A Finite Elastoplastic Constitutive Formulation With New Co-rotational Stress-Rate and Strain-Hardening Rule

1995 ◽  
Vol 62 (3) ◽  
pp. 733-739 ◽  
Author(s):  
Z. Xia ◽  
F. Ellyin
Keyword(s):  
Constitutive Model ◽  
Strain Hardening ◽  
Complex Loading ◽  
Stress Rate ◽  
Cyclic Shear ◽  
Hardening Law ◽  
Rate Measure ◽  
Principal Directions ◽  
Constitutive Formulation ◽  
Objective Stress Rate

A constitutive model for finite elastoplastic deformations is presented. This model incorporates two novel features: first, a strain-hardening law that is applicable to complex loading paths and histories; and second, an objective stress-rate measure that is based on the spin of an orthogonal triad of material unit vectors which instantaneously coincides with the principal directions of the stress tensor. Problems of shear superposed on triaxial tension, cyclic shear deformation, and biaxial nonproportional loading are studied. It is shown that realistic predictions for the aforementioned problems are obtained by using the proposed constitutive model.

Evaluation of a simplified soil constitutive model considering implied strength and pore-water pressure generation for one-dimensional (1D) seismic site response

2020 ◽  
Vol 57 (7) ◽  
pp. 974-991 ◽  
Author(s):  
Xuan Mei ◽  
Scott M. Olson ◽  
Youssef M.A. Hashash
Keyword(s):  
Constitutive Model ◽  
Shear Strain ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Site Response ◽  
Water Pressure ◽  
Generation Model ◽  
Cyclic Shear ◽  
Centrifuge Tests ◽  
Spectral Accelerations

Pore-water pressure (PWP) generation can lead to soil softening and liquefaction of sandy soils during earthquakes, with potential influence on site response and seismic design. The authors evaluated the generalized quadratic/hyperbolic (GQ/H) constitutive model, which captures small-strain stiffness, large-strain shear strength, and is coupled with a widely used cyclic strain–based PWP generation model (termed GQ/H+u). A suite of cyclic direct simple shear tests with a range of relative densities (∼30%–80%) and effective vertical stresses (∼25–200 kPa) and dynamic centrifuge tests with liquefiable sands were used to evaluate the ability of the GQ/H+u model to simulate cyclic soil behavior. Results indicate that GQ/H+u provides reasonable estimates of PWP increase during cyclic shear, with differences between measured and computed excess PWP ratios (ru) for both element and centrifuge tests generally smaller than 0.1. Computed spectral accelerations are comparable to centrifuge test measurements, with almost no bias at medium to long periods (T > 0.4 s) when the computed maximum shear strain (γmax) was smaller than the limit shear strain (γlimit). When computed ru > 0.8 and computed γmax > γlimit, spectral accelerations may be underestimated at both short and long periods as dilative behavior is not captured by GQ/H+u.

Transversely isotropic constitutive model of the polypropylene separator based on Rich-Hill elastoplastic constitutive theory

2020 ◽  
pp. 1-26
Author(s):  
Guicheng Zhao ◽  
Huifeng Xi ◽  
Jinbiao Yang
Keyword(s):  
Constitutive Model ◽  
Lithium Ion Batteries ◽  
Large Deformation ◽  
Yield Criterion ◽  
Lithium Ion ◽  
Transversely Isotropic ◽  
Porous Polymer ◽  
Constitutive Theory ◽  
Elastic Plastic ◽  
Hardening Law

Abstract The polypropylene (PP) separator is a kind of transversely isotropic porous polymer film, and it is a key component of lithium-ion batteries. The mechanical properties of the separator affect the strength and security of lithium-ion batteries directly. However, the anisotropy behaviors of the separator remain unclear, which has led to inaccuracy of failure behaviors in lithium-ion battery. A large deformation elastic-plastic constitutive model of the PP separator was developed with the Rich-Hill large deformation elastoplastic constitutive theory. Besides, the hardening law of the PP separator was established according to the Hill yield criterion. The constitutive model accurately captured the anisotropy behaviors and the elastic-plastic process considering the large deformation of the separator. Numerical examples for model validation were presented and in good agreement with stress-strain data of tests up to the hardening stage.

A Characteristic and a Precisely Constitutive Model for Undrained Clay

2020 ◽  
Vol 975 ◽  
pp. 203-207
Author(s):  
Shih Tsung Hsu ◽  
Wen Chi Hu ◽  
Yu Heng Lin ◽  
Zhuo Ling
Keyword(s):  
Shear Strength ◽  
Plastic Strain ◽  
Constitutive Model ◽  
Strain Hardening ◽  
Undrained Shear Strength ◽  
Triaxial Tests ◽  
Stress Strain ◽  
Proposed Model ◽  
Taipei Basin ◽  
Undrained Shear

Constitutive models for soils are usually adopted in numerical method to analyze the behavior of geotechnical structures. This study performs a series of consolidated-undrained triaxial tests to establish the stress-strain curve of clay. A constitutive model that considers continuous strain hardening-softening is proposed based on the results of triaxial tests. Triaxial test results reveal that undrained shear strength linearly increases with an increase in consolidated pressure , the normalized undrained shear strength is about 0.52 not only for this study but also for the other two cases around Taipei Basin. Due to undrained condition, an associated flow rule between plastic strain increment and stress tensor is adopted. As accumulative plastic strain or/and consolidated pressure change, the mobilized undrained shear strength also changes. All parameters needed for the proposed model can be expressed as a function of undrained shear strength Su, The mobilized undrained shear strength for the proposed model during strain hardening-softening can be in term of accumulative plastic strain. This model can calculate the stress-strain curves of clayed soils accurately.

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