scholarly journals Elastoplastical Analysis of the Interface between Clay and Concrete Incorporating the Effect of the Normal Stress History

2013 ◽  
Vol 2013 ◽  
pp. 1-12 ◽  
Author(s):  
Zhao Cheng ◽  
Zhao Chunfeng ◽  
Gong Hui
Keyword(s):  
Normal Stress ◽  
Load Transfer ◽  
Shear Behaviour ◽  
Model Parameters ◽  
Stress History ◽  
Hardening Parameter ◽  
Using Data ◽  
Energy Dissipated ◽  
Interaction Problem ◽  
Soil Interface

The behaviour of the soil-structure interface is crucial to the design of a pile foundation. Radial unloading occurs during the process of hole boring and concrete curing, which will affect the load transfer rule of the pile-soil interface. Through large shear tests on the interface between clay and concrete, it can be concluded that the normal stress history significantly influences the shear behaviour of the interface. The numerical simulation of the bored shaft-soil interaction problem requires proper modelling of the interface. By taking the energy accumulated on the interface as a hardening parameter and viewing the shearing process of the interface as the process of the energy dissipated to do work, considering the influence of the normal stress history on the shearing rigidity, a mechanical model of the interface between clay and concrete is proposed. The methods to define the model parameters are also introduced. The model is based on a legible mathematical theory, and all its parameters have definite physical meaning. The model was validated using data from a direct shear test; the validation results indicated that the model can reproduce and predict the mechanical behaviour of the interface between clay and concrete under an arbitrary stress history.

scholarly journals Non-orthogonal elastoplastic constitutive model for sand with dilatancy

2021 ◽  
Author(s):  
Jingyu Liang ◽  
Dechun Lu ◽  
Xiuli Du ◽  
Wei Wu ◽  
Chao Ma
Keyword(s):  
Constitutive Model ◽  
Plastic Flow ◽  
Flow Direction ◽  
Model Performance ◽  
Yield Function ◽  
Flow Rule ◽  
Shear Process ◽  
Hardening Parameter ◽  
Elastoplastic Constitutive Model ◽  
Plastic Flow Rule

A non-orthogonal elastoplastic constitutive model for sand with dilatancy is presented in the characteristic stress space. Dilatancy of sand is represented by the direction of plastic flow, which can be directly determined by applying the non-orthogonal plastic flow rule to an improved elliptic yield function. A new hardening parameter is developed to describe the contractive and dilative volume change during the shear process, which is co-ordinated with the non-orthogonal plastic flow direction. The combination of the non-orthogonal plastic flow rule and the proposed hardening parameter renders the proposed model with the ability to reasonably describe the stress-strain relationship of sand with dilatancy. The model performance is evaluated by comparing with the experimental data of sand under triaxial stress conditions.

scholarly journals A Novel Flow Model of Strain Hardening and Softening for Use in Tensile Testing of a Cylindrical Specimen at Room Temperature

Materials ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 4876
Author(s):  
Mohd Kaswandee Razali ◽  
Man Soo Joun ◽  
Wan Jin Chung
Keyword(s):  
Flow Stress ◽  
Strain Hardening ◽  
Tensile Testing ◽  
Room Temperature ◽  
Flow Model ◽  
Cylindrical Specimen ◽  
Fourth Power ◽  
Strain Hardening Exponent ◽  
Small Strains ◽  
Hardening Parameter

We develop a new flow model based on the Swift method, which is both versatile and accurate when used to describe flow stress in terms of strain hardening and damage softening. A practical issue associated with flow stress at room temperature is discussed in terms of tensile testing of a cylindrical specimen; we deal with both material identification and finite element predictions. The flow model has four major components, namely the stress before, at, and after the necking point and around fracture point. The Swift model has the drawback that not all major points of stress can be covered simultaneously. A term of strain to the third or fourth power (the “second strain hardening exponent”), multiplied and thus controlled by a second strain hardening parameter, can be neglected at small strains. Any effect of the second strain hardening exponent on the identification of the necking point is thus negligible. We use this term to enhance the flexibility and accuracy of our new flow model, which naturally couples flow stress with damage using the same hardening constant as a function of damage. The hardening constant becomes negative when damage exceeds a critical value that causes a drastic drop in flow stress.

Self-Consistent Approaches and Strain Heterogeneities in Two-Phase Elastoplastic Materials

1994 ◽  
Vol 47 (1S) ◽  
pp. S66-S76 ◽  
Author(s):  
Michel Bornert ◽  
Eveline Herve´ ◽  
Claude Stolz ◽  
Andre´ Zaoui
Keyword(s):  
Deformation Theory ◽  
Shear Bands ◽  
Local Concentration ◽  
Two Phase ◽  
Self Consistent ◽  
Measured Strain ◽  
Elastoplastic Materials ◽  
Hardening Parameter ◽  
Analytical Result ◽  
Definition Of

