Academic literature on the topic 'Microstructural differences'
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Journal articles on the topic "Microstructural differences"
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Costin, Walter, Olivier Lavigne, Andrei G. Kotousov, Reza Ghomashchi, Ian H. Brown, Valerie Linton, and Frank J. Barbaro. "Susceptibility of Acicular Ferrite and Upper Bainite Microstructures to Hydrogen Assisted Cold Cracking Propagation." Materials Science Forum 909 (November 2017): 44–49. http://dx.doi.org/10.4028/www.scientific.net/msf.909.44.
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Acicular ferrite (AF) and upper bainite (UB) are microstructural constituents commonly found in ferritic weld metals. Both microstructures are formed within a similar temperature range and by the same type of transformation mechanisms. They have however, substantially different morphologies and microstructural features that govern both their mechanical properties and hydrogen embrittlement susceptibility. This work shows that despite substantial microstructural differences, the mechanical properties of both microstructural constituents were quite similar. However, the microstructural differences were found to significantly affect the hydrogen crack propagation resistance. Hydrogen assisted cold cracking (HACC) propagates along a path of least resistance through the surrounding microstructure. The unit crack path was significantly shorter for AF than for UB, which implied more frequent changes in direction and thus increased dissipation of energy from the crack driving force. These results suggest that AF, possessing fine interlocking grains and high angle grain boundaries (HAGB), increases the localised resistance to HACC propagation more than UB due to the impediment of brittle, cleavage-like crack propagation at HAGB’s.
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Reginster, Sylvie, Anne Mertens, Hakan Paydas, Jerome Tchoufang Tchuindjang, Quentin Contrepois, Thierry Dormal, Olivier Lemaire, and Jacqueline Lecomte-Beckers. "Processing of Ti Alloys by Additive Manufacturing: A Comparison of the Microstructures Obtained by Laser Cladding, Selective Laser Melting and Electron Beam Melting." Materials Science Forum 765 (July 2013): 413–17. http://dx.doi.org/10.4028/www.scientific.net/msf.765.413.
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In this study, samples of alloy Ti-6Al-4V have been processed by different additive manufacturing techniques in order to compare the resulting microstructure. In all three processes, ultrafast cooling gives rise to strongly out-of-equilibrium microstructures. However, the specific of the heat flow in each process lead to significant differences as far as the grains orientation and the resulting microstructural anisotropy are concerned.
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Harkness, S. D., W. Lewis, M. Bartholomeusz, and M. Tsai. "Effect of target processing on CoCrPtTa thin-film media." Journal of Materials Research 15, no. 12 (December 2000): 2811–13. http://dx.doi.org/10.1557/jmr.2000.0401.
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The ensuing paper summarizes an investigation on the effect of target microstructural morphology on resultant sputter deposited media magnetic performance. Significant differences in media magnetic coercivity were obtained from Co–Cr–Pt–Ta targets possessing the same chemistry, sputtered under identical conditions, but possessing different microstructural phase and crystallographic texture characteristics. This result was most likely caused by the difference in sputter yields for the Ta-containing phases in the two distinct target microstructures. Results support enhanced chromium segregation yielding a decrease in the intergranuler exchange energy field for the deposited thin films.
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Nolan, T. P., R. Sinclair, T. Yamashita, and R. Ranjan. "Correlation of micro-structural, micro-chemical and micro-magnetic properties of longitudinal recording media using CM20FEG Lorentz TEM." Proceedings, annual meeting, Electron Microscopy Society of America 52 (1994): 892–93. http://dx.doi.org/10.1017/s042482010017219x.
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Cobalt alloy on chromium thin film magnetic media are used in industry computer hard disk drives because of their large values of coercivity (Hc), remanent magnetization (Mr), squareness (S*), and relatively low noise. The magnetic performance depends strongly on processing conditions and the resulting nanometer scale microstructure.A complete structure-processing-properties analysis requires effective measurement of magnetic and microstructural properties. To date, most structure-properties analyses have involved correlation of bulk magnetic (hysteresis loop) properties and magnetic recording measurements with physical microstructures observed by high-resolution SEM and TEM.The nanoscale microstructural features that dramatically affect magnetic properties are difficult to observe but careful TEM analysis has been used to observe subtle, important differences in the atomic scale physical microstructure. Even these impressive capabilities are becoming insufficient for continued development of improved magnetic recording media. Microstructural design is moving into a regime where appropriate control of magnetic properties requires control of elemental composition and second phase formation as well as crystallography and morphology, at near-atomic levels.
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Tadesse, Abel, and Hasse Fredriksson. "The Effect of Inoculation on the Thermal Expansion/Contraction during Solidification of Gray Cast Iron." Materials Science Forum 790-791 (May 2014): 447–51. http://dx.doi.org/10.4028/www.scientific.net/msf.790-791.447.
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Inoculation of casting used to improve the microstructure and the properties of the component. Depending upon the area of application, gray cast iron has different microstructure and mechanical properties. The type and amount of the inoculation result in shape and orientation differences of the flake graphite. The Linear Variable Differential Transformer (LVDT) shows a variation in displacements change during the solidification. Temperature measurement used to analyze cooling curves and microstructural analysis of sample to examine the physical differences. Thermal analysis compared with the experimental results and microstructural study for describing the variation in area fraction and shape of graphite. The experimental result indicates contraction in austenite formation region, and expansion in eutectic formation region. The effect of the inoculant and the superheat temperature shows a variation in degree of expansion/contraction and cooling rates of the experiments. The comparisons between the experimental and the theoretical results have been done. Combining the theoretical and experimental results, it resembles a difference in eutectic formation region, and it needs carful investigation in future works.
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Rubenis, Kristaps, Agnese Pura, Valdis Teteris, Janis Locs, and Jurijs Ozolins. "Effect of Shaping Method and Heat Treatment on Microstructure and Thermoelectric Properties of Titanium Dioxide." Key Engineering Materials 604 (March 2014): 240–44. http://dx.doi.org/10.4028/www.scientific.net/kem.604.240.
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The TiO2samples were obtained by two different shaping methods: cold isostatic pressing and cold extrusion, sintered in air at 1373 K, 1573 K, 1773 K and annealed under vacuum at 1373 K. Differences in density, microstructure and thermoelectric properties were observed between the samples depending on the shaping method used. With increase in sintering temperature the electrical conductivity of all samples increased while the Seebeck coefficient decreased. Great microstructural differences were observed between the surface and bulk of the samples made by each of the shaping techniques. It was found that microstructural differences between surface and bulk of the samples affect their thermoelectric properties.
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SINGH, NANDINI C., ARCHITH RAJAN, ARCHANA MALAGI, KEERTHI RAMANUJAN, MATTEO CANINI, PASQUALE A. DELLA ROSA, PARTHA RAGHUNATHAN, BRENDAN S. WEEKES, and JUBIN ABUTALEBI. "Microstructural anatomical differences between bilinguals and monolinguals." Bilingualism: Language and Cognition 21, no. 5 (October 9, 2017): 995–1008. http://dx.doi.org/10.1017/s1366728917000438.
