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Letteratura scientifica selezionata sul tema "Compositionally graded materials"

Autore: Grafiati

Pubblicato: 14 settembre 2024

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Articoli di riviste sul tema "Compositionally graded materials"

Coco, Lorenzo, Florent Lefevre-Schlick, Olivier Bouaziz, Xiang Wang, J. K. Solberg e David Embury. "The mechanical response of compositionally graded materials". Materials Science and Engineering: A 483-484 (giugno 2008): 266–69. http://dx.doi.org/10.1016/j.msea.2006.12.164.

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Torrecillas, R. "Compositionally graded zirconia-molybdenum materials without residual stress". Metal Powder Report 57, n. 6 (giugno 2002): 54. http://dx.doi.org/10.1016/s0026-0657(02)80261-2.

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Zhong, S., S. P. Alpay, Z. G. Ban e J. V. Mantese. "Effective pyroelectric response of compositionally graded ferroelectric materials". Applied Physics Letters 86, n. 9 (28 febbraio 2005): 092903. http://dx.doi.org/10.1063/1.1866505.

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ChÃ©hab, BÃ©chir, Hatem Zurob, David Embury, Olivier Bouaziz e Yves Brechet. "Compositionally Graded Steels: A Strategy for Materials Development". Advanced Engineering Materials 11, n. 12 (dicembre 2009): 992–99. http://dx.doi.org/10.1002/adem.200900180.

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Popa, Monica, José-Maria Calderón Moreno, Pavol Hvizdoš, Raúl Bermejo e Guy Anné. "Residual Stress Profile Determined by Piezo-Spectroscopy in Alumina/Alumina-Zirconia Layers Separated by a Compositionally Graded Intermediate Layer". Key Engineering Materials 290 (luglio 2005): 328–31. http://dx.doi.org/10.4028/www.scientific.net/kem.290.328.

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In order to understand the mechanical behavior of layered composites with compositional gradient, it is necessary to determine their state of residual stresses. Compositionally graded materials can offer the advantage of eliminating abrupt changes in composition between layers having different thermal expansion coefficients. The existence of a compositional gradient may reduce discontinuities in thermal residual stresses, something beneficial from the point of view of the mechanical properties. We present here a study of the state of the residual stresses in a layered material made of thicker (several mm) homogeneous layers of alumina and alumina-20%zirconia separated by a thinner (less than 300 µm) intermediate graded alumina-zirconia layer, obtained by controlled deposition of powders from a solution using an electrophoretic deposition method. The thermal residual stresses generated during cooling after sintering were measured in the homogeneous layers at each side, and at steps of about 30 µm in the graded layer along the direction of the compositional gradient, by using fluorescence ruby luminescence piezo-spectroscopy. Results show that the hydrostatic stresses on alumina grains vary continuously, indicating the absence of discontinuities in thermal residual stresses along the compositionally graded layer and at the interfaces of the homogeneous layers.

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Wu, Jiagang, John Wang, Dingquan Xiao e Jianguo Zhu. "Compositionally graded bismuth ferrite thin films". Journal of Alloys and Compounds 509, n. 35 (settembre 2011): L319—L323. http://dx.doi.org/10.1016/j.jallcom.2011.05.076.

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Suresh, S., A. E. Giannakopoulos e J. Alcalá. "Spherical indentation of compositionally graded materials: Theory and experiments". Acta Materialia 45, n. 4 (aprile 1997): 1307–21. http://dx.doi.org/10.1016/s1359-6454(96)00291-1.

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Peka, H. P., D. A. Pulemyotov e M. P. Verkhovodov. "Compositionally graded semiconductors with intervalley crossover". Semiconductor Science and Technology 8, n. 8 (1 agosto 1993): 1517–22. http://dx.doi.org/10.1088/0268-1242/8/8/006.

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Kim, Yeon-Wook, Tae-Hyun Nam e Seong-Min Lee. "Martensitic Transformation Behaviors of Compositionally Graded Ti–Ni-Based Shape Memory Alloys". Science of Advanced Materials 12, n. 10 (1 ottobre 2020): 1586–90. http://dx.doi.org/10.1166/sam.2020.3802.

