Littérature scientifique sur le sujet « Microcracked microstructure »
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Articles de revues sur le sujet "Microcracked microstructure"
1
Freim, John, J. McKittrick, W. J. Nellis et J. D. Katz. « Development of novel microstructures in zirconia-toughened alumina using rapid solidification and shock compaction ». Journal of Materials Research 11, no 1 (janvier 1996) : 110–19. http://dx.doi.org/10.1557/jmr.1996.0014.
Texte intégralRésumé :
A rapidly solidified alumina-zirconia eutectic material containing nanocrystalline t-ZrO2 has been synthesized. When heated, the microstructure contained a mixture of t-ZrO2 and m-ZrO2, each of which can facilitate toughening of the composite. Dynamic shock compaction was used to accelerate densification of the material, producing crack-free specimens with high green densities. After sintering to densities measuring ∼95% of theoretical, the shock-compacted specimens fabricated with unstabilized alumina-zirconia were extensively microcracked due to an overabundance of the m-ZrO2 phase. Experiments employing Y2O3 as a chemical stabilizer have shown that the extent of the phase transformation can be controlled, and the microstructure that developed in the stabilized material contained an acceptable level of the microcrack generating m-ZrO2 phase.
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Sevostianov, I., L. Gorbatikh et M. Kachanov. « Recovery of information on the microstructure of porous/microcracked materials from the effective elastic/conductive properties ». Materials Science and Engineering : A 318, no 1-2 (novembre 2001) : 1–14. http://dx.doi.org/10.1016/s0921-5093(01)01694-x.
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Zeng, Qiu Lian, Zhong Guang Wang et J. K. Shang. « Microstructural Effects on Low Cycle Fatigue of Sn-3.8Ag-0.7Cu Pb-Free Solder ». Key Engineering Materials 345-346 (août 2007) : 239–42. http://dx.doi.org/10.4028/www.scientific.net/kem.345-346.239.
Texte intégralRésumé :
Low cycle fatigue behavior of Sn-3.8Ag-0.7Cu solder was investigated under fully reversed cyclic loading, with particular emphasis on microstructural effects. The LCF behavior of the solder with equiaxed microstructure was found to differ greatly from that of the solder with a dendrite microstructure. At a given total strain amplitude, the dendrite microstructure exhibited a much longer fatigue life than the equiaxed microstructure. Such a strong microstructural effect on fatigue life arose from the difference in cyclic deformation and fracture mechanisms between the two microstructures. A large number of microcracks along grain boundaries of the equiaxed structure solder developed with increasing cycling, while for the dendrite structure solder, cyclic deformation took place along the direction of the maximal shear stress during fatigue tests and microcracks initiated and propagated along shear deformation bands. Besides, the fatigue behavior of the dendritic microstructure was very sensitive to cyclic frequency whereas the fatigue behavior of the equiaxed microstructure showed less sensitivity to cyclic frequency.
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Kilicli, Volkan. « Development of an eutectic-based self-healing in Al–Si cast alloy ». Materials Testing 64, no 3 (1 mars 2022) : 371–77. http://dx.doi.org/10.1515/mt-2021-2045.
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Abstract In this study, a self-healing mechanism was developed by means of melting the eutectic structure for microcrack repair in a hypoeutectic Al–Si cast alloy. The alloy was heated just above the eutectic temperature to provide melting of the eutectic in this mechanism. The melted eutectic Si particles repair the microcrack under appropriate conditions. The microcrack formation was provided by tensile loading in Al–Si alloy tensile bars and then eutectic-based self-healing treatment was performed to ensure microcrack healing. Microcrack healing was monitored by X-ray radiography and microstructural examinations were carried out by scanning electron microscopy. The mechanical properties were investigated by tensile testing before and after the healing treatment. Eutectic-based self-healing treatment provides the healing of some microcracks in the microstructure of hypoeutectic Al–Si cast alloy. Also, 44% of yield strength, 59% of ultimate tensile strength, and 86% of total elongation have been recovered by the eutectic-based self-healing process in Al–Si alloy.
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Balart, MarÍa J., Xinjiang Hao et Claire L. Davis. « Automated SEM/EDS Analysis for Assessment of Trace Cross-Contamination in 316L Stainless Steel Powders ». Metallurgical and Materials Transactions A 53, no 2 (1 décembre 2021) : 345–58. http://dx.doi.org/10.1007/s11661-021-06474-4.
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AbstractFollowing observations of microcracking in two, out of three, Additive manufactured (AM) 316L steel samples, an investigation was undertaken to ascertain the root cause. Welding diagrams, taking into account composition and process parameters, could not generally account for the experimental observations of non-cracked versus cracked AM 316L samples. EBSD phase maps in all three AM samples exhibited a fully austenitic microstructure not only in the bulk sample but also near-surface. Analysis of microcracked regions in the AM samples showed the presence of local enrichment of Ni, Cu and P. Automated SEM/EDS analysis on feedstock powder samples prepared for cross-section examination revealed a fine, foreign particulate contaminant, expected to arise from NiCrCuP alloy cross-contamination during atomization, to be completely embedded in a 316L powder particle. This type of contamination would not have been revealed on examination of powder mounted onto a SEM stub, a common approach to assess powder quality. Based on this analysis, it is recommended to consider including automated SEM/EDS analysis on powder cross-sections in any standardization protocol for quality control of powders, to increase the chances of detection and identification of fine cross-contaminants. It is also recommended that atomization of NiCrCuP alloy should no longer precede atomization of 316L alloy.
