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Sample records for alumina-iron functionally graded

  1. Fabrication and characteristics of alumina-iron functionally graded materials

    DEFF Research Database (Denmark)

    He, Zeming; Ma, J.; Tan, G.E.B.

    2009-01-01

    In the present work, five-layered alumina–iron functionally graded materials (FGMs) were fabricated via a simple route of die pressing and pressureless sintering. The shrinkage differences among the layers in the FGM were minimized by particle size selection and processing control. The...

  2. Functionally graded cermets

    Directory of Open Access Journals (Sweden)

    L. Jaworska

    2006-04-01

    Full Text Available Purpose: Cermets have very good plasticity and high hardness. Functionally graded cermets secure obtaining of cutting tools with hard wear resistance surface layer and ductile body frame. A new FGM was obtained using P/M method.Design/methodology/approach: Materials were obtained using free sintering at vacuum and the high temperature-high pressure sintering method. Functionally graded cermets have more amount of hard phase in the surface layer and lower participation of this phase in the body frame. FGMs were prepared by the layers pressing method and the centrifugal deposition method.Findings: Material with 55 wt.% of TiC and 45 wt.% of (Ni,Mo was prepared. The phase’s composition of this material was analysed. The ring structure of material and complex carbides formation was confirmed. The gradient of the phase composition and hardness measurement are presented. Phase composition of FGM strongly depend on conditions of centrifugal sedimentation process: duration, rotation speed, solid content, dispersive liquids. The centrifugal deposition process of powders forming guarantees gradient phase composition for materials obtaining the powder metallurgy methods. The FGM obtained by powders forming method should be sintered using pressure processes in a closed containers (or special assembly because of materials high porosity which is a result of various chemical contents of this same material parts.Practical implications: Due to their low chemical affinity to steel and the resistance for high temperatures oxidation, cermets have better cutting properties than carbides. Application of cermet inserts guarantees the high quality of machined surface (low roughness. Cermets could be used in “dry cutting” processes.Originality/value: The centrifugal deposition method for powders with phases content gradient forming is original value.

  3. Complex permittivity scaling of functionally graded composites

    International Nuclear Information System (INIS)

    In this paper, we provide a fundamental understanding of dielectric loss behavior as a function of applied electric field and frequency in functionally graded composites with varying numbers of layers and compositions. A new power-law scaling relation in the form of ϵ′′∝fpEoq was derived based upon the ferroelectric hysteresis. The magnitude of the imaginary component of the dielectric permittivity (ϵ′′) was estimated from the polarization–electric field hysteresis loop. The changes in exponents of the scaling relation were correlated with the mechanism controlling the dielectric loss and interfacial coupling in graded structures. Building upon the scaling analysis, we investigated the effect of E-field on the domain mobility (μ) for various functionally graded systems. These results were correlated with the experimental investigation on ferroelectric domains using transmission electron microscopy and piezoresponse force microscopy. (papers)

  4. Functionally graded WC-Co hardmetals

    International Nuclear Information System (INIS)

    Functionally graded hardmetals with a continuous gradient in cobalt and TiC were manufactured by electrophoretic deposition (EPD). Most attention was focussed on obtaining a fully dense and phase-pure material without loosing the cobalt gradient during sintering. WC-Co graded plates of 35x35 mm were processed by electrophoretic deposition, cold isostatic pressing and sintering. The resulting graded material showed a continuous variation in composition, microstructure and mechanical properties. The cobalt content in the WC-Co FGM increased from about 6 wt.% on the hard side to 17 wt.% on the soft side, whereas the Vickers hardness, HV10, was found to decrease continuously from 19 to 8.5 GPa along the same direction. The WC-Co-TiC FGM contained a TiC gradient from 0 to 25 wt.% and Vickers hardness values from 16.3 up to 19.8 GPa along the same direction. (author)

  5. Photothermal characterization of functionally graded materials (FGM)

    International Nuclear Information System (INIS)

    This paper deals with the photothermal characterization of functionally graded materials (FGM) whose thermal properties are varying parallel to the sample surface. Simple experimental configurations and associated inversion procedures are proposed either for thermal mapping or for pitch-catch imaging mode. The photothermally induced periodic temperature field at the sample surface is first calculated using a specific code, then the inversion procedures are checked using a simulated set of data. Preliminary experimental results are presented outlining need of specific filter to cope with experimental noise

  6. Modeling Bamboo as a Functionally Graded Material

    International Nuclear Information System (INIS)

    Natural fibers are promising for engineering applications due to their low cost. They are abundantly available in tropical and subtropical regions of the world, and they can be employed as construction materials. Among natural fibers, bamboo has been widely used for housing construction around the world. Bamboo is an optimized composite material which exploits the concept of Functionally Graded Material (FGM). Biological structures, such as bamboo, are composite materials that have complicated shapes and material distribution inside their domain, and thus the use of numerical methods such as the finite element method and multiscale methods such as homogenization, can help to further understanding of the mechanical behavior of these materials. The objective of this work is to explore techniques such as the finite element method and homogenization to investigate the structural behavior of bamboo. The finite element formulation uses graded finite elements to capture the varying material distribution through the bamboo wall. To observe bamboo behavior under applied loads, simulations are conducted considering a spatially-varying Young's modulus, an averaged Young's modulus, and orthotropic constitutive properties obtained from homogenization theory. The homogenization procedure uses effective, axisymmetric properties estimated from the spatially-varying bamboo composite. Three-dimensional models of bamboo cells were built and simulated under tension, torsion, and bending load cases

  7. An asymptotically exact theory of functionally graded piezoelectric shells

    CERN Document Server

    Le, Khanh Chau

    2016-01-01

    An asymptotically exact two-dimensional theory of functionally graded piezoelectric shells is derived by the variational-asymptotic method. The error estimation of the constructed theory is given in the energetic norm. As an application, analytical solution to the problem of forced vibration of a functionally graded piezoceramic cylindrical shell with thickness polarization fully covered by electrodes and excited by a harmonic voltage is found.

  8. Magnetothermoelastic creep analysis of functionally graded cylinders

    Energy Technology Data Exchange (ETDEWEB)

    Loghman, A., E-mail: aloghman@kashanu.ac.i [Department of Mechanical Engineering, Faculty of Engineering, University of Kashan, Kashan 87317-51167 (Iran, Islamic Republic of); Ghorbanpour Arani, A.; Amir, S. [Department of Mechanical Engineering, Faculty of Engineering, University of Kashan, Kashan 87317-51167 (Iran, Islamic Republic of); Vajedi, A. [Department of Mechanical Engineering, Islamic Azad University, Arak Branch, Arak (Iran, Islamic Republic of)

    2010-07-15

    This paper describes time-dependent creep stress redistribution analysis of a thick-walled FGM cylinder placed in uniform magnetic and temperature fields and subjected to an internal pressure. The material creep, magnetic and mechanical properties through the radial graded direction are assumed to obey the simple power law variation. Total strains are assumed to be the sum of elastic, thermal and creep strains. Creep strains are time, temperature and stress dependent. Using equations of equilibrium, stress-strain and strain-displacement a differential equation, containing creep strains, for displacement is obtained. Ignoring creep strains in this differential equation a closed form solution for the displacement and initial magnetothermoelastic stresses at zero time is presented. Initial magnetothermoelastic stresses are illustrated for different material properties. Using Prandtl-Reuss relation in conjunction with the above differential equation and the Norton's law for the material uniaxial creep constitutive model, the radial displacement rate is obtained and then the radial and circumferential creep stress rates are calculated. Creep stress rates are plotted against dimensionless radius for different material properties. Using creep stress rates, stress redistributions are calculated iteratively using magnetothermoelastic stresses as initial values for stress redistributions. It has been found that radial stress redistributions are not significant for different material properties, however major redistributions occur for circumferential and effective stresses.

  9. Two-dimensional thermoelasticity solution for functionally graded thick beams

    Institute of Scientific and Technical Information of China (English)

    Lü; Chaofeng

    2006-01-01

    [1]Suresh S,Mortensen A.Fundamentals of Functionally Graded Materials.London:IOM Communications,1998[2]Wetherhold R C,Seelman S,Wang J Z.The use of functionally graded materials to eliminate or control thermal deformation.Compos Sci Technol,1996,56:1099―1104[3]Almajid A,Taya M,Hudnut S.Analysis of out-of-plane displacement and stress field in a piezo-composite plate with functionally graded microstructure.Int J Solids Struct,2001,38:3377―3391[4]Wu X H,Chen C Q,Shen Y P,et al.A high order theory for functionally graded piezoelectric shells.Int J Solids Struct,2002,39:5325―5344[5]Ootao Y,Tanigawa Y.Three-dimensional transient piezothermo-elasticity in functional graded rectangular plate bonded to a piezoelectric plate.Int J Solids Struct,2000,37:4377―4401[6]Chen W Q,Ding H J.On free vibration of a functionally graded piezoelectric rectangular plate.Acta Mech,2002,153:207―216[7]Chen W Q,Bian Z G,Lv C F,et al.3D free vibration analysis of a functionally graded piezoelectric hollow cylinder filled with compressible fluid.Int J Solids Struct,2004,41:947―964[8]Zhong Z,Shang E T.Exact analysis of simply supported functionally graded piezothermoelectric plates.J Intell Mater Syst Struct,2005,16:643―651[9]Sankar B V.An elasticity solution for functionally graded beams.Compos Sci Technol,2001,61:689―696[10]Sankar B V,Tzeng J T.Thermal stresses in functionally graded beams.AIAA J,2002,40:1228―1232[11]Zhu H,Sankar B V.A combined Fourier series-Galerkin method for the analysis of functionally graded beams.J Appl Mech-Trans ASME,2004,71:421―424[12]Chen W Q,Lv C F,Bian Z G.Elasticity solution for free vibration of laminated beams.Compos Struct,2003,62:75―82[13]Nagem R J,Williams J H.Dynamic analysis of large space structures using transfer matrices and joint coupling matrices.Mech Struct Mach,1989,17:349―371[14]Ding H J,Chen W Q,Zhang L C.Elasticity of Transversely Isotropic Materials.Dordrecht:Springer-Verlag,2006[15]Shu C.Differential Quadrature and Its

  10. Elasticity solutions for functionally graded plates in cylindrical bending

    Institute of Scientific and Technical Information of China (English)

    YANG Bo; DING Hao-jiang; CHEN Wei-qiu

    2008-01-01

    The plate theory of functionally graded materials suggested by Mian and Spencer is extended to analyze the cylindrical bending problem of a functionally graded rectangular plate subject to uniform load. The expansion formula for displacements is adopted. While keeping the assumption that the material parameters can vary along the thickness direction in an arbitrary fashion, this paper considers orthotropic materials rather than isotropic materials. In addition, the traction-free condition on the top surface is replaced with the condition of uniform load applied on the top surface. The plate theory for the particular case of cylindrical bending is presented by considering an infinite extent in the y-direction. Effects of boundary conditions and material inhomogeneity on the static response of functionally graded plates are investigated through a numerical example.

  11. Fracture Analysis of Functionally Graded Materials by a BEM

    OpenAIRE

    Gao, X.W.; Zhang, Ch.; Sladek, J.; Sladek, V.

    2009-01-01

    Fracture Analysis of Functionally Graded Materials by a BEM correspondance: Corresponding author. Tel.: +49 271 7402173; fax: +49 271 7404074. (Zhang, Ch.) (Zhang, Ch.) Department of Engineering Mechanics--> , Southeast University--> , Nanjing--> - CHINA (Gao, X.W.) Department of Civil Engineering--> , University of Siegen--> , D-57068 Siegen--> - GERMANY (Zhang, ...

  12. Interfacial adhesion of laser clad functionally graded materials

    NARCIS (Netherlands)

    De Hosson, JTM; Pei, YT; Ocelik, [No Value; Sudarshan, TS; Stiglich, JJ; Jeandin, M

    2002-01-01

    Specially designed samples of laser clad AlSi40 functionally graded materials (FGM) are made for evaluating the interfacial adhesion. To obtain the interfacial bond strength notches are made right at the interface of the FGMs. In-sitit microstructural observations during straining in an FEG-ESEM (fi

  13. Interfacial adhesion of laser clad functionally graded materials

    NARCIS (Netherlands)

    Pei, Y. T.; Ocelik, V.; De Hosson, J. T. M.

    2003-01-01

    Specially designed samples of laser clad AlSi40 functionally graded materials (FGM) are made for evaluating the interfacial adhesion. To obtain the interfacial bond strength notches are made right at the interface of the FGMs. In-situ microstructural observations during straining in a field-emission

  14. The elastic response for microlayered functionally graded media

    OpenAIRE

    Jedrysiak, J.; Wierzbicki, E.; Wozniak, Cz.

    2006-01-01

    In this note microlayered composites having continuously varying macroscopic properties are considered. Such compositesare referred to as the functionally graded laminates (FGL). The aim of this contribution is to derive a new averaged model describing the elastic response of the FGL, using the modified tolerance averaging technique, developed for periodic composites and structures by Wozniak and Wierzbicki (2000).

  15. Structural integrity of engineering components made of functionally graded materials

    OpenAIRE

    Oyekoya, Oyedele O.

    2008-01-01

    Functionally graded materials (FGM) are composite materials with microstructure gradation optimized for the functioning of engineering components. For the case of fibrous composites, the fibre density is varied spatially, leading to variable material properties tailored to specific optimization requirements. There is an increasing demand for the use of such intelligent materials in space and aircraft industries. The current preferred methods to study engineering components made...

  16. Preparation and Fatigue Properties of Functionally Graded Cemented Carbides

    International Nuclear Information System (INIS)

    Cemented carbides with a functionally graded structure have significantly improved mechanical properties and lifetimes in cutting, drilling and molding. In this work, WC-6 wt.% Co cemented carbides with three-layer graded structure (surface layer rich in WC, mid layer rich in Co and the inner part of the average composition) were prepared by carburizing pre-sintered η-phase-containing cemented carbides. The three-point bending fatigue tests based on the total-life approach were conducted on both WC-6wt%Co functionally graded cemented carbides (FGCC) and conventional WC-6wt%Co cemented carbides. The functionally graded cemented carbide shows a slightly higher fatigue limit (∼100 MPa) than the conventional ones under the present testing conditions. However, the fatigue crack nucleation behavior of FGCC is different from that of the conventional ones. The crack nucleates preferentially along the Co-gradient and perpendicular to the tension surface in FGCC, while parallel to the tension surface in conventional cemented carbides

  17. Functionally Graded Dual-Nanoparticulate-Reinforced Aluminum Matrix Composite Materials

    International Nuclear Information System (INIS)

    Functionally graded carbon nanotubes (CNT) and nano Silicon carbide (nSiC) reinforced aluminum (Al) matrix composite materials were fully densified by a simple ball milling and hot-pressing processes. The nSiC was used as a physical mixing agent to increase dispersity of the CNT in the Al particles. It was observed that the CNT was better dispersed in the Al particles with a nSiC mixing agent compared to without it used. SEM micrograph showed that the interface of the each layers had very tightly adhesion without any serious pores and micro-cracks. This functionally graded dual-nanoparticulate-reinforced Al matrix composite by powder metallurgical approach could also be applied to comples matrix materials.

  18. ANALYSIS OF BAMBOO AS A FUNCTIONALLY GRADED MATERIAL

    OpenAIRE

    G. LOKESHA; M. VENKATARAMA REDDY; T. YELLA REDDY

    2014-01-01

    Bamboo is an optimized natural composite that exploits the concept of Functionally Graded Material (FGM). Biological structures such as bamboo have complicated micro-structural shapes and material distribution, and thus the use of numerical methods such as finite element method can be a useful tool for understanding the mechanical behavior of these materials. This paper explores techniques such as finite element method to investigate the structural behavior of bamboo. Two-dimensional model...

  19. Fabrication of a Functionally Graded Copper-Zinc Sulfide Phosphor

    Science.gov (United States)

    Park, Jehong; Park, Kwangwon; Kim, Jongsu; Jeong, Yongseok; Kawasaki, Akira; Kwon, Hansang

    2016-03-01

    Functionally graded materials (FGMs) are compositionally gradient materials. They can achieve the controlled distribution of the desired characteristics within the same bulk material. We describe a functionally graded (FG) metal-phosphor adapting the concept of the FGM; copper (Cu) is selected as a metal and Cu- and Cl-doped ZnS (ZnS:Cu,Cl) is selected as a phosphor and FG [Cu]-[ZnS:Cu,Cl] is fabricated by a very simple powder process. The FG [Cu]-[ZnS:Cu,Cl] reveals a dual-structured functional material composed of dense Cu and porous ZnS:Cu,Cl, which is completely combined through six graded mediating layers. The photoluminescence (PL) of FG [Cu]-[ZnS:Cu,Cl] is insensitive to temperature change. FG [Cu]-[ZnS:Cu,Cl] also exhibits diode characteristics and photo reactivity for 365 nm -UV light. Our FG metal-phosphor concept can pave the way to simplified manufacturing of low-cost and can be applied to various electronic devices.

  20. Fabrication of a Functionally Graded Copper-Zinc Sulfide Phosphor

    Science.gov (United States)

    Park, Jehong; Park, Kwangwon; Kim, Jongsu; Jeong, Yongseok; Kawasaki, Akira; Kwon, Hansang

    2016-01-01

    Functionally graded materials (FGMs) are compositionally gradient materials. They can achieve the controlled distribution of the desired characteristics within the same bulk material. We describe a functionally graded (FG) metal-phosphor adapting the concept of the FGM; copper (Cu) is selected as a metal and Cu- and Cl-doped ZnS (ZnS:Cu,Cl) is selected as a phosphor and FG [Cu]-[ZnS:Cu,Cl] is fabricated by a very simple powder process. The FG [Cu]-[ZnS:Cu,Cl] reveals a dual-structured functional material composed of dense Cu and porous ZnS:Cu,Cl, which is completely combined through six graded mediating layers. The photoluminescence (PL) of FG [Cu]-[ZnS:Cu,Cl] is insensitive to temperature change. FG [Cu]-[ZnS:Cu,Cl] also exhibits diode characteristics and photo reactivity for 365 nm -UV light. Our FG metal-phosphor concept can pave the way to simplified manufacturing of low-cost and can be applied to various electronic devices. PMID:26972313

  1. Hardness profile measurements in functionally graded WC-Co composites

    Energy Technology Data Exchange (ETDEWEB)

    Larsson, C.; Oden, M

    2004-09-25

    Micro- and nanoindentation were used to determine hardness as a function of depth in two functionally graded WC-Co composites. The gradients were continuous (extended over {approx}70 and {approx}40 {mu}m, respectively) and consisted of varying WC and Co phase volume fractions. Five comparable homogeneous samples with different Co contents and different average WC grain sizes were also used for direct comparison. A relationship between hardness and Co content was established for both the graded and the homogeneous samples wherein the hardness decreased with increasing Co content. The magnitude of the hardness was the same (for a given Co content) for the functionally graded and the homogeneous materials. The hardness measurements were also correlated with X-ray diffraction studies of thermal residual stresses and the absence of any major influence explained. It is generally concluded that the hardness values are dominated by the local Co content. Additionally, the examination of surface cracks around indents suggests that compositional gradients in WC-Co composites offer increased toughness.

  2. Hardness profile measurements in functionally graded WC-Co composites

    International Nuclear Information System (INIS)

    Micro- and nanoindentation were used to determine hardness as a function of depth in two functionally graded WC-Co composites. The gradients were continuous (extended over ∼70 and ∼40 μm, respectively) and consisted of varying WC and Co phase volume fractions. Five comparable homogeneous samples with different Co contents and different average WC grain sizes were also used for direct comparison. A relationship between hardness and Co content was established for both the graded and the homogeneous samples wherein the hardness decreased with increasing Co content. The magnitude of the hardness was the same (for a given Co content) for the functionally graded and the homogeneous materials. The hardness measurements were also correlated with X-ray diffraction studies of thermal residual stresses and the absence of any major influence explained. It is generally concluded that the hardness values are dominated by the local Co content. Additionally, the examination of surface cracks around indents suggests that compositional gradients in WC-Co composites offer increased toughness

  3. Supersonic flutter analysis of thin cracked functionally graded material plates

    CERN Document Server

    Natarajan, S; Bordas, S

    2012-01-01

    In this paper, the flutter behaviour of simply supported square functionally graded material plates immersed in a supersonic flow is studied. An enriched 4-noded quadrilateral element based on field consistency approach is used for this study and the crack is modelled independent of the underlying mesh. The material properties are assumed to be temperature dependent and graded only in the thickness direction. The effective material properties are estimated using the rule of mixtures. The formulation is based on the first order shear deformation theory and the shear correction factors are evaluated employing the energy equivalence principle. The influence of the crack length, the crack orientation, the flow angle and the gradient index on the aerodynamic pressure and the frequency are numerically studied. The results obtained here reveal that the critical frequency and the critical pressure decreases with increase in crack length and it is minimum when the crack is aligned to the flow angle.

  4. Plasma spray forming of functionally graded materials mould

    Institute of Scientific and Technical Information of China (English)

    ZHAO Zi-yu; FANG Jian-cheng; LI Hong-you

    2005-01-01

    A new technology of functionally graded materials(FGM) mould fabricated by plasma spraying and arc spraying was developed. According to applied characteristic of plastic mould, the reasonable coatings of FGM were designed and their microstructures were analyzed. At the same time, some key problems were solved including spray mould fabricating, FGM forming and demoulding, etc. The results show that the service performance of the FGM mould is much more excellent than the one composed of the traditional materials, and the life span can also be greatly increased. The technology will have a significant influence on materials development in mould industry.

  5. A functionally graded material model of cracked polymer weld

    Czech Academy of Sciences Publication Activity Database

    Ševčík, Martin; Hutař, Pavel; Náhlík, Luboš; Knésl, Zdeněk

    Bratislava : Vydavatelstvo STU v Bratislave, 2009 - (Murín, J.; Kutiš, V.; Ďuriš, R.), s. 1-10 ISBN 978-80-227-3067-9. [Computational modelling and advanced simulations 2009. Bratislava (SK), 30.06.2009-03.07.2009] R&D Projects: GA ČR GC101/09/J027; GA ČR GD106/09/H035 Institutional research plan: CEZ:AV0Z20410507 Keywords : functionally graded material * stress intensity factor * polymer weld * strip model Subject RIV: JL - Materials Fatigue, Friction Mechanics

  6. Thermal Characterization of Functionally Graded Materials: Design of Optimum Experiments

    Science.gov (United States)

    Cole, Kevin D.

    2003-01-01

    This paper is a study of optimal experiment design applied to the measure of thermal properties in functionally graded materials. As a first step, a material with linearly-varying thermal properties is analyzed, and several different tran- sient experimental designs are discussed. An optimality criterion, based on sen- sitivity coefficients, is used to identify the best experimental design. Simulated experimental results are analyzed to verify that the identified best experiment design has the smallest errors in the estimated parameters. This procedure is general and can be applied to design of experiments for a variety of materials.

  7. Functionally graded alumina-based thin film systems

    Science.gov (United States)

    Moore, John J.; Zhong, Dalong

    2006-08-29

    The present invention provides coating systems that minimize thermal and residual stresses to create a fatigue- and soldering-resistant coating for aluminum die casting dies. The coating systems include at least three layers. The outer layer is an alumina- or boro-carbide-based outer layer that has superior non-wettability characteristics with molten aluminum coupled with oxidation and wear resistance. A functionally-graded intermediate layer or "interlayer" enhances the erosive wear, toughness, and corrosion resistance of the die. A thin adhesion layer of reactive metal is used between the die substrate and the interlayer to increase adhesion of the coating system to the die surface.

  8. Thermoelastic analysis of a cylindrical vessel of functionally graded materials

    International Nuclear Information System (INIS)

    This paper presents a novel method for analyzing steady thermal stresses in a functionally graded hollow cylinder. The thermal and thermoelastic parameters are assumed to arbitrarily vary along the radial direction of the hollow cylinder. The boundary value problem associated with a thermoelastic problem is converted to a Fredholm integral equation. By numerically solving the resulting equation, the distribution of the thermal stresses and radial displacement is obtained. The numerical results obtained are presented graphically and the influence of the gradient variation of the material properties on thermal stresses is investigated. It is found that appropriate gradient can make the distribution of thermal stresses more gentle in the whole structure.

  9. Microwave sintering of W/Cu functionally graded materials

    Energy Technology Data Exchange (ETDEWEB)

    Liu, R.; Hao, T.; Wang, K.; Zhang, T.; Wang, X.P.; Liu, C.S. [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); Fang, Q.F., E-mail: qffang@issp.ac.cn [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China)

    2012-12-15

    Fabricating W/Cu functionally graded materials (FGM) with fine microstructure and good properties is extremely significant in the development of fusion reactors as well as spallation neutron sources. The five-layered W/Cu FGM (W30% + Cu70%/W50% + Cu50%/W70% + Cu30%/W90% + Cu10%/W100%, volume fraction) were fabricated by a microwave sintering method in a short time (30 min). Scanning electron microscopy and energy dispersive X-ray spectrometer analysis showed that the graded structure can be retained although the microwave sintering temperature was as high as 1300 Degree-Sign C (well above the melting temperature of Cu) and the fine microstructure of W in each layer can be also maintained due to the short sintering time. The overall relative density of the W/Cu FGM sample microwave-sintered at 1350 Degree-Sign C reaches 93% and the copper-rich layers are almost 100% dense. The thermal conductivity of the sample is about 200 W/mK at room temperature and decreases with increasing temperature.

  10. Experimental Study of Functionally Graded Beam with Fly Ash

    Science.gov (United States)

    Bajaj, K.; Shrivastava, Y.; Dhoke, P.

    2013-11-01

    Generally, concrete used in the field suffers from lack of durability and homogeneity. As cement is the only binding material in concrete and due to hike in its price, researchers have been looking for apt substitutes. For the sake of economy, strength and anti-corrosion functionally graded beam (FGB) has developed having one layer of normal concrete and another of high volume fly-ash concrete (HVFAC). The flexural behavior FGB has analyzed experimentally in this work with variation in interface as 0, 25, 50, 75 and 100 from bottom. In this study, HVFAC has prepared with replacement of cement by 20, 35 and 55 % with fly ash for M20 and M30 grade of concrete. It has seemed that there is 12.86 and 3.56 % increase in compressive and flexural strength of FGB. The bond strength FGM cube is optimum at 50 mm depth. As FGM is economical, having more durability and strength, so its adoption enables more sustainability in concrete industry.

  11. Applications and functions of food-grade phosphates.

    Science.gov (United States)

    Lampila, Lucina E

    2013-10-01

    Food-grade phosphates are used in the production of foods to function as buffers, sequestrants, acidulants, bases, flavors, cryoprotectants, gel accelerants, dispersants, nutrients, precipitants, and as free-flow (anticaking) or ion-exchange agents. The actions of phosphates affect the chemical leavening of cakes, cookies, pancakes, muffins, and doughnuts; the even melt of processed cheese; the structure of a frankfurter; the bind and hydration of delicatessen meats; the fluidity of evaporated milk; the distinctive flavor of cola beverages; the free flow of spice blends; the mineral content of isotonic beverages; and the light color of par-fried potato strips. In the United States, food-grade phosphates are generally recognized as safe, but use levels have been defined for some foods by the Code of Federal Regulations, specifically Titles 9 and 21 for foods regulated by the U.S. Department of Agriculture (USDA) and the U.S. Food and Drug Administration (FDA), respectively. Standards for food purity are defined nationally and internationally in sources such as the Food Chemicals Codex and the Joint Food and Agriculture Organization and World Health Organization (FAO/WHO) Expert Committee on Food Additives. PMID:24033359

  12. Nanoindentation of functionally graded hybrid polymer/metal thin films

    International Nuclear Information System (INIS)

    Hybrid functionally graded coatings (2D-FGC) were deposited by magnetron co-sputtering from poly(tetrafluoroethylene) (PTFE) and AISI 316L stainless steel (316L) targets. The carbon and fluorine content varied from 7.3 to 23.7 at.% and from 0 to 57 at.%, respectively. The surface modification was developed to change the surface of 316L vascular stents in order to improve the biocompatibility of the outmost layer of the metallic biomaterial. In-depth XPS analysis revealed the presence of a graded chemical composition accompanied by the variation of the film structure. These results were complemented by those of transmission electron microscopy (TEM) analysis that highlighted the nanocomposite nature of the coatings. The nanomechanical characterization of 2D-FGC was performed by nanoindentation at several loads on the thin films deposited onto two different steel substrates: 316L and AISI M2. The study allowed establishing 0.7 mN as the load that characterized the coatings without substrate influence. Both hardness and Young modulus decrease with the increase of fluorine content due to the evolution in chemical composition, chemical bonds and structure.

  13. Nanoindentation of functionally graded hybrid polymer/metal thin films

    Energy Technology Data Exchange (ETDEWEB)

    Nunes, J.; Piedade, A.P., E-mail: ana.piedade@dem.uc.pt

    2013-11-01

    Hybrid functionally graded coatings (2D-FGC) were deposited by magnetron co-sputtering from poly(tetrafluoroethylene) (PTFE) and AISI 316L stainless steel (316L) targets. The carbon and fluorine content varied from 7.3 to 23.7 at.% and from 0 to 57 at.%, respectively. The surface modification was developed to change the surface of 316L vascular stents in order to improve the biocompatibility of the outmost layer of the metallic biomaterial. In-depth XPS analysis revealed the presence of a graded chemical composition accompanied by the variation of the film structure. These results were complemented by those of transmission electron microscopy (TEM) analysis that highlighted the nanocomposite nature of the coatings. The nanomechanical characterization of 2D-FGC was performed by nanoindentation at several loads on the thin films deposited onto two different steel substrates: 316L and AISI M2. The study allowed establishing 0.7 mN as the load that characterized the coatings without substrate influence. Both hardness and Young modulus decrease with the increase of fluorine content due to the evolution in chemical composition, chemical bonds and structure.

  14. Nonlinear analysis of functionally graded laminates considering piezoelectric effect

    Energy Technology Data Exchange (ETDEWEB)

    Behjat, Ba Shir [Mechanical Engineering Faculty Sahand Univ. of Technology, Sahand New Tawn (Iran, Islamic Republic of); Khoshravan Mohamad Reza [Tabriz Univ., Tabriz (Iran, Islamic Republic of)

    2012-08-15

    In this paper, static bending analysis of functionally graded plates with piezoelectric layers has been carried out considering geometrical nonlinearity in different sets of mechanical and electrical loadings. Only the geometrical nonlinearity has been taken into account. The governing equations are obtained using potential energy and Hamilton's principle. The finite element model is derived based on constitutive equation of piezoelectric material accounting for coupling between elasticity and electric effect by using higher order elements. The present finite element used displacement and electric potential as nodal degrees of freedom. Results are presented for two constituent FGM plate under different mechanical boundary conditions. Numerical results for FGM plate are given in dimensionless graphical forms. Effects of material composition and boundary conditions on nonlinear response of the plate are also studied.

  15. Thermal behavior of the duct applied functionally graded material

    International Nuclear Information System (INIS)

    In Unmanned Aerial Vehicles (UAV), the high temperature results from friction among the air, combustion of fuel in engine and combustion gas of a nozzle. The high temperature may cause serious damages in UAV structure. The Functionally Graded Material(FGM) is chosen as a material of the engine duct structure. Thermal stress analysis of FGM is performed in this paper. FGM is composed of two constituent materials that are mixed up according to the specific volume fraction distribution in order to withstand high temperature. Therefore, hoop stress, axial stress and shear stress of duct with 2 layers, 4 layers and 8 layers FGM are compared and analyzed respectively. In addition, the creep behavior of FGM used in duct structure of an engine is analyzed for better understanding of FGM characteristics

  16. Analyses of functionally graded plates with a magnetoelectroelastic layer

    International Nuclear Information System (INIS)

    A meshless local Petrov–Galerkin (MLPG) method is presented for the analysis of functionally graded material (FGM) plates with a sensor/actuator magnetoelectroelastic layer localized on the top surface of the plate. The Reissner–Mindlin shear deformation theory is applied to describe the plate bending problem. The expressions for the bending moment, shear force and normal force are obtained by integration through the FGM plate and magnetoelectric layer for the corresponding constitutive equations. Then, the original three-dimensional (3D) thick-plate problem is reduced to a two-dimensional (2D) problem. Nodal points are randomly distributed over the mean surface of the considered plate. Each node is the center of a circle surrounding the node. The weak-form on small subdomains with a Heaviside step function as the test function is applied to derive local integral equations. After performing the spatial MLS approximation, a system of ordinary differential equations of the second order for certain nodal unknowns is obtained. The derived ordinary differential equations are solved by the Houbolt finite-difference scheme. Pure mechanical loads or electromagnetic potentials are prescribed on the top of the layered plate. Both stationary and transient dynamic loads are analyzed. (paper)

  17. AXISYMMETRIC BENDING OF TWO-DIRECTIONAL FUNCTIONALLY GRADED CIRCULAR AND ANNULAR PLATES

    Institute of Scientific and Technical Information of China (English)

    Guojun Nie; Zheng Zhong

    2007-01-01

    Assuming the material properties varying with an exponential law both in the thickness and radial directions, axisymmetric bending of two-directional functionally graded circular and annular plates is studied using the semi-analytical numerical method in this paper. The deflections and stresses of the plates are presented. Numerical results show the well accuracy and convergence of the method. Compared with the finite element method, the semi-analytical numerical method is with great advantage in the computational efficiency. Moreover, study on axisymmetric bending of two-directional functionally graded annular plate shows that such plates have better performance than those made of isotropic homogeneous materials or one-directional functionally graded materials. Two-directional functionally graded material is a potential alternative to the one-directional functionally graded material. And the integrated design of materials and structures can really be achieved in two-directional functionally graded materials.

  18. Fabrication, Characterization and Modeling of Functionally Graded Materials

    Science.gov (United States)

    Lee, Po-Hua

    In the past few decades, a number of theoretical and experimental studies for design, fabrication and performance analysis of solar panel systems (photovoltaic/thermal systems) have been documented. The existing literature shows that the use of solar energy provides a promising solution to alleviate the shortage of natural resources and the environmental pollution associated with electricity generation. A hybrid solar panel has been invented to integrate photovoltaic (PV) cells onto a substrate through a functionally graded material (FGM) with water tubes cast inside, through which water flow serves as both a heat sink and a solar heat collector. Due to the unique and graded material properties of FGMs, this novel design not only supplies efficient thermal harvest and electrical production, but also provides benefits such as structural integrity and material efficiency. In this work, a sedimentation method has been used to fabricate aluminum (Al) and high-density polyethylene (HDPE) FGMs. The size effect of aluminum powder on the material gradation along the depth direction is investigated. Aluminum powder or the mixture of Al and HDPE powder is thoroughly mixed and uniformly dispersed in ethanol and then subjected to sedimentation. During the sedimentation process, the concentration of Al and HDPE particles temporally and spatially changes in the depth direction due to the non-uniform motion of particles; this change further affects the effective viscosity of the suspension and thus changes the drag force of particles. A Stokes' law based model is developed to simulate the sedimentation process, demonstrate the effect of manufacturing parameters on sedimentation, and predict the graded microstructure of deposition in the depth direction. In order to improve the modeling for sedimentation behavior of particles, the Eshelby's equivalent inclusion method (EIM) is presented to determine the interaction between particles, which is not considered in a Stokes' law based

  19. Thermal post-bunkling analyses of functionally graded material rod

    Institute of Scientific and Technical Information of China (English)

    ZHAO Feng-qun; WANG Zhong-min; LIU Hong-zhao

    2007-01-01

    The non-linear governing differential equations of immovably simply supported functionally graded material (FGM) rod subjected to thermal loads were derived.The thermal post-buckling behaviors of FGM rod made of ZrO2 and Ti-6A1-4Vwere analyzed by shooting method. Firstly, the thermal post-buckling equilibrium paths of the FGM rod with different gradient index in the uniform temperature field were plotted,and compared with the behaviors of the homogeneous rods made of ZrO2 and Ti-6A1-4V materials, respectively. For given value of end rotation angles, the influence of gradient index on the thermal post-buckling behaviors of FGM rod was discussed. Secondly, the thermal post-buckling characteristics of the FGM rod were analyzed when the temperature difference parameter is changed while the bottom temperature parameter remains constant, and when the bottom temperature parameter is changed while the temperature difference parameter remains constant, and compared with the characteristics of the two homogeneous material rods.

