Modeling of Grain Shape Effect on Multiaxial Plasticity of Metallic Polycrystals

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
A. Abdul-Latif
Keyword(s):  
Grain Shape ◽  
Inelastic Strain ◽  
Cyclic Behavior ◽  
Loading Path ◽  
Model Parameters ◽  
Shape Effect ◽  
Inelastic Behavior ◽  
Aspect Ratios ◽  
Ellipsoidal Shape ◽  
Aluminum Alloy 2024

A simplified nonincremental interaction law is used describing the nonlinear elastic-inelastic behavior of FCC polycrystals proposed recently (Abdul-Latif and Radi, 2010, “Modeling of the Grain Shape Effect on the Elastic-Inelastic Behavior of Polycrystals with Self-Consistent Scheme,” ASME J. Eng. Mater. Technol., 132(1), p. 011008). In this scheme, the elastic strain defined at the granular level based on the Eshelby's tensor is assumed to be isotropic, uniform and compressible. Hence, the approach considers that the inclusion (grain) has an ellipsoidal shape of half axes defining by a, b and c such as a ≠ b = c. The granular heterogeneous inelastic strain is locally determined using the slip theory. Both elastic and inelastic granular strains depend on the granular aspect ratio (α = a/b). An aggregate of grains of ellipsoidal shape is supposed to be randomly distributed with a distribution of aspect ratios having a log-normal statistical function. The effect of this distribution on the mechanical behavior is investigated. A host of cyclic inelastic behavior of polycrystalline metals is predicted under uniaxial and multiaxial loading paths. Using the aluminum alloy 2024, an original complex cyclic loading path type is proposed and carried out experimentally. After the model parameters calibration, the elastic-inelastic cyclic behavior of this alloy is quantitatively described by the model. As a conclusion, the model can successfully describe the elasto-inelastic at the overall and local levels.

Grain Shape Effect and the Viscoplastic Parameter on the Evolution of Isotropic and Kinematic Hardening of Metallic Materials under Cyclic Loading

2019 ◽  
Vol 820 ◽  
pp. 48-59
Author(s):  
Abdelhamid Kerkour-El Miad ◽  
A. Kerour-El Miad ◽  
Redouane Kouddane
Keyword(s):  
Grain Shape ◽  
Kinematic Hardening ◽  
Inelastic Strain ◽  
System Level ◽  
Elastic Behavior ◽  
Isotropic Hardening ◽  
Shape Effect ◽  
Metallic Materials ◽  
Crystallographic Slip ◽  
Self Consistent

The main objective of this work is to study the grain shape effect (aspect ratio α = a / b) and the viscoplastic parameter γ on the evolution of the kinematic and isotropic hardening of FCC type metallic materials, under uniaxial cyclic Tension-Compression ‘‘TC’ and to interpret these results. These parameters of shape and viscoplastic were developed and introduced by Abdul-Latif and Radi, indeed in this study we use their model. Expressed within the framework of a self-consistent approach, the rate-dependent inelastic strain is examined at the crystallographic slip system level describing a constitutive model for FCC metallic polycrystals, whereas the elastic strain is determined at the granular level. Based on the Eshelby’s tensor, the elastic behavior is assumed to be compressible. For a polycrystalline structure, the grains deform plastically by crystallographic slip located at the most favorably oriented systems supporting a high resolved shear stress . The approach considers that the inclusion (grain) form is ellipsoidal of half axes defining by a, b and c such as a ≠b= c. Several numerical tests are carried out highlighting the role of shape and viscoplastic parameter on the evolution of kinematic and isotropic hardening. A general comparison between the and effect on the overall hardening of the polycrystal shows that this work hardening is more sensitive to the parameter (for given ) compared to (for given). Keywords: Grain shape effect, Ellipsoidal inclusion, Viscoplastic parameter effect, Kinematic and isotropic hardening, Uniaxial cyclic ‘‘TC‘‘, Self-consistent model.

Modeling of the Grain Shape Effect on the Elastic-Inelastic Behavior of Polycrystals With Self-Consistent Scheme

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
A. Abdul-Latif ◽  
M. Radi
Keyword(s):  
Grain Shape ◽  
Spherical Inclusion ◽  
Shape Effect ◽  
Inelastic Behavior ◽  
Consistent Model ◽  
Self Consistent ◽  
Eshelby’S Tensor ◽  
Anisotropic Elastic ◽  
Nonlinear Elastic ◽  
Interaction Law

