The Experts below are selected from a list of 12717 Experts worldwide ranked by ideXlab platform

David Ryckelynck - One of the best experts on this subject based on the ideXlab platform.

  • Crystal plasticity modeling of the cyclic behavior of polycrystalline aggregates under non-symmetric uniaxial loading: Global and local analyses
    International Journal of Plasticity, 2020
    Co-Authors: Harris Farooq, Georges Cailletaud, Samuel Forest, David Ryckelynck
    Abstract:

    Abstract When a sample is cyclically loaded under a mean Stress or strain, incremental strain ratcheting or mean Stress relaxation phenomena are usually observed. Experiments show that for metallic materials there is generally no full mean Stress relaxation as well as saturation of macroscopic strain ratcheting. In contrast, most macroscopic constitutive models produce both quantities in excess, and complex sets of additional internal variables must be introduced to improve the modeling. Little attention has been paid to model such phenomena using polycrystal aggregates especially going up to the regime of cyclic mechanical stability. In this work based on an elementary crystal plasticity model for FCC crystals and large scale finite element simulations, it is shown that the interaction between different grains is sufficient to cater for such complex phenomena. Light is shed on how different regions of the polycrystal accommodate each other and how the classical definition of constant rate strain ratcheting or a zero mean Stress is nearly impossible to apply to a polycrystalline aggregate. In addition, it is shown that even if a macroscopic stable Hysteresis Stress strain loop is observed, ratcheting phenomena can still be observed at the local scale. The distributions of different constitutive quantities within a polycrystal are also analyzed which gives a new insight into what is happening inside a polycrystal in terms of Stress and strain redistribution. In particular, the existence of evolving bimodal distributions of Stress and accumulated plastic strain is evidenced and related to the occurrence of plastic shakedown and incomplete mean Stress relaxation. Two numerical criteria to detect strain ratcheting are finally proposed and discussed.

  • Crystal plasticity modeling of the cyclic behavior of polycrystalline aggregates under non-symmetric uniaxial loading: Global and local analyses
    International Journal of Plasticity, 2019
    Co-Authors: Harris Farooq, Georges Cailletaud, Samuel Forest, David Ryckelynck
    Abstract:

    When a sample is cyclically loaded under a mean Stress or strain, incremental strain ratcheting or mean Stress relaxation phenomena are usually observed. Experiments show that for metallic materials there is generally no full mean Stress relaxation as well as saturation of macroscopic strain ratcheting. In contrast, most macroscopic constitutive models produce both quantities in excess, and complex sets of additional internal variables must be introduced to improve the modeling. Little attention has been paid to model such phenomena using polycrystal aggregates especially going up to the regime of cyclic mechanical stability. In this work based on an elementary crystal plasticity model for FCC crystals and large scale finite element, it is be shown that the interaction between different grains is sufficient to cater for such complex phenomena. Light is shed on how different regions of the polycrystal accommodate each other and how the classical definition of constant rate strain ratcheting or a zero mean Stress is nearly impossible to apply to a polycrystalline aggregate. In addition, it is shown that even if a macroscopic stable Hysteresis Stress strain loop is observed, ratcheting phenomena can still be observed at the local scale. The distributions of different constitutive quantities within a polycrystal are also analyzed which gives a new insight into what is happening inside a polycrystal in terms of Stress and strain redistribution. In particular, the existence of evolving bimodal distributions of Stress and accumulated plastic strain is evidenced and related to the occurrence of plastic shakedown and incomplete mean Stress relaxation. Two numerical criteria to detect strain ratcheting are finally proposed and discussed.

