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L. Briottet - One of the best experts on this subject based on the ideXlab platform.
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Damage in a Viscoplastic Material—Part II. Overall behaviour
International Journal of Plasticity, 1999Co-Authors: L. BriottetAbstract:Abstract The overall behaviour of a damaged Viscoplastic Material under axisymmetric loading is addressed in this paper. A linear viscous matrix containing aligned spheroidal cavities is first considered. Its overall behaviour is estimated by means of a differential scheme. The damage-induced morphological anisotropy, due to the shape of the voids, is then analyzed. It is shown to be significant even at low volume fractions of cavities ( ƒ ), when the latter are prolate or oblate. These results are then used to predict the behaviour of a nonlinear viscous matrix containing aligned spheroidal cavities, by means of a variational principle proposed by Ponte Castaneda (1991). Two types of nonlinear matrix behaviour are considered: a power law corresponding to metal forming at moderate strain rates and a linear law with nonzero intercept suited to high strain rates.The constitutive equations of such nonlinear damaged Materials have been used in a companion paper in order to study the influence of matrix compressibility on the growth of a spheroidal cavity during straining.
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damage in a Viscoplastic Material part ii overall behaviour
International Journal of Plasticity, 1998Co-Authors: L. BriottetAbstract:Abstract The overall behaviour of a damaged Viscoplastic Material under axisymmetric loading is addressed in this paper. A linear viscous matrix containing aligned spheroidal cavities is first considered. Its overall behaviour is estimated by means of a differential scheme. The damage-induced morphological anisotropy, due to the shape of the voids, is then analyzed. It is shown to be significant even at low volume fractions of cavities ( ƒ ), when the latter are prolate or oblate. These results are then used to predict the behaviour of a nonlinear viscous matrix containing aligned spheroidal cavities, by means of a variational principle proposed by Ponte Castaneda (1991). Two types of nonlinear matrix behaviour are considered: a power law corresponding to metal forming at moderate strain rates and a linear law with nonzero intercept suited to high strain rates.The constitutive equations of such nonlinear damaged Materials have been used in a companion paper in order to study the influence of matrix compressibility on the growth of a spheroidal cavity during straining.
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damage in a Viscoplastic Material part i cavity growth
International Journal of Plasticity, 1996Co-Authors: L. Briottet, Helmut Klocker, F MontheilletAbstract:Abstract The exact velocity, stress and strain rate fields around a spheroidal cavity in an infinite linear Viscoplastic compressible matrix are derived analytically by the ‘three function approach’. The perturbation of the velocity field due to the cavity is the superposition of three independent modes, inducing homothetic growth, pure distortion and both volume and shape changes, respectively. This solution is then used to investigate the velocity field around a spheroidal cavity in a nonlinear viscous compressible Material by means of a variational principle. The behaviour of such damaged linear and nonlinear Materials will be discussed in a forthcoming companion paper. The importance of the reference strain, while studying void growth in a compressible Material, is emphasized. If the axial strain is chosen as a reference, void growth is found to be enhanced at low triaxiality ratios, but lowered at high triaxiality ratios in a compressible matrix relative to an incompressible one. Finally, the transition from a power law to a linear law with intercept, at increasing strain rates, is shown to reduce damage growth rate.
Janis Varna - One of the best experts on this subject based on the ideXlab platform.
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nonlinear viscoelastic Viscoplastic Material model including stiffness degradation for hemp lignin composites
Composites Science and Technology, 2008Co-Authors: Erik Marklund, Johannes Eitzenberger, Janis VarnaAbstract:Abstract In repeating tensile tests with increasing maximum strain for every loading cycle the hemp/lignin composites clearly showed a nonlinear behavior and hysteresis loops in loading and unloading. The explanation for this behavior is the inherent viscoelastic nature for this type of Material, but also noticeable stiffness degradation with increasing strain level. Creep tests performed at different stress levels revealed a nonlinear viscoelastic response and after recovery Viscoplastic strain was detected for high stress levels. It is demonstrated that Schapery’s model is suitable to model nonlinear viscoelasticity whereas Viscoplastic strain may be described by a nonlinear functional presented by Zapas and Crissman. In a creep test this functional leads to a power law with respect to time and stress. In order to include stiffness reduction due to damage Schapery’s model has been modified by incorporating a maximum strain-state dependent function reflecting the elastic modulus reduction with increasing strain measured in tensile tests. A generalized incremental model of the constitutive equation for viscoelastic case has been used to validate the developed Material model in a linear stress controlled loading and unloading ramp. The model successfully describes the main features for the investigated Material and shows good agreement with test data within the considered stress range.
