Browsing by Author "Chahaoui"

Now showing 1 - 8 of 8
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    An Associated and Nonassociated Flow Rule Comparison for AISI 439-430TI Forming: Modeling and Experimental Analysis
    (2021-09-21) Chahaoui
    The plastic anisotropy behavior of ferritic stainless steel (FSS) sheets was analyzed and modeled under associated and nonassociated flow rule approaches. Three orthotropic flow functions, known as quadratic Hill48 and nonquadratic (Yld2000-2d and BBC2005), were developed and employed under an associated and nonassociated flow rule hypothesis. For the NAFR based on the initial anisotropy, the mechanical behavior was described by the nonexponential model functions of Yld2000-2d and BBC2005 to predict the directional dependence of mechanical parameters. It provided a considerable advantage in terms of flexibility and good agreement with the experiment. According to the results, the polynomial fit functions of the transverse versus longitudinal true plastic strain curve were used to describe the designated properties corresponding to a selected level of strain. To describe the evolution of anisotropic hardening and potential plastic hardening, seven different loading conditions were considered. The proposed evolutionary non-AFR Yld2000-2d and BBC2005 criteria showed good accuracy in predicting the evolution of hardening yield and Lankford coefficients depending on the plastic deformation.
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    An Evolutionary Anisotropic Behavior for DC04 Sheet Using Hill48 Function under Non-Associated Flow Rule Hypothesis
    (2022-10-28) Chahaoui
    analyzed based on a quadratic Hill48 function and under the application of two plasticity approaches: associated and non-associated flow rule approaches (AFR and NAFR, respectively). The mechanical properties have been modeled, such as the uniaxial flow stresses () and the coefficient of anisotropy r() (or the Lankford parameter). In the identification of anisotropic parameters, the decoupling of the two tensors (strain and stress) under the assumption of non-associated plasticity gives better predictions compared with the experimental. With the purpose of introducing the evolutionary anisotropic path of plastically equivalent characteristics for the uniaxial flow stresses (), the isotropic hardening of mechanical strain hardening function is presented using the following empirical law based on Voce model. Therefore,
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    Application of Associated and Non-Associated Flow Metal Plasticity for F.S.S Sheet
    (2021-01-11) Chahaoui
    In the last decade, several phenomenological yield criteria for anisotropic material has been proposed to improve the modeling predictions about sheet metal-forming processes. In regard to this engineering application, two proprieties of models have been used. If the yield function and the plastic potential are not same (not equal), the normality rule is non associative flow rule (NAFR), otherwise, when the stresses yield has been completely coupled to the anisotropic strain rate ratio (plastic potential), is called the associated flow rule (AFR). The non-associated flow rule is largely adopted to predict a plastic behavior for metal forming, accurately about à strong mechanical anisotropy presents in sheet metal forming processes. However, various studies described the limits of the AFR concept in dealing with highly anisotropic materials. In this study, the quadratic Hill1948 yield criteria is considered to predict mechanical behavior under AFR and NAFR approach. Experiment and modeling predictions behaviour of normalized anisotropic coefficient r (θ) and σ (θ) evolved with θ in sheet plane. and the equibiaxial yield stress σb was assumed σb=1 but the rb-values was computed from Yld96 [15]
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    Constitutive Modelling of an Industrial Rolled Sheet for a DIN 1623 St14 (DC04) Steel
    (2019-09-17) Chahaoui
    The comprehension of the anisotropy impacts on mechanical properties of the rolled steel sheets was investigated using a non-quadratic anisotropic yield function. In this study, experimental and modelling determination of behavior of an industrial rolled sheets for a DIN 1623 St14 steel were carried out. The yield stresses and Lankford r-values in uniaxial were experimentally determined but the balanced biaxial tension stress states and rb were assumed. The parameters of the associated yield equation, derived from the three orthotropic yield functions proposed by Hill48 and Yld2000-2d, were determined. Predictions and the evolution of normalized yield stress and normalized Lankford parameters (plastic strain ratio) obtained by the presented investigative are considered. In order to describe the path of equivalent plastic behavior, the isotropic hardening function is described using the following various empirical standard formulae based on: Hollomon, Ludwick, Swift and Voce model.
