The Constitutive Model for Isotropic Damage of Geomaterial

2007 ◽  
Vol 348-349 ◽  
pp. 513-516
Author(s):  
Yuan Xue Liu ◽  
Jian Ting Zhou ◽  
Zhong You Li
Keyword(s):  
Constitutive Model ◽  
Numerical Computation ◽  
Stress And Strain ◽  
Stress Strain ◽  
Computation Procedure ◽  
Strain Behavior ◽  
Reconstituted Soil ◽  
Isotropic Damage

A constitutive model for isotropic damage of geomaterial is put forward, and its numerical computation procedure is given also. The calculated results for a simple example could highlight our understanding about the mechanism of geomaterial damage, and several useful conclusions can be drawn: The series assumption can not be used to synthesis mode of stress and strain for complexus theory of geomaterials damage; strictly speaking, the parallel assumption can not be used to that of geomaterials damage also; the complexus stress-strain behavior like that of ideal natural geomaterial under small stress, and like that of reconstituted soil under large stress.

A Cyclic Stress-Strain Constitutive Model for Polycrystalline Magnesium Alloy and its Application

2007 ◽  
Vol 546-549 ◽  
pp. 81-88
Author(s):  
Xiang Guo Zeng ◽  
Qing Yuan Wang ◽  
Jing Hong Fan ◽  
Zhan Hua Gao ◽  
Xiang He Peng
Keyword(s):  
Magnesium Alloy ◽  
Constitutive Model ◽  
Cyclic Stress ◽  
Stress And Strain ◽  
Slip Systems ◽  
Stress Strain ◽  
Strain Behavior ◽  
Cast Magnesium ◽  
Magnesium Alloy Am60 ◽  
Good Agreement

The stress-strain behavior of cast magnesium alloy (AM60) was investigated by strain-controlled cyclic testing carried out on MTS. In order to describe the cyclic stress and strain properties of AM60 by means of the energy storing characteristics of microstructure during irreversible deformation, a plastic constitutive model with no yielding surface was developed for single crystal by adopting a spring-dashpot mechanical system. Plastic dashpots reflecting the material transient response were introduced to describe the plasticity of slip systems. By utilizing the KBW self-consistent theory, a polycrystalline plastic constitutive model for Magnesium alloy was formed. The numerical analysis in the corresponding algorithm is greatly simplified as no process of searching for the activation of the slip systems and slip directions is required. The cyclic stress-strain behavior, based on this model, is discussed. The simulation results show good agreement with the experimental data for AM60.

scholarly journals Uniform Nonlinear Constitutive Model and Parameters for Clay in Different Consolidation Conditions Based on Regression Method

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Tao Cheng ◽  
Keqin Yan ◽  
Huazhi Zhang ◽  
Xianfeng Luo ◽  
Shengfang Li
Keyword(s):  
Constitutive Model ◽  
Initial Conditions ◽  
Constitutive Relations ◽  
Test Sample ◽  
Maximum Relative Error ◽  
Compression Tests ◽  
Stress Strain ◽  
Strain Behavior ◽  
Nonlinear Constitutive Model ◽  
Isotropic Consolidation

The nonlinear constitutive relations of clay are investigated considering different initial conditions. Highly compressible clay is selected as the test sample. Two groups of tri-axial compression tests are performed, respectively, afterK0consolidation and isotropic consolidation. On the basis of the framework ofE~vmodel, a uniform nonlinear constitutive model is proposed by fitting the test data. With the average slope of the unloading-reloading curve selected as the unloading modulus, the unloading function is constructed as the loading-unloading criterion. Moreover, a comparison between the experimental stress-strain curves and the results predicted by the constitutive model is made. It is shown that the prediction is reasonable, which can reflect the stress-strain behavior of the soil under theK0consolidation and isotropic consolidation conditions. The maximum relative error of the two series of curves is not remarkable, less than 6%.

Protein Forced Unfolding and Its Effects on the Finite Deformation Stress-Strain Behavior of Biomacromolecular Solids

2005 ◽  
Vol 874 ◽  
Author(s):  
H. Jerry Qi ◽  
Christine Ortiz ◽  
Mary C. Boyce
Keyword(s):  
Constitutive Model ◽  
Single Molecule ◽  
Biological Networks ◽  
Finite Deformation ◽  
State Theory ◽  
Force Extension ◽  
Stress Strain ◽  
Strain Behavior ◽  
Mechanics Model ◽  
Deformation Stress

AbstractMany proteins have been experimentally observed to exhibit a force-extension behavior with a characteristic repeating pattern of a nonlinear rise in force with imposed displacement to a peak, followed by a significant force drop upon reaching the peak (a “saw-tooth” profile) due to successive unfolding of modules during extension. This behavior is speculated to play a governing role in biological and mechanical functions of natural materials and biological networks composed of assemblies of such protein molecules. In this paper, a constitutive model for the finite deformation stress-strain behavior of crosslinked networks of modular macromolecules is developed. The force-extension behavior of the individual modular macromolecule is represented using the Freely Jointed Chain (FJC) statistical mechanics model together with a two-state theory to capture unfolding. The single molecule behavior is then incorporated into a formal continuum mechanics framework to construct a constitutive model. Simulations illustrate a relatively smooth “yield”-like stress-strain behavior of these materials due to activate unfolding in these microstructures.

scholarly journals Stress-Strain Behavior of Perfluorosulfonic Acid Membranes at Various Temperatures and Humidities: Experiments and Phenomenological Modeling