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Myer, L. R., J. M. Kemeny, Z. Zheng, R. Suarez, R. T. Ewy et N. G. W. Cook. « Extensile Cracking in Porous Rock Under Differential Compressive Stress ». Applied Mechanics Reviews 45, no 8 (1 août 1992) : 263–80. http://dx.doi.org/10.1115/1.3119758.
Texte intégralRésumé :
Under differential compressive stress rocks exhibit nonlinear deformation that includes initial compaction, near-linear elastic behavior, and strain-hardening followed by strain-softening and dilation (or compaction in clastic rocks) and localization. This behavior derives largely from changes in the microstructure of the rocks. Much of it has been attributed to the growth of extensile microcracks. The stress-induced microstructural changes brought about by successively more complicated states of stress produced by uniaxial and triaxial compression of circular cylinders, axisymmetric stresses in hollow cylinders, and indentation by hemispheres in Indiana limestone and Berea sandstone have been preserved using Wood’s metal porosimetry. In this technique molten Wood’s metal at about 100°C is used as a pore fluid at a pressure of about 10 MPa, and the experiments are conducted using the concepts of effective stress. At the deformation state of interest, the temperature is lowered to solidify the metal, thereby preserving the microstructure as it exists under load and facilitating subsequent preparation of the specimen for microscopic study. Mode I microcrack growth is observed to occur by a variety of mechanisms such as bending, point loading and sliding cracks. The effects of this are analyzed using an elastic continuum within which Mode II displacement across microcracks and Mode I microcrack growth results from heterogeneous stress concentrations that produce local tensile stresses. While the continuum model replicates many of the observations, it fails to account for localization by en echelon arrays of extensile microcracks that precede macroscopic shear faulting. Using a “zero order” continuum approximation, the spatially stochastic distribution of grains in clastic rocks is shown to be important in the formation of the en echelon arrays of microcracks that form shear bands.
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Ju, J. W., et Tsung-Muh Chen. « Effective Elastic Moduli of Two-Dimensional Brittle Solids With Interacting Microcracks, Part I : Basic Formulations ». Journal of Applied Mechanics 61, no 2 (1 juin 1994) : 349–57. http://dx.doi.org/10.1115/1.2901451.
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Statistical micromechanical formulations are presented to investigate effective elastic moduli of two-dimensional brittle solids with interacting slit microcracks. The macroscopic stress-strain relations of elastic solids with interacting microcracks are micromechanically derived by taking the ensemble average over all possible realizations which feature the same material microstructural geometry, characteristics, and loading conditions. Approximate analytical solutions of a two-microcrack interaction problem are introduced to account for microcrack interaction among many randomly oriented and located microcracks. The overall elastic-damage compliances of microcrack-weakened brittle solids under uniaxial and biaxial loads are also derived. Therefore, stationary statistical micromechanical formulation is completed. Moreover, some special cases are investigated by using the proposed framework. At variance with existing phenomenological continuum damage models, the proposed framework does not employ any fitted “material parameters. ” “Cleavage 1” microcrack growth and “evolutionary damage models” within the proposed context will be presented in Part II of this series. It is emphasized that microstructural statistical informations are already embedded in the proposed ensemble-averaged equations and, therefore, no Monte Carlo simulations are needed.
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Li, Xu-Dong. « K Variations and Anisotropy : Microstructure Effect and Numerical Predictions ». Journal of Engineering Materials and Technology 125, no 1 (31 décembre 2002) : 65–74. http://dx.doi.org/10.1115/1.1525252.
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Computer experiments were performed on simulated polycrystalline material samples that possess locally anisotropic microstructures to investigate stress intensity factor (K) variations and anisotropy along fronts of microcracks of different sizes. The anisotropic K, arising from inhomogeneous stresses in broken grains, was determined for planar microcracks by using a weight function-based numerical technique. It has been found that the grain-orientation-geometry-induced local anisotropy produces large variations in K along front of microcracks, when the crack size is of the order of few grain diameters. Synergetic effect of grain orientation and geometry of broken grains control K variations and evolution along the microcrack front. The K variations may diminish at large crack sizes, signifying a shift of K calculation to bulk stress dependence from local stress dependence. Local grain geometry and texture may lead to K anisotropy, producing unusually higher/lower K at a segment of the crack front. Either K variation or anisotropy cannot be ignored when assessing a microcrack.
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Wang, Heng, Zhanli Liu, Dandan Xu, Qinglei Zeng et Zhuo Zhuang. « Extended finite element method analysis for shielding and amplification effect of a main crack interacted with a group of nearby parallel microcracks ». International Journal of Damage Mechanics 25, no 1 (29 décembre 2014) : 4–25. http://dx.doi.org/10.1177/1056789514565933.
Texte intégralRésumé :
The shielding and amplification effects of transverse array of microcracks on a main crack are investigated using extended finite element method. The interaction between macrocracks and microcracks is quantitatively characterized in terms of the stress intensity factor which is calculated by the interaction integral method and the complete stress field in the entire domain could be given without remeshing. Various distributions of microcracks with different number, location, and density are considered. For a microcrack collinear to the main crack, the numerical results agree quite well with the analytical solution. Interestingly, the shielding and amplification effects display periodicity when the main crack is placed inside the microcrack rows. In particular, the minimum stress intensity factor of the main crack which refers to the maximum shielding effect is primarily determined by the nearest microcracks. However, the maximum stress intensity factor is largely affected by the distribution and density of microcracks and even could be turned from enhancement to shielding. The results are consistent with the microcrack-toughening phenomenon observed in the experiments and are meaningful for the design of new microstructure-toughening materials.
