scholarly journals A Coupled Elastoplastic Damage Dynamic Model for Rock

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Xuelong Hu ◽  
Ming Zhang ◽  
Xiangyang Zhang ◽  
Min Tu ◽  
Zhiqiang Yin ◽  
...  
Keyword(s):  
Plastic Strain ◽  
Constitutive Model ◽  
Damage Mechanics ◽  
Yield Criterion ◽  
Triaxial Compression ◽  
Equivalent Plastic Strain ◽  
Damage Variable ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Elastoplastic Damage

Rock dynamic constitutive model plays an important role in understanding dynamic response and addressing rock dynamic problems. Based on elastoplastic mechanics and damage mechanics, a dynamic constitutive model of rock coupled with elastoplastic damage is established. In this model, unified strength theory is taken as the yield criterion; to reflect the different damage evolution law of rocks under tension and pressure conditions, the effective plastic strain and volumetric plastic strain are used to represent the compressive damage variable and the equivalent plastic strain is used to represent the tensile damage variable; the plastic hardening behavior and strain rate effect of rocks are characterized by piecewise function and dynamic increase factor function, respectively; Fortran language and LS-DYNA User-Defined Interface (Umat) are used to numerically implement the constitutive model; the constitutive model is verified by three classical examples of rock uniaxial and triaxial compression tests, rock uniaxial tensile test, and rock ballistic test. The results show that the constitutive model can describe the dynamic and static mechanical behavior of rock comprehensively.

scholarly journals Strain Rate-Dependent Constitutive and Low Stress Triaxiality Fracture Behavior Investigation of 6005 Al Alloy

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Yong Peng ◽  
Xuanzhen Chen ◽  
Shan Peng ◽  
Chao Chen ◽  
Jiahao Li ◽  
...  
Keyword(s):  
Flow Stress ◽  
Plastic Strain ◽  
Strain Rate ◽  
Fracture Behavior ◽  
Equivalent Plastic Strain ◽  
Stress Triaxiality ◽  
Tensile Tests ◽  
Uniaxial Tensile ◽  
Strain Rates ◽  
Stress States

In order to study the dynamic and fracture behavior of 6005 aluminum alloy at different strain rates and stress states, various tests (tensile tests at different strain rates and tensile shearing tests at five stress states) are conducted by Mechanical Testing and Simulation (MTS) and split-Hopkinson tension bar (SHTB). Numerical simulations based on the finite element method (FEM) are performed with ABAQUS/Standard to obtain the actual stress triaxialities and equivalent plastic strain to fracture. The results of tensile tests for 6005 Al show obvious rate dependence on strain rates. The results obtained from simulations indicate the feature of nonmonotonicity between the strain to fracture and stress triaxiality. The equivalent plastic strain reduces to a minimum value and then increases in the stress triaxiality range from 0.04 to 0.30. A simplified Johnson-Cook (JC) constitutive model is proposed to depict the relationship between the flow stress and strain rate. What is more, the strain-rate factor is modified using a quadratic polynomial regression model, in which it is considered to vary with the strain and strain rates. A fracture criterion is also proposed in a low stress triaxiality range from 0.04 to 0.369. Error analysis for the modified JC model indicates that the model exhibits higher accuracy than the original one in predicting the flow stress at different strain rates. The fractography analysis indicates that the material has a typical ductile fracture mechanism including the shear fracture under pure shear and the dimple fracture under uniaxial tensile.

scholarly journals A Multiparameter Damage Constitutive Model for Rock Based on Separation of Tension and Shear

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
YanHui Yuan ◽  
Ming Xiao
Keyword(s):  
Constitutive Model ◽  
Damage Model ◽  
Damage Mechanism ◽  
Internal Variable ◽  
Damage Variable ◽  
Tensor Form ◽  
Shear Damage ◽  
Damage Constitutive Model ◽  
Microscopic Damage ◽  
Elastoplastic Damage

