A Reexamination of the Equations of Anisotropic Poroelasticity

2017 ◽  
Vol 84 (5) ◽  
Author(s):  
Yue Gao ◽  
Zhanli Liu ◽  
Zhuo Zhuang ◽  
Keh-Chih Hwang
Keyword(s):  
Constitutive Model ◽  
Laboratory Tests ◽  
Material Constant ◽  
Solid Skeleton ◽  
Material Constants ◽  
New Material ◽  
Solid Part ◽  
Four Levels

The anisotropic poroelastic constitutive model is reexamined in this article. The assumptions and conclusions of previous works, i.e., Thompson and Willis and Cheng, are compared and clarified. The micromechanics of poroelasticity is discussed by dividing the medium into connected fluid part and solid skeleton part. The latter includes, in turn, solid part and, possibly, disconnected fluid part, i.e., fluid islands; therefore, the solid skeleton part is inhomogeneous. The constitutive model is complicated both in the whole medium and in the solid skeleton because of their inhomogeneity, but the formulations are simplified successfully by introducing a new material constant which is defined differently by Cheng and by Thompson and Willis. All the unmeasurable micromechanical material constants are lumped together in this constant. Four levels of assumptions used in poroelasticity are demonstrated, and with the least assumptions, the constitutive model is formulated. The number of independent material constants is discussed, and the procedures in laboratory tests to obtain the constants are suggested.

Parametric Investigation of Mooney-Rivlin Material Constants on Silicone Biocomposite

2017 ◽  
Vol 882 ◽  
pp. 51-55 ◽  
Author(s):  
Siti Humairah Kamarul Bahrain ◽  
Jamaluddin Mahmud
Keyword(s):  
Mechanical Properties ◽  
Constitutive Model ◽  
Future Study ◽  
Mechanical Behaviour ◽  
Constitutive Models ◽  
Material Constant ◽  
High Tendency ◽  
Material Constants ◽  
Hyperelastic Materials ◽  
Linear Behaviour

Hyperelastic materials are unique materials that have high tendency to stretch and its highly non-linear behaviour is commonly investigated using hyperelastic constitutive models. The aim of this paper is to investigate the sensitivity of Mooney-Rivlin material constants; C1 and C2 values in order to observe the behavior and pattern of the stress-stretch graph for silicone-kenaf composite. There were no previous studies done in regards to assess the mechanical behaviour of the stress-stretch curve for silicone-kenaf biocomposite by varying the Mooney-Rivlin material constants. The material constant, C1 and C2 are varied into few cases and the patterns of stress-stretch curves are studied. It was found that variations of C1 and C2 material constants could contribute differently on the mechanical properties of silicone-kenaf composite. Thus, the results and findings of this study could be further enhanced by future study to gain deeper understanding on the hyperelastic materials behaviour and Mooney-Rivlin hyperelastic constitutive model.

scholarly journals Development of a Novel Hybrid Unified Viscoplastic Constitutive Model

2015 ◽  
Author(s):  
Luis A. Varela J. ◽  
Calvin M. Stewart
Keyword(s):  
Experimental Data ◽  
Stainless Steel ◽  
Hybrid Model ◽  
Material Constant ◽  
Inelastic Behavior ◽  
Hastelloy X ◽  
Material Constants ◽  
Stainless Steel 304 ◽  
Simulation Results ◽  
Optimal Material

Hastelloy X and stainless steel 304 are alloys widely used in industrial gas turbines components, petrochemical industry and energy generation applications; In the Pressure Vessel and Piping (PVP) industries they are used in nuclear and chemical reactors, pipes and valves applications. Hastelloy X and stainless steel 304 are favored for these types of applications where elevated temperatures are preferred for better systems’ efficiencies; they are favored due to its high strength and corrosion resistance at high temperature levels. A common characteristic of these alloys, is its rate-dependent mechanical behavior which difficult the prediction of the material response for design and simulation purposes. Therefore, a precise unified viscoplastic model capable to describe Hastelloy X and stainless steel 304 behaviors under a variety of loading conditions at high temperatures is needed to allow a better and less conservative design of components. Numerous classical unified viscoplastic models have been proposed in literature, to predict the inelastic behavior of metals under extreme environments. Based on Miller and Walker classical unified constitutive models a novel hybrid unified viscoplastic constitutive model is introduced in the present work, to describe the inelastic behavior caused by creep and fatigue effects at high temperature. The presented hybrid model consists of the combination of the best aspects of Miller and Walker model constitutive equations, with the addition of a damage rate equation which provides a description of the damage evolution and rupture prediction capabilities for Hastelloy X and stainless steel 304. A detailed explanation on the meaning of each material constant is provided, along with its impact on the hybrid model behavior. Material constants were calculated using the recently developed Material Constant Heuristic Optimizer (MACHO) software, to ensure the use of the optimal material constants values. This software uses the simulated annealing algorithm to determine the optimal material constants in a global surface, by comparing numerical simulations to an extensive database of experimental data. To validate the capabilities of the proposed hybrid model, numerical simulation results are compared to a broad range of experimental data at different stress levels and strain amplitudes; besides the consideration of two alloys in the present work, would demonstrate the model’s capabilities and flexibility to model multiple alloys behavior. Finally a quantitative analysis is provided to determine the percentage error and coefficient of determination between the experimental data and numerical simulation results to estimate the efficiency of the proposed hybrid model.

