scholarly journals A method for calculating differential constitutive equation of linear viscoelastic composite model

2021 ◽  
Vol 104 (2) ◽  
pp. 003685042110232
Author(s):  
Peng Peihuo
Keyword(s):  
Constitutive Equation ◽  
Linear Differential Operator ◽  
Viscoelastic Model ◽  
Viscoelastic Composite ◽  
Matrix Operations ◽  
Linear Viscoelastic ◽  
Actual Material ◽  
Linear Differential ◽  
Independent Path ◽  
Strain Equation

The stress–strain behaviors of viscoelastic materials are often simulated using a model composed of various combinations of springs and dampers. With the increase in the number of springs and dampers, the viscoelastic characteristics of the model will approach those of the actual material. This study discusses how to obtain the differential constitutive equation of a viscoelastic model composed of any number of springs and dampers. First, the general viscoelastic model is regarded as the combination of various Kelvin units. The viscoelastic model is then transformed into a digraph. Based on the relationships between the independent path of the digraph and the strain equation of the viscoelastic model and between the closed enclosure and the stress equation, the derivation of the constitutive equation is transformed into operations involving the incidence matrix of the digraph. Finally, the coefficients of the linear differential operator of the constitutive equation of the viscoelastic model can be obtained by block matrix operations. This method is suitable for computer programming and has a certain significance for accurately constructing viscoelastic models of engineering materials.

Application of a Viscoelastic Model for Polyester Mooring

2010 ◽  
Author(s):  
J. W. Kim ◽  
J. H. Kyoung ◽  
A. Sablok
Keyword(s):  
Material Properties ◽  
Viscoelastic Model ◽  
Practical Method ◽  
Time Dependent ◽  
Mooring Line ◽  
New Model ◽  
Global Performance ◽  
Excitation Period ◽  
Linear Viscoelastic ◽  
Floating Platforms

A new practical method to simulate time-dependent material properties of polyester mooring line is proposed. The time-dependent material properties of polyester rope are modeled with a standard linear solid (SLS) model, which is one of the simplest forms of a linear viscoelastic model. The viscoelastic model simulates most of the mechanical properties of polyester rope such as creep, strain-stress hysteresis and excitation period-dependent stiffness. The strain rate-stress relation of the SLS model has been re-formulated to a stretch-tension relation, which is more suitable for implementation into global performance and mooring analyses tools for floating platforms. The new model has been implemented to a time-domain global performance analysis software and applied to simulate motion of a spar platform with chain-polyester-chain mooring system. The new model provides accurate platform offset without any approximation on the mean environmental load and can simulate the transient effect due to the loss of a mooring line during storm conditions, which has not been possible to simulate using existing dual-stiffness models.

A non-linear viscoelastic model with structure-dependent relaxation times

1976 ◽  
Vol 1 (2) ◽  
pp. 147-157 ◽  
Author(s):  
D. Acierno ◽  
F.P. La Mantia ◽  
G. Marrucci ◽  
G. Rizzo ◽  
G. Titomanlio
Keyword(s):  
Relaxation Times ◽  
Viscoelastic Model ◽  
Non Linear ◽  
Linear Viscoelastic ◽  
Linear Viscoelastic Model

STRESS RELAXATION OF MAGNETORHEOLOGICAL FLUIDS

2002 ◽  
Vol 16 (17n18) ◽  
pp. 2655-2661
Author(s):  
W. H. LI ◽  
G. CHEN ◽  
S. H. YEO ◽  
H. DU
Keyword(s):  
Stress Relaxation ◽  
Viscoelastic Model ◽  
Relaxation Modulus ◽  
Damping Function ◽  
Mr Fluids ◽  
Large Step ◽  
Linear Viscoelastic ◽  
Predicted Values ◽  
Two Parameters ◽  
Step Strain

In this paper, the experimental and modeling study and analysis of the stress relaxation characteristics of magnetorheological (MR) fluids under step shear are presented. The experiments are carried out using a rheometer with parallel-plate geometry. The applied strain varies from 0.01% to 100%, covering both the pre-yield and post-yield regimes. The effects of step strain, field strength, and temperature on the stress modulus are addressed. For small step strain ranges, the stress relaxation modulus G(t,γ) is independent of step strain, where MR fluids behave as linear viscoelastic solids. For large step strain ranges, the stress relaxation modulus decreases gradually with increasing step strain. Morever, the stress relaxation modulus G(t,γ) was found to obey time-strain factorability. That is, G(t,γ) can be represented as the product of a linear stress relaxation G(t) and a strain-dependent damping function h(γ). The linear stress relaxation modulus is represented as a three-parameter solid viscoelastic model, and the damping function h(γ) has a sigmoidal form with two parameters. The comparison between the experimental results and the model-predicted values indicates that this model can accurately describe the relaxation behavior of MR fluids under step strains.

