Variational Viscoelastic-Damage Model for Fiber Reinforced Soft Tissues

2013 ◽  
Author(s):  
Eduardo A. Fancello ◽  
Jakson M. Vassoler
Keyword(s):  
Mechanical Behavior ◽  
Internal Structure ◽  
Soft Tissues ◽  
Damage Model ◽  
Potential Functions ◽  
Ground Substance ◽  
Mullins Effect ◽  
Numerical Examples ◽  
Proposed Model ◽  
Dissipative Material

Connective soft tissues have a pronounced anisotropic mechanical behavior due to their internal structure, consisting of a quasi isotropic ground substance and anisotropic reinforcement based mostly in elastin and collagen fibers. The objective of this paper is to extend previously proposed model for viscoelastic materials with fiber reinforcement making it capable to represent two important phenomena: the so-called Mullins effect and the softening at excessive strains. The model is based on a variational, thermodynamical consistent framework based on an incremental potential that allows for the representation of different dissipative material by simply changing the expression of potential functions and for the obtention of symmetric constitutive tangent matrices. Numerical examples show the capability of the proposed model to mimic with appreciable accuracy the experimentally observed mechanical behavior of soft tissues.

Damage Model for Dissipative Materials with Generalized Non-Linear Strength Theory

2011 ◽  
Vol 415-417 ◽  
pp. 1439-1442
Author(s):  
Wei Wei Yu ◽  
Xuan Guo
Keyword(s):  
Internal Structure ◽  
Damage Model ◽  
Structural Evolution ◽  
Strength Theory ◽  
Structural Configuration ◽  
Progressive Loss ◽  
Proposed Model ◽  
Non Linear ◽  
Predicting Behavior

This paper builds the formulations of damage model for dissipative materials with generalized non-linear strength theory. The proposed model reflects the internal structural configuration and damage behavioure. The structural evolution parameters are introduced to account for the progressive loss of the internal structure. The proposed damage model is proposed by generalized non-linear strength theory, the capability of the models in predicting behavior of clay has been examined.

A Model for the Mullins Effect in Multinetwork Elastomers

2017 ◽  
Vol 84 (12) ◽  
Author(s):  
Mattia Bacca ◽  
Costantino Creton ◽  
Robert M. McMeeking
Keyword(s):  
Damage Model ◽  
Hydrostatic Compression ◽  
Cross Linking ◽  
Mullins Effect ◽  
Maximum Strain ◽  
Double Network ◽  
Proposed Model ◽  
Damage Process ◽  
Composite Stiffness ◽  
Highly Loaded

Double and triple network (TN) elastomers can be made by infusing monomers into a single network (SN) polymer, causing it to swell, and then polymerizing and cross-linking the monomers. The result is a double network (DN) elastomer in which one network is stretched and the other is in hydrostatic compression. TN systems are made by repeating the process starting with the DN material. The multinetwork (MN) elastomers exhibit a Mullins effect in which softening occurs upon a first cycle of loading, with the elastomer stiffness recovered above the previous maximum strain. The Mullins effect is attributed to rupture of the stretched network, eliminating the constraint on the compressed network, thereby motivating straining at the lower stiffness of the remaining material. A model for this process is developed, based on the previous work of Horgan et al. (2004, “A Theory of Stress Softening of Elastomers Based on Finite Chain Extensibility,” Proc. R. Soc. A, 460(2046), pp. 1737–1754). In the proposed model, a composite stiffness for the MN system is developed and a damage process introduced to degrade the contribution of the stretched network. The damage model is designed to account for the progressive elimination of chains that are most highly loaded in the stretched network, so that the undamaged stiffness is restored when the strain rises above levels previously experienced. The proposed model reproduces the behavior of the Mullins effect in the MN system.

Why is it necessary to use a damage model to simulate the mechanical behavior of concrete under drying and leaching?