By analysis of the microscopic damage mechanism of rock, a multiparameter elastoplastic damage constitutive model which considers damage mechanism of tension and shear is established. A revised general form of elastoplastic damage model containing damage internal variable of tensor form is derived by considering the hypothesis that damage strain is induced by the degeneration of elastic modulus. With decomposition of plastic strain introduced, the forms of tension damage variable and shear damage variable are derived, based on which effects of tension and shear damage on material’s stiffness and strength are considered simultaneously. Through the utilizing of Zienkiewicz-Pande criterion with tension limit, the specific form of the multiparameter damage model is derived. Numerical experiments show that the established model can simulate damage behavior of rock effectively.

scholarly journals FAILURE OF COATINGS OF TINPLATES

2015 ◽  
Vol 21 (3) ◽  
pp. 213 ◽  
Author(s):  
Emil Spisak ◽  
Miroslav Džupon ◽  
Janka Majerníková ◽  
Emília Spišáková Duľová
Keyword(s):  
Plastic Strain ◽  
Tensile Test ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Quality Test ◽  
Tin Coating ◽  
Coating Quality ◽  
Limit States ◽  
Edx Analysis ◽  
Tin Coatings

<p class="AMSmaintext">The goal of the contribution was to get the information about the way of failure of tin coatings and their causes and about behaviour of tin coatings at the limit states of deformation.  The work shows that in the maximum plastic strain area the failure of tin coating was mainly due to transversal cracks without separation of the coating particles and decohesion at the coating-substrate interface. As an additional tin coating quality test, it would be advisable to include qualitative EDX analysis of tin coating in the area of uniform and maximum plastic strain of the surface of test specimens after a uniaxial tensile test.</p>

scholarly journals Statistical Damage Constitutive Model for Cemented Sand considering the Residual Strength and Initial Compaction Phase

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Cai Tan ◽  
Ming-dao Yuan ◽  
Yong-sheng Shi ◽  
Bing-sheng Zhou ◽  
Hao Li
Keyword(s):  
Constitutive Model ◽  
Residual Strength ◽  
Damage Mechanics ◽  
Triaxial Compression ◽  
Triaxial Stress ◽  
Cemented Sand ◽  
Damage Constitutive Model ◽  
Statistical Damage Constitutive Model ◽  
Initial Compaction ◽  
Statistical Damage

Based on continuum damage mechanics and the assumption of volume invariance, a damage constitutive model of cemented sand under triaxial stress was established while considering residual strength. Statistical theory was then introduced into this model. Assuming that the microunit strength of cemented sand obeys a Weibull random distribution, an expression of microunit strength based on the Mohr–Coulomb criterion was derived. Additionally, a damage evolution equation and a statistical damage constitutive model of cemented sand under triaxial stress were established. In order to consider the nonlinear deformation and volume change in the initial pore compaction stage, the critical point reflecting the completion of the initial compaction stage was determined. This was done by applying the volume invariance assumption to the linear portion of the stress and strain curve and performing a coordinate transformation. The nonlinearity of the initial compaction stage was fitted by a quadratic function. A triaxial compression test of cemented sand was then carried out to verify this proposed method. The results show that the calculated values by the damage constitutive model fit well with the actual experimental values and that the calculated results can reflect the stress softening, residual strength, and initial compaction characteristics of cemented sand, which shows the rationality and feasibility of the model.