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Lu, Houdi, Hongtao Wang, Haitao Wang, Lie Jin, Xinxin Wu et Yu Zhou. « FM-DBEM Simulation of 3D Microvoid and Microcrack Graphite Models ». Science and Technology of Nuclear Installations 2017 (2017) : 1–14. http://dx.doi.org/10.1155/2017/1071709.
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The graphite is porous medium, and the geometry and size distribution of its structural deficiencies such as microcracks and microvoids at different oxidation degrees have a great influence on the overall performance. In this paper, we adopt the FM-DBEM to study 3D models which contain spheroidal microvoids and circular microcracks. The accuracy of this method is tested by a comparison to the theoretical solution to the problem of 2D microcrack and microvoid interaction problem. Two simulations are conducted: the simulation of graphite model containing a large number of randomly distributed microcracks and microvoids and the simulation of graphite model containing microcracks and growing microvoids. The simulations investigate the effective moduli versus the two microstructures’ density and the effect of microvoid’s growth on the SIF of microcrack.
Thèses sur le sujet "Microcracked microstructure"
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Mouiya, Mossaab. « Thermomechanical properties of refractory materials, influence of the diffuse microcracking ». Electronic Thesis or Diss., Limoges, 2024. http://www.theses.fr/2024LIMO0066.
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Les matériaux réfractaires sont largement utilisés dans les applications à haute température mais ne sont pas toujours enclins à résister aux chocs thermiques sévères. Pour résoudre ce problème, une microstructure incorporant des microfissures préexistantes est une solution bien connue pour améliorer la résistance aux chocs thermiques. Néanmoins, une telle microstructure endommagée nécessite une meilleure compréhension pour optimiser son design sans compromettre l'intégrité du matériau. Dans un tel contexte, le Titanate d'Aluminium (Al₂TiO₅, AT) présentant une forte anisotropie de dilatation thermique, constitue un système modèle idéal pour créer un réseau de microfissures adapté afin d'améliorer la flexibilité et le comportement à la rupture. Cette thèse étudie les propriétés thermomécaniques des matériaux réfractaires développés à base d'AT, comprenant des céramiques polycristallines et des composites alumine/AT, en mettant l'accent sur les relations entre la microstructure et les propriétés macroscopiques. Dans le cas de ces deux matériaux, les microfissures préexistantes jouent un rôle clé sur le module de Young, le comportement de dilatation thermique, la réponse contrainte-déformation en traction, l'énergie de rupture et donc la résistance aux chocs thermiques. Un effet d’hystérésis significatif sur le module de Young et l’expansion thermique en fonction de la température témoigne des mécanismes de fermeture-réouverture de microfissures. Des essais de traction uniaxiale ont mis en évidence des lois de comportement non linéaires, impactant l'énergie de rupture et la résistance aux chocs thermiques. En particulier, des essais de traction incrémentale à 850 °C ont montré des comportements antagonistes à la montée ou à la descente en température du fait de l’histoire thermique. Les composites (alumine/AT) avec des 0 à 10 % d’inclusions présentent des microfissures diffuses dues à un différentiel d’expansion thermique. Ils présentent un module de Young réduit, des lois de comportement fortement non linéaires et une déformation à la rupture plus élevée à température ambiante. Les essais de choc thermique effectués par le dispositif innovant ATHORNA pour tous les matériaux à base d'AT étudiés ont confirmé leur résilience sous gradient thermique élevé. Ces résultats fournissent des informations précieuses pour le design de futurs matériaux réfractaires avancés présentant une résistance aux chocs thermiques amélioréeRefractory materials are widely used in high-temperature applications but are not always prone to resist severe thermal shock. To address this problem, microstructure incorporating pre-existing microcracks are already well known to improve thermal shock resistance. Nevertheless, such damaged microstructure needs a better understanding to optimize their design without compromising material integrity. In such context, Aluminum Titanate (Al₂TiO₅, AT) exhibiting a great thermal expansion anisotropy, constitutes an ideal model system for creating a tailored microcracks network in order to improve flexibility and fracture behavior. This thesis investigates the thermomechanical properties of developed AT-based refractory materials, including polycrystalline AT and alumina/AT composites, with emphasis on the relationship between microstructure and macroscopic properties. In both materials, pre-existing microcracks play a key role on Young's modulus, thermal expansion behavior, tensile stress-strain response, fracture energy, and thus thermal shock resistance. A significant hysteretic effect on Young's modulus and thermal expansion as a function of temperature indicates microcracks closure-reopening mechanisms. Uniaxial tensile tests revealed nonlinear stress-strain laws, impacting fracture energy and thermal shock resistance. In particular, incremental tensile tests at 850 °C showed contrasting behaviors during heating and cooling, attributed to thermal history. Composite materials with AT inclusions (0 - 10 wt.%) embedded in an alumina matrix exhibit diffuse microcracking due to thermal expansion mismatch. These composites exhibited reduced Young's modulus, highly nonlinear stress-strain laws, and higher strain to rupture at room temperature. Thermal shock tests performed by the innovative ATHORNA device for all studied AT-based materials confirmed their resilience under high thermal gradients. These findings provide valuable insights for the design of future advanced refractory materials with improved thermal shock resistance
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Almansour, Mansour A. « Sulfide stress cracking resistance of API-X100 high strength low alloy steel in H2S environments ». Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/267.