scholarly journals A Nonlinear Statistical Damage Constitutive Model for Porous Rocks

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Yue Pan ◽  
Zhiming Zhao ◽  
Liu He ◽  
Guang Wu
Keyword(s):  
Constitutive Model ◽  
Solid Skeleton ◽  
Porous Rocks ◽  
Different Types ◽  
Confining Pressures ◽  
Damage Constitutive Model ◽  
Statistical Damage Constitutive Model ◽  
Energy Theory ◽  
Water Contents ◽  
Statistical Damage

In the current paper, the deformation behaviours of rocks during compression are studied by testing 10 groups of sandstone samples with different porosity characteristics. According to the energy theory, the rock material was divided into two parts: solid skeleton and voids. A statistical damage-based approach was adopted to establish a nonlinear statistical damage constitutive model. The validity of the statistical damage constitutive model is verified by the test data. The statistical damage constitutive model performs well in each stage of rock compression before failure. For different types of rocks, different confining pressures, and different water contents, the statistical damage constitutive model fits well. This model can be applied to most types of rocks and in most engineering environments.

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.

Laboratory Properties Evaluation of Wearing Course Asphalt Mixtures Incorporating RAP Materials

2011 ◽  
Vol 305 ◽  
pp. 398-401
Author(s):  
Lan Yun Chen ◽  
Xin Qiu ◽  
Xin Kuan Wang ◽  
Qing Yang
Keyword(s):  
Natural Resources ◽  
Environmental Protection ◽  
Laboratory Tests ◽  
Asphalt Mixtures ◽  
Land Conservation ◽  
Material Consumption ◽  
Engineering Characteristics ◽  
New Material

Using RAP to reproduce new mixtures helps to reduce new material consumption, minimizes the exploitation of natural resources and brings vast benefit in land conservation and environmental protection. The main objectives of this study is to conduct laboratory tests on RAP mixtures with different RAP content, to comprehensively evaluate their engineering characteristics, then to recommend the best suitable RAP mixtures as the local paving materials.

An Efficient Method for the Optimization of Viscoplastic Constitutive Model Constants

2010 ◽  
Author(s):  
James P. DeMarco ◽  
Erik A. Hogan ◽  
Calvin M. Stewart ◽  
Ali P. Gordon
Keyword(s):  
Constitutive Model ◽  
Random Noise ◽  
Constitutive Models ◽  
Optimization Method ◽  
Complex Stress ◽  
Operating Conditions ◽  
Widespread Application ◽  
Material Constants ◽  
Material Parameters ◽  
Critical Components

Constitutive modeling has proven useful in providing accurate predictions of material response in components subjected to a variety of operating conditions; however, the high number of experiments necessary to determine appropriate constants for a model can be prohibitive, especially for more expensive materials. Generally, up to twenty experiments simulating a range of conditions are needed to identify the material parameters for a model. In this paper, an automated process for optimizing the material constants of the Miller constitutive model for uniaxial modeling is introduced. The use of more complex stress, strain, and temperature histories than are traditionally used allows for the effects of all material parameters to be captured using significantly fewer tests. A graphical user interface known as uSHARP was created to implement the resulting method, which determines the material constants of a viscoplastic model using a minimum amount of experimental data. By carrying out successive finite element simulations and comparing the results to simulated experimental test data, both with and without random noise, the material constants were determined from 75% fewer experiments. The optimization method introduced here reduces the cost and time necessary to determine constitutive model constants through experimentation. Thus it allows for a more widespread application of advanced constitutive models in industry and for better life prediction modeling of critical components in high-temperature applications.

Determination of Material Constants of Internal Time Theory of Plasticity and Creep for Fatigue Analysis and Creep-Fatigue Analysis

2011 ◽  
Author(s):  
Osamu Watanabe
Keyword(s):  
Finite Element ◽  
Constitutive Model ◽  
Fatigue Analysis ◽  
Computer Hardware ◽  
Computational Time ◽  
Inelastic Behavior ◽  
Material Constants ◽  
Creep Fatigue ◽  
Recent Computer

Recent computer hardware is greatly developed to make possible fatigue analysis and creep-fatigue analysis of structures, which takes much computational time in the past. The code and standard recommend the simplified method in the fatigue analysis and creep-fatigue analysis instead of the detailed inelastic finite element solutions. It is widely recognized that the employed constitutive model affects inelastic finite element solutions significantly. However, the inelastic finite element solutions can consider effects of geometry shape or boundary conditions easily compared to the simplified methods. The other advantage of the inelastic solutions can also assist the mechanism of inelastic deformations. Thus, the accurate inelastic finite element solution is still intense research subject in this area.. The present paper will study constitutive model and the determination method of the material constants for the fatigue analysis and creep-fatigue analysis in order to simulate inelastic behavior at saturated condition, which differs from those at the initial loading.

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

2018 ◽  
Vol 140 (9) ◽  
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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