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Дисертації з теми "Caoutchouc – Matériaux – Fatigue"
Raoult, Ida. "Structures élastomères sous chargement cyclique : Comportement – Fatigue – Durée de vie." École polytechnique, 2010. http://www.theses.fr/2010EPXX0090.
Повний текст джерелаThe automotive industry must ensure the service life of numerous rubber components used for anti vibratory purposes. This work aims at proposing a method to predict the fatigue life of a carbon-black reinforced natural rubber structure. The approach proposed here consists in uncoupling the evolution of the mechanics behaviour and damage under cyclic loading. We make the assumption that the behaviour tends to stabilize and that the lifetime, defined as the initiation of a crack, depends only on the mechanical variables in the stabilized state. Upon cyclic loading, elastomers experience a stress-softening phenomenon known as the Mullins’ effect. This phenomenon occurs mostly during the first few cycles, after which the response of the material remains unchanged by additional reloading. We propose a model to represent this stabilized state, supposed to depend only on some cyclic variables. The parameters are the maximum stretches reached in a finite number of material directions, in order to describe the anisotropy induced by the Mullins’ effect. This model is used to analyse a large number of uniaxial and multixial fatigue tests realised with cylindrical dumbbell specimens. We show its ability to take into account the type of control (force or displacement) and the influence of an initial overload. The analysis of the multiaxial data indicates that the maximum principal stress is well correlated with lifetime for all types of solicitations, excepting those which involve multi-plane cumulative damage. A cumulative damage law is proposed to account for these types of loading
Bennani, Amine. "Elaboration, Comportement et Durée de vie en Fatigue du Caoutchouc Naturel chargé de Silice." Paris, ENMP, 2006. https://pastel.archives-ouvertes.fr/tel-00136825.
Повний текст джерелаNatural rubber has long been reinforced by stiff fillers such as carbon black in order to improve mechanical properties (breaking strength, abrasion, rigidity…). The introduction of silica particles to the library of potential fillers offers new possibilities to further tailor the properties of Natural rubber via blending. Introduce silica instead of carbon black is a challenge in pneumatic industry. Synthetic-based elastomers filled with silica particles decrease in rolling friction of the tires while also retaining a good adherence. The goal of this study is to explore the influence of silica particles one the mechanical behavior, stiffness, strength, hysterisis, fatigue lifetime, of natural rubber. The main purpose is to understand the influence of the morphology of silica (Interaction surfaces between filler with rubber, dispersion with random distribution, chemical activity) on the mechanical behavior and on the fatigue lifetime. Also, Two blends with two different morphology of silica were produced. The both blends were made to obtain similar rheology properties. Experiments investigations were performed to identify the mechanical behavior such as (tension, compression, torsion ,cyclic loading, relaxation tests) and mechanisms of deformation and damage were estimated from uniaxial elongation in combination with in situ SEM micrographs tests. The micro-structure of the blends were studied through SEM observations and uniaxial elongation in combination with in situ X-ray. Theses studies indicate respectively a good dispersion of the filler and a crystallization of soft-segment induced by elongation. Fatigue experimental results with fractographic observations allow to built a new model of lifetime prediction. This model is able to predict the location and orientation of cracks as well as the fatigue lifetime. The life time experiments and numerical tests study shows how the two different silica particles reinforced natural rubber , when subjected to various mechanical loading conditions (uniaxial, hydrostatic, monotonic, cyclic)
Lacroix, Florian. "Etude du comportement en fatigue des caoutchoucs synthétiques." Tours, 2004. http://www.theses.fr/2004TOUR4060.
Повний текст джерелаThe behaviour of an elastomer being a close function of its service conditions (stress, temperature or the environment), it is very difficult to study its fatigue resistance. This study is focused essentially an crack initiation, a subject seldom studied. The aim of this study, in the industrial context is to increase the fatigue life of a chloroprene elastomer and to identify a mechanical parameter characteristic of fatigue. The second aim is to correlate laboratory specimen behavior with that of real components (tested in special set ups) by means of a finite element simulation. We have identified a scalar parameter, representing the dissipated energy and determined by a visco-hypereleastic constitutive low. Different crack techniques to detect crack initiation were tested and a critical analysis has beeen made on the efficiency of these techniques
Beurrot, Stéphanie. "Cristallisation sous contrainte du caoutchouc naturel en fatigue et sous sollicitation multiaxiale." Ecole Centrale de Nantes, 2012. https://tel.archives-ouvertes.fr/tel-00835499.
Повний текст джерелаNatural rubber is well-known for its excellent mechanical properties in multiaxial fatigue and those are generaly attributed to the ability of the material to crystallize when strained. However, the relationship between strain-induced crystallization and mechanical properties of natural rubber has never been established. The aim of this thesis is therefore to understand the origin of the great multiaxial fatigue properties of carbon black-filled natural rubber, by considering two small scales of study, as opposed to the macroscopic scale generally considered. The first part of this thesis is dedicated to uniaxial crack growth and energy dissipation mechanisms at the cracks and micro-cracks scale ; those mechanisms are determined thanks to original in-situ propagation tests observed with scanning electron microscope. In the second part of the thesis, strain-induced crystallization is studied at the macromolecular scale, in static multaxial deformation on the one hand and in uniaxial fatigue on the other hand, thanks to X-ray diffraction measurements performed at the Soleil synchrotron facility. The characteristics of crystallites, i. E. Their size, orientation, number and lattice parameters, are measured during the different mechanical tests. We observe that in multiaxial deformation, the crystallites are similar in size and have the samei lattice parameters than those nucleated in uniaxial deformation, but their orientation strongly varies with the multiaxiality of the deformation and is not influenced by the loading path. Finally, we show that in uniaxial fatigue, the characteristics of the crystallites evolve with the number of cycles, differently depending on the minimum and maximium stretch ratios reached at each cycle
Ostoja-Kuczynski, Élisabeth. "Comportement en fatigue des élastomères : application aux structures antivibratoires pour l'automobile." Nantes, 2005. http://www.theses.fr/2005NANT2153.
Повний текст джерелаThe delivery time for a new car project was previously five years and is now two years. In this context, the numerical simulation should replace experiments in order to sufficiently reduce the design time of new components. Nowadays, simulation of static and dynamic responses of new AVS components is widely used during the design loop, but duration life estimation remains a critical objective for rubber manufactures. In this context, a fatigue life criterion is a necessary pre-requisite to numerically establish the relevance of technical solutions before their experimental validation. In this work, several aspects of fatigue of rubbers are studied : 1 – very long and very short duration life, 2 – reinforcement phenomenon under non-relaxing conditions, 3 – temperature influence and 4 – multiaxiality effects. For each case, propagation law and initiation law are investigated in order to demonstrate that propagation and initiation were drive by similar physical mechanisms
Rublon, Pierre. "Etude expérimentale multi-échelle de la propagation de fissure de fatique dans le caoutchouc naturel." Ecole centrale de Nantes, 2013. http://www.theses.fr/2013ECDN0003.
Повний текст джерелаThis PhD thesis aims to experimentally characterizethe fatigue crack growth behaviour in natural rubber, and is particularly interested in the neighbourhood of thecrack tip where the well-known phenomenon of straininduced crystallization takes place due to the large strains in this region. The final goal is therefore to explain the outstanding fatigue properties and crack growth resistance of natural rubber which are recognized for a while in literature. On the one hand, fatigue crack growth rate tests are performed to evaluate the influence of various parameters such as the type of elastomer, the carbon-black content and non-relaxing conditions, on the fatigue crack growth resistance. On the other hand, various experimental methods are used at different scales to characterize the fatigue crack tip neighbourhood. First of all, a synchrotron radiation allows us to measure quantitatively the strain-induced crystallization phenomenon at the crack tip using the wide-angle X-ray diffraction method. Moreover, those results are related to strain field measurements obtained by digital image correlation. Besides, an original fatigue experiment performed in a scanning electron microscope enables us to observe in situ the fatigue crack growth mechanisms at the crack tip. Finally, all these experimental results, compared to macroscopic measurements of fatigue crack growth rates in our samples, lead to a discussion about the influence that has the strain-induced crystallization phenomenon on the resistance to fatigue crack growth in natural rubber
Warneboldt, Iona. "Multiaxial fatigue design of elastomeric parts using Equivalent Fatigue Loads." Electronic Thesis or Diss., Brest, École nationale supérieure de techniques avancées Bretagne, 2022. http://www.theses.fr/2022ENTA0002.
Повний текст джерелаThis thesis introduces an Equivalent Fatigue Load (EFL) approach for the multiaxial fatigue design of elastomeric parts. As direct Finite Element Analysis (FEA) calculations of automotive in-service loads (Road Load Data (RLD)) are too expensive, the objective is to derive simplified load blocks as a realistic input for numerical damage calculations. Three streps are applied for this method: the localization method, the material damage function and the EFL determination process. Various fatigue tests have been conducted (415 samples) to study the fatigue behavior of this complex type of relaxing and non-relaxing multiaxial loading on natural rubber specimens. Lifetime and crack features are analyzed to eventually introduce an appropriate critical planebased fatigue measure and to establish a novel mean strain effect model. This criterion is generalized throughout an original critical plane search method. To estimate the local mechanical response (localization method), this thesis identifies an axes-coupling method that is fitted for the nonlinear nature of elastomeric structures. It is based on the multiplicative decomposition of the deformation gradient tensors. These two steps are then implemented in the framework of the EFLdetermination process. For this, a global optimization method is added to determine the simplified load blocks, causing locally the same fatigue behavior in the given structure. The computational costs of this optimization are reduced by only considering a subset of the most damaged material points for EFLdetermination. Finally, the method has been challenged on a specimen to outline its capabilities and to validate the approach
Gauchet, Séverine. "Etude de l'influence du type de noir de carbone sur la tenue en fatigue de caoutchouc HNBR." Tours, 2007. http://www.theses.fr/2007TOUR4049.
Повний текст джерелаThe fatigue resistance optimization of the alternator pulley needs to understand damage mechanisms influence on the rubber fatigue behaviour used in mecanical power transmission. Although the toughness of rubber was log time studed, the fatigue of HNBR filled with carbon black is not described in literature. The aim of this work is to understand the influence of filler on theses complex mechanisms through the modifications induiced by filler on the microstructure and dynamical properties. Two damage mechanisms at starting initiate several microcracks which are propagated in rosette forme. Size and number of petals depend on the type of carbon black. This characteristics represent the cracking speed and they describe a mechanisme of crack rotation. The influence of filler on the damage is highlighted by solid NMR H. This original technique proves to be a power technique for studying degradation of rubber having a complex formulation. These results open new propects in order to understand damage mechanisms
Pire, Myriam. "Caoutchouc naturel époxydé et réticulation par les acides dicarboxyliques : chimie, cinétique et propriétés mécaniques." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2011. http://pastel.archives-ouvertes.fr/pastel-00732940.
Повний текст джерелаDemassieux, Quentin. "Structural changes in the process zone of a cyclic fatigue crack in filled natural rubber." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066074.
Повний текст джерелаFilled natural rubbers are widely used in structural parts such as tires for their outstanding mechanical properties. Their exceptional behavior is often associated to the ability of natural rubber chains to form a crystalline structure under tension. In the case of cyclic fatigue cracking, the dissipation added through crystallization and melting at the crack tip is often seen as the main reinforcing mechanism that reduces fatigue crack growth. This PhD work focused on all the dissipative mechanisms activated by the strain amplification near a crack tip. An extensive use of X-ray scattering was made to investigate sub-micronic changes in structure (strain-induced crystallization, cavitation, filler network). A study was made in uniaxial tension to understand the effects of material composition and test environment on these structure changes. The effect of filler volume fraction, crosslink density, thermal ageing and test temperature were considered. This study was followed by a complete description of several fatigue crack-tips. Digital image correlation was used to map the strain fields at the vicinity of the cracks, while X-ray mapping of the process zone gave information on the local changes in structure. The cyclic fatigue properties of the materials were then discussed through the knowledge acquired both in uniaxial tension and near crack-tips. It showed that the effect of strain induced-crystallization far outweigh the dissipation added