 1960s. At the same time, cold recycling, or re-manufacturing, of sheet metals is an emerging area studied mostly empirically; in its current form, it lacks theoretical foundation. In order to address the challenge of residual formability for sheet-metal products, a reformability index is introduced in this study. The proposed method takes advantage of the latest developments in the area of evaluating multiple-Path formability and introduces a quantitative reformability index for the manufactured material. This index represents possible levels of Strains for deformation along different Paths, based on Polar Effective Plastic Strain (PEPS). PEPS provides robustness against non-Linear Strain-Path effects, thus making a reliable basis for such analysis. Based on residual formability, a predictive model was sought to assess a degrading effect of the flattening process. Taking advantage of extensive numerical simulation, a wide range of geometrical parameters in an unbending process, as a predominant mechanism in flattening, was studied. The reformability index alongside prediction of degradation in flattening allows evaluation of prospective re-manufacturing. The significance of this research is its advancement towards recycling of sheet-metal products without melting them by facilitating design for sustainability. The proposed scheme also provides a subroutine friendly framework for numerical simulations.
Jinjin Ha - One of the best experts on this subject based on the ideXlab platform.
-
Strain hardening response and modeling of eddq and dp780 steel sheet under non Linear Strain Path
Mechanics of Materials, 2013Co-Authors: Jinjin Ha, Frederic BarlatAbstract:Abstract The anisotropic hardening behaviors of dual phase (DP780) and extra deep drawing quality (EDDQ) steel sheets under non-proportional Strain Paths were investigated. Two-step uniaxial tension tests, which consisted of the first loading in the rolling (RD) or transverse (TD) and the second loading in every 15° from the first loading axis, were conducted. For DP780 steel, a significant Bauschinger effect accompanied by a transient hardening behavior after reverse loading was the prominent phenomenon. In contrast, EDDQ exhibited stress overshooting followed by Strain hardening stagnation with respect to the monotonic flow curve near cross-loading conditions. The extended HAH model combined with the Yld2000-2d yield function were used to reproduced the anisotropic hardening behavior of the two materials. For DP780, the extended HAH model could capture the Bauschinger effect and transient hardening behavior well for tension reloading at 0°, 15°, 75° and 90° from the RD or TD preStraining direction. However, the predictions at 30°, 45° and 60° were slightly different from the experiments. For EDDQ, this approach reproduced the Strain hardening anisotropy well including flow stress overshooting followed by a stage of Strain hardening stagnation.