Duncan-Chang Nonlinear Elastic Model Considered Loess Structure

2011 ◽  
Vol 90-93 ◽  
pp. 176-181
Author(s):  
Chang Lu Chen ◽  
Sheng Jun Shao ◽  
Lin Ma
Keyword(s):  
Nonlinear Model ◽  
Stress Ratio ◽  
Structural Parameters ◽  
Strain Curve ◽  
Triaxial Tests ◽  
Model Parameters ◽  
Elastic Model ◽  
Stress Strain ◽  
Nonlinear Elastic ◽  
Intact Loess

Duncan-Chang nonlinear model has been modified and applied to the structural loess calculation. Based on structural studies and conventional triaxial tests, this paper has analyzed the mechanical properties of intact loess and the relationship between the stress ratio structural parameters and the strain, then the expression of generalized shear strain and stress ratio structural parameters are given to facilitate the engineering applications. On this basis, the stress-strain curve of intact loess was corrected by the use of the stress ratio structural parameters. The form of the intact loess stress-strain curves which have been revised has changed hardening from the softening or weak softening. The results show that the modified stress-strain curves of intact loess can apply Duncan- Chang nonlinear model to calculate and the model parameters are reasonable and effective. This method provides Duncan-Chang nonlinear model which is widely used in engineering with a new ways and means in intact structural loess application.

Evaluation of a Pseudo-Elastic Model for the Mullins Effect

2004 ◽  
Vol 32 (3) ◽  
pp. 120-145 ◽  
Author(s):  
W. V. Mars
Keyword(s):  
Pure Shear ◽  
Strain Curve ◽  
Elastic Behavior ◽  
Elastic Model ◽  
Mullins Effect ◽  
Stress Strain ◽  
Finite Element Program ◽  
Simple Tension ◽  
Element Program ◽  
Nonlinear Elastic

Abstract Typically, the stress-strain response in filled rubbers depends strongly on the maximum loading previously encountered. The phenomenon, known as the Mullins effect, can be idealized for many purposes as an instantaneous and irreversible softening of the stress-strain curve that occurs whenever the load increases beyond its prior all-time maximum value. At times when the load is less than a prior maximum, nonlinear elastic behavior prevails. Ogden and Roxburgh proposed an empirical model capable of describing this phenomenon, based on a pseudo-elastic concept. Their model, with minor adaptations, has recently been implemented in a commercial finite element program. This paper demonstrates the effectiveness of the implemented model for several benchmark cases including uniform hydrostatic loading, simple tension, pure shear, and equibiaxial tension. The paper also compares model predictions with experimental results for a series of experiments conducted with various combinations of axial tension/compression and torsion loading.

scholarly journals Black rubber and the non-linear elastic response of scale invariant solids

2020 ◽  
Vol 2020 (9) ◽  
Author(s):  
Matteo Baggioli ◽  
Víctor Cáncer Castillo ◽  
Oriol Pujolàs
Keyword(s):  
Strain Curve ◽  
Effective Field ◽  
Elastic Response ◽  
Elastic Behaviour ◽  
Scale Invariant ◽  
Stress Strain ◽  
Nonlinear Stress ◽  
Hyper Elastic ◽  
Simple Class ◽  
Nonlinear Elastic

Abstract We discuss the nonlinear elastic response in scale invariant solids. Following previous work, we split the analysis into two basic options: according to whether scale invariance (SI) is a manifest or a spontaneously broken symmetry. In the latter case, one can employ effective field theory methods, whereas in the former we use holographic methods. We focus on a simple class of holographic models that exhibit elastic behaviour, and obtain their nonlinear stress-strain curves as well as an estimate of the elasticity bounds — the maximum possible deformation in the elastic (reversible) regime. The bounds differ substantially in the manifest or spontaneously broken SI cases, even when the same stress- strain curve is assumed in both cases. Additionally, the hyper-elastic subset of models (that allow for large deformations) is found to have stress-strain curves akin to natural rubber. The holographic instances in this category, which we dub black rubber, display richer stress- strain curves — with two different power-law regimes at different magnitudes of the strain.

