scholarly journals On Adequacy of Two-point Averaging Schemes for Composites with Nonlinear Viscoelastic Phases

10.14311/658 ◽  
2004 ◽  
Vol 44 (5-6) ◽  
Author(s):  
J. Zeman ◽  
R. Valenta ◽  
M. Šejnoha
Keyword(s):  
Finite Element ◽  
Shear Bands ◽  
Material Model ◽  
Finite Element Simulations ◽  
Composite Medium ◽  
Viscoelastic Response ◽  
Two Phase ◽  
Nonlinear Viscoelastic ◽  
The Matrix ◽  
Macroscopic Response

Finite element simulations on fibrous composites with nonlinear viscoelastic response of the matrix phase are performed to explain why so called two-point averaging schemes may fail to deliver a realistic macroscopic response. Nevertheless, the potential of two-point averaging schemes (the overall response estimated in terms of localized averages of a two-phase composite medium) has been put forward in number of studies either in its original format or modified to overcome the inherited stiffness of classical ”elastic” localization rules. However, when the material model and geometry of the microstructure promote the formation of shear bands, none of the existing two-point averaging schemes will provide an adequate macroscopic response, since they all fail to capture the above phenomenon. Several examples are presented here to support this statement. 

VELOCITY AND ATTENUATION OF SEISMIC WAVES IN TWO‐PHASE MEDIA: PART I. THEORETICAL FORMULATIONS

Geophysics ◽  
1974 ◽  
Vol 39 (5) ◽  
pp. 587-606 ◽  
Author(s):  
Guy T. Kuster ◽  
M. Nafi Toksöz
Keyword(s):  
Elastic Moduli ◽  
Seismic Waves ◽  
Matrix Material ◽  
Composite Medium ◽  
Solid Matrix ◽  
Seismic Velocities ◽  
Displacement Fields ◽  
Two Phase ◽  
The Matrix ◽  
In Series

The propagation of seismic waves in two‐phase media is treated theoretically to determine the elastic moduli of the composite medium given the properties, concentrations, and shapes of the inclusions and the matrix material. For long wavelengths the problem is formulated in terms of scattering phenomena in an approach similar to that of Ament (1959). The displacement fields, expanded in series, for waves scattered by an “effective” composite medium and individual inclusions are equated. The coefficients of the series expansions of the displacement fields provide a relationship between the elastic moduli of the effective medium and those of the matrix and inclusions. The expressions are derived for both solid and liquid inclusions in a solid matrix as well as for solid suspensions in a fluid matrix. Both spherical and oblate spheroidal inclusions are considered. Some numerical calculations are carried out to demonstrate the effects of fluid inclusions of various shapes on the seismic velocities in rocks. It is found that the concentration, shapes, and properties of the inclusions are important parameters. A concentration of a fraction of one percent of thin (small aspect ratio) inclusions could affect the compressional and shear velocities by more than ten percent. For both sedimentary and igneous rock models, the calculations for “dry” (i.e.,air‐saturated) and water‐saturated states indicate that the compressional velocities change significantly while the shear velocities change much less upon saturation with water.

Influence of Material Model on Tensile Loaded Joint

2010 ◽  
Vol 165 ◽  
pp. 394-399 ◽  
Author(s):  
E. Szymczyk ◽  
Grzegorz Slawinski
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Numerical Analysis ◽  
Stress Field ◽  
Material Model ◽  
Finite Element Simulations ◽  
Residual Stress Field ◽  
Material Models ◽  
Riveted Joint ◽  
Load Conditions

The paper deals with the numerical analysis of a tensile loaded riveted joint. Finite element simulations of the upsetting process were carried out with the use of Marc code to determine the residual stress field. The contact with friction is defined between the mating parts of the joint. The computations were performed for four cases of material and load conditions and a comparison was performed on the basis of results obtained for standard elasto plastic and Gurson material models. Moreover, the influence of material model and residual stress on the tensile loaded joint was analyzed.

