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

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.

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The Constitutive Model for High Temperature Flow Behavior of SiC/6168Al Composite

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1089.37 ◽

2015 ◽

Vol 1089 ◽

pp. 37-41

Author(s):

Jiang Wang ◽

Sheng Li Guo ◽

Sheng Pu Liu ◽

Cheng Liu ◽

Qi Fei Zheng

Keyword(s):

Constitutive Model ◽

Hot Deformation ◽

Flow Behavior ◽

Type Equation ◽

Strain Rate Range ◽

Compression Tests ◽

Stress Strain ◽

Hollomon Parameter ◽

Proposed Model ◽

Relationship Of

The hot deformation behavior of SiC/6168Al composite was studied by means of hot compression tests in the temperature range of 300-450 °C and strain rate range of 0.01-10 s-1. The constitutive model was developed to predict the stress-strain curves of this composite during hot deformation. This model was established by considering the effect of the strain on material constants calculated by using the Zenter-Hollomon parameter in the hyperbolic Arrhenius-type equation. It was found that the relationship of n, α, Q, lnA and ε could be expressed by a five-order polynomial. The stress-strain curves obtained by this model showed a good agreement with experimental results. The proposed model can accurately describe the hot flow behavior of SiC/6168Al composite, and can be used to numerically analyze the hot forming processes.

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A Mathematical Description for the Stress-Strain Behavior of Annealed 2 1/4 Cr-1 Mo Steel

Journal of Pressure Vessel Technology ◽

10.1115/1.3454348 ◽

1976 ◽

Vol 98 (2) ◽

pp. 118-125 ◽

Cited By ~ 2

Author(s):

R. L. Klueh ◽

T. L. Hebble

Keyword(s):

Mathematical Description ◽

Flow Behavior ◽

True Strain ◽

Empirical Relationship ◽

Tensile Tests ◽

Strain Rates ◽

Strain Behavior ◽

Test Conditions ◽

Wide Range ◽

Strain Data

We have conducted a detailed series of tensile tests on one heat of annealed 2 1/4 Cr-1 Mo steel over the range 25 to 593°C (75 to 1100°F) and at nominal strain rates of 0.4, 0.04, 0.004, and 0.0004/min. To determine an empirical relationship to represent the flow behavior, we fitted the true-stress true-strain data from these tests to several proposed models. The models fit were those proposed by Hollomon, Ludwik, Ludwigson, and Voce. From a comparison of the standard error of estimate, the Voce equation was concluded to be the best mathematical description of the data under most test conditions and the best single representation over the wide range of test conditions.

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

Mathematical Problems in Engineering ◽

10.1155/2014/804586 ◽

2014 ◽

Vol 2014 ◽

pp. 1-8 ◽

Cited By ~ 1

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%.

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

MRS Proceedings ◽

10.1557/proc-874-l4.3 ◽

2005 ◽

Vol 874 ◽

Cited By ~ 3

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.

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An experimental study on stress-strain behavior and constitutive model of hardfill material

Science China Physics Mechanics and Astronomy ◽

10.1007/s11433-011-4518-3 ◽

2011 ◽

Vol 54 (11) ◽

pp. 2015-2024 ◽

Cited By ~ 8

Author(s):

MengXi Wu ◽

Bin Du ◽

YuanCheng Yao ◽

XianFeng He

Keyword(s):

Experimental Study ◽

Constitutive Model ◽

Stress Strain ◽

Strain Behavior

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

Journal of Biomechanical Engineering ◽

10.1115/1.4037071 ◽

2017 ◽

Vol 139 (9) ◽

Cited By ~ 4

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.

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

Materials Science Forum ◽

10.4028/www.scientific.net/msf.546-549.81 ◽

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.

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408 On Some Peculiar Stress-Strain Behavior of an Engineering Plastic, Polyphenylene-ether PPE and Numerical Reproduction of Such Phenomena Using the Viscoplastic Constitutive Model Based Overstress VBO

The Proceedings of Conference of Kyushu Branch ◽

10.1299/jsmekyushu.2010.63.135 ◽

2010 ◽

Vol 2010.63 (0) ◽

pp. 135-136

Author(s):

Takashi MINOKAWA ◽

Tetsuyuki HIROE ◽

Kazuhito FUJIWARA ◽

Hidehiro HATA ◽

Akira YAMASHITA ◽

...

Keyword(s):

Constitutive Model ◽

Stress Strain ◽

Strain Behavior ◽

Model Based ◽

Engineering Plastic

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Quantification of Material Constants for a Phenomenological Constitutive Model of Porcine Tricuspid Valve Leaflets for Simulation Applications

Journal of Biomechanical Engineering ◽

10.1115/1.4040126 ◽

2018 ◽

Vol 140 (9) ◽

Cited By ~ 7

Author(s):

Keyvan Amini Khoiy ◽

Anup D. Pant ◽

Rouzbeh Amini

Keyword(s):

Constitutive Model ◽

Tricuspid Valve ◽

Computational Models ◽

Biaxial Stress ◽

Stress Strain ◽

Mean Values ◽

Material Constants ◽

Model Average ◽

Anisotropy Index ◽

Index Value

The tricuspid valve is a one-way valve on the pulmonary side of the heart, which prevents backflow of blood during ventricular contractions. Development of computational models of the tricuspid valve is important both in understanding the normal valvular function and in the development/improvement of surgical procedures and medical devices. A key step in the development of such models is quantification of the mechanical properties of the tricuspid valve leaflets. In this study, after examining previously measured five-loading-protocol biaxial stress–strain response of porcine tricuspid valves, a phenomenological constitutive framework was chosen to represent this response. The material constants were quantified for all three leaflets, which were shown to be highly anisotropic with average anisotropy indices of less than 0.5 (an anisotropy index value of 1 indicates a perfectly isotropic response, whereas a smaller value of the anisotropy index indicates an anisotropic response). To obtain mean values of material constants, stress–strain responses of the leaflet samples were averaged and then fitted to the constitutive model (average R2 over 0.9). Since the sample thicknesses were not hugely different, averaging the data using the same tension levels and stress levels produced similar average material constants for each leaflet.

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