Study on Elastic-Plastic Damage Constitutive Model of Frozen Soil Based on Energy Dissipation Theory

2013 ◽  
Vol 423-426 ◽  
pp. 1187-1192 ◽  
Author(s):  
Zhi Min Li ◽  
Tao Liu ◽  
Zhi Li Cui
Keyword(s):  
Energy Dissipation ◽  
Constitutive Model ◽  
Damage Mechanics ◽  
Yield Criterion ◽  
Dissipation Function ◽  
Frozen Soil ◽  
Elastic Plastic ◽  
Plastic Damage ◽  
Plastic Dissipation ◽  
Damage Constitutive Model

Starting from the thermodynamics, model of frozen soil is studied by energy dissipation theory and the inside and outside the state variables is given under isothermal conditions. Damage of frozen soil is re-flecked by effective stress and damage tensor in Damage Mechanics. Dissipation function is in form of plastic dissipation function (DP yield criterion) and the damage dissipation function. And plastic dissipation function is coupled of the damage variable. Through the elastic-plastic and damage evolution, frozen soil incremental elastic-plastic damage constitutive model is made. And finite element scheme is given.

Evaluation of Mechanical and Fracture Characteristics Using Instrumented Indentation Technique

2007 ◽  
Vol 539-543 ◽  
pp. 2210-2215
Author(s):  
Jung Suk Lee ◽  
Kwang Ho Kim ◽  
Jae Hwan Han ◽  
Dong Il Kwon
Keyword(s):  
Fracture Toughness ◽  
Residual Stress ◽  
Material Characterization ◽  
Damage Mechanics ◽  
Evaluation Method ◽  
Flow Property ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Instrumented Indentation ◽  
Indentation Technique

The material characterization on the weak points of the structural systems is essential to evaluate safety accurately. However, general material characterization methods such as uniaxial tensile test and CTOD (crack tip opening displacement) test are destructive, therefore, it cannot be applied to the system in use. To overcome this problem, the material characterization using instrumented indentation technique was developed. However, current researches on instrumented indentation technique focus on the hardness measurement. The evaluation of flow property, residual stress and fracture toughness using instrumented indentation technique is not sufficiently performed. In this paper, we introduce the evaluation method of the flow property, the residual stress near the weldment and the fracture toughness developed from damage mechanics. The algorithm of flow property evaluation, the residual stress evaluation model and the fracture toughness model by using indentation were verified comparing with the experimental results.

scholarly journals Qualitative Behaviour of Elastic-Plastic Solutions for a Class of Damage Mechanics Models Near Bimaterial Interfaces: A Simple Analytical Example

2013 ◽  
Vol 2013 ◽  
pp. 1-5
Author(s):  
Sergei Alexandrov ◽  
Yusof Mustafa
Keyword(s):  
Plastic Strain ◽  
Boundary Value Problem ◽  
Damage Mechanics ◽  
Boundary Value ◽  
Equivalent Plastic Strain ◽  
Damage Parameter ◽  
Bimaterial Interface ◽  
Hard Material ◽  
Qualitative Behaviour ◽  
Elastic Plastic

The paper presents an exact analytic solution for a class of elastic-plastic models with damage evolution. The boundary value problem consists of a planar deformation comprising the simultaneous shearing and expansion of a hollow cylindrical specimen of material and involves a bimaterial interface at which the materials stick to each other. With no loss of generality for understanding the qualitative behaviour of the solution near the bimaterial interface, an extreme case when the hard material is rigid is considered. The solution is reduced to a transcendental equation for the value of the equivalent plastic strain at the bimaterial interface. This equation predicts that the equivalent plastic strain attains a maximum under certain conditions. The existence of the solution of the boundary value problem depends on the value of the damage parameter at fracture, which is a material constant. In particular, if this value is larger than the value of the damage parameter at the bimaterial interface corresponding to the maximum possible value of the equivalent strain at this interface, then no solution exists. Experimental data available in the literature are used to assess whether Lemaitre’s model is applicable.

scholarly journals A Study of Coupled Creep Damaged Constitutive Model of Artificial Frozen Soil

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Dongwei Li ◽  
Junhao Chen ◽  
Yan Zhou
Keyword(s):  
Finite Element ◽  
Constitutive Model ◽  
Damage Mechanics ◽  
Yield Criterion ◽  
Creep Damage ◽  
Confining Pressure ◽  
Frozen Soil ◽  
Finite Element Program ◽  
Finite Element Software ◽  
Frozen Clay