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In this study, we demonstrate a simple and effective way to fabricate functionally graded TiNi-based alloys with linear variations of composition and martensitic transformation behavior. Ti50Ni50 and Ti50Ni35Cu15 alloy strips were fabricated through a melt overflow process. The compositionally graded diffusion couple was fabricated by annealing two strips of different alloy compositions after being placed face to face in a pressing graphite mold. The mechanical properties and martensitic transformation behaviour of the diffusion couple were analysed by tensile test and DSC. The compositionally graded specimens exhibited unique superelastic property and wide martensitic formation temperature range. Such mechanical and thermal behaviors of the compositionally graded TiNi-based alloy offer good function and controllability for actuators.

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Klic, A., e M. Marvan. "Pseudo-spin model of compositionally graded ferroelectrics". Phase Transitions 79, n. 6-7 (giugno 2006): 493–503. http://dx.doi.org/10.1080/01411590600892377.

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Tesi sul tema "Compositionally graded materials"

Jandl, Adam Christopher. "III-V compositionally graded buffers for heterostructure integration". Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98164.

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Thesis: Ph. D. in Electronic, Photonic, and Magnetic Materials, Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2015.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 120-125).
InyGa₁-yAs alloys are critical in commercial applications such as high speed transistors, light emitting diodes, solid state lasers, photovoltaics, and photo-detectors. However, the range of compositions used in these applications is often limited to the range of InyGa₁-yAs compositions which are lattice matched to elementary or binary semiconductor substrates. Additionally, the integration of InyGa₁-yAs based devices on silicon substrates has been limited by complicated processing procedures. In order to resolve these issues we developed two compositionally graded buffer systems to integrate InyGa₁-yAs devices on InP and Si substrates. The development of InyGa₁-yAs devices on Si substrates also used the direct growth of Ge on Si offcut substrates. InAsxP₁-x compositionally graded buffers were investigated for the growth of InyGa₁-yAs compositions with lattice constants greater than InP. We report the effects of strain gradient, growth temperature, and strain initiation sequence (gradual or abrupt strain introduction) on threading dislocation density, surface roughness, epi-layer relaxation, and tilt. We find that gradual introduction of strain causes increased dislocation densities (>10⁶ cm-²) and tilt of the epi-layer (> 0.10°). A method of abrupt strain initiation is proposed which can result in dislocation densities as low as 1.0x10⁵ cm-² for films graded from the InP lattice constant to InAs₀.₁₅P₀.₈₅. A model for a two-energy level dislocation nucleation system is proposed based on our results. We demonstrate a method for the growth of InyGa₁-yAs devices on Si substrates in a single process run. Two epitaxial layers were used to change the lattice constant from the Si substrate to the InyGa₁-yAs lattice constant. The first layer was a Ge layer grown directly on Si. To reduce the threading dislocation density to < 10⁸ cm-² we investigated the most efficient thermal cycle annealing procedure. The second layer was an InvAl₁-v,As compositionally graded buffer. In₀.₃Ga₀.₇As quantum well devices grown on InvAl₁-v,As/Ge/Si virtual substrates had threading dislocation density of 2x 10' cm-², mobility of 6400 cm2/Vs, and sheet carrier concentration of 1.1x 10¹² cm-²
by Adam Christopher Jandl.
Ph. D. in Electronic, Photonic, and Magnetic Materials

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Goh, Johnathan Jian Ming. "Commercialization potential of compositionally graded Ge - Si₁₋x̳Gex̳ - Si substrates for solar applications". Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/38550.

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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2006.
In title on t.p., double-underscored "x" appears as subscript.
Includes bibliographical references.
This project considers the potential of Ge - Si₁₋x̳Gex̳ - Si substrates for solar applications. The use of compositionally graded substrates to achieve heterointegration across different materials platforms such as Si, Ge and GaAs has proven successful and dual junction solar cells have been fabricated on such substrates. The potential for graded substrates in the solar market is discussed considering the current technology, market players and worldwide renewable energy policies. A cost model is also developed and analyzed in the course of writing to assess the feasibility of this commercial enterprise. The result of these analyses highlights the technical and commercial viability of graded substrates in the solar market.
by Johnathan Jian Ming Goh.
M.Eng.