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DTI is an established method to study cerebral white-matter microstructure. Two established measures of DTI are fractional anisotropy (FA) and mean diffusivity (MD) and both differ for bilingual and monolingual speakers. Less is known about differences in two other measures called radial (RD) and axial diffusivity (AD). We report differences in mean RD and AD-values in the right superior longitudinal fasciculus (SLF) and forceps minor between bilingual (Hindi–English) and monolingual (English) speakers as well as differences in mean FA-values in the anterior thalamic radiation, right inferior fronto-occipital and inferior longitudinal fasciculus (ILF) and mean MD-values in forceps minor and bilateral SLF. Noteworthy, a positive correlation between L2 proficiency and mean RD-values in the right SLF was observed. We suggest that changes in the geometry of white matter tracts reflect regular bilingual language experience and contend that neuroplasticity in right SLF results from demands on cognitive control for bilingual speakers.
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Islam, Showmic, Musa Norouzian, and Joseph A. Turner. "Influence of tessellation morphology on ultrasonic scattering." Journal of the Acoustical Society of America 152, no. 3 (September 2022): 1951–61. http://dx.doi.org/10.1121/10.0014288.
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Material properties, such as hardness, yield strength, and ductility, depend on the microstructure of the material. If the microstructural organization can be quantified nondestructively, for example, with ultrasonic scattering techniques, then it may be possible to predict the mechanical performance of a component. Three-dimensional digital microstructures have been increasingly used to investigate the scattering of mechanical waves within a numerical framework. These synthetic microstructures can be generated using different tessellation algorithms that result in different grain shapes. In this study, the variation of ultrasonic scattering is calculated for microstructures of different morphologies for a nickel polycrystal. The ultrasonic properties are calculated for the Voronoi, Laguerre tessellations, and voxel-based synthetic microstructures created by DREAM.3D. The results show that the differences in the two-point statistics and ultrasonic attenuation for different morphologies become more significant at wider size distributions and higher frequencies.
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Hubbard, Nicholas A., Monroe Turner, Joanna L. Hutchison, Austin Ouyang, Jeremy Strain, Larry Oasay, Saranya Sundaram, et al. "Multiple sclerosis-related white matter microstructural change alters the BOLD hemodynamic response." Journal of Cerebral Blood Flow & Metabolism 36, no. 11 (July 22, 2016): 1872–84. http://dx.doi.org/10.1177/0271678x15615133.
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Multiple sclerosis (MS) results in inflammatory damage to white matter microstructure. Prior research using blood-oxygen-level dependent (BOLD) imaging indicates MS-related alterations to brain function. What is currently unknown is the extent to which white matter microstructural damage influences BOLD signal in MS. Here we assessed changes in parameters of the BOLD hemodynamic response function (HRF) in patients with relapsing-remitting MS compared to healthy controls. We also used diffusion tensor imaging to assess whether MS-related changes to the BOLD-HRF were affected by changes in white matter microstructural integrity. Our results showed MS-related reductions in BOLD-HRF peak amplitude. These MS-related amplitude decreases were influenced by individual differences in white matter microstructural integrity. Other MS-related factors including altered reaction time, limited spatial extent of BOLD activity, elevated lesion burden, or lesion proximity to regions of interest were not mediators of group differences in BOLD-HRF amplitude. Results are discussed in terms of functional hyperemic mechanisms and implications for analysis of BOLD signal differences.
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Hao, Jia, Wang Yao, W. B. Ryan Harris, Joy Y. Vink, Kristin M. Myers, and Eve Donnelly. "Characterization of the collagen microstructural organization of human cervical tissue." Reproduction 156, no. 1 (July 2018): 71–79. http://dx.doi.org/10.1530/rep-17-0763.
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The cervix shortens and softens as its collagen microstructure remodels in preparation for birth. Altered cervical tissue collagen microstructure can contribute to a mechanically weak cervix and premature cervical dilation and delivery. To investigate the local microstructural changes associated with anatomic location and pregnancy, we used second-harmonic generation microscopy to quantify the orientation and spatial distribution of collagen throughout cervical tissue from 4 pregnant and 14 non-pregnant women. Across patients, the alignment and concentration of collagen within the cervix was more variable near the internal os and less variable near the external os. Across anatomic locations, the spatial distribution of collagen within a radial zone adjacent to the inner canal of the cervix was more homogeneous than that of a region comprising the middle and outer radial zones. Two regions with different collagen distribution characteristics were found. The anterior and posterior sections in the outer radial zone were characterized by greater spatial heterogeneity of collagen than that of the rest of the sections. Our findings suggest that the microstructural alignment and distribution of collagen varies with anatomic location within the human cervix. These observed differences in collagen microstructural alignment may reflect local anatomic differences in cervical mechanical loading and function. Our study deepens the understanding of specific microstructural cervical changes in pregnancy and informs investigations of potential mechanisms for normal and premature cervical remodeling.
Dissertations / Theses on the topic "Microstructural differences"
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Minani, Evariste. "Growth temperature and microstructural differences in hydrogenated amorphous silicon deposited on glass substrates." Master's thesis, University of Cape Town, 2002. http://hdl.handle.net/11427/6995.
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Includes bibliography.Hydrogenated amorphous silicon (a-Si:H) is an important thin film semiconductor with a wide variety of applications in microelectronics and optoelectronics. However, it is metastable and photodegrades after a moderate light illumination (Staebler-Wronski effect). The most stable material has been suggested to be at the edge of crystallinity with microcrystalline inclusions. Using a combination of positron annihilation and X-ray diffraction techniques, the microstructure of hydrogenated amorphous silicon grown by hot wire chemical vapour deposition on glass substrates at different substrate temperatures ranging between 300°C and 500 °C is examined. In previous studies the crystallisation was accompanied by a relaxation of defect structure with an increase in free volume at positron annihilation site. In this work, both techniques show a relaxation of the network with increasing growth temperature, leading to a higher degree of ordering, shorter bond lengths, and a reduction in the average size of defects in the material.
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Freeman, Felicity. "Structuring difference : the additive manufacture of spatially & functionally differentiated microstructures." Thesis, University of Sheffield, 2018. http://etheses.whiterose.ac.uk/22742/.
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Additive manufacturing is an enabling technology for achieving spatially-differentiated functionally-graded materials at a resolution that could not be realised by conventional methods. This work covers the development of an in-situ magnetically and microstructurally graded material, built by selective laser melting from a single composition of 17-4PH stainless steel. The high solidification rates of additive manufacture are exploited to drive very fine austenite grain and cell sizes, suppressing the thermally-driven martensitic transformation and stabilising austenite. But additively manufactured parts are known to suffer from thermal strain, and the low stacking fault energy of metastable retained austenite makes it susceptible to deformation-driven transformation. Regions engineered to have low thermal strain remain fully austenitic and demonstrate paramagnetic behaviour, while other regions, tailored to have higher thermal strain, partially transform to ferromagnetic martensite. The magnetic properties are proportional to the phase composition, and therefore to thermal strain, and are shown to be controllable through the build parameters and geometry. The applications for this type of magnetically graded material include electrical machine architectures, and a SLM-built in-situ magnetically graded rotor is demonstrated in a synchronous motor.