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Nonlinear viscoelastic Viscoplastic Material model including stiffness degradation for hemp/lignin composites
Composites Science and Technology, 2008Co-Authors: Erik Marklund, Johannes Eitzenberger, Janis VarnaAbstract:Abstract In repeating tensile tests with increasing maximum strain for every loading cycle the hemp/lignin composites clearly showed a nonlinear behavior and hysteresis loops in loading and unloading. The explanation for this behavior is the inherent viscoelastic nature for this type of Material, but also noticeable stiffness degradation with increasing strain level. Creep tests performed at different stress levels revealed a nonlinear viscoelastic response and after recovery Viscoplastic strain was detected for high stress levels. It is demonstrated that Schapery’s model is suitable to model nonlinear viscoelasticity whereas Viscoplastic strain may be described by a nonlinear functional presented by Zapas and Crissman. In a creep test this functional leads to a power law with respect to time and stress. In order to include stiffness reduction due to damage Schapery’s model has been modified by incorporating a maximum strain-state dependent function reflecting the elastic modulus reduction with increasing strain measured in tensile tests. A generalized incremental model of the constitutive equation for viscoelastic case has been used to validate the developed Material model in a linear stress controlled loading and unloading ramp. The model successfully describes the main features for the investigated Material and shows good agreement with test data within the considered stress range.
N.c. Barnard - One of the best experts on this subject based on the ideXlab platform.
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A viscoelastic – Viscoplastic Material model for superalloy applications
International Journal of Fatigue, 2020Co-Authors: J.p. Rouse, B. Engel, Christopher J. Hyde, Stephen Pattison, Mark Whittaker, Jonathan Jones, B.j. Cockings, N.c. BarnardAbstract:Abstract An understanding of rate dependency over a wide range of time scales is vitally important in approximating the transient response of critical components operating in extreme environments. Many examples of Viscoplastic model formulations can be found in the literature, wherein all rate dependency is assumed to occur after yielding. Such models neglect any viscous effects during elastic deformation. In the present work, a unified viscoelastic – Viscoplastic Material model is developed for the Nickel superalloy RR1000. Particular emphasis is placed on model parameter determination, which is accomplished using standard cyclic plasticity and stress relaxation experimental data.
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a viscoelastic Viscoplastic Material model for superalloy applications
International Journal of Fatigue, 2020Co-Authors: J.p. Rouse, B. Engel, Christopher J. Hyde, Stephen Pattison, Jonathan Jones, B.j. Cockings, M T Whittaker, N.c. BarnardAbstract:Abstract An understanding of rate dependency over a wide range of time scales is vitally important in approximating the transient response of critical components operating in extreme environments. Many examples of Viscoplastic model formulations can be found in the literature, wherein all rate dependency is assumed to occur after yielding. Such models neglect any viscous effects during elastic deformation. In the present work, a unified viscoelastic – Viscoplastic Material model is developed for the Nickel superalloy RR1000. Particular emphasis is placed on model parameter determination, which is accomplished using standard cyclic plasticity and stress relaxation experimental data.
Christoph Schweizer - One of the best experts on this subject based on the ideXlab platform.
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Computational Assessment of the Microstructure-Dependent Thermomechanical Behaviour of AlSi12CuNiMg-T7—Methods and Microstructure-Based Finite Element Analyses
Advances in Mechanics of High-Temperature Materials, 2020Co-Authors: Carl Fischer, Axel Reichenbacher, Mario Metzger, Christoph SchweizerAbstract:In this paper, the influence of the microstructure of a cast aluminium alloy used for pistons in combustion engines on the local and global deformation behavior is investigated by means of microstructure-based cell models and the finite element method. Therefore, a representative microstructure is digitized using nano computer tomography. In the digitized and segmented data, the aluminium matrix, silicon particles, pores and two intermetallic phases are distinguished. Microstructure-based cell models are created and linear-elastic, thermal and Viscoplastic Material properties are assigned for the finite element simulation in ABAQUS/Standard. The elastic, macroscopic nearly isotropic Material behavior is shown for 64 different microstructure-based cell models with 200 $$\times $$ 200 $$\times $$ 200 elements with microstructure-dependent Material properties at room temperature. A microstructure cell is subjected to a thermal cycle with zero macroscopic loading in order to examine the influence of the thermal mismatch between the individual microstructure phases on the resulting stresses and strains on the micro level. High stresses at interfaces of silicon particles and the aluminium matrix occur in the linear-elastic simulation, whereas an elastic-Viscoplastic Material behavior of the aluminium matrix leads to a overall stress relief in the microstructure cell.