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Curnis, Agathe. "Évolution métallurgique et corrosion à haute température de matériaux à gradient de composition élaborés par procédé Laser Metal Deposition - powder". Electronic Thesis or Diss., Bourgogne Franche-Comté, 2024. http://www.theses.fr/2024UBFCK018.

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Les matériaux à gradient de composition présentent de nombreux avantages et notamment celui d’adapter localement le matériau en fonction de la sollicitation perçue par la pièce tout en limitant les risques d’incompatibilités entre les matériaux. Ce travail de thèse s’est concentré sur la réalisation d’un système de matériaux à gradient de composition par procédé Laser Metal Deposition-powder à partir d’un substrat en acier faiblement allié jusqu’à un alliage 625. Ce système multi-matériaux devant présenter une bonne tenue à la corrosion à haute température, son comportement à 800 et 650°C sous air de laboratoire, en absence ou en présence d’espèces chlorées, a été étudié.La caractérisation du système à gradient, dans un état brut de fabrication a révélé différentes microstructures et phases en présence dans les différentes régions du gradient. Lors de vieillissements à 800°C, des évolutions métallurgiques ont été mises en avant, notamment au niveau de l’alliage 625, avec la précipitation de la phase δ.La résistance à l’oxydation du système a été étudiée sous air de laboratoire à 800°C jusqu’à 2 500 h. Une cinétique parabolique liée à la formation de couches protectrices de chromine a été mise en avant. La présence d’un dépôt de NaCl accélère de manière catastrophique la dégradation de l’alliage 625. Dans ce cas, les couches de produits de corrosion sont très épaisses, très fissurées ou écaillées, composées majoritairement de NiO, Cr2O3 et d’oxydes de type spinelle Ni-Cr-Fe. La région de métal située à l’interface avec la couche d’oxyde est fortement endommagée, notamment par la formation d’un réseau de pores interconnectés permettant la diffusion rapide des espèces chlorées dans le cadre du mécanisme d’oxydation active se produisant dans ces conditions. En comparaison, à 650°C, la dégradation du matériau en présence du dépôt solide de NaCl est nettement ralentie, les couches de produits de corrosion sont moins épaisses et le substrat métallique très peu endommagé. Les différences de comportements entre les deux températures peuvent être comprises à travers des différences microstructurales et de volatilité de chlorures métalliques
Compositionally graded materials offer numerous advantages, including the ability to locally adjust the material composition to adapt it to service conditions while minimizing the risks of incompatibilities between materials. This thesis work focused on the development of a compositionally graded material system using the Laser Metal Deposition-powder process, starting from a low-alloy steel substrate to alloy 625. As this multi-material system is expected to exhibit good high-temperature corrosion resistance, its behavior in an air atmosphere at 800°C and 650°C, with and without a NaCl solid deposit, was studied.Characterization of the as-built compositionally gradient system revealed various microstructures and phases depending on the regions of the gradient. Metallurgical evolutions were highlighted during aging at 800°C, particularly in alloy 625 with the precipitation of the δ phase.The oxidation resistance of the system was studied in an air atmosphere at 800°C for up to 2 500 h. Parabolic kinetics related to the formation of a protective Cr2O3 layer were highlighted. The presence of a NaCl deposit catastrophically accelerated the degradation of alloy 625. In this case, the corrosion scale was thick, highly cracked or spalled and mainly composed of NiO, Cr2O3, and (Ni,Cr,Fe)3O4. The metal region at the interface with the oxide layer was severely damaged, especially by the formation of an interconnected voids network allowing the rapid diffusion of chlorinated species in the active oxidation mechanism occurring under these conditions. In comparison, at 650°C, material degradation with a NaCl deposit was significantly slowed, with a thinner corrosion scale, and a less damaged substrate. Differences in behavior between the two temperatures can be understood through differences in microstructural characteristics and the volatility of metal chlorides."

