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Author: Zhengwei Qu Publisher: ISBN: Category : Languages : en Pages : 300
Book Description
La connaissance du comportement des matériaux élastomères est un enjeu important pour la conception de composants ou de structures mécaniques. Que ce soit sous chargement monotone ou cyclique, uniaxial ou multiaxial, ces propriétés doivent être maîtrisées afin de construire des outils prédictifs de durée de vie robustes Dans la revue bibliographique, après une présentation des propriétés physico-chimiques des matériaux élastomères, les modèles pour décrire leur comportement monotone sont discutés. Sont également présentées, les mécanismes d'endommagement (effet Mullins, adoucissement cyclique) ainsi que les aspects liés à 1 a fatigue et à la rupture de ces matériaux. Dans une deuxième partie, qui concerne les chargements cycliques, on s'intéresse tout d'abord à l'endommagement de type Mullms. Des expénences réalisées sur un élastomére de type SBR, mettent en évidence ce mécanisme d'endommagement. Se basant sur les travaux de Miehe. la prédiction par ce type de modéle conduit à un accord acceptable avec les données expérimentales. On s'intéresse ensuite à la prédiction de la durée de vie en fatigue en utilisant la définition de l'endommagement de Lemaltre. Sur la base d'une densité d'énergie d'Ogden d'ordre 4, on généralise un modéle développé par Wang permettant de calculer la durée de vie d'un élastomère. Ce modèle simple à deux paramètres permet de rendre à priori compte des évolutions observées expérimentalement en chargement uniaxial.On montre également les limites d'un tel modéle pour des chargements multiaxiaux. Dans la troisième partie, il s'agit de développer un outil prédictif de rupture des élastoméres sous chargement monotone et multiaxial Se basant sur le concept de défaut intrinsèque, et s'appuyant sur la mécanique de la rupture, on construit, par des simulations éléments finis en chargement biaxial, une courbe d'état limite dans le plan des élongations principales, dans le cas des contraintes planes. Les valeurs ainsi prédites sont en accord satisfaisant avec des données expérimentales pour deux matériaux différents (NR et SBR). Enfin, on tente de généraliser cette approche pour des cas où la pression hydrostatique est prépondérante, c'est-à-dire où la cavitation est le principal mécanisme de dégradation.
Author: Zhengwei Qu Publisher: ISBN: Category : Languages : en Pages : 300
Book Description
La connaissance du comportement des matériaux élastomères est un enjeu important pour la conception de composants ou de structures mécaniques. Que ce soit sous chargement monotone ou cyclique, uniaxial ou multiaxial, ces propriétés doivent être maîtrisées afin de construire des outils prédictifs de durée de vie robustes Dans la revue bibliographique, après une présentation des propriétés physico-chimiques des matériaux élastomères, les modèles pour décrire leur comportement monotone sont discutés. Sont également présentées, les mécanismes d'endommagement (effet Mullins, adoucissement cyclique) ainsi que les aspects liés à 1 a fatigue et à la rupture de ces matériaux. Dans une deuxième partie, qui concerne les chargements cycliques, on s'intéresse tout d'abord à l'endommagement de type Mullms. Des expénences réalisées sur un élastomére de type SBR, mettent en évidence ce mécanisme d'endommagement. Se basant sur les travaux de Miehe. la prédiction par ce type de modéle conduit à un accord acceptable avec les données expérimentales. On s'intéresse ensuite à la prédiction de la durée de vie en fatigue en utilisant la définition de l'endommagement de Lemaltre. Sur la base d'une densité d'énergie d'Ogden d'ordre 4, on généralise un modéle développé par Wang permettant de calculer la durée de vie d'un élastomère. Ce modèle simple à deux paramètres permet de rendre à priori compte des évolutions observées expérimentalement en chargement uniaxial.On montre également les limites d'un tel modéle pour des chargements multiaxiaux. Dans la troisième partie, il s'agit de développer un outil prédictif de rupture des élastoméres sous chargement monotone et multiaxial Se basant sur le concept de défaut intrinsèque, et s'appuyant sur la mécanique de la rupture, on construit, par des simulations éléments finis en chargement biaxial, une courbe d'état limite dans le plan des élongations principales, dans le cas des contraintes planes. Les valeurs ainsi prédites sont en accord satisfaisant avec des données expérimentales pour deux matériaux différents (NR et SBR). Enfin, on tente de généraliser cette approche pour des cas où la pression hydrostatique est prépondérante, c'est-à-dire où la cavitation est le principal mécanisme de dégradation.
Author: Gert Heinrich Publisher: Springer Nature ISBN: 3030689204 Category : Technology & Engineering Languages : en Pages : 491
Book Description
The book summarizes recent international research and experimental developments regarding fatigue crack growth investigations of rubber materials. It shows the progress in fundamental as well as advanced research of fracture investigation of rubber material under fatigue loading conditions, especially from the experimental point of view. However, some chapters will describe the progress in numerical modeling and physical description of fracture mechanics and cavitation phenomena in rubbers. Initiation and propagation of cracks in rubber materials are dominant phenomena which determine the lifetime of these soft rubber materials and, as a consequence, the lifetime of the corresponding final rubber parts in various fields of application. Recently, these phenomena became of great scientific interest due to the development of new experimental methods, concepts and models. Furthermore, crack phenomena have an extraordinary impact on rubber wear and abrasion of automotive tires; and understanding of crack initiation and growth in rubbers will help to support the growthing number of activities and worldwide efforts of reduction of tire wear losses and abrasion based emissions.
Author: Jean Lemaitre Publisher: Springer Science & Business Media ISBN: 3662027615 Category : Science Languages : en Pages : 225
Book Description
A new branch of science usually develops thus. Somebody publishes the basic ideas. Hesitatingly at first, then little by little, other original contributions appear, until a certain threshold is reached. Then, overview articles are printed, conferences are held, and a first mention is made in textbooks, until specialized monographs are written. Continuum darnage mechanics has reached that status now. To analyze or, if possible, to predict the failure of machine parts or other structures is one of the main goals of engineering science. Consequently fracture mechanics became one of its leading branches. It was based on the analysis of existing cracks. However, especially under conditions of cyclic loading, this might be too late to prevent a disaster. Therefore, the question regarding the precursory state, that is, the evolution of intemal darnage before macrocracks become visible, was then posed. One of the successful approaches to the problern was Weibull's theory which examined, in a statistical manner, the "weakest link" in the material volume under consideration. Unfortunately it proved too difficult mathematically to be applied to complicated parts or structures. Therefore it was highly appreciated by the scientific of material community when L. M. Kachanov published in 1958 a simple model darnage which subsequently could be extended to brittle elastic, plastic or viscous materials under all conditions of uniaxial or multiaxial, simple or cyclic loadings, so that it may be considered nearly universal.
Author: C. Bathias Publisher: ISBN: Category : Environment Languages : en Pages : 9
Book Description
Fatigue crack growth in natural rubber is studied using fracture mechanics concepts and an extension of Griffith's criterion. The effects of load ratio, temperature, and environment are examined. It appears that, for cycles without compression, a mean stress in tension improves the fatigue behavior by inducing crystallization, whereas a minimum stress in compression greatly damages the material. Tests under inert atmosphere show that, in addition to the mechanical damage, an important chemical damage due to oxygen is present. The fatigue cracking of natural rubber is also approached studying the influence of damage mechanisms in relation to microstructural aspects. In this way, SEM observations of fracture surfaces show a marked dependence on crack growth rate, load ratio, temperature, and environment. For high growth rates, we observe some fatigue striations, and we notice a microscopic mechanism for formation of tongue structure, which is highly dependent on gaseous oxygen and typical of natural rubbers.
Author: Wolfgang Grellmann Publisher: Springer ISBN: 9783642379116 Category : Technology & Engineering Languages : en Pages : 303
Book Description
Elastomers are found in many applications ranging from technology to daily life applications for example in tires, drive systems, sealings and print rollers. Dynamical operation conditions put extremely high demands on the performance and stability of these materials and their elastic and flow properties can be easily adjusted by simple manipulations on their elastic and viscous properties. However, the required service life suffers often from material damage as a result of wear processes such as abrasion and wear fatigue, mostly caused by crack formation and propagation. This book covers interdisciplinary research between physics, physical chemistry, material sciences and engineering of elastomers within the range from nanometres to millimetres and connects these aspects with the constitutive material properties. The different chapters describe reliable lifetime and durability predictions based on new fracture mechanical testing concepts and advanced material-theoretical methods which are finally implemented in the finite element method for structural simulations. The use of this approach allows a realistic description of complex geometrical and loading conditions which includes the peculiarities of the mechanical behaviour of elastomeric materials in detail. Furthermore, this approach demonstrates how multi-scale research concepts provide an ambitious interdisciplinary challenge at the interface between engineering and natural sciences. This book covers the interests of academic researchers, graduate students and professionals working in polymer science, rubber and tire technology and in materials science at the interface of academic and industrial research.
Author: Ali A. Al-Quraishi Publisher: ISBN: Category : Fillers (Materials) Languages : en Pages : 98
Book Description
The objective of this research is to determine the deformation and fracture characteristics of natural rubber under tensile impact loading. Material tension and fracture experiments were performed on unfilled and 25 phr carbon black-filled natural rubber. The material tension tests were done in order to characterize material stiffness and strength as they vary with strain rate. The fracture tests were done in order to study the effect of high strain rate on the tear energy of natural rubbers. Tensile stress-extension ratio curves up to material failure were generated from the test data at constant strain rates ranging from 0.1 to 229 s−1. Several transitions associated with stain-induced crystallization were observed in both materials. Transitions occurred between 0.1-110 s−1 and above 110 s−1 in the unfilled natural rubber, and for the 25 phr carbon black-filled natural rubber transitions occurred between 0.1-132 s−1 and beyond 132 s−1. The unfilled natural rubber became more compliant when the strain rate increased from 110 to 206 s−1, and it became stiffer when the strain rate increased from 206 to 229 s−1. The filled natural rubber became stiffer when the strain rate increased from 83 to132 s−1, and it became more compliant when the strain rate increased from 132 to s−1. It was found from the fracture experiments that the fracture energy of the unfilled natural rubber did not vary significantly over a range of sample strain rate from 0.01 to 56 s−1, but there was significant variation in the fracture energy of the 25 phr carbon black filled natural rubber from 0.01 to 71 s−1 sample strain rate. The fracture energy of the 25 phr carbon black filled natural rubber at a sample strain rate of 0.1 s−1 was 25 kJ/m2, which was three times greater than it was at 10 s−1 sample strain rate. Furthermore, the carbon black fillers increased the fracture energy of natural rubber at quasi-static sample strain rates (0.01-0.1 s−1) by about 200%, but the carbon black fillers did not improve the fracture energy of natural rubber at sample strain rates between 5-29 s−1. In this strain rate range, the fracture energy of 25 phr carbon black-filled natural rubber was almost the same as that in the unfilled natural rubber. Above a sample strain rate of 30 s−1, the fracture energy was greater than the unfilled natural rubber. Finally, the crack speed did not vary significantly with loading rates for both unfilled and filled natural rubber. The tensile response of 25 phr carbon black-filled natural rubber was used to develop high strain rate constitutive equations. A three-dimensional hyper-viscoelastic constitutive equation to describe the high strain rate material behavior was implemented in ABAQUS Explicit via a user-defined subroutine (VUMAT). Numerical predictions of the far-field forces in the tensile specimen were about 20% higher than that recorded in the experiments. The FEA program was used to predict the strain energy density at the crack tip, and it was found that the strain energy density is within the measured material toughness of the test data. This suggested that the material toughness could be used as a failure criterion for the rubber.
Author: E.E. Gdoutos Publisher: Springer Science & Business Media ISBN: 1402062397 Category : Science Languages : en Pages : 1003
Book Description
This volume contains two-page abstracts of the 482 papers presented at the latest conference on the subject, in Alexandroupolis, Greece. The accompanying CD contains the full length papers. The abstracts of the fifteen plenary lectures are included at the beginning of the book. The remaining 467 abstracts are arranged in 23 tracks and 28 special symposia/sessions with 225 and 242 abstracts, respectively. The papers of the tracks have been contributed from open call, while the papers of the symposia/sessions have been solicited by the respective organizers.
Author: Touhid Zarrin-Ghalami Publisher: ISBN: Category : Elastomers Languages : en Pages : 153
Book Description
This study investigates constitutive behavior, material properties and fatigue damage under constant and variable amplitude uniaxial and multiaxial loading conditions, with the goal of developing CAE analytical techniques for durability and life prediction of elastomeric components. Such techniques involve various topics including material monotonic and cyclic deformation behaviors, proper knowledge of stress/strain histories, fatigue damage quantification parameters, efficient event identification methods, and damage accumulation rules. Elastomeric components are widely used in many applications, including automobiles due to their good damping and energy absorption characteristics. The type of loading normally encountered by these components in service is variable amplitude cyclic loading. Therefore, fatigue failure is a major consideration in their design and availability of an effective technique to predict fatigue life under complex loading is very valuable to the design procedure. In this work a fatigue life prediction methodology for rubber components is developed which is then verified by means of analysis and testing of an automobile cradle mount made of filled natural rubber. The methodology was validated with component testing under different loading conditions including constant and variable amplitude in-phase and out-of-phase axial-torsion experiments. The analysis conducted includes constitutive behavior representation of the material, finite element analysis of the component, and a fatigue damage parameter for life predictions. In addition, capabilities of Rainflow cycle counting procedure and Miner's linear cumulative damage rule are evaluated. Fatigue characterization typically includes both crack nucleation and crack growth. Therefore, relevant material deformation and fatigue properties are obtained from experiments conducted under stress states of simple tension and planar tension. For component life predictions, both fatigue crack initiation approach as well as fatigue crack growth approach based on fracture mechanics are presented. Crack initiation life prediction was performed using different damage criteria. The optimum method for crack initiation life prediction for complex multiaxial variable amplitude loading was found to be a critical plane approach based on maximum normal strain plane and damage quantification by cracking energy density on that plane. The fracture mechanics approach was used for total fatigue life prediction of the component based on specimen crack growth data and FE simulation results. Total fatigue life prediction results showed good agreement with experiments for all of the loading conditions considered.
Author: Zhengwei Qu
Author: Zhengwei Qu
Author: Gert Heinrich
Author: Zhanqi Guo
Author: Jean Lemaitre
Author: C. Bathias
Author: Wolfgang Grellmann
Author: 
Author: Ali A. Al-Quraishi
Author: E.E. Gdoutos
Author: Touhid Zarrin-Ghalami