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    Experimental Study and Modelling of the Ferritic Steel Anisotropic Behavior under Associated and Non-Associated Flow Rule
    (2021-01-05) Chahaoui
    In the present study, two different yield criteria were investigated to model and compare the yield thresholds functions for the plastic behavior of rolled sheets. These two different yield criteria as described via Hill48 yield quadratic and F. Barlat Yld2000-2d non-quadratic criterion. For this purpose, an experimental device of simple tensile test and the studied material are described. The experimental results in terms of Yield stress and Anisotropic coefficient are estimated from the Associated Flow Rule (AFR) and Non-Associated Flow Rule (NAFR). However, it is found that the criterion of Yld2000-2d is the most appropriate model in comparison with the experimental results.
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    Influence of the carburization time on the structural and mechanical properties of XC20 steel
    (2021-08-21) Chahaoui
    This study focuses on the effect of carburization time on the structural and mechanical properties of low carbon XC20 mild steel (C. Wt.%<0.25). The XC20 steel was carburized with activated carbon with a carbon potential Cp1=1.1%, at 910 °Cat different carburization times of 2, 4 and 6 h. The results obtained show that XC20 steel (non-carburized) has a ferrite-pearlitic structure with a hardness and a Young’s modulus of the order of (150 HV, 26KN/mm2). After carburization, the structure of the carburized layer is transformed in martensite (Fe γ) in which cementite (Fe3C) is imbricated. The depth of the carburized layer and the amount of carbon on the surface gradually increase with increasing carburization time. In addition, the carburized XC20 steel becomes hard and brittle where the hardness and Young’s modulus have been increased for a high holding time until reaching maximum values (845 HV, 48KNmm−2) after 6 h of carburization . However, the toughness of XC20 steel has been reduced from 163 to 40 J cm−2.
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    Modelling Mechanical Properties of AISI 439-430Ti Ferritic Stainless Steel Sheet
    (2019-05-14) Chahaoui
    The comprehension of the anisotropy impacts on mechanical properties of the rolled steel sheets was investigated using a nonquadratic anisotropic yield function. In this study, experimental and modelling determination regarding the behaviour of an industrial rolled sheet for a ferritic stainless low-carbon steel were carried out. The parameters of the associated yield equation, derived from the three orthotropic yield functions proposed by Hill48, Yld96 and Yld2000-2d, were determined. Predictions and the evolution of normalized yield stress and normalized Lankford parameters (plastic strain ratio) obtained by the presented investigative are considered. The forecasts given by the YLD2000-2d criterion are consistent with that of the experience. In order to describe the path of strain behavior, the isotropic hardening function is described using the following four empirical standard formulae based on: Hollomon, Ludwick, Swift and Voce law. More accurately, the anisotropy coefficients of three yield functions are represented as a function of the longitudinal equivalent plastic strain.
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    Three-dimensional transient CFD modeling of multiple finned aluminum foam heat sinks in a horizontal channel
    (2023-07-28) Chahaoui
    Finned metal foam heat sinks are well-known because of their excellent performance in cooling of powered electronics. In this study, three-dimensional transient numerical simulations of finned aluminum foam heat sinks in a forced convection of air were carried out using commercial COMSOL. The geometry under consideration consists of an array of finned aluminum foam heat sinks mounted on heater blocks and placed on a plate in a horizontal channel. Heat sink aluminum foam regions were considered as porous media with a local nonequilibrium thermal model to evaluate thermal characteristics, while the Forchheimer-Brinkman extended Darcy model is considered for the flow analysis. Our main concern in the present study is to evaluate the transient thermal–hydraulic behavior and the cooling performance under constant flux heat sources while varying the Reynolds number and variable morphological parameters of the aluminum foam, i.e., porosity (ε) varied from 0.85 to 0.95. The thermal performance ratio and the average Nusselt number of the finned aluminum foam heat sinks are 23.14% and 30%, respectively, larger than the finned aluminum heat sinks. As the Reynolds number increases, the thermal characteristics are enhanced, and the pressure drop is increased. An increase in porosity causes a reduction in heat transfer rate and an elevation of pressure drop.