Based on a well established nonincremental interaction law for fully anisotropic elastic-inelastic behavior of polycrystals, tangent formulation-based and simplified interaction laws of softened nature are derived to describe the nonlinear elastic-inelastic behavior of fcc polycrystals. Using the Eshelby’s tensor, the developed approach considers that the inclusion (grain) form is ellipsoidal. It has been clearly demonstrated by Abdul-Latif et al. (2002, “Elastic-Inelastic Self-Consistent Model for Polycrystals,” ASME J. Appl. Mech., 69, pp. 309–316) for spherical inclusion that the tangent formulation-based model requires more calculation time, and is incapable to describe correctly the multiaxial elastic-inelastic behavior of polycrystals in comparison with the simplified model. Hence, the simplified nonincremental interaction is studied considering the grain shape effect. A parametric study is conducted showing principally the influence of the some important parameters (the grain shape (α) and the new viscous parameter γ) and the effect of their interaction on the hardening evolution of polycrystals. Quantitatively, it is recognized that the model describes suitably the grain shape effect together with the new viscous parameter γ on the strain-stress behavior of aluminum and Waspaloy under tensile test.

Micromagnetic simulations on the grain shape effect in Nd-Fe-B magnets

2016 ◽  
Vol 120 (3) ◽  
pp. 033903 ◽  
Author(s):  
Min Yi ◽  
Oliver Gutfleisch ◽  
Bai-Xiang Xu
Keyword(s):  
Grain Shape ◽  
Shape Effect ◽  
Micromagnetic Simulations

Sophisticated Creep-Fatigue Life Estimation Scheme for Pressure Vessel Components Based on Stress Redistribution Locus Concept

2004 ◽  
Author(s):  
Takashi Shimakawa ◽  
Kyotada Nakamura ◽  
Ken-Ichi Kobayashi
Keyword(s):  
Thermal Stress ◽  
Pressure Vessel ◽  
Inelastic Strain ◽  
Stress Redistribution ◽  
Inelastic Behavior ◽  
Strain Concentration ◽  
Strain Behavior ◽  
Creep Fatigue ◽  
Current Design ◽  
Estimation Scheme

High temperature components are operated under cyclic thermal transient. Creep-Fatigue is the most dominant failure mode to be considered in Elevated Temperature Design of these components. Design limit for computed thermal stress is allowed to exceed yielding, because thermal stress is generally regarded as a displacement controlled one. Since creep deformation is considered as additional inelastic behavior, methodology to estimate inelastic strain concentration should be prepared in a design standard. Though inelastic FEM analyses can be applied to calculate inelastic strain concentration magnitude, it is well known that prediction is affected by applied constitutive model. Current design codes recommend to apply elastic FEM and to estimate inelastic strain behavior by simplified method. This paper presents sophisticated technique to estimate inelastic strain behavior based on Stress Redistribution Locus (SRL) method. Applicability of SRL concept is discussed with a help of FEM results for representative components of pressure vessel components such as nozzle, skirt and tube sheet.

Yield Surface and Complex Loading Path Simulation of a Duplex Stainless Steel Using a Bi-Phase Polycrystalline Model

2007 ◽  
Vol 567-568 ◽  
pp. 141-144 ◽  
Author(s):  
Pierre Evrard ◽  
Veronique Aubin ◽  
Suzanne Degallaix ◽  
Djimedo Kondo
Keyword(s):  
Stainless Steel ◽  
Uniaxial Tension ◽  
Compression Test ◽  
Plastic Anisotropy ◽  
Constant Strain Rate ◽  
Loading Path ◽  
Model Parameters ◽  
Proportional Loading ◽  
Loading Paths ◽  
Polycrystalline Model

In order to model the elasto-viscoplastic behaviour of an austenitic-ferritic stainless steel, the model initially developed by Cailletaud-Pilvin [1] [2] and used for modeling single-phase polycrystalline steel is extended in order to take into account the bi-phased character of a duplex steel. Two concentration laws and two local constitutive laws, based on the crystallographic slips and the dislocation densities, are thus simultaneously considered. The model parameters are identified by an inverse method. Simple tests among which tension test at constant strain rate and at different strain rates and uniaxial tension-compression test are used during the identification step. The predictive capabilities of the polycrystalline model are tested for non-proportional loading paths. It is shown that the model reproduces the over-hardening experimentally observed for this kind of loading paths. Then, yield surfaces are simulated during a uniaxial tension-compression test: it is shown that the distortion (i.e. plastic anisotropy induced by loading path) is correctly described.