The Studies of Rock Damage Softening Statistical Constitutive Model under True Triaxial Stress State

2014 ◽  
Vol 580-583 ◽  
pp. 312-315
Author(s):  
Hui Mei Zhang ◽  
Xiang Miao Xie ◽  
Geng She Yang
Keyword(s):  
Constitutive Model ◽  
Strain Curve ◽  
Stress Path ◽  
Complex Stress ◽  
Model Parameters ◽  
Stress Strain ◽  
Deformation And Failure ◽  
True Triaxial ◽  
Complex Stress Path ◽  
The Impact

From the feature of rock micro-unit failure obeys Poisson random distribution, the damage softening statistical constitutive of was established under true triaxial confinement based on D-P criterion, so the impact of the intermediate principal stress on rock deformation and failure was considered in theory, and the actual engineering rock complex stress path evolution was reflected more realistically. Furthermore, according to the geometrical conditions of stress-strain relationship, the theoretical relationship between constitutive model parameters and the stress-strain curve characteristic parameters during the process of rock softening and deforming, which enhance the adaptability of the model. Finally, the rationality of the model verified by the measured data.

A new nonlinear polyconvex orthotropic material model for the robust simulation of technical fabrics in civil engineering applications at large strains – Validation with large-scale experiment/Ein neues polykonvexes orthotropes Materialmodell zur robusten Simulation von Textilmembranen im Bauingenieur- wesen unter Berücksichtigung großer Deformationen – Validierung anhand eines Großbauteilversuchs

Bauingenieur ◽  
2019 ◽  
Vol 94 (12) ◽  
pp. 488-497
Author(s):  
Mehran Motevalli ◽  
Jörg Uhlemann ◽  
Natalie Stranghöner ◽  
Daniel Balzani
Keyword(s):  
Nonlinear Model ◽  
Orthotropic Material ◽  
Large Scale ◽  
Real Life ◽  
Material Model ◽  
Woven Fabric ◽  
Model Parameters ◽  
Elastic Model ◽  
Engineering Applications ◽  
Strain Paths

Abstract A polyconvex orthotropic material model is proposed for the simulation of tensile membrane structures. The notion of anisotropic metric tensors is employed in the formulation of the polyconvex orthotropic term which allows for the description of the interaction of the warp and fill yarns. The model is adjusted to the stress-strain paths of uni- and biaxial tensile tests of a woven fabric and the results are compared with the linear elastic model. The lateral contraction in the uniaxial loading case is taken into account to also capture the strong crosswise interactions. An increased number of load cycles is considered in the experiments to reach a saturated elastic state of the material. A new method is proposed enabling in principle the identification of unique (linear) stiffness parameters by previously identifying the (nonlinear) model parameters. Eventually, the proposed nonlinear model contains only 4 material parameters to be identified for the individual membrane material. Moreover, a new large-scale experimental setting is presented which allows for the validation of the proposed model response in real-life engineering applications. The numerical robustness of the model is tested in an advanced simulation of a large roof structure under application of realistic boundary conditions.

Experimental Study on Parameters of Duncan-Chang Model for Cement-Soil

2013 ◽  
Vol 641-642 ◽  
pp. 403-409
Author(s):  
Cai Fu Qian ◽  
Xin Jiang Song ◽  
Jie Wu ◽  
Wei Li
Keyword(s):  
Experimental Study ◽  
Calculation Method ◽  
Confining Pressure ◽  
Elastic Theory ◽  
Triaxial Tests ◽  
Stress Strain ◽  
Pressure Decrease ◽  
Cement Soil ◽  
Nonlinear Elastic ◽  
Chang Model

