The Experts below are selected from a list of 31335 Experts worldwide ranked by ideXlab platform
R Naghdabadi - One of the best experts on this subject based on the ideXlab platform.
-
experimental and numerical investigation of pulse shaped split hopkinson pressure bar test
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2012Co-Authors: R Naghdabadi, M J Ashrafi, J ArghavaniAbstract:Employing a proper pulse shaper in the conventional split Hopkinson pressure bar (SHPB) test helps to achieve dynamic equilibrium condition and to fulfill a constant strain rate condition in the test specimen. To this end, the parameters affecting the incident pulse shape, i.e., pulse shaper thickness, pulse shaper diameter, striker bar length and striker bar velocity are experimentally studied. Moreover, simulation results, validated by experimental data together with wave propagation analysis, are exploited to provide general guidelines to properly design a pulse shaper. It is recommended to use a relatively large diameter pulse shaper for testing work-Hardening Materials. Also, for different test conditions, e.g., striker bar velocity, it is recommended to scale the pulse shaper thickness and cross-sectional area proportional to the striker bar velocity. Employing these guidelines considerably reduce the try and error process for selecting proper pulse shaper. Finally, to show the effectiveness of the proposed guidelines in practice, SHPB experiments on copper and cast iron specimens are performed. The results show that the variation of strain rate in the specimens is reduced significantly when a proper pulse shaper is employed.
-
nonlinear plastic modeling of Materials based on the generalized strain rate tensor
ASME 2008 Pressure Vessels and Piping Conference, 2008Co-Authors: Kamyar Ghavam, R NaghdabadiAbstract:In this paper, a method for modeling of elastic-plastic Hardening Materials under large deformations is proposed. In this model the generalized strain rate tensor is used. Such a tensor is obtained on the basis of the method which was introduced by the authors. Based on the generalized strain rate tensor, a flow rule, a Prager-type kinematic Hardening equation and a kinematic decomposition is proposed and the governing equations for such Materials are obtained. As an application, the governing equations for the simple shear problem are solved and some results are compared with those in the literature.Copyright © 2008 by ASME
-
elastic plastic modeling of Hardening Materials using a corotational rate based on the plastic spin tensor
ASME 2007 Pressure Vessels and Piping Conference, 2007Co-Authors: Kamyar Ghavam, R NaghdabadiAbstract:In this paper based on the multiplicative decomposition of the deformation gradient, the plastic spin tensor and the plastic spin corotational rate are introduced. Using this rate (and also log-rate), an elastic-plastic constitutive model for Hardening Materials are proposed. In this model, the Armstrong-Frederick kinematic Hardening and the isotropic Hardening equations are used. The proposed model is solved for the simple shear problem with the material properties of the stainless steel SUS 304. The results are compared with those obtained experimentally by Ishikawa [1]. This comparison shows a good agreement between the results of proposed theoretical model and the experimental data. As another example, the Prager kinematic Hardening equation is used. In this case, the stress results are compared with those obtained by Bruhns et al. [2], in which they used the additive decomposition of the strain rate tensor.Copyright © 2007 by ASME
-
elastic plastic modeling of the Hardening Materials based on an eulerian strain tensor and a proper corotational rate
ASME 2005 Pressure Vessels and Piping Conference, 2005Co-Authors: R Naghdabadi, Kamyar GhavamAbstract:In this paper a model for analyzing elastic-plastic kinematic Hardening Materials is introduced, based on the additive decomposition of the corotational rate of an Eulerian strain tensor In this model, the elastic constitutive equation as well as the flow rule and the Hardening equation is expressed in terms of the elastic and plastic parts of the corotational rate of the mentioned Eulerian stain tensor and its conjugate stress tensor. In the flow rule, the plastic part of the corotational rate of the Eulerian strain tensor is related to the difference of the deviatoric part of the conjugate stress and the back stress tensors. A proportionality factor is used in this flow rule which must be obtained from a consistency condition based on the von Mises yield criterion. A Prager type kinematic Hardening model is used which relates the corotational rate of the back stress tensor to the plastic part of the corotational rate of the Eulerian strain tensor. Also in this paper a proper corotational rate corresponding to the Eulerian strain tensor is introduced. Finally the governing equations for the analysis of elastic-plastic kinematic Hardening Materials are obtained. As an application, these governing equations are solved numerically for the simple shear problem and the stress and back stress components are plotted versus the shear displacement. The results are compared with those, which are available in the literature.Copyright © 2005 by ASME
-
elastic plastic modeling of kinematic Hardening Materials based on f fefp decomposition and the logarithmic strain tensor
Volume!, 2004Co-Authors: Kamyar Ghavam, R NaghdabadiAbstract:In this paper, based on the multiplicative decomposition of the deformation gradient tensor an elastic-plastic modeling of kinematic Hardening Materials is introduced. In this model, the elastic constitutive equation as well as the flow rule and Hardening equation are expressed in terms of the corotational rate of the elastic and plastic logarithmic strains. As an application, the simple shear problem is solved and the stress components are plotted versus shear displacement for a kinematic Hardening material.© 2004 ASME
J Arghavani - One of the best experts on this subject based on the ideXlab platform.