Artificial frozen soil is a kind of typical creep material, and the frozen clay under the unloading stress paths of high-confining pressure conforms to the improved the Zienkiewicz–Pande parabola-type yield criterion, and the Mohr–Coulomb yield function can describe the shear yield surface of artificial frozen clay under low-confining pressure. Based on the results of triaxial creep and shear tests for artificial frozen soil, the viscoplastic damage variable and evolution rule of artificial frozen clay were obtained by using the theory of viscoelastic-plastic mechanics and damage mechanics. An improved Zienkiewicz–Pande parabola-type yield criterion was used instead of a linear Newton body to obtain a coupled constitutive model of viscoelastic-plastic damage in the frozen soil under the unloading stress paths and to derive the coupling flexibility matrix for viscoelastic and viscoplastic damage. A finite element program of artificial frozen soil considering creep damage was written in the Visual Fortran 6.6A environment and embedded into the nonlinear finite element software ADINA as a user subroutine. The results of numerical simulation and laboratory testing were identical, with a maximum error of no more than 4.8%. This work shows that it is reasonable to describe the creep constitutive model of frozen soil with the viscoelastic-plastic-coupled constitutive model.

3D Mechanical Properties of the Layered Esophagus: Experiment and Constitutive Model

2006 ◽  
Vol 128 (6) ◽  
pp. 899-908 ◽  
Author(s):  
W. Yang ◽  
T. C. Fung ◽  
K. S. Chian ◽  
C. K. Chong
Keyword(s):  
Constitutive Model ◽  
Fiber Orientation ◽  
Strain Energy ◽  
Physiological State ◽  
Three Dimensional ◽  
Strain Energy Function ◽  
Esophageal Wall ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Esophageal Diseases

The identification of a three dimensional constitutive model is useful for describing the complex mechanical behavior of a nonlinear and anisotropic biological tissue such as the esophagus. The inflation tests at the fixed axial extension of 1, 1.125, and 1.25 were conducted on the muscle and mucosa layer of a porcine esophagus separately and the pressure-radius-axial force was recorded. The experimental data were fitted with the constitutive model to obtain the structure-related parameters, including the collagen amount and fiber orientation. Results showed that a bilinear strain energy function (SEF) with four parameters could fit the inflation data at an individual extension very well while a six-parameter model had to be used to capture the inflation behaviors at all three extensions simultaneously. It was found that the collagen distribution was axial preferred in both layers and the mucosa contained more collagen, which were in agreement with the findings through a pair of uniaxial tensile test in our previous study. The model was expected to be used for the prediction of stress distribution within the esophageal wall under the physiological state and provide some useful information in the clinical studies of the esophageal diseases.

Relevant Cubic Grain Plank Plastic Strain Ratio (R) the Theory Research and Experiment

2011 ◽  
Vol 243-249 ◽  
pp. 5999-6002
Author(s):  
Wen Xia Yue ◽  
Lang Wu ◽  
Li Min Cheng
Keyword(s):  
Plastic Strain ◽  
Sheet Metal ◽  
Function Theory ◽  
Strain Ratio ◽  
Metal Sheet ◽  
Quadratic Functions ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Tensor Function ◽  
Plastic Strain Ratio

This paper shows that different materials have different quadratic functions, tensor function theory can make the function of history to represent the plastic strain, which can be a sheet metal pressing does uniaxial tensile test show that the plane of sheet metal, sheet metal specimen axis and the angle between the rolling direction changes, to the metal plastic strain ratio (R) along with the changes. To explain this phenomenon, the introduction of a quadratic yield function to describe the experimental results of some of the metal sheet. This paper shows that different materials have different quadratic functions, tensor function theory can make the function of history to represent the plastic strain, which can be a sheet metal pressing does not depend on the value of history.

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