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Evolution equations for the C(t)-integral and the crack-tip opening displacement CTOD for elastic–Viscoplastic Material behavior and temperature dependent Material properties
Engineering Fracture Mechanics, 2016Co-Authors: Christoph SchweizerAbstract:Abstract In this paper evolution equations for the C ( t ) -integral and the crack-tip opening displacement CTOD are presented for elastic–Viscoplastic Material behavior and monotonic loading. The evolution equations account for the temperature dependence of the elastic, plastic and viscous Material properties. Additionally, an implicit integration algorithm is presented and validated by using finite element simulations.
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evolution equations for the c t integral and the crack tip opening displacement ctod for elastic Viscoplastic Material behavior and temperature dependent Material properties
Engineering Fracture Mechanics, 2016Co-Authors: Christoph SchweizerAbstract:Abstract In this paper evolution equations for the C ( t ) -integral and the crack-tip opening displacement CTOD are presented for elastic–Viscoplastic Material behavior and monotonic loading. The evolution equations account for the temperature dependence of the elastic, plastic and viscous Material properties. Additionally, an implicit integration algorithm is presented and validated by using finite element simulations.
Erik Marklund - One of the best experts on this subject based on the ideXlab platform.
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nonlinear viscoelastic Viscoplastic Material model including stiffness degradation for hemp lignin composites
Composites Science and Technology, 2008Co-Authors: Erik Marklund, Johannes Eitzenberger, Janis VarnaAbstract:Abstract In repeating tensile tests with increasing maximum strain for every loading cycle the hemp/lignin composites clearly showed a nonlinear behavior and hysteresis loops in loading and unloading. The explanation for this behavior is the inherent viscoelastic nature for this type of Material, but also noticeable stiffness degradation with increasing strain level. Creep tests performed at different stress levels revealed a nonlinear viscoelastic response and after recovery Viscoplastic strain was detected for high stress levels. It is demonstrated that Schapery’s model is suitable to model nonlinear viscoelasticity whereas Viscoplastic strain may be described by a nonlinear functional presented by Zapas and Crissman. In a creep test this functional leads to a power law with respect to time and stress. In order to include stiffness reduction due to damage Schapery’s model has been modified by incorporating a maximum strain-state dependent function reflecting the elastic modulus reduction with increasing strain measured in tensile tests. A generalized incremental model of the constitutive equation for viscoelastic case has been used to validate the developed Material model in a linear stress controlled loading and unloading ramp. The model successfully describes the main features for the investigated Material and shows good agreement with test data within the considered stress range.
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Nonlinear viscoelastic Viscoplastic Material model including stiffness degradation for hemp/lignin composites
Composites Science and Technology, 2008Co-Authors: Erik Marklund, Johannes Eitzenberger, Janis VarnaAbstract:Abstract In repeating tensile tests with increasing maximum strain for every loading cycle the hemp/lignin composites clearly showed a nonlinear behavior and hysteresis loops in loading and unloading. The explanation for this behavior is the inherent viscoelastic nature for this type of Material, but also noticeable stiffness degradation with increasing strain level. Creep tests performed at different stress levels revealed a nonlinear viscoelastic response and after recovery Viscoplastic strain was detected for high stress levels. It is demonstrated that Schapery’s model is suitable to model nonlinear viscoelasticity whereas Viscoplastic strain may be described by a nonlinear functional presented by Zapas and Crissman. In a creep test this functional leads to a power law with respect to time and stress. In order to include stiffness reduction due to damage Schapery’s model has been modified by incorporating a maximum strain-state dependent function reflecting the elastic modulus reduction with increasing strain measured in tensile tests. A generalized incremental model of the constitutive equation for viscoelastic case has been used to validate the developed Material model in a linear stress controlled loading and unloading ramp. The model successfully describes the main features for the investigated Material and shows good agreement with test data within the considered stress range.