2010 ◽  
Vol 14 (6-7) ◽  
pp. 923-935
Author(s):  
Thomas Rougelot ◽  
Cheng Peng ◽  
Nicolas Burlion ◽  
Dominique Bernard
Keyword(s):  
Mechanical Behavior ◽  
Damage Model

The Generation Principle and Mathematical Models of Double-Enveloping Internal Gear Pairs

2015 ◽  
Author(s):  
Xuan Li ◽  
Bingkui Chen ◽  
Yawen Wang ◽  
Guohua Sun ◽  
Teik C. Lim
Keyword(s):  
Mathematical Model ◽  
Load Capacity ◽  
Geometrical Shape ◽  
Gear Pair ◽  
Numerical Examples ◽  
Proposed Model ◽  
General Mathematical Model ◽  
Meshing Characteristics ◽  
Internal Gear ◽  
Tooth Pair

In this paper, the planar double-enveloping method is presented for the generation of tooth profiles of the internal gear pair for various applications, such as gerotors and gear reducers. The main characteristic of this method is the existence of double contact between one tooth pair such that the sealing property, the load capacity and the transmission precision can be significantly improved as compared to the conventional configuration by the single-enveloping theory. Firstly, the generation principle of the planar double-enveloping method is introduced. Based on the coordinate transformation and the envelope theory, the general mathematical model of the double-enveloping internal gear pair is presented. By using this model, users can directly design different geometrical shape profiles to obtain a double-enveloping internal gear pair with better meshing characteristics. Secondly, to validate the effectiveness of the proposed model, specific mathematical formulations of three double-enveloping internal gear pairs which apply circular, parabolic and elliptical curves as the generating curves are given. The equations of tooth profiles and meshing are derived and the composition of tooth profiles is analyzed. Finally, numerical examples are provided for an illustration.

Dynamics of a Two-DOF Parallel Pointing Mechanism

2005 ◽  
Author(s):  
Alessandro Cammarata ◽  
Rosario Sinatra
Keyword(s):  
Numerical Simulation ◽  
Parallel Mechanism ◽  
Inverse Dynamics ◽  
Kinematic Model ◽  
Degree Of Freedom ◽  
Numerical Examples ◽  
Proposed Model ◽  
Dynamic Analyses ◽  
Moving Platform ◽  
Two Degree Of Freedom

This paper presents kinematic and dynamic analyses of a two-degree-of-freedom pointing parallel mechanism. The mechanism consists of a moving platform, connected to a fixed platform by two legs of type PUS (prismatic-universal-spherical). At first a simplified kinematic model of the pointing mechanism is introduced. Based on this proposed model, the dynamics equations of the system using the Natural Orthogonal Complement method are developed. Numerical examples of the inverse dynamics results are presented by numerical simulation.

Representation of Mechanical Behavior in the Presence of Changing Internal Structure

1988 ◽  
Vol 55 (1) ◽  
pp. 1-10 ◽  
Author(s):  
E. T. Onat ◽  
F. A. Leckie
Keyword(s):  
Mechanical Behavior ◽  
Internal Structure ◽  
Applied Stress ◽  
Constitutive Equations ◽  
Creep Damage ◽  
Main Ideas ◽  
The Relationship ◽  
Small Deformations

The paper is concerned with the representation of the relationship that exists, for a given material and temperature and for small deformations, between histories of applied stress and the observed strain and the accompanying changes in internal structure of the material. Emphasis is given to creep damage in metals as a vehicle for illustration of the main ideas introduced in the paper. In particular, the role played by irreducible even rank tensors in the representation of internal structure is discussed and clarified. The restrictions placed by thermodynamics on constitutive equations are considered and the use of potentials in these equations is examined and criticized.

scholarly journals Improved numerical model for fatigue cumulative damage of mechanical structure considering load sequence and interaction

2021 ◽  
Vol 13 (2) ◽  
pp. 168781402199530
Author(s):  
Bixiong Huang ◽  
Shuci Wang ◽  
Shuanglong Geng ◽  
Xintian Liu
Keyword(s):  
Fatigue Life ◽  
Theoretical Basis ◽  
Life Prediction ◽  
Damage Model ◽  
Cumulative Damage ◽  
Load Spectrum ◽  
Random Load ◽  
Mechanical Parts ◽  
Proposed Model ◽  
Load Sequence

To more accurately predict the fatigue life of components under the action of random loads, it is necessary to explore the influence of the interaction between the load sequence and the load on the life prediction. Based on the Manson-Halford method and Corten-Dolan model, this paper establishes a fatigue cumulative damage model that takes into account both the load order and the interaction between loads, and also takes into account the loads near the fatigue limit. The fatigue life of mechanical parts under random load can be calculated through this model, which provides a theoretical basis for life prediction under random load spectrum. The fatigue life of mechanical parts under random load can be calculated through this model, which provides a theoretical basis for life prediction under random load spectrum. Comparing the calculation results of the proposed model with the results of Palmgren Miner, Manson-Halford method, and Corten-Dolan model, it is found that the fatigue damage model established can reasonably predict the fatigue life of parts. Comparison and verification of examples further prove the accuracy and reliability of the proposed model.

