Viscoelastic material response with a fractional-derivative constitutive model

AIAA Journal ◽  
1996 ◽  
Vol 34 (3) ◽  
pp. 596-600 ◽  
Author(s):  
William P. Baker ◽  
Lloyd B. Eldred ◽  
Anthony N. Palazotto
Keyword(s):  
Constitutive Model ◽  
Fractional Derivative ◽  
Viscoelastic Material ◽  
Material Response

A Dislocation Density Based Constitutive Model for Cyclic Deformation

1996 ◽  
Vol 118 (4) ◽  
pp. 441-447 ◽  
Author(s):  
Y. Estrin ◽  
H. Braasch ◽  
Y. Brechet
Keyword(s):  
Cyclic Loading ◽  
Dislocation Density ◽  
Constitutive Model ◽  
Constitutive Equations ◽  
Cyclic Deformation ◽  
Internal Variables ◽  
Density Evolution ◽  
Alloy 800H ◽  
Material Response ◽  
Dislocation Densities

A new constitutive model describing material response to cyclic loading is presented. The model includes dislocation densities as internal variables characterizing the microstructural state of the material. In the formulation of the constitutive equations, the dislocation density evolution resulting from interactions between dislocations in channel-like dislocation patterns is considered. The capabilities of the model are demonstrated for INCONEL 738 LC and Alloy 800H.

A variable-order viscoelastic constitutive model under constant strain rate

2020 ◽  
Author(s):  
Yao Wang ◽  
Dagang Sun ◽  
Zhanlong Li ◽  
Yuan Qin ◽  
Bao Sun
Keyword(s):  
Constitutive Model ◽  
Strain Rate ◽  
Fractional Order ◽  
Viscoelastic Material ◽  
Constitutive Models ◽  
Constant Strain Rate ◽  
Variable Order ◽  
Hyper Elastic ◽  
Material Coefficient ◽  
Viscoelastic Coefficient

The traditional viscoelastic constitutive models encounter the problems of massive parameters and ambiguous physical meanings. A new concept of variable-order viscoelastic constitutive (called VOVC) model is put forward based on the constant fractional-order constitutive model and the viscoelastic theory. The determination methods of the two parameters in the VOVC model, including the material coefficient and the viscoelastic coefficient, are discussed both in the tensile and the resilient processes. The comparisons are made between the VOVC model and the traditional constitutive models i.e. the constant fractional-order Kelvin-Voigt (CFKV) model, the Zhu-wang-tang nonlinear thermo-viscoelastic constitutive (ZWT) model and the Ogden nonlinear hyper-elastic (Ogden) model. The results show that the VOVC model with the constant material coefficient and the variable viscoelastic coefficient predicts the whole evolution of the constitutive behavior of the viscoelastic material under the constant strain rate more precisely. The constant material coefficient in the VOVC model means the stiffness of the viscoelastic material. The variable viscoelastic coefficient in the model means the distribution of the elasticity and viscosity. The VOVC model contains a simpler structure, fewer parameters, clearer physical meanings and higher precision.

scholarly journals Overview and conceptual constitutive framework for pellet-based buffer materials

2020 ◽  
Vol 195 ◽  
pp. 02013
Author(s):  
Giulia M. Ghiadistri ◽  
Lidija Zdravkovic ◽  
David M. Potts ◽  
Aikaterini Tsiampousi
Keyword(s):  
Constitutive Model ◽  
Nuclear Waste ◽  
Waste Disposal ◽  
Structural Investigation ◽  
Nuclear Waste Disposal ◽  
Material Testing ◽  
High Density ◽  
Compacted Clay ◽  
Material Response ◽  
Buffer Material

Buffer materials for nuclear waste disposal applications generally consist of blocks made of highly expansive compacted clay. However, high-density pellets of bentonite are being evaluated as an alternative buffer material for waste isolation. The material response of pellet-based buffers may be quite different from that of compacted buffers, because of the peculiar discontinuous porosity presented. An overview of the literature available on pellet-based buffers is presented and, in particular, two main topics are discussed: firstly, the characteristics of the fabric of the pellets that can be observed through techniques of micro-structural investigation, secondly, the most important behavioural features that can be seen during material testing. Additionally, the constitutive frameworks that have already been developed specifically for pellets are also reviewed. The overall objective of the paper is to highlight the differences between compacted and pellet-based bentonite buffers, in order to propose suitable assumptions to start developing a constitutive model for the latter.

A generalised fractional derivative approach to viscoelastic material properties measurement

2005 ◽  
Vol 164 (2) ◽  
pp. 493-506 ◽  
Author(s):  
J.J. de Espı́ndola ◽  
João M. da Silva Neto ◽  
Eduardo M.O. Lopes
Keyword(s):  
Fractional Derivative ◽  
Viscoelastic Material ◽  
Material Properties
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