-
experimental and numerical investigation of pulse shaped split hopkinson pressure bar test
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2012Co-Authors: R Naghdabadi, M J Ashrafi, J ArghavaniAbstract:Employing a proper pulse shaper in the conventional split Hopkinson pressure bar (SHPB) test helps to achieve dynamic equilibrium condition and to fulfill a constant strain rate condition in the test specimen. To this end, the parameters affecting the incident pulse shape, i.e., pulse shaper thickness, pulse shaper diameter, striker bar length and striker bar velocity are experimentally studied. Moreover, simulation results, validated by experimental data together with wave propagation analysis, are exploited to provide general guidelines to properly design a pulse shaper. It is recommended to use a relatively large diameter pulse shaper for testing work-Hardening Materials. Also, for different test conditions, e.g., striker bar velocity, it is recommended to scale the pulse shaper thickness and cross-sectional area proportional to the striker bar velocity. Employing these guidelines considerably reduce the try and error process for selecting proper pulse shaper. Finally, to show the effectiveness of the proposed guidelines in practice, SHPB experiments on copper and cast iron specimens are performed. The results show that the variation of strain rate in the specimens is reduced significantly when a proper pulse shaper is employed.
R Luri - One of the best experts on this subject based on the ideXlab platform.
-
comparison between finite element method and analytical methods for studying wire drawing processes
Journal of Materials Processing Technology, 2005Co-Authors: C J Luis, J Leon, R LuriAbstract:Abstract Wire drawing is one of the most commonly used processes for obtaining wire used in mechanical applications such as: rivets, screws, welding wires, etc. In this work, several analytical methods have been employed in order to obtain the forces, energies, stresses and strains that are involved in the process. A comparative study between analytical methods and FEM results is presented, considering Hardening strain Materials. The material selected to carry out those analyses was an aluminium alloy AA-5083, whose flow stress was determined by an appropriate tension test. The geometric property of axisymmetry has been used in order to reduce the computational cost in the finite element simulations, and to simplify the equations for the rest of the methods introduced. The energies involved in wire drawing processes are also determined. Moreover, energies involved in the process are studied for both strain Hardening and non-strain Hardening Materials.
Changzheng Cheng - One of the best experts on this subject based on the ideXlab platform.
-
complete elastic plastic stress asymptotic solutions near general plane v notch tips
Applied Mathematical Modelling, 2020Co-Authors: Bin Hu, Zongjun Hu, Cong Li, Changzheng ChengAbstract:Abstract An efficient method is developed to determine the multiple term eigen-solutions of the elastic-plastic stress fields at the plane V-notch tip in power-law Hardening Materials. By introducing the asymptotic expansions of stress and displacement fields around the V-notch tip into the fundamental equations of elastic-plastic theory, the governing ordinary differential equations (ODEs) with the stress and displacement eigen-functions are established. Then the interpolating matrix method is employed to solve the resulting nonlinear and linear ODEs. Consequently, the first four and even more terms of the stress exponents and the associated eigen-solutions are obtained. The present method has the advantages of greater versatility and high accuracy, which is capable of dealing with the V-notches with arbitrary opening angle under plane strain and plane stress. In the present analysis, both the elastic and the plastic deformations are considered, thus the complete elastic and plastic stress asymptotic solutions are evaluated. Numerical examples are shown to demonstrate the accuracy and effectiveness of the present method.