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REBIBO, JACQUES. "Influence de la microstructure d'aciers sur l'attenuation des ondes ultrasonores de volume mesuree selon differentes methodes." Compiègne, 1992. http://www.theses.fr/1992COMP450S.
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La premiere etape de cette etude a ete de comparer les mesures d'attenuation faites par contact direct, en immersion et avec des lignes a retard (appelees buffers) realisees dans des materiaux differents. Les resultats ont montre que la methode utilisant un buffer en verre donnait des mesures precises sur une large bande de frequences. L'etude a ensuite consiste a mesurer l'attenuation des ondes longitudinales dans les aciers en fonction de leur etat structural. Nous avons choisi un acier a tres faible teneur en carbone afin d'obtenir une structure entierement ferritique. Nous avons montre que la distribution statistique de taille de grain (dstg) etait le parametre devant etre pris en compte au niveau de l'attenuation, la dstg ayant ete determinee par traitement informatique de l'image. L'attenuation ultrasonore mesuree dans les aciers ferrito-perlitiques fait probablement appel a deux mecanismes de diffusion relatifs a chaque constituant (grain ferritique et grain perlitique). L'acier 35 ncd 16 a ete choisi pour obtenir des structures martensitiques, on se trouve alors confronte a de tres faibles niveaux d'attenuation. Les resultats n'ont pas montre que la taille de grain austenitique etait le parametre determinant au niveau de l'attenuation. Dans le cas d'aciers frittes, l'attenuation est sensible a l'influence de la taille de grain et de la porosite. L'ensemble des resultats obtenus a montre que l'attenuation ultrasonore dans les differentes structures etudiees etait la somme d'un coefficient d'absorption lineaire en frequence et d'un coefficient de diffusion proportionnel a la puissance 4 de la frequence et a la dstg
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Bounoua, Nahed Sihem. "Rhéologie et microstructure des suspensions de fibres concentrées non-browniennes." Thesis, Université Côte d'Azur (ComUE), 2016. http://www.theses.fr/2016AZUR4049/document.
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Dans ce travail, nous étudions le comportement rhéologique de suspensions concentrées de fibres non-browniennes. Dans un premier temps, nous avons élaboré de nouvelles méthodes expérimentales en géométrie torsionnelle plan-plan, pour mesurer la viscosité, les deux différences de contraintes normales, ainsi que les contraintes normales d'origine particulaire. Nous avons été en mesure d'apporter des résultats originaux qui ont été interprétés en termes d’évolution de la microstructure des suspensions de fibres. Les mesures de la viscosité en régimes stationnaire et transitoire ont permis de mettre en évidence l'importance de l'orientation et de l'effet du confinement sur la viscosité. Par ailleurs, nous avons obtenu pour la première fois des mesures indépendantes des deux différences de contraintes normales en géométrie torsionnelle plan-plan. Les mesures de la pression dans le fluide interstitiel nous ont donné accès aux contraintes normales particulaires et apporté une première mise en évidence expérimentale du phénomène de migration des fibres dans les suspensions non-browniennes. Dans un deuxième temps, nous avons établi deux modèles théoriques qui tentent d'expliquer la rhéofluidification des suspensions de fibres concentrées par une compétition entre des forces adhésives entre fibres et les forces hydrodynamiques et qui proposent un scénario de formation et de destruction d'agrégats. Les résultats de ces modèles sont alors confrontés aux mesures expérimentales et rendent bien compte du comportement de la viscosité sur une large gamme de taux de cisaillementIn this manuscript we investigate, both experimentally and theoretically, the rheological behavior of concentrated non-Brownian fiber suspensions. The experiments consist in developing new methods for measuring the viscosity, the two normal stress differences as well as the particle normal stresses, in torsional plate-plate geometry. We were able to bring original results that have been interpreted by the evolution of the microstructure of the fiber suspensions during the flow. The experiments in stationary and transient regime highlight the importance of fiber orientation and the effect of the confinement on the viscosity measurement. For the first time, the first and the second normal stress differences have been measured separately in a torsional flow. Furthermore, thanks to the measurement of the pore pressure in the suspensions, an estimation of the particle normal stresses has been carried out and, for the first time the phenomenon of fiber migration in non-Brownian suspensions has been evidenced. From a theoretical point of view, we developed two complementary models that tend to explain shear-thinning behavior in concentrated fiber suspensions by a balance between adhesive and hydrodynamic forces and propose a scenario for the formation and the destruction of aggregates. These models are then tested against experimental measurements in a wide range of shear rates
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Saied, Mahmoud. "Experimental and numerical modeling of the dissolution of delta ferrite in the Fe-Cr-Ni system : application to the austenitic stainless steels." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAI016/document.
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La ferrite résiduelle δ est présente dans les microstructures de coulée des aciers inoxydables austénitiques. Elle résulte de la transformation incomplète δ→γ ayant lieu l'étape de solidification. Sa présence peut nuire à la forgeabilité à chaud des aciers inoxydables et peut conduire à la formation de criques de rives et de pailles en J lors du laminage à chaud des brames. Ce travail de thèse a pour but de comprendre les mécanismes de la transformation δ→γ à haute température dans les aciers inoxydables austénitiques via une modélisation expérimentale et numérique. La transformation a été étudié dans un alliage ternaire Fe-Cr-Ni coulé par lingot et de composition proche de celle des alliages industriels. Trois morphologies de ferrite ont été mises en évidence à l'état brut de solidification: lattes au bord du lingot, vermiculaire et lattes au centre. Leur cinétique de dissolution est étudiée à des températures allant de 1140°C à 1340°C et caractérisée en termes de fraction de ferrite et profils de composition du Cr et du Ni. La dissolution de la ferrite vermiculaire comprend trois étapes : une croissance initiale transitoire suivie par deux régimes de dissolution à haute puis à faible taux de transformation. D'un autre côté, il a été possible d'étudier la dissolution de la ferrite dans des microstructures multicouches élaborées par l'empilement de plaques de ferrite et d'austénite du système Fe-Cr-Ni et soudées à l'état solide par Compression Isostatique à Chaud puis réduits en épaisseurs par laminages successifs. L'étude et la caractérisation de la cinétique de dissolution de la ferrite est plus facile dans ces microstructures étant donnée la planéité initiale des interfaces δ/γ. L'analyse des résultats expérimentaux a été menée via le développement d'un modèle numérique, à interface mobile, de la transformation de phases δ→γ pilotée par la diffusion. La diffusion peut être traitée dans les géométries plane, cylindrique et sphérique. En guise de validation, le modèle a été utilisé pour analyser la dissolution de la ferrite dans les microstructures multicouches. Par la suite il a été appliqué au cas de la ferrite vermiculaire en usant d'une approche novatrice où la morphologie des dendrites est approximée par une combinaison de cylindres et de sphères. Malgré la simplicité des hypothèse sous-jacentes, le modèle a permis d'expliquer les mécanismes de croissance initiale et de changement de régime de dissolution. D'autre part, via une étude paramétrique, l'effet des données d'entrée a été étudié et les plus pertinentes d'entre eux en termes de prédiction quantitative ont été mises en avant, en particulier la description thermodynamique du digramme Fe-Cr-Ni, le gradient initial et la distribution des rayons des particules de ferriteResidual δ-ferrite is widely encountered in the as-cast microstructure of austenitic stainless steels. It stems from the incomplete high temperature solid-state δ→γ transformation occurring upon the solidification stage. Its presence has a detrimental effect the hot workability of stainless steels, leading to the formation of edge cracks and sliver defects during slabs