  • Crystal plasticity modeling of the cyclic behavior of polycrystalline aggregates under non-symmetric uniaxial loading: Global and local analyses
    2019
    Co-Authors: Harris Farooq, Georges Cailletaud, Samuel Forest, David Ryckelynck
    Abstract:

    When a geometry is cyclically loaded under a mean Stress or strain, incremental strain ratcheting or mean Stress relaxation are observed. Experiments shows that for metallic materials there is non-zero mean Stress as well as saturation of macroscopic strain ratcheting, and most macroscopic models produce both quantities in excess. Little attention has been paid to model such phenomena using polycrystal aggregates especially going up to the regime of cyclic mechanical stability. In this paper it will be shown that the interaction between different grains is enough to cater for such complex phenomena using crystal plasticity models for FCC crystals. Light will be shed on how different regions accommodate each other and how the classical definition of constant rate strain ratcheting or a zero mean Stress is nearly impossible in a virtual polycrystal. More importantly, it will be shown that even if there is a macroscopic stable Hysteresis Stress strain loop, local stabilization is not guaranteed. The distribution of different constitutive quantities within a polycrystal are also analyzed which give a new insight into what is happening inside a polycrystal. Specifically, within a polycrystal, accumulated plasticity divides into two parts, and it is postulated that this division of plasticity gives the material its capability to retain its cyclic mean Stress or a saturating ratcheting strain. Two numerical tests to detect strain ratcheting will also be presented. To go up to asymptotic values, as well as to get an unbiased solution a strictly rate-independent model will be used.

Fathi H. Ghorbel - One of the best experts on this subject based on the ideXlab platform.

  • Differential Hysteresis modeling of a shape memory alloy wire actuator
    IEEE ASME Transactions on Mechatronics, 2005
    Co-Authors: Sushant M. Dutta, Fathi H. Ghorbel
    Abstract:

    In this paper, we develop a complete mathematical model of a shape memory alloy (SMA) wire actuated by an electric current and a bias spring. The operation of the SMA actuator involves different physical phenomena, such as heat transfer, phase transformation with temperature Hysteresis, Stress-strain variations and electrical resistance variation accompanying the phase transformation. We model each of these phenomena in a modular fashion. A key feature of the proposed model is that one or more of its modules can be extended to fit other SMA applications. At the heart of the proposed model is a differential Hysteresis model capable of representing minor Hysteresis loops. We generate the temperature profile for the Hysteresis model using lumped parameter analysis. We extend the variable sublayer model to represent actuator strain and electrical resistance. This model can be used to develop a position control system for the actuator. Simulation results from the model are found to be in good agreement with experimental data.

  • Dynamic Modeling and Control of Hysteresis in a Shape Memory Alloy Actuator
    Dynamic Systems and Control Parts A and B, 2004
    Co-Authors: Sushant M. Dutta, Fathi H. Ghorbel, James B. Dabney
    Abstract:

    In this paper, we develop a complete mathematical model of a shape memory alloy (SMA) wire actuated by electric power and a bias spring. The operation of the SMA actuator involves different physical phenomena, such as heat transfer, phase transformation with temperature Hysteresis, Stress–strain variations and electrical resistance variation accompanying the phase transformation. We model each of these phenomena in a modular fashion. A key feature of the proposed model is that one or more of its modules can be extended to fit other SMA applications. At the heart of the proposed model is a dynamic Hysteresis model capable of representing minor Hysteresis loops. We generate the temperature profile for the Hysteresis model using lumped parameter analysis. We extend the variable sublayer model to represent actuator strain and electrical resistance. The dynamic properties of the Hysteresis model are developed and are exploited in developing control system strategies. Control simulation case studies are presented.Copyright © 2004 by ASME

Sushant M. Dutta - One of the best experts on this subject based on the ideXlab platform.