  20. Optimum weight design of functionally graded material gears

    Science.gov (United States)

    Jing, Shikai; Zhang, He; Zhou, Jingtao; Song, Guohua

    2015-11-01

    Traditional gear weight optimization methods consider gear tooth number, module, face width or other dimension parameters of gear as design variables. However, due to the complicated form and geometric features peculiar to the gear, there will be large amounts of design parameters in gear design, and the influences of gear parameters changing on gear trains, transmission system and the whole equipment have to be taken into account, which increases the complexity of optimization problem. This paper puts forward to apply functionally graded materials (FGMs) to gears and then conduct the optimization. According to the force situation of gears, the material distribution form of FGM gears is determined. Then based on the performance parameters analysis of FGMs and the practical working demands for gears, a multi-objective optimization model is formed. Finally by using the goal driven optimization (GDO) method, the optimal material distribution is achieved, which makes gear weight and the maximum deformation be minimum and the maximum bending stress do not exceed the allowable stress. As an example, the applying of FGM to automotive transmission gear is conducted to illustrate the optimization design process and the result shows that under the condition of keeping the normal working performance of gear, the method achieves in greatly reducing the gear weight. This research proposes a FGM gears design method that is able to largely reduce the weight of gears by optimizing the microscopic material parameters instead of changing the macroscopic dimension parameters of gears, which reduces the complexity of gear weight optimization problem.

  1. Fabrication and Microstructure of W/Cu Functionally Graded Material

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    W/Cu functionally gradient material (FGM) has excellent mech anical properties since it can effectively relax interlayer thermal st resses caused by the mismatch between their thermal expansion coeffici ents. W/Cu FGM combines the advantages of tungsten such as high meltin g point and service strength, with heat conductivity and plasticity of copper at room temperature. Thus it demonstrates satisfactory heat co rrosion and thermal shock resistance and will be a promising candidate as divertor component in thermonuclear device. Owing to the dramatic difference of melting point between tungsten and copper, conventional processes meet great difficulties in fabricating this kind of FGMs. A new approach termed graded sintering under ultra-high pressure (GSUHP) is proposed, with which a near 96% relative density of W/Cu FGM that contains a full distribution spectrum (0€?00%W) has been successfully fabricated. Suitable amount of transition metals (such as nickel, zir conium, vanadium) is employed as additives to activate tungsten's sint ering, enhance phase wettability and bonding strength between W and Cu . Densification effects of different layer of FGM were investigated. M icrostructure morphology and interface elements distribution were obse rved and analyzed. The thermal shock performance of W/Cu FGM was also preliminarily tested.

  2. Residual stress analysis of metal/ceramic functionally graded materials

    International Nuclear Information System (INIS)

    It is very difficult to join a metal and a ceramic film directly, because the difference in their coefficients of thermal expansion is so large that cracks may occur in the film or a delamination may occur in an interface. A functionally graded material (FGM) is usual to relax an abrupt change in mechanical and/or physical properties at an interface of joining. We prepared the Fe/Al2O3 FGM consisting five layers from iron to Al2O3 by spark plasma sintering (SPS). Residual stresses in each layer of FGM were measured by RESA in order to investigate the best production condition of FGM. The following results were obtained from the residual stress measurement in FGM.1. Residual stresses in all parts of Fe were tensile and increased with decreasing the volume fraction of Fe.2. Residual stresses in all parts of Al2O3 were compression and increased with decreasing the volume fraction of Al2O3. The difference in an average internal stress was large in the part of Fe 20%-Al2O3 80%. (author)

  3. Fabrication of Mo-Ti functionally graded material

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    Molybdenum alloys and titanium alloys were sintered at 1473K for 1 h under a pressure of 30 MPa. It was found that the addition of Al can increase evidently the relative density of sintered Mo-Fe alloys. The Fe-Al additives are also suitable for the sintering of titanium alloys, and the Mo alloy and Ti alloy can be densified concurrently with the same additives 3 % Fe-1.5 % Al. The experimental results also showed that during the sintering of Mo-Ti alloys the Fe-Al sintering aids promoted the formation of Mo-Ti solid solution, but the solid solution reaction occurred at the low sintering temperature of 1 473 K is inadequate. Finally, Mo-Ti system functionally graded material has been successfully fabricated. Its density changed gradually from 9.52 g/ cm3 to 4.48 g/cm3 in thickness direction. Such a material can be used in dynamic high-pressure technology.

  4. The modified couple stress functionally graded Timoshenko beam formulation

    International Nuclear Information System (INIS)

    In this paper, a size-dependent formulation is presented for Timoshenko beams made of a functionally graded material (FGM). The formulation is developed on the basis of the modified couple stress theory. The modified couple stress theory is a non-classic continuum theory capable to capture the small-scale size effects in the mechanical behavior of structures. The beam properties are assumed to vary through the thickness of the beam. The governing differential equations of motion are derived for the proposed modified couple-stress FG Timoshenko beam. The generally valid closed-form analytic expressions are obtained for the static response parameters. As case studies, the static and free vibration of the new model are respectively investigated for FG cantilever and FG simply supported beams in which properties are varying according to a power law. The results indicate that modeling beams on the basis of the couple stress theory causes more stiffness than modeling based on the classical continuum theory, such that for beams with small thickness, a significant difference between the results of these two theories is observed.

  5. ANALYSIS OF BAMBOO AS A FUNCTIONALLY GRADED MATERIAL

    Directory of Open Access Journals (Sweden)

    G. LOKESHA

    2014-09-01

    Full Text Available Bamboo is an optimized natural composite that exploits the concept of Functionally Graded Material (FGM. Biological structures such as bamboo have complicated micro-structural shapes and material distribution, and thus the use of numerical methods such as finite element method can be a useful tool for understanding the mechanical behavior of these materials. This paper explores techniques such as finite element method to investigate the structural behavior of bamboo. Two-dimensional models of bamboo cells were built and simulated under tensile load, compression load and bending load cases, using ANSYS 12.1 version with two material options, one with isotropic material properties (averaged Young’s modulus and the second with FGM properties (spatially varying Young’s modulus. In this study the stress obtained from FGM model are much higher than those obtained from Isotropic material model and the maximum stresses are noted at the outer diameter. This is due to the fact that the higher stiffness of that fiber-dense region and also the stress redistribution through the bamboo wall.

  6. Fracture of functionally graded materials: application to hydrided zircaloy

    International Nuclear Information System (INIS)

    This thesis is devoted to the dynamic fracture of functionally graded materials. More particularly, it deals with the toughness of nuclear cladding at high burnup submitted to transient loading. The fracture is studied at local scale using cohesive zone model in a multi body approach. Cohesive zone models include frictional contact to take into account mixed mode fracture. Non smooth dynamics problems are treated within the Non-Smooth Contact Dynamics framework. A multi scale study is necessary because of the dimension of the clad. At microscopic scale, the effective properties of surface law, between each body, are obtained by periodic numerical homogenization. A two fields Finite Element formulation is so written. An extended formulation of the NSCD framework is obtained. The associated software allows to simulate, in finite deformation, from the crack initiation to post-fracture behavior in heterogeneous materials. At microscopic scale, random RVE calculations are made to determine effective properties. At macroscopic scale, calculations of part of clad are made to determine the role of the mean hydrogen concentration and gradient of hydrogen parameters in the toughness of the clad under dynamic loading. (author)

  7. Manufacturing technique and performance of functionally graded concrete segment in shield tunnel

    Institute of Scientific and Technical Information of China (English)

    Baoguo MA; Dinghua ZOU; Li XU

    2009-01-01

    The quality of segment is very important to theservice life of shield tunnel. Concerning the complex engineering environment of the Wuhan Yangtze River Shield Tunnel, the principle of functionally graded materials was introduced to design and produce the functionally graded concrete segment (FGCS). Its key manufacturing technique was proposed and its perfor-mance was tested.

  8. Optimal Design of Functionally Graded Metallic Foam Insulations

    Science.gov (United States)

    Haftka, Raphael T.; Sankar, Bhavani; Venkataraman, Satchi; Zhu, Huadong

    2002-01-01

    The focus of our work has been on developing an insight into the physics that govern the optimum design of thermal insulation for use in thermal protection systems of launch vehicle. Of particular interest was to obtain optimality criteria for designing foam insulations that have density (or porosity) distributions through the thickness for optimum thermal performance. We investigate the optimum design of functionally graded thermal insulation for steady state heat transfer through the foam. We showed that the heat transfer in the foam has competing modes, of radiation and conduction. The problem assumed a fixed inside temperature of 400 K and varied the aerodynamic surface heating on the outside surface from 0.2 to 1.0 MW/sq m. The thermal insulation develops a high temperature gradient through the thickness. Investigation of the model developed for heat conduction in foams showed that at high temperatures (as on outside wall) intracellular radiation dominates the heat transfer in the foam. Minimizing radiation requires reducing the pore size, which increases the density of the foam. At low temperatures (as on the inside wall), intracellular conduction (of the metal and air) dominates the heat transfer. Minimizing conduction requires increasing the pore size. This indicated that for every temperature there was an optimum value of density that minimized the heat transfer coefficient. Two optimization studies were performed. One was to minimize the heat transmitted though a fixed thickness insulation by varying density profiles. The second was to obtain the minimum mass insulation for specified thickness. Analytical optimality criteria were derived for the cases considered. The optimality condition for minimum heat transfer required that at each temperature we find the density that minimizes the heat transfer coefficient. Once a relationship between the optimum heat transfer coefficient and the temperature was found, the design problem reduced to the solution of a

  9. Technology Tips: Two Useful Functions for Excel Grade Books

    Science.gov (United States)

    Lobo, Glen E.

    2006-01-01

    The topic of this month's department is writing macros in Excel. The examples given are of use to teachers who maintain their grade books in Excel, and show, for example, how to drop the lowest or choose the highest scores from a student's record. The Surfing Note cites a collection of online tools and resources for professional development…

  10. Application of ANFIS for analytical modeling of tensile strength of functionally graded steels

    Directory of Open Access Journals (Sweden)

    Ali Nazari

    2012-06-01

    Full Text Available In the present study, the tensile strength of ferritic and austenitic functionally graded steels produced by electroslag remelting has been modeled. To produce functionally graded steels, two slices of plain carbon steel and austenitic stainless steels were spot welded and used as electroslag remelting electrode. Functionally graded steel containing graded layers of ferrite and austenite may be fabricated via diffusion of alloying elements during remelting stage. Vickers microhardness profile of the specimen has been obtained experimentally and modeled with adaptive network-based fuzzy inference systems (ANFIS. To build the model for graded ferritic and austenitic steels, training, testing and validation using respectively 174 and 120 experimental data were conducted. According to the input parameters, in the ANFIS model, the Vickers microhardness of each layer was predicted. A good fit equation which correlates the Vickers microhardness of each layer to its corresponding chemical composition was achieved by the optimized network for both ferritic and austenitic graded steels. Afterwards; the Vickers microhardness of each layer in functionally graded steels was related to the yield stress of the corresponding layer and by assuming Holloman relation for stress-strain curve of each layer, they were acquired. Finally, by applying the rule of mixtures, tensile strength of functionally graded steels configuration was found through a numerical method. The obtained results from the proposed model are in good agreement with those acquired from the experiments.

  11. Effect of Layers Position on Fracture Toughness of Functionally Graded Steels in Crack Divider Configuration

    Institute of Scientific and Technical Information of China (English)

    Ali Nazari; Jamshid Aghazadeh Mohandesi; Shadi Riahi

    2011-01-01

    In the present study, fracture toughness of functionally graded steels in crack divider configuration has been modeled. By utilizing plain carbon and austenitic stainless steels slices with various thicknesses and arrangements as electroslag remelting electrodes, functionally graded steels were produced. The fracture toughness of the functionally graded steels in crack divider configuration has been found to depend on the composites' type together with the volume fraction and the position of the containing phases. According to the area under stress-strain curve of each layer in the functionally graded steels, a mathematical model has been presented for predicting fracture toughness of composites by using the rule of mixtures. The fracture toughness of each layer has been modified according to the position of that layer where for the edge layers, net plane stress condition was supposed and for the central layers, net plane strain condition was presumed. There is a good agreement between experimental results and those acquired from the analytical model.

  12. Functionally Graded Polyimide Nanocomposite Foams for Ablative and Inflatable/Flexible/Deplorable Structures Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The objective of the proposed research is to develop functionally graded polyimide foams as light-weight, high performance thermal protection systems (TPS) for...

  13. Stress and Strain Analysis of Functionally Graded Rectangular Plate with Exponentially Varying Properties

    OpenAIRE

    Amin Hadi; Abbas Rastgoo; Daneshmehr, A. R.; Farshad Ehsani

    2013-01-01

    The bending of rectangular plate made of functionally graded material (FGM) is investigated by using three-dimensional elasticity theory. The governing equations obtained here are solved with static analysis considering the types of plates, which properties varying exponentially along direction. The value of Poisson’s ratio has been taken as a constant. The influence of different functionally graded variation on the stress and displacement fields was studied through a numerical example. The ...

  14. Optimisation of energy absorbing liner for equestrian helmets. Part II: Functionally graded foam liner

    OpenAIRE

    Cui, Liang; Forero Rueda, Manuel A.; Gilchrist, M. D.

    2009-01-01

    The energy absorbing liner of safety helmets was optimised using finite element modelling. In this present paper, a functionally graded foam (FGF) liner was modelled, while keeping the average liner density the same as in a corresponding reference single uniform density liner model. Use of a functionally graded foam liner would eliminate issues regarding delamination and crack propagation between interfaces of different density layers which could arise in liners with discrete density variatio...

  15. Sound symbolic naming of novel objects is a graded function.

    Science.gov (United States)

    Thompson, Patrick D; Estes, Zachary

    2011-12-01

    Although linguistic traditions of the last century assumed that there is no link between sound and meaning (i.e., arbitrariness), recent research has established a nonarbitrary relation between sound and meaning (i.e., sound symbolism). For example, some sounds (e.g., /u/ as in took) suggest bigness whereas others (e.g., /i/ as in tiny) suggest smallness. We tested whether sound symbolism only marks contrasts (e.g., small versus big things) or whether it marks object properties in a graded manner (e.g., small, medium, and large things). In two experiments, participants viewed novel objects (i.e., greebles) of varying size and chose the most appropriate name for each object from a list of visually or auditorily presented nonwords that varied incrementally in the number of "large" and "small" phonemes. For instance, "wodolo" contains all large-sounding phonemes, whereas "kitete" contains all small-sounding phonemes. Participants' choices revealed a graded relationship between sound and size: The size of the object linearly predicted the number of large-sounding phonemes in its preferred name. That is, small, medium, and large objects elicited names with increasing numbers of large-sounding phonemes. The results are discussed in relation to cross-modal processing, gesture, and vocal pitch. PMID:21895561

  16. Value functions on simple algebras, and associated graded rings

    CERN Document Server

    Tignol, Jean-Pierre

    2015-01-01

    This monograph is the first book-length treatment of valuation theory on finite-dimensional division algebras, a subject of active and substantial research over the last forty years. Its development was spurred in the last decades of the twentieth century by important advances such as Amitsur's construction of noncrossed products and Platonov's solution of the Tannaka-Artin problem. This study is particularly timely because it approaches the subject from the perspective of associated graded structures. This new approach has been developed by the authors in the last few years and has significantly clarified the theory. Various constructions of division algebras are obtained as applications of the theory, such as noncrossed products and indecomposable algebras. In addition, the use of valuation theory in reduced Whitehead group calculations (after Hazrat and Wadsworth) and in essential dimension computations (after Baek and Merkurjev) is showcased. The intended audience consists of graduate students and researc...

  17. Fatigue behavior of functionally graded steel produced by electro-slag remelting

    International Nuclear Information System (INIS)

    The present study attempts to investigate the fatigue behavior of functionally graded steel (FGS) produced through electroslag remelting (ESR) process. To produce FGSs, two different slices of plain carbon steel and austenitic stainless steel were welded and used as ESR's electrode. Some of alloying elements in austenitic stainless steel, such as Nickel and Chromium, as well as carbon in plain carbon steel may be replaced during remelting stage; graded layers (austenite and martensite layers) may also be fabricated. Vickers micro-hardness test and scanning electron microscopy (SEM) of FGS were performed and variations in hardness and microstructure were observed. SEM images exhibited multi-phase graded steel. The rotating bending fatigue test was performed on specimens. The fatigue test results showed improvement in fatigue limit of FGS in comparison with that of its ingredients. SEM's images of fatigue fracture surfaces in FGS showed deviation and branching in crack propagation when crack propagates from graded austenite to graded martensite phase

  18. An investigation on thermal residual stresses in a cylindrical functionally graded WC–Co component

    International Nuclear Information System (INIS)

    The thermal residual stress distribution in a functionally graded cemented tungsten carbide (FG WC–Co) hollow cylinder was examined with an emphasis on the effects of key variables, such as gradient profile and gradient thickness on the magnitude and distribution of the stress field. An analytical direct solution based on solving the governing equations of a cylinder composed of a uniform inner core and a functionally graded outer shell was developed, considering the cylindrical compound as two separate elements: a homogeneous cylinder and a functionally graded shell. Through the graded shell, material properties such as the modulus of elasticity and the coefficient of thermal expansion (CTE), except Poisson's ratio, were considered to vary as a power function of the radius, and proper mechanical boundary conditions were imposed at the interface of the two cylinders. Practical values for the two variables, gradient profile and gradient thickness, were evaluated in the mathematical solution for the FG WC–Co compound, and their effects on the stress distribution were studied. An examination of different gradient profiles showed that with excess Co content in the graded region, compressive radial stresses were created, while with decreasing Co content through the graded region tensile stresses were generated at the interface. The effect of gradient thickness was shown to have a greater effect on radial stress, compared to hoop stress, and increasing the gradient thickness significantly increased the radial stress magnitude.

  19. An investigation on thermal residual stresses in a cylindrical functionally graded WC-Co component

    Energy Technology Data Exchange (ETDEWEB)

    Tahvilian, L. [Metallurgical Engineering, University of Utah, 135 South 1460 East, Salt Lake City, UT 84112 (United States); Fang, Z. Zak, E-mail: zak.fang@utah.edu [Metallurgical Engineering, University of Utah, 135 South 1460 East, Salt Lake City, UT 84112 (United States)

    2012-11-15

    The thermal residual stress distribution in a functionally graded cemented tungsten carbide (FG WC-Co) hollow cylinder was examined with an emphasis on the effects of key variables, such as gradient profile and gradient thickness on the magnitude and distribution of the stress field. An analytical direct solution based on solving the governing equations of a cylinder composed of a uniform inner core and a functionally graded outer shell was developed, considering the cylindrical compound as two separate elements: a homogeneous cylinder and a functionally graded shell. Through the graded shell, material properties such as the modulus of elasticity and the coefficient of thermal expansion (CTE), except Poisson's ratio, were considered to vary as a power function of the radius, and proper mechanical boundary conditions were imposed at the interface of the two cylinders. Practical values for the two variables, gradient profile and gradient thickness, were evaluated in the mathematical solution for the FG WC-Co compound, and their effects on the stress distribution were studied. An examination of different gradient profiles showed that with excess Co content in the graded region, compressive radial stresses were created, while with decreasing Co content through the graded region tensile stresses were generated at the interface. The effect of gradient thickness was shown to have a greater effect on radial stress, compared to hoop stress, and increasing the gradient thickness significantly increased the radial stress magnitude.

  20. Fabrication of Al-W Functionally Graded Impact Material via Vacuum Hot-Pressing Sintering Method

    International Nuclear Information System (INIS)

    Dense graded material as a type of functionally graded material (FGM) changes its wave impedance gradually along the thickness direction. In this investigation, Al-W functionally graded material was fabricated via vacuum hot-pressing sintering method (VHPS). The results showed that densified Al-W composite was fabricated at 550°C-300MPa-120min which the relative density was higher than 98.5% without intermetallic compounds. The density graded material of Al-W FGM was attained at the optimized parameters which the component of Al was from 10% to 100%. The micro structure of Al-W FGM composite indicated that W particles in single-layer composite were distributed homogeneously. The density of each layer in Al-W FGM composite was consistent with the design value.

  1. Functionally Graded Interfaces: Role and Origin of Internal Electric Field and Modulated Electrical Response.

    Science.gov (United States)

    Maurya, Deepam; Zhou, Yuan; Chen, Bo; Kang, Min-Gyu; Nguyen, Peter; Hudait, Mantu K; Priya, Shashank

    2015-10-14

    We report the tunable electrical response in functionally graded interfaces in lead-free ferroelectric thin films. Multilayer thin film graded heterostructures were synthesized on platinized silicon substrate with oxide layers of varying thickness. Interestingly, the graded heterostructure thin films exhibited shift of the hysteresis loops on electric field and polarization axes depending upon the direction of an applied bias. A diode-like characteristics was observed in current-voltage behavior under forward and reverse bias. This modulated electrical behavior was attributed to the perturbed dynamics of charge carriers under internal bias (self-bias) generated due to the increased skewness of the potential wells. The cyclic sweeping of voltage further demonstrated memristor-like current-voltage behavior in functionally graded heterostructure devices. The presence of an internal bias assisted the generation of photocurrent by facilitating the separation of photogenerated charges. These novel findings provide opportunity to design new circuit components for the next generation of microelectronic device architectures. PMID:26378954

  2. Even low-grade inflammation impacts on small intestinal function

    OpenAIRE

    Peuhkuri, Katri; Vapaatalo, Heikki; Korpela, Riitta

    2010-01-01

    Independent of the cause and location, inflammation - even when minimal - has clear effects on gastrointestinal morphology and function. These result in altered digestion, absorption and barrier function. There is evidence of reduced villus height and crypt depth, increased permeability, as well as altered sugar and peptide absorption in the small intestine after induction of inflammation in experimental models, which is supported by some clinical data. Identification of inflammatory factors ...

  3. Prediction of the adhesive behavior of bio-inspired functionally graded materials against rough surfaces

    OpenAIRE

    Chen Peijian; Peng Juan; Zhao Yucheng; Gao Feng

    2014-01-01

    Roughness effect and adhesion properties are important characteristics to be accessed in the development of functionally graded materials for biological and biomimetic applications, particularly for the hierarchical composition in biomimetic gecko robot. A multi-asperities adhesion model to predict the adhesive forces is presented in this work. The effect of surface roughness and graded material properties, which significantly alter the adhesive strength between contact bodies, can be simulta...

  4. Fabrication of Al/Diamond Particles Functionally Graded Materials by Centrifugal Sintered-Casting Method

    International Nuclear Information System (INIS)

    The continuous graded structure of functionally graded materials (FGMs) can be created under a centrifugal force. Centrifugal sintered-casting (CSC) method, proposed by the authors, is one of the fabrication methods of FGM under centrifugal force. This method is a combination of the centrifugal sintering method and centrifugal casting method. In this study, Al/diamond particle FGM was fabricated by the proposed method.

  5. Fabrication of Al/Diamond Particles Functionally Graded Materials by Centrifugal Sintered-Casting Method

    Science.gov (United States)

    Watanabe, Yoshimi; Shibuya, Masafumi; Sato, Hisashi

    2013-03-01

    The continuous graded structure of functionally graded materials (FGMs) can be created under a centrifugal force. Centrifugal sintered-casting (CSC) method, proposed by the authors, is one of the fabrication methods of FGM under centrifugal force. This method is a combination of the centrifugal sintering method and centrifugal casting method. In this study, Al/diamond particle FGM was fabricated by the proposed method.

  6. Powder metallurgical fabrication of metal/ceramic functionally graded materials for high temperature use

    International Nuclear Information System (INIS)

    Powder metallurgical fabrication of metal/ceramic functionally graded material (FGM) has been described. The first part of this paper briefly shows the concept of FGM with the special reference to the large progress of research works on thermal barrier materials where the role of thermal stress relaxation function has been emphasized. Then, powder metallurgical processing of this type of FGM is reviewed on the basis of recent activities. Graded structures may be found in ordinary engineering materials from former days; however, if one has begun to tailor the intentional gradient of composition and/or microstructure in a material in order to achieve the desired functions and properties, the material shall possess the concept of Functionally Graded Material (FGM). The FGM has the great potential of applications in many fields by using gradient on chemical, biochemical, physical and mechanical properties. (author)

  7. Elastic and viscoelastic solutions to rotating functionally graded hollow and solid cylinders

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Analytical solutions to rotating functionally graded hollow and solid long cylinders are developed. Young's modulus and material density of the cylinder are as* sumed to vary exponentially in the radial direction, and Poisson's ratio is assumed to be constant. A unified governing equation is derived from the equilibrium equations, compat-ibility equation, deformation theory of elasticity and the stress-strain relationship. The governing second-order differential equation is solved in terms of a hypergeometric func-tion for the elastic deformation of rotating functionally graded cylinders. Dependence of stresses in the cylinder on the inhomogeneous parameters, geometry and boundary conditions is examined and discussed. The proposed solution is validated by comparing the results for rotating functionally graded hollow and solid cylinders with the results for rotating homogeneous isotropic cylinders. In addition, a viscoelastic solution to the rotating viscoelastic cylinder is presented, and dependence of stresses in hollow and solid cylinders on the time parameter is examined.

  8. Deflection control of functionally graded material beams with bonded piezoelectric sensors and actuators

    International Nuclear Information System (INIS)

    An analytical solution is developed for analysis of functionally graded material (FGM) beams containing two layers of piezoelectric material, used as sensor and actuator. The properties of FGM layer are functionally graded in the thickness direction according to the volume fraction power law distribution. The equations of motion are derived by using Hamilton's principle, based on the first-order shear deformation theory. By using a displacement potential function, and assumption of harmonic vibration, the equations of motion have been solved analytically. Finally, the effects of FGM constituent volume fraction in the peak responses for various volume fraction indexes have been graphically illustrated

  9. Finite element analysis of the dynamic behavior of radially polarized Functionally Graded Piezoelectric (FGP) structures

    Science.gov (United States)

    Kandasamy, Ramkumar; Cui, Fangsen

    2016-04-01

    In the traditional layered piezoelectric structures, high stress concentrations could cause the structural failure in interlayer surfaces due to repeated strain reversals. To overcome the performance limitations of these structures, the concept of Functionally Graded Materials (FGMs) has been introduced to improve the lifetime, integrity, and reliability of these structures. In this paper, the free and forced vibration of radially polarized Functionally Graded Piezoelectric (FGP) cylinders under different sets of loading are studied. Material properties such as piezoelectric, elastic and permittivity are assumed to change along its thickness, based on a specific gradation function. Four-parameter power law distribution is used to grade the volume fraction of the constituents comprising of PZT-5A and PZT-5H. Material property is assumed to be temperature dependent for a few numerical studies. The present modeling approach is validated by comparing the free and forced vibration of radially polarized Functionally Graded Piezoelectric (FGP) cylinders with those reported in the literature. The effects of material composition, loading and boundary conditions on the dynamic behavior of FGP cylinder are described. Since the modeling of functionally graded piezoelectric systems is challenging, the present study can help in the design and analysis of FGP cylinders.

  10. Fabrication and properties of axisymmetric WC/Co functionally graded hard metal via microwave sintering

    Energy Technology Data Exchange (ETDEWEB)

    Lin Wei; Bai Xinde; Ling Yunhan; Jiang Zuozhong; Xie Zhipeng [Dept. of Materials Science and Engineering, Tsinghua Univ., Beijing, BJ (China)

    2003-07-01

    To reduce the cost of fabrication and improve the product quality, microwave sintering of axisymmetric functionally graded WC/Co hard metals was explored in this paper. WC-Co green compacts with a discontinuously axisymmetrical laying distribution of Co (3-25wt%) were first molded by cold isostatic pressure (CIP) and then sintered by microwave (2.45 GHz) irradiation in an Ar atmosphere. Microstructural changes and hardness survey have been examined through SEM analysis, etc. It was found that the densification and mechanical properties of the gradient compact were strongly dependent on the temperature and time of microwave sintering. Crystal particles remained quite small. Heat activation of WC grains and selective heating of microwave have enhanced the metallurgical and mechanical properties of cemented WC/Co functionally graded hard metals. Based on this result, preparation of nano-structural WC/Co functionally graded cemented carbides by microwave sintering is more promising. (orig.)

  11. Progress of in-situ produced functionally graded hard materials (hardmetals and ceramics) for tool applications

    International Nuclear Information System (INIS)

    Hard together with tough has been long the goal of tool scientists and engineers. Coated tools combine high wear and high toughness together and have been successfully used today. However, the coating thickness is limited because of large different between substrate and coating, additional cost is need for coating processing (CVD or PVD), and furthermore, in some cases such as in mining applications coated tools are not suitable. Recently, the concept of Functionally graded materials (FGMs) has spread word-wide during the past four international symposiums held in Sendai, Japan (1990), San Francisco, USA (1992), Lausanne, Switzerland (1994) and Tsukuba, Japan (1996). The idea of graded compositions, microstructures and functions has attracted the attention of many scientists, researchers and engineers for its boundless scope in materials science and engineering. FGMs materials are usually prepared by sintering of pre-layered green powder compacts. This processing is not suitable for tool producers because of its complicated process and additional costs. By studying phase diagrams, phase stability, phase equilibria and metallurgical reactions during sintering, graded WC-Co hardmetals and graded sialon ceramics (Si3N4), with increased Co contents and increased β/α phase ratio inwards respectively, have been in-situ produced recently from homogenous powder compact. The properties (functions) vary gradually from surface to center (core) due to compositional graduations. The graded WC-Co hardmetals feature 3 zone structures and have been successfully used in industry. The graded sialon, ceramics are only recently fabricated by Austrian Research Center Seibersdorf first and characterize high wear α-Sialon surface and high tough β-sialon core. This work presents progress of the above mentioned functionally graded tool materials. (author)

  12. Emerging role of functional brain MRI in low-grade glioma surgery

    DEFF Research Database (Denmark)

    Friismose, Ancuta; Traise, Peter; Markovic, Ljubo;

    Learning objectives 1. To describe the use of functional MRI (fMRI) in cranial surgery planning for patients with low-grade gliomas (LGG). 2. To show the increasing importance of fMRI in the clinical setting. Background LGG include brain tumors classified by the World Health Organization as grade I...... and II. LGG typically affect younger, otherwise healthy individuals. Whereas previously the preferred management strategy of LGG was one of watchful expectation, there is now evidence supporting radical surgery as a means of preventing malignant transformation and ensuring precise tumor grading. FMRI...... can be used to map eloquent cortex areas, thus minimizing postoperative deficits and improving surgical performance. Findings and procedure details Patients diagnosed with low-grade gliomas located in eloquent brain areas undergo fMRI prior to surgery. The exams are performed on a 3T MR system...

  13. A functionally graded multilayer approach to the synthesis of boron containing ceramic thin films

    Science.gov (United States)

    Tavsanoglu, T.; Jeandin, M.; Addemir, O.; Yucel, O.

    2012-11-01

    Despite their excellent properties, adhesion problems are common for B4C and BCN thin films on different substrates when the film thickness exceeds about 500 nm. Three functionally graded multilayer designs; surface boronizing of the steel substrate before deposition (Boride underlayer/B4C), Ti/TiC/B4C and Ti/TiN/BCN structures were discussed in this study, to alleviate the adhesion problems. Cross-sectional FE-SEM examinations and elemental depth profiling by SIMS revealed the graded structure of the films. The elemental film composition measured by EPMA and the mechanical properties determined by nanoindentation demonstrated the graded chemical composition and the transition of the hardness and Young's modulus values between different layers respectively. The results demonstrated the possibility of growing well adherent boron containing ceramic coatings with thicknesses in the μm range by means of different graded underlayer designs.

  14. Stress analysis in a functionally graded disc under mechanical loads and a steady state temperature distribution

    Indian Academy of Sciences (India)

    Hasan Çallioğlu

    2011-02-01

    An analytical thermoelasticity solution for a disc made of functionally graded materials (FGMs) is presented. Infinitesimal deformation theory of elasticity and power law distribution for functional gradation are used in the solution procedure. Some relative results for the stress and displacement components along the radius are presented due to internal pressure, external pressure, centrifugal force and steady state temperature. From the results, it is found that the grading indexes play an important role in determining the thermomechanical responses of FG disc and in optimal design of these structures.

  15. Optimisation of energy absorbing liner for equestrian helmets. Part II: Functionally graded foam liner

    International Nuclear Information System (INIS)

    The energy absorbing liner of safety helmets was optimised using finite element modelling. In this present paper, a functionally graded foam (FGF) liner was modelled, while keeping the average liner density the same as in a corresponding reference single uniform density liner model. Use of a functionally graded foam liner would eliminate issues regarding delamination and crack propagation between interfaces of different density layers which could arise in liners with discrete density variations. As in our companion Part I paper [Forero Rueda MA, Cui L, Gilchrist MD. Optimisation of energy absorbing liner for equestrian helmets. Part I: Layered foam liner. Mater Des [submitted for publication

  16. Thermo-Elastic Analysis Of A Rotating Hollow Cylinder Made Of Arbitrary Functionally Graded Materials

    Science.gov (United States)

    Arefi, Mohammad; Nahas, Iman; Abedi, Majid

    2015-12-01

    Thermo-mechanical analysis of the functionally graded orthotropic rotating hollow structures, subjected to thermo-mechanical loadings is studied in this paper. The relations were derived for both plane strain and plane stress conditions as a cylinder and disk, respectively. Non homogeneity was considered arbitrary through thickness direction for all mechanical and thermal properties. The responses of the system including temperature distribution, radial displacement and radial and circumferential stresses were derived in the general state. As case study, power law gradation was assumed for functionally graded cylinder and the mentioned results were evaluated in terms of parameters of the system such as non-homogeneous index and angular velocity.

  17. Thermo-Elastic Analysis Of A Rotating Hollow Cylinder Made Of Arbitrary Functionally Graded Materials*

    Directory of Open Access Journals (Sweden)

    Arefi Mohammad

    2015-12-01

    Full Text Available Thermo-mechanical analysis of the functionally graded orthotropic rotating hollow structures, subjected to thermo-mechanical loadings is studied in this paper. The relations were derived for both plane strain and plane stress conditions as a cylinder and disk, respectively. Non homogeneity was considered arbitrary through thickness direction for all mechanical and thermal properties. The responses of the system including temperature distribution, radial displacement and radial and circumferential stresses were derived in the general state. As case study, power law gradation was assumed for functionally graded cylinder and the mentioned results were evaluated in terms of parameters of the system such as non-homogeneous index and angular velocity.

  18. Semi-Analytical Solution of Functionally Graded Circular Short Hollow Cylinder Subject to Transient Thermal Loading

    Directory of Open Access Journals (Sweden)

    Eskandari Jam Jafar

    2014-12-01

    Full Text Available In this paper, by using a semi-analytical solution based on multi-layered approach, the authors present the solutions of temperature, displacements, and transient thermal stresses in functionally graded circular hollow cylinders subjected to transient thermal boundary conditions. The cylinder has finite length and is subjected to axisymmetric thermal loads. It is assumed that the functionally graded circular hollow cylinder is composed of N fictitious layers and the properties of each layer are assumed to be homogeneous and isotropic. Time variations of the temperature, displacements, and stresses are obtained by employing series solving method for ordinary differential equation, Laplace transform techniques and a numerical Laplace inversion.

  19. Analysis, manufacture and characterization of Ni/Cu functionally graded structures

    International Nuclear Information System (INIS)

    Highlights: ► Functionally graded structures (FGSs) of nickel and copper can be manufactured. ► The hardness curve of FGS can be used for approximating the gradation function of elastic properties. ► The graded finite element approaches with great accuracy the FGS resonance frequencies obtained experimentally. -- Abstract: In this work, an experimental and numerical analysis and characterization of functionally graded structures (FGSs) is developed. Nickel (Ni) and copper (Cu) materials are used as basic materials in the numerical modeling and experimental characterization. For modeling, a MATLAB finite element code is developed, which allows simulation of harmonic and modal analysis considering the graded finite element formulation. For experimental characterization, Ni–Cu FGSs are manufactured by using spark plasma sintering technique. Hardness and Young’s modulus are found by using microindentation and ultrasonic measurements, respectively. The effective gradation of Ni/Cu FGS is addressed by means of optical microscopy, energy dispersive spectrometry, scanning electron microscopy and hardness testing. For the purpose of comparing modeling and experimental results, the hardness curve, along the gradation direction, is used for identifying the gradation profile; accordingly, the experimental hardness curve is used for approximating the Young’s modulus variation and the graded finite element modeling is used for verification. For the first two resonance frequency values, a difference smaller than 1% between simulated and experimental results is obtained.