hot rolling. This PhD work aims at bringing more understanding of the kinetics of high temperature δ→γ transformation in austenitic stainless steels via experimental and numerical modeling. The transformation was studied in a ternary Fe-Cr-Ni ingot-cast alloy with composition close to the industrial alloys. Three ferrite morphologies were identified: lathy at the edge of the ingot, vermicular and lathy at the center. Their dissolution kinetics were established at temperatures ranging from 1140°C to 1340°C and characterized in terms of ferrite fraction and Cr and Ni diffusion. The vermicular ferrite undergoes a transient growth followed by a high then a low rate dissolution regimes. On the other hand, ferrite dissolution was also studied in the multilayered microstructures. such microstructures were elaborated by alternating ferrite and austenite sheets of the Fe-Cr-Ni system, diffusion-bonded by Hot isostatic Pressing and reduced in thickness by successive rollings. Dissolution is easier to handle in such microstructures thanks to the initial planar δ/γ interfaces. Analysis of the experimental results were carried out with a numerical moving-boundary model of diffusion-controlled δ→γ transformation. Diffusion can be treated in the planar, cylindrical and spherical geometries. As a preliminary validation, the model was used to analyze kinetics of ferrite dissolution in the multilayered microstructures. It was then applied to the cast alloy using an original descriptive approach combining spheres and cylinders as equivalent morphology of dendritic ferrite. Although based on simplifying assumptions, the model was able to reproduce experimental results with satisfactory agreement. Mechanisms underlying the initial growth of vermicular ferrite and the transition in dissolution regimes were outlined. The effect of a wide range of input parameters has been considered and relevant parameters for quantitative calculations were brought to light, such as thermodynamical descriptions of the Fe-Cr-Ni system, composition gradients and distribution of ferrite's radii
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Quan, Liang. "Using FDM and FEM to simulate the decarburization in AISI 1074 during heat processing and its impact." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/44769.
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The metallurgical processes and the products developed from these processes have been the cornerstone on which our civilizations have developed and flourished. Many of the new materials that have been developed over centuries were often the result of serendipitous occurrences. Because of the importance of new materials to the improvement of society, it is necessary to accelerate the way in which new alloys and processes are designed, developed and implemented.
Over the last two decades the computational side of materials science has thrived as a result of bigger and faster computers. However, the application of new computational methods to the development of new materials and structures is still in the early stages primarily because of the complexity of most metallurgical processes. One such process is the decarburization of steel. Because of the importance of the microstructure on the mechanical properties, changes in the near surface properties are affected by the loss of carbon in the alloy. The topics investigated in this thesis include a variety of alloys and microstructures that are considered to be important in the development of a unique structure necessary for a more efficient method of recovering natural gas and oil from underground reserves as well as structures for energy absorbing systems. Since both the material application and the structure are new, this research represents an ideal opportunity to combine processing, properties, microstructure and computations to accelerate the development of these new structures.
Compared to other commercially available proppants which tend to fail in demanding environments, the thin-walled hollow metal proppants are regarded more promising due to the low density and high mechanical strength. The energy-absorbing composite material manufactured by embedding said spheres in the Mg/Al matrix material is optimized by improving sphere and matrix properties at each step in the process. Ultimately the mechanical strength, fracture toughness, and energy absorption are expected to achieve a factor of 2-5 higher than previously reported.
Modeling makes it economically practical to assess the targeted materials' overall properties, behaviors and the mechanical responses in conjunction with stress environment, material properties, material dimensions among other variables, before a structure is built. Additionally, more advanced modeling can enable the quantitative descriptions of more complex metallurgical phenomena such as the effects of impurity elements and deformation under complex loading conditions.
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WISNIEWSKI, MURIEL. "Synthese de stereocopolymeres de l'acide lactique par polymerisation de lactides avec differents alcoolates metalliques. Etude de la microstructure, des proprietes thermiques et de la formation de stereocomplexes." Paris 6, 1995. http://www.theses.fr/1995PA066490.
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Des polylactides ayant des caracteristiques controlees (masses molaires, fonctionnalite) ont ete prepares par polymerisation par ouverture de cycle du lactide a l'aide d'alcoolates d'aluminium derives de bases de schiff. Une etude cinetique montre qu'en solution, les ordres en monomere et en amorceur sont egaux a un. Les reactions de transesterification apparaissent en fin de polymerisation. L'etude de la microstructure par rmn#1#3c indique que les polylactides racemiques presentent une proportion elevee de sequences isotactiques dont la composition peut etre interpretee par une statistique de markov de premier ordre. Les stereocopolymeres de lactide sont semi-cristallins quel que soit leur exces enantiomere. Des stereocomplexes sont obtenus par melange de stereocopolymeres de chiralite opposee lorsque la purete optique des deux partenaires est superieure a 20%. L'emploi d'alcoolates d'aluminium derives de bases de shiff chirales a fort encombrement sterique reduit les reactions de transesterification et conduit a une polymerisation enantioasymetrique avec un choix preferentiel tres eleve en l'un des enantiomeres
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Bombrowski, Martin. "Viskoelastisches Verhalten und Struktur konzentrierter Kaolinsuspensionen mit negativer Normalspannung." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2016. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-201880.
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In Abhängigkeit von der Suspensionszusammensetzung und der jeweiligen Scherrate können konzentrierte Kaolinsuspensionen ungewöhnliche rheologische Phänomene wie Oszillationen der scheinbaren Viskosität oder eine negative 1.~Normalspannungsdifferenz zeigen. In dieser Arbeit wurde die Abhängigkeit der 1.~Normalspannungsdifferenz, des Speicher- und des Verlustmoduls im linear-viskoelastischen Bereich sowie der Fließgrenze von der Oberflächenbeladung des Kaolins, von der Kaolinfeststoffkonzentration, vom pH-Wert und von der Ionenstärke untersucht. Weiterhin wurde eine Methode entwickelt, die die Fixierung der scherinduzierten Mikrostruktur der Suspensionen und deren anschließende Charakterisierung mittels Röntgenbeugung gestattet. Außerdem wurde ein rheologisches Modell abgeleitet, das den Zusammenhang zwischen den Aussagen zur scherinduzierten Mikrostruktur und dem Auftreten negativer 1.~Normalspannungsdifferenzen herstellt.
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Lee, Jiho. "Impact of process parameter modification on poly(3-hexylthiophene) film morphology and charge transport." Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50409.
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Organic electronics based on π-conjugated semi-conductor raises new technology, such as organic film transistors, e-paper, and organic photovoltaic cells that can be implemented cost-effectively on large-area applications. Currently, the device performance is limited by low charge carrier mobility. Poly(3-hexylthiophene) (P3HT) and organic field effect transistors (OFET) is used as a model to investigate morphology of the organic film and corresponding electronic properties. In this thesis, processing parameters such as boiling points and solubility are controlled to impact the micro- and macro-morphology of the film to enhance the charge transport of the device.