Kamyar Ghavam - One of the best experts on this subject based on the ideXlab platform.
-
nonlinear plastic modeling of Materials based on the generalized strain rate tensor
ASME 2008 Pressure Vessels and Piping Conference, 2008Co-Authors: Kamyar Ghavam, R NaghdabadiAbstract:In this paper, a method for modeling of elastic-plastic Hardening Materials under large deformations is proposed. In this model the generalized strain rate tensor is used. Such a tensor is obtained on the basis of the method which was introduced by the authors. Based on the generalized strain rate tensor, a flow rule, a Prager-type kinematic Hardening equation and a kinematic decomposition is proposed and the governing equations for such Materials are obtained. As an application, the governing equations for the simple shear problem are solved and some results are compared with those in the literature.Copyright © 2008 by ASME
-
elastic plastic modeling of Hardening Materials using a corotational rate based on the plastic spin tensor
ASME 2007 Pressure Vessels and Piping Conference, 2007Co-Authors: Kamyar Ghavam, R NaghdabadiAbstract:In this paper based on the multiplicative decomposition of the deformation gradient, the plastic spin tensor and the plastic spin corotational rate are introduced. Using this rate (and also log-rate), an elastic-plastic constitutive model for Hardening Materials are proposed. In this model, the Armstrong-Frederick kinematic Hardening and the isotropic Hardening equations are used. The proposed model is solved for the simple shear problem with the material properties of the stainless steel SUS 304. The results are compared with those obtained experimentally by Ishikawa [1]. This comparison shows a good agreement between the results of proposed theoretical model and the experimental data. As another example, the Prager kinematic Hardening equation is used. In this case, the stress results are compared with those obtained by Bruhns et al. [2], in which they used the additive decomposition of the strain rate tensor.Copyright © 2007 by ASME
-
elastic plastic modeling of the Hardening Materials based on an eulerian strain tensor and a proper corotational rate
ASME 2005 Pressure Vessels and Piping Conference, 2005Co-Authors: R Naghdabadi, Kamyar GhavamAbstract:In this paper a model for analyzing elastic-plastic kinematic Hardening Materials is introduced, based on the additive decomposition of the corotational rate of an Eulerian strain tensor In this model, the elastic constitutive equation as well as the flow rule and the Hardening equation is expressed in terms of the elastic and plastic parts of the corotational rate of the mentioned Eulerian stain tensor and its conjugate stress tensor. In the flow rule, the plastic part of the corotational rate of the Eulerian strain tensor is related to the difference of the deviatoric part of the conjugate stress and the back stress tensors. A proportionality factor is used in this flow rule which must be obtained from a consistency condition based on the von Mises yield criterion. A Prager type kinematic Hardening model is used which relates the corotational rate of the back stress tensor to the plastic part of the corotational rate of the Eulerian strain tensor. Also in this paper a proper corotational rate corresponding to the Eulerian strain tensor is introduced. Finally the governing equations for the analysis of elastic-plastic kinematic Hardening Materials are obtained. As an application, these governing equations are solved numerically for the simple shear problem and the stress and back stress components are plotted versus the shear displacement. The results are compared with those, which are available in the literature.Copyright © 2005 by ASME
-
elastic plastic modeling of kinematic Hardening Materials based on f fefp decomposition and the logarithmic strain tensor
Volume!, 2004Co-Authors: Kamyar Ghavam, R NaghdabadiAbstract:In this paper, based on the multiplicative decomposition of the deformation gradient tensor an elastic-plastic modeling of kinematic Hardening Materials is introduced. In this model, the elastic constitutive equation as well as the flow rule and Hardening equation are expressed in terms of the corotational rate of the elastic and plastic logarithmic strains. As an application, the simple shear problem is solved and the stress components are plotted versus shear displacement for a kinematic Hardening material.© 2004 ASME
