The Experts below are selected from a list of 186 Experts worldwide ranked by ideXlab platform

E. Hosseini - One of the best experts on this subject based on the ideXlab platform.

  • The investigation of primary creep regeneration for 10%Cr martensitic steel: Unified constitutive modelling
    International Journal of Mechanical Sciences, 2021
    Co-Authors: Stuart Holdsworth, Edoardo Mazza, E. Hosseini
    Abstract:

    Abstract An elastic-viscoplastic constitutive material model is developed for the representation of the creep response of a 10%Cr steel under cyclic loading conditions. It has been shown that the model is able to describe primary creep regeneration (PCR), i.e. the incidence of a period of high creep strain rate following a Stress reversal. The developed model is a variant of the well-known Chaboche viscoplastic constitutive model, and employs a bi-term power-law equation to represent the Stress-regime dependence of the viscoplastic strain rate response. Back Stress and Drag Stress are used to describe the kinematic and isotropic hardening/softening behaviour of the material, respectively. The evolutions of back Stress and Drag Stress consider contributions from strain hardening, dynamic softening, static recovery and cyclic hardening/softening. The effectiveness of the developed model for describing the sensitivity of the PCR behaviour to different loading parameters (e.g. reverse-loading magnitude and duration) and to represent the effect of PCR activation on the overall strain accumulation behaviour of the material is discussed. Furthermore, the predictive capability of the model is demonstrated for describing the response of the material during two independent benchmark tests; a Stress-varying creep and a low-cycle fatigue experiments.

  • Effect of prior deformation on the subsequent creep and anelastic recovery behaviour of an advanced martensitic steel: Unified constitutive modelling
    International Journal of Mechanical Sciences, 2020
    Co-Authors: E. Hosseini, A. Kazemi, Karen Abrinia, Hamid Shahsavari, Stuart Holdsworth, Mostafa Baghani
    Abstract:

    Abstract This paper presents an elastic-viscoplastic constitutive model formulation for the representation of different aspects of high-temperature deformation behaviour of an advanced martensitic steel under various loading conditions. The model is a variant of the well-known Chaboche constitutive model and uses a bi-term power-law equation for describing the Stress dependency of the viscoplastic strain rate. Isotropic and kinematic hardening/softening considerations have been incorporated through the employment of Drag-Stress and back-Stress concepts. The evolution equations for Drag-Stress and back-Stress consider contributions from strain hardening, dynamic strain softening, and static recovery. The effectiveness of the model formulation has been examined for the representation of the deformation behaviour of a 10%Cr martensitic steel at 600 °C. It has been demonstrated that the developed model could provide a fairly accurate description for i) constant-load creep, ii) constant-strain Stress-relaxation, iii) anelastic recovery, and iv) negative creep behaviour of the alloy. More importantly, evidence on the capability of the model for taking into consideration the effect of prior-loading on the subsequent viscoplastic response has been presented.

Stuart Holdsworth - One of the best experts on this subject based on the ideXlab platform.

  • The investigation of primary creep regeneration for 10%Cr martensitic steel: Unified constitutive modelling
    International Journal of Mechanical Sciences, 2021
    Co-Authors: Stuart Holdsworth, Edoardo Mazza, E. Hosseini
    Abstract:

    Abstract An elastic-viscoplastic constitutive material model is developed for the representation of the creep response of a 10%Cr steel under cyclic loading conditions. It has been shown that the model is able to describe primary creep regeneration (PCR), i.e. the incidence of a period of high creep strain rate following a Stress reversal. The developed model is a variant of the well-known Chaboche viscoplastic constitutive model, and employs a bi-term power-law equation to represent the Stress-regime dependence of the viscoplastic strain rate response. Back Stress and Drag Stress are used to describe the kinematic and isotropic hardening/softening behaviour of the material, respectively. The evolutions of back Stress and Drag Stress consider contributions from strain hardening, dynamic softening, static recovery and cyclic hardening/softening. The effectiveness of the developed model for describing the sensitivity of the PCR behaviour to different loading parameters (e.g. reverse-loading magnitude and duration) and to represent the effect of PCR activation on the overall strain accumulation behaviour of the material is discussed. Furthermore, the predictive capability of the model is demonstrated for describing the response of the material during two independent benchmark tests; a Stress-varying creep and a low-cycle fatigue experiments.