  20. Nonlinear vibration of functionally graded circular cylindrical shells based on improved Donnell equations

    Science.gov (United States)

    Bich, Dao Huy; Xuan Nguyen, Nguyen

    2012-12-01

    In the present work, the study of the nonlinear vibration of a functionally graded cylindrical shell subjected to axial and transverse mechanical loads is presented. Material properties are graded in the thickness direction of the shell according to a simple power law distribution in terms of volume fractions of the material constituents. Governing equations are derived using improved Donnell shell theory ignoring the shallowness of cylindrical shells and kinematic nonlinearity is taken into consideration. One-term approximate solution is assumed to satisfy simply supported boundary conditions. The Galerkin method, the Volmir's assumption and fourth-order Runge-Kutta method are used for dynamical analysis of shells to give explicit expressions of natural frequencies, nonlinear frequency-amplitude relation and nonlinear dynamic responses. Numerical results show the effects of characteristics of functionally graded materials, pre-loaded axial compression and dimensional ratios on the dynamical behavior of shells. The proposed results are validated by comparing with those in the literature.

  1. Prediction of the adhesive behavior of bio-inspired functionally graded materials against rough surfaces

    Science.gov (United States)

    Peijian, Chen; Juan, Peng; Yucheng, Zhao; Feng, Gao

    2014-06-01

    Roughness effect and adhesion properties are important characteristics to be accessed in the development of functionally graded materials for biological and biomimetic applications, particularly for the hierarchical composition in biomimetic gecko robot. A multi-asperities adhesion model to predict the adhesive forces is presented in this work. The effect of surface roughness and graded material properties, which significantly alter the adhesive strength between contact bodies, can be simultaneously considered in the generalized model. It is found that proper interfacial strength can be controlled by adjusting surface roughness σ / R, graded exponent k and material parameter E*R / Δγ. The results should be helpful in the design of new biomimetic materials and useful in application of micro functional instruments.

  2. Prediction of the adhesive behavior of bio-inspired functionally graded materials against rough surfaces

    Directory of Open Access Journals (Sweden)

    Chen Peijian

    2014-06-01

    Full Text Available Roughness effect and adhesion properties are important characteristics to be accessed in the development of functionally graded materials for biological and biomimetic applications, particularly for the hierarchical composition in biomimetic gecko robot. A multi-asperities adhesion model to predict the adhesive forces is presented in this work. The effect of surface roughness and graded material properties, which significantly alter the adhesive strength between contact bodies, can be simultaneously considered in the generalized model. It is found that proper interfacial strength can be controlled by adjusting surface roughness σ / R, graded exponent k and material parameter E*R / Δγ. The results should be helpful in the design of new biomimetic materials and useful in application of micro functional instruments.

  3. Microwave synthesis and mechanical characterization of functionally graded material for applications in fusion devices

    Indian Academy of Sciences (India)

    Charu Lata Dube; Yashashri Patil; Shailesh Kanpara; Samir S Khirwadkar; Subhash C Kashyap

    2014-12-01

    Functionally graded tungsten–copper bimetallic compact with fine microstructure and good mechanical property has been synthesized by employing microwave heating method at a temperature of 800 °C and in a short processing time of 30 min. Scanning electron microscopy and energy dispersive X-ray analysis revealed the graded structure of synthesized sample. The fine microstructure of tungsten in each layer is caused by arrested grain growth because of the short sintering time. The overall relative density of the W/Cu functionally graded sample has reached 87% of the theoretical density. Vickers microhardness measurements, across the length of a compact, show increase in hardness value of the sample with the increase in tungsten content. The experimental hardness values match well with the theoretically calculated hardness values.

  4. Surface Wave Speed of Functionally Graded Magneto-Electro-Elastic Materials with Initial Stresses

    Directory of Open Access Journals (Sweden)

    Li Li

    2014-09-01

    Full Text Available The shear surface wave at the free traction surface of half- infinite functionally graded magneto-electro-elastic material with initial stress is investigated. The material parameters are assumed to vary ex- ponentially along the thickness direction, only. The velocity equations of shear surface wave are derived on the electrically or magnetically open circuit and short circuit boundary conditions, based on the equations of motion of the graded magneto-electro-elastic material with the initial stresses and the free traction boundary conditions. The dispersive curves are obtained numerically and the influences of the initial stresses and the material gradient index on the dispersive curves are discussed. The investigation provides a basis for the development of new functionally graded magneto-electro-elastic surface wave devices.

  5. Correlation of grading of pulmonary emphysema by computed tomography to pulmonary function

    International Nuclear Information System (INIS)

    We studied the CT findings of 17 emphysema patients with special reference to the extent of emphysematous changes. Characteristic CT findings were low-attenuation area (LAA) and vascular abnormality and the appearance of various images on CT. To assess the extent of emphysematous changes, we classified the CT images into 4 grades based on the distribution and size of LAAs. As the grades progressed, the distribution and size of LAAs became wider and larger and vascular abnormalities were clearly evident. Although this CT-grading is a semiquantitative method, it is simple to use and gives information on the approximate extent of disease. This CT-grading was also used to show pulmonary function. The RV/TLC and expiratory flow showed a tendency to be impaired in Grade IV and the diffusion capacity was impaired parallel to CT-grading. CT is able to demonstrate the presence and distribution of LAAs noninvasively. Therefore it is considered that CT is useful for clinical diagnosis and the assessment of the extent of pulmonary emphysema. (author)

  6. Recovery of Graded Index Profile of Planar Waveguide by Cubic Spline Function

    Institute of Scientific and Technical Information of China (English)

    YANG Yong; CHEN Xian-Feng; LIAO Wei-Jun; XIA Yu-Xing

    2007-01-01

    A method is proposed to recover the refractive index profile of graded waveguide from the effective indices by a cubic spline interpolation function. Numerical analysis of several typical index distributions show that the refractive index profile can be reconstructed closely to its exact profile by the presented interpolation model.

  7. Eighth Grade In-Service Teachers' Knowledge of Proportional Reasoning and Functions: A Secondary Data Analysis

    Science.gov (United States)

    Masters, Jessica

    2012-01-01

    A secondary data analysis was conducted using a large dataset from a study related to online professional development for eighth grade teachers of mathematics. Using this data, the paper provides a snapshot of the current state of teachers' knowledge related to proportional reasoning and functions. The paper also considers how teachers' knowledge…

  8. Functionally Graded Thermoelectric Material though One Step Band Gap and Dopant Engineering

    DEFF Research Database (Denmark)

    Jensen, Ellen Marie; Borup, Kasper Andersen; Cederkrantz, Daniel;

    gradients. It has previously been shown that a large functionally graded thermoelectric single crystal can be synthesized by the Czochralski method (1). Utilizing element gradients inherent to the Czochralski process we have synthesized a Ge1-xSix:B crystal with a continuously varying x, band gap, and...

  9. Sub-stoichiometric functionally graded titania fibres for water-splitting applications

    International Nuclear Information System (INIS)

    The photo–electro–chemical (PEC) splitting of water requires semiconductor materials with a minimum energy gap of 1.23 eV along with conduction and valence bands overlapping the oxidation of H2O and reduction of H+ respectively. This work overcomes the limitations of stoichiometric titania by manufacturing fine scale fibres that exhibit a compositional gradient of oxygen vacancies across the fibre length. In such a fibre configuration the fibre end that is chemically reduced to a relatively small extent performs as the photoanode and the oxygen vacancies enhance the absorption of light. The fibre end that is reduced the most consists of Magnéli phases and exhibits metallic electrical conductivity that enhances the electron–hole separation. The structure and composition of the functionally graded fibres, which were manufactured through extrusion, pressureless sintering and carbo-thermal reduction, are studied using XRD and electron microscopy. Electrochemical impedance spectroscopy measurements were performed in a three-electrode electrochemical system and showed that the oxygen vacancies in the functionally graded fibres affect the flat band potential and have increased carrier density. The efficiency of the system was evaluated with PEC measurements that shows higher efficiency for the functionally graded fibres compared to homogeneous TiO2 or Magnéli phase fibres. The functionally graded and fine scale fibres have the potential to be used as an array of active fibres for water splitting applications. (paper)

  10. Neonates with reduced neonatal lung function have systemic low-grade inflammation

    DEFF Research Database (Denmark)

    Chawes, Bo L.K.; Stokholm, Jakob; Bønnelykke, Klaus;

    2015-01-01

    14 days before, and asthmatic symptoms, as well as virus-induced wheezing, at any time before biomarker assessment at age 6 months did not affect the associations. Conclusion: Diminished neonatal lung function is associated with upregulated systemic inflammatory markers, such as hs-CRP.......Background: Children and adults with asthma and impaired lung function have been reported to have low-grade systemic inflammation, but it is unknown whether this inflammation starts before symptoms and in particular whether low-grade inflammation is present in asymptomatic neonates with reduced...... lung function. ObjectiveWe sought to investigate the possible association between neonatal lung function and biomarkers of systemic inflammation.  Methods: Plasma levels of high-sensitivity C-reactive protein (hs-CRP), IL-1β, IL-6, TNF-α, and CXCL8 (IL-8) were measured at age 6 months in 300 children...

  11. Functionally graded materials for orthopedic applications - an update on design and manufacturing.

    Science.gov (United States)

    Sola, Antonella; Bellucci, Devis; Cannillo, Valeria

    2016-01-01

    Functionally graded materials (FGMs) are innovative materials whose composition and/or microstructure gradually vary in space according to a designed law. As a result, also the properties gradually vary in space, so as to meet specific non-homogeneous service requirements without any abrupt interface at the macroscale. FGMs are emerging materials for orthopedic prostheses, since the functional gradient can be adapted to reproduce the local properties of the original bone, which helps to minimize the stress shielding effect and, at the same time, to reduce the shear stress between the implant and the surrounding bone tissue, two critical prerequisites for a longer lifespan of the graft. After a brief introduction to the origin of the FGM concept, the review surveys some representative examples of graded systems which are present in nature and, in particular, in the human body, with a focus on bone tissue. Then the rationale for using FGMs in orthopedic devices is discussed more in detail, taking into account both biological and biomechanical requirements. The core of the paper is dedicated to two fundamental topics, which are essential to benefit from the use of FGMs for orthopedic applications, namely (1) the computational tools for materials design and geometry optimization, and (2) the manufacturing techniques currently available to produce FGM-based grafts. This second part, in its turn, is structured to consider the production of functionally graded coatings (FGCs), of functionally graded 3D parts, and of special devices with a gradient in porosity (functionally graded scaffolds). The inspection of the literature on the argument clearly shows that the integration of design and manufacturing remains a critical step to overpass in order to achieve effective FGM-based implants. PMID:26757264

  12. Stresses and displacements in functionally graded materials of semi-infinite extent induced by rectangular loadings

    OpenAIRE

    Zhong-Qi Yue; Hong-Tian Xiao

    2012-01-01

    This paper presents the stress and displacement fields in a functionally graded material (FGM) caused by a load. The FGM is a graded material of Si3N4-based ceramics and is assumed to be of semi-infinite extent. The load is a distributed loading over a rectangular area that is parallel to the external surface of the FGM and either on its external surface or within its interior space. The point-load analytical solutions or so-called Yue’s solutions are used for the numerical integration over t...

  13. Functionally Graded Ceramics Fabricated with Side-by-Side Tape Casting for Use in Magnetic Refrigeration

    DEFF Research Database (Denmark)

    Bulatova, Regina; Bahl, Christian; Andersen, Kjeld Bøhm;

    2015-01-01

    Functionally graded ceramic tapes have been fabricated by a side-by-side tape casting technique. This study shows the possibility and describes the main principles of adjacent coflow of slurries resulting in formation of thin plates of graded ceramic material. Results showed that the small...... distinct identification of the interface region and analysing the degree of cross-interface diffusion, the isothermal entropy change was measured by a vibrating sample magnetometer as the magnetic transition temperature (Curie temperature) is very sensitive to the dopant level in ceramics. Also the purpose...

  14. Analysis of Sigmoid Functionally Graded Material (S-FGM) Nanoscale Plates Using the Nonlocal Elasticity Theory

    OpenAIRE

    Woo-Young Jung; Sung-Cheon Han

    2013-01-01

    Based on a nonlocal elasticity theory, a model for sigmoid functionally graded material (S-FGM) nanoscale plate with first-order shear deformation is studied. The material properties of S-FGM nanoscale plate are assumed to vary according to sigmoid function (two power law distribution) of the volume fraction of the constituents. Elastic theory of the sigmoid FGM (S-FGM) nanoscale plate is reformulated using the nonlocal differential constitutive relations of Eringen and first-order shear defo...

  15. Varied effects of shear correction on thermal vibration of functionally graded material shells

    OpenAIRE

    Hong, C. C.

    2014-01-01

    The effects of varied shear correction coefficient on the first-order transverse shear deformation result of functionally graded material (FGM) thick circular cylindrical shells under thermal vibration are investigated and computed by using the generalized differential quadrature method. The computed and varied values of shear correction coefficient are usually functions of FGM power law index and environment temperature. In the thermoelastic stress–strain relations, the simpler form stiffnes...

  16. Deposition and Characterization of HVOF Thermal Sprayed Functionally Graded Coatings Deposited onto a Lightweight Material

    Science.gov (United States)

    Hasan, M.; Stokes, J.; Looney, L.; Hashmi, M. S. J.

    2009-02-01

    There is a significant interest in lightweight materials (like aluminum, magnesium, titanium, and so on) containing a wear resistance coating, in such industries as the automotive industry, to replace heavy components with lighter parts in order to decrease vehicle weight and increase fuel efficiency. Functionally graded coatings, in which the composition, microstructure, and/or properties vary gradually from the bond coat to the top coat, may be applied to lightweight materials, not only to decrease weight, but also to enhance components mechanical properties by ensuring gradual microstructural (changes) together with lower residual stress. In the current work, aluminum/tool-steel functionally graded coatings were deposited onto lightweight aluminum substrates. The graded coatings were then characterized in terms of residual stress and hardness. Results show that residual stress increased with an increase in deposition thickness and a decrease in number of layers. However, the hardness also increased with an increase in deposition thickness and decrease in number of layers. Therefore, an engineer must compromise between the hardness and stress values while designing a functionally graded coating-substrate system.

  17. Thermomechanical vibration analysis of a functionally graded shell with flowing fluid

    International Nuclear Information System (INIS)

    This paper reports the results of an investigation into the vibration of functionally graded cylindrical shells with flowing fluid, embedded in an elastic medium, under mechanical and thermal loads. By considering rotary inertia, the first-order shear deformation theory (FSDT) and the fluid velocity potential, the dynamic equation of functionally graded cylindrical shells with flowing fluid is derived. Here, heat conduction equation along the thickness of the shell is applied to determine the temperature distribution and material properties are assumed to be graded distribution along the thickness direction according to a power-law in terms of the volume fractions of the constituents. The equations of eigenvalue problem are obtained by using a modal expansion method. In numerical examples, effects of material composition, thermal loading, static axial loading, flow velocity, medium stiffness and shell geometry parameters on the free vibration characteristics are described. The new features in this paper are helpful for the application and the design of functionally graded cylindrical shells containing fluid flow. (authors)

  18. Electro-mechanical response of functionally graded beams with imperfectly integrated surface piezoelectric layers

    Institute of Scientific and Technical Information of China (English)

    YAN; Wei; CHEN; Weiqiu

    2006-01-01

    The time-dependent behavior of a simply-supported functionally graded beam bonded with piezoelectric sensors and actuators is studied using the state-space method. The creep behavior of bonding adhesives between piezoelectric layers and beam is characterized by a Kelvin-Voigt viscoelastic model, which is practical in a high temperature circumstance. Both the host elastic functionally graded beam and the piezoelectric layers are orthotropic and in a state of plane stress, with the former being inhomogeneous along the thickness direction. A laminate model is employed to approximate the host beam. Moreover, the coupling effect between the elastic deformation and electric field in piezoelectric layers is considered. Results indicate that the viscoelastic property of interfacial adhesives has a significant effect on the function of bonded actuators and sensors with time elapsing.

  19. Free Vibration and Stability of Axially Functionally Graded Tapered Euler-Bernoulli Beams

    Directory of Open Access Journals (Sweden)

    Ahmad Shahba

    2011-01-01

    Full Text Available Structural analysis of axially functionally graded tapered Euler-Bernoulli beams is studied using finite element method. A beam element is proposed which takes advantage of the shape functions of homogeneous uniform beam elements. The effects of varying cross-sectional dimensions and mechanical properties of the functionally graded material are included in the evaluation of structural matrices. This method could be used for beam elements with any distributions of mass density and modulus of elasticity with arbitrarily varying cross-sectional area. Assuming polynomial distributions of modulus of elasticity and mass density, the competency of the element is examined in stability analysis, free longitudinal vibration and free transverse vibration of double tapered beams with different boundary conditions and the convergence rate of the element is then investigated.

  20. Exact solution and transient behavior for torsional vibration of functionally graded finite hollow cylinders

    Institute of Scientific and Technical Information of China (English)

    H.M.Wang; C.B.Liu; H.J.Ding

    2009-01-01

    Exact solutions are obtained for transient torsional responses of a finitely long, functionally graded hollow cylinder under three different end conditions, I.e. Free--free, free-fixed and fixed-fixed. The cylinder with its external surface fixed is subjected to a dynamic shearing stress at the internal surface. The material properties are assumed to vary in the radial direction in a power law form, while keep invariant in the axial direction. With expansion in the axial direction in terms of trigonometric series, the governing equations for the unknown functions about the radial coordinate r and time t are deduced. By applying the variable substitution technique, the superposition method and the separation of variables consecutively, series-form solutions of the equations are obtained. Natural frequencies and the transient torsional responses are finally discussed for a functionally graded finite hollow cylinder.

  1. Vibration analysis and transient response of a functionally graded piezoelectric curved beam with general boundary conditions

    Science.gov (United States)

    Su, Zhu; Jin, Guoyong; Ye, Tiangui

    2016-06-01

    The paper presents a unified solution for free and transient vibration analyses of a functionally graded piezoelectric curved beam with general boundary conditions within the framework of Timoshenko beam theory. The formulation is derived by means of the variational principle in conjunction with a modified Fourier series which consists of standard Fourier cosine series and supplemented functions. The mechanical and electrical properties of functionally graded piezoelectric materials (FGPMs) are assumed to vary continuously in the thickness direction and are estimated by Voigt’s rule of mixture. The convergence, accuracy and reliability of the present formulation are demonstrated by comparing the present solutions with those from the literature and finite element analysis. Numerous results for FGPM beams with different boundary conditions, geometrical parameters as well as material distributions are given. Moreover, forced vibration of the FGPM beams subjected to dynamic loads and general boundary conditions are also investigated.

  2. Free-edge stress analysis of functionally graded material layered biocomposite laminates.

    Science.gov (United States)

    Huang, Bin; Kim, Heung Soo

    2014-10-01

    A stress function based theory is proposed to obtain free-edge stress distributions for three-dimensional, orthotropic, linearly elastic rectangular biocomposite laminates with surface-bonded functionally graded materials (FGM). The assumed stress fields automatically satisfy the pointwise equilibrium equation, as well as traction-free and free edge boundary conditions. The complementary virtual work principle, followed by the general eigenvalue solution procedure, is used to obtain 3-D free edge stress states. A typical stacking sequence of composite laminate is used as numerical investigation with surface bonded FGMs. It is shown that with proper exponential factor of FGMs, the interlaminar stresses at the FGM layer interface can be reduced significantly, in return to prevent debonding of FGM layers. This approach can be useful in the design of functionally graded material layered biocomposite structures. PMID:25942808

  3. Tailoring vibration mode shapes using topology optimization and functionally graded material concepts

    International Nuclear Information System (INIS)

    Tailoring specified vibration modes is a requirement for designing piezoelectric devices aimed at dynamic-type applications. A technique for designing the shape of specified vibration modes is the topology optimization method (TOM) which finds an optimum material distribution inside a design domain to obtain a structure that vibrates according to specified eigenfrequencies and eigenmodes. Nevertheless, when the TOM is applied to dynamic problems, the well-known grayscale or intermediate material problem arises which can invalidate the post-processing of the optimal result. Thus, a more natural way for solving dynamic problems using TOM is to allow intermediate material values. This idea leads to the functionally graded material (FGM) concept. In fact, FGMs are materials whose properties and microstructure continuously change along a specific direction. Therefore, in this paper, an approach is presented for tailoring user-defined vibration modes, by applying the TOM and FGM concepts to design functionally graded piezoelectric transducers (FGPT) and non-piezoelectric structures (functionally graded structures—FGS) in order to achieve maximum and/or minimum vibration amplitudes at certain points of the structure, by simultaneously finding the topology and material gradation function. The optimization problem is solved by using sequential linear programming. Two-dimensional results are presented to illustrate the method

  4. Mothers' depressive symptoms and children's cognitive and social agency: Predicting first-grade cognitive functioning.

    Science.gov (United States)

    Yan, Ni; Dix, Theodore

    2016-08-01

    Using data from the National Institute of Child Health and Human Development (NICHD) Study of Early Child Care and Youth Development (N = 1,364), the present study supports an agentic perspective; it demonstrates that mothers' depressive symptoms in infancy predict children's poor first-grade cognitive functioning because depressive symptoms predict children's low social and cognitive agency-low motivation to initiate social interaction and actively engage in activities. When mothers' depressive symptoms were high in infancy, children displayed poor first-grade cognitive functioning due to (a) tendencies to become socially withdrawn by 36 months and low in mastery motivation by 54 months and (b) tendencies for children's low agency to predict declines in mothers' sensitivity and cognitive stimulation. Findings suggest that mothers' depressive symptoms undermine cognitive development through bidirectional processes centered on children's low motivation to engage in social interaction and initiate and persist at everyday tasks. (PsycINFO Database Record PMID:27389834

  5. Hygrothermomagnetoelectroelastic analysis of a functionally graded magnetoelectroelastic hollow sphere resting on an elastic foundation

    International Nuclear Information System (INIS)

    Static behavior of a functionally graded magnetoelectroelastic hollow sphere subjected to hygrothermal loading in the spherically symmetric state is studied. The sphere could be rested on a Winkler elastic foundation on the inner and/or outer surfaces. It is assumed that the material properties obey a power law in the radial direction. Considering the axisymmetric heat conduction and moisture diffusion equations, temperature and moisture concentration distributions within the radius of the sphere are achieved. The governing coupled differential equations are exactly solved. Numerical examples are discussed in detail to show the significant influences of inhomogeneity index, hygrothermal loading, elastic foundation and electromagnetic boundary conditions on the static behavior of a functionally graded magnetoelectroelastic hollow sphere. (paper)

  6. Plane strain analytical solutions for a functionally graded elastic-plastic pressurized tube

    International Nuclear Information System (INIS)

    Plane strain analytical solutions to functionally graded elastic and elastic-plastic pressurized tube problems are obtained in the framework of small deformation theory. The modulus of elasticity and the uniaxial yield limit of the tube material are assumed to vary radially according to two parametric parabolic forms. The analytical plastic model is based on Tresca's yield criterion, its associated flow rule and ideally plastic material behaviour. Elastic, partially plastic and fully plastic stress states are investigated. It is shown that the elastoplastic response of the functionally graded pressurized tube is affected significantly by the material nonhomogeneity. Different modes of plasticization may take place unlike the homogeneous case. It is also shown mathematically that the nonhomogeneous elastoplastic solution presented here reduces to that of a homogeneous one by appropriate choice of the material parameters

  7. Magnetothermoelastic stress and perturbation of magnetic field vector in a functionally graded hollow sphere

    Energy Technology Data Exchange (ETDEWEB)

    Ali, Ghorbanpour Arani; Arefmanesh, A. [University of Kashan, Department of Mechanical Engineering, Faculty of Engineering, Kashan (Iran); Salari, M.; Khademizadeh, H. [Isfahan University of Technology, Department of Mechanical Engineering, Isfahan (Iran)

    2010-02-15

    In this article, a closed-form solution for one-dimensional magnetothermoelastic problem in a functionally graded material (FGM) hollow sphere placed in uniform magnetic and temperature fields subjected to an internal pressure is obtained using the infinitesimal theory of magnetothermoelasticity. Hyper-geometric functions are employed to solve the governing equation. The material properties through the graded direction are assumed to be nonlinear with an exponential distribution. The nonhomogeneity of the material in the radial direction is assumed to be exponential. The temperature, displacement and stress fields and the perturbation of magnetic field vector are determined and compared with those of the homogeneous case. Hence, the effect of inhomogeneity on the stresses and the perturbation of magnetic field vector distribution are demonstrated. The results of this study are applicable for designing optimum FGM hollow spheres. (orig.)

  8. Fundamentals of liquid phase for modern cermets and functionally graded cemented carbonitrides (FGCC)

    International Nuclear Information System (INIS)

    Metallurgical reactions and microstructure developments during sintering of modern cermets and functionally graded cemented carbonitrides (FGCC) were investigated by modern thermal and analytical methods such as mass spectrometer (MS), differential thermal analysis (DTA), differential scanning calorimeter (DSC), dilatometer (DIL), microscopy and analytical electronic microscopy with energy dispersive spectrometer (EDS). The complex phase reactions and phase equilibrium in the multi-component system Ti/Mo/W/Ta/Nb/C,N-Co/Ni were studied. The melting behaviors in the systems of TiC-WC/MoC-Ni/Co, TiC-TiN-WC-Co and TiCN-TaC-WC-Co have been established. By better understanding of the mechanisms that govern the sintering processing and metallurgical reactions, new cermets and different types of functionally graded cemented carbonitrides (FGCC) with desired microstructures and properties were developed and fabricated. (author)

  9. Effect of partial elastic foundation on free vibration of fluid-filled functionally graded cylindrical shells

    Science.gov (United States)

    Kim, Young-Wann

    2015-12-01

    The free vibration characteristics of fluid-filled functionally graded cylindrical shells buried partially in elastic foundations are investigated by an analytical method. The elastic foundation of partial axial and angular dimensions is represented by the Pasternak model. The motion of the shells is represented by the first-order shear deformation theory to account for rotary inertia and transverse shear strains. The functionally graded cylindrical shells are composed of stainless steel and silicon nitride. Material properties vary continuously through the thickness according to a power law distribution in terms of the volume fraction of the constituents. The governing equation is obtained using the Rayleigh-Ritz method and a variation approach. The fluid is described by the classical potential flow theory. Numerical examples are presented and compared with existing available results to validate the present method.

  10. Microstructure, mechanical properties, and biological response to functionally graded HA coatings

    International Nuclear Information System (INIS)

    Hydroxyapatite (HA) [Ca10(PO4)6(OH)2] is the primary mineral content, representing 43% by weight, of bone. Applying a thin layer of HA, to the surface of a metal implant, can promote osseointegration and increase the mechanical stability of the implant. In this study, a biocompatible coating comprising an HA film with functionally graded crystallinity is being deposited on a heated substrate in an Ion Beam Assisted Deposition (IBAD) system. The microstructure of the film was studied using Transmission Electron Microscopy techniques. Finally, initial cell adhesion and cell differentiation on the coating was evaluated using ATCC CRL 1486 human embryonic palatal mesenchymal cell, an osteoblast precursor cell line. The results have shown superior mechanical properties and biological response to the functionally graded HA film

  11. Microstructure, mechanical properties, and biological response to functionally graded HA coatings

    Energy Technology Data Exchange (ETDEWEB)

    Rabiei, Afsaneh [Department of Mechanical and Aerospace Engineering, North Carolina State University, 3211 Broughton Hall, 2601 Stinson Dr., Campus Box 7910, Raleigh, NC 27695-7910 (United States)]. E-mail: arabiei@eos.ncsu.edu; Blalock, Travis [Department of Mechanical and Aerospace Engineering, North Carolina State University, 3211 Broughton Hall, 2601 Stinson Dr., Campus Box 7910, Raleigh, NC 27695-7910 (United States); Thomas, Brent [Materials Science and Engineering, North Carolina State University, 911 Partners Way, Raleigh, NC 27695 (United States); Cuomo, Jerry [Materials Science and Engineering, North Carolina State University, 911 Partners Way, Raleigh, NC 27695 (United States); Yang, Y. [Biomedical Engineering and Orthopedic Surgery, University of Tennessee Health Science Center, 920 Madison Ave., Suite 1005, Memphis, TN 38163 (United States); Ong, Joo [Biomedical Engineering and Orthopedic Surgery, University of Tennessee Health Science Center, 920 Madison Ave., Suite 1005, Memphis, TN 38163 (United States)

    2007-04-15

    Hydroxyapatite (HA) [Ca{sub 10}(PO{sub 4}){sub 6}(OH){sub 2}] is the primary mineral content, representing 43% by weight, of bone. Applying a thin layer of HA, to the surface of a metal implant, can promote osseointegration and increase the mechanical stability of the implant. In this study, a biocompatible coating comprising an HA film with functionally graded crystallinity is being deposited on a heated substrate in an Ion Beam Assisted Deposition (IBAD) system. The microstructure of the film was studied using Transmission Electron Microscopy techniques. Finally, initial cell adhesion and cell differentiation on the coating was evaluated using ATCC CRL 1486 human embryonic palatal mesenchymal cell, an osteoblast precursor cell line. The results have shown superior mechanical properties and biological response to the functionally graded HA film.

  12. Methods of electrophoretic deposition for functionally graded porous nanostructures and systems thereof

    Energy Technology Data Exchange (ETDEWEB)

    Worsley, Marcus A; Baumann, Theodore F; Satcher, Joe H; Olson, Tammy Y; Kuntz, Joshua D; Rose, Klint A

    2015-03-03

    In one embodiment, an aerogel includes a layer of shaped particles having a particle packing density gradient in a thickness direction of the layer, wherein the shaped particles are characterized by being formed in an electrophoretic deposition (EPD) process using an impurity. In another embodiment, a method for forming a functionally graded porous nanostructure includes adding particles of an impurity and a solution to an EPD chamber, applying a voltage difference across the two electrodes of the EPD chamber to create an electric field in the EPD chamber, and depositing the material onto surfaces of the particles of the impurity to form shaped particles of the material. Other functionally graded materials and methods are described according to more embodiments.

  13. Preparation of Al/Si functionally graded materials using ultrasonic separation method

    OpenAIRE

    Zhang Zhongtao; Li Tingju; Yue Hongyun

    2008-01-01

    Functionally graded materials (FGM) have been widely used in many industries such as aerospace, energy and electronics. In this experimental study of fabricating FGM, an approach was developed to prepare Al/Si FGM using power ultrasonic separation method. Material sample with continuously changing composition and performance/properties was successfully produced. Results showed that the microstructure of the FGM sample transited, from its top to bottom, from the hypereutectic structure with a ...

  14. Sound radiation of a functionally graded material cylindrical shell in water by mobility method

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    Based on the fundamental dynamic equations of functionally graded material (FGM) cylindrical shell, this paper investigates the sound radiation of vibrational FGM shell in water by mobility method. This model takes into account the exterior fluid loading due to the sound press radiated by the FGM shell. The FGM cylindrical shell was excited by a harmonic line radial force uniformly distributing along the generator. The FGM shell equations of motion, the Helmholtz equation in the exterior fluid medium and th...

  15. Analysis of stress singularities at singular points of elastic solids made of functionally graded materials

    Science.gov (United States)

    Matveenko, V. P.; Fedorov, A. Yu.; Shardakov, I. N.

    2016-01-01

    The results of analytical and numerical investigations on estimating the character of the singularity of stresses in a vicinity of different variants of special points of the 2D elastic solids made of functionally graded materials (FGMs) are presented. The variant of construction by analytical methods in the polar system of coordinates is considered for eigensolutions in the flat wedges made of the FGM, the elastic properties of which are represented as power series in terms of the radial coordinate.

  16. Synthesis and microwave absorbing characteristics of functionally graded carbonyl iron/polyurethane composites

    OpenAIRE

    R. B. Yang; W. F. Liang; Wu, C.H.; Chen, C. C.

    2016-01-01

    Radar absorbing materials (RAMs) also known as microwave absorbers, which can absorb and dissipate incident electromagnetic wave, are widely used in the fields of radar-cross section reduction, electromagnetic interference (EMI) reduction and human health protection. In this study, the synthesis of functionally graded material (FGM) (CI/Polyurethane composites), which is fabricated with semi-sequentially varied composition along the thickness, is implemented with a genetic algorithm (GA) to o...

  17. Optimization of a functionally graded circular plate with inner rigid thin obstacles. II. Approximate problems

    Czech Academy of Sciences Publication Activity Database

    Hlaváček, Ivan; Lovíšek, J.

    2011-01-01

    Roč. 91, č. 12 (2011), s. 957-966. ISSN 0044-2267 R&D Projects: GA AV ČR(CZ) IAA100190803 Institutional research plan: CEZ:AV0Z10190503 Keywords : control of elliptic variational inequalities * functionally graded plates * optimal design of plates * finite element approximations Subject RIV: BA - General Mathematics Impact factor: 0.863, year: 2011 http://onlinelibrary.wiley.com/doi/10.1002/zamm.201000238/abstract

  18. An accurate higher order displacement model with shear and normal deformations effects for functionally graded plates

    Energy Technology Data Exchange (ETDEWEB)

    Jha, D.K., E-mail: dkjha@barc.gov.in [Civil Engineering Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India); Kant, Tarun [Department of Civil Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400 076 (India); Srinivas, K. [Civil Engineering Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Singh, R.K. [Reactor Safety Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India)

    2013-12-15

    Highlights: • We model through-thickness variation of material properties in functionally graded (FG) plates. • Effect of material grading index on deformations, stresses and natural frequency of FG plates is studied. • Effect of higher order terms in displacement models is studied for plate statics. • The benchmark solutions for the static analysis and free vibration of thick FG plates are presented. -- Abstract: Functionally graded materials (FGMs) are the potential candidates under consideration for designing the first wall of fusion reactors with a view to make best use of potential properties of available materials under severe thermo-mechanical loading conditions. A higher order shear and normal deformations plate theory is employed for stress and free vibration analyses of functionally graded (FG) elastic, rectangular, and simply (diaphragm) supported plates. Although FGMs are highly heterogeneous in nature, they are generally idealized as continua with mechanical properties changing smoothly with respect to spatial coordinates. The material properties of FG plates are assumed here to vary through thickness of plate in a continuous manner. Young's modulii and material densities are considered to be varying continuously in thickness direction according to volume fraction of constituents which are mathematically modeled here as exponential and power law functions. The effects of variation of material properties in terms of material gradation index on deformations, stresses and natural frequency of FG plates are investigated. The accuracy of present numerical solutions has been established with respect to exact three-dimensional (3D) elasticity solutions and the other models’ solutions available in literature.

  19. An evaluation of the stress intensity factor in functionally graded materials

    Czech Academy of Sciences Publication Activity Database

    Ševčík, Martin; Hutař, Pavel; Náhlík, Luboš; Knésl, Zdeněk

    2009-01-01

    Roč. 3, č. 2 (2009), s. 401-410. ISSN 1802-680X R&D Projects: GA ČR GD106/09/H035; GA ČR GC101/09/J027 Institutional research plan: CEZ:AV0Z20410507 Keywords : functionally graded material * power-law material change Subject RIV: JL - Materials Fatigue, Friction Mechanics

  20. High velocity oxy-fuel (HVOF) thermal spray deposition of functionally graded coatings

    OpenAIRE

    Mahbub, Hasan

    2005-01-01

    The present study investigates an innovative modification of a HVOF (High Velocity Oxy-Fuel) thermal spray process to produce functionally graded thick coatings. In order to deposit thick coatings, certain problems have to be overcome. More specifically these problems include minimizing residual stresses, which cause shape distortion in assprayed components. Residual stresses in coatings also lead to adhesion loss, interlaminar debonding, cracking or buckling and are particularly high where t...

  1. The method of fundamental solutions for transient heat conduction in functionally graded materials: some special cases

    Directory of Open Access Journals (Sweden)

    Mohammad Nili Ahmadabadi

    2014-05-01

    Full Text Available In this paper, the Method of Fundamental Solutions (MFS is extended to solve some special cases of the problem of transient heat conduction in functionally graded mate- rials. First, the problem is transformed to a heat equation with constant coecients using a suitable new transformation and then the MFS together with the Tikhonov regularization method is used to solve the resulting equation

  2. Microstructure-based modeling of elastic functionally graded materials: One dimensional case

    OpenAIRE

    Sharif-Khodaei, Zahra; Zeman, Jan

    2008-01-01

    Functionally graded materials (FGMs) are two-phase composites with continuously changing microstructure adapted to performance requirements. Traditionally, the overall behavior of FGMs has been determined using local averaging techniques or a given smooth variation of material properties. Although these models are computationally efficient, their validity and accuracy remain questionable, since a link with the underlying microstructure (including its randomness) is not clear. In this paper, w...