Alternative approach to improve ordering of polymer chains and increase in charge transport without post-treatment of P3HT solution is studied. The addition of high boiling good solvent to the relatively low boiling main solvent forms ordered packing of π-conjugated polymers during the deposition process. We show that addition of 1% of dichlorobenzene (DCB) to the chloroform based P3HT solution was sufficient to improve wetting and molecular structures of the film to increase carrier mobility.
Systematic study of solvent-assisted re-annealing technique, which has potential application in OFET encapsulation and fabrication of top-contact OFET, is conducted to improve mobility of OFET, and, to suggest a cost-effective processing condition suitable for industrial application. Three process parameters: boiling point, polarity, and solubility are investigated to further understand the trend of film response to the solvent-assisted technique. We report the high boiling non-polar solvents with relatively high RED values promote highest improvement in molecular packing and formulate crystalline structure of the thin film, which increases the device performance.
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Silbermann, Christian B. "Ein Beitrag zur Modellierung versetzungs- und verformungsinduzierter plastischer Lokalisierungsphänomene metallischer Werkstoffe." Universitätsverlag Chemnitz, 2019. https://monarch.qucosa.de/id/qucosa%3A35973.
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Die vorliegende Arbeit beschäftigt sich mit Festkörperkontinuumsmechanik und Metall- bzw. Kristallplastizität auf verschiedenen Längenskalen. Diesbezüglich besteht die Arbeit aus drei größeren Teilen. Im ersten Teil werden Verformungsvorgänge mit expliziter FEM (Finite-Elemente-Methode) und einem makroskopischen phänomenologischen Modell der Viskoplastizität simuliert. Hierbei wird sich auf das Gleichkanalwinkelpressen (ECAP) eines Metallbarrens und die Stauchung einer sogenannten Crashbox konzentriert. In beiden Fällen gelingt es, die im Experiment bereits beobachtete Lokalisierung der Verformung korrekt wiederzugeben. Da bei den Simulationen die konkrete Mikrostruktur des Materials vernachlässigt wird, werden diese Lokalisierungsphänomene als verformungsinduziert angesehen. Der zweite Teil beschäftigt sich mit der Erweiterung des viskoplastischen Modells, sodass mikroskopische Vorgänge der Gitterdefektstruktur des Materials berücksichtigt werden können. Dazu wird ein Modell des dynamischen Verhaltens von Versetzungspopulationen entwickelt und an das makroskopische viskoplastische Modell gekoppelt. Auf diese Weise können Aspekte der sogenannten Kornfeinung – einem komplexen Strukturbildungsprozess von Versetzungen und anderen Gitterdefekten – erfasst werden. Allerdings kann die für die makroskopischen Eigenschaften entscheidende Bildung von Subkorngrenzen auf diese Weise nicht abgebildet werden. Um dies zu erreichen, wird im dritten Teil der Arbeit eine mesoskopische Theorie der Kristallplastizität mit kontinuierlich verteilten Versetzungen verwendet und weiterentwickelt. Hierbei werden die für eine Subkornbildung wesentlichen Freiheitsgrade hinzugenommen, die Anzahl phänomenologischer Ansätze und zugehöriger Materialparameter aber so klein wie möglich gehalten. Mit dieser Kontinuumsversetzungstheorie (KVT) gelingt es, die Bildung von Subkorngrenzen bei großen plastischen Verformungen eines Kristallits zu verfolgen. Bei den impliziten FEM-Simulationen wird ebenfalls eine Lokalisierung beobachtet, allerdings in Bezug auf die Aktivität der Versetzungen in verschiedenen Gleitebenen. Dementsprechend wird dieses Lokalisierungsphänomen als versetzungsinduziert angesehen. Der Beitrag der vorliegenden Arbeit liegt zum einen in der Aufarbeitung und Gegenüberstellung unterschiedlicher methodischer Herangehensweisen zur Modellierung verformungs- und versetzungsinduzierter Lokalisierungsphänomene. Zum anderen wird eine Analyse und Vereinheitlichung der geometrisch linearen KVT nach Berdichevsky & Le vorgenommen. Wie sich dabei zeigt, verhindern inhärente kinematische Einschränkungen der Theorie die Simulation einer Subkornbildung. Aus diesem Grund wird die konsistente geometrisch nichtlineare KVT von Gurtin aufgegriffen und erweitert. Mit einem daraus abgeleiteten elastisch und plastisch anisotropen Modell der Einkristallviskoplastizität wird der Nachweis erbracht, dass die Subkornbildung damit simuliert werden kann. Darüber hinaus wird eine Aufbereitung und Synthese von Algorithmen zur numerischen Lösung der zugehörigen Feldgleichungen mittels der Methode der finiten Differenzen und der finiten Elemente geliefert. Zudem werden beide Näherungsverfahren in Bezug auf Vor- und Nachteile sowie thermodynamische Konsistenz bei der Anwendung auf Mehrfeldprobleme miteinander verglichen.The present thesis deals with solid continuum mechanics applied to metal and crystal plasticity on different length scales. In this respect, the work consists of three larger parts. In the first part, deformation processes are simulated with explicit FEM (Finite Element Method) and a macroscopic phenomenological model of viscoplasticity. Here the focus is on the Equal-Channel Angular Pressing (ECAP) of a metal billet and the compression of a so-called crash box. In both cases it is possible to correctly reproduce the localization of the deformation as already observed in the experiment. Since the concrete microstructure of the material is neglected in the simulations, these localization phenomena are regarded as deformation-induced. The second part deals with the extension of the viscoplastic model so that microscopic processes of the lattice defect structure of the material can be considered. A model of the dynamic behavior of dislocation populations is developed and coupled to the macroscopic viscoplastic model. In this way, aspects of the so-called grain refinement – a complex structure formation process of dislocations and other lattice defects – can be captured. However, the formation of subgrain boundaries, which is decisive for the macroscopic properties, cannot be predicted in this way. To achieve this, a mesoscopic theory of crystal plasticity with continuously distributed dislocations is used and further developed in the third part of the thesis. Here, the degrees of freedom essential for subgrain formation are added, while the number of phenomenological approaches and associated material parameters are kept as small as possible. With this continuum dislocation theory it is possible to follow the formation of subgrain boundaries during large plastic deformations of a crystallite. In the implicit FEM simulations, localization is also observed, but with respect to the dislocation activity in different slip planes. Accordingly, this localization phenomenon is considered dislocation-induced. The contribution of the present work lies on the one hand in the review and comparison of different methodical approaches to the modeling of deformation- and dislocation-induced localization phenomena. On the other hand, an analysis and unification of the geometrically linear continuum dislocation theory according to Berdichevsky & Le is carried out. As it turns out, inherent kinematic limitations of the theory prevent the simulation of subgrain formation. For this reason the consistent geometrically non-linear continuum dislocation theory from Gurtin is adopted and extended. With the derived model of elastically and plastically anisotropic single crystal viscoplasticity it is proven that subgrain formation can be simulated. Moreover, a preparation and synthesis of algorithms for the numerical solution of the associated field equations using the method of finite differences and finite elements is provided. In addition, both approximation methods are compared in terms of advantages and disadvantages as well as thermodynamic consistency when applied to multi-field problems.