The conventional triaxial tests for cement-soil show stronger soften characteristics of cement-soil under low confining pressure. The soften character is weaken as confining pressure decrease. For adopting Duncan-Chang hyperbola model to obtain parameters of cement-soil, the model cannot include the stress-strain soften characteristics of cement-soil, and must be discussed. The paper studies on parameters of Duncan-Chang model using generalized Hooke law and nonlinear elastic theory. The researches show the parameters of k and n are unrelated to soften characteristics of cement-soil; the relation of Rf and σ3 is given by the soften characteristics, Rf influence the soften process directly. The calculation method could be used in E-u model, and has good practical value.

scholarly journals Study on Damage Statistical Constitutive Model of Triaxial Compression of Acid-Etched Rock under Coupling Effect of Temperature and Confining Pressure

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7414
Author(s):  
Youliang Chen ◽  
Peng Xiao ◽  
Xi Du ◽  
Suran Wang ◽  
Zhoulin Wang ◽  
...  
Keyword(s):  
Constitutive Model ◽  
Coupling Effect ◽  
Triaxial Compression ◽  
Strain Curve ◽  
Confining Pressure ◽  
Effect Of Temperature ◽  
Acid Etching ◽  
Model Parameters ◽  
Stress Strain Curve ◽  
Stress Strain

Based on Lemaitre’s strain equivalence hypothesis theory, it is assumed that the strength of acid-etching rock microelements under the coupling effect of temperature and confining pressure follows the Weibull distribution. Under the hypothesis that micro-element damage meets the D-P criterion and based on continuum damage mechanics and statistical theory, chemical damage variables, thermal damage variables and mechanical damage variables were introduced in the construction of damage evolution equations and constitutive models for acid-etching rocks considering the coupled effects of temperature and confining pressure. The required model parameters were obtained by theoretical derivation, and the model was verified based on the triaxial compression test data of granite. Comparing the experimental stress-strain curve with the theoretical stress-strain curve, the results show that they were in good agreement. By selecting reasonable model parameters, the damage statistical constitutive model can accurately reflect the stress-strain curve characteristics of rock in the process of triaxial compression. The comparison between the experimental and theoretical results also verifies the reasonableness and reliability of the model. This model provides a new rock damage statistical constitutive equation for the study of rock mechanics and its application in engineering, and has certain reference significance for rock underground engineering.

Plasticity Model of Extruded Peanuts under Mechanical Pressing

2011 ◽  
Vol 55-57 ◽  
pp. 20-25
Author(s):  
Xiao Zheng ◽  
Ya Xin Zhang ◽  
Guo Xiang Lin ◽  
Zhi Xian Sun
Keyword(s):  
Constitutive Equations ◽  
Inverse Method ◽  
Yield Criterion ◽  
Strain Curve ◽  
Model Parameters ◽  
Plasticity Model ◽  
Stress Strain ◽  
Relative Deviation ◽  
Maximum Relative Deviation ◽  
Mechanical Pressing

The experiments for stress—strain and confined pressing of granular peanuts by uniaxial pressing were carried out. The results show that granular peanuts conform to the model of three power curve. By using of Kuhn`s yield criterion, plasticity constitutive equations of granular peanuts were developed. The model parameters were determined from experimental stress—strain curve using an inverse method. The maximum relative deviation between the measured and the simulated value of strain is 5.4%, and the average relative deviation is 3.5%. Results indicated that the plasticity constitutive equations can describe the plastic deformation for extruded peanut, and Kuhn`s yield criterion can be used as theoretical basis for plasticity model of granular peanuts.<b></b>

scholarly journals Transformation of Test Data for the Specification of a Viscoelastic Marlow Model

Solids ◽  
2020 ◽  
Vol 1 (1) ◽  
pp. 2-15
Author(s):  
Olaf Hesebeck
Keyword(s):  
Tensile Test ◽  
Strain Rate ◽  
Finite Strain ◽  
Strain Curve ◽  
Model Parameters ◽  
Strain Rates ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Material Response ◽  
Rate Dependent