Texte intégralRésumé :
Sulfide Stress Cracking (SSC) resistance of the newly developed API-X100 High Strength Low Alloy (HSLA) steel was investigated in the NACE TM0177 "A" solution. The NACE TM0177 "A" solution is a hydrogen sulfide (H2S) saturated solution containing 5.0 wt.% sodium chloride (NaC1) and 0.5 wt.% acetic acid (CH3COOH). The aim of this thesis was to study the effect of microstructure, non-metallic inclusions and alloying elements of the X100 on H2S corrosion and SSC susceptibility. The study was conducted by means of electrochemical polarization techniques and constant load (proof ring) testing. Microstructural analysis and electrochemical polarization results for X100were compared with those for X80, an older generation HSLA steel. Uniaxial constant load SSC testing was conducted using X100 samples and the results were compared with those reported for older generation HSLA steels.
Addition of H2S to the NACE TM0177 "A" solution increased the corrosion rate of X100from 51.6 to 96.7 mpy. The effect of H2S on the corrosion rate was similar for X80. The corrosion rate for X80 increased from 45.2 to 80.2 mpy when H2S was added to the test solution. Addition of H2S enhanced the anodic kinetics by forming a catalyst (FeHSads) on the metal surface and as a result, shifted the anodic polarization curve to more current densities. Moreover, the cathodic half cell potential increased due to the decrease in pH, from 2.9 to 2.7, which shifted the cathodic polarization curve to more current densities. The increase in both the anodic and cathodic currents, after H2S addition, caused the rise in the corrosion current density.
In H2S saturated NACE TM-0177 "A" solution, the X100 steel corrosion rate was higher than the X80 steel by 20%. Longer phase boundaries and larger nonmetallic inclusions in the X100 microstructure generated more areas with dissimilar corrosion potentials and therefore, a stronger driving force for corrosion. Higher density of second phase regions and larger nonmetallic inclusions acted as an increased cathode area on the X100 surface which increased the cathodic current density and consequently, increased the corrosion current density.
Proof ring tests on the X100 gave a threshold stress value, C5th, of 46% YS, 343.1 MPa(49.7 ksi). The main failure was caused by SSC cracking. SSC nucleated at corrosion pits on the metal surface and microcracks in the metal body and propagated perpendicular to the applied stress. Hydrogen Induced Cracking (HIC) was observed in the X100. HIC cracks nucleated at banded martensite-ferrite interfaces and propagated along the rolling direction parallel to the applied tensile stress through the softer ferrite phase.
When compared to older HSLA grades, the X100 tested in this study had a high SSC susceptibility and therefore, is not be recommended for H2S service applications. The high X100 SSC susceptibility was caused by the material high corrosion rates in H2Smedia which formed corrosion pits that acted as crack initiation sites on the metal surface and provided more hydrogen that migrated into the steel. In addition, the X100
inhomogeneous microstructure provided a high density of hydrogen traps in front of the main crack tip which promoted SSC microcrack formation inside the metal. Microcracks in the metal body connected with the main crack tip that originated from corrosion pits which assisted SSC propagation.
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Shi, Yue. « Micro-mechanics-based models of monotonic and cyclic behaviors of quasi-brittle rock-like materials having an elasto-viscoplastic matrix with microcracks ». Electronic Thesis or Diss., Université de Lille (2022-....), 2023. https://pepite-depot.univ-lille.fr/ToutIDP/EDENGSYS/2023/2023ULILN057.pdf.
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L'objectif principal de cette thèse est de modéliser le comportement mécanique macroscopique des géomatériaux dans des conditions de chargement instantané et dépendant du temps. Dans ce contexte, le matériau étudié est modélisé du point de vue de la microstructure en utilisant des schémas de localisation et d'homogénéisation bien adaptés. À l'échelle microscopique, on suppose que les microfissures ont une morphologie en forme de penny et qu'elles sont intégrées de manière aléatoire dans une matrice solide isotrope. Dans le cadre de la thermodynamique, deux variables internes, la déformation inélastique et les dommages induits par les microfissures, sont toutes deux classées en fonction de la microfissuration instantanée et de la microfissuration sous-critique. L'endommagement instantané est régi par une force thermodynamique conjuguée, tandis que l'endommagement dépendant du temps évolue vers l'équilibre de la microstructure. En outre, l'accent est mis sur la modélisation de la matrice solide en tant que composante de cohésion-friction. Cela nécessite l'introduction d'une nouvelle variable interne, la déformation plastique de la matrice, qui se traduit par une transition fragile-ductile plus claire dans le régime de pré-crête, en particulier sous des pressions de confinement relativement élevées. Ensuite, la matrice plastique compressible est décrite séparément par une règle d'écoulement associée et une règle d'écoulement non associée, en comparaison avec un grand nombre de résultats d'essais. Il s'avère que le modèle non associé peut bien reproduire la transition compaction-dilatation avec des nombres cycliques. Enfin, le modèle unifié est développé pour étudier le comportement à long terme en termes de viscoplasticité de la matrice. Les mécanismes de déformation sont analysés en ce qui concerne le couplage entre la viscoplasticité de la matrice et la propagation sous-critique des microfissuresThe primary objective of this thesis is to model the macroscopic mechanical behavior of geomaterials under both instantaneous and time-dependent loading conditions. In this context, the studied material is modeled from the view of microstructure using well-suited localization and homogenization schemes. At the microscopic scale, it is assumed that microcracks have a penny-shaped morphology and are randomly embedded in an isotropic solid matrix. In framework of thermodynamics, two internal variables, inelastic strain and microcrack-induced damage, are both classified in consideration of instantaneous microcracking and sub-critical microcracking. The instantaneous damage is driven by a conjugated thermodynamics force, while the time-dependent damage evolves towards microstructure equilibrium. Further, the emphasis is put on modeling the solid matrix as a cohesive-friction component. This needs to introduce a new internal variable, plastic strain of matrix, resulting in a clearer brittle-ductile transition in the pre-peak regime, especially under relative high confining pressures. Next, the plastic compressible matrix is separately described by an associated and a non-associated flow rule in comparison with a large amount of test results. It is found that the non-associated model can well reproduce the compaction-dilatation transition with cyclic numbers. Finally, the unified model is developed to investigate the long-term behavior in terms of matrix viscoplasticity. The deformation mechanisms are analyzed regarding the coupling between matrix viscoplasticity and sub-critical propagation of microcracks
Chapitres de livres sur le sujet "Microcracked microstructure"
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Lu, Jinbin, Lifeng Zheng, Feng Chen, Liang Yang et Qiang Zhang. « Experimental Study on Physical and Mechanical Characteristics and Microstructure of Sandstone After High Temperature-Water Cooling Treatment ». Dans Lecture Notes in Civil Engineering, 323–38. Singapore : Springer Nature Singapore, 2024. http://dx.doi.org/10.1007/978-981-97-4090-1_27.