Books on the topic "Microstructural differences"
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ZnO bao mo zhi bei ji qi guang, dian xing neng yan jiu. Shanghai Shi: Shanghai da xue chu ban she, 2010.
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Hopkins, William D., Cheryl D. Stimpson, and Chet C. Sherwood. Social cognition and brain organization in chimpanzees (Pan troglodytes) and bonobos (Pan paniscus). Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198728511.003.0014.
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Bonobos and chimpanzees are two closely relates species of the genus Pan, yet they exhibit marked differences in anatomy, behaviour and cognition. For this reason, comparative studies on social behaviour, cognition and brain organization between these two species provide important insights into evolutionary models of human origins. This chapter summarizes studies on socio-communicative competencies and social cognition in chimpanzees and bonobos from the authors’ laboratory in comparison to previous reports. Additionally, recent data on species differences and similarities in brain organization in grey matter volume and distribution is presented. Some preliminary findings on microstructural brain organization such as neuropil space and cellular distribution in key neurotransmitters and neuropeptides involved in social behaviour and cognition is presented. Though these studies are in their infancy, the findings point to potentially important differences in brain organization that may underlie bonobo and chimpanzees’ differences in social behaviour, communication and cognition. Les bonobos et les chimpanzés sont deux espèces du genus Pan prochement liées, néanmoins ils montrent des différences anatomiques, comportementales et cognitives marquées. Pour cette raison, les études comparatives sur le comportement social, la cognition et l’organisation corticale entre ces deux espèces fournissent des idées sur les modèles évolutionnaires des origines humaines. Dans ce chapitre, nous résumons des études sur les compétences socio-communicatives et la cognition sociale chez les chimpanzés et les bonobos de notre laboratoire en comparaison avec des rapports précédents. En plus, nous présentons des données récentes sur les différences et similarités d’organisation corticale du volume et distribution de la matière grise entre espèces. Nous présentons plus de résultats préliminaires sur l’organisation corticale microstructurale comme l’espace neuropile et la division cellulaire dans des neurotransmetteurs clés et les neuropeptides impliqués dans le comportement social et la cognition. Bien que ces études sont dans leur enfance, les résultats montrent des différences d’organisation corticale importantes qui sont à la base des différences de comportement social, la communication et la cognition entre les bonobos et les chimpanzés.
Book chapters on the topic "Microstructural differences"
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Tirado González, J. G., A. Esguerra-Arce, L. K. Herrera, and J. Esguerra-Arce. "Differences in Microstructural Aspects Between Die Pressing and Metal-Fused Filament Fabrication Using Powder Originating from Waste." In Sustainable Design and Manufacturing, 67–76. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-19-9205-6_7.
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Sánchez, J. M., M. A. Sebastián Pérez, J. M. González, M. S. Carrilero, and Mariano Marcos Bárcena. "Microstructural Differences of Adhered Material in the Tool Edge and Tool Rake Face. Application to the Machining of Al Alloys." In Materials Science Forum, 181–86. Stafa: Trans Tech Publications Ltd., 2005. http://dx.doi.org/10.4028/0-87849-962-8.181.
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Noji, H., and F. Furusawa. "Differences of Microstructural and Superconducting Properties of Bi-2212 Thick Films by a Variation of the Maximum Temperature During Melt-Solidification with and without Bi2Al4O9." In Advances in Superconductivity XII, 682–84. Tokyo: Springer Japan, 2000. http://dx.doi.org/10.1007/978-4-431-66877-0_204.
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Callahan, Patrick G. "Distance Measures for Quantifying the Differences in Microstructures." In Statistical Methods for Materials Science, 291–304. Boca Raton, Florida : CRC Press, [2019]: CRC Press, 2019. http://dx.doi.org/10.1201/9781315121062-21.
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Wennerström, Håkan, and David M. Anderson. "Difference Versus Gaussian Curvature Energies; Monolayer Versus Bilayer Curvature Energies; Applications to Vesicle Stability." In Statistical Thermodynamics and Differential Geometry of Microstructured Materials, 137–52. New York, NY: Springer New York, 1993. http://dx.doi.org/10.1007/978-1-4613-8324-6_11.
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Balokhonov, Ruslan R., and Varvara A. Romanova. "Microstructure-Based Computational Analysis of Deformation and Fracture in Composite and Coated Materials Across Multiple Spatial Scales." In Springer Tracts in Mechanical Engineering, 377–419. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-60124-9_17.
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AbstractA multiscale analysis is performed to investigate deformation and fracture in the aluminum-alumina composite and steel with a boride coating as an example. Model microstructure of the composite materials with irregular geometry of the matrix-particle and substrate-coating interfaces correspondent to the experimentally observed microstructure is taken into account explicitly as initial conditions of the boundary value problem that allows introducing multiple spatial scales. The problem in a plane strain formulation is solved numerically by the finite-difference method. Physically-based constitutive models are developed to describe isotropic strain hardening, strain rate and temperature effects, Luders band propagation and jerky flow, and fracture. Local regions experiencing bulk tension are found to occur during compression that control cracking of composites. Interrelated plastic strain localization in the steel substrate and aluminum matrix and crack origination and growth in the ceramic coating and particles are shown to depend on the strain rate, particle size and arrangement, as well as on the loading direction: tension or compression.
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Koseki, Toshihiko, and Toshio Araki. "Modeling of Steel Weld Microstructure Using Monte Carlo and Finite Difference Hybrid Method." In THERMEC 2006, 4002–7. Stafa: Trans Tech Publications Ltd., 2007. http://dx.doi.org/10.4028/0-87849-428-6.4002.
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Fehlberg, Maja, Kwang-Seop Kim, Knut Drewing, René Hensel, and Roland Bennewitz. "Perception of Friction in Tactile Exploration of Micro-structured Rubber Samples." In Haptics: Science, Technology, Applications, 21–29. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-06249-0_3.
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AbstractFingertip friction and the related shear of skin are key mechanical mechanisms in tactile perception, but the perception of friction itself is rarely explored except for the flat surfaces of tactile displays. We investigated the perception of friction for tactile exploration of a unique set of samples whose fabric-like surfaces are equipped with regular arrays of flexible micropillars. The measured fingertip friction increases with decreasing bending stiffness, where the latter is controlled by radius (20–75 µm) and aspect ratio of the micropillars. In forced-choice tasks, participants noticed relative differences in friction as small as 0.2, and even smaller when a sample with less than 100 µm distance between pillars is omitted from the analysis. In an affective ranking of samples upon active touch, the perception of pleasantness is anticorrelated with the measured friction. Our results offer insights towards a rational design of materials with well-controlled surface microstructure which elicit a dedicated tactile appeal.
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"Basic Understanding of Weld Corrosion." In Corrosion of Weldments, 1–12. ASM International, 2006. http://dx.doi.org/10.31399/asm.tb.cw.t51820001.