  • Differential Hysteresis modeling of a shape memory alloy wire actuator
    IEEE ASME Transactions on Mechatronics, 2005
    Co-Authors: Sushant M. Dutta, Fathi H. Ghorbel
    Abstract:

    In this paper, we develop a complete mathematical model of a shape memory alloy (SMA) wire actuated by an electric current and a bias spring. The operation of the SMA actuator involves different physical phenomena, such as heat transfer, phase transformation with temperature Hysteresis, Stress-strain variations and electrical resistance variation accompanying the phase transformation. We model each of these phenomena in a modular fashion. A key feature of the proposed model is that one or more of its modules can be extended to fit other SMA applications. At the heart of the proposed model is a differential Hysteresis model capable of representing minor Hysteresis loops. We generate the temperature profile for the Hysteresis model using lumped parameter analysis. We extend the variable sublayer model to represent actuator strain and electrical resistance. This model can be used to develop a position control system for the actuator. Simulation results from the model are found to be in good agreement with experimental data.

  • Dynamic Modeling and Control of Hysteresis in a Shape Memory Alloy Actuator
    Dynamic Systems and Control Parts A and B, 2004
    Co-Authors: Sushant M. Dutta, Fathi H. Ghorbel, James B. Dabney
    Abstract:

    In this paper, we develop a complete mathematical model of a shape memory alloy (SMA) wire actuated by electric power and a bias spring. The operation of the SMA actuator involves different physical phenomena, such as heat transfer, phase transformation with temperature Hysteresis, Stress–strain variations and electrical resistance variation accompanying the phase transformation. We model each of these phenomena in a modular fashion. A key feature of the proposed model is that one or more of its modules can be extended to fit other SMA applications. At the heart of the proposed model is a dynamic Hysteresis model capable of representing minor Hysteresis loops. We generate the temperature profile for the Hysteresis model using lumped parameter analysis. We extend the variable sublayer model to represent actuator strain and electrical resistance. The dynamic properties of the Hysteresis model are developed and are exploited in developing control system strategies. Control simulation case studies are presented.Copyright © 2004 by ASME

Harris Farooq - One of the best experts on this subject based on the ideXlab platform.

  • Crystal plasticity modeling of the cyclic behavior of polycrystalline aggregates under non-symmetric uniaxial loading: Global and local analyses
    International Journal of Plasticity, 2020
    Co-Authors: Harris Farooq, Georges Cailletaud, Samuel Forest, David Ryckelynck
    Abstract:

    Abstract When a sample is cyclically loaded under a mean Stress or strain, incremental strain ratcheting or mean Stress relaxation phenomena are usually observed. Experiments show that for metallic materials there is generally no full mean Stress relaxation as well as saturation of macroscopic strain ratcheting. In contrast, most macroscopic constitutive models produce both quantities in excess, and complex sets of additional internal variables must be introduced to improve the modeling. Little attention has been paid to model such phenomena using polycrystal aggregates especially going up to the regime of cyclic mechanical stability. In this work based on an elementary crystal plasticity model for FCC crystals and large scale finite element simulations, it is shown that the interaction between different grains is sufficient to cater for such complex phenomena. Light is shed on how different regions of the polycrystal accommodate each other and how the classical definition of constant rate strain ratcheting or a zero mean Stress is nearly impossible to apply to a polycrystalline aggregate. In addition, it is shown that even if a macroscopic stable Hysteresis Stress strain loop is observed, ratcheting phenomena can still be observed at the local scale. The distributions of different constitutive quantities within a polycrystal are also analyzed which gives a new insight into what is happening inside a polycrystal in terms of Stress and strain redistribution. In particular, the existence of evolving bimodal distributions of Stress and accumulated plastic strain is evidenced and related to the occurrence of plastic shakedown and incomplete mean Stress relaxation. Two numerical criteria to detect strain ratcheting are finally proposed and discussed.