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AbstractIn geothermal energy development, high-temperature rock mass will go through the process of water cooling. It is of great significance to study the physical and mechanical characteristics and microstructure of high-temperature rock after water cooling for the long-term stability analysis of underground engineering. Based on this, the surface characteristics, mass, and volume variation of sandstone cooled by water at high temperatures (100, 200, 400, 600, 800, and 1000 °C) were investigated. Using the Rock Top multifield coupling tester, a series of axial compressions and longitudinal wave velocity tests of the sandstone after a high temperature-water cooling treatment are performed. The microstructure characteristic obtained by X-ray diffraction and scanning electron microscope was studied, and the effect of high temperature-water cooling behavior on the mechanical properties of sandstone was investigated. The results show that: (1) The mass loss rate, volume expansion rate and peak strain of sandstone increase with increasing temperature, while peak strength decreases gradually. When the temperature exceeds 400 °C, the physical and mechanical parameters of sandstone change markedly. (2) When the temperature is less than 400 °C, corresponds to the compressive and line-elastic phases, the stable crack propagation phase, the rapid crack propagation phase and the destructive phase during the failure process of sandstone, the wave velocity of sandstone are steadily increasing, oscillating, and sharply decreasing, respectively. While the temperature is below 1000 °C, the wave velocity of sandstone is oscillation increases, slows down and drops sharply, respectively. (3) When the temperature is below 400 °C, the mineral content of sandstone varies less. While the temperature exceeds 400 °C, there is an overall increasing trend in the sodium feldspar content of sandstone. (4) The increase in temperature promotes the development of pore fractures within the sandstone, especially at higher temperature states where microcracks expand along the intergranular to form microcrack networks, leading to an increase in the scale and number of defects such as fractures within the sandstone.
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Gehling, M. Große, et H. Vehoff. « Simulation of the Stability of Microcracks in Macroscopic Structures ». Dans Microstructures, Mechanical Properties and Processes - Computer Simulation and Modelling, 202–8. Weinheim, FRG : Wiley-VCH Verlag GmbH & Co. KGaA, 2005. http://dx.doi.org/10.1002/3527606157.ch32.
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Yu, Jinyeong, Seong Ho Lee, Seho Cheon, Mooseong Mun, Jeong Hun Lee et Taekyung Lee. « Microstructural Evolution Near Microcrack in AZ31 Mg Alloy Under Electropulses ». Dans Magnesium Technology 2024, 47–48. Cham : Springer Nature Switzerland, 2024. http://dx.doi.org/10.1007/978-3-031-50240-8_9.
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Xia, Junwu, Linli Yu, Zhichun Zhu, Pengxu Li, Yuan He et Jun Yu. « Basic Properties and Microstructure of Coal Gangue Pervious Concrete Under Acid Rain Environment ». Dans Lecture Notes in Civil Engineering, 165–76. Singapore : Springer Nature Singapore, 2024. http://dx.doi.org/10.1007/978-981-97-4090-1_15.
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AbstractTo systematically investigate the durability performance of coal gangue pervious concrete (CGPC) under acid rain environment, various factors are taken into account, including designed porosity, acid rain pH value, and erosion time. These factors affect the mass, compressive strength, and permeability coefficient of CGPC. Moreover, the research delves into the erosion mechanism of acid rain. The results indicate that the compressive strength of CGPC shows an initial increase followed by a subsequent decrease under acid rain environment. The permeability coefficient slightly decreases in the early stage of acid rain erosion, followed by an increase in the later stage. In the acid rain, the reaction between $${\text{SO}}_{{4}}^{{2 - }}$$ SO 4 2 - and Ca2+ generates expansive products such as gypsum. Initially, these products fill the pores, increasing the structural density. However, as erosion progresses, the continuous accumulation of gypsum leads to the formation of expansive microcracks, resulting in a reduction in strength.
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Spicer, James B., José D. Arregui-Mena, Cristian I. Contescu et Nidia C. Gallego. « Effects of Microstructural Composition, Porosity, and Microcracks on the Elastic Moduli of Nuclear Graphites ». Dans Graphite Testing for Nuclear Applications : The Validity and Extension of Test Methods for Material Exposed to Operating Reactor Environments, 34–53. 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959 : ASTM International, 2022. http://dx.doi.org/10.1520/stp163920210073.