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Abstract Corrosion failures of welds can occur even when the proper base metal and filler metal have been selected, industry codes and standards have been followed, and welds have been deposited that possess full weld penetration and have proper shape and contour. This chapter describes some of the general characteristics associated with the corrosion of weldments. The role of macro- and microcompositional variations, a feature common to weldments, is emphasized in this chapter to bring out differences that need to be realized in comparing the corrosion of weldments to that of wrought materials. The discussion covers the factors influencing corrosion of weldments, microstructural features of weld microstructures, various forms of weld corrosion, and welding practice to minimize corrosion.
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Bai, Lijun, Shan Wang, and Chuanzhu Sun. "Neuroimaging and Its Application in the Diagnosis and Early Prognostication of TBI." In Neurotrauma, edited by Lijun Bai, Shan Wang, and Chuanzhu Sun, 183–88. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780190279431.003.0017.
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Traumatic brain injury (TBI) is a substantial public health problem. Differences in the progress of recovery make it a heterogeneous injury and limit effective diagnostic tools that depend on patients’ clinical manifestation. Neuroimaging methods have been widely applied in published reports, especially advanced neuroimaging techniques such as diffusion tensor imaging (DTI) and functional magnetic resonance imaging (fMRI). fMRI is a widely used diagnostic imaging method for task-related dysfunction after TBI and in the assessment of cognitive. It can measure the fluctuations that exist in human brains during either active task states or a resting state. DTI, a relatively new MRI technique that is sensitive to microstructural abnormalities shows great advantages on visualizing axonal injury and major pathology in white matter tracts following TBI. It can be a significant early indicator for TBI, providing prognostics for later injury.
Conference papers on the topic "Microstructural differences"
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Ruffer, Nicholas John, and Dave Lenk. "Machining Difficulties Due to Microstructural Differences in Grey Iron." In International Off-Highway & Powerplant Congress & Exposition. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 1999. http://dx.doi.org/10.4271/1999-01-2863.
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Sasaki, Katsuhiko, Takuji Kobayashi, and Ken-Ichi Ohguchi. "Microstructural Change of Sn/37Pb and Sn/3Ag/0.5Cu Solder Alloys Subjected to Uniaxial Ratchetting Deformation." In ASME 2007 InterPACK Conference collocated with the ASME/JSME 2007 Thermal Engineering Heat Transfer Summer Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/ipack2007-33603.
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Ratchetting deformations of solder alloys are significant deformations for the safety and reliability of solder joints of electronic packaging. In this paper, the microstructural change of the solder alloys due to the uniaxial ratchetting deformation is evaluated to clarify the effect of the microstructure on the viscous deformation of solder alloys. The microstructures are observed after the specimens are subjected to the uniaxial ratchetting deformation during several cycle numbers. The change of the size of grains or lamella structures is used to evaluate the uniaxial ratchetting deformation of solder alloys. The observation clarifies that the differences in the microstructural change due to the uniaxial ratchetting deformation between the lead-free and lead-containing solder alloys. The uniaxial ratchetting deformation and the additional creep deformation after the ratchetting deformation is also simulated by the dislocation based constitutive model. The simulation suggests that the material parameters used in the constitutive model may be correlated to the microstructural change of the solder alloys.
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Hage, Ilige S., and Ramsey F. Hamade. "Toward quantifying geometric microstructural differences between primary and secondary osteons via segmentation." In 2014 Middle East Conference on Biomedical Engineering (MECBME). IEEE, 2014. http://dx.doi.org/10.1109/mecbme.2014.6783281.
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Deshpande, S., S. Sampath, P. I. Gouma, and H. Herman. "Microstructural Characterization Across Length Scales of Thermal Sprayed Ni-5wt%Al Coatings." In ITSC2003, edited by Basil R. Marple and Christian Moreau. ASM International, 2003. http://dx.doi.org/10.31399/asm.cp.itsc2003p1419.
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Abstract Thermal spray processing involves a multitude of interdependent process variables resulting in a complex layered microstructure with each layer composed of several splats separated by splat-splat interfaces. Each splat contains columnar/equiaxed grains with multiple orientations. A typical microstructure also contains defects such as globular pores, and interlamellar pores. This gamut of features encompasses a range of macro, micro and nano length scales. This study involves a thorough microstructural characterization across length scales of Ni-5wt%Al coatings to understand the dependence of microstructural variability on processing conditions and its profound influence on coating properties. Studied here are coatings produced by four different spray methods, namely twin wire-arc, air plasma, high velocity oxyfuel and cold spraying with distinct variations w.r.t. nature of feedstock, method of material injection, amount of melting, and process parameters such as particle velocity and temperature in flight. Macro-scale, Micro-scale and Nanoscale microstructural characterization of these Ni5Al coatings elucidates the variations in oxide content, splat structure, grain structure and phases obtained, based on differences in processing parameters. Through characterization of these bond-coats, using Optical microscopy, Image analysis, Scanning and Transmission electron microscopy techniques, variations in coating properties such as porosity and thermal conductivity can be explained with respect to coating microstructure and process characteristics.
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Zoeller, Tracie L., and Thomas H. Sanders. "The Effect of Thermal Treatment on the Microstructural Evolution of an Al-Cu Alloy." In ASME 2003 Heat Transfer Summer Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/ht2003-47149.
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Following solidification, an aluminum alloy microstructure is highly segregated. The microstructure consists of cored dendrites with various soluble and insoluble phases present in the dendritic regions. The solidification rate has a marked effect on the amount of coring that an alloy experiences. Understanding the effects of the solidification rate is important in explaining differences in microstructures. Subsequent heat treatments are performed to homogenize the microstructure. The microstructure evolution after each processing step is dependent upon the previous microstructures. The variation in local chemical composition may promote or hinder precipitation of new phases. A large volume fraction of coarse insoluble phases can lead to the occurrence of recrystallized grains via particle stimulated nucleation, while inhomogeneous solute distribution can lead to the precipitation of an uneven distribution of dispersoid phases. The effect of solidification rate and subsequent thermal treatments on the microstructure of an Al-4Cu alloy will be investigated and experimental and numerical results will be presented.
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Chowdhury, Md Mahmudur R., Mohd Aminul Hoque, Jeffrey C. Suhling, Sa’d Hamasha, and Pradeep Lall. "Evolution of the Microstructure of Lead Free Solders Subjected to Both Aging and Cyclic Loading." In ASME 2019 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/ipack2019-6560.