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Thomas, Jonova. "Microstructural Phase Evolution In Laser Deposited Compositionally Graded Titanium Chromium Alloys". Thesis, University of North Texas, 2016. https://digital.library.unt.edu/ark:/67531/metadc849610/.

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A compositionally graded Ti-xCr (10≤x≤30 wt%) alloy has been fabricated using Laser Engineered Net Shaping (LENSTM) to study the microstructural phase evolution along a compositional gradient in both as-deposited and heat treated conditions (1000°C followed by furnace cooling or air cooling). The alloys were characterized by SEM BSE imaging, XRD, EBSD, TEM and micro-hardness measurements to determine processing-structure-property relations. For the as-deposited alloy, α-Ti, β-Ti, and TiCr2 (C15 Laves) phases exist in varying phase fractions, which were influential in determining hardness values. With the furnace cooled alloy, there was more homogeneous nucleation of α phase throughout the sample with a larger phase fraction of TiCr2 resulting in increased hardness values. When compared to the air cooled alloy, there was absence of wide scale nucleation of α phase and formation of ω phase within the β phase due to the quicker cooling from elevated temperature. At lower concentrations of Cr, the kinetics resulted in a diffusionless phase transformation of ω phase with increased hardness and a lower phase fraction of TiCr2. In contrast at higher Cr concentrations, α phase separation reaction occurs where the β phase is spinodally decomposed to Cr solute-lean β1 and solute-rich β2 resulting in reduced hardness.

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Daugherty, Timothy J. "Assessment of the ballistic performance of compositional and mesostructural functionally graded materials produced by additive manufacturing". Youngstown State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1596474811965998.

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Ramirez, Cadavid David A. "Development of Processes for the Extraction of Industrial Grade Rubber and Co-Products from the Roots of Taraxacum kok-saghyz (TK)". The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1512060296142347.

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Capitoli di libri sul tema "Compositionally graded materials"

Watanabe, Yoshimi, Shin Oike e Ick Soo Kim. "Formation of Compositional Gradient during Fabrication of FGMs by a Centrifugal In Situ Method". In Functionally Graded Materials VIII, 693–98. Stafa: Trans Tech Publications Ltd., 2005. http://dx.doi.org/10.4028/0-87849-970-9.693.

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Nakano, J., K. Fujii e R. Yamada. "Thermal diffusivity measurement for SiC/C compositionally graded graphite materials". In Functionally Graded Materials 1996, 439–44. Elsevier, 1997. http://dx.doi.org/10.1016/b978-044482548-3/50072-x.

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"3. Advanced manufacturing of compositionally graded composite materials: An overview". In Hierarchical Composite Materials, 41–54. De Gruyter, 2018. http://dx.doi.org/10.1515/9783110545104-003.

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Joseph, Jithin. "Direct Laser Fabrication of Compositionally Complex Materials". In Advances in Civil and Industrial Engineering, 147–63. IGI Global, 2020. http://dx.doi.org/10.4018/978-1-7998-4054-1.ch008.

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Additive manufacturing (AM) opens up the possibility of a direct build-up of components with sophisticated internal features or overhangs that are difficult to manufacture by a single conventional method. As a cost-efficient, tool-free, and digital approach to manufacturing components with complex geometries, AM of metals offers many critical benefits to various sectors such as aerospace, medical, automotive, and energy compared to conventional manufacturing processes. Direct laser fabrication (DLF) uses pre-alloyed powder mix or in-situ alloying of the elemental powders for metal additive manufacturing with excellent chemical homogeneity. It, therefore, shows great promise to enable the production of complex engineering components. This technique allows the highest build rates of the AM techniques with no restrictions on deposit size/shape and the fabrication of graded and hybrid materials by simultaneously feeding different filler materials. The advantages and disadvantages of DLF on the fabrication of compositionally complex metallic alloys are discussed in the chapter.