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« Microcrack Analysis of Composite Materials[1] ». Dans Metallography and Microstructures. ASM International, 2004. http://dx.doi.org/10.31399/asm.hb.v09.a0009079.
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Wang, Yuwei, Zhenxin Liang, Jia Yang, Li Lu et Qian Sun. « Study on the Microstructure and Properties of T91 Steel Pipe after 96000 Hours Service Under High Temperature and High Pressure ». Dans Advances in Transdisciplinary Engineering. IOS Press, 2023. http://dx.doi.org/10.3233/atde230448.
Texte intégralRésumé :
The microstructure, macro morphology, oxide layer morphology and mechanical properties of T91 steel after 96000 hours of service at high temperature and high pressure were investigated. The results show that the service steel pipe has good macroscopic appearance, no obvious wear, scratch, bulge, deformation, surface crack and other abnormal features, and no obvious thinning of wall thickness. The chemical composition of different pipe sections meets the standard, and the microstructure is mainly tempered martensite, which is evenly distributed, with a small amount of massive ferrite and no obvious coarse phase. The oxidation products are divided into internal oxide layer and external oxide layer, and the internal oxide layer is dense and continuous, microcracks appear in the loose oxide layer. After 96000 hours of service, T91 steel has good mechanical properties. The tensile properties at room temperature and high temperature are good. For room temperature, the yield strength and tensile strength are 480MPa and 630MPa, respectively. Under 500°C and high temperature, the yield strength exceeds 319MPa, the tensile strength exceeds 380MPa, and the elongation exceeds 17%. Hardness test values are between 185∼250 HBW.
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Beheshti, Mohammadali, Saeid Kakooei, Mokhtar Che Ismail et Shohreh Shahrestani. « Investigation of Zn/Ni-Based Electrocatalysts for Electrochemical Conversion of CO2 to SYNGAS ». Dans Electrocatalysis [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.95626.
Texte intégralRésumé :
In the last decade, there is some research on the conversion of CO2 to energy form. CO2 can be converted to value-added chemicals including HCOOH, CO, CH4, C2H4, and liquid hydrocarbons that can be used in various industries. Among the methods, electrochemical methods are of concern regarding their capability to operate with an acceptable reaction rate and great efficiency at room temperature and can be easily coupled with renewable energy sources. Besides, electrochemical cell devices have been manufactured in a variety of sizes, from portable to large-scale applications. Catalysts that optionally reduce CO2 at low potential are required. Therefore, choosing a suitable electrocatalyst is very important. This chapter focused on the electrochemical reduction of CO2 by Zn-Ni bimetallic electrocatalyst. The Zn-Ni coatings were deposited on the low-carbon steel substrate. Electrochemical deposition parameters such as temperature in terms of LPR corrosion rate, microstructure, microcracks, and its composition have been investigated. Then, the electrocatalyst stability and activity, as well as gas intensity and selectivity, were inspected by SEM/EDX analysis, GC, and electrochemical tests. Among the electrocatalysts for CO2 reduction reaction, the Zn65%-Ni35% electrode with cluster-like microstructure had the best performance for CO2 reduction reaction according to minimum coke formation (<10%) and optimum CO and H2 faradaic efficiencies (CO FE% = 55% and H2 FE% = 45%).
Actes de conférences sur le sujet "Microcracked microstructure"
1
Planques, P., V. Vidal, P. Lours, V. Proton, F. Crabos, J. Huez et B. Viguier. « Mechanical Properties of Yttria-Stabilised-Zirconia for Thermal Barrier Coating Systems : Effects of Testing Procedure and Thermal Aging ». Dans ITSC2017, sous la direction de A. Agarwal, G. Bolelli, A. Concustell, Y. C. Lau, A. McDonald, F. L. Toma, E. Turunen et C. A. Widener. DVS Media GmbH, 2017. http://dx.doi.org/10.31399/asm.cp.itsc2017p0302.
Texte intégralRésumé :
Abstract Cyclic oxidation failure of Atmospheric Plasma Sprayed Thermal Barrier Coatings systems (APS TBCs), commonly used to insulate hot sections in gas turbines, usually results from the spallation of the ceramic top coat. Consequently, in order to predict such spalling phenomena, understanding the mechanisms for cracks initiation and propagation in thermal barrier coatings is of utmost concern for engine-makers. Failure of the TBC is strongly related to the thermal and mechanical properties of each component of the multi-materials system (substrate, bond coat and ceramic) but also to the response of the TBC as a whole. The purpose of the work is to assess the mechanical behaviour of thick TBC using experimental approach for TBC standard lamellar, porous and microcracked microstructure (classically obtained through APS coatings). The experimental characterisation of the mechanical behaviour of the ceramic top coat of the TBC is addressed on specifically designed and prepared free-standing specimens using three points bending (3PB) tests and Small Punch Testing (SPT). The tests are performed on free-standing top coats made of YSZ in the as deposited states and for specimens that undergone isothermal aging at 1100°C for various durations (1h, 10h and 100h). The results of test performed at room temperature using both mechanical testing techniques are compared. This allows to show the evolution of mechanical properties after thermal aging. Tests performed at 850°C in the SPT ring show that the evolution of properties resulting from this aging may be different at room temperature as compare to 850°C.
2
Liu, Y., T. Nakamura, V. Srinivasan, A. Gouldstone et S. Sampath. « Mechanism Underlying Anelastic Properties of Thermal Spray Coating ». Dans ITSC2007, sous la direction de B. R. Marple, M. M. Hyland, Y. C. Lau, C. J. Li, R. S. Lima et G. Montavon. ASM International, 2007. http://dx.doi.org/10.31399/asm.cp.itsc2007p0225.