scholarly journals Structure investigations of layered soil – varved clay

2016 ◽  
Vol 48 (4) ◽  
pp. 365-375 ◽  
Author(s):  
Matylda Tankiewicz
Keyword(s):  
Mechanical Behavior ◽  
Internal Structure ◽  
Strength Properties ◽  
Layered Soil ◽  
Radiographic Images ◽  
Composition And Structure ◽  
Computed Microtomography ◽  
Structure Investigations ◽  
Varved Clay

Abstract In the paper the results of laboratory investigations of structure of layered soil are presented. They focus on varved clay that is a soil composed of two alternately arranged varves with different texture and mechanical properties. An effect of such structure is an anisotropy of the material. Due to varying conditions during its formation process the soil exhibits some irregularities in composition and structure. Due to that modelling of mechanical behavior, like strength, may not provide satisfactory results. Main purpose of the examinations is an investigation of internal structure of layered soil – varved clay – in relation to its strength anisotropy and evaluation of the suitability of the use of two different techniques to assess the soil structure. Investigated material have been taken from area near city of Bełchatów in central Poland. The examinations included investigation of particle size distribution of soil and its components, identification of lamination with use of scanning electron microscope (SEM) and computed microtomography technique (μCT). First, the texture of each varve and varved clay as a composite have been estimated. Next, the investigation of surface perpendicular to the lamination have been carried out with SEM. Pictures of varves with different magnifications are presented. Also the varves arrangement and details of layers contact area are shown. Finally, investigation of internal structure of the soil have been performed by using microtomograph. The outcome is a series of radiographic images and reconstructed 3D model of tested soil. Presented results show complexity of the structure of varved clay that affect the mechanical behavior. Determination of the structure with use of presented techniques may be helpful in examination of strength properties and proper modeling of such soil.

scholarly journals A bi-dissipative damage model for concrete

2015 ◽  
Vol 8 (1) ◽  
pp. 49-65
Author(s):  
J. J. C. Pituba ◽  
W. M. Pereira Júnior
Keyword(s):  
Reinforced Concrete ◽  
Structural Engineering ◽  
Damage Mechanics ◽  
Damage Model ◽  
Continuum Damage Mechanics ◽  
Concrete Material ◽  
Framed Structures ◽  
Energy Equivalence ◽  
Proposed Model ◽  
Damage Processes

This work deals with an improvement of an anisotropic damage model in order to analyze reinforced concrete structures submitted to reversal loading. The original constitutive model is based on the fundamental hypothesis of energy equivalence between real and continuous media following the concepts of the Continuum Damage Mechanics. The concrete is assumed as an initial elastic isotropic medium presenting anisotropy, permanent strains and bimodularity induced by damage evolution. In order to take into account the bimodularity, two damage tensors governing the rigidity in tension or compression regimes are introduced. However, the original model is not capable to simulate the influence of the previous damage processes in compression regimes. In order to avoid this problem, some conditions are introduced to simulate the damage unilateral effect. It has noted that the damage model is agreement with to micromechanical theory conditions when dealing to unilateral effect in concrete material. Finally, the proposed model is applied in the analyses of reinforced concrete framed structures submitted to reversal loading. These numerical applications show the good performance of the model and its potentialities to simulate practical problems in structural engineering.

scholarly journals Extreme Value Analysis for Mixture Models with Heavy-Tailed Impurity

Mathematics ◽  
2021 ◽  
Vol 9 (18) ◽  
pp. 2208
Author(s):  
Ekaterina Morozova ◽  
Vladimir Panov
Keyword(s):  
Stock Returns ◽  
Mixture Models ◽  
Extreme Value ◽  
Extreme Value Analysis ◽  
Value Analysis ◽  
Numerical Examples ◽  
Proposed Model ◽  
Mixing Parameter ◽  
Heavy Tailed ◽  
Regularly Varying Distribution

This paper deals with the extreme value analysis for the triangular arrays which appear when some parameters of the mixture model vary as the number of observations grows. When the mixing parameter is small, it is natural to associate one of the components with “an impurity” (in the case of regularly varying distribution, “heavy-tailed impurity”), which “pollutes” another component. We show that the set of possible limit distributions is much more diverse than in the classical Fisher–Tippett–Gnedenko theorem, and provide the numerical examples showing the efficiency of the proposed model for studying the maximal values of the stock returns.

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