Stress Behavior at the Interface Junction of an Elastic Inclusion

2002 ◽  
Vol 69 (6) ◽  
pp. 844-852 ◽  
Author(s):  
Z. Q. Qian ◽  
A. R. Akisanya ◽  
D. S. Thompson
Keyword(s):  
Finite Element ◽  
Elastic Inclusion ◽  
Symmetric Mode ◽  
The Finite Element Method ◽  
Displacement Fields ◽  
Two Phase ◽  
Stress And Displacement Fields ◽  
Higher Order Terms ◽  
The Matrix ◽  
Finite Element Prediction

The stress distribution at the interface junction of an elastic inclusion embedded in a brittle matrix is examined. Solutions are derived for the stress and displacement fields near the junction formed by the intersection of the interfaces between the inclusion and the matrix. The stress field consists of symmetric (mode I) and skew-symmetric (mode II) components. The magnitude of the intensity factor associated with each mode of deformation is determined using a combination of the finite element method and a contour integral. The numerical results of the stresses near the interface junction of two different inclusion geometries show that the asymptotic solutions of the stresses are in agreement with those from the finite element prediction when higher-order terms are considered. The implications of the results for the failure of particle-reinforced and two-phase brittle materials are discussed.

Dynamic Constitutive and Failure Behavior of a Two-Phase Tungsten Composite

1997 ◽  
Vol 64 (3) ◽  
pp. 487-494 ◽  
Author(s):  
M. Zhou ◽  
R. J. Clifton
Keyword(s):  
Shear Band ◽  
Shear Bands ◽  
Kolsky Bar ◽  
High Rate ◽  
Failure Behavior ◽  
Localized Deformation ◽  
Two Phase ◽  
The Matrix ◽  
Torsional Kolsky Bar ◽  
The Impact

The constitutive response and failure behavior of a W-Ni-Fe alloy over the strain rate range of 10-4 to 5 X 105 s-1 is experimentally investigated. Experiments conducted are pressure-shear plate impact, torsional Kolsky bar, and quasi-static torsion. The material has a microstructure of hard tungsten grains embedded in a soft alloy matrix. Nominal shear stress-strain relations are obtained for deformations throughout the experiments and until after the initiation of localization. Shear bands form when the plastic strain becomes sufficiently large, involving both the grains and the matrix. The critical shear strain for shear band development under the high rate, high pressure conditions of pressure-shear is approximately 1–1.5 or 6–8 times that obtained in torsional Kolsky bar experiments which involve lower strain rates and zero pressure. Shear bands observed in the impact experiments show significantly more intensely localized deformation. Eventual failure through the shear band is a combination of grain-matrix separation, ductile matrix rupture, and grain fracture. In order to understand the effect of the composite microstructure and material inhomogeneity on deformation, two other materials are also used in the study. One is a pure tungsten and the other is an alloy of W, Ni, and Fe with the same composition as that of the matrix phase in the overall composite. The results show that the overall two-phase composite is more susceptible to the formation of shear bands than either of its constituents.

The Secondary Development of Nonlinear Viscoelastic Constitutive Model Based on ABAQUS

2011 ◽  
Vol 138-139 ◽  
pp. 466-470
Author(s):  
Long Yi ◽  
Yun Peng ◽  
Hou Quan Hong ◽  
Yu Liang Li
Keyword(s):  
Finite Element ◽  
Constitutive Model ◽  
Material Model ◽  
Secondary Development ◽  
Uniaxial Tensile ◽  
Finite Element Software ◽  
Material Constitutive Model ◽  
Nonlinear Viscoelastic ◽  
Linear Viscoelastic ◽  
Viscoelastic Constitutive Model

Based on the subroutine VUMAT, user-defined material model in the nonlinear finite element software ABAQUS/EXPLICIT, a nonlinear viscoelastic constitutive model is developed. The validify of the subroutine has been proven through the standard uniaxial tensile model. The shortage of finite element softwares which only have linear viscoelastic constitutive model is remedied. This paper presents the process of developing a material constitutive model and some useful technology. It can be referred for extending the material constitutive model in finite element softwares.

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