Constitutive model with strain softening

Department of Civil Engineering and Engineering Mechanics, University of Arizona, Tucson, AZ 85721, U.S.A.
Mathematical and Computer Modelling (Impact Factor: 2.02). 01/1987; 23(6):733-750. DOI: 10.1016/0020-7683(87)90076-X

ABSTRACT The aim or this paper is to propose a simple yet realistic model for the mechanical behavior of geologic materials such as concrete and rock. The effect of structural changes in such materials is addressed and incorporated in the theory through a tensor form of a damage variable. It is shown that formation of damage is responsible for the softening in strength observed in experiments, for the degradation of the elastic shear modulus, and for induced anisotropy. A generalized plasticity model is incorporated for the so-called topical or continuum part of the behavior, whereas the damage part is represented by the so-called stress-relieved behavior. The parameters required to define the model are identified and determined from multiaxial testing of a concrete. The predictions are compared with observed behavior for a number of stress paths. The model shows very good agreement with the observed response.

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    ABSTRACT: In order to derive general evolution laws, the authors resort to the definition of a conjugate force of damage. Based upon a loading function and a damage rule with physical meaning, the authors define this force as a factor multiplying the compliance rate occurring in the expression for dissipation energy rate. The further introduced pseudo-logarithmic damage tensor rate leads to a convenient separation of volumetric and deviatoric tensorial parts, responsible respectively for isotropic and deviatoric degradations. The authors use an elastic degradation and damage theory with a second-order tensor (secant) formulation which allows to establish simplified micro- and macro-models for degradation. The damage scalar is linked with the introduced tensors, and an additional calculation provides explicite formulas for introduced measures. In part II, the results of part I are applied in order to develop a generalized model by formulating the loading function as a particular function of the conjugate damage force and history function. The shape of the loading surface in stress space is obtained together with a damage rule and hardening/softening laws. In the case of uniaxial tension and in other simple loading cases (pure shear, pure distortion, tensile loading), the constitutive laws are obtained in closed form. A numerical test with rotation of principal axes is performed, and plotted diagrams illustrate each analyzed case. We also mention the illustration of loading paths and frictional criteria in diagrams and tables.
    International Journal of Solids and Structures 01/2001; 38(4). DOI:10.1016/S0020-7683(00)00030-5 · 2.04 Impact Factor
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    ABSTRACT: The technique of splitting grouting for dams is one of the important technical approaches to improve the inner quality of dam construction. However, the construction cost is too high with the current technological standard, which restricts the further promotion of this technology. Based on the assumption that the other conditions of construction process remained unchanged and by obeying the law of interaction between the placement of grout-hole spacing and the actual anti-seepage effect during splitting grouting, Mohr-Coulomb Hardening constitutive model was adopted in this paper on the basis of large-scale finite element numerical algorithm. Through the fluid-solid coupling computation of grout holes of different spacing, the distribution law of various factors during splitting grouting, such as the pore water pressure generated by seriflux and the stress and strain of dam, was studied first. Next, the mechanism of reinforcement and seepage of splitting grouting seriflux in soil body was revealed, and the influence of this mechanism on the stability of dam body was also investigated. Finally, the effect of splitting grouting was evaluated.
    Applied Mechanics and Materials 01/2012; 151:295-299. DOI:10.4028/
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