The combination of hyperelastic material models with viscoelasticity allows researchers to model the strain-rate-dependent large-strain response of elastomers. Model parameters can be identified using a uniaxial tensile test at a single strain rate and a relaxation test. They enable the prediction of the stress–strain behavior at different strain rates and other loadings like compression or shear. The Marlow model differs from most hyperelastic models by the concept not to use a small number of model parameters but a scalar function to define the mechanical properties. It can be defined conveniently by providing the stress–strain curve of a tensile test without need for parameter optimization. The uniaxial response of the model reproduces this curve exactly. The coupling of the Marlow model and viscoelasticity is an approach to create a strain-rate-dependent hyperelastic model which has good accuracy and is convenient to use. Unfortunately, in this combination, the Marlow model requires to specify the stress–strain curve for the instantaneous material response, while experimental data can be obtained only at finite strain rates. In this paper, a transformation of the finite strain rate data to the instantaneous material response is derived and numerically verified. Its implementation enables us to specify hyperelastic materials considering strain-rate dependence easily.

Applicability of Duncan-Chang Model and its Modified Versions to Methane Hydrate-Bearing Sands

2011 ◽  
Vol 347-353 ◽  
pp. 3384-3387 ◽  
Author(s):  
Ju Hua Xiong ◽  
Xiao Yong Kou ◽  
Fang Liu ◽  
Ming Jing Jiang
Keyword(s):  
Methane Hydrate ◽  
Constitutive Models ◽  
Constitutive Law ◽  
Triaxial Tests ◽  
Elastic Model ◽  
Clathrate Compound ◽  
Constitutive Response ◽  
Nonlinear Elastic ◽  
Hydrate Bearing Sediments ◽  
Chang Model

Methane hydrate is ice-like clathrate compound that attracts global attention due to its huge potential as a future energy source. The constitutive law of methane hydrate-bearing sediments remains unknown and becomes a barrier in sustainable exploitation of methane hydrate from marine sediments. The Duncan-Change model is a nonlinear elastic model which was widely accepted by the geotechnical community in approximating the constitutive response of geo-materials. This model and its evolved versions were employed in this study to model the stress-strain response observed in triaxial tests on methane hydrate-bearing sands. Duncan-Chang type models capture well the strain hardening behaviors. However, they fall short of incorporating the dependency of temperature and saturation degree of methane hydrate, which have to be taken into account in future constitutive models of methane hydrate-bearing deposits.

Strain Rate Dependence and Short-Term Relaxation Behavior of a Thermoset Polymer at Elevated Temperature: Experiment and Modeling

2008 ◽  
Author(s):  
A. J. W. McClung ◽  
M. B. Ruggles-Wrenn
Keyword(s):  
Strain Rate ◽  
Strain Curve ◽  
Strain Recovery ◽  
Relaxation Behavior ◽  
Solid Polymer ◽  
Experimental Program ◽  
Model Parameters ◽  
Stress Strain ◽  
Nonlinear Stress ◽  
Thermoset Polymer

The inelastic deformation behavior of PMR-15 neat resin, a high-temperature thermoset polymer, was investigated at 288°C. The experimental program was designed to explore the influence of strain rate changes in the 10−6 to 10−3 s−1 range on tensile loading, unloading, and strain recovery behavior, as well as on the relaxation response of the material. The material exhibits positive, nonlinear strain rate sensitivity in monotonic loading. Nonlinear, “curved” stress-strain behavior during unloading is observed at all strain rates. The strain recovery at zero stress is profoundly affected by prior strain rate. The prior strain rate is also found to have a strong influence on relaxation behavior. The rest stresses measured at the termination of relaxation tests form the relaxation boundary which resembles a nonlinear stress-strain curve. The results suggest that the inelastic behavior of the PMR-15 solid polymer at 288°C can be represented using a unified constitutive model with an overstress dependence of the inelastic rate of deformation. The experimental data are modeled with the viscoplasticity theory based on over-stress (VBO). A systematic procedure for determining model parameters is presented and the model is employed to predict the response of the material under various test histories.

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