  • Effect of prior deformation on the subsequent creep and anelastic recovery behaviour of an advanced martensitic steel: Unified constitutive modelling
    International Journal of Mechanical Sciences, 2020
    Co-Authors: E. Hosseini, A. Kazemi, Karen Abrinia, Hamid Shahsavari, Stuart Holdsworth, Mostafa Baghani
    Abstract:

    Abstract This paper presents an elastic-viscoplastic constitutive model formulation for the representation of different aspects of high-temperature deformation behaviour of an advanced martensitic steel under various loading conditions. The model is a variant of the well-known Chaboche constitutive model and uses a bi-term power-law equation for describing the Stress dependency of the viscoplastic strain rate. Isotropic and kinematic hardening/softening considerations have been incorporated through the employment of Drag-Stress and back-Stress concepts. The evolution equations for Drag-Stress and back-Stress consider contributions from strain hardening, dynamic strain softening, and static recovery. The effectiveness of the model formulation has been examined for the representation of the deformation behaviour of a 10%Cr martensitic steel at 600 °C. It has been demonstrated that the developed model could provide a fairly accurate description for i) constant-load creep, ii) constant-strain Stress-relaxation, iii) anelastic recovery, and iv) negative creep behaviour of the alloy. More importantly, evidence on the capability of the model for taking into consideration the effect of prior-loading on the subsequent viscoplastic response has been presented.

Kevin P. Walker - One of the best experts on this subject based on the ideXlab platform.

  • The viscoplastic behavior of Hastelloy-X single crystal
    International Journal of Plasticity, 1993
    Co-Authors: Eric H. Jordan, Shixiang Shi, Kevin P. Walker
    Abstract:

    Abstract A viscoplastic constitutive model for Hastelloy-X single crystal material is developed based on crystallographic slip theory. The constitutive model was constructed for use in a viscoplastic self-consistent model for isotropic Hastelloy-X polycrystalline material, which has been described in a recent publication. It is found that, by using the slip geometry known from the metallurgical literature, the anisotropic response can be accurately predicted. The model was verified by using tension and torsion data taken at 982°C (1800°F). The constitutive model used on each slip system is a simple unified visoplastic power law model in which weak latent interaction effects are taken into account. The Drag Stress evolution equations for the octahedral system are written in a hardening/recovery format in which both hardening and recovery depend on separate latent interaction effects between the octahedral crystallographic slip systems. The strain rate behavior of the single crystal material is well correlated by the constitutive model in uniaxial and torsion tests, but it is necessary to include latent information effects between the octahedral slip systems in order to obtain the best possible representation of biaxial cyclic strain rate behavior. Finally, it was observed that the single crystal exhibited dynamic strain aging at 871°C (1600°F). Similar dynamic strain aging occurs at 649°C (1200°F) in the polycrystalline version of the alloy.

Mostafa Baghani - One of the best experts on this subject based on the ideXlab platform.

  • Effect of prior deformation on the subsequent creep and anelastic recovery behaviour of an advanced martensitic steel: Unified constitutive modelling
    International Journal of Mechanical Sciences, 2020
    Co-Authors: E. Hosseini, A. Kazemi, Karen Abrinia, Hamid Shahsavari, Stuart Holdsworth, Mostafa Baghani
    Abstract:

    Abstract This paper presents an elastic-viscoplastic constitutive model formulation for the representation of different aspects of high-temperature deformation behaviour of an advanced martensitic steel under various loading conditions. The model is a variant of the well-known Chaboche constitutive model and uses a bi-term power-law equation for describing the Stress dependency of the viscoplastic strain rate. Isotropic and kinematic hardening/softening considerations have been incorporated through the employment of Drag-Stress and back-Stress concepts. The evolution equations for Drag-Stress and back-Stress consider contributions from strain hardening, dynamic strain softening, and static recovery. The effectiveness of the model formulation has been examined for the representation of the deformation behaviour of a 10%Cr martensitic steel at 600 °C. It has been demonstrated that the developed model could provide a fairly accurate description for i) constant-load creep, ii) constant-strain Stress-relaxation, iii) anelastic recovery, and iv) negative creep behaviour of the alloy. More importantly, evidence on the capability of the model for taking into consideration the effect of prior-loading on the subsequent viscoplastic response has been presented.

Koen Dewettinck - One of the best experts on this subject based on the ideXlab platform.

  • rheological profiling of organogels prepared at critical gelling concentrations of natural waxes in a triacylglycerol solvent
    Journal of Agricultural and Food Chemistry, 2015
    Co-Authors: Ashok R Patel, Mehrnoosh Babaahmadi, Ans Lesaffer, Koen Dewettinck
    Abstract:

    The aim of this study was to use a detailed rheological characterization to gain new insights into the gelation behavior of natural waxes. To make a comprehensive case, six natural waxes (differing in the relative proportion of chemical components: hydrocarbons, fatty alcohols, fatty acids, and wax esters) were selected as organogelators to gel high-oleic sunflower oil. Flow and dynamic rheological properties of organogels prepared at critical gelling concentrations (Cg) of waxes were studied and compared using Drag (Stress ramp and steady flow) and oscillatory shear (Stress and frequency sweeps) tests. Although, none of the organogels satisfied the rheological definition of a “strong gel” (G″/G′ (ω) ≤ 0.1), on comparing the samples, the strongest gel (highest critical Stress and dynamic, apparent, and static yield Stresses) was obtained not with wax containing the highest proportion of wax esters alone (sunflower wax, SFW) but with wax containing wax esters along with a higher proportion of fatty alcohol...

  • Rheological Profiling of Organogels Prepared at Critical Gelling Concentrations of Natural Waxes in a Triacylglycerol Solvent
    2015
    Co-Authors: Ashok R Patel, Mehrnoosh Babaahmadi, Ans Lesaffer, Koen Dewettinck
    Abstract:

    The aim of this study was to use a detailed rheological characterization to gain new insights into the gelation behavior of natural waxes. To make a comprehensive case, six natural waxes (differing in the relative proportion of chemical components: hydrocarbons, fatty alcohols, fatty acids, and wax esters) were selected as organogelators to gel high-oleic sunflower oil. Flow and dynamic rheological properties of organogels prepared at critical gelling concentrations (Cg) of waxes were studied and compared using Drag (Stress ramp and steady flow) and oscillatory shear (Stress and frequency sweeps) tests. Although, none of the organogels satisfied the rheological definition of a “strong gel” (G″/G′ (ω) ≤ 0.1), on comparing the samples, the strongest gel (highest critical Stress and dynamic, apparent, and static yield Stresses) was obtained not with wax containing the highest proportion of wax esters alone (sunflower wax, SFW) but with wax containing wax esters along with a higher proportion of fatty alcohols (carnauba wax, CRW) although at a comparatively higher Cg (4%wt for latter compared to 0.5%wt for former). As expected, gel formation by waxes containing a high proportion of lower melting fatty acids (berry, BW, and fruit wax, FW) required a comparatively higher Cg (6 and 7%wt, respectively), and in addition, these gels showed the lowest values for plateau elastic modulus (G′LVR) and a prominent crossover point at higher frequency. The gelation temperatures (TG′=G″) for all the studied gels were lower than room temperature, except for SFW and CRW. The yielding-type behavior of gels was evident, with most gels showing strong shear sensitivity and a weak thixotropic recovery. The rheological behavior was combined with the results of thermal analysis and microstructure studies (optical, polarized, and cryo-scanning electron microscopy) to explain the gelation properties of these waxes