  • Crystal plasticity modeling of the cyclic behavior of polycrystalline aggregates under non-symmetric uniaxial loading: Global and local analyses
    International Journal of Plasticity, 2019
    Co-Authors: Harris Farooq, Georges Cailletaud, Samuel Forest, David Ryckelynck
    Abstract:

    When a sample is cyclically loaded under a mean Stress or strain, incremental strain ratcheting or mean Stress relaxation phenomena are usually observed. Experiments show that for metallic materials there is generally no full mean Stress relaxation as well as saturation of macroscopic strain ratcheting. In contrast, most macroscopic constitutive models produce both quantities in excess, and complex sets of additional internal variables must be introduced to improve the modeling. Little attention has been paid to model such phenomena using polycrystal aggregates especially going up to the regime of cyclic mechanical stability. In this work based on an elementary crystal plasticity model for FCC crystals and large scale finite element, it is be shown that the interaction between different grains is sufficient to cater for such complex phenomena. Light is shed on how different regions of the polycrystal accommodate each other and how the classical definition of constant rate strain ratcheting or a zero mean Stress is nearly impossible to apply to a polycrystalline aggregate. In addition, it is shown that even if a macroscopic stable Hysteresis Stress strain loop is observed, ratcheting phenomena can still be observed at the local scale. The distributions of different constitutive quantities within a polycrystal are also analyzed which gives a new insight into what is happening inside a polycrystal in terms of Stress and strain redistribution. In particular, the existence of evolving bimodal distributions of Stress and accumulated plastic strain is evidenced and related to the occurrence of plastic shakedown and incomplete mean Stress relaxation. Two numerical criteria to detect strain ratcheting are finally proposed and discussed.

  • Crystal plasticity modeling of the cyclic behavior of polycrystalline aggregates under non-symmetric uniaxial loading: Global and local analyses
    2019
    Co-Authors: Harris Farooq, Georges Cailletaud, Samuel Forest, David Ryckelynck
    Abstract:

    When a geometry is cyclically loaded under a mean Stress or strain, incremental strain ratcheting or mean Stress relaxation are observed. Experiments shows that for metallic materials there is non-zero mean Stress as well as saturation of macroscopic strain ratcheting, and most macroscopic models produce both quantities in excess. Little attention has been paid to model such phenomena using polycrystal aggregates especially going up to the regime of cyclic mechanical stability. In this paper it will be shown that the interaction between different grains is enough to cater for such complex phenomena using crystal plasticity models for FCC crystals. Light will be shed on how different regions accommodate each other and how the classical definition of constant rate strain ratcheting or a zero mean Stress is nearly impossible in a virtual polycrystal. More importantly, it will be shown that even if there is a macroscopic stable Hysteresis Stress strain loop, local stabilization is not guaranteed. The distribution of different constitutive quantities within a polycrystal are also analyzed which give a new insight into what is happening inside a polycrystal. Specifically, within a polycrystal, accumulated plasticity divides into two parts, and it is postulated that this division of plasticity gives the material its capability to retain its cyclic mean Stress or a saturating ratcheting strain. Two numerical tests to detect strain ratcheting will also be presented. To go up to asymptotic values, as well as to get an unbiased solution a strictly rate-independent model will be used.

Samuel Forest - One of the best experts on this subject based on the ideXlab platform.

  • Crystal plasticity modeling of the cyclic behavior of polycrystalline aggregates under non-symmetric uniaxial loading: Global and local analyses
    International Journal of Plasticity, 2020
    Co-Authors: Harris Farooq, Georges Cailletaud, Samuel Forest, David Ryckelynck
    Abstract:

    Abstract When a sample is cyclically loaded under a mean Stress or strain, incremental strain ratcheting or mean Stress relaxation phenomena are usually observed. Experiments show that for metallic materials there is generally no full mean Stress relaxation as well as saturation of macroscopic strain ratcheting. In contrast, most macroscopic constitutive models produce both quantities in excess, and complex sets of additional internal variables must be introduced to improve the modeling. Little attention has been paid to model such phenomena using polycrystal aggregates especially going up to the regime of cyclic mechanical stability. In this work based on an elementary crystal plasticity model for FCC crystals and large scale finite element simulations, it is shown that the interaction between different grains is sufficient to cater for such complex phenomena. Light is shed on how different regions of the polycrystal accommodate each other and how the classical definition of constant rate strain ratcheting or a zero mean Stress is nearly impossible to apply to a polycrystalline aggregate. In addition, it is shown that even if a macroscopic stable Hysteresis Stress strain loop is observed, ratcheting phenomena can still be observed at the local scale. The distributions of different constitutive quantities within a polycrystal are also analyzed which gives a new insight into what is happening inside a polycrystal in terms of Stress and strain redistribution. In particular, the existence of evolving bimodal distributions of Stress and accumulated plastic strain is evidenced and related to the occurrence of plastic shakedown and incomplete mean Stress relaxation. Two numerical criteria to detect strain ratcheting are finally proposed and discussed.