  3. Optimization of a functionally graded circular plate with inner rigid thin obstacles. I. Continuous problems

    Czech Academy of Sciences Publication Activity Database

    Hlaváček, Ivan; Lovíšek, J.

    2011-01-01

    Roč. 91, č. 9 (2011), s. 711-723. ISSN 0044-2267 R&D Projects: GA AV ČR(CZ) IAA100190803 Institutional research plan: CEZ:AV0Z10190503 Keywords : functionally graded plate * optimal design Subject RIV: BA - General Mathematics Impact factor: 0.863, year: 2011 http://onlinelibrary.wiley.com/doi/10.1002/zamm.201000119/abstract

  4. Theoretical analysis on bending behavior of function-ally graded composite beam crack-controlled by ultrahigh toughness cementitious composites

    Institute of Scientific and Technical Information of China (English)

    XU ShiLang; LI QingHua

    2009-01-01

    Ultrahigh toughness cementitious composites (UHTCC) obviously show strain hardening property under tensile or bending loading. The failure pattern of the UHTCC components exhibits multiple fine cracks under uniaxial tensile loading with prominent tensile strain capacity in excess of 3%, with merely 60 μm average crack width even corresponding to the ultimate tensile strain state. The approach adopted is based on the concept of functionally-graded concrete, where part of the concrete, which surrounds the main longitudinal reinforcement in a RC (reinforced concrete) member, is strategically replaced with UHTCC with excellent crack-controlling ability. Investigations on bending behavior of functionally-graded composite beam crack controlled by UHTCC has been carried out, including theo-retical analysis, experimental research on long composite beams without web reinforcement, validation and comparison between experimental and theoretical results, and analysis on crack control. In addi-tion to improving bearing capacity, the results indicate that functionally-graded composite beams using UHTCC has been found to be very effective in preventing corrosion-induced damage compared with RC beams. Therefore, durability and service life of the structure could be enhanced. This paper discusses the development of internal force and crack propagation during loading process, and presents analysis of the internal force in different stages, moment-curvature relationship from loading to damage and calculation of mid-span deflection and ductility index. In the end, the theoretical formulae have been validated by experimental results.

  5. Exact and numerical elastodynamic solutions for thick-walled functionally graded cylinders subjected to pressure shocks

    Energy Technology Data Exchange (ETDEWEB)

    Shariyat, M., E-mail: m_shariyat@yahoo.co [Faculty of Mechanical Engineering, K.N. Toosi University of Technology, Pardis Street, Molla-Sadra Avenue, Vanak Square, P.O. Box: 19395-1999, Tehran 19991 43344 (Iran, Islamic Republic of); Nikkhah, M.; Kazemi, R. [Faculty of Mechanical Engineering, K.N. Toosi University of Technology, Pardis Street, Molla-Sadra Avenue, Vanak Square, P.O. Box: 19395-1999, Tehran 19991 43344 (Iran, Islamic Republic of)

    2011-02-15

    In the present paper, analytical and numerical elastodynamic solutions are developed for long thick-walled functionally graded cylinders subjected to arbitrary dynamic and shock pressures. Both transient dynamic response and elastic wave propagation characteristics are studied in these non-homogeneous structures. Variations of the material properties across the thickness are described according to both polynomial and power law functions. A numerically consistent transfinite element formulation is presented for both functions whereas the exact solution is presented for the power law function. The FGM cylinder is not divided into isotropic sub-cylinders. An approach associated with dividing the dynamic radial displacement expression into quasi-static and dynamic parts and expansion of the transient wave functions in terms of a series of the eigenfunctions is employed to propose the exact solution. Results are obtained for various exponents of the functions of the material properties distributions, various radius ratios, and various dynamic and shock loads.

  6. Mechanical and biological properties of the micro-/nano-grain functionally graded hydroxyapatite bioceramics for bone tissue engineering.

    Science.gov (United States)

    Zhou, Changchun; Deng, Congying; Chen, Xuening; Zhao, Xiufen; Chen, Ying; Fan, Yujiang; Zhang, Xingdong

    2015-08-01

    Functionally graded materials (FGM) open the promising approach for bone tissue repair. In this study, a novel functionally graded hydroxyapatite (HA) bioceramic with micrograin and nanograin structure was fabricated. Its mechanical properties were tailored by composition of micrograin and nanograin. The dynamic mechanical analysis (DMA) indicated that the graded HA ceramics had similar mechanical property compared to natural bones. Their cytocompatibility was evaluated via fluorescent microscopy and MTT colorimetric assay. The viability and proliferation of rabbit bone marrow mesenchymal stem cells (BMSCs) on ceramics indicated that this functionally graded HA ceramic had better cytocompatibility than conventional HA ceramic. This study demonstrated that functionally graded HA ceramics create suitable structures to satisfy both the mechanical and biological requirements of bone tissues. PMID:25910818

  7. Free vibration analysis of layered functionally graded beams with experimental validation

    International Nuclear Information System (INIS)

    Highlights: ► An improved third order shear deformation theory. ► Energy approach. ► Vibration analysis of layered functionally graded beam with experimental validation. ► The effect of added mass. ► Sample fabrication, volume fraction analysis, vibration testing. -- Abstract: An improved third order shear deformation theory is employed to formulate a governing equation for predicting free vibration of layered functionally graded beams. The Ritz method is adopted to solve the governing equation for various types of boundary conditions and the frequency results are validated by some available and experimental results. A multi-step sequential infiltration technique is used to fabricate the layered functionally graded beams for vibration testing. For the first time, a simple mathematical model, based on a power law distribution, is introduced to approximate material volume fraction of the layered beams. The details of layered beam fabrication according to the infiltration technique, microstructure and volume fraction analysis as well as vibration experimental set up are included and described in this investigation. Aspects which affect natural frequencies, such as material compositions, thickness ratio, and boundary conditions, are then taken into consideration. The impact on frequency of added mass is presented and discussed.

  8. Investigating the Force Production of Functionally-Graded Flexible Wings in Flapping Wing Flight

    Science.gov (United States)

    Mudbhari, Durlav; Erdogan, Malcolm; He, Kai; Bateman, Daniel; Lipkis, Rory; Moored, Keith

    2015-11-01

    Birds, insects and bats oscillate their wings to propel themselves over long distances and to maneuver with unprecedented agility. A key element to achieve their impressive aerodynamic performance is the flexibility of their wings. Numerous studies have shown that homogeneously flexible wings can enhance force production, propulsive efficiency and lift efficiency. Yet, animal wings are not homogenously flexible, but instead have varying material properties. The aim of this study is to characterize the force production and energetics of functionally-graded flexible wings. A partially-flexible wing composed of a rigid section and a flexible section is used as a first-order model of functionally-graded materials. The flexion occurs in the spanwise direction and it is affected by the spanwise flexion ratio, that is, the ratio of the length of the rigid section compared to the total span length. By varying the flexion ratio as well as the material properties of the flexible section, the study aims to examine the force production and energetics of flapping flight with functionally-graded flexible wings. Supported by the Office of Naval Research under Program Director Dr. Bob Brizzolara, MURI grant number N00014-14-1-0533.

  9. The narwhal (Monodon monoceros) cementum-dentin junction: a functionally graded biointerphase.

    Science.gov (United States)

    Grandfield, Kathryn; Chattah, Netta Lev-Tov; Djomehri, Sabra; Eidelmann, Naomi; Eichmiller, Frederick C; Webb, Samuel; Schuck, P James; Nweeia, Martin; Ho, Sunita P

    2014-08-01

    In nature, an interface between dissimilar tissues is often bridged by a graded zone, and provides functional properties at a whole organ level. A perfect example is a "biological interphase" between stratified cementum and dentin of a narwhal tooth. This study highlights the graded structural, mechanical, and chemical natural characteristics of a biological interphase known as the cementum-dentin junction layer and their effect in resisting mechanical loads. From a structural perspective, light and electron microscopy techniques illustrated the layer as a wide 1000-2000 μm graded zone consisting of higher density continuous collagen fiber bundles from the surface of cementum to dentin, that parallels hygroscopic 50-100 μm wide collagenous region in human teeth. The role of collagen fibers was evident under compression testing during which the layer deformed more compared to cementum and dentin. This behavior is reflected through site-specific nanoindentation indicating a lower elastic modulus of 2.2 ± 0.5 GPa for collagen fiber bundle compared to 3 ± 0.4 GPa for mineralized regions in the layer. Similarly, microindentation technique illustrated lower hardness values of 0.36 ± 0.05 GPa, 0.33 ± 0.03 GPa, and 0.3 ± 0.07 GPa for cementum, dentin, and cementum-dentin layer, respectively. Biochemical analyses including Raman spectroscopy and synchrotron-source microprobe X-ray fluorescence demonstrated a graded composition across the interface, including a decrease in mineral-to-matrix and phosphate-to-carbonate ratios, as well as the presence of tidemark-like bands with Zn. Understanding the structure-function relationships of wider tissue interfaces can provide insights into natural tissue and organ function. PMID:25205746

  10. Determination and modeling of residual stress in functionally graded WC-Co

    Science.gov (United States)

    Tahvilian, Leila

    Gradual variations in composition and/or structure through the volume of functionally graded materials (FGMs) generally result in corresponding continuous spatial variations in mechanical/physical properties, and often in significant residual stresses that develop during processing. Due to inhomogeneous properties in these materials, residual stress measurement in FGMs can be a very challenging problem. In this study, residual stresses in functionally graded cemented tungsten carbide (FG-WC-Co) were investigated by numerical, analytical and experimental approaches by means of a layer removal technique. The numerical method consisted of finite element analysis (FEA) modeling for the FGM plate, in order to calculate residual stress distribution over the volume and to develop a method for predicting residual stress levels in closely related materials. The analytical procedure embodied a mathematical approach to determine residual stress distributions, and analytically determined values are compared with those obtained from FEA modeling and experimental results. The experimental approach consisted of fabricating and heat treating FG-WC-Co flat samples, then measuring strain changes by strain gauge after each sequential layer removal from the opposite side of the specimen from the graded region. Good agreement was found between analytical, numerical and experimental results. Furthermore, thermal residual stress distribution in FG-WC-Co hollow cylinder was examined with an emphasis on the effects of key variables, the gradient profile and the gradient thickness, on the magnitude and distribution of the stress field. An analytical direct solution based on solving the governing equations of a cylinder composed of a uniform inner core and a functionally graded outer shell was developed. The cylindrical compound was considered as two separate elements: homogeneous cylinder and functionally graded shell. Material properties, such as the elastic modulus and the coefficient of

  11. Determination of the Local Thermal Conductivity of Functionally Graded Materials by a Laser Flash Method

    DEFF Research Database (Denmark)

    Zajas, Jan Jakub; Heiselberg, Per

    2013-01-01

    Determination of thermal conductivity of construction materials is essential to estimate their insulation capabilities. In most cases, homogenous materials are used and well developed methods exist for measurements of their thermal conductivity. The task becomes more challenging when dealing with...... scanning them point by point and determining the thermal conductivity as a function of the spatial dimensions. The method proves to be repeatable and of reasonable accuracy and can be used to determine the local thermal properties on a scale of millimeters. In this study, the method was successfully...... applied to create a map of thermal conductivity of a functionally graded material sample....

  12. A new design of cemented stem using functionally graded materials (FGM).

    Science.gov (United States)

    Hedia, H S; Aldousari, S M; Abdellatif, A K; Fouda, N

    2014-01-01

    One of the most frequent complications of total hip replacement (THR) is aseptic loosening of femoral component which is primarily due to changes of post-operative stress distribution pattern with respect to intact femur. Stress shielding of the femur is known to be a principal factor in aseptic loosening of hip replacements. Many designers show that a stiff stem shields the surrounding bone from mechanical loading causing stress shielding. Others show that reducing stem stiffness promotes higher proximal interface shear stress which increases the risk of proximal interface failure. Therefore, the task of this investigation is to solve these conflicting problems appeared in the cemented total hip replacement. The finite element method and optimization technique are used in order to find the optimal stem material which gives the optimal available stress distribution between the proximal medial femoral bone and the cement mantle interfaces. The stem is designed using the concept of functionally graded material (FGM) instead of using the conventional most common used stem material. The results showed that there are four feasible solutions from the optimization runs. The best of these designs is to use a cemented stem graded from titanium at the upper stem layer to collagen at the lower stem layer. This new cemented stem design completely eliminates the stress shielding problem at the proximal medial femoral region. The stress shielding using the cemented functionally graded stem is reduced by 98% compared to titanium stem. PMID:24840196

  13. Thermal Stress Analysis of W/Cu Functionally Graded Materials by Using Finite Element Method

    International Nuclear Information System (INIS)

    Copper alloys with tungsten coating shows an excellent plasma irradiation resistance, however, the difference of coefficient thermal expansion between W and Cu makes it really a difficult job to prepare over 1 mm W coating with high adhesive strength. Functionally graded material (FGM) seems to be an effective method to improve the adhesive strength of thick W coating. This paper focused on the finite element simulation on thermal stress for W/Cu FGM with different graded layers, composition and thicknesses. In addition, the variance of stresses for functionally graded coatings with the steady state heat flux were simulated by finite element analysis (ANSYS Workbench). The results showed that the W/Cu FGM was effectively beneficial for the stress relief of W coating. Meanwhile, the maximum von mises stress decreased approximately by 52.8 % compared to monolithic W plasma facing material. And the four-layer FGM with a compositional exponent of 2 was optimum for 1.5 mm W coating.

  14. On the nonlinear axisymmetric dynamic buckling behavior of clamped functionally graded spherical caps

    Science.gov (United States)

    Prakash, T.; Sundararajan, N.; Ganapathi, M.

    2007-01-01

    Here, the dynamic thermal buckling behavior of functionally graded spherical caps is studied considering geometric nonlinearity based on von Karman's assumptions. The formulation is based on first-order shear deformation theory and it includes the in-plane and rotary inertia effects. The material properties are graded in the thickness direction according to the power-law distribution in terms of volume fractions of the material constituents. The effective material properties are evaluated using homogenization method. The governing equations obtained using finite element approach are solved employing the Newmark's integration technique coupled with a modified Newton-Raphson iteration scheme. The pressure load corresponding to a sudden jump in the maximum average displacement in the time history of the shell structure is taken as the dynamic buckling load. The present model is validated against the available isotropic case. A detailed numerical study is carried out to highlight the influences of shell geometries, power law index of functional graded material and boundary conditions on the dynamic buckling load of shallow spherical shells.

  15. Preparation of Al/Si functionally graded materials using ultrasonic separation method

    Directory of Open Access Journals (Sweden)

    Zhang Zhongtao

    2008-08-01

    Full Text Available Functionally graded materials (FGM have been widely used in many industries such as aerospace, energy and electronics. In this experimental study of fabricating FGM, an approach was developed to prepare Al/Si FGM using power ultrasonic separation method. Material sample with continuously changing composition and performance/properties was successfully produced. Results showed that the microstructure of the FGM sample transited, from its top to bottom, from the hypereutectic structure with a large quantity of primary Si gradually to the eutectic, and fi nally to the hypoeutectic with numerous primary Al dendrites. The distribution of primary Si and microhardness of the FGM sample also presented graded characteristics, resulting that the wear resistance of the FGM sample decreased from top to bottom. Preliminary discussion was made on the mechanism of the formation of Al/Si FGM.

  16. Stresses and Displacements in Functionally Graded Materials of Semi-Infinite Extent Induced by Rectangular Loadings

    Directory of Open Access Journals (Sweden)

    Zhong-Qi Yue

    2012-01-01

    Full Text Available This paper presents the stress and displacement fields in a functionally graded material (FGM caused by a load. The FGM is a graded material of Si3N4-based ceramics and is assumed to be of semi-infinite extent. The load is a distributed loading over a rectangular area that is parallel to the external surface of the FGM and either on its external surface or within its interior space. The point-load analytical solutions or so-called Yue’s solutions are used for the numerical integration over the distributed loaded area. The loaded area is discretized into 200 small equal-sized rectangular elements. The numerical integration is carried out with the regular Gaussian quadrature. Weak and strong singular integrations encountered when the field points are located on the loaded plane, are resolved with the classical methods in boundary element analysis. The numerical integration results have high accuracy.

  17. Preparation of Al/Si functionally graded materials using ultrasonic separation method

    Institute of Scientific and Technical Information of China (English)

    Zhang Zhongtao; LI Tingju; Yue Hongyun; Zhang Jian; Li Jie

    2008-01-01

    Functionally graded materials (FGM) have been widely used in many industries such as aerospace, energy and electronics. In this experimental study of fabricating FGM, an approach was developed to prepare Al/Si FGM using power ultrasonic separation method. Material sample with continuously changing composition and performance/properties was successfully produced. Results showed that the microstructure of the FGM sample transited, from its top to bottom, from the hypereutectic structure with a large quantity of primary Si gradually to the eutectic, and finally to the hypoeutectic with numerous primary AI dendrites. The distribution of primary Si and microhardness of the FGM sample also presented graded characteristics, resulting that the wear resistance of the FGM sample decreased from top to bottom. Preliminary discussion was made on the mechanism of the formation of Al/Si FGM.

  18. Nonlinear free flexural vibrations of functionally graded rectangular and skew plates under thermal environments

    CERN Document Server

    Sundararajan, N; Ganapathi, M; 10.1016/j.finel.2005.06.001

    2011-01-01

    The nonlinear formulation developed based on von Karman's assumptions is employed to study the free vibration characteristics of functionally graded material (FGM) plates subjected to thermal environment. Temperature field is assumed to be a uniform distribution over the plate surface and varied in the thickness direction. The material is assumed to be temperature dependent and graded in the thickness direction according to the power-law distribution in terms of volume fractions of the constituents. The effective material properties are estimated from the volume fractions and the material properties of the constituents using Mori-Tanaka homogenization method. The nonlinear governing equations obtained using Lagrange's equations of motion are solved using finite element procedure coupled with the direct iteration technique. The variation of nonlinear frequency ratio with amplitude is highlighted considering various parameters such as gradient index, temperature, thickness and aspect ratios, and skew angle. For...

  19. Electro-magneto-thermo-elastic response of infinite functionally graded cylinders without energy dissipation

    Science.gov (United States)

    Zenkour, Ashraf M.; Abbas, Ibrahim A.

    2015-12-01

    The electro-magneto-thermo-elastic analysis problem of an infinite functionally graded (FG) hollow cylinder is studied in the context of Green-Naghdi's (G-N) generalized thermoelasticity theory (without energy dissipation). Material properties are assumed to be graded in the radial direction according to a novel power-law distribution in terms of the volume fractions of the metal and ceramic constituents. The inner surface of the FG cylinder is pure metal whereas the outer surface is pure ceramic. The equations of motion and the heat-conduction equation are used to derive the governing second-order differential equations. A finite element scheme is presented for the numerical purpose. The system of differential equations is solved numerically and some plots for displacement, radial and electromagnetic stresses, and temperature are presented. The radial displacement, mechanical stresses and temperature as well as the electromagnetic stress are all investigated along the radial direction of the infinite cylinder.

  20. Linear free flexural vibration of cracked functionally graded plates in thermal environment

    CERN Document Server

    Natarajan, S; Ganapathi, M; Kerfriden, P; Bordas, S; 10.1016/j.compstruc.2011.04.002

    2011-01-01

    In this paper, the linear free flexural vibrations of functionally graded material plates with a through center crack is studied using an 8-noded shear flexible element. The material properties are assumed to be temperature dependent and graded in the thickness direction. The effective material properties are estimated using the Mori-Tanaka homogenization scheme. The formulation is developed based on first-order shear deformation theory. The shear correction factors are evaluated employing the energy equivalence principle. The variation of the plates natural frequency is studied considering various parameters such as the crack length, plate aspect ratio, skew angle, temperature, thickness and boundary conditions. The results obtained here reveal that the natural frequency of the plate decreases with increase in temperature gradient, crack length and gradient index.

  1. FUNCTIONALLY GRADED ALUMINA/MULLITE COATINGS FOR PROTECTION OF SILICON CARBIDE CERAMIC COMPONENTS FROM CORROSION; FINAL

    International Nuclear Information System (INIS)

    The main objective of this research project was the formulation of processes that can be used to prepare compositionally graded alumina/mullite coatings for protection from corrosion of silicon carbide components (monolithic or composite) used or proposed to be used in coal utilization systems (e.g., combustion chamber liners, heat exchanger tubes, particulate removal filters, and turbine components) and other energy-related applications. Since alumina has excellent resistance to corrosion but coefficient than silicon carbide, the key idea of this project has been to develop graded coatings with composition varying smoothly along their thickness between an inner (base) layer of mullite in contact with the silicon carbide component and an outer layer of pure alumina, which would function as the actual protective coating of the component. (Mullite presents very good adhesion towards silicon carbide and has thermal expansion coefficient very close to that of the latter.)

  2. FUNCTIONALLY GRADED ALUMINA/MULLITE COATINGS FOR PROTECTION OF SILICON CARBIDE CERAMIC COMPONENTS FROM CORROSION

    Energy Technology Data Exchange (ETDEWEB)

    Prof. Stratis V. Sotirchos

    2001-02-01

    The main objective of this research project was the formulation of processes that can be used to prepare compositionally graded alumina/mullite coatings for protection from corrosion of silicon carbide components (monolithic or composite) used or proposed to be used in coal utilization systems (e.g., combustion chamber liners, heat exchanger tubes, particulate removal filters, and turbine components) and other energy-related applications. Since alumina has excellent resistance to corrosion but coefficient than silicon carbide, the key idea of this project has been to develop graded coatings with composition varying smoothly along their thickness between an inner (base) layer of mullite in contact with the silicon carbide component and an outer layer of pure alumina, which would function as the actual protective coating of the component. (Mullite presents very good adhesion towards silicon carbide and has thermal expansion coefficient very close to that of the latter.)

  3. Propagation of elastic waves in an anisotropic functionally graded hollow cylinder in vacuum.

    Science.gov (United States)

    Baron, Cécile

    2011-02-01

    As a non-destructive, non-invasive and non-ionizing evaluation technique for heterogeneous media, the ultrasonic method is of major interest in industrial applications but especially in biomedical fields. Among the unidirectionally heterogeneous media, the continuously varying media are a particular but widespread case in natural materials. The first studies on laterally varying media were carried out by geophysicists on the Ocean, the atmosphere or the Earth, but the teeth, the bone, the shells and the insects wings are also functionally graded media. Some of them can be modeled as planar structures but a lot of them are curved media and need to be modeled as cylinders instead of plates. The present paper investigates the influence of the tubular geometry of a waveguide on the propagation of elastic waves. In this paper, the studied structure is an anisotropic hollow cylinder with elastic properties (stiffness coefficients c(ij) and mass density ρ) functionally varying in the radial direction. An original method is proposed to find the eigenmodes of this waveguide without using a multilayered model for the cylinder. This method is based on the sextic Stroh's formalism and an analytical solution, the matricant, explicitly expressed under the Peano series expansion form. This approach has already been validated for the study of an anisotropic laterally-graded plate (Baron et al., 2007; Baron and Naili, 2010) [6,5]. The dispersion curves obtained for the radially-graded cylinder are compared to the dispersion curves of a corresponding laterally-graded plate to evaluate the influence of the curvature. Preliminary results are presented for a tube of bone in vacuum modelling the in vitro conditions of bone strength evaluation. PMID:20692675

  4. Analysis of Thermal Buckling of Ceramic-Metal Functionally Graded Plates Using Refined Third Order Shear Deformation Theory

    Directory of Open Access Journals (Sweden)

    S. S. Daimi

    2014-08-01

    Full Text Available Functionally graded materials (FGMs are microscopically inhomogeneous spatial composite materials, typically composed of a ceramic-metal or ceramic-polymer pair of materials. Therefore, it is important to investigate the behaviors of engineering structures such as beams and plates made from FGMs when they are subjected to thermal loads for appropriate design. Therefore, using an improved third order shear deformation theory (TSDT based on more rigorous kinetics of displacements to predict the behaviors of functionally graded plates is expected to be more suitable than using other theories. In this paper, the improved TSDT is used to investigate thermal buckling of functionally graded plates. Temperature dependent material property solutions are adopted to investigate thermal buckling results of functionally graded plates. To obtain the solutions, the Ritz method using polynomial and trigonometric functions for defining admissible displacements and rotations is applied to solve the governing equations.

  5. On Super-KMS Functionals for Graded-Local Conformal Nets

    CERN Document Server

    Hillier, Robin

    2012-01-01

    Motivated by a few preceding works, we introduce super-KMS functionals for graded-local conformal nets with superderivations, roughly speaking as a certain supersymmetric modification of classical KMS states on local conformal nets. Although we are able to make several surprising statements concerning their general structure, most properties will be studied in the setting of individual models. In particular, we provide a constructive existence and partial uniqueness proof of super-KMS functionals for the supersymmetric free field in d dimensions, for its rational extensions, and for the super-Virasoro net. As a general tool we develop a quasi-equivalence criterion for certain functionals on the CAR algebra in the sense of Araki. Moreover, we show that super-KMS functionals - as one of their main applications - give rise to generalized perturbation-invariant entire cyclic (JLO) cocycles and thus to a connection with noncommutative geometry.

  6. Evaluation of Green's Function Derivatives for Exponentially Graded Elasticity

    Energy Technology Data Exchange (ETDEWEB)

    Abd El Azzim Mohamed, Omar M [ORNL; Gray, Leonard J [ORNL; Nintcheu Fata, Sylvain [ORNL

    2010-01-01

    Effective formulas for computing the Green's function of an exponentially graded three dimensional material have been derived In previous work. The expansion approach for evaluating the Green's function has been extended to develop corresponding algorithms for its first and second order derivatives. The resulting formulas are again obtained as a relatively simple analytic term plus a single double integral, the integrand involving only elementary functions. A primary benefit of the expansion procedure is the ability to compute the second order derivatives needed for fracture analysis. Moreover, as all singular terms in this hypersingular kernel are contained in the analytic expression, these expressions are readily implemented in a boundary integral equation calculation. The computational formulas for the first derivative are tested by comparing with results of finite difference approximations involving the Green's function. In turn, the second derivatives are then validated by comparing with finite difference quotients using the first derivatives.

  7. Optimization design and residual thermal stress analysis of PDC functionally graded materials

    Institute of Scientific and Technical Information of China (English)

    CAO Pin-lu; LIU Bao-chang; YIN Kun; ZHANG Zu-pei

    2006-01-01

    The distribution of thermal stresses in functionally graded polycrystalline diamond compact (PDC) and in single coating of PDC are analyzed respectively by thermo-mechanical finite element analysis (FEA). It is shown that they each have a remarkable stress concentration at the edge of the interfaces. The diamond coatings usually suffer premature failure because of spallation, distortion or defects such as cracks near the interface due to these excessive residual stresses. Results showed that the axial tensile stress in FGM coating is reduced from 840 MPa to 229 MPa compared with single coating, and that the shear stress is reduced from 671 MPa to 471 MPa. Therefore, the single coating is more prone to spallation and cracking than the FGM coating.The effects of the volume compositional distribution factor (n) and the number of the graded layers (L) on the thermal stresses in FGM coating are also discussed respectively. Modelling results showed that the optimum value of the compositional distribution factor is 1.2, and that the best number of the graded layers is 6.

  8. Novel Investigation on Nanostructured Multilayer and Functionally Graded Ni-P Electroless Coatings on Stainless Steel

    Science.gov (United States)

    Anvari, S. R.; Monirvaghefi, S. M.; Enayati, M. H.

    2015-06-01

    In this study, step-wise multilayer and functionally graded Ni-P coatings were deposited with electroless in which the content of phosphorus and nickel would be changed gradually and step-wise through the thickness of the coatings, respectively. To compare the properties of these coatings with Ni-P single-layer coatings, three types of coatings with different phosphorus contents were deposited. Heat treatment of coatings was performed at 400 °C for 1 h. The microstructure and phase transformation of coatings were characterized by SEM/EDS, TEM, and XRD. The mechanical properties of coatings were studied by nanoindentation test. According to the results of the single-layer coatings, low P coating had the maximum hardness and also the ratio of hardness ( H) to elasticity modulus ( E) for the mentioned coating was maximum. In addition, low and medium P coatings had crystalline and semi-crystalline structure, respectively. The mentioned coatings had texture and after heat treatment their texture didn't change. While high P coating had amorphous structure, after heat treatment it changed to crystalline structure with texture for nickel grains. Furthermore, the results showed that functionally graded and step-wise multilayer coatings were deposited successfully by using the same initial bath and changing the temperature and pH during deposition. Nanoindentation test results showed that the hardness of the mentioned coatings changed from 670 Hv near the substrate to 860 Hv near the top surface of coatings. For functionally graded coating the hardness profile had gradual changes, while step-wise multilayer coating had step-wise hardness profile. After heat treatment trend of hardness profiles was changed, so that near the substrate, hardness was measured 1400 Hv and changed to 1090 Hv at the top coat.

  9. Geometry Design Optimization of Functionally Graded Scaffolds for Bone Tissue Engineering: A Mechanobiological Approach.

    Directory of Open Access Journals (Sweden)

    Antonio Boccaccio

    Full Text Available Functionally Graded Scaffolds (FGSs are porous biomaterials where porosity changes in space with a specific gradient. In spite of their wide use in bone tissue engineering, possible models that relate the scaffold gradient to the mechanical and biological requirements for the regeneration of the bony tissue are currently missing. In this study we attempt to bridge the gap by developing a mechanobiology-based optimization algorithm aimed to determine the optimal graded porosity distribution in FGSs. The algorithm combines the parametric finite element model of a FGS, a computational mechano-regulation model and a numerical optimization routine. For assigned boundary and loading conditions, the algorithm builds iteratively different scaffold geometry configurations with different porosity distributions until the best microstructure geometry is reached, i.e. the geometry that allows the amount of bone formation to be maximized. We tested different porosity distribution laws, loading conditions and scaffold Young's modulus values. For each combination of these variables, the explicit equation of the porosity distribution law-i.e the law that describes the pore dimensions in function of the spatial coordinates-was determined that allows the highest amounts of bone to be generated. The results show that the loading conditions affect significantly the optimal porosity distribution. For a pure compression loading, it was found that the pore dimensions are almost constant throughout the entire scaffold and using a FGS allows the formation of amounts of bone slightly larger than those obtainable with a homogeneous porosity scaffold. For a pure shear loading, instead, FGSs allow to significantly increase the bone formation compared to a homogeneous porosity scaffolds. Although experimental data is still necessary to properly relate the mechanical/biological environment to the scaffold microstructure, this model represents an important step towards

  10. A semi-analytical three-dimensional free vibration analysis of functionally graded curved panels

    Energy Technology Data Exchange (ETDEWEB)

    Zahedinejad, P. [Department of Mechanical Engineering, Islamic Azad University, Branch of Shiraz, Shiraz (Iran, Islamic Republic of); Malekzadeh, P., E-mail: malekzadeh@pgu.ac.i [Department of Mechanical Engineering, Persian Gulf University, Persian Gulf University Boulevard, Bushehr 75168 (Iran, Islamic Republic of); Center of Excellence for Computational Mechanics, Shiraz University, Shiraz (Iran, Islamic Republic of); Farid, M. [Department of Mechanical Engineering, Islamic Azad University, Branch of Shiraz, Shiraz (Iran, Islamic Republic of); Karami, G. [Department of Mechanical Engineering and Applied Mechanics, North Dakota State University, Fargo, ND 58105-5285 (United States)

    2010-08-15

    Based on the three-dimensional elasticity theory, free vibration analysis of functionally graded (FG) curved thick panels under various boundary conditions is studied. Panel with two opposite edges simply supported and arbitrary boundary conditions at the other edges are considered. Two different models of material properties variations based on the power law distribution in terms of the volume fractions of the constituents and the exponential distribution of the material properties through the thickness are considered. Differential quadrature method in conjunction with the trigonometric functions is used to discretize the governing equations. With a continuous material properties variation assumption through the thickness of the curved panel, differential quadrature method is efficiently used to discretize the governing equations and to implement the related boundary conditions at the top and bottom surfaces of the curved panel and in strong form. The convergence of the method is demonstrated and to validate the results, comparisons are made with the solutions for isotropic and FG curved panels. By examining the results of thick FG curved panels for various geometrical and material parameters and subjected to different boundary conditions, the influence of these parameters and in particular, those due to functionally graded material parameters are studied.

  11. The edge crack problem for an orthotropic functionally graded strip under concentrated loads

    Institute of Scientific and Technical Information of China (English)

    果立成; 吴林志; 曾涛

    2004-01-01

    The plane crack problem of an orthotropic functionally graded strip under concentrated loads is studied. The edge crack is perpendicular to the boundary and the elastic property of the material is assumed to vary depending on thickness. By using an integral transform method, the present problem can be reduced to a single integral equation which is solved numerically. The influences of parameters such as the nonhomogeneity constant and the geometry parameters on the stress intensity factors (SIFs) are studied. It is found that the nonhomogeneity constant has important influences on the SIFs.

  12. A Study on Propagation Characteristic of One-dimensional Stress Wave in Functionally Graded Armor Composites

    International Nuclear Information System (INIS)

    The development of Functionally Graded Materials (FGM) for energy-absorbing applications requires understanding of stress wave propagation in these structures in order to optimize their resistance to failure. One-dimensional stress wave in FGM composites under elastic and plastic wave loading have been investigated. The stress distributions through the thickness and stress status have been analyzed and some comparisons have been done with the materials of sharp interfaces (two-layered material). The results demonstrate that the gradient structure design greatly decreases the severity of the stress concentrations at the interfaces and there are no clear differences in stress distribution in FGM composites under elastic and plastic wave loading.

  13. Magnetothermoelastic interactions in hollow structures of functionally graded material subjected to mechanical loads

    International Nuclear Information System (INIS)

    This paper considers the magnetothermoelastic problem of functionally graded material (FGM) hollow structures subjected to mechanical loads. Exact solutions for stresses and perturbations of the magnetic field vector in FGM hollow cylinders and FGM hollow spheres are determined using the infinitesimal theory of magnetothermoelasticity. The material stiffness, thermal expansion coefficient and magnetic permeability are assumed to obey the same simple power-law variation through the structures' wall thickness. The aim of this research is to understand the effect of composition on magneto- thermoelastic stresses and to design optimum FGM hollow cylinders and hollow spheres

  14. Phase instability in ZrO2 endash NiAl functionally graded materials

    International Nuclear Information System (INIS)

    Sedimentation in organic solvents was followed by hot-pressing to produce 2 mole% yttria stabilized zirconia-NiAl functionally graded materials (FGM close-quote s). These FGM close-quote s were better able to accommodate high levels of residual stress than alumina-NiAl FGM close-quote s; this is possibly due to enhanced tetragonal phase retention. However, we found that the zirconia layer in these FGM close-quote s subsequently experiences room temperature transformation of t-ZrO2 to m-ZrO2. copyright 1997 Materials Research Society

  15. Static Response of Functionally Graded Material Plate under Transverse Load for Varying Aspect Ratio

    Directory of Open Access Journals (Sweden)

    Manish Bhandari

    2014-01-01

    Full Text Available Functionally gradient materials (FGM are one of the most widely used materials in various applications because of their adaptability to different situations by changing the material constituents as per the requirement. Nowadays it is very easy to tailor the properties to serve specific purposes in functionally gradient material. Most structural components used in the field of engineering can be classified as beams, plates, or shells for analysis purposes. In the present study the power law, sigmoid law and exponential distribution, is considered for the volume fraction distributions of the functionally graded plates. The work includes parametric studies performed by varying volume fraction distributions and aspect ratio. The FGM plate is subjected to transverse UDL (uniformly distributed load and point load and the response is analysed.