Texte intégralRésumé :
Abstract The microstructure of thermally sprayed ceramic coatings is characterized by the existence of various pores and microcracks. The porous microstructure makes coating desirable for thermal insulation, but this unique microstructural feature also gives rise to anelastic response under tension and compression loads. Detail investigations of curvature measurements of ceramic coated substrate indicate the coatings to exhibit anelastic behavior composed of nonlinear and hysteresis characteristics. In this paper, the mechanisms of such behaviors were studied from curvature-temperature measurements and finite element analysis through modeling the microstructure of yttria stabilized zirconia (YSZ) coating. Computational models contain numerous randomly distributed pores and microcracks with various sizes, aspect ratios, locations and orientations. The effects of such attributes of pores and microcracks on coating anelastic behavior were studied by simulations of curvature change during thermal cycles.
3
Persson, C., P. Bengtsson, J. Wigren et D. Greving. « Modeling and Characterization of Residual Stresses and Microstructure in Thermal Barrier Coatings after Plasma Spraying ». Dans ITSC 1996, sous la direction de C. C. Berndt. ASM International, 1996. http://dx.doi.org/10.31399/asm.cp.itsc1996p0941.
Texte intégralRésumé :
Abstract Thermal barrier coatings with a zirconia top coating and a NiCoCrAlY bond coating were plasma sprayed onto a nickelbase alloy. The pre-heating of the bond coated substrates and the cooling during the top coating spraying were varied to produce five different spray sets. A finite element model was developed to predict the heat transfer and the resulting thermal stresses during the spraying. A layer removal technique was used to measure the residual stresses in the as-sprayed samples. The measurements revealed low residual stresses in the top coatings and tensile stresses in the order of 150 MPa in the bond coating. A correlation between the measured top coating residual stresses and the substrate temperature in the end of the top coating spraying was found. In general, good agreement between modelled and measured residual stresses was found. The top coatings were found to contain vertical microcracks and the densities of the cracks were point-counted in the spray sets. A slight increase in microcrack densities was found as the spraying was performed onto a colder substrate. The densities of vertical microcracks were correlated to modelled in-elastic strain in the top coatings.
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Sevostianov, I., M. Kachanov, J. Ruud, P. Lorraine et M. Dubois. « Micromechanical Analysis of Plasma Sprayed TBC : Anisotropic Elastic and Conductive Properties in Terms of Microstructure and Experimental Verification on YSZ Coatings ». Dans ITSC2003, sous la direction de Basil R. Marple et Christian Moreau. ASM International, 2003. http://dx.doi.org/10.31399/asm.cp.itsc2003p1557.
Texte intégralRésumé :
Abstract Quantitative characterization of microstructures of plasma sprayed coatings, that accounts for their anisotropic and “irregular” character, is developed. An important finding is that “islands” of partial contacts along microcrack faces –even if they are very small - produce a strong effect on both elasticity and conductivity, thus reducing the “effective” microcrack density. Theoretical results are twofold: (1) conductive/elastic properties of the coatings in terms of the microstructure, and (2) conductive–elastic cross-property connections, that interrelate the anisotropic overall conductive and elastic constants. They can be utilized for “mapping” possible combinations of the two properties and, thus, for optimization of the microstructure for the combined conductive/elastic performance. Testing of the model against experimental data on YSZ coatings produces a good agreement.
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Ortner, Susan R. « A Microstructure-Based Probabilistic Model for Cleavage in RPV Steels ». Dans ASME 2006 Pressure Vessels and Piping/ICPVT-11 Conference. ASMEDC, 2006. http://dx.doi.org/10.1115/pvp2006-icpvt-11-93678.
Texte intégralRésumé :
In both simple ferrite-carbide materials, and more complex ferritic steels, cleavage is mediated by the fracture of the particles they contain. If particle cracking is easy, then extension of the resulting particle-sized microcracks into the ferrite matrix, can become the critical step in inducing fracture. Under these circumstances, brittle fracture is essentially stress-controlled, and several models use this as a basis for failure prediction. Fracture toughness data from a series of MnMoNi steels are presented, together with observations of fracture initiation sites, and calculations of the stresses and strains pertaining to these locations at failure, to show that there are circumstances under which particle cracking is not easy. A strain criterion is found to describe the probability of particle cracking effectively. A previously-published, stress-based model is generalised to include the strain criterion. The more general model correlates initiation site properties with K, and predicts a marked temperature-dependence of K (i.e. a ductile-to-brittle transition), even though the only temperature-dependent input parameters are the flow properties. Other input parameters for the model are linked explicitly to the microstructure. The relative dominance of particle cracking and microcrack extension in cleavage depends most strongly on initiating particle type, and final quench severity.
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Bianchi, L., N. Llorca-lsern et G. Bertran. « Microstructural Evaluation of Plasma Sprayed Coatings Using Fractal Characterization ». Dans ITSC2001, sous la direction de Christopher C. Berndt, Khiam A. Khor et Erich F. Lugscheider. ASM International, 2001. http://dx.doi.org/10.31399/asm.cp.itsc2001p0967.