  • Crystal plasticity modeling of the cyclic behavior of polycrystalline aggregates under non-symmetric uniaxial loading: Global and local analyses
    International Journal of Plasticity, 2019
    Co-Authors: Harris Farooq, Georges Cailletaud, Samuel Forest, David Ryckelynck
    Abstract:

    When a sample is cyclically loaded under a mean Stress or strain, incremental strain ratcheting or mean Stress relaxation phenomena are usually observed. Experiments show that for metallic materials there is generally no full mean Stress relaxation as well as saturation of macroscopic strain ratcheting. In contrast, most macroscopic constitutive models produce both quantities in excess, and complex sets of additional internal variables must be introduced to improve the modeling. Little attention has been paid to model such phenomena using polycrystal aggregates especially going up to the regime of cyclic mechanical stability. In this work based on an elementary crystal plasticity model for FCC crystals and large scale finite element, it is be shown that the interaction between different grains is sufficient to cater for such complex phenomena. Light is shed on how different regions of the polycrystal accommodate each other and how the classical definition of constant rate strain ratcheting or a zero mean Stress is nearly impossible to apply to a polycrystalline aggregate. In addition, it is shown that even if a macroscopic stable Hysteresis Stress strain loop is observed, ratcheting phenomena can still be observed at the local scale. The distributions of different constitutive quantities within a polycrystal are also analyzed which gives a new insight into what is happening inside a polycrystal in terms of Stress and strain redistribution. In particular, the existence of evolving bimodal distributions of Stress and accumulated plastic strain is evidenced and related to the occurrence of plastic shakedown and incomplete mean Stress relaxation. Two numerical criteria to detect strain ratcheting are finally proposed and discussed.

  • Crystal plasticity modeling of the cyclic behavior of polycrystalline aggregates under non-symmetric uniaxial loading: Global and local analyses
    2019
    Co-Authors: Harris Farooq, Georges Cailletaud, Samuel Forest, David Ryckelynck
    Abstract:

    When a geometry is cyclically loaded under a mean Stress or strain, incremental strain ratcheting or mean Stress relaxation are observed. Experiments shows that for metallic materials there is non-zero mean Stress as well as saturation of macroscopic strain ratcheting, and most macroscopic models produce both quantities in excess. Little attention has been paid to model such phenomena using polycrystal aggregates especially going up to the regime of cyclic mechanical stability. In this paper it will be shown that the interaction between different grains is enough to cater for such complex phenomena using crystal plasticity models for FCC crystals. Light will be shed on how different regions accommodate each other and how the classical definition of constant rate strain ratcheting or a zero mean Stress is nearly impossible in a virtual polycrystal. More importantly, it will be shown that even if there is a macroscopic stable Hysteresis Stress strain loop, local stabilization is not guaranteed. The distribution of different constitutive quantities within a polycrystal are also analyzed which give a new insight into what is happening inside a polycrystal. Specifically, within a polycrystal, accumulated plasticity divides into two parts, and it is postulated that this division of plasticity gives the material its capability to retain its cyclic mean Stress or a saturating ratcheting strain. Two numerical tests to detect strain ratcheting will also be presented. To go up to asymptotic values, as well as to get an unbiased solution a strictly rate-independent model will be used.