The Generalized Self Consistent Scheme [GSCS] extended to the nonlinear case with help of a deformation theory of elastoplasticity is used to predict the strain heterogeneities that spread out in two phase elastoplastic materials submitted to a monotonic uniaxial load. Materials with different microstructural morphologies are considered. The single composite inclusion of the GSCS is an accurate representation of “matrix/inclusion” microstructures but it does not give a sufficient representation of the considered morphologies. That’s why this model is extended to more general cases by using two or even more different spherical composite inclusions: local concentration fluctuations and local morphological inversions can then be modeled. The nonlinear extension is also modified: the composite inclusions are discretized into several concentric layers in order to take into better account the strain gradient along the radius and a new definition of the work-hardening parameter of each of these layers is proposed. The elastoplastic strain field in the single composite inclusion is also computed numerically by means of finite element methods and compared to the analytical result. Unfortunately, these modifications do not basically modify the strain heterogeneity predictions of the GSCS, which widely underestimate the measured strain heterogeneities in most of the cases. In fact, the inaccuracy of the GSCS in these cases is basically due to the appearance of long range shear bands that cannot be described by a local self-consistent approach.

On Measuring the Near-Tip Plastic Strain Singularity

1990 ◽  
Vol 57 (4) ◽  
pp. 901-905 ◽  
Author(s):  
Sundar M. Kamath ◽  
Kyung S. Kim
Keyword(s):  
Focal Plane ◽  
Mapping Technique ◽  
Simple Relationship ◽  
Finite Area ◽  
Hardening Material ◽  
Experimental Parameters ◽  
Hardening Parameter ◽  
Continuous Trace ◽  
Metallic Specimen ◽  
Hrr Singularity

A recently developed experimental method, stress intensity factor tracer, is extended to measure the strength, J, of the HRR singularity for near-tip plastic deformation. Focal-plane mapping of the HRR field shows that the light intensity, I, collected on a finite area of the focal plane has a simple relationship with J as I = βJ2n/(2n+1). The constant, β, is a product of several experimental parameters and “n” is the hardening parameter of a power-law hardening material. The focal-plane mapping technique is also capable of estimating the shape and size of the HRR-field dominant region for a relatively thin (<10mm) metallic specimen. In addition, a continuous trace of the J variation can be monitored using a single, stationary photodetector. Because the measurement value of this method is independent of crack-tip motion, the transition of HRR singularity from stationary to moving can also be studied. In this paper, the theoretical analysis of the method is presented.

Singular Fields in Plane-Strain Penetration

1991 ◽  
Vol 58 (4) ◽  
pp. 910-915 ◽  
Author(s):  
David Durban ◽  
Omri Rand
Keyword(s):  
Boundary Layer ◽  
Strain Rate ◽  
Plane Strain ◽  
Constitutive Relation ◽  
Solid Material ◽  
Material Behavior ◽  
Wall Friction ◽  
Friction Factors ◽  
Hardening Parameter ◽  
Strain Rate Hardening

Local singular fields are investigated in the vicinity of the vertex of a sharp wedge that penetrates a viscous solid. Material behavior is modeled by the usual powerlaw constitutive relation. Wall friction is accounted for by imposing friction factors along the walls of the wedge. The case of a Newtonian fluid is investigated analytically, and sample numerical results are presented for nonlinear strain rate hardening. It is shown that the exponent of strain rate singularity increases as the wedge becomes sharper and smoother. Increasing the hardening parameter also results in a stronger strain rate singularity. High levels of wall friction induce an intensive shear boundary layer near the wall.

Comparison of Three Methods for Material Hardening Parameter Identification under Cyclic Tension-Compression Loadings: Roll Levelling Case Study

2015 ◽  
Vol 651-653 ◽  
pp. 957-962 ◽  
Author(s):  
Elena Silvestre ◽  
Eneko Sáenz de Argandoña ◽  
Lander Galdos ◽  
Joseba Mendiguren
Keyword(s):  
Parameter Identification ◽  
Kinematic Hardening ◽  
High Strength Steels ◽  
High Strength ◽  
Material Model ◽  
Forming Process ◽  
Element Analysis ◽  
Transient Behaviour ◽  
Cyclic Tension ◽  
Hardening Parameter

The roll levelling is a forming process used to remove the residual stresses and imperfections of metal strips by means of plastic deformations. The process is especially important to avoid final geometrical errors when coils are cold formed or when thick plates are cut by laser. In the last years, and due to the appearance of high strength materials such as Ultra High Strength Steels, machine design engineers are demanding a reliable tool for the dimensioning of the levelling facilities. In response to this demand, Finite Element Analysis is becoming an important technique able to lead engineers towards facilities optimization through a deeper understanding of the process.In this scenario, the accuracy and quality of the simulation results are highly dependent on the accuracy of the implemented material model. During roll levelling process, the sheet metal is subjected to cyclic tensile-compressive deformations, therefore a proper constitutive. model which considers the phenomena that occurs during cyclic loadings, such as the Bauschinger effec, work hardeningt and the transient behaviour, is needed. The prediction of all these phenomena which affect the final shape of the product are linked to the hardening rule.In the present paper, the roll levelling simulation of a DP1000 steel is performed using a combined isotropic-kinematic hardening formulation introduced by Chaboche and Lemaitre since its simplicity and its ability to predict the Bauschinger effect. The model has been fitted to the experimental curves obtained from a cyclic tension-compression test, which has been performed by means of a special tool developed to avoid the buckling of the specimen during compressive loadings. The model has been fitted using three different material hardening parameter identification methodologies which have been compared.

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