Prediction of Low Cycle Fatigue Life Using Cycles Jumping Integration Scheme

2015 ◽  
Vol 784 ◽  
pp. 308-316 ◽  
Author(s):  
Carl Labergere ◽  
Khemais Saanouni ◽  
Zhi Dan Sun ◽  
Mohamed Ali Dhifallah ◽  
Yisa Li ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Low Cycle Fatigue ◽  
Mesh Size ◽  
Loading Path ◽  
Integration Scheme ◽  
Model Parameters ◽  
Cycle Fatigue ◽  
316L Steel ◽  
Fully Coupled ◽  
Full Loading

In this paper, cycles jumping scheme integration is used to numerically integrate fully coupled constitutive equations in order to predict the low cycle fatigue life under cyclic loading. This procedure avoids the calculation of the full loading cycles (some millions of loading cycles) while considering the transient stages due to the hardening (at the beginning) and the high damage-induced softening during the last tens of loading cycles. The model parameters have been identified using the results obtained from a 316L steel cylindrical specimen subject to symmetric tension-compression loading path. The effects of the specimen size as well as the mesh size on the fatigue life prediction are investigated.

Sensitivity of three-component 3D finite-difference elastic seismic modeling to inclusion parameters in HTI and TTI media with high inclusion density

Geophysics ◽  
2010 ◽  
Vol 75 (2) ◽  
pp. T49-T61 ◽  
Author(s):  
Yanrong Hu ◽  
George McMechan
Keyword(s):  
Finite Difference ◽  
Aspect Ratio ◽  
Crack Density ◽  
Carbonate Reservoir ◽  
Staggered Grid ◽  
Model Parameters ◽  
Seismic Responses ◽  
Eighth Order ◽  
Direction Parallel ◽  
Aspect Ratios

Parameters associated with the presence of inclusions (cracks or vugs) significantly influence seismic responses. The T-matrix method is used to define approximate anisotropic effective elastic stiffness tensors for media with inclusions. This allows 3D, three-component, eighth-order staggered-grid finite-difference modeling to simulate the seismic responses of anisotropic media with high inclusion density, various aspect ratios, spatial distributions and orientations of inclusions, and fluid content. The model parameters are chosen to represent aligned inclusions ranging from vertical cracks to vugs in a carbonate reservoir encased in clastics. The magnitude of anisotropy increases with increasing inclusion density for P- and S-waves. Cracks in a high-velocity carbonate reduce the stiffnesses and correspondingvelocities; this results in smaller contrasts with the surrounding (lower-stiffness) clastics and, hence, smaller reflection coefficients. S-wave splitting and the anisotropy of [Formula: see text] are clearly visible.The aspect ratio of the spatial distribution of the cracks potentially produces larger anisotropy than the crack aspect ratio, especially at large crack density. The crack distribution has little effect on stiffnesses parallel to the cracks but a large effect perpendicular to the cracks. As the crack orientation moves farther from vertical, changes in the resulting seismograms are more systematic in the direction parallel to the crack strike than perpendicular to it. The seismic signatures resulting from variations of the inclusion parameters are significant and easily visible in the data. This is a computational basis for obtaining more accurate, complete, and quantitative characterizations of inclusions.

Thermal Conductivity Enhancement of Ethylene Glycol-Based Suspensions in the Presence of Silver Nanoparticles of Various Shapes

2013 ◽  
Vol 136 (3) ◽  
Author(s):  
Xin Fang ◽  
Qing Ding ◽  
Li-Wu Fan ◽  
Zi-Tao Yu ◽  
Xu Xu ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Ethylene Glycol ◽  
The Other ◽  
Thermal Conductivity Enhancement ◽  
Shape Effect ◽  
Conductivity Enhancement ◽  
Shape Dependence ◽  
Aspect Ratios ◽  
Relative Enhancement ◽  
Particle Shape Effect

In this technical brief, the effect of adding silver (Ag) nanoparticles of various shapes on the thermal conductivity enhancement of ethylene glycol (EG)-based suspensions was investigated experimentally. These included Ag nanospheres (Ag NSs), Ag nanowires (Ag NWs), and Ag nanoflakes (Ag NFs). Measurements of the thermal conductivity of the suspensions were performed from 10 to 30 °C at an increment of 5 °C. It was shown that the thermal conductivity of the EG-based suspensions increases with raising the temperature. The Ag NWs of a high aspect ratio (∼500) caused greatest relative enhancement up to 15.6% at the highest loading of nearly 0.1 vol. %, whereas the other two shapes of nanoparticles, Ag NSs and Ag NFs with much smaller aspect ratios, only led to enhancements up to 5%. The formation of a network of Ag NWs that facilitates heat conduction was likely responsible for their better performance. The relative enhancement was also predicted by the Hamilton-Crosser model that takes the particle shape effect into consideration. It was shown that the predictions far underestimate the thermal conductivity enhancements but are qualitatively consistent with their shape dependence. As a penalty, however, the presence of Ag NWs was shown to give rise to significant increase in the viscosity of the EG-based suspensions.

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