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Abstract Currently, lead-free solders are being widely used as an alternative to traditional Sn-Pb solders in micro-electronic packaging industry due to the environmental concern of lead. Fatigue failure of solder joints is one of the common failure modes in electronic packaging which might be attributed to the experiences of thermo-mechanical fatigue (e.g. Power switching) or mechanical fatigue (e.g. vibration) loading. To design these lead-free solders more strategically for specific applications, it is important to understand the failure mechanism of lead-free solders under fatigue loading. Moreover, the microstructure and constitutive properties of conventional lead free solder joints in electronic assemblies such as SAC305 changes when exposed to isothermal aging. These changes consequently reduce the reliability of lead free electronic assemblies significantly due to aging. In this study, we have examined the effects of prior aging on damage accumulation occurring in SAC305 and SAC_Q (SAC+Bi) solder materials subjected to mechanical cycling (fatigue testing). Uniaxial samples have been prepared and polished so that the microstructural changes could be tracked after the initial aging, and then subsequently with mechanical cycling. In particular, we have examined the microstructural changes that occurred in small fixed regions in the solder samples, rather than using several different regions. Regions of interest near the center of the sample were marked using small indents formed with a nanoindentation system. Samples were then subjected to aging at 125 °C for various durations to produce several different initial microstructures. Scanning electron microscopy (SEM) were used to investigate the aging induced microstructural changes in the regions of interest in the solder sample. After aging, the samples were then subjected to mechanical cycling. After various durations of cycling (e.g. 0, 10, 25, 50, 75, 100, 200, 300 cycles) that were below the fatigue life of the materials, the regions of interest were again examined using SEM. Using the recorded images, the microstructural evolutions in the fixed regions were observed, and the effects of the initial aging on the results were determined. In case of SAC305, It was found that the number of IMC particles decreased while the average diameter of the particles increases significantly due to the initial aging. The distribution and size of the intermetallic particles in the inter-dendritic regions were observed to remain essentially unchanged with the application of the mechanical cyclic load. Relative to the non-aged samples, there were significant differences observed in the rate and intensity of the micro crack growth occurring in the heavily aged samples that began with much coarser microstructures. Later, the cycling induced microstructure evolutions observed in the SAC_Q lead free alloy has been compared with the observed changes in the microstructure of SAC305 that occurred during the cyclic loading. Due to the presence of bismuth, significant difference in the microstructural evolution of the SAC_Q alloy during cycling were observed. Thus, the doped alloys have shown a high potential for use in thermal cycling conditions because of their improved resistance to aging-induced evolution.
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Wan, William, and Rudolph L. Gleason. "Collagen Fiber Angle Quantification of Carotid Arteries From Fibulin-5 Null Mice." In ASME 2011 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2011. http://dx.doi.org/10.1115/sbc2011-53685.
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Recent studies have revealed that carotid arteries from fibulin-5 (fbln5) null mice exhibit altered biomechanical and microstructural properties [1–2]. While the previous studies outline quantitative differences in mechanical properties of arteries from fbln5 null and wildtype mice, physical microstructural differences have yet to be quantified. Measurement of microstructural parameters will provide a crucial link between previously quantified mechanical properties and biological effects of knocking out the fbln5 gene. Characterizing microstructural properties will also provide experimental data to validate structurally-motivated constitutive relations and growth and remodeling models [3–4]. In this study, we quantified collagen fiber orientation in carotid arteries from fbln5 null and wildtype mice; collagen in mouse carotid arteries were imaged using multiphoton microscopy and analyzed using a fast Fourier transform algorithm.
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Chen, H. C., E. Pfender, B. Dzur, and G. Nutsch. "Microstructural Comparison of Alumina Coatings Prepared by RF and DC Plasma Spraying." In ITSC 1999, edited by E. Lugscheider and P. A. Kammer. Verlag für Schweißen und verwandte Verfahren DVS-Verlag GmbH, 1999. http://dx.doi.org/10.31399/asm.cp.itsc1999p0603.
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Abstract DC plasma spraying has been widely recognized as a quick and economic way to produce all kinds of coatings (metals, alloys, and ceramics) for a variety of applications. There has been a growing interest in using radio frequency (RF) plasmas. Studies have been reported on characterization of plasma-sprayed coatings by TEM, including thermal barrier coatings, alumina coatings, and Ni-Al coatings. There are, however, no detailed studies reported on microstructural comparisons of coatings prepared by RF and DC plasma spraying. In this paper, XRD, SEM, TEM, polarizing OM, four-point bending fracture, and molten particle impact behavior are used to clarify microstructural differences between the RF- and DC-coatings. The results showed that the microstructures were much different for both cases, especially in the interfacial region between the coatings and the substrates. Paper includes a German-language abstract.
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Toma, F. L., G. Bertrand, R. Rampon, D. Klein, and C. Coddet. "Relationship Between the Suspension Properties and Liquid Plasma Sprayed Coating Characteristics." In ITSC2006, edited by B. R. Marple, M. M. Hyland, Y. C. Lau, R. S. Lima, and J. Voyer. ASM International, 2006. http://dx.doi.org/10.31399/asm.cp.itsc2006p0697.
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Abstract The suspension plasma spraying using a liquid as material feedstock is a promising technique to elaborate thin and nanostructured coatings. This work deals with the study of suspensions in order to obtain specific microstructural coatings. The slurries were prepared starting from nanosized titania powders. Distilled water and alcohol were used as solvents and appropriate dispersing agents were employed to stabilize the suspensions. An external injection system that ensures the atomisation and radial injection of the suspension into Ar-H2 plasma under atmospheric conditions was designed. The coatings were characterized by scanning electron microscopy and differences in the microstructure of the deposits were observed. Efforts were made to understand the relationship between liquid feedstock properties, injection/plasma parameters and coatings microstructural characteristics.
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Li, Ming, Vimal H. Desai, and N. Sastry Cheruvu. "The Effect of Microstructural Differences on NA2SO4-Induced Corrosion of Superalloy CMSX-4 at High Temperatures." In ASME 1997 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/97-gt-424.
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Single crystal (SC) nickel based superalloys have been used in aero engine applications for a long time. The SC casting techniques are not yet widely used in the land based engine components because of their much larger size which makes casting and the subsequent heat treatment more difficult. In large casting, microporosity and elemental segregation are more severe. The γ/γ′ eutectic structure and dendritic arm spacing are also larger due to large casting size. All these defects will affect the heat treatment process and the subsequent service properties, including the resistance to oxidation and hot corrosion. In this work, as-cast and heat treated CMSX-4 specimens from small and large blades were used to study the effects of cast defects and heat treatment on Na2SO4 -induced hot corrosion resistance of the single crystal superalloy. The tests were carried out between 900 to 1000°C, for times ranging than 10 to 600 hours in the presence of a Na2SO4 deposit. The specimens from as-cast large blade underwent catastrophic attack after a short exposure time. But the initiation time for catastrophic attack approximately doubled in the case of wholly solution heat treated specimens. It is thus likely that although the hot corrosion resistance of this single crystal material is not as good as that of IN738, proper heat treatment can improve its hot corrosion resistance.
Reports on the topic "Microstructural differences"
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Kiv, A. E., T. I. Maximova, and V. N. Soloviev. Microstructure of the relaxed (001) Si surface. [б. в.], December 1999. http://dx.doi.org/10.31812/0564/1245.
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We have applied molecular dynamics method and semi-empirical potential [1] to obtain the realistic picture of Si surface layers relaxation.The starting configuration was taken as a parallelepiped containing 864 atoms. There were 12 layers with 72 atoms in each one. Periodic boundary conditions were used in two dimensions. At first all atoms were in normal lattice positions. The relaxation of Si surface, which corresponds to (001) plane was investigated. MD method was applied in its standard form i.e. the equations of motion were solved by using of the central difference scheme. The time-step was 10-14s.