A non-linear viscoelastic model for sediments flocculated in the presence of seawater salts

2015 ◽  
Vol 482 ◽  
pp. 500-506 ◽  
Author(s):  
Christian Goñi ◽  
Ricardo I. Jeldres ◽  
Pedro G. Toledo ◽  
Anthony D. Stickland ◽  
Peter J. Scales
Keyword(s):  
Viscoelastic Model ◽  
Non Linear ◽  
Linear Viscoelastic ◽  
Linear Viscoelastic Model

scholarly journals Influence of Couple Stresses and Thermophoresis on Free Convective Heat and Mass Transfer of Viscoelastic Fluid.

2020 ◽  
Vol 17 ◽  
pp. 50-63
Author(s):  
N. T. M. Eldabe ◽  
Ahmed Refaie Ali ◽  
Gamil Ali Shalaby
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Convective Heat ◽  
Newtonian Fluid ◽  
Numerical Solutions ◽  
Viscoelastic Model ◽  
Skin Friction Coefficient ◽  
Physical Parameters ◽  
Couple Stresses ◽  
Linear Differential

A theoretical study has been developed to investigate the influence of thermophoresis and couple stresses on the steady flow of non-Newtonian fluid with free convective heat and mass transfer over a channel bounded by two permeable plates. The considered non-Newtonian fluid follows a viscoelastic model. The problem is modulated mathematically by a system of non-linear differential equations pertaining to describe the continuity, momentum, energy, and concentration. These equations involve the effects of viscous dissipation and chemical reaction. The numerical solutions of the dimensionless equations are found as a function of the physical parameters of this problem. The numerical formulas of the velocity (u), temperature Φ and concentration Θ as well as skin friction coefficient T*, Nusselt number(Nu) and Sherwood number(Sh) are computed. The physical parameter's effects of the problem on these formulas are described and illustrated graphically through some figures and tables. It is observed that any increase in the thermophoretic parameter T leads to reduce in velocity profiles as well as concentration layers. In contrast, the velocity increases with increasing the couple stresses inverse parameter.

scholarly journals A posteriori error estimates for elliptic boundary-value problems

1985 ◽  
Vol 39 (2) ◽  
pp. 159-168
Author(s):  
W. L. Chan
Keyword(s):  
Boundary Value Problems ◽  
Error Estimates ◽  
Linear Differential Operator ◽  
Elliptic Boundary ◽  
Boundary Value ◽  
A Posteriori Error Estimates ◽  
Posteriori Error ◽  
A Posteriori ◽  
Elliptic Boundary Value ◽  
Linear Differential

AbstractA posteriori error estimates for a class of elliptic unilateral boundary value problems are obtained for functions satisfying only part of the boundary conditions. Next, we give an alternative approach to the a posteriori error estimates for self-adjoint boundary value problems developed by Aubin and Burchard. Further, we are able to construct an alternative estimate with mild additional assumptions. An example of a linear differential operator of order 2k is given.

scholarly journals Modelling liver tissue properties using a non-linear viscoelastic model ror surgery simulation

2002 ◽  
Vol 12 ◽  
pp. 146-153 ◽  
Author(s):  
J.-M. Schwartz ◽  
M. Dellinger ◽  
D. Rancourt ◽  
C. Moisan ◽  
D. Laurendeau
Keyword(s):  
Liver Tissue ◽  
Viscoelastic Model ◽  
Surgery Simulation ◽  
Tissue Properties ◽  
Non Linear ◽  
Linear Viscoelastic ◽  
Linear Viscoelastic Model
Sign in / Sign up

Export Citation Format

Share Document