  16. Study of high temperature oxidation of duplex and functionally graded materials of thermal barrier coating (FGM TBC)

    International Nuclear Information System (INIS)

    Although the number and the severity of thermal barrier coatings applications on hot section components have dramatically increased in the past decade, premature spallation failure of thermal barrier coatings , due to mismatch of thermal expansion at the metal/ceramic interface of the two coating layers, during service is still an overriding concern. Therefore, functionally graded materials with a gradual compositional variation have been introduced. In this study, comparison of properties of two different types of thermal barrier coatings was made to improve the surface characteristics on high temperature components. These thermal barrier coatings consisted of a duplex thermal barrier coatings and a five layered functionally graded thermal barrier coatings . In both coatings, Yttria partially stabilized Zirconia topcoat was deposited by air plasma spraying and Ni Cr Al Y bond coat was deposited by high velocity oxy fuel spraying. In functionally graded materials coating, functionally graded layer was sprayed by air plasma process by varying the feeding ratio of YSZ/Ni Cr Al Y powders using two separate powder feeders. Then, isothermal oxidation was carried out at 950degC in atmosphere to obtain the plot of mass change vs. time to study oxidation kinetic. Microstructural and compositional changes of coating, oxides formed during service were examined by optical microscope and scanning electron microscopy with EDS. functionally graded materials coating failed after 2100 h and duplex coating failed after 1700 h. Finally, it was found that functionally graded materials coating is more qualified than duplex thermal barrier coatings and stands for a longer time

  17. Fabrication of a nanocrystalline Ni-Co/CoO functionally graded layer with excellent electrochemical corrosion and tribological performance.

    Science.gov (United States)

    Wang, Liping; Zhang, Junyan; Zeng, Zhixiang; Lin, Yiming; Hu, Litian; Xue, Qunji

    2006-09-28

    Nanocrystalline (NC) Ni-Co/CoO functionally graded materials with excellent lubricating, high anti-corrosion and anti-wear performance were fabricated by electrodeposition and subsequent cyclic thermal oxidation and quenching. Transmission electron microscopy and energy dispersive x-ray spectroscopy investigations show that bulk Ni-Co gradient deposits with an average grain size in the range of 13-40 nm demonstrated a graded structure transition from face-centred cubic to hexagonal close packed and graded composition changes from Ni-rich to Co-rich regions with the increase in deposit thickness. X-ray diffraction and x-ray photoelectron spectroscopy analysis indicated the surface layer of NC Ni-Co graded materials to be mainly composed of dense and ultrafine CoO with a (111) preferred orientation. The NC Ni-Co/CoO functionally graded materials exhibited significantly enhanced corrosion resistance in both NaOH and NaCl solutions and remarkably improved wear resistance and dry self-lubricating performance when compared with the NC Ni and Ni-Co graded deposits under dry sliding wear conditions. The higher corrosion and tribological performance of NC Ni-Co/CoO graded materials can be attributed to the graded microstructure within the deposits, the anti-corrosion barrier of a dense oxide layer and the solid lubrication effect of CoO-rich tribo-surface films. PMID:21727585

  18. Bifurcation and chaos of thin circular functionally graded plate in thermal environment

    Energy Technology Data Exchange (ETDEWEB)

    Hu Yuda, E-mail: huyuda03@163.com [School of Civil Engineering and Mechanics, Yanshan University, Qinhuangdao 066004 (China); Zhang Zhiqiang, E-mail: zhangzqvib@126.com [School of Civil Engineering and Mechanics, Yanshan University, Qinhuangdao 066004 (China)

    2011-09-15

    Highlights: > We study bifurcations and chaotic dynamics of a FGM circular plate. > We consider the effect of temperature-dependent material properties. > Increasing volume fraction index will increase chaotic regions. > Increasing temperature will reduce chaotic regions. > The FGM plate exists chaotic motions, multiple periodic and periodic motions. - Abstract: A ceramic/metal functionally graded circular plate under one-term and two-term transversal excitations in the thermal environment is investigated, respectively. The effects of geometric nonlinearity and temperature-dependent material properties are both taken into account. The material properties of the functionally graded plate are assumed to vary continuously through the thickness, according to a power law distribution of the volume fraction of the constituents. Using the principle of virtual work, the nonlinear partial differential equations of FGM plate subjected to transverse harmonic forcing excitation and thermal load are derived. For the circular plate with clamped immovable edge, the Duffing nonlinear forced vibration equation is deduced using Galerkin method. The criteria for existence of chaos under one-term and two-term periodic perturbations are given with Melnikov method. Numerical simulations are carried out to plot the bifurcation curves for the homolinic orbits. Effects of the material volume fraction index and temperature on the criterions are discussed and the existences of chaos are validated by plotting phase portraits, Poincare maps. Also, the bifurcation diagrams and corresponding maximum Lyapunov exponents are plotted. It was found that periodic, multiple periodic solutions and chaotic motions exist for the FGM plate under certain conditions.

  19. Dynamic stability of functionally graded cantilever cylindrical shells under distributed axial follower forces

    Science.gov (United States)

    Torki, Mohammad Ebrahim; Kazemi, Mohammad Taghi; Reddy, Junuthula N.; Haddadpoud, Hassan; Mahmoudkhani, Saeid

    2014-02-01

    In this paper, flutter of functionally graded material (FGM) cylindrical shells under distributed axial follower forces is addressed. The first-order shear deformation theory is used to model the shell, and the material properties are assumed to be graded in the thickness direction according to a power law distribution using the properties of two base material phases. The solution is obtained by using the extended Galerkin's method, which accounts for the natural boundary conditions that are not satisfied by the assumed displacement functions. The effect of changing the concentrated (Beck's) follower force into the uniform (Leipholz's) and linear (Hauger's) distributed follower loads on the critical circumferential mode number and the minimum flutter load is investigated. As expected, the flutter load increases as the follower force changes from the so-called Beck's load into the so-called Leipholz's and Hauger's loadings. The increased flutter load was calculated for homogeneous shell with different mechanical properties, and it was found that the difference in elasticity moduli bears the most significant effect on the flutter load increase in short, thick shells. Also, for an FGM shell, the increase in the flutter load was calculated directly, and it was found that it can be derived from the simple power law when the corresponding increase for the two base phases are known.

  20. A study on the dynamics of rotating beams with functionally graded properties

    Science.gov (United States)

    Piovan, M. T.; Sampaio, R.

    2009-10-01

    The constant needs of the industry impel the engineering community in seeking of new concepts and new strategies in order to improve the structural response of structures as well as to enhance the endurance of materials. This is particularly true in the case of rotating blades that are subjected to severe environmental conditions such as high temperatures as well as mechanical conditions such as high rotating accelerations, centrifugal forces, geometric stiffening, among others. It is well known that flexible beams become stiffer when subjected to high speed rotations, because of the axial-bending coupling associated to the large displacements of the beam cross-section. This is called geometric stiffening effect and it was analyzed over the last decades in many beam applications from blade problems to drill-string modeling. In this paper a rotating nonlinear beam model accounting for arbitrary axial deformations is developed. The beam is made of functionally graded materials (FGM). This model is also employed to analyze other simplified models based on isotropic materials or composite materials, that are particular cases of the present formulation. The assumption of steady-state values of centrifugal loads is evaluated. It has to be said that there is a lack of information about modeling of beams made of functionally graded materials and this paper is intended to be a contribution on the subject.

  1. Buckling Analysis of Functionally Graded Material Plates Using Higher Order Shear Deformation Theory

    Directory of Open Access Journals (Sweden)

    B. Sidda Reddy

    2013-01-01

    Full Text Available The prime aim of the present study is to present analytical formulations and solutions for the buckling analysis of simply supported functionally graded plates (FGPs using higher order shear deformation theory (HSDT without enforcing zero transverse shear stresses on the top and bottom surfaces of the plate. It does not require shear correction factors and transverse shear stresses vary parabolically across the thickness. Material properties of the plate are assumed to vary in the thickness direction according to a power law distribution in terms of the volume fractions of the constituents. The equations of motion and boundary conditions are derived using the principle of virtual work. Solutions are obtained for FGPs in closed-form using Navier’s technique. Comparison studies are performed to verify the validity of the present results from which it can be concluded that the proposed theory is accurate and efficient in predicting the buckling behavior of functionally graded plates. The effect of side-to-thickness ratio, aspect ratio, modulus ratio, the volume fraction exponent, and the loading conditions on the critical buckling load of FGPs is also investigated and discussed.

  2. Analysis of Dynamic Fracture Parameters in Functionally Graded Material Plates with Cracks by Graded Finite Element Method and Virtual Crack Closure Technique

    Directory of Open Access Journals (Sweden)

    Li Ming Zhou

    2016-01-01

    Full Text Available Based on the finite element software ABAQUS and graded element method, we developed a dummy node fracture element, wrote the user subroutines UMAT and UEL, and solved the energy release rate component of functionally graded material (FGM plates with cracks. An interface element tailored for the virtual crack closure technique (VCCT was applied. Fixed cracks and moving cracks under dynamic loads were simulated. The results were compared to other VCCT-based analyses. With the implementation of a crack speed function within the element, it can be easily expanded to the cases of varying crack velocities, without convergence difficulty for all cases. Neither singular element nor collapsed element was required. Therefore, due to its simplicity, the VCCT interface element is a potential tool for engineers to conduct dynamic fracture analysis in conjunction with commercial finite element analysis codes.

  3. Optimization of Sound Transmission Loss through a Thin Functionally Graded Material Cylindrical Shell

    Directory of Open Access Journals (Sweden)

    Ali Nouri

    2014-01-01

    Full Text Available The maximizing of sound transmission loss (TL across a functionally graded material (FGM cylindrical shell has been conducted using a genetic algorithm (GA. To prevent the softening effect from occurring due to optimization, the objective function is modified based on the first resonant frequency. Optimization is performed over the frequency range 1000–4000 Hz, where the ear is the most sensitive. The weighting constants are chosen here to correspond to an A-weighting scale. Since the weight of the shell structure is an important concern in most applications, the weight of the optimized structure is constrained. Several traditional materials are used and the result shows that optimized shells with aluminum-nickel and aluminum-steel FGM are the most effective at maximizing TL at both stiffness and mass control region, while they have minimum weight.

  4. An approximate solution to the stress and deformation states of functionally graded rotating disks

    Science.gov (United States)

    Sondhi, Lakshman; Sanyal, Shubhashis; Saha, Kashi Nath; Bhowmick, Shubhankar

    2016-07-01

    The present work employs variational principle to investigate the stress and deformation states and estimate the limit angular speed of functionally graded high-speed rotating annular disks of constant thickness. Assuming a series approximation following Galerkin's principle, the solution of the governing equation is obtained. In the present study, elasticity modulus and density of the disk material are taken as power function of radius with the gradient parameter ranging between 0.0 and 1.0. Results obtained from numerical solutions are validated with benchmark results and are found to be in good agreement. The results are reported in dimensional form and presented graphically. The results provide a substantial insight in understanding the behavior of FGM rotating disks with constant thickness and different gradient parameter. Furthermore, the stress and deformation state of the disk at constant angular speed and limit angular speed is investigated to explain the existence of optimum gradient parameters.

  5. Varied effects of shear correction on thermal vibration of functionally graded material shells

    Directory of Open Access Journals (Sweden)

    C.C. Hong

    2014-12-01

    Full Text Available The effects of varied shear correction coefficient on the first-order transverse shear deformation result of functionally graded material (FGM thick circular cylindrical shells under thermal vibration are investigated and computed by using the generalized differential quadrature method. The computed and varied values of shear correction coefficient are usually functions of FGM power law index and environment temperature. In the thermoelastic stress–strain relations, the simpler form stiffness of FGM shells under linear temperature rise is considered. The equation of shear correction coefficient is derived and obtained by using the total strain energy principle. Two parametric effects: environment temperature and FGM power law index on the thermal stress and center deflection of FGM thick circular cylindrical shells are obtained and investigated.

  6. Static analysis of a functionally graded cylindrical shell with piezoelectric layers as sensor and actuator

    International Nuclear Information System (INIS)

    In this paper, an analytical approach to the static behavior of functionally graded material (FGM) cylindrical shells with simply supported edges is developed. The Poisson's ratios of the FGM shell are assumed to be constant, but it is the modulus of elasticity which varies continuously through the radial direction according to the exponential function. The shell has finite length and embedded piezoelectric layers. The partial differential equilibrium equations as well as the stress–displacement relations are reduced to the ordinary one with constant coefficient by using the Fourier series expansion. Finally, the problem is solved by using the state space method. Numerical results are given to demonstrate the accuracy of the presented method. The influences of the gradient index, applied voltage and radius to thickness ratios on the static behavior of FGM shells are also studied

  7. Enriched Element-Free Galerkin Method for Fracture Analysis of Functionally Graded Piezoelectric Materials

    Directory of Open Access Journals (Sweden)

    Guang Wei Meng

    2015-01-01

    Full Text Available A new method using the enriched element-free Galerkin method (EEFGM to model functionally graded piezoelectric materials (FGPMs with cracks was presented. To improve the solution accuracy, extended terms were introduced into the approximation function of the conventional element-free Galerkin method (EFGM to describe the displacement and electric fields near the crack. Compared with the conventional EFGM, the new approach requires smaller domain to describe the crack-tip singular field. Additionally, the domain of the nodes was not affected by the crack. Therefore, the visibility method and the diffraction method were no longer needed. The mechanical response of FGPM was discussed, when its material parameters changed exponentially in a certain direction. The modified J-integrals for FGPM were deduced, whose results were compared with the results of the conventional EFGM and the analytical solution. Numerical example results illustrated that this method is feasible and precise.

  8. Thermal shock resistance behavior of a functionally graded ceramic: Effects of finite cooling rate

    Directory of Open Access Journals (Sweden)

    Zhihe Jin

    2014-01-01

    Full Text Available This work presents a semi-analytical model to explore the effects of cooling rate on the thermal shock resistance behavior of a functionally graded ceramic (FGC plate with a periodic array of edge cracks. The FGC is assumed to be a thermally heterogeneous material with constant elastic modulus and Poisson's ratio. The cooling rate applied at the FGC surface is modeled using a linear ramp function. An integral equation method and a closed form asymptotic temperature solution are employed to compute the thermal stress intensity factor (TSIF. The thermal shock residual strength and critical thermal shock of the FGC plate are obtained using the SIF criterion. Thermal shock simulations for an Al2O3/Si3N4 FGC indicate that a finite cooling rate leads to a significantly higher critical thermal shock than that under the sudden cooling condition. The residual strength, however, is relatively insensitive to the cooling rate.

  9. Formation Behavior of Continuous Graded Composition in Ti-ZrO2 Functionally Graded Materials Fabricated by Mixed-Powder Pouring Method

    OpenAIRE

    Murali Jayachandran; Hideaki Tsukamoto; Hisashi Sato; Yoshimi Watanabe

    2013-01-01

    A mixed-powder pouring method has been proposed to fabricate functionally graded materials (FGMs) with the desired compositional gradient. The experimental procedure involves preparation of mixed powders consisting of more than two types of particles with different size and/or density, which exhibit different velocities in suspension and sedimentation to form the green body under gravity conditions. The green body was sintered by a spark plasma sintering (SPS) method. The initiation of the pa...

  10. Microstructure characterization of aluminium syntactic functionally graded composites containing hollow ceramic microspheres manufactured by radial centrifugal casting

    OpenAIRE

    Ferreira, S. C.; Velhinho, A.; L. A. Rocha; Fernandes, F. M. Braz

    2008-01-01

    Syntactic functionally graded metal matrix composites (SFGMMC) are a class of metallic foams in which closed porosity results from the presence of hollow ceramic microspheres (microballoons), whose spatial distribution varies continuously between the inner and the outer section of the part, thus resulting in a continuous variation in properties. In this work, aluminium-based SFGMMC rings were fabricated by radial centrifugal casting. The graded composition along the radial direction is contro...

  11. Electro-magneto-thermo-elastic response of infinite functionally graded cylinders without energy dissipation

    International Nuclear Information System (INIS)

    The electro-magneto-thermo-elastic analysis problem of an infinite functionally graded (FG) hollow cylinder is studied in the context of Green–Naghdi's (G–N) generalized thermoelasticity theory (without energy dissipation). Material properties are assumed to be graded in the radial direction according to a novel power-law distribution in terms of the volume fractions of the metal and ceramic constituents. The inner surface of the FG cylinder is pure metal whereas the outer surface is pure ceramic. The equations of motion and the heat-conduction equation are used to derive the governing second-order differential equations. A finite element scheme is presented for the numerical purpose. The system of differential equations is solved numerically and some plots for displacement, radial and electromagnetic stresses, and temperature are presented. The radial displacement, mechanical stresses and temperature as well as the electromagnetic stress are all investigated along the radial direction of the infinite cylinder. - Highlights: • The electro-magneto-thermo-elastic analysis problem of a FG cylinder is studied. • A finite element scheme is presented for the numerical purpose. • The results are investigated along the radial direction of the infinite cylinder. • It provides interesting information for all researchers working on this subject

  12. Verification of The Thermal Buckling Load in Plates Made of Functional Graded Material

    Directory of Open Access Journals (Sweden)

    Amran Ayob

    2010-12-01

    Full Text Available In this study, thermal buckling of thin plate made of Functionally Graded Materials (FGM with linearly varying thickness is considered. The material properties are also graded in the thickness direction according to a simple power law distribution in which the properties are stated in terms of the volume fractions of the constituents. All edges of the plate are simply supported. The equilibrium and stability equations of a FGM plate under thermal loads can be derived based on higher order plate theories via variation formulation, and are then used to determine the governing deferential equation of the plate and the pre-buckling forces. The buckling analysis of a FGM plate is conducted by assuming a uniform temperature rise, temperature gradient through the thickness, and linear temperature variation in the thickness. Closed–form solutions are obtained the buckling load defined in a weighted residual approach. In a special case the obtained results are compared with the results of FGM plates with uniform thickness. The influences of the plate thickness variation and the edge ratio on the critical loads are investigated. Different gradient exponent k, different geometries and loading conditions were studied.

  13. Microstructure and Properties of Thermally Sprayed Functionally Graded Coatings for Polymeric Substrates

    Science.gov (United States)

    Ivosevic, M.; Knight, R.; Kalidindi, S. R.; Palmese, G. R.; Sutter, J. K.

    2003-01-01

    The use of polymer matrix composites (PMCs) in the gas flow path of advanced turbine engines offers significant benefits for aircraft engine performance but their useful lifetime is limited by their poor erosion resistance. High velocity oxy-fuel (HVOF) sprayed polymer/cermet functionally graded (FGM) coatings are being investigated as a method to address this technology gap by providing erosion and oxidation protection to polymer matrix composites. The FGM coating structures are based on a polyimide matrix filled with varying volume fractions of WC-Co. The graded coating architecture was produced using a combination of internal and external feedstock injection, via two computer-controlled powder feeders and controlled substrate preheating. Porosity, coating thickness and volume fraction of the WC-Co filler retained in the coatings were determined using standard metallographic techniques and computer image analysis. The pull-off strength (often referred to as the adhesive strength) of the coatings was evaluated according to the ASTM D 4541 standard test method, which measured the greatest normal tensile force that the coating could withstand. Adhesive/cohesive strengths were determined for three different types of coating structures and compared based on the maximum indicated load and the surface area loaded. The nature and locus of the fractures were characterized according to the percent of adhesive and/or cohesive failure, and the tested interfaces and layers involved were analyzed by Scanning Electron Microscopy.

  14. Ni–Fe–Al$_2$O$_3$ electrodeposited nanocomposite coating with functionally graded microstructure

    Indian Academy of Sciences (India)

    V TORABINEJAD; A SABOUR ROUHAGHDAM; M ALIOFKHAZRAEI; M H ALLAHYARZADEH

    2016-06-01

    In this study, a Ni–Fe–Al$_2$O$_3$ nanocomposite coating was deposited on the substrate of low-carbon steel by electrodeposition from a sulphate-based bath. The effects of frequency and duty cycle were investigated to producethe functionally graded (FG) coating. For this purpose, first, the coatings with duty cycle-decreased method (DDM) were deposited in eight steps from 88 to 11%. At the second step, frequency-increased method (FIM) was utilized from 50 to 6400 Hz during eight steps. Assessing of coatings was carried out by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), potentiodynamic test, Vickers microhardness test and wear test.Microstructure evaluations gained by SEM and EDS demonstrated that the continuous alterations of duty cycle contribute for manufacturing of FG coatings, so that the maximum particle fraction was in the free surface of the coating and its amount was gradually decreased to the interface. These investigations showed that FIM had no effect on production of graded structure. Corrosion and wear tests indicated high corrosion and wear resistance of DDM coatings in comparison to FIM coatings. Investigating the best coatings obtained from both above methods exhibited 50 and 20% reduction in corrosion current density and wear rate, respectively, for DDM specimen in comparison to FIM sample.

  15. Design and Synthesis of Ti-ZrO2 Functionally Graded Materials

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Functionally graded materials (FGMs) based on titanium-zirconia system have been prepared by powder metallurgical method. The graded interlayer number and the compositional distribution have been designed by elastic finite element method. The interfacial microstructure between layers, the combining state of phases between Ti and ZrO2 have been investigated by means of XRD (X-ray diffraction), SEM (scanning electron microscope), EDS (energy dispersive spectrometer) and so on. The co-existing region of Ti and ZrO2 has been determined by thermodynamic calculation to control the sintering atmosphere. The experimental results show that the joint between Ti and ZrO2 phases is physical in this composite and ZrO2 mainly exists as tetragonal phase. The microstructure of Ti-ZrO2 system FGM exhibits a transition from a zirconia particle dispersion in a titanium matrix to an inverse dispersion of titanium in zirconia. The gradient structure of titanium and zirconia can relieve thermal stress.

  16. Electro-magneto-thermo-elastic response of infinite functionally graded cylinders without energy dissipation

    Energy Technology Data Exchange (ETDEWEB)

    Zenkour, Ashraf M., E-mail: zenkour@hotmail.com [Department of Mathematics, Faculty of Science, King Abdulaziz University, Jeddah 21589 (Saudi Arabia); Department of Mathematics, Faculty of Science, Kafrelsheikh University, Kafr El-Sheikh 33516 (Egypt); Abbas, Ibrahim A. [Department of Mathematics, Faculty of Science and Arts-Khulais, King Abdulaziz University, Jeddah (Saudi Arabia); Department of Mathematics, Faculty of Science, Sohag University, Sohag (Egypt)

    2015-12-01

    The electro-magneto-thermo-elastic analysis problem of an infinite functionally graded (FG) hollow cylinder is studied in the context of Green–Naghdi's (G–N) generalized thermoelasticity theory (without energy dissipation). Material properties are assumed to be graded in the radial direction according to a novel power-law distribution in terms of the volume fractions of the metal and ceramic constituents. The inner surface of the FG cylinder is pure metal whereas the outer surface is pure ceramic. The equations of motion and the heat-conduction equation are used to derive the governing second-order differential equations. A finite element scheme is presented for the numerical purpose. The system of differential equations is solved numerically and some plots for displacement, radial and electromagnetic stresses, and temperature are presented. The radial displacement, mechanical stresses and temperature as well as the electromagnetic stress are all investigated along the radial direction of the infinite cylinder. - Highlights: • The electro-magneto-thermo-elastic analysis problem of a FG cylinder is studied. • A finite element scheme is presented for the numerical purpose. • The results are investigated along the radial direction of the infinite cylinder. • It provides interesting information for all researchers working on this subject.

  17. Elaboration of functionally graded materials for plasma facing components of the thermonuclear machines

    International Nuclear Information System (INIS)

    The objective of this study was to develop a Functionally Graded Material (FGM) W/Cu to replace the compliance layer (Cu-OFHC) in the plasma facing components of thermonuclear fusion reactor like ITER. The peculiarity of this work is to elaborate these materials without exceeding the melting temperature of copper in order to control its microstructure. The co-sintering is the most attractive solution to achieve this goal. The first phase of this study has been to decrease the sintering temperature of the tungsten to achieve this co-sintering. The elaboration of a Functionally Graded Materials being delicate, thermomechanical calculations were performed in order to determine the number and chemical composition in order to increase the lifespan of Plasma Facing Components. Spark Plasma Sintering conditions were optimized in order to achieve maximum density of WxCu1-x composites. The effect of copper content and density of the WxCu1-x composites on thermal and mechanical properties was investigated. The SPS conditions were applied for W/CuCrZr assemblies with a compliance layer composed of several interlayers. The importance of time for the integrity of assemblies thereof has been highlighted. The study of the dwell time during W/CuCrZr assembly leads to identify a parameter to characterize the integrity of the interface regardless of the composition and the nature of the layer of compliance. Moreover, the phenomena associated with the formation of the interface assembly have been identified. The interface W/WxCu1-x is formed by the extrusion of the copper layer of the WxCu1-x inside the tungsten porosities. The WyCu1-y/CuCrZr interface is formed by copper migration of CuCrZr layer inside the WyCu1-y layer. Finally optimization assembly conditions showed that the mechanical stresses due to the densification of the Functionally Graded Materials can be limited by sintering the FGM before the assembly. (author)

  18. The Effect Of Ceramic In Combination Of Two Sigmoid Functionally Graded Rotating Disks With Variable Thickness

    DEFF Research Database (Denmark)

    Bayat, M.; Sahari, B. B.; Saleem, M.

    2012-01-01

    In this paper the elastic solutions of a disk composed of FGM – Functionaly Graded Material, is presented.......In this paper the elastic solutions of a disk composed of FGM – Functionaly Graded Material, is presented....

  19. Finite Element Analysis of Shrinkage in the Interface of Functionally Graded Concrete Segment Used in Shield Tunneling

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    In functionally graded materials (FGM), the problem of interface stability caused by the volume deformation is commonly regarded as the key factor for its performance. Based on test results, in terms of finite element method (FEM) this paper analyzed problems in the shrinkage of functionally graded material interface of shield concrete segment, which was designed and produced by the principle of functionally graded materials. In the analysis model, the total shrinkage of concrete was converted into the thermal shrinkage by means of the method of "Equivalent Temperature Difference". Consequently, the shrinkage stress of interface layer was calculated and compared with the bond strength of interface layer.The results indicated that the volume deformation of two-phase materials of functionally graded concrete (FGC) segment, which were the concrete cover and the concrete structure layer, showed better compatibility and the tension stress of interface layer, which was resulted from the shrinkage of concrete and calculated by ANSYS, was less than the bond strength of interface layer. Therefore, the interface stability of functionally graded concrete segment was good and the sliding deformation of interface layer would not generate.

  20. Interface Oscillation in the Side-by-Side (SBS) Tape Casting of Functionally Graded Ceramics (FGCs)

    DEFF Research Database (Denmark)

    Jabbari, Masoud; Bulatova, Regina; Hattel, Jesper Henri;

    2012-01-01

    slurries. The rheological behavior of the slurries are extracted from experiments and used in the ANSYS FLUENT commercial code to develop a fluid flow model for the non-Newtonian ceramic slurries and evaluate the interface oscillation between the stripes in SBS tape casting. The Numerical results show......Room temperature magnetic refrigeration is a new highly efficient and environmentally protective technology. Although it has not been maturely developed, it shows great applicable prosperity and seems to be a potential substitute for the traditional vapor compression technology. Tape Casting is a...... common process in producing multilayer ceramics, which now is used for producing side-by-side (SBS) functionally graded ceramics (FGCs). These FGCs are mostly used in the magnetic refrigeration sectors due to the varying composition of the magnetocaloric materials so that the magnetic transition...

  1. Bending and vibration of functionally graded material sandwich plates using an accurate theory

    CERN Document Server

    Natarajan, S

    2012-01-01

    In this paper, the bending and the free flexural vibration behaviour of sandwich functionally graded material (FGM) plates are investigated using QUAD-8 shear flexible element developed based on higher order structural theory. This theory accounts for the realistic variation of the displacements through the thickness. The governing equations obtained here are solved for static analysis considering two types of sandwich FGM plates, viz., homogeneous face sheets with FGM core and FGM face sheets with homogeneous hard core. The in-plane and rotary inertia terms are considered for vibration studies. The accuracy of the present formulation is tested considering the problems for which three-dimensional elasticity solutions are available. A detailed numerical study is carried out based on various higher-order models to examine the influence of the gradient index and the plate aspect ratio on the global/local response of different sandwich FGM plates.

  2. Influence of Inclusion Shape on Thermoelasto-Plastic Optimun Design of Ceramic Metal Functionally Graded Materials

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A nonlinear finite element method is applied to observe how inclusion shape influence the thermal response of a ceramic-metal functionally graded material (FGM).The elastic and plastic behaviors of the layers which are two-phase isotropic composites consisting of randomly oriented elastic spheroidal inclusions and a ductile matrix are predicted by a mean field method.The prediction results show that inclusion shape has remarkable influence on the overall behavior of the composite.The consequences of the thermal response analysis of the FGM are that the response is dependent on inclusion shape and its composition profile cooperatively and that the plastic behavior of each layer should be taken into account in optimum design of a ceramic-metal FGM.

  3. The beam-mode stability of periodic functionally-graded-material shells conveying fluid

    Science.gov (United States)

    Shen, Huijie; Païdoussis, Michael P.; Wen, Jihong; Yu, Dianlong; Wen, Xisen

    2014-05-01

    The characteristics of beam-mode stability of fluid-conveying shell systems are investigated in this paper for shells with clamped-free (cantilevered) boundary conditions. An FEM algorithm is developed to conduct the investigation. A periodic shell structure of functionally graded material (FGM), termed as PFGM shell here, is designed so as to enhance the stability for the shell system, and to eliminate the stress concentration problems that exist in periodic structures. Results show that by the introduction of periodic design the critical velocities can be raised over several desired ranges of the dimensionless fluid density β, and the stress concentration is effectively reduced in the PFGM shell. Finally, the effects of the geometric shape, material parameters and spring supports on the dynamical stability are probed.

  4. Transverse Vibration of Axially Moving Functionally Graded Materials Based on Timoshenko Beam Theory

    Directory of Open Access Journals (Sweden)

    Suihan Sui

    2015-01-01

    Full Text Available The transverse free vibration of an axially moving beam made of functionally graded materials (FGM is investigated using a Timoshenko beam theory. Natural frequencies, vibration modes, and critical speeds of such axially moving systems are determined and discussed in detail. The material properties are assumed to vary continuously through the thickness of the beam according to a power law distribution. Hamilton’s principle is employed to derive the governing equation and a complex mode approach is utilized to obtain the transverse dynamical behaviors including the vibration modes and natural frequencies. Effects of the axially moving speed and the power-law exponent on the dynamic responses are examined. Some numerical examples are presented to reveal the differences of natural frequencies for Timoshenko beam model and Euler beam model. Moreover, the critical speed is determined numerically to indicate its variation with respect to the power-law exponent, axial initial stress, and length to thickness ratio.

  5. Electromechanical buckling of functionally graded electrostatic nanobridges using strain gradient theory

    Science.gov (United States)

    Shojaeian, Milad; Beni, Yaghoub Tadi; Ataei, Hossein

    2016-01-01

    Electromechanical buckling (EMB) of beam-type nanoelectromechanical systems (NEMSs) is investigated based on modified strain gradient theory. The system is modeled as a clamped-guided nanobeam which is under compressive or tensile axial loads as well as the effect of nonlinear electrostatic and van der Waals symmetric transverse forces. In addition, the beam is considered to be made of axially and transverse functionally graded materials. Here, FGM is Poly-SiGe, of which the general properties change gradually from silicon to germanium based on a simple power-law method. Considering the Euler-Bernoulli beam theory and using the principle of minimum potential energy, the governing equations and corresponding boundary conditions are established. After validation of results, the effects of power law index, variation of size effect parameters, length-thickness ratio and the distance between the two fixed and movable electrodes on the buckling response of the system are discussed.

  6. Optimization of Natural Frequencies and Sound Power of Beams Using Functionally Graded Material

    Directory of Open Access Journals (Sweden)

    Nabeel T. Alshabatat

    2014-01-01

    Full Text Available This paper presents a design method to optimize the material distribution of functionally graded beams with respect to some vibration and acoustic properties. The change of the material distribution through the beam length alters the stiffness and the mass of the beam. This can be used to alter a specific beam natural frequency. It can also be used to reduce the sound power radiated from the vibrating beam. Two novel volume fraction laws are used to describe the material volume distributions through the length of the FGM beam. The proposed method couples the finite element method (for the modal and harmonic analysis, Lumped Parameter Model (for calculating the power of sound radiation, and an optimization technique based on Genetic Algorithm. As a demonstration of this technique, the optimization procedure is applied to maximize the fundamental frequency of FGM cantilever and clamped beams and to minimize the sound radiation from vibrating clamped FGM beam at a specific frequency.

  7. Analysis of macro and micro residual stresses in functionally graded materials by diffraction methods

    CERN Document Server

    Dantz, D; Reimers, W

    1999-01-01

    The residual stress state in microwave sintered metal-ceramic functionally graded materials (FGM) consisting of 8Y-ZrO/sub 2//Ni and 8Y-ZrO/sub 2//NiCr8020, respectively, was analysed by non- destructive diffraction methods. In $9 order to get knowledge of the complete residual stress state in the near surface region as well as in the interior of the material, complementary methods were applied. Whereas the surface was characterised by X-ray techniques using $9 conventional sources, the stresses within the bulk of the material were investigated by means of high energy synchrotron radiation. The stress state was found to obey the differences in the coefficients of thermal expansion $9 (micro-stresses) on the one hand and the inhomogeneous cooling conditions (macrostresses) on the other hand. (7 refs).

  8. Recent development in modeling and analysis of functionally graded materials and structures

    Science.gov (United States)

    Gupta, Ankit; Talha, Mohammad

    2015-11-01

    In this article, an extensive review related to the structural response of the functionally graded materials (FGMs) and structures have been presented. These are high technology materials developed by a group scientist in the late 1980's in Japan. The emphasis has been made here, to present the structural characteristics of FGMs plates/shells under thermo-electro-mechanical loadings under various boundary and environmental conditions. This paper also provides an overview of different fabrication procedures and the future research directions which is required to implement these materials in the design and analysis appropriately. The expected outcome of present review can be treated as milestone for future studies in the area of high technology materials and structures, and would be definitely advantageous for the researchers, scientists, and designers working in this field.

  9. Microstructure of titanium component in hydroxyapatite-Ti asymmetrical functionally graded biomaterial

    Institute of Scientific and Technical Information of China (English)

    储成林; 林萍华; 董寅生; 朱景川; 尹钟大

    2004-01-01

    The microstructure of the titanium component in hydroxyapatite (HA)-Ti asymmetrical functionally graded biomaterial (FGM) fabricated by powder metallurgical process was investigated.It is found that the main subthere of the Ti component in the FGM consists of screw dislocations whose Burgers vectors are 1/3and there are not deformation twins. Screw dislocations are straight and regularly distributed, and cross slip can be observed. The density of the dislocations in the Ti component increases with the rise of the content of the HA component in the FGM. The subgrain boundaries of the Ti component consist of dislocation network walls. Some microbands with bamboo-leaf-shape distribute regularly in Ti grains, which exhibit a specific orientation relationship with α-Ti parent phase.

  10. Manufacturing and testing W/Cu functionally graded material mock-ups for plasma facing components

    International Nuclear Information System (INIS)

    The W/Cu functionally graded material (FGM) mock-ups were manufactured by resistance sintering under ultrahigh pressure or three times hot pressing. The bonding strength of W/Cu FGM was determined by tensile and shearing tests. A thermodiffusion experiment was used for testing thermal conductivity of the region containing W, the first and second W-Cu alloy layers. High heat flux and thermal fatigue tests have been carried out using electron beam or laser. The results are that the specimens with higher density in the W layer have better performances in high heat flux and thermal fatigue tests. Using the above sintering techniques, W/Cu FGM mock-ups for plasma facing components have been successfully manufactured at less cost

  11. Low speed centrifugal casting of Functionally Graded solid cast ingot by anomalous particle distribution

    Science.gov (United States)

    Mer, K. K. S.; Ray, S.

    2011-12-01

    Functionally graded cylindrical ingot of Al-Al2O3 composite synthesized by centrifugal casting shows particle distribution and hardness decreasing radially from the outer radius to inner radius. The progressive decrease in alumina content and hardness from the outer radius towards the center may be attributed to higher centrifugal force acting on relatively denser alumina particles during rotation, as compared to that acting on lighter alloy melt. It is also observed, as one moves down from the top to the bottom of cast ingot the alumina content decreases. This is surprising in view of higher density of alumina particles relative to the melt. The particle settling should have resulted at more particles towards the bottom, but distribution observed is in contradiction.