Texte intégralRésumé :
Abstract Depending on working parameters, plasma spraying process allows to achieve original metallic and/or ceramic coating microstructures varying from quite dense to high porosity materials. Combined to the versatility of the process in terms of coating shaping, this leads to an extended field of applications. For instance, porous coatings are required for stress accommodation or filtering applications due to their high specific area, whereas dense coatings are needed for the electrolyte in S.O.F.C technology. Past works have shown that porosity is not a convenient parameter to describe completely coating microstructure and that the main difficulty is to find a unique parameter capable to describe the microcrack network and pores distribution. In this paper we propose a fractal approach of coating microstructure based on confocal microscopy of fluorescent impregnated coatings. Fractal dimensions as well as porosity data are given and analyzed for various plasma-spayed coating microstructures. This work is a contribution to characterize plasma-sprayed coatings. Coatings properties are related to the microstructure which depends on the spraying process.
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Dubský, J., P. Chráska, S. Ahmaniemi, M. Vippola, P. Vuoristo et T. Mäntylä. « Effect of Aluminum Phosphate Sealing on the Elastic Properties of Plasma Sprayed Ceramic Coatings ». Dans ITSC2003, sous la direction de Basil R. Marple et Christian Moreau. ASM International, 2003. http://dx.doi.org/10.31399/asm.cp.itsc2003p0617.
Texte intégralRésumé :
Abstract Plasma sprayed ceramic coatings have much lower stiffness in comparison to sintered ceramics. The reason for that is their characteristic microstructure with porosity and microcracks. Microcracks decrease the interlamellar cohesion in vertical direction, but also affect the individual splat properties in the horizontal direction. For that reason sealing treatments are often applied with plasma sprayed ceramic coatings in order to improve their corrosion resistance and mechanical properties. In this paper the effect of aluminum phosphate sealing treatment on the elastic properties of plasma sprayed Al2O3 and Cr2O3 coatings were studied. Residual stresses in the plane of coating surfaces were compared using the X-ray diffraction analysis (XRD). A special four point bending device, designed for the X-ray diffractometer, was used in determining the effect of additional load on coating elastic behavior. In as-sprayed alumina coatings tensile stresses of about 400 MPa were detected while only about 40 MPa of compressive stresses were measured in the as-sprayed chromia coatings. Microstructural characterization revealed that sealing treatment had apparently affected the coating microstructure and filled some microcracks and interlamellar spacings. As a result, in both sealed coatings, compressive stresses of about 100 up to 150 MPa were observed. Also a better stiffness of both materials was detected during the bending of specimens. In addition, the sealing treatment increased nearly ten times the Young’s modulus, determined by XRD analysis under various tensile loads.
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Ma, X. Q., J. Roth, T. D. Xiao et M. Gell. « Study of Unique Microstructure in SPS Ceramic NanoCoatings ». Dans ITSC2003, sous la direction de Basil R. Marple et Christian Moreau. ASM International, 2003. http://dx.doi.org/10.31399/asm.cp.itsc2003p1471.
Texte intégralRésumé :
Abstract Ceramic oxide coatings were made with a unique microstructure using solution plasma spray (“SPS”), a novel variant on the conventional powder plasma spray techniques. In the SPS process, a precursor solution is fed into an air plasma torch using a liquid injector, and a nanocrystalline ceramic coating is formed directly on various substrates without post heat treatment. It was found that the microstructure of the SPS coating depended on control of process parameters for liquid feed and plasma spray to a large extent. This study deals with the formation of SPS deposited yttria stabilized zirconia coatings with a well-controlled microstructure addressing porosity, cracking and adhesion. The SPS-deposited YSZ coatings have demonstrated unique microstructural characteristics including adjustable porosity, vertical microcracks and the absence of splat boundaries. Such zirconia-base coatings show great potential for the applications of high-density electrolyte layers in solid oxide fuel cells (“SOFC”s) and high porosity/low conductivity thermal barrier coatings for industrial and gas turbines.
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Hu, Wenqian, Galen B. King et Yung C. Shin. « Micromachining of Metals, Alloys and Ceramics by Picosecond Laser Ablation ». Dans ASME 2008 International Manufacturing Science and Engineering Conference collocated with the 3rd JSME/ASME International Conference on Materials and Processing. ASMEDC, 2008. http://dx.doi.org/10.1115/msec_icmp2008-72247.
Texte intégralRésumé :
Microhole drilling and microstructure machining with a picosecond (ps) Nd:YVO4 laser (pulse duration of 10 ps) in metals, alloys and ceramics are reported. Blind and through microholes were drilled by percussion drilling as well as trepanning drilling. The diameters of the holes were in the range from 20 μm to 1000 μm. Microfeatures were machined and the flexibility of ps laser machining was demonstrated. The quality of drilled holes, e.g., recast layer, microcrack and conicity, and that of the microstructures, were investigated by optical microscope, surface profilometer, or scanning electron microscope (SEM). Ps laser ablation rate was investigated by experiments as well as a simplified laser ablation model.
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Basu, S. N., G. Ye, C. Cui, M. Gevelber, D. Wroblewski, J. R. Fincke et W. D. Swank. « Plasma Sprayed Coatings with Engineered Microstructures ». Dans ITSC2003, sous la direction de Basil R. Marple et Christian Moreau. ASM International, 2003. http://dx.doi.org/10.31399/asm.cp.itsc2003p1599.
Texte intégralRésumé :
Abstract An advanced closed loop control system that enables tight control of the particle and substrate states has been developed. This unique capability allows deposition of coatings under very controlled conditions. This enables the construction of detailed process/property maps that can lead to a fundamental understanding of the formation mechanisms of key microstructural features during the plasma deposition process. The microstructural development during processing is discussed in light of the physics of microcrack formation during plasma deposition, including the effect of particle and substrate states on splat solidification, thermal gradients and residual stresses.