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Pettermann, H. E., E. Weissenbek e S. Suresh. "Simulation of the Elasto–Plastic Deformations in Compositionally Graded Metal–Ceramic Structures: Mean–Field and Unit Cell Approaches**This work was supported by the Grant DE-FG02-93ER45506 to MIT from the US Department of Energy. The post–doctoral study of EW at MIT was supported by an Erwin Schrödinger Fellowship from the AUSTRIAN NATIONAL SCIENCE FOUNDATION. HP’s visit to MIT was supported by a scholarship for Overseas Scientific Study from the AUSTRIAN FEDERAL MINISTRY OF SCIENCE, TRANSPORT AND ART." In Functionally Graded Materials 1996, 75–80. Elsevier, 1997. http://dx.doi.org/10.1016/b978-044482548-3/50014-7.

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Pakseresht, Amir Hossein, M. R. Rahimipour, M. Alizadeh, S. M. M. Hadavi e A. Shahbazkhan. "Concept of Advanced Thermal Barrier Functional Coatings in High Temperature Engineering Components". In Research Perspectives on Functional Micro- and Nanoscale Coatings, 396–419. IGI Global, 2016. http://dx.doi.org/10.4018/978-1-5225-0066-7.ch015.

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In conventional thermal barrier coatings (TBCs) the major problem is the spalling of a ceramic coating. This could be due to the large thermal stresses which are generated during thermal cycling on the oxidizing environment. One of the ways to improve the life span and overcome mentioned problems is introducing the concept of functionally graded materials (FGM) into the TBC. Functionally graded materials are referred to as a class of advanced materials that are distinguished by variation in their properties with varying their dimensions. Through employing a functionally graded thermal barrier coating (FG-TBC), an intermediate layer with a gradual compositional variation is embedded between the top and the bond coats. This layer(s), composed of ceramic and metal in various ratios, can achieve a gradual composition variation, thereby leading to gradual changes in microstructures and better mechanical and physical properties.

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Fracchia, Elisa, e Mario Rosso. "Development and Characterization of New Functionally Graded Aluminium Alloys". In Aluminium Alloys - Design and Development of Innovative Alloys, Manufacturing Processes and Applications [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.101022.

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Nowadays, aluminium alloys are adopted mainly to produce engineering and automotive components. The present investigation aims to design, cast and characterize novel functionally graded materials (FGMs) produced using Al-Mg and Al-Si alloys by gravity casting technique. Alloys were sequentially cast into a mould to obtain an FGM to realizing great mechanical and metallurgical bonding. Zn addition was further performed in FGM to increase the mechanical properties, thanks to the nucleation of the intermetallic phases MgZn2. Castings were subsequently mechanically tested by tensile tests, bending tests, hardness and microhardness measures to assess the products\' quality. Microstructural characterizations were performed along the FGM to assess the metallurgical bonding and evaluate the microstructures obtained. Fracture, microstructural and compositional analysis will highlight the quality of this new FGM proposed. Possible applications of these materials are suggested, as automotive pistons or structural components.

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Fan, Xuefei, Xu Chu, Wentao Cao e Yi Zou. "Local rapid exhumation during the long-lived Grenville orogeny". In Laurentia: Turning Points in the Evolution of a Continent. Geological Society of America, 2022. http://dx.doi.org/10.1130/2022.1220(18).

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ABSTRACT The Grenville Province is the largest and most structurally complex orogenic belt that formed in the Mesoproterozoic, representing the amalgamation of the supercontinent Rodinia. The Mattawa domain, part of the Algonquin domain in Ontario, Canada, hosts some of the most deeply buried metamorphic rocks of this orogen. This high-grade metamorphic terrane consists of large areas of felsic orthogneiss and kilometer-sized mafic boudins. Dark-colored metabasite cropping out near Mattawa, Ontario, Canada, contains relict mineral assemblages and decompression textures indicative of high-pressure eclogite. Garnet porphyroblasts surrounded by plagioclase coronae are hosted in fine-grained symplectic intergrowths of diopside + plagioclase ± amphibole, which compositionally reintegrated into an omphacite composition (Na/[Na + Ca] ~0.5). Phase equilibria analysis revealed an eclogite-facies peak pressure of ~2 GPa at 850 °C. This temperature is consistent with the zirconium contents of rutile inclusions in garnet (up to 1725 ppm Zr). Despite high-temperature metamorphism, garnet growth zonation is partially preserved. Diffusion modeling of representative garnet profiles yielded a time scale of <0.1 m.y. for decompression from the peak pressure to ~1.2 GPa, suggesting an average exhumation rate of several decimeters per year. Decompression was followed by fast cooling within hundreds of thousands of years. Such fast decompression and cooling rates contrast with the protracted metamorphic evolution recorded in most of the Grenville orogen and likely resulted from local extrusion of lower-crustal material in response to localized extension during the early Ottawan stage. Since very few examples of Precambrian short-duration regional metamorphism have been documented, the fast decompression documented in this study provides valuable constraints for the geodynamic transition to a modern plate-tectonic regime.

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Atti di convegni sul tema "Compositionally graded materials"

Lin, Xin, Mocong Yang, Xiaojing Xu, Haiou Yang, Jing Chen e Weidong Huang. "Phase evolution in laser solid formed compositionally graded Ti60-Ti2AlNb alloys". In ICALEO® 2009: 28th International Congress on Laser Materials Processing, Laser Microprocessing and Nanomanufacturing. Laser Institute of America, 2009. http://dx.doi.org/10.2351/1.5061597.

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Jovanova, Jovana, Mary Frecker, Reginald F. Hamilton e Todd A. Palmer. "Target Shape Optimization of Functionally Graded Shape Memory Alloy Compliant Mechanism". In ASME 2016 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/smasis2016-9070.

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Nickel Titanium (NiTi) shape memory alloys (SMAs) exhibit shape memory and/or superelastic properties, enabling them to demonstrate multifunctionality by engineering microstructural and compositional gradients at selected locations. This paper focuses on the design optimization of NiTi compliant mechanisms resulting in single-piece structures with functionally graded properties, based on user-defined target shape matching approach. The compositionally graded zones within the structures will exhibit an on demand superelastic effect (SE) response, exploiting the tailored mechanical behavior of the structure. The functional grading has been approximated by allowing the geometry and the superelastic properties of each zone to vary. The superelastic phenomenon has been taken into consideration using a standard nonlinear SMA material model, focusing only on 2 regions of interest: the linear region of higher Young’s modulus of elasticity and the superelastic region with significantly lower Young’s modulus of elasticity. Due to an outside load, the graded zones reach the critical stress at different stages based on their composition, position and geometry, allowing the structure morphing. This concept has been used to optimize the structures’ geometry and mechanical properties to match a user-defined target shape structure. A multi-objective evolutionary algorithm (NSGA II - Non-dominated Sorting Genetic Algorithm) for constrained optimization of the structure’s mechanical properties and geometry has been developed and implemented.

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Jovanova, Jovana, Simona Domazetovska e Mary Frecker. "Modeling of the Interface of Functionally Graded Superelastic Zones in Compliant Deployable Structures". In ASME 2018 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/smasis2018-8176.

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Functionally graded compliant mechanisms can be fabricated with additive manufacturing technology by engineering the microstructural and compositional gradients at selected locations resulting in compositionally graded zones of higher and lower flexibility. The local compliance depends on the geometry of the structure as well as the material property in the selected region. As Nitinol (NiTi) is well suited for applications requiring compliance, the critical transformation stress and the superelastic modulus of elasticity are crucial parameters for defining the local compliance. To understand the behavior at the interface between two different material compositions, three models of gradient change between the alloys are analyzed: step change, linear and polynomial gradients. In addition to localize the deformation in the interface, three different flexure designs in the interface are analyzed. This paper will address a methodology for modeling and parametrization of material properties and transition at the interface, for different flexure designs. The combined effort in the interface of the functional grading and the geometry will be used for the design of monolithic self-deployable structures, initially folded in compact shape. The design motivation comes from the self-deploying mechanisms inspired by insects’ wings.

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Kurishima, K., H. Nakajima, S. Yamahata, T. Kobayashi e Y. Matsuoka. "Effects of a Compositionally Graded InxGa1-xAs Base in Abrupt-Emitter InP/InGaAs HBTs". In 1994 International Conference on Solid State Devices and Materials. The Japan Society of Applied Physics, 1994. http://dx.doi.org/10.7567/ssdm.1994.c-6-1.

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Ou, Hao, Jiang Pu, Tomoyuki Yamada, Naoki Wada, Hibiki Naito, Zheng Liu, Toshifumi Irisawa, Yusuke Nakanishi, Yasumitsu Miyata e Taishi Takenobu. "Continuous Color-Tunable Light-Emitting Devices Based on Compositionally Graded Monolayer Transition Metal Dichalcogenide Alloys". In 2022 International Conference on Solid State Devices and Materials. The Japan Society of Applied Physics, 2022. http://dx.doi.org/10.7567/ssdm.2022.h-5-02.

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Allen, Marshall, Raymundo Arroyave e Richard Malak. "Deep Ensembles for Modeling Uncertain Phase Constraints In Compositionally Graded Alloy Design". In ASME 2022 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/detc2022-89091.

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Abstract Compositionally graded alloys (CGAs) are a specific class of multi-material functionally graded materials (FGMs) that use spatial variations in alloy composition to meet competing performance requirements in at different locations regions of a single part. Directed energy deposition (DED) metal additive technology has enabled the manufacturing of CGAs, but design these alloys remains a challenge. One important challenge is to avoid alloy compositions that result in the formation of deleterious phases during manufacturing. While designers can use CALculation of PHAse Diagram (CALPHAD) models predict the presence of deleterious phases, these calculations tend to be too costly to incorporate directly in a computational design framework. In this work, we apply deep ensembles, or ensembles of deep artificial neural networks (ANNs), to learn a surrogate model of deleterious phase boundaries based on CALPHAD simulations. The learned model is used as a constraint by a path planning algorithm to identify gradient pathway through metal composition space that can be successfully manufactured. We demonstrate the deep ensemble approach in the Fe-Ni-Cr-Ti quaternary system and benchmark it against individual ANNs and a K-nearest neighbors (KNN) approach reported previously. Additionally, we investigate the use of the predicted class probability threshold as a means for understanding surrogate model uncertainty and reasoning about the design space. Lastly, we illustrate how varying the thresholds on constraint probability results in a trade off between manufacturing risk and identifying solutions through narrow passageways.

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Pillai, Rishi, Q. Q. Ren, Yi-Feng Su, Rebecca Kurfess, Thomas Feldhausen e Soumya Nag. "Leveraging Additive Manufacturing to Fabricate High Temperature Alloys With Co-Designed Mechanical Properties and Environmental Resistance". In ASME Turbo Expo 2023: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2023. http://dx.doi.org/10.1115/gt2023-103009.

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Abstract A paradigm shift in the traditional sequential design approaches is critically essential to create application-specific hierarchical and multifunctional materials with superior long-term performance for next-generation energy technologies involving extreme environments. In the current work, we aim to leverage the flexibility and geometric/compositional complexity offered by additive manufacturing to demonstrate this new approach by co-designing a compositionally graded Ni-based alloy for molten salts\sCO2 heat exchangers to enable mitigation of environmental degradation of surfaces exposed to molten halide salts, while simultaneously suppressing the consequent deterioration in mechanical stability. Thermokinetic modeling describing the underlying physics of thermally- and environmentally induced spatiotemporal compositional and microstructural evolution will be employed to predict the parameter space of material deposition processes and precisely identify the required composition gradient. Preliminary corrosion and mechanical testing of the dual material demonstrated the potential of the material to replace existing solid solution strengthened materials for this application.

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Allen, Marshall, Tanner Kirk, Richard Malak e Raymundo Arroyave. "A Subspace-Inclusive Sampling Method for the Computational Design of Compositionally Graded Alloys". In ASME 2021 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/detc2021-68836.

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Abstract Compositionally graded alloys, a special class of functionally graded materials (FGMs), utilize localized variations in composition within a single metal part to achieve higher performance than traditional single-material parts. In previous work [1], the authors presented a computational design methodology that avoids common issues which limit a gradient alloy’s usefulness or feasibility, such as deleterious phases or properties, and also optimizes gradients for performance objectives. However, the previous methodology only samples the interior of a composition space, meaning designed gradients must include all elements in the space at every step in the gradient. Because the addition of even a small amount of an alloying element can introduce a new deleterious phase, this characteristic often neglects potentially simpler solutions to otherwise unsolvable problems and, consequently, discourages the addition of new elements to the state space. The present work improves upon the previous methodology by introducing a sampling method that includes subspaces with fewer elements in the design search. The new sampling method samples within an artificial expanded form of the state space and projects samples outside the true region to the nearest true subspace. This method is evaluated first by observing the distribution of samples in each subspace of a 2-D, 3-D, and 4-D state space. Next, a parametric study in a synthetic 2-D problem compares the performance of the new sampling scheme to the previous methodology. Lastly, the updated methodology is applied to design a gradient from stainless steel to equiatomic NiTi that has practical uses such as embedded shape memory actuation and for which the previous methodology fails to find a feasible path.

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Wang, Fude, Junfa Mei e Xinhua Wu. "Microstructure study of direct laser fabricated compositionally graded ti alloys using simultaneous feed of powder and wire". In ICALEO® 2005: 24th International Congress on Laser Materials Processing and Laser Microfabrication. Laser Institute of America, 2005. http://dx.doi.org/10.2351/1.5060509.

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Capasso, Federico, C. Tu e K. Mohammed. "New high gain staircase photoconductors and observation of sawtooth-to-stalrcase transition in compositionally graded heterostructures". In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1986. http://dx.doi.org/10.1364/oam.1986.tub6.

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Staircase heterostructures have recently been proposed as a means of achieving noise-free photomultiplierlike avalanche gain and repeated velocity overshoot. No experimental study of transport in such structures has so far been reported. In this paper we report the first investigation of carrier transport in a staircase potential configuration. The latter is obtained by appropritely biasing an MBE compositionally graded multilayer AIGaAs structure contacted by two n+ regions. The graded gap undoped region consists of three layers each graded from x = 0 to x = 0.2 over a distance of 5000 Å. A new photoconductive gain phenomenon which is peculiar to these graded materials is found. Dramatic differences in the photoconductivity are observed as the band diagram changes from a sawtooth to a staircase configuration, with increasing bias. In the staircase conduction band configuration electrons have high velocity while holes are slowed down and partially trapped by virtue of the valence band steps. This leads to high current gain (≥ 104). In the sawtooth configuration, on the other hand, the opposite occurs and the gain dramatically decreases (≤ 10). By engineering the staircase band diagram the performance of the photoconductor (gain and gain-bandwidth product) can be tuned over a very wide range. Other device applications are also discussed.

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Mayas, Magda. Creating with timbre. Norges Musikkhøgskole, agosto 2018. http://dx.doi.org/10.22501/nmh-ar.686088.

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Unfolding processes of timbre and memory in improvisational piano performance This exposition is an introduction to my research and practice as a pianist, in which I unfold processes of timbre and memory in improvised music from a performer’s perspective. Timbre is often understood as a purely sonic perceptual phenomenon. However, this is not in accordance with a site-specific improvisational practice with changing spatial circumstances impacting the listening experience, nor does it take into account the agency of the instrument and objects used or the performer’s movements and gestures. In my practice, I have found a concept as part of the creating process in improvised music which has compelling potential: Timbre orchestration. My research takes the many and complex aspects of a performance environment into account and offers an extended understanding of timbre, which embraces spatial, material and bodily aspects of sound in improvised music performance. The investigative projects described in this exposition offer a methodology to explore timbral improvisational processes integrated into my practice, which is further extended through collaborations with sound engineers, an instrument builder and a choreographer: -experiments in amplification and recording, resulting in Memory piece, a series of works for amplified piano and multichannel playback - Piano mapping, a performance approach, with a custom-built device for live spatialization as means to expand and deepen spatio-timbral relationships; - Accretion, a project with choreographer Toby Kassell for three grand pianos and a pianist, where gestural approaches are used to activate and compose timbre in space. Together, the projects explore memory as a structural, reflective and performative tool and the creation of performing and listening modes as integrated parts of timbre orchestration. Orchestration and choreography of timbre turn into an open and hybrid compositional approach, which can be applied to various contexts, engaging with dynamic relationships and re-configuring them.

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