2008 ◽  
Vol 6 (1) ◽  
Author(s):  
Ahmet Kusoglu ◽  
Yaliang Tang ◽  
Michael H. Santare ◽  
Anette M. Karlsson ◽  
Simon Cleghorn ◽  
...  
Keyword(s):  
Constitutive Model ◽  
Flow Behavior ◽  
True Strain ◽  
Plastic Behavior ◽  
Stress Strain ◽  
True Strain Rate ◽  
Material Constants ◽  
Strain Behavior ◽  
Constitutive Response ◽  
Perfluorinated Sulfonic Acid

The constitutive response of perfluorinated sulfonic acid (PFSA) membranes based on tensile testing is investigated, and a phenomenological constitutive model for the elastoplastic flow behavior as a function of temperature and humidity is proposed. To this end, the G’Sell–Jonas (1979, “Determination of the Plastic Behavior of Solid Polymers at Constant True Strain Rate,” J. Mater. Sci., 14, pp. 583–591) constitutive model for semicrystalline polymers is extended by incorporating, in addition to temperature, relationships between the material constants of this model and the measured relative humidity. By matching the proposed constitutive model to the experimental stress-strain data, useful material constants are found. Furthermore, correlations between these material constants and Young’s modulus and proportional limit stress are investigated. The influence of material orientation, inherited from processing conditions, on the stress-strain behavior is also studied. The proposed model can be used to approximate the mechanical behavior of PFSA membranes in numerical simulations of a fuel cell operation.

Development of a Flow Evolution Network Model for the Stress–Strain Behavior of Poly(L-lactide)

2017 ◽  
Vol 139 (9) ◽  
Author(s):  
Maureen L. Dreher ◽  
Srinidhi Nagaraja ◽  
Jorgen Bergstrom ◽  
Danika Hayman
Keyword(s):  
Finite Element ◽  
Constitutive Model ◽  
Computational Modeling ◽  
Medical Devices ◽  
Constitutive Models ◽  
Constitutive Relationship ◽  
Displacement Curve ◽  
Stress Strain ◽  
Strain Behavior ◽  
Flow Evolution

Computational modeling is critical to medical device development and has grown in its utility for predicting device performance. Additionally, there is an increasing trend to use absorbable polymers for the manufacturing of medical devices. However, computational modeling of absorbable devices is hampered by a lack of appropriate constitutive models that capture their viscoelasticity and postyield behavior. The objective of this study was to develop a constitutive model that incorporated viscoplasticity for a common medical absorbable polymer. Microtensile bars of poly(L-lactide) (PLLA) were studied experimentally to evaluate their monotonic, cyclic, unloading, and relaxation behavior as well as rate dependencies under physiological conditions. The data were then fit to a viscoplastic flow evolution network (FEN) constitutive model. PLLA exhibited rate-dependent stress–strain behavior with significant postyield softening and stress relaxation. The FEN model was able to capture these relevant mechanical behaviors well with high accuracy. In addition, the suitability of the FEN model for predicting the stress–strain behavior of PLLA medical devices was investigated using finite element (FE) simulations of nonstandard geometries. The nonstandard geometries chosen were representative of generic PLLA cardiovascular stent subunits. These finite element simulations demonstrated that modeling PLLA using the FEN constitutive relationship accurately reproduced the specimen’s force–displacement curve, and therefore, is a suitable relationship to use when simulating stress distribution in PLLA medical devices. This study demonstrates the utility of an advanced constitutive model that incorporates viscoplasticity for simulating PLLA mechanical behavior.

Analyses of stress strain behavior and constitutive model of artificial methane hydrate

2011 ◽  
Vol 77 (2) ◽  
pp. 183-188 ◽  
Author(s):  
Feng Yu ◽  
Yongchen Song ◽  
Weiguo Liu ◽  
Yanghui Li ◽  
Weihaur Lam
Keyword(s):  
Constitutive Model ◽  
Methane Hydrate ◽  
Stress Strain ◽  
Strain Behavior

A Comparison of Tensile Stress-Strain Data from Dumbbell, Ring, and Oval Specimens

1974 ◽  
Vol 47 (5) ◽  
pp. 1213-1233 ◽  
Author(s):  
F. S. Myers ◽  
J. D. Wenrick
Keyword(s):  
Tensile Modulus ◽  
Thermoplastic Elastomers ◽  
Cyclic Softening ◽  
Stress And Strain ◽  
Stress Strain ◽  
Test Configuration ◽  
Uniaxial Test ◽  
Strain Behavior ◽  
Strain Data ◽  
Low Modulus

Abstract Our study has shown that the tensile bar or dumbbell gives higher values for failure stress and strain than does either the ring or oval specimen. This should be expected since the tensile bar permits a primarily uniaxial test and one without the stress-concentrating pins used for the ring and oval. However, it is very difficult to obtain accurate low-strain data with the tensile bar. Also, the strain rate is not constant because of tab deformation. The ring, oval, and tensile bar show agreement for values of stress and strain above 100 per cent strain but below failure. For soft, low modulus stocks the ring and oval agree at low strains. For stock with tensile modulus values above 1000 psi, the bending stress and strain, required to straighten the ring to its in-test configuration, significantly affect the data. There is less ambiguity in reducing the data from tests run with the oval than from those run with the ring, whether reduction is done manually or through direct acquisition by computer. This is again because of the initial straightening of the ring. For both the ring and oval, the material in contact with the pin experiences non-uniaxial deformation and becomes the site of failure. Yielding, as defined in this paper, can be related to hysteresis effects and hence to the phenomenon known as cyclic softening. The stress at 300 per cent strain and the stress and strain at failure are not sufficient to characterize stress-strain behavior, particularly for thermoplastic elastomers.

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