  12. Parametric instability of a functionally graded Timoshenko beam on Winkler's elastic foundation

    Energy Technology Data Exchange (ETDEWEB)

    Mohanty, S.C., E-mail: scmohanty@nitrkl.ac.in [National Institute of Technology, Rourkela, Department of Mechanical Engineering, National Institute of Technology, Rourkela, Orissa 769008 (India); Dash, R.R., E-mail: rati_igit@yahoo.co.in [Indira Gandhi Institute of Technology, Sarang, Department of Mechanical Engineering, Indira Gandhi Institute of Technology, Sarang, Dist. Dhenkanal, Orissa 759146 (India); Rout, T., E-mail: troutwala@gmail.com [Indira Gandhi Institute of Technology, Sarang, Department of Mechanical Engineering, Indira Gandhi Institute of Technology, Sarang, Dist. Dhenkanal, Orissa 759146 (India)

    2011-08-15

    Highlights: > Winkler's elastic foundation enhances the stability of both FGO and FGSW beams with material properties distribution along the thickness as per power law and exponential law. > FGO beam with steel-rich bottom is more stable than a beam with aluminium-rich bottom for both the types of property distribution. > FGSW beam with the properties in FGM core varying as per power law becomes less stable with increase in core thickness. > Exponential variation of core properties enhances its stability with the increase in core thickness. - Abstract: This article presents an investigation of the dynamic stability of functionally graded ordinary (FGO) beam and functionally graded sandwich (FGSW) beam on Winkler's elastic foundation using finite element method. The material properties are assumed to follow both exponential and power law. It is found that the foundation enhances stability of the FGO beam for first three modes. The effect of distributions of material properties of the FGO beam on its parametric instability is investigated. It is found that the FGO beam with steel-rich bottom is more stable as compared to that with Al-rich bottom for all the three modes and for both the types of property distributions. The effect of property distribution on stability of FGSW beam with steel as bottom skin and alumina as top skin is also investigated. It is observed that the beam having properties in core according to exponential law is the most stable beam while the beam having properties in core as per power law with index 2.5 is the least stable beam. For an FGSW beam it is found that the increase in the thickness of FGM core makes the beam less stable when the properties in FGM vary as per power law whereas the stability of beam enhances with the increase of thickness of FGM core when the properties vary according to exponential law.

  13. Bifurcation and chaos of thin circular functionally graded plate in thermal environment

    International Nuclear Information System (INIS)

    Highlights: → We study bifurcations and chaotic dynamics of a FGM circular plate. → We consider the effect of temperature-dependent material properties. → Increasing volume fraction index will increase chaotic regions. → Increasing temperature will reduce chaotic regions. → The FGM plate exists chaotic motions, multiple periodic and periodic motions. - Abstract: A ceramic/metal functionally graded circular plate under one-term and two-term transversal excitations in the thermal environment is investigated, respectively. The effects of geometric nonlinearity and temperature-dependent material properties are both taken into account. The material properties of the functionally graded plate are assumed to vary continuously through the thickness, according to a power law distribution of the volume fraction of the constituents. Using the principle of virtual work, the nonlinear partial differential equations of FGM plate subjected to transverse harmonic forcing excitation and thermal load are derived. For the circular plate with clamped immovable edge, the Duffing nonlinear forced vibration equation is deduced using Galerkin method. The criteria for existence of chaos under one-term and two-term periodic perturbations are given with Melnikov method. Numerical simulations are carried out to plot the bifurcation curves for the homolinic orbits. Effects of the material volume fraction index and temperature on the criterions are discussed and the existences of chaos are validated by plotting phase portraits, Poincare maps. Also, the bifurcation diagrams and corresponding maximum Lyapunov exponents are plotted. It was found that periodic, multiple periodic solutions and chaotic motions exist for the FGM plate under certain conditions.

  14. Parametric instability of a functionally graded Timoshenko beam on Winkler's elastic foundation

    International Nuclear Information System (INIS)

    Highlights: → Winkler's elastic foundation enhances the stability of both FGO and FGSW beams with material properties distribution along the thickness as per power law and exponential law. → FGO beam with steel-rich bottom is more stable than a beam with aluminium-rich bottom for both the types of property distribution. → FGSW beam with the properties in FGM core varying as per power law becomes less stable with increase in core thickness. → Exponential variation of core properties enhances its stability with the increase in core thickness. - Abstract: This article presents an investigation of the dynamic stability of functionally graded ordinary (FGO) beam and functionally graded sandwich (FGSW) beam on Winkler's elastic foundation using finite element method. The material properties are assumed to follow both exponential and power law. It is found that the foundation enhances stability of the FGO beam for first three modes. The effect of distributions of material properties of the FGO beam on its parametric instability is investigated. It is found that the FGO beam with steel-rich bottom is more stable as compared to that with Al-rich bottom for all the three modes and for both the types of property distributions. The effect of property distribution on stability of FGSW beam with steel as bottom skin and alumina as top skin is also investigated. It is observed that the beam having properties in core according to exponential law is the most stable beam while the beam having properties in core as per power law with index 2.5 is the least stable beam. For an FGSW beam it is found that the increase in the thickness of FGM core makes the beam less stable when the properties in FGM vary as per power law whereas the stability of beam enhances with the increase of thickness of FGM core when the properties vary according to exponential law.

  15. Stochastic simulation of functionally graded materials with random porosity and volume fraction

    International Nuclear Information System (INIS)

    The stresses in traditional thermal barrier coatings (TBC's) can be unacceptably high due to sharp discontinuities in the thermal expansion coefficient between the thermally insulating material, often a ceramic, and the structural material, often a metal. Recently, functionally graded materials (FGM's), which are by definition non-homogeneous materials with a continuous variation in composition and/or microstructure in some spatial direction, have been developed in order to mitigate these high stresses at the material interface. This functional grading allows the material to achieve an optimal combination of properties such as strength, hardness, durability and wear/corrosion resistance, which distinguishes FGM's from conventional composites where uniform materials are joined along sharp boundaries. Computational efforts to successfully model and simulate FGM's are the subject of many studies, considering both analytical and finite element based techniques. Of fundamental importance to any such attempt is the accurate representation of the graded material properties. Despite the on-going efforts, very little work has been developed that treats the randomness inherent in their microstructure. This randomness is a natural consequence of the difficulty in manufacturing these materials to exact specifications. The major goal of this current research is to develop a numerical model that investigates the effects of microstructural randomness on the stress and temperature distribution in FGM's, based on stochastic simulation techniques. This will be achieved by assuming that porosity and metal volume fraction vary randomly around their specified through-thickness values and by assuming one-dimensional steady-state heat transfer. In order to perform stochastic simulations that reflect randomness in the FGM microstructure, the porosity and the metal/ceramic volume fraction are described by non-homogeneous stochastic fields, which are assumed homogeneous after normalization

  16. Functionally graded hydroxyapatite-alumina-zirconia biocomposite: Synergy of toughness and biocompatibility

    Energy Technology Data Exchange (ETDEWEB)

    Afzal, Mohammad Atif Faiz [Biomaterials Processing and Characterization Laboratory, Department of Materials Science and Engineering, Indian Institute of Technology Kanpur (India); Kesarwani, Pallavi [Visvesvaraya National Institute of Technology Nagpur (India); Reddy, K. Madhav; Kalmodia, Sushma [Laboratory for Biomaterials, Department of Materials Science and Engineering, Indian Institute of Technology Kanpur (India); Basu, Bikramjit [Materials Research Centre, Indian Institute of Science, Bangalore-560012 (India); Balani, Kantesh, E-mail: kbalani@iitk.ac.in [Biomaterials Processing and Characterization Laboratory, Department of Materials Science and Engineering, Indian Institute of Technology Kanpur (India); Laboratory for Biomaterials, Department of Materials Science and Engineering, Indian Institute of Technology Kanpur (India)

    2012-07-01

    Functionally Gradient Materials (FGM) are considered as a novel concept to implement graded functionality that otherwise cannot be achieved by conventional homogeneous materials. For biomedical applications, an ideal combination of bioactivity on the material surface as well as good physical property (strength/toughness/hardness) of the bulk is required in a designed FGM structure. In this perspective, the present work aims at providing a smooth gradation of functionality (enhanced toughening of the bulk, and retained biocompatibility of the surface) in a spark plasma processed hydroxyapatite-alumina-zirconia (HAp-Al{sub 2}O{sub 3}-YSZ) FGM bio-composite. In the current work HAp (fracture toughness {approx} 1.5 MPa.m{sup 1/2}) and YSZ (fracture toughness {approx} 6.2 MPa.m{sup 1/2}) are coupled with a transition layer of Al{sub 2}O{sub 3} allowing minimum gradient of mechanical properties (especially the fracture toughness {approx} 3.5 MPa.m{sup 1/2}). The in vitro cyto-compatibilty of HAp-Al{sub 2}O{sub 3}-YSZ FGM was evaluated using L929 fibroblast cells and Saos-2 Osteoblast cells for their adhesion and growth. From analysis of the cell viability data, it is evident that FGM supports good cell proliferation after 2, 3, 4 days culture. The measured variation in hardness, fracture toughness and cellular adhesion across the cross section confirmed the smooth transition achieved for the FGM (HAp-Al{sub 2}O{sub 3}-YSZ) nanocomposite, i.e. enhanced bulk toughness combined with unrestricted surface bioactivity. Therefore, such designed biomaterials can serve as potential bone implants. - Graphical abstract: Spark plasma sintered functionally gradient materials (FGM) eliciting the YSZ - Al{sub 2}O{sub 3}-YSZ and HAp-Al{sub 2}O{sub 3} interface with grading hardness, toughness and biocompatibility response. Highlights: Black-Right-Pointing-Pointer Development of functionally gradient material to serve as a potential bone implant. Black-Right-Pointing-Pointer Introduction

  17. Functionally graded hydroxyapatite-alumina-zirconia biocomposite: Synergy of toughness and biocompatibility

    International Nuclear Information System (INIS)

    Functionally Gradient Materials (FGM) are considered as a novel concept to implement graded functionality that otherwise cannot be achieved by conventional homogeneous materials. For biomedical applications, an ideal combination of bioactivity on the material surface as well as good physical property (strength/toughness/hardness) of the bulk is required in a designed FGM structure. In this perspective, the present work aims at providing a smooth gradation of functionality (enhanced toughening of the bulk, and retained biocompatibility of the surface) in a spark plasma processed hydroxyapatite-alumina-zirconia (HAp-Al2O3-YSZ) FGM bio-composite. In the current work HAp (fracture toughness ∼ 1.5 MPa.m1/2) and YSZ (fracture toughness ∼ 6.2 MPa.m1/2) are coupled with a transition layer of Al2O3 allowing minimum gradient of mechanical properties (especially the fracture toughness ∼ 3.5 MPa.m1/2). The in vitro cyto-compatibilty of HAp-Al2O3-YSZ FGM was evaluated using L929 fibroblast cells and Saos-2 Osteoblast cells for their adhesion and growth. From analysis of the cell viability data, it is evident that FGM supports good cell proliferation after 2, 3, 4 days culture. The measured variation in hardness, fracture toughness and cellular adhesion across the cross section confirmed the smooth transition achieved for the FGM (HAp-Al2O3-YSZ) nanocomposite, i.e. enhanced bulk toughness combined with unrestricted surface bioactivity. Therefore, such designed biomaterials can serve as potential bone implants. - Graphical abstract: Spark plasma sintered functionally gradient materials (FGM) eliciting the YSZ – Al2O3-YSZ and HAp-Al2O3 interface with grading hardness, toughness and biocompatibility response. Highlights: ► Development of functionally gradient material to serve as a potential bone implant. ► Introduction of Aluminum oxide and Yttria Stabilized Zirconia (YSZ) cushion layer. ► Smooth fracture toughness gradient between hydroxyapatite and YSZ interface.

  18. Basic solutions of multiple parallel symmetric mode-III cracks in functionally graded piezoelectric/piezomagnetic material plane

    Institute of Scientific and Technical Information of China (English)

    泮世东; 周振功; 吴林志

    2013-01-01

    The Schmidt method is adopted to investigate the fracture problem of mul-tiple parallel symmetric and permeable finite length mode-III cracks in a functionally graded piezoelectric/piezomagnetic material plane. This problem is formulated into dual integral equations, in which the unknown variables are the displacement jumps across the crack surfaces. In order to obtain the dual integral equations, the displacement jumps across the crack surfaces are directly expanded as a series of Jacobi polynomials. The results show that the stress, the electric displacement, and the magnetic flux intensity factors of cracks depend on the crack length, the functionally graded parameter, and the distance among the multiple parallel cracks. The crack shielding effect is also obviously presented in a functionally graded piezoelectric/piezomagnetic material plane with mul-tiple parallel symmetric mode-III cracks.

  19. Longitudinal Investigation of Adaptive Functioning Following Conformal Irradiation for Pediatric Craniopharyngioma and Low-Grade Glioma

    International Nuclear Information System (INIS)

    Purpose: Children treated for brain tumors with conformal radiation therapy experience preserved cognitive outcomes. Early evidence suggests that adaptive functions or independent-living skills may be spared. This longitudinal investigation prospectively examined intellectual and adaptive functioning during the first 5 years following irradiation for childhood craniopharyngioma and low-grade glioma (LGG). The effect of visual impairment on adaptive outcomes was investigated. Methods and Materials: Children with craniopharyngioma (n=62) and LGG (n=77) were treated using conformal or intensity modulated radiation therapy. The median age was 8.05 years (3.21-17.64 years) and 8.09 years (2.20-19.27 years), respectively. Serial cognitive evaluations including measures of intelligence quotient (IQ) and the Vineland Adaptive Behavior Scales (VABS) were conducted at preirradiation baseline, 6 months after treatment, and annually through 5 years. Five hundred eighty-eight evaluations were completed during the follow-up period. Results: Baseline assessment revealed no deficits in IQ and VABS indices for children with craniopharyngioma, with significant (P<.05) longitudinal decline in VABS Communication and Socialization indices. Clinical factors associated with more rapid decline included females and preirradiation chemotherapy (interferon). The only change in VABS Daily Living Skills correlated with IQ change (r=0.34; P=.01) in children with craniopharyngioma. Children with LGG performed below population norms (P<.05) at baseline on VABS Communication, Daily Living Indices, and the Adaptive Behavior Composite, with significant (P<.05) longitudinal decline limited to VABS Communication. Older age at irradiation was a protective factor against longitudinal decline. Severe visual impairment did not independently correlate with poorer adaptive outcomes for either tumor group. Conclusions: There was relative sparing of postirradiation functional outcomes over time in this sample

  20. Longitudinal Investigation of Adaptive Functioning Following Conformal Irradiation for Pediatric Craniopharyngioma and Low-Grade Glioma

    Energy Technology Data Exchange (ETDEWEB)

    Netson, Kelli L. [Department of Psychiatry and Behavioral Sciences, Kansas University School of Medicine—Wichita, Kansas (United States); Conklin, Heather M. [Department of Psychology, St Jude Children' s Research Hospital, Memphis, Tennessee (United States); Wu, Shengjie; Xiong, Xiaoping [Department of Biostatistics, St Jude Children' s Research Hospital, Memphis, Tennessee (United States); Merchant, Thomas E., E-mail: thomas.merchant@stjude.org [Division of Radiation Oncology, St Jude Children' s Research Hospital, Memphis, Tennessee (United States)

    2013-04-01

    Purpose: Children treated for brain tumors with conformal radiation therapy experience preserved cognitive outcomes. Early evidence suggests that adaptive functions or independent-living skills may be spared. This longitudinal investigation prospectively examined intellectual and adaptive functioning during the first 5 years following irradiation for childhood craniopharyngioma and low-grade glioma (LGG). The effect of visual impairment on adaptive outcomes was investigated. Methods and Materials: Children with craniopharyngioma (n=62) and LGG (n=77) were treated using conformal or intensity modulated radiation therapy. The median age was 8.05 years (3.21-17.64 years) and 8.09 years (2.20-19.27 years), respectively. Serial cognitive evaluations including measures of intelligence quotient (IQ) and the Vineland Adaptive Behavior Scales (VABS) were conducted at preirradiation baseline, 6 months after treatment, and annually through 5 years. Five hundred eighty-eight evaluations were completed during the follow-up period. Results: Baseline assessment revealed no deficits in IQ and VABS indices for children with craniopharyngioma, with significant (P<.05) longitudinal decline in VABS Communication and Socialization indices. Clinical factors associated with more rapid decline included females and preirradiation chemotherapy (interferon). The only change in VABS Daily Living Skills correlated with IQ change (r=0.34; P=.01) in children with craniopharyngioma. Children with LGG performed below population norms (P<.05) at baseline on VABS Communication, Daily Living Indices, and the Adaptive Behavior Composite, with significant (P<.05) longitudinal decline limited to VABS Communication. Older age at irradiation was a protective factor against longitudinal decline. Severe visual impairment did not independently correlate with poorer adaptive outcomes for either tumor group. Conclusions: There was relative sparing of postirradiation functional outcomes over time in this sample

  1. In-situ Observation of Ongoing Microstructural Changes in Functionally Graded Thermal Spray Coating during Mechanical Loading

    Czech Academy of Sciences Publication Activity Database

    Mušálek, Radek; Vilémová, Monika; Matějíček, Jiří; Taltavull, C.; Lopez Galisteo, A.J.

    India : Valardocs, 2015 - (Sudarshan, T.; Vuoristo, P.; Koivuluoto, H.), s. 571-578 ISBN 978-81-926196-1-3. [International Conference on Surface Modification Technologies/28./. Tampere (FI), 16.06.2014-18.06.2014] R&D Projects: GA ČR(CZ) GPP108/12/P552 Institutional support: RVO:61389021 Keywords : thermal spray coating * fracture * failure process * in-situ observation * functionally graded materials Subject RIV: JK - Corrosion ; Surface Treatment of Materials http://www.researchgate.net/publication/277330034_In-situ_Observation_of_Ongoing_Microstructural_Changes_in_Functionally_Graded_Thermal_Spray_Coating_during_Mechanical_Loading

  2. PREFACE: 12th International Symposium on Multiscale, Multifunctional and Functionally Graded Materials (FGM 2012)

    Science.gov (United States)

    Zhou, Zhangjian; Li, Jingfeng; Zhang, Lianmeng; Ge, Changchun

    2013-03-01

    The 12th International Symposium on Multiscale, Multifunctional and Functionally Graded Materials (FGM-2012) was held in Beijing, China, from 22-36 October 2012. This was part of a series of conferences organized every two years endorsed by International Advisory Committee for FGM's, which serves as a forum for scientists, educators, engineers and young students interested in the development of functionally graded materials (FGM). The series continues from the previous international symposium on FGM held in Sendai, Japan (1990), San Francisco, USA (1992), Lausanne, Switzerland (1994), Tsukuba, Japan (1996), Dresden, Germany (1998), Estes Park, USA (2000), Beijing, China (2002), Leuven, Belgium (2004), Hawaii, USA (2006), Sendai, Japan (2008) and Guimaraes, Portugal (2010). Functionally graded materials are non-uniform materials which are designed with embodied continuous spatial variations in composition and microstructure for the specific purpose of adjusting their thermal, structural, mechanical, biological or functional response to specific application conditions. Such multi-phase materials cover a range of space and time scales, and are best understood by means of a comprehensive multiscale, multiphysics approach. These kinds of materials are presently in the forefront of materials research, receiving worldwide attention. They have a broad range of applications including for example, biomedical, biomechanical, automotive, aerospace, mechanical, civil, nuclear, and naval engineering. New applications are continuously being discovered and developed. The objective of the FGM-2012 intends to provide opportunities for exchanging ideas and discussing state-of-the-art theories, techniques and applications in the fields of multiscale, multifunctional and FGM, through invited lectures, oral and poster presentations. FGM-2012 was organized and hosted by University of Science and Technology Beijing, China, together with Tsing-hua University and Wuhan University of

  3. Numerical modeling of wave propagation in functionally graded materials using time-domain spectral Chebyshev elements

    Science.gov (United States)

    Hedayatrasa, Saeid; Bui, Tinh Quoc; Zhang, Chuanzeng; Lim, Chee Wah

    2014-02-01

    Numerical modeling of the Lamb wave propagation in functionally graded materials (FGMs) by a two-dimensional time-domain spectral finite element method (SpFEM) is presented. The high-order Chebyshev polynomials as approximation functions are used in the present formulation, which provides the capability to take into account the through thickness variation of the material properties. The efficiency and accuracy of the present model with one and two layers of 5th order spectral elements in modeling wave propagation in FGM plates are analyzed. Different excitation frequencies in a wide range of 28-350 kHz are investigated, and the dispersion properties obtained by the present model are verified by reference results. The through thickness wave structure of two principal Lamb modes are extracted and analyzed by the symmetry and relative amplitude of the vertical and horizontal oscillations. The differences with respect to Lamb modes generated in homogeneous plates are explained. Zero-crossing and wavelet signal processing-spectrum decomposition procedures are implemented to obtain phase and group velocities and their dispersion properties. So it is attested how this approach can be practically employed for simulation, calibration and optimization of Lamb wave based nondestructive evaluation techniques for the FGMs. The capability of modeling stress wave propagation through the thickness of an FGM specimen subjected to impact load is also investigated, which shows that the present method is highly accurate as compared with other existing reference data.

  4. ANALYSIS OF A CRACK IN A FUNCTIONALLY GRADED STRIP WITH A POWER FORM SHEAR MODULUS

    Institute of Scientific and Technical Information of China (English)

    Jinju Ma; Zheng Zhong; Chuanzeng Zhang

    2009-01-01

    The plane strain problem of a crack in a functionally graded strip with a power form shear modulus is studied. The governing equation in terms of Airy's stress function is solved exactly by means of Fourier transform. The mixed boundary problem is then reduced to a system of singular integral equations and is solved numerically to obtain the stress intensity factor at crack-tip. The maximum circumferential stress criterion and the strain energy density criterion are both employed to predict the direction of crack initiation. Numerical examples are given to show the influence of the material gradation models and the crack sizes on the mode-Ⅰ and mode-Ⅱ stress intensity factors. The dependence of the critical kink-angle on the crack size is examined and it is found that the crack kink-angle decreases with the increase of the normalized crack length, indicating that a longer crack tends to follow the original crack-line while it is much easier for a shorter crack to deviate from the original crack-line.

  5. Analysis of Sigmoid Functionally Graded Material (S-FGM Nanoscale Plates Using the Nonlocal Elasticity Theory

    Directory of Open Access Journals (Sweden)

    Woo-Young Jung

    2013-01-01

    Full Text Available Based on a nonlocal elasticity theory, a model for sigmoid functionally graded material (S-FGM nanoscale plate with first-order shear deformation is studied. The material properties of S-FGM nanoscale plate are assumed to vary according to sigmoid function (two power law distribution of the volume fraction of the constituents. Elastic theory of the sigmoid FGM (S-FGM nanoscale plate is reformulated using the nonlocal differential constitutive relations of Eringen and first-order shear deformation theory. The equations of motion of the nonlocal theories are derived using Hamilton’s principle. The nonlocal elasticity of Eringen has the ability to capture the small scale effect. The solutions of S-FGM nanoscale plate are presented to illustrate the effect of nonlocal theory on bending and vibration response of the S-FGM nanoscale plates. The effects of nonlocal parameters, power law index, aspect ratio, elastic modulus ratio, side-to-thickness ratio, and loading type on bending and vibration response are investigated. Results of the present theory show a good agreement with the reference solutions. These results can be used for evaluating the reliability of size-dependent S-FGM nanoscale plate models developed in the future.

  6. Fracture Behavior and Properties of Functionally Graded Fiber-Reinforced Concrete

    International Nuclear Information System (INIS)

    In concrete pavements, a single concrete mixture design is selected to resist mechanical loading without attempting to adversely affect the concrete pavement shrinkage, ride quality, or noise attenuation. An alternative approach is to design distinct layers within the concrete pavement surface which have specific functions thus achieving higher performance at a lower cost. The objective of this research was to address the structural benefits of functionally graded concrete materials (FGCM) for rigid pavements by testing and modeling the fracture behavior of different combinations of layered plain and synthetic fiber-reinforced concrete materials. Fracture parameters and the post-peak softening behavior were obtained for each FGCM beam configuration by the three point bending beam test. The peak loads and initial fracture energy between the plain, fiber-reinforced, and FGCM signified similar crack initiation. The total fracture energy indicated improvements in fracture behavior of FGCM relative to full-depth plain concrete. The fracture behavior of FGCM depended on the position of the fiber-reinforced layer relative to the starter notch. The fracture parameters of both fiber-reinforced and plain concrete were embedded into a finite element-based cohesive zone model. The model successfully captured the experimental behavior of the FGCMs and predicted the fracture behavior of proposed FGCM configurations and structures. This integrated approach (testing and modeling) demonstrates the viability of FGCM for designing layered concrete pavements system

  7. Management of Grade III Mobile Anterior Tooth in Function Using Endostabilizer – A Case Report

    OpenAIRE

    Kokane, Vandana B; Swapnil N Patil

    2014-01-01

    Impact of implant dentistry is such that today very few dentists think about saving grade III mobile anterior teeth. A patient with grade III mobility of central incisor due to apical root resorption was treated by using 80 no.stainless steel ‘H’ file as endostabiliser and one year follow up was done. Endostabiliser reduced the mobility of grade III mobile teeth drastically, immediately after its placement. Tooth was absolutely asymptomatic throughout one year follow up.

  8. Membranes for periodontal regeneration: From commercially available to spatially designed and functionally graded materials

    Science.gov (United States)

    Bottino, Marco Cicero

    The aging of the global population will lead to a considerable increase in the number of surgical and restorative procedures related to oral rehabilitation or periodontal regeneration. Periodontitis is one of the most aggressive pathologies that concern the integrity of the periodontal system that can lead to the destruction of the periodontium. Guided tissue and guided bone regeneration (GTR/GBR) have been used for the repair and regeneration of periodontal tissues by utilizing an occlusive membrane. The goal of this dissertation is to advance the knowledge in the area of periodontal regeneration by investigating the properties of a commercially available freeze-dried collagen-based graft (AlloDermRTM) and by designing/fabricating a functionally graded membrane (FGM) via multilayer electrospinning. The effects of different rehydration times and of a simultaneous rehydration/crosslinking procedure on the biomechanical properties and matrix stability of the commercially available membrane were investigated. The results revealed that there are significant changes on the biomechanical properties of the graft as rehydration time increases. Moreover, it was demonstrated that the simultaneous rehydration/crosslinking protocol has a synergistic effect in terms of enhancing biomechanical properties. A FGM consisting of a core-layer (CL) and two functional surface-layers (SL) was fabricated via sequential electrospinning. Hydroxyapatite nanoparticles (n-HAp) were incorporated to enhance bone formation (SL facing bone defect), and metronidazole benzoate (MET) was added to prevent bacterial colonization (SL facing the epithelial tissue). Degradation studies performed on both the CL and the FGM confirmed that the design holds promise in terms of providing the required mechanical stability to avoid membrane collapse and, therefore, enhance bone regeneration. Finally, it was demonstrated that MET incorporation into the SL that would face epithelial tissue is effective in

  9. Cytotoxicity of Protein-Carbon Nanotubes on J774 Macrophages Is a Functionalization Grade-Dependent Effect

    Directory of Open Access Journals (Sweden)

    Silvia Lorena Montes-Fonseca

    2015-01-01

    Full Text Available Carbon nanotubes (CNTs are used as carriers in medicine due to their ability to be functionalized with chemical substances. However, cytotoxicity analysis is required prior to use for in vivo models. The aim of this study was to evaluate the cytotoxic effect of CNTs functionalized with a 46 kDa surface protein from Entamoeba histolytica (P46-CNTs on J774A macrophages. With this purpose, CNTs were synthesized by spray pyrolysis and purified (P-CNTs using sonication for 48 h. A 46 kDa protein, with a 4.6–5.4 pI range, was isolated from E. histolytica HM1:IMSS strain trophozoites using an OFFGEL system. The P-CNTs were functionalized with the purified 46 kDa protein, classified according to their degree of functionalization, and characterized by Raman and Infrared spectroscopy. In vitro cytotoxicity was evaluated by MTT, apoptosis, and morphological assays. The results demonstrated that P46-CNTs exhibited cytotoxicity dependent upon the functionalized grade. Contrary to what was expected, P46-CNTs with a high grade of functionalization were more toxic to J774 macrophages than P46-CNTs with a low grade of functionalization, than P-CNTs, and had a similar level of toxicity as UP-CNT. This suggests that the nature of the functionalized protein plays a key role in the cytotoxicity of these nanoparticles.

  10. School Grades and Responsibility for Younger Siblings: An Empirical Study of the "Teaching Function."

    Science.gov (United States)

    Smith, Thomas Ewin

    1984-01-01

    A study based on the confluence model of family effects upon intellectual growth found a negative relationship between grades and the number of older siblings for Whites but not for Blacks and a negative relationship between the grades of Blacks and responsibility for younger siblings. (CMG)

  11. A mathematical model for smart functionally graded beam integrated with shape memory alloy actuators

    Energy Technology Data Exchange (ETDEWEB)

    Sepiani, H.; Ebrahimi, F. [University of Tehran, Tehran (Iran, Islamic Republic of); Karimipour, H. [Iran University of Science and Technology, Tehran (Iran, Islamic Republic of)

    2009-12-15

    This paper presents a theoretical study of the thermally driven behavior of a shape memory alloy (SMA)/FGM actuator under arbitrary loading and boundary conditions by developing an integrated mathematical model. The model studied is established on the geometric parameters of the three-dimensional laminated composite box beam as an actuator that consists of a functionally graded core integrated with SMA actuator layers with a uniform rectangular cross section. The constitutive equation and linear phase transformation kinetics relations of SMA layers based on Tanaka and Nagaki model are coupled with the governing equation of the actuator to predict the stress history and to model the thermo-mechanical behavior of the smart shape memory alloy/FGM beam. Based on the classical laminated beam theory, the explicit solution to the structural response of the structure, including axial and lateral deflections of the structure, is investigated. As an example, a cantilever box beam subjected to a transverse concentrated load is solved numerically. It is found that the changes in the actuator's responses during the phase transformation due to the strain recovery are significant

  12. Thermal Buckling and Free Vibration Analysis of Heated Functionally Graded Material Beams

    Directory of Open Access Journals (Sweden)

    Khalane Sanjay Anandrao

    2013-05-01

    Full Text Available The effect of temperature dependency of material properties on thermal buckling and free vibration of functionally graded material (FGM beams is studied. The FGM beam is assumed to be at a uniform through thickness temperature, above the ambient temperature. Finite element system of equations based on the first order shear deformation theory is developed. FGM beam with axially immovable ends having the classical boundary conditions is analysed. An exhaustive set of numerical results, in terms of buckling temperatures and frequencies, is presented, considering the temperature independent and temperature dependent material properties. The buckling temperature and fundamental frequency obtained using the temperature independent material properties is higher than that obtained by using the temperature dependent material properties, for all the material distributions, geometrical parameters in terms of length to thickness ratios and the boundary conditions considered. It is also observed that the frequencies of the FGM beam will reduce with the increase in temperature. This observation is applicable for the higher modes of vibration also. The necessity of considering the temperature dependency of material properties in determining thermal buckling and vibration characteristics of FGM beams is clearly demonstrated.Defence Science Journal, 2013, 63(3, pp.315-322, DOI:http://dx.doi.org/10.14429/dsj.63.2370

  13. Free Vibration and Dynamic Stability of Functionally Graded Material Plates on Elastic Foundation

    Directory of Open Access Journals (Sweden)

    I. Ramu

    2015-05-01

    Full Text Available The study of parametric resonance characteristics of functionally-graded material (FGM plates on elastic foundation is proposed under biaxial in plane periodic load. Finite element method in conjunction with Hamilton’s principle is utilised to establish the governing equations in a discrete form, Floquet’s theory was applied to determine the instability regions of FGM plate resting on elastic foundation. The effects of power law index, temperature rise, and foundation coefficients on the natural frequencies and dynamic stability of the plate have been examined in detail through parametric studies. The first two natural frequencies decrease with increase in temperature and power law index values, on the contrary, these two frequencies increase with increase in the foundation constants. Increase in power law index enhances the instability of the FGM plate. Increased foundation stiffness enhances the stability of the plate. Influence of shear layer constant is more dominant compared to the Winkler foundation constant.Defence Science Journal, Vol. 65, No. 3, May 2015, pp.245-251, DOI: http://dx.doi.org/10.14429/dsj.65.8621

  14. Synthesis and microwave absorbing characteristics of functionally graded carbonyl iron/polyurethane composites

    Science.gov (United States)

    Yang, R. B.; Liang, W. F.; Wu, C. H.; Chen, C. C.

    2016-05-01

    Radar absorbing materials (RAMs) also known as microwave absorbers, which can absorb and dissipate incident electromagnetic wave, are widely used in the fields of radar-cross section reduction, electromagnetic interference (EMI) reduction and human health protection. In this study, the synthesis of functionally graded material (FGM) (CI/Polyurethane composites), which is fabricated with semi-sequentially varied composition along the thickness, is implemented with a genetic algorithm (GA) to optimize the microwave absorption efficiency and bandwidth of FGM. For impedance matching and broad-band design, the original 8-layered FGM was obtained by the GA method to calculate the thickness of each layer for a sequential stacking of FGM from 20, 30, 40, 50, 60, 65, 70 and 75 wt% of CI fillers. The reflection loss of the original 8-layered FGM below -10 dB can be obtained in the frequency range of 5.12˜18 GHz with a total thickness of 9.66 mm. Further optimization reduces the number of the layers and the stacking sequence of the optimized 4-layered FGM is 20, 30, 65, 75 wt% with thickness of 0.8, 1.6, 0.6 and 1.0 mm, respectively. The synthesis and measurement of the optimized 4-layered FGM with a thickness of 4 mm reveal a minimum reflection loss of -25.2 dB at 6.64 GHz and its bandwidth below - 10 dB is larger than 12.8 GHz.

  15. Effect of anisotropy on creep behavior in a functionally graded material disc of variable thickness

    Science.gov (United States)

    Gupta, Vandana; Singh, S. B.

    2014-09-01

    In this paper, an effort has been made to study the effect of anisotropy on the steady state creep behavior in the functionally graded material disc with hyperbolic thickness made of Al-SiC (particle). The content of silicon carbide particles in the disc is assumed to decrease linearly from the inner to the outer radius of the disc. The creep behavior of the disc under stresses developing due to rotation at 15,000 rpm has been determined by Sherby's law. The creep parameters of the FGM disc vary along the radial distance due to varying composition and this variation has been estimated by regression fit of the available experimental data. The creep response of rotating disc is expressed by a threshold stress with value of stress exponent as 8. The study reveals that the anisotropy has a significant effect on the steady state creep response of rotating FGM disc. Thus, the care to introduce anisotropy should be taken for the safe design of the rotating FGM disc with hyperbolic thickness.

  16. Fabrication of W–Cu functionally graded material with improved mechanical strength

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Pei [Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); Graduate School of the Chinese Academy of Sciences, Beijing 100039 (China); Guo, Shibin; Liu, Guanghua; Chen, Yixiang [Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); Li, Jiangtao, E-mail: ljt0012@vip.sina.com [Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China)

    2014-07-15

    Highlights: • We prepared W–Cu FGM, valuable for nuclear fusion, by a new method in a short time. • Some of the Cu grains which were surrounded by W were about 50 nm. • The prepared W–Cu showed 15% higher bending strength than commercial W–Cu products. • The prepared W–Cu also showed a better plasticity than commercial W–Cu products. - Abstract: W–Cu functionally graded material (FGM) is prepared by a novel method of high-gravity combustion synthesis and melt-infiltration in a short time. In the W–Cu FGM, W grains are micron-sized and partially sintered to form an incomplete net structure, the Cu grains surrounded by W are about 50 nm, and lots of dislocations exist in the Cu phase. The W-rich layer shows both better strength and plasticity than the commercial W–Cu composite with a similar composition prepared by a conventional infiltration method.

  17. Geometrically Nonlinear Static Analysis of Edge Cracked Timoshenko Beams Composed of Functionally Graded Material

    Directory of Open Access Journals (Sweden)

    Şeref Doğuşcan Akbaş

    2013-01-01

    Full Text Available Geometrically nonlinear static analysis of edge cracked cantilever Timoshenko beams composed of functionally graded material (FGM subjected to a nonfollower transversal point load at the free end of the beam is studied with large displacements and large rotations. Material properties of the beam change in the height direction according to exponential distributions. The cracked beam is modeled as an assembly of two subbeams connected through a massless elastic rotational spring. In the study, the finite element of the beam is constructed by using the total Lagrangian Timoshenko beam element approximation. The nonlinear problem is solved by using incremental displacement-based finite element method in conjunction with Newton-Raphson iteration method. The convergence study is performed for various numbers of finite elements. In the study, the effects of the location of crack, the depth of the crack, and various material distributions on the nonlinear static response of the FGM beam are investigated in detail. Also, the difference between the geometrically linear and nonlinear analysis of edge cracked FGM beam is investigated in detail.

  18. Functionally Graded Aluminum Foam Fabricated by Friction Powder Sintering Process with Traversing Tool

    Science.gov (United States)

    Hangai, Yoshihiko; Morita, Tomoaki; Koyama, Shinji; Kuwazuru, Osamu; Yoshikawa, Nobuhiro

    2016-07-01

    Functionally graded aluminum foam (FG Al foam) is a new class of Al foam in which the pore structure varies over the foam, resulting in corresponding variations in the mechanical properties of the foam. In this study, FG Al foam plates were fabricated by a friction powder sintering (FPS) process with a traversing tool that is based on a previously developed sintering and dissolution process. The variation of the mechanical properties was realized by setting the volume fraction φ of NaCl in the mixture to 60, 70, and 80%. Long FG Al foam plates were fabricated with a length equal to the tool traversing length with φ varying in the tool traversing direction. From x-ray computed tomography observation, it was shown that the density of the Al foam decreased with increasing φ. In contrast, almost uniform pore structures were obtained in each area. According to the results of compression tests on each area, the plateau stress and energy absorption tended to decrease with increasing φ. Therefore, it was shown that FG Al foam plates with varying mechanical properties can be fabricated by the FPS process with the traversing tool.

  19. Compressive properties of sandwiches with functionally graded rubber core and jute–epoxy skins

    Indian Academy of Sciences (India)

    M R Doddamani; S M Kulkarni

    2013-04-01

    The compressive behaviour of a new class of sandwich composite made up of jute fiber reinforced epoxy skins and piece-wise linear fly ash reinforced functionally graded (FG) rubber core is investigated in flat-wise mode. FG samples are prepared using conventional casting technique. Presence of gradation is quantified physically by weight method. This paper addresses the effect of weight fraction of fly ash, core to thickness ratio (C/H) and orientation of jute on specific compressive modulus and strength. In each trial five replicates are tested with lower amount of fly ash below the upper skin of sandwich (rubber-up). Results of experimentation are subjected to statistical analysis of variance (ANOVA) to find the influential factor governing the compressive behaviour. Furthermore piece-wise linear gradation is modeled in finite element and strength values are compared with experimental results. Sandwich sample with fly ash content of 40%, C/H of 0.4 and orientations of 30°/60° registered better performance. Specific strength is observed to increase upto 30% filler content followed by stabilization. Finite element results for strength match very well with experimental ones.

  20. A mathematical model for smart functionally graded beam integrated with shape memory alloy actuators

    International Nuclear Information System (INIS)

    This paper presents a theoretical study of the thermally driven behavior of a shape memory alloy (SMA)/FGM actuator under arbitrary loading and boundary conditions by developing an integrated mathematical model. The model studied is established on the geometric parameters of the three-dimensional laminated composite box beam as an actuator that consists of a functionally graded core integrated with SMA actuator layers with a uniform rectangular cross section. The constitutive equation and linear phase transformation kinetics relations of SMA layers based on Tanaka and Nagaki model are coupled with the governing equation of the actuator to predict the stress history and to model the thermo-mechanical behavior of the smart shape memory alloy/FGM beam. Based on the classical laminated beam theory, the explicit solution to the structural response of the structure, including axial and lateral deflections of the structure, is investigated. As an example, a cantilever box beam subjected to a transverse concentrated load is solved numerically. It is found that the changes in the actuator's responses during the phase transformation due to the strain recovery are significant

  1. Fabrication of Al2O3-W Functionally Graded Materials by Slipcasting Method

    International Nuclear Information System (INIS)

    We have successfully fabricated a functionally graded material (FGM) from tungsten and alumina powders by a slip-casting method. This FGM has applications as a sealing and conducting component for high-intensity discharge lamps (HiDLs) that have a translucent alumina envelope. Two types of W powder, with different oxidizing properties, were used as the raw powders for the Al2O3-W FGM. 'Oxidized W' was prepared by heat-treatment at 200 deg. C for 180 min in air. Alumina and each of the W powders were mixed in ultrapure water by ultrasonic stirring. The slurry was then cast into a cylindrical acrylic mold, which had a base of porous alumina, under controlled pressure. The green compacts were subsequently dried, and then sintered using a vacuum furnace at 1600 deg. C for a fixed time. The microstructures of the FGMs were observed by scanning electron microscopy (SEM) of the polished section. The Al2O3-W FGM with the 'oxidized W' powder resulted in a microscopic compositional gradient. However, the FGM with 'as-received W' showed no compositional gradient. This result was mainly attributed to the difference between the ζ-potentials of the W powders with the different oxidizing conditions; basically 'oxidized W' powder tends to disperse because of the larger ζ-potential of the oxide layer coated on the W powder core.

  2. Fabrication of W–Cu functionally graded material with improved mechanical strength

    International Nuclear Information System (INIS)

    Highlights: • We prepared W–Cu FGM, valuable for nuclear fusion, by a new method in a short time. • Some of the Cu grains which were surrounded by W were about 50 nm. • The prepared W–Cu showed 15% higher bending strength than commercial W–Cu products. • The prepared W–Cu also showed a better plasticity than commercial W–Cu products. - Abstract: W–Cu functionally graded material (FGM) is prepared by a novel method of high-gravity combustion synthesis and melt-infiltration in a short time. In the W–Cu FGM, W grains are micron-sized and partially sintered to form an incomplete net structure, the Cu grains surrounded by W are about 50 nm, and lots of dislocations exist in the Cu phase. The W-rich layer shows both better strength and plasticity than the commercial W–Cu composite with a similar composition prepared by a conventional infiltration method

  3. Nonlinear dynamics of initially imperfect functionally graded circular cylindrical shell under complex loads

    Science.gov (United States)

    Liu, Y. Z.; Hao, Y. X.; Zhang, W.; Chen, J.; Li, S. B.

    2015-07-01

    The nonlinear vibration of a simply supported FGM cylindrical shell with small initial geometric imperfection under complex loads is studied. The effects of radial harmonic excitation, compressive in-plane force combined with supersonic aerodynamic and thermal loads are considered. The small initial geometric imperfection of the cylindrical shell is characterized in the form of the sine-type trigonometric functions. The effective material properties of this FGM cylindrical shell are graded in the radial direction according to a simple power law in terms of the volume fractions. Based on Reddy's third-order shear deformation theory, von Karman-type nonlinear kinematics and Hamilton's principle, the nonlinear partial differential equation that controls the shell dynamics is derived. Both axial symmetric and driven modes of the cylindrical shell deflection pattern are included. Furthermore, the equations of motion can be reduced into a set of coupled nonlinear ordinary differential equations by applying Galerkin's method. In the study of the nonlinear dynamics responses of small initial geometric imperfect FGM cylindrical shell under complex loads, the 4th order Runge-Kutta method is used to obtain time history, phase portraits, bifurcation diagrams and Poincare maps with different parameters. The effects of external loads, geometric imperfections and volume fractions on the nonlinear dynamics of the system are discussed.

  4. Probabilistic Fracture Analysis of Functionally Graded Materials--Part II: Implementation and Numerical Examples

    International Nuclear Information System (INIS)

    Probabilistic fracture analyses are performed for investigating uncertain fracture response of Functionally Graded Material (FGM) structures. The First-Order-Reliability-Method (FORM) is implemented into an existing Finite Element code for FGM (FE-FGM), which was previously developed at the University of Illinois at Urbana-Champaign. The computational simulation will be used in order to estimate the probability of crack initiation with uncertainties in the material properties only. The two-step probability analysis method proposed in the companion paper is illustrated by a numerical example of a composite strip with an edge crack. First, the reliability index of a crack initiation event is estimated as we vary the mean and standard deviation of the slope and the location of the inflection point of the spatial profile of Young's modulus. Secondly, the reliability index is estimated as we vary the standard deviation and the correlation length of the random field that characterize the random spatial fluctuation of Young's modulus. Also investigated is the relative importance of the uncertainties in the toughness compared to those in Young's modulus

  5. 3D-FE analysis of functionally graded structured dental posts.

    Science.gov (United States)

    Abu Kasim, Noor H; Madfa, Ahmed A; Hamdi, Mohd; Rahbari, Ghahnavyeh R

    2011-01-01

    This study aimed to compare the biomechanical behaviour of functionally graded structured posts (FGSPs) and homogenous-type posts in simulated models of a maxillary central incisor. Two models of FGSPs consisting of a multilayer xTi-yHA composite design, where zirconia and alumina was added as the first layer for models A and B respectively were compared to homogenous zirconia post (model C) and a titanium post (model D). The amount of Ti and HA in the FGSP models was varied in gradations. 3D-FEA was performed on all models and stress distributions were investigated along the dental post. In addition, interface stresses between the posts and their surrounding structures were investigated under vertical, oblique, and horizontal loadings. Strain distribution along the post-dentine interface was also investigated. The results showed that FGSPs models, A and B demonstrated better stress distribution than models C and D, indicating that dental posts with multilayered structure dissipate localized and interfacial stress and strain more efficiently than homogenous-type posts. PMID:22123011

  6. Nonlocal thermo-mechanical vibration analysis of functionally graded nanobeams in thermal environment

    Science.gov (United States)

    Ebrahimi, Farzad; Salari, Erfan

    2015-08-01

    In this paper, the thermal effect on free vibration characteristics of functionally graded (FG) size-dependent nanobeams subjected to various types of thermal loading is investigated by presenting a Navier type solution and employing a semi analytical differential transform method (DTM) for the first time. Two kinds of thermal loading, namely, linear temperature rise and nonlinear temperature rise are studied. Material properties of FG nanobeam are supposed to vary continuously along the thickness according to the power-law form and the material properties are assumed to be temperature-dependent. The small scale effect is taken into consideration based on nonlocal elasticity theory of Eringen. The nonlocal equations of motion are derived through Hamilton's principle and they are solved applying DTM. According to the numerical results, it is revealed that the proposed modeling and semi analytical approach can provide accurate frequency results of the FG nanobeams as compared to analytical results and also some cases in the literature. The detailed mathematical derivations are presented and numerical investigations are performed while the emphasis is placed on investigating the effect of the several parameters such as thermal effect, material distribution profile, small scale effects, mode number and boundary conditions on the normalized natural frequencies of the temperature-dependent FG nanobeams in detail. It is explicitly shown that the vibration behaviour of a FG nanobeams is significantly influenced by these effects. Numerical results are presented to serve as benchmarks for future analyses of FG nanobeams.

  7. Comparison of Various Functionally Graded Femoral Prostheses by Finite Element Analysis

    Directory of Open Access Journals (Sweden)

    Azim Ataollahi Oshkour

    2014-01-01

    Full Text Available This study is focused on finite element analysis of a model comprising femur into which a femoral component of a total hip replacement was implanted. The considered prosthesis is fabricated from a functionally graded material (FGM comprising a layer of a titanium alloy bonded to a layer of hydroxyapatite. The elastic modulus of the FGM was adjusted in the radial, longitudinal, and longitudinal-radial directions by altering the volume fraction gradient exponent. Four cases were studied, involving two different methods of anchoring the prosthesis to the spongy bone and two cases of applied loading. The results revealed that the FG prostheses provoked more SED to the bone. The FG prostheses carried less stress, while more stress was induced to the bone and cement. Meanwhile, less shear interface stress was stimulated to the prosthesis-bone interface in the noncemented FG prostheses. The cement-bone interface carried more stress compared to the prosthesis-cement interface. Stair climbing induced more harmful effects to the implanted femur components compared to the normal walking by causing more stress. Therefore, stress shielding, developed stresses, and interface stresses in the THR components could be adjusted through the controlling stiffness of the FG prosthesis by managing volume fraction gradient exponent.

  8. Biodegradability of poly (L-lactic acid) functionally graded materials with hardness gradient

    International Nuclear Information System (INIS)

    The aim of this study is to develop a functionally graded material (FGM) of biodegradable poly (L-lactic acid) (PLLA) with a hardness gradient. For this purpose, the PLLA was extruded at elevated temperatures to introduce molecular orientation. Two types of extrusion, direct extrusion and equal channel angular (ECA) extrusion, were carried out. Heat treatment without extrusion was also carried out at 50degC, 60degC and 70degC. For the mechanical property characterization, the hardness distributions were investigated using a Vickers microhardness tester. Biodegradability of PLLA FGM was measured by evaluating the mass decreasing ratio after incubation in a physiological saline solution at 37degC. It was found that the PLLA FGMs with symmetric and asymmetric hardness gradients could be fabricated by direct extrusion and ECA extrusion at elevated temperature, respectively. Although in the initial state the mass of PLLA gradually increased with the softening of the FGM, it started to decrease after two weeks. (author)

  9. Forced vibration analysis of functionally graded carbon nanotube-reinforced composite plates using a numerical strategy

    Science.gov (United States)

    Ansari, R.; Hasrati, E.; Faghih Shojaei, M.; Gholami, R.; Shahabodini, A.

    2015-05-01

    In this paper, the nonlinear forced vibration behavior of composite plates reinforced by carbon nanotubes is investigated by a numerical approach. The reinforcement is considered to be functionally graded (FG) in the thickness direction according to a micromechanical model. The first-order shear deformation theory and von Kármán-type kinematic relations are employed. The governing equations and the corresponding boundary conditions are derived with the use of Hamilton's principle. The generalized differential quadrature (GDQ) method is utilized to achieve a discretized set of nonlinear governing equations. A Galerkin-based scheme is then applied to obtain a time-varying set of ordinary differential equations of Duffing-type. Subsequently, a time periodic discretization is done and the frequency response of plates is determined via the pseudo-arc length continuation method. Selected numerical results are given for the effects of different parameters on the nonlinear forced vibration characteristics of uniformly distributed carbon nanotube- and FG carbon nanotube-reinforced composite plates. It is found that with the increase of CNT volume fraction, the flexural stiffness of plate increases; and hence its natural frequency gets larger. Moreover, it is observed that the distribution type of CNTs significantly affects the vibrational behavior of plate. The results also show that when the mid-plane of plate is CNT-rich, the natural frequency takes its minimum value and the hardening-type response of plate is intensified.

  10. Enhanced thermal stability of functionally graded sandwich cylindrical shells by shape memory alloys

    Science.gov (United States)

    Asadi, H.; Akbarzadeh, A. H.; Chen, Z. T.; Aghdam, M. M.

    2015-04-01

    The present paper deals with the nonlinear thermal instability of geometrically imperfect sandwich cylindrical shells under uniform heating. The sandwich shells are made of a shape memory alloy (SMA)-fiber-reinforced composite and functionally graded (FG) face sheets (FG/SMA/FG). The Brinson phenomenological model is used to express the constitutive characteristics of SMA fibers. The governing equations are established within the framework of the third-order shear deformation shell theory by taking into account the von Karman geometrical nonlinearity and initial imperfection. The material properties of constituents are assumed to be temperature dependent. The Galerkin technique is utilized to derive expressions of the bifurcation points and bifurcation paths of the sandwich cylindrical shells. Using the developed closed-form solutions, extensive numerical results are presented to provide an insight into the influence of the SMA fiber volume fraction, SMA pre-strain, core thickness, non-homogeneity index, geometrical imperfection, geometry parameters of sandwich shells and temperature dependency of materials on the stability of shells. The results reveal that proper application of SMA fibers postpones the thermal bifurcation point and dramatically decreases thermal post-buckling deflection. Moreover, the induced tensile recovery stress of SMA fibers could also stabilize the geometrically imperfect shells during the inverse martensite phase transformation.

  11. Free vibration of functionally graded carbon-nanotube-reinforced composite plates with cutout.

    Science.gov (United States)

    Mirzaei, Mostafa; Kiani, Yaser

    2016-01-01

    During the past five years, it has been shown that carbon nanotubes act as an exceptional reinforcement for composites. For this reason, a large number of investigations have been devoted to analysis of fundamental, structural behavior of solid structures made of carbon-nanotube-reinforced composites (CNTRC). The present research, as an extension of the available works on the vibration analysis of CNTRC structures, examines the free vibration characteristics of plates containing a cutout that are reinforced with uniform or nonuniform distribution of carbon nanotubes. The first-order shear deformation plate theory is used to estimate the kinematics of the plate. The solution method is based on the Ritz method with Chebyshev basis polynomials. Such a solution method is suitable for arbitrary in-plane and out-of-plane boundary conditions of the plate. It is shown that through a functionally graded distribution of carbon nanotubes across the thickness of the plate, the fundamental frequency of a rectangular plate with or without a cutout may be enhanced. Furthermore, the frequencies are highly dependent on the volume fraction of carbon nanotubes and may be increased upon using more carbon nanotubes as reinforcement. PMID:27335742

  12. Rigorous buckling analysis of size-dependent functionally graded cylindrical nanoshells

    Science.gov (United States)

    Sun, Jiabin; Lim, C. W.; Zhou, Zhenhuan; Xu, Xinsheng; Sun, Wei

    2016-06-01

    This paper presents new analytical solutions for buckling of carbon nanotubes (CNTs) and functionally graded (FG) cylindrical nanoshells subjected to compressive and thermal loads. The model applies Eringen's nonlocal differential constitutive relation to describe the size-dependence of nanoshells. Based on Reddy's higher-order shear deformation theory, governing equations are established and solved by separating the variables. The analysis first re-examines the classical buckling of single-walled CNTs. Accurate solutions are established, and it is found that the buckling stress decreases drastically when the nonlocal parameter reaches a certain value. For CNTs with constant wall-thickness, the buckling stress eventually decreases with enhanced size effect. By comparing with CNTs molecular dynamic simulations, the obtained nonlocal parameters are much smaller than those proposed previously. Subsequently, FG cylindrical nanoshells are analyzed, and it is concluded that similar behavior that has been observed for CNTs is also valid for FG cylindrical nanoshells. The paper further discusses in detail the effects of different geometric parameters, material distribution, and temperature field.

  13. Comparative analysis of steady state heat transfer in a TBC and functionally graded air cooled gas turbine blade

    Indian Academy of Sciences (India)

    Nilanjan Coomar; Ravikiran Kadoli

    2010-02-01

    Internal cooling passages and thermal barrier coatings (TBCs) are presently used to control metal temperatures in gas turbine blades. Functionally graded materials (FGMs), which are typically mixtures of ceramic and metal, have been proposed for use in turbine blades because they possess smooth property gradients thereby rendering them more durable under thermal loads. In the present work, a functionally graded model of an air-cooled turbine blade with airfoil geometry conforming to the NACA0012 is developed which is then used in a finite element algorithm to obtain a non-linear steady state solution to the heat equation for the blade under convection and radiation boundary conditions. The effects of external gas temperature, coolant temperature, surface emissivity changes and different average ceramic/metal content of the blade on the temperature distributions are examined. Simulations are also carried out to compare cooling effectiveness of functionally graded blades with that of blades having TBC. The results highlight the effect of including radiation in the simulation and also indicate that external gas temperature influences the blade heat transfer more strongly. It is also seen that graded blades with about 70% ceramic content can deliver better cooling effectiveness than conventional blades with TBC.

  14. How preschool executive functioning predicts several aspects of math achievement in Grades 1 and 3: A longitudinal study.

    Science.gov (United States)

    Viterbori, Paola; Usai, M Carmen; Traverso, Laura; De Franchis, Valentina

    2015-12-01

    This longitudinal study analyzes whether selected components of executive function (EF) measured during the preschool period predict several indices of math achievement in primary school. Six EF measures were assessed in a sample of 5-year-old children (N = 175). The math achievement of the same children was then tested in Grades 1 and 3 using both a composite math score and three single indices of written calculation, arithmetical facts, and problem solving. Using previous results obtained from the same sample of children, a confirmatory factor analysis examining the latent EF structure in kindergarten indicated that a two-factor model provided the best fit for the data. In this model, inhibition and working memory (WM)-flexibility were separate dimensions. A full structural equation model was then used to test the hypothesis that math achievement (the composite math score and single math scores) in Grades 1 and 3 could be explained by the two EF components comprising the kindergarten model. The results indicate that the WM-flexibility component measured during the preschool period substantially predicts mathematical achievement, especially in Grade 3. The math composite scores were predicted by the WM-flexibility factor at both grade levels. In Grade 3, both problem solving and arithmetical facts were predicted by the WM-flexibility component. The results empirically support interventions that target EF as an important component of early childhood mathematics education. PMID:26218333

  15. Crack propagation in functionally graded materials and structures; Risswachstum in funktional gradierten Materialien und Strukturen

    Energy Technology Data Exchange (ETDEWEB)

    Schramm, Britta

    2014-07-01

    Components with graded fracture-mechanical properties show a fundamentally different crack propagation behaviour than do homogeneous, isotropic structures. This becomes especially evident in investigations on the influence of fracture-mechanical material grading on the stage of steady fatigue crack propagation and on crack propagation speed da/dN. Theoretical findings based on the so-called TSSR concept, which was developed as part of this dissertation, indicate that it can have either positive or negative effects on crack propagation behaviour, depending on various material characteristics and grading constellations. The dissertation reports on experiments for validating theoretical statements on the influence of different structural conditions on crack propagation behaviour. These statements were largely found to be correct. The study thus contributes to the prediction of crack propagation in fracture-mechanically graded components and structures subject to static or cyclical stress.

  16. Development of Functionally Graded Materials for Manufacturing Tools and Dies and Industrial Processing Equipment

    Energy Technology Data Exchange (ETDEWEB)

    Lherbier, Louis, W.; Novotnak, David, J.; Herling, Darrell, R.; Sears, James, W.

    2009-03-23

    Hot forming processes such as forging, die casting and glass forming require tooling that is subjected to high temperatures during the manufacturing of components. Current tooling is adversely affected by prolonged exposure at high temperatures. Initial studies were conducted to determine the root cause of tool failures in a number of applications. Results show that tool failures vary and depend on the operating environment under which they are used. Major root cause failures include (1) thermal softening, (2) fatigue and (3) tool erosion, all of which are affected by process boundary conditions such as lubrication, cooling, process speed, etc. While thermal management is a key to addressing tooling failures, it was clear that new tooling materials with superior high temperature strength could provide improved manufacturing efficiencies. These efficiencies are based on the use of functionally graded materials (FGM), a new subset of hybrid tools with customizable properties that can be fabricated using advanced powder metallurgy manufacturing technologies. Modeling studies of the various hot forming processes helped identify the effect of key variables such as stress, temperature and cooling rate and aid in the selection of tooling materials for specific applications. To address the problem of high temperature strength, several advanced powder metallurgy nickel and cobalt based alloys were selected for evaluation. These materials were manufactured into tooling using two relatively new consolidation processes. One process involved laser powder deposition (LPD) and the second involved a solid state dynamic powder consolidation (SSDPC) process. These processes made possible functionally graded materials (FGM) that resulted in shaped tooling that was monolithic, bi-metallic or substrate coated. Manufacturing of tooling with these processes was determined to be robust and consistent for a variety of materials. Prototype and production testing of FGM tooling showed the

  17. Formation Behavior of Continuous Graded Composition in Ti-ZrO2 Functionally Graded Materials Fabricated by Mixed-Powder Pouring Method

    Directory of Open Access Journals (Sweden)

    Murali Jayachandran

    2013-01-01

    Full Text Available A mixed-powder pouring method has been proposed to fabricate functionally graded materials (FGMs with the desired compositional gradient. The experimental procedure involves preparation of mixed powders consisting of more than two types of particles with different size and/or density, which exhibit different velocities in suspension and sedimentation to form the green body under gravity conditions. The green body was sintered by a spark plasma sintering (SPS method. The initiation of the particle settlement was precisely controlled by using crushed ice as the suspension medium. Ti-ZrO2 FGMs were fabricated, in this study, using different sizes of ZrO2 and Ti particles. Vickers hardness confirmed the compositional gradient in the fabricated FGMs. A numerical simulation was also carried out to analyze the particle movement inside the suspension medium during the formation process and predict compositional gradient in the FGMs.

  18. Synthesis and microwave absorbing characteristics of functionally graded carbonyl iron/polyurethane composites

    Directory of Open Access Journals (Sweden)

    R. B. Yang

    2016-05-01

    Full Text Available Radar absorbing materials (RAMs also known as microwave absorbers, which can absorb and dissipate incident electromagnetic wave, are widely used in the fields of radar-cross section reduction, electromagnetic interference (EMI reduction and human health protection. In this study, the synthesis of functionally graded material (FGM (CI/Polyurethane composites, which is fabricated with semi-sequentially varied composition along the thickness, is implemented with a genetic algorithm (GA to optimize the microwave absorption efficiency and bandwidth of FGM. For impedance matching and broad-band design, the original 8-layered FGM was obtained by the GA method to calculate the thickness of each layer for a sequential stacking of FGM from 20, 30, 40, 50, 60, 65, 70 and 75 wt% of CI fillers. The reflection loss of the original 8-layered FGM below –10 dB can be obtained in the frequency range of 5.12∼18 GHz with a total thickness of 9.66 mm. Further optimization reduces the number of the layers and the stacking sequence of the optimized 4-layered FGM is 20, 30, 65, 75 wt% with thickness of 0.8, 1.6, 0.6 and 1.0 mm, respectively. The synthesis and measurement of the optimized 4-layered FGM with a thickness of 4 mm reveal a minimum reflection loss of –25.2 dB at 6.64 GHz and its bandwidth below – 10 dB is larger than 12.8 GHz.

  19. Fast plasma sintering delivers functional graded materials components with macroporous structures and osseointegration properties.

    Science.gov (United States)

    Godoy, R F; Coathup, M J; Blunn, G W; Alves, A L; Robotti, P; Goodship, A E

    2016-01-01

    We explored the osseointegration potential of two macroporous titanium surfaces obtained using fast plasma sintering (FPS): Ti macroporous structures with 400-600 µmØ pores (TiMac400) and 850-1000 µmØ pores (TiMac850). They were compared against two surfaces currently in clinical use: Ti-Growth® and air plasma spray (Ti-Y367). Each surface was tested, once placed over a Ti-alloy and once onto a CoCr bulk substrate. Implants were placed in medial femoral condyles in 24 sheep. Samples were explanted at four and eight weeks after surgery. Push-out loads were measured using a material-testing system. Bone contact and ingrowth were assessed by histomorphometry and SEM and EDX analyses. Histology showed early osseointegration for all the surfaces tested. At 8 weeks, TiMac400, TiMac850 and Ti-Growth® showed deep bone ingrowth and extended colonisation with newly formed bone. The mechanical push-out force was equal in all tested surfaces. Plasma spray surfaces showed greater bone-implant contact and higher level of pores colonisation with new bone than FPS produced surfaces. However, the void pore area in FPS specimens was significantly higher, yet the FPS porous surfaces allowed a deeper osseointegration of bone to implant. FPS manufactured specimens showed similar osseointegration potential to the plasma spray surfaces for orthopaedic implants. FPS is a useful technology for manufacturing macroporous titanium surfaces. Furthermore, its capability to combine two implantable materials, using bulk CoCr with macroporous titanium surfaces, could be of interest as it enables designers to conceive and manufacture innovative components. FPS delivers functional graded materials components with macroporous structures optimised for osseointegration. PMID:27071735

  20. Two-dimensional thermoelastic analysis of a functionally graded cylinder for different functionalities by using the higher-order shear deformation theory

    Science.gov (United States)

    Arefi, M.

    2015-05-01

    The present paper addresses application of the general shear deformation theory for the thermoelastic analysis of a functionally graded cylindrical shell subjected to inner and outer loads. The shear deformation theory and the energy method are employed for this purpose. This method presents the final relations by using a set of second-order differential equations in terms of the integral of material properties over the shell thickness. The obtained formulation can be solved for two well-known functionalities.

  1. The Development and Production of a Functionally Graded Composite for Pb-Bi Service

    Energy Technology Data Exchange (ETDEWEB)

    Ballinger, Ronald G

    2011-08-01

    A material that resists lead-bismuth eutectic (LBE) attack and retains its strength at 700°C would be an enabling technology for LBE-cooled reactors. No single alloy currently exists that can economically meet the required performance criteria of high strength and corrosion resistance. A Functionally Graded Composite (FGC) was developed with layers engineered to perform these functions. F91 was chosen as the structural layer of the composite for its strength and radiation resistance. Fe-12Cr-2Si, an alloy developed from previous work in the Fe-Cr-Si system, was chosen as the corrosion-resistant cladding layer because of its chemical similarity to F91 and its superior corrosion resistance in both oxidizing and reducing environments. Fe-12Cr-2Si experienced minimal corrosion due to its self-passivation in oxidizing and reducing environments. Extrapolated corrosion rates are below one micron per year at 700ï°C. Corrosion of F91 was faster, but predictable and manageable. Diffusion studies showed that 17 microns of the cladding layer will be diffusionally diluted during the three year life of fuel cladding. 33 microns must be accounted for during the sixty year life of coolant piping. 5 cm coolant piping and 6.35 mm fuel cladding preforms were produced on a commercial scale by weld-overlaying Fe-12Cr-2Si onto F91 billets and co-extruding them. An ASME certified weld was performed followed by the prescribed quench-and-tempering heat treatment for F91. A minimal heat affected zone was observed, demonstrating field weldability. Finally, corrosion tests were performed on the fabricated FGC at 700ï°C after completely breaching the cladding in a small area to induce galvanic corrosion at the interface. None was observed. This FGC has significant impacts on LBE reactor design. The increases in outlet temperature and coolant velocity allow a large increase in power density, leading to either a smaller core for the same power rating or more power output for the same size

  2. Clinical significance of a proposed lymphoscintigrpahic functional grade system in patients with extremity lymphedema of stage i

    International Nuclear Information System (INIS)

    We proposed a new lymphoscintigrpahic functional grade (LGr) system in extremity lymphedema, and investigated the association between the LGr and a long-term response to physical therapy in patients with extremity lymphedema of stage I. The subjects were 20 patients with unilateral extremity lymphedema of stage I, who underwent pre-treatment extremity lymphoscintigraphy using Tc-99m antimony sulfur colloid, and were treated by complex decongestive physical therapy (CDPT). A proposed lymphoscintigrpahic functional grade system consisted of LGr 0 to LGr 4 according to the ilioinguinal nodal uptake, amount of dermal backflow, and uptake pattern of main and collateral lymphatics : LGr 0 = normal, LGr 1 = decreased lymphatic function without dermal backflow, LGr 2 = decreased lymphatic function with dermal backflow, LGr 3 = non - visualization of main lymphatics with dermal backflow, and LGr 4 = no significant lymphatic transport from injection site. LGr 2 was divided into 2A and 2B based on the amount of dermal backflow. A physician who is a lymphedema specialist determined the long-term outcome to CDPT with normalized response (NR), good response (GR) and poor response (PR) based on the change of edema volume reduction, skin status and occurrence of dermatolymphangioadenitis after the clinical follow-up for more than 1 year. Therapeutic responses were NR in 2 patients. GR in 9 patients and PR in 9 patients. Baseline LGrs were 1 in 7 patients, 2A in 4 patients, 2B in 5 patients, 3 in 2 patients, and 4 in 2 patients. There was a significant relationship between therapeutic response and LGr (p=0.003). In other words, 10 of 11 patients (91%) with LGr 1 or 2A showed NR. or GR. On the contrary, 8 of 9 patients (89%) with LGr 2B, 3 or 4 showed PR. Patients with unilateral extremity lymphedema of stage I had different lymphoscintigrpahic functional grades. This grade system may be useful to predict the response to physical therapy in such patients

  3. Clinical significance of a proposed lymphoscintigrpahic functional grade system in patients with extremity lymphedema of stage i

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Joan Young; Hwang, Ji Hye; Kim, Dong Ik; Cho, Young Seok; Lee, Su Jin; Choi, Yong; Choe, Yeam Seong; Lee, Kyung Han; Kim, Byung Tae [Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul (Korea, Republic of)

    2005-07-01

    We proposed a new lymphoscintigrpahic functional grade (LGr) system in extremity lymphedema, and investigated the association between the LGr and a long-term response to physical therapy in patients with extremity lymphedema of stage I. The subjects were 20 patients with unilateral extremity lymphedema of stage I, who underwent pre-treatment extremity lymphoscintigraphy using Tc-99m antimony sulfur colloid, and were treated by complex decongestive physical therapy (CDPT). A proposed lymphoscintigrpahic functional grade system consisted of LGr 0 to LGr 4 according to the ilioinguinal nodal uptake, amount of dermal backflow, and uptake pattern of main and collateral lymphatics : LGr 0 = normal, LGr 1 = decreased lymphatic function without dermal backflow, LGr 2 = decreased lymphatic function with dermal backflow, LGr 3 = non - visualization of main lymphatics with dermal backflow, and LGr 4 = no significant lymphatic transport from injection site. LGr 2 was divided into 2A and 2B based on the amount of dermal backflow. A physician who is a lymphedema specialist determined the long-term outcome to CDPT with normalized response (NR), good response (GR) and poor response (PR) based on the change of edema volume reduction, skin status and occurrence of dermatolymphangioadenitis after the clinical follow-up for more than 1 year. Therapeutic responses were NR in 2 patients. GR in 9 patients and PR in 9 patients. Baseline LGrs were 1 in 7 patients, 2A in 4 patients, 2B in 5 patients, 3 in 2 patients, and 4 in 2 patients. There was a significant relationship between therapeutic response and LGr (p=0.003). In other words, 10 of 11 patients (91%) with LGr 1 or 2A showed NR. or GR. On the contrary, 8 of 9 patients (89%) with LGr 2B, 3 or 4 showed PR. Patients with unilateral extremity lymphedema of stage I had different lymphoscintigrpahic functional grades. This grade system may be useful to predict the response to physical therapy in such patients.

  4. Characterization and selection of suitable grades of lactose as functional fillers for capsule filling: part 1.

    Science.gov (United States)

    Moolchandani, Vikas; Augsburger, Larry L; Gupta, Abhay; Khan, Mansoor; Langridge, John; Hoag, Stephen W

    2015-01-01

    The purpose of this work is to characterize thermal, physical and mechanical properties of different grades of lactose and better understand the relationships between these properties and capsule filling performance. Eight grades of commercially available lactose were evaluated: Pharmatose 110 M, 125 M, 150 M, 200 M, 350 M (α-lactose monohydrate), AL (anhydrous lactose containing ∼80% β-AL), DCL11 (spray dried α-lactose monohydrate containing ∼15% amorphous lactose) and DCL15 (granulated α-lactose monohydrate containing ∼12% β-AL). In this study, different lactose grades were characterized by thermal, solid state, physical and mechanical properties and later evaluated using principal component analysis (PCA) to assess the inter-relationships among some of these properties. The lactose grades were characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD), moisture sorption/desorption isotherms, particle size distribution; the flow was characterized by Carr Index (CI), critical orifice diameter (COD) and angle of friction. Plug mechanical strength was estimated from its diametric crushing strength. The first and second principal components (PC) captured 47.6% and 27.4% of variation in the physical and mechanical property data, respectively. The PCA plot grouped together 110 M, AL, DCL11 and DCL15 on the one side of plot which possessed superior properties for capsule formulation and these grades were selected for future formulation development studies (part II of this work). PMID:25212639

  5. Control of sound and vibration for cylindrical shells by utilizing a periodic structure of functionally graded material

    International Nuclear Information System (INIS)

    A periodic shell made of functionally graded material (FGM) is proposed in this Letter. Wave propagation and vibration transmission in the FGM periodic shell for different circumferential modes are investigated. By illustrating the dynamical behavior of the periodic FGM shell within the pass/stop band frequency ranges, the mechanism of wave propagation and vibration transmission in the shell are illuminated. Moreover, the suppression characteristics of structure-borne sound in the internal field of the shell, either within the stop or pass band frequency ranges, are studied. -- Highlights: ► Construction of a periodic shell used functionally graded material periodically. ► Investigation of wave propagation and vibration transmission. ► Dynamical behaviors and formation mechanism of band gap. ► Characteristics of acoustic pressure distribution.

  6. Control of sound and vibration for cylindrical shells by utilizing a periodic structure of functionally graded material

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Huijie; Wen, Jihong [Key Laboratory of Science and Technology on Integrated Logistics Support, National University of Defense Technology, Changsha 410073 (China); Païdoussis, Michael P. [Department of Mechanical Engineering, McGill University, Montreal, Québec, H3A OC3 (Canada); Yu, Dianlong [Key Laboratory of Science and Technology on Integrated Logistics Support, National University of Defense Technology, Changsha 410073 (China); Asgari, Meisam [Department of Mechanical Engineering, McGill University, Montreal, Québec, H3A OC3 (Canada); Wen, Xisen, E-mail: wenxs@vip.sina.com [Key Laboratory of Science and Technology on Integrated Logistics Support, National University of Defense Technology, Changsha 410073 (China)

    2012-10-01

    A periodic shell made of functionally graded material (FGM) is proposed in this Letter. Wave propagation and vibration transmission in the FGM periodic shell for different circumferential modes are investigated. By illustrating the dynamical behavior of the periodic FGM shell within the pass/stop band frequency ranges, the mechanism of wave propagation and vibration transmission in the shell are illuminated. Moreover, the suppression characteristics of structure-borne sound in the internal field of the shell, either within the stop or pass band frequency ranges, are studied. -- Highlights: ► Construction of a periodic shell used functionally graded material periodically. ► Investigation of wave propagation and vibration transmission. ► Dynamical behaviors and formation mechanism of band gap. ► Characteristics of acoustic pressure distribution.

  7. "A New Class od Functionally Graded Cearamic-Metal Composites for Next Generation Very High Temperature Reactors"

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Mohit Jain; Dr. Ganesh Skandan; Dr. Gordon E. Khose; Mrs. Judith Maro, Nuclear Reactor Laboratory, MIT

    2008-05-01

    Generation IV Very High Temperature power generating nuclear reactors will operate at temperatures greater than 900 oC. At these temperatures, the components operating in these reactors need to be fabricated from materials with excellent thermo-mechanical properties. Conventional pure or composite materials have fallen short in delivering the desired performance. New materials, or conventional materials with new microstructures, and associated processing technologies are needed to meet these materials challenges. Using the concept of functionally graded materials, we have fabricated a composite material which has taken advantages of the mechanical and thermal properties of ceramic and metals. Functionally-graded composite samples with various microstructures were fabricated. It was demonstrated that the composition and spatial variation in the composition of the composite can be controlled. Some of the samples were tested for irradiation resistance to neutrons. The samples did not degrade during initial neutron irradiation testing.

  8. Microstructure and kinetics of a functionally graded NiTi-TiC x composite produced by combustion synthesis

    International Nuclear Information System (INIS)

    Production of a NiTi-TiC x functionally graded material (FGM) composite is possible through use of a combustion synthesis (CS) reaction employing the propagating mode (SHS). The NiTi-TiC x FGM combines the well-known and understood superelastic and shape memory capabilities of NiTi with the high hardness, wear and corrosion resistance of TiC x. The material layers were observed as functionally graded both in composition and porosity with distinct interfaces, while still maintaining good material interaction and bonding. XRD of the FGM composite revealed the presence of TiC x with equi-atomic NiTi and minor NiTi2 and NiTi3 phases. The TiC x particle size decreased with increasing NiTi content. Microindentation performed across the length of the FGM revealed a decrease in hardness as the NiTi content increased

  9. X-ray tomographic imaging of Al/SiCp functionally graded composites fabricated by centrifugal casting

    International Nuclear Information System (INIS)

    The present work refers to an X-ray microtomography experiment aiming at the elucidation of some aspects regarding particle distribution in SiC-particle-reinforced functionally graded aluminium composites. Precursor composites were produced by rheocasting. These were then molten and centrifugally cast to obtain the functionally graded composites. From these, cylindrical samples, around 1 mm in diameter, were extracted, which were then irradiated with a X-ray beam produced at the European Synchrotron Radiation Facility. The 3-D images were obtained in edge-detection mode. A segmentation procedure has been adapted in order to separate the pores and SiC particles from the Al matrix. Preliminary results on the particle and pore distributions are presented

  10. A New Class of Functionally Graded Cearamic-Metal Composites for Next Generation Very High Temperature Reactors

    International Nuclear Information System (INIS)

    Generation IV Very High Temperature power generating nuclear reactors will operate at temperatures greater than 900 C. At these temperatures, the components operating in these reactors need to be fabricated from materials with excellent thermo-mechanical properties. Conventional pure or composite materials have fallen short in delivering the desired performance. New materials, or conventional materials with new microstructures, and associated processing technologies are needed to meet these materials challenges. Using the concept of functionally graded materials, we have fabricated a composite material which has taken advantages of the mechanical and thermal properties of ceramic and metals. Functionally-graded composite samples with various microstructures were fabricated. It was demonstrated that the composition and spatial variation in the composition of the composite can be controlled. Some of the samples were tested for irradiation resistance to neutrons. The samples did not degrade during initial neutron irradiation testing.

  11. A parametric study on the buckling of functionally graded material plates with internal discontinuities using the partition of unity method

    OpenAIRE

    S Natarajan; Chakraborty, S.; M. Ganapathi; Subramaniam, M

    2013-01-01

    In this paper, the effect of local defects, viz., cracks and cutouts on the buckling behaviour of functionally graded material plates subjected to mechanical and thermal load is numerically studied. The internal discontinuities, viz., cracks and cutouts are represented independent of the mesh within the framework of the extended finite element method and an enriched shear flexible 4-noded quadrilateral element is used for the spatial discretization. The properties are assumed to vary only in ...

  12. Micromechanical Simulation of Thermal Cyclic Behavior of ZrO2/Ti Functionally Graded Thermal Barrier Coatings

    OpenAIRE

    Hideaki Tsukamoto

    2015-01-01

    This study numerically investigates cyclic thermal shock behavior of ZrO2/Ti functionally graded thermal barrier coatings (FG TBCs) based on a nonlinear mean-field micromechanical approach, which takes into account the time-independent and dependent inelastic deformation, such as plasticity of metals, creep of metals and ceramics, and diffusional mass flow at the ceramic/metal interface. The fabrication processes for the FG TBCs have been also considered in the simulation. The effect of creep...

  13. Application of X-ray microtomography to the microstructural characterization of Al-based functionally graded materials

    OpenAIRE

    Velhinho, A.; Fernandes, F. M. Braz; Ferreira, S. C.; L. A. Rocha; Vignoles, G.; Cloetens, P.

    2006-01-01

    This paper provides a brief overview of the possibilities offered by X-ray computed microtomography, and particularly synchrotron radiation X-ray microtomography, regarding metal matrix composite characterization, emphasis being placed in the case of Al-based functionally graded materials. Examples are provided concerning the characterization of the reinforcement population, interfacial properties, in-situ transformation and damage evolution. The specific needs of the technique and limitation...

  14. A Novel Fabrication Method for Functionally Graded Materials under Centrifugal Force: The Centrifugal Mixed-Powder Method

    OpenAIRE

    Eri Miura-Fujiwara; Yoshifumi Inaguma; Hisashi Sato; Yoshimi Watanabe

    2009-01-01

    One of the fabrication methods for functionally graded materials (FGMs) is a centrifugal solid-particle method, which is an application of the centrifugal casting technique. However, it is the difficult to fabricate FGMs containing nano-particles by the centrifugal solid-particle method. Recently, we proposed a novel fabrication method, which we have named the centrifugal mixed-powder method, by which we can obtain FGMs containing nano-particles. Using this processing method, Cu-based FGMs co...

  15. Bending and free vibration of functionally graded beams using various higher-order shear deformation beam theories

    OpenAIRE

    Thai, Huu-Tai; Vo, Thuc

    2012-01-01

    In this paper, various higher-order shear deformation beam theories for bending and free vibration of functionally graded beams are developed. The developed theories account for higher-order variation of transverse shear strain through the depth of the beam, and satisfy the stress-free boundary conditions on the top and bottom surfaces of the beam. A shear correction factor, therefore, is not required. In addition, these theories have strong similarities with Euler–Bernoulli beam theory in so...

  16. Microstructure, properties and temperature evolution of electro-pulsing treated functionally graded Ti–6Al–4V alloy strip

    International Nuclear Information System (INIS)

    Highlights: • Functional graded titanium alloy is produced by electro-pulsing treatment. • Ductility of material is improved greatly to 27.8% by EPT. • Precipitation and re-dissolution of beta phase are both found in the EPT process. • FGM-EPT features consist of ultrafast process and low temperature. • Temperature evolution implies the coupling of thermal and a thermal effect. - Abstract: Microstructure, mechanical properties, electrical resistivity and temperature evolution of functionally graded Ti–6Al–4V alloy strips were processed under the electro-pulsing treatment (EPT) for 16 s and further studied by optical microscope, scanning electron microscopy, X-ray diffraction, electrical resistivity measurement, mechanical testing and consecutive temperature testing. Six kinds of microstructures were obtained on the single functional graded material (FGM) by different EPT parameters. The temperature evolution of each processing parameter was measured timely to be found low and different as a proof of the coupling of thermal and athermal effect in the FGM-EPT procedure. With increasing the frequency, the volume of beta phase increased gradually in general and re-dissolution both occurred. The ductility for sectional samples of FGM was enhanced to the maximum value, elongation to failure 27.8%, without compromising too much ultimate tensile strength and relevant tensile fracture behaviors were changed. The mechanism of microstructure change was discussed by the coupling of the thermal and athermal effect of EPT to decrease the thermodynamic barrier and influence the dislocations and atoms motion

  17. Microstructure, properties and temperature evolution of electro-pulsing treated functionally graded Ti–6Al–4V alloy strip

    Energy Technology Data Exchange (ETDEWEB)

    Ye, Xiaoxin; Kuang, Jie; Li, Xiaopei; Tang, Guoyi, E-mail: tanggy@mail.sz.tsinghua.edu.cn

    2014-06-25

    Highlights: • Functional graded titanium alloy is produced by electro-pulsing treatment. • Ductility of material is improved greatly to 27.8% by EPT. • Precipitation and re-dissolution of beta phase are both found in the EPT process. • FGM-EPT features consist of ultrafast process and low temperature. • Temperature evolution implies the coupling of thermal and a thermal effect. - Abstract: Microstructure, mechanical properties, electrical resistivity and temperature evolution of functionally graded Ti–6Al–4V alloy strips were processed under the electro-pulsing treatment (EPT) for 16 s and further studied by optical microscope, scanning electron microscopy, X-ray diffraction, electrical resistivity measurement, mechanical testing and consecutive temperature testing. Six kinds of microstructures were obtained on the single functional graded material (FGM) by different EPT parameters. The temperature evolution of each processing parameter was measured timely to be found low and different as a proof of the coupling of thermal and athermal effect in the FGM-EPT procedure. With increasing the frequency, the volume of beta phase increased gradually in general and re-dissolution both occurred. The ductility for sectional samples of FGM was enhanced to the maximum value, elongation to failure 27.8%, without compromising too much ultimate tensile strength and relevant tensile fracture behaviors were changed. The mechanism of microstructure change was discussed by the coupling of the thermal and athermal effect of EPT to decrease the thermodynamic barrier and influence the dislocations and atoms motion.

  18. Synthesis of functionally graded nano Al2O3–Ni composite coating by pulse electrodeposition

    International Nuclear Information System (INIS)

    The main goal of this research is the synthesis of functionally graded nickel–nano Al2O3 composite coatings by using pulse deposition in which the amount of the embedded nano alumina particles changes in the cross section of the composite. For producing functionally graded nanocomposite coatings by pulse electrodeposition under ultrasonic agitation, frequency and duty cycle changes can be applied and in this research, the influence of both parameters has been studied. Microstructure of these coatings investigated by SEM, EBSD and XRD methods. By changing the duty cycle from 90% to 10% at different frequency, the microstructure of the coatings did not change significantly. These coatings showed ductile structure with {0 0 1} texture at primary layers and small randomly oriented grains at final layers. The most important factor affecting the microstructure of the nickel matrix was the average current density and incorporation of nano alumina particles does not have significant effect on the microstructure. The optimum condition for production of functionally graded nano Al2O3–Ni coating was changing of the duty cycle from 90% to 10% at fixed frequency of 10 Hz.

  19. Finite Element Modeling and Free Vibration Analysis of Functionally Graded Nanocomposite Beams Reinforced by Randomly Oriented Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Benedict Thomas

    2013-12-01

    Full Text Available This article deals with the finite element modeling and free vibration analysis of functionally graded nanocomposite beams reinforced by randomly oriented straight single-walled carbon nanotubes (SWCNTs. Nanostructural materials can be used to alter mechanical, thermal and electrical properties of polymer-based composite materials, because of their superior properties and perfect atom arrangement. Timoshenko beam theory is used to evaluate dynamic characteristics of the beam. The Eshelby–Mori–Tanaka approach based on an equivalent fiber is used to investigate the material properties of the beam. The equations of motion are derived by using Hamilton’s principle. The finite element method is employed to discretize the model and obtain a numerical approximation of the motion equation. Different SWCNTs distributions in the thickness direction are introduced to improve fundamental natural frequency and dynamic behavior of uniform functionally graded nanocomposite beam. Results are presented in tabular and graphical forms to show the effects of various material distributions, carbon nanotube orientations, shear deformation, slenderness ratios and boundary conditions on the dynamic behavior of the beam. The first five normalized mode shapes for functionally graded carbon nanotube reinforced composite (FG-CNTRC beams with different boundary conditions and different carbon nanotubes (CNTs orientation are presented. The results show that the above mentioned effects play very important role on the dynamic behavior of the beam.

  20. Theoretical analysis on bending behavior of functionally graded composite beam crack-controlled by ultrahigh toughness cementitious composites

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Ultrahigh toughness cementitious composites (UHTCC) obviously show strain hardening property under tensile or bending loading. The failure pattern of the UHTCC components exhibits multiple fine cracks under uniaxial tensile loading with prominent tensile strain capacity in excess of 3%, with merely 60 μm average crack width even corresponding to the ultimate tensile strain state. The approach adopted is based on the concept of functionally-graded concrete, where part of the concrete, which surrounds the main longitudinal reinforcement in a RC (reinforced concrete) member, is strategically replaced with UHTCC with excellent crack-controlling ability. Investigations on bending behavior of functionally-graded composite beam crack controlled by UHTCC has been carried out, including theo- retical analysis, experimental research on long composite beams without web reinforcement, validation and comparison between experimental and theoretical results, and analysis on crack control. In addition to improving bearing capacity, the results indicate that functionally-graded composite beams using UHTCC has been found to be very effective in preventing corrosion-induced damage compared with RC beams. Therefore, durability and service life of the structure could be enhanced. This paper discusses the development of internal force and crack propagation during loading process, and presents analysis of the internal force in different stages, moment-curvature relationship from loading to damage and calculation of mid-span deflection and ductility index. In the end, the theoretical formulae have been validated by experimental results.

  1. Three-dimensional thermo-elastic analysis of a functionally graded cylindrical shell with piezoelectric layers by differential quadrature method

    Energy Technology Data Exchange (ETDEWEB)

    Alashti, R. Akbari, E-mail: raalashti@nit.ac.ir [Mechanical Engineering Department, Babol University of Technology, P.O. Box 484, Shariati Avenue, Babol (Iran, Islamic Republic of); Khorsand, M. [Mechanical Engineering Department, Babol University of Technology, P.O. Box 484, Shariati Avenue, Babol (Iran, Islamic Republic of)

    2011-05-15

    Three-dimensional thermo-elastic analysis of a functionally graded cylindrical shell with piezoelectric layers under the effect of asymmetric thermo-electro-mechanical loads is carried out. Numerical results of displacement, stress and thermal fields are obtained using two versions of the differential quadrature methods, namely polynomial and Fourier quadrature methods. Material properties of the shell are assumed to be graded in the radial direction according to a power law but the Poisson's ratio is assumed to be constant. Shells are considered to be under the effect of the pressure loading in the form of cosine and ring pressure loads, electric potentials and temperature fields. Numerical results for various boundary conditions are obtained and the effects of the thickness of piezoelectric layers, grading index of material properties and the ratio of the thickness to the radius of the shell on these results is presented. - Highlights: > A numerical study of an FGM cylindrical shell with piezoelectric layers is made. > Governing equations are solved by two versions of differential quadrature methods. > The effect of layers thickness, grading index and geometrical ratios is presented.

  2. Chronic low-grade inflammation, lipid risk factors and mortality in functionally dependent elderly

    Directory of Open Access Journals (Sweden)

    Vasović Olga

    2010-01-01

    Full Text Available Background/Aim. It has been proved that a highly sensitive C-reactive protein (hsCRP can be used as an established marker of chronic inflammation for cardiovascular risk assessment. Since mean values of both low-density cholesterol (LDL-C and high-density lipoprotein cholesterol (HDL-C decrease during aging, the knowledge that increased hsCRP concentration predicts mortality (Mt would influence therapy and treatment outcome. The aim of this study was to examine importance of chronic low grade inflammation and its association with lipid risk factors for all-cause Mt in functionally dependent elderly. Methods. The participants of this longitudinal prospective study were 257 functionally dependent elderly aged 65-99 years. Baseline measurements: anthropometric measurements, blood pressure, fasting plasma total cholesterol (TC, triglyceride (TG, HDL-C, LDL-C, non- HDL-C, hemoglobin A1c (HbA1c were recorded and different lipid ratios were calculated. Inflammation was assessed by the levels of white blood cells, fibrinogen and hsCRP. The participants with hsCRP grater than 10 mg/L were excluded from the study. The residual participants (77.4% women were divided into three groups according to their hsCRP levels: a low (< 1 mg/L, n = 70, average (1 to 3 mg/L, n = 69, and high (3-10 mg/L, n = 69 hsCRP group. Associations of all-cause Mt with different risk factors were examined using logistic regression analysis. Results. The hsCRP level showed a significant positive correlation with waist (r = 0.199, p = 0.004 and hip (r = 0.187, p = 0.007 circumferences, body mass index (r = 0.143, p = 0.040 and serum triglyceride level (r = 0.139, p = 0.045 and significant negative correlation with HDL-C (r = -0.164, p = 0.018. Ratios TC/HDL-C and TG/HDL-C were significantly smaller in the low hsCRP group compared to the average hsCRP group (p = 0.019, p = 0.045, respectively and without significant differences compared with the high hsCRP group. Two years after the

  3. Functional grading of metal foam cores for yield-limited lightweight sandwich beams

    International Nuclear Information System (INIS)

    We show that grading the porosity in a bent metal skin/metal foam core sandwich can generate significant weight savings in yield-limited design when, and only when, there is a gradient in the applied moment along the sandwich beam

  4. Asphalt Pavement Aging and Temperature Dependent Properties Using Functionally Graded Viscoelastic Model

    Science.gov (United States)

    Dave, Eshan V.

    2009-01-01

    Asphalt concrete pavements are inherently graded viscoelastic structures. Oxidative aging of asphalt binder and temperature cycling due to climatic conditions being the major cause of non-homogeneity. Current pavement analysis and simulation procedures dwell on the use of layered approach to account for these non-homogeneities. The conventional…

  5. Corrosion and wear behavior of functionally graded Al2024/SiC composites produced by hot pressing and consolidation

    International Nuclear Information System (INIS)

    Highlights: • Functionally graded Al2024/SiC composites were produced by hot pressing. • Effect of the number of graded layers was investigated on the corrosion behavior. • Functionally graded composites has the most corrosion resistant than composites. • Wear mechanisms of Al2024/SiC composites were explained. - Abstract: Functionally graded Al2024/SiC composites (FGMs) with varying percentage of SiC (30–60%) were produced by hot pressing and consolidation method. The effects of SiC content and number of layers of Al2024/SiC FGMs on the corrosion and wear behaviors were investigated. The microstructures of these composites were characterized by a scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS). The corrosion performances of composites were evaluated by potentiodynamic polarization scans in 3.5% NaCl solution. Corrosion experiments shows that corrosion rate (1109 mpy) of two layered FGMs which containing 50 wt.% SiC were much higher than Al2024 matrix (2569 mpy) and Al2024/50 wt.% SiC composite (2201 mpy). Mechanical properties of these composites were evaluated by microhardness measurements and ball-on-disk wear tests. As the applied load change from 15 to 20 N, the wear rates of the Al2024 increased significantly and wear mechanism transformed from mild to severe wear regime. It has been shown that Al2024/40 wt.% SiC composite has lower wear rate where adhesive and abrasive wear mechanisms play a major role

  6. Corrosion and wear behavior of functionally graded Al2024/SiC composites produced by hot pressing and consolidation

    Energy Technology Data Exchange (ETDEWEB)

    Erdemir, Fatih; Canakci, Aykut, E-mail: aykut@ktu.edu.tr; Varol, Temel; Ozkaya, Serdar

    2015-09-25

    Highlights: • Functionally graded Al2024/SiC composites were produced by hot pressing. • Effect of the number of graded layers was investigated on the corrosion behavior. • Functionally graded composites has the most corrosion resistant than composites. • Wear mechanisms of Al2024/SiC composites were explained. - Abstract: Functionally graded Al2024/SiC composites (FGMs) with varying percentage of SiC (30–60%) were produced by hot pressing and consolidation method. The effects of SiC content and number of layers of Al2024/SiC FGMs on the corrosion and wear behaviors were investigated. The microstructures of these composites were characterized by a scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS). The corrosion performances of composites were evaluated by potentiodynamic polarization scans in 3.5% NaCl solution. Corrosion experiments shows that corrosion rate (1109 mpy) of two layered FGMs which containing 50 wt.% SiC were much higher than Al2024 matrix (2569 mpy) and Al2024/50 wt.% SiC composite (2201 mpy). Mechanical properties of these composites were evaluated by microhardness measurements and ball-on-disk wear tests. As the applied load change from 15 to 20 N, the wear rates of the Al2024 increased significantly and wear mechanism transformed from mild to severe wear regime. It has been shown that Al2024/40 wt.% SiC composite has lower wear rate where adhesive and abrasive wear mechanisms play a major role.

  7. Fabrication of Fe-FeAl Functionally Graded Material Using the Wire-Arc Additive Manufacturing Process

    Science.gov (United States)

    Shen, Chen; Pan, Zengxi; Cuiuri, Dominic; Roberts, Jon; Li, Huijun

    2016-02-01

    A functionally gradient iron-aluminum wall structure with aluminum composition gradient from 0 at. pct to over 50 at. pct is fabricated using a wire-arc additive manufacturing (WAAM) system. The as-fabricated alloy is investigated using optical microstructure analysis, hardness testing, tensile testing, X-ray diffraction phase characterization, and electron-dispersive spectrometry. The comprehensive analysis of the experimental samples has shown that the WAAM system can be used for manufacturing iron aluminide functionally graded material with full density, desired composition, and reasonable mechanical properties.

  8. Characterization of W/Fe functionally graded materials manufactured by resistance sintering under ultra-high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Qu, Dandan [School of Materials Science and Engineering, University of Science and Technology Beijing, 100083 Beijing (China); Karlsruhe Institute of Technology, Institute for Applied Materials, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Zhou, Zhangjian, E-mail: zhouzhangjianustb@163.com [School of Materials Science and Engineering, University of Science and Technology Beijing, 100083 Beijing (China); Tan, Jun [School of Materials Science and Engineering, University of Science and Technology Beijing, 100083 Beijing (China); Aktaa, Jarir [Karlsruhe Institute of Technology, Institute for Applied Materials, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany)

    2015-02-15

    Highlights: • W/Fe functionally graded material (FGM) are fabricated well by resistance sintering under ultra-high pressure (RSUHP). • The whole sintering time is less than 3 min and cost-effective. • We research the W/Fe interface and the formation of intermetallic at the interface. In addition, we explain the possible method to avoid the formation of brittle intermetallic. • Vickers hardness of W/Fe FGM before and after heat treatment are investigated here. - Abstract: W/Fe-based components are considered as primary structural materials for the future fusion reactor. A five-layer W/Fe functional graded material (FGM) with W volume fraction of 0%, 25%, 50%, 75% and 100%, respectively, have been fabricated by a novel sintering method combining resistance sintering with ultra-high pressure. The sintering was carried out under pressures of 9 GPa and an input power of 11 kW for 60 s. The microstructure of cross-section observed by SEM shows a well-graded transition. The relative density of each layer is more than 97%. A brittle phase Fe{sub 7}W{sub 6} is formed at the interface of W particles and Fe particles, and this intermetallic phase coats Fe particles homogeneously with a thickness of 1–5 μm. It is possible to avoid the brittle phase by choosing appropriate particle size and sintering parameters. In addition, Vickers hardness of W/Fe FGM was investigated before and after heat treatment.

  9. Characterization of W/Fe functionally graded materials manufactured by resistance sintering under ultra-high pressure

    International Nuclear Information System (INIS)

    Highlights: • W/Fe functionally graded material (FGM) are fabricated well by resistance sintering under ultra-high pressure (RSUHP). • The whole sintering time is less than 3 min and cost-effective. • We research the W/Fe interface and the formation of intermetallic at the interface. In addition, we explain the possible method to avoid the formation of brittle intermetallic. • Vickers hardness of W/Fe FGM before and after heat treatment are investigated here. - Abstract: W/Fe-based components are considered as primary structural materials for the future fusion reactor. A five-layer W/Fe functional graded material (FGM) with W volume fraction of 0%, 25%, 50%, 75% and 100%, respectively, have been fabricated by a novel sintering method combining resistance sintering with ultra-high pressure. The sintering was carried out under pressures of 9 GPa and an input power of 11 kW for 60 s. The microstructure of cross-section observed by SEM shows a well-graded transition. The relative density of each layer is more than 97%. A brittle phase Fe7W6 is formed at the interface of W particles and Fe particles, and this intermetallic phase coats Fe particles homogeneously with a thickness of 1–5 μm. It is possible to avoid the brittle phase by choosing appropriate particle size and sintering parameters. In addition, Vickers hardness of W/Fe FGM was investigated before and after heat treatment

  10. Processing and Characterization of Functionally Graded Hydroxyapatite Coatings for Biomedical Implants

    Science.gov (United States)

    Bai, Xiao

    Hydroxyapatite [Ca10(PO4)6(OH) 2, HA] has been widely applied as a coating on various biomedical bone/dental implants to improve biocompatibility and bioactivity. It has been observed that primary reasons leading to implantation failure of commercial HA coated implants processed by plasma spraying are the poor mechanical properties of coatings and infections accompanied by implantation. It has been also reported an ideal coating should be able to stimulate new bone growth at the initial stage of implantation and stay stable both mechanically and chemically thereafter. This research has investigated a functionally graded hydroxyapatite (FGHA) coating that is capable of improving the stability of implants, facilitating recovery, and preventing infections after implantation. A series of FGHA coatings with incorporated Ag 0 ˜ 13.53 wt. % has been deposited onto Ti substrate using ion beam assisted deposition (IBAD) with in-situ heat treatment. The compositional, microstructural, mechanical, and biological properties of coatings have been analyzed via various tests. The relationship among processing parameters, coating properties and biological behaviors has been established and the processing parameters for processing FGHA coatings with/without incorporated Ag have been optimized. Microstructure observations of coating cross section via transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) for set temperature coatings deposited at 450°C ˜ 750°C reveals that in-situ substrate temperature is the primary factor controlling the crystallinity of the coatings. The microstructure observation of cross section via TEM/STEM for both FGHA coatings with/without incorporated Ag has shown that coatings are dense and have a gradually decreased crystallinity from substrate/coating interface to top surface. In particular, the interface has an atomically intermixed structure; the region near the interface has a columnar grain structure whereas

  11. Association of therapeutic occasion, gross motor function grading and developmental level with gross motor functional recovery in children with cerebral palsy

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    BACKGROUND: The abnormal posture and motor pattern have not stabilized in children with cerebral palsy at early period, thus timely treatment can establish normal postural reflex and motor pattern, and prevent complications of muscle contracture, ankylosis, skeletal deformity, etc. The clinical factors affecting the rehabilitative efficacy of gross motor function in children with cerebral palsy should be observed.OBJECTIVE: To observe the effects of therapeutic occasion, grading of gross motor function and developmental level on the rehabilitative efficacy in children with cerebral palsy.DESIGN: A case-controlled analysis.SETTING: Qilu Children's Hospital of Shandong University.PARTICIPANTS: Totally 138 children with cerebral palsy, who were hospitalized for 12 months in the Rehabilitation Center of Qilu Children's Hospital, Shandong University, were selected from April 2004 to September 2006, and all the children were diagnosed to be accorded with the standard set by the national seminar on cerebral palsy in 2004. There were 97 males and 41 females, including 55 cases of 0 - 2 years old,47 cases of 2 - 4 years and 36 cases of 4 - 6 years. Informed contents were obtained from relatives of all the children.METHODS: ① Comprehensive rehabilitation treatment: Vojta method was to induce the children to turn over the body and crawl by stimulating reflective turn over and crawling on belly. Bobath method including trainings of head control, turning over body, keeping sitting position, keeping balance, crawling, keeping standing position, and walking, etc.; The children were massaged by using the maneuvers of push, press, rub,pull, wave, etc. according to the sites and types of palsy. Acupuncture was performed mainly at bilateral motor areas, the needle was retained for 1 hour per time, 6 days continuously every week, and followed by a 1-day interval. ② Prognosis assessment: The gross motor functional grading of the children with cerebral palsy at admission was

  12. Functionally graded scaffolds for the engineering of interface tissues using hybrid twin screw extrusion/electrospinning technology

    Science.gov (United States)

    Erisken, Cevat

    Tissue engineering is the application of the principles of engineering and life sciences for the development of biological alternatives for improvement or regeneration of native tissues. Native tissues are complex structures with functions and properties changing spatially and temporally, and engineering of such structures requires functionally graded scaffolds with composition and properties changing systematically along various directions. Utilization of a new hybrid technology integrating the controlled feeding, compounding, dispersion, deaeration, and pressurization capabilities of extrusion process with electrospinning allows incorporation of liquids and solid particles/nanoparticles into polymeric fibers/nanofibers for fabrication of functionally graded non-woven meshes to be used as scaffolds in engineering of tissues. The capabilities of the hybrid technology were demonstrated with a series of scaffold fabrication and cell culturing studies along with characterization of biomechanical properties. In the first study, the hybrid technology was employed to generate concentration gradations of beta-tricalcium phosphate (beta-TCP) nanoparticles in a polycaprolactone (PCL) binder, between two surfaces of nanofibrous scaffolds. These scaffolds were seeded with pre-osteoblastic cell line (MC3T3-E1) to attempt to engineer cartilage-bone interface, and after four weeks, the tissue constructs revealed formation of continuous gradations in extracellular matrix akin to cartilage-bone interface in terms of distributions of mineral concentrations and biomechanical properties. In a second demonstration of the hybrid technology, graded differentiation of stem cells was attempted by using insulin, a known stimulator of chondrogenic differentiation, and beta-glycerol phosphate (beta-GP), for mineralization. Concentrations of insulin and beta-GP in PCL were controlled to monotonically increase and decrease, respectively, along the length of scaffolds, which were then seeded

  13. Free vibration analysis of a rotating hub-functionally graded material beam system with the dynamic stiffening effect

    Science.gov (United States)

    Li, L.; Zhang, D. G.; Zhu, W. D.

    2014-02-01

    A comprehensive dynamic model of a rotating hub-functionally graded material (FGM) beam system is developed based on a rigid-flexible coupled dynamics theory to study its free vibration characteristics. The rigid-flexible coupled dynamic equations of the system are derived using the method of assumed modes and Lagrange's equations of the second kind. The dynamic stiffening effect of the rotating hub-FGM beam system is captured by a second-order coupling term that represents longitudinal shrinking of the beam caused by the transverse displacement. The natural frequencies and mode shapes of the system with the chordwise bending and stretching (B-S) coupling effect are calculated and compared with those with the coupling effect neglected. When the B-S coupling effect is included, interesting frequency veering and mode shift phenomena are observed. A two-mode model is introduced to accurately predict the most obvious frequency veering behavior between two adjacent modes associated with a chordwise bending and a stretching mode. The critical veering angular velocities of the FGM beam that are analytically determined from the two-mode model are in excellent agreement with those from the comprehensive dynamic model. The effects of material inhomogeneity and graded properties of FGM beams on their dynamic characteristics are investigated. The comprehensive dynamic model developed here can be used in graded material design of FGM beams for achieving specified dynamic characteristics.

  14. 3D analysis of functionally graded material plates with complex shapes and various holes

    Institute of Scientific and Technical Information of China (English)

    Zhi-yuan CAO; Shou-gao TANG; Guo-hua CHENG

    2009-01-01

    In this paper, the basic formulae for the semi-analytical graded FEM on FGM members are derived. Since FGM parameters vary along three space coordinates, the parameters can be integrated in mechanical equations. Therefore with the parameters of a given FGM plate, problems of FGM plate under various conditions can be solved. The approach uses 1D discretization to obtain 3D solutions, which is proven to be an effective numerical method for the mechanical analyses of FGM structures. Examples of FGM plates with complex shapes and various holes are presented.

  15. Computational Micromechanics of Damage Initiation and Growth in Functionally Graded Composites

    DEFF Research Database (Denmark)

    Mishnaevsky, Leon; Gross, Dietmar

    2008-01-01

    composites with metal matrix and ceramic inclusions, a series of numerical mesomechanical experiments has been carried out. The tensile stress-strain curves, fraction of failed particles versus applied strain curves, and stress and damage distributions at different stages of loading were determined for...... different generic (artificially designed) graded microstructures and compared. It was shown that the flow stress and stiffness of composites increase and failure strain decreases with decreasing property gradient (i.e., when the particles become more localized in some material regions). The damage growth in...

  16. Effects of the DICOM grayscale standard display function on the accuracy of medical-grade grayscale and consumer-grade color displays for telemammography screening

    Science.gov (United States)

    Salazar, Antonio J.; Romero, Javier; Bernal, Oscar; Moreno, Angela; Velasco, Sofía.; Díaz, Xavier

    2013-11-01

    The aim of this study was to compare the diagnostic accuracy of the consumer-grade and medical-grade monitors —with very different costs— in breast cancer detection, when using with and without Digital Imaging and Communication in Medicine (DICOM) standard calibration. This was a retrospective study with factorial design and repeated measures, using 70 digital mammograms (40 benign or normal cases and 30 malignant cases), four radiologists, and three displays, with and without display calibration. Film mammograms were also included. Readings were classified according to the Breast Imaging Reporting and Data System. One medical-grade grayscale display and two consumer-grade displays were compared. Receiver operating characteristics curves were plotted for nodules, micro calcifications and the degree of malignancy. The diagnostic accuracy for each device was calculated as the area under these curves and accuracies were compared using analysis of variance.

  17. Piezoelectricity above the Curie temperature? Combining flexoelectricity and functional grading to enable high-temperature electromechanical coupling

    International Nuclear Information System (INIS)

    Most technologically relevant ferroelectrics typically lose piezoelectricity above the Curie temperature. This limits their use to relatively low temperatures. In this Letter, exploiting a combination of flexoelectricity and simple functional grading, we propose a strategy for high-temperature electromechanical coupling in a standard thin film configuration. We use continuum modeling to quantitatively demonstrate the possibility of achieving apparent piezoelectric materials with large and temperature-stable electromechanical coupling across a wide temperature range that extends significantly above the Curie temperature. With Barium and Strontium Titanate, as example materials, a significant electromechanical coupling that is potentially temperature-stable up to 900 °C is possible

  18. Exposure of W-TiC/Cu Functionally Graded Materials in the Edge Plasma of HT-7 Tokamak

    Institute of Scientific and Technical Information of China (English)

    刘洋; 朱大焕; 陈俊凌; 周张健; 鄢容

    2012-01-01

    Six-layered W-TiC/Cu functionally graded materials were fabricated by resistance sintering under ultra-high pressure and exposed in the edge plasma of HT-7 tokamak. Microstruc- ture morphologies show that the TiC particles distribute homogeneously in the W matrix, strength- ening the grain boundary, while gradient layers provide a good compositional transition from W- TiC to Cu. After about 360 shots in the HT-7 tokamak, clear surface modification can be observed after plasma exposure, and the addition of nano TiC particles is beneficial to the improvement of plasma loads resistance of W.

  19. Free Vibration of Size-Dependent Functionally Graded Microbeams Based on the Strain Gradient Reddy Beam Theory

    Science.gov (United States)

    Ansari, R.; Gholami, R.; Sahmani, S.

    2014-09-01

    The microscale vibration characteristics of microbeams made of functionally graded materials (FGMs) are investigated based on the strain gradient Reddy beam theory capable of capturing the size effect. The non-classical governing differential equations, together with the corresponding boundary conditions, are obtained using Hamilton's principle. Then, the free vibration problem of simply supported FGM microbeams is solved using the Navier solution. The natural frequencies of FGM microbeams are calculated corresponding to a wide range of dimensionless length scale parameters, material property gradient indices, and aspect ratios to illustrate the influences of size effect on the vibrational response of FGM microbeams.

  20. Elasto-plastic damage analysis of functionally graded material disks subjected to thermal shock and thermal cycle

    International Nuclear Information System (INIS)

    The elasto-plastic damage behaviors of functionally graded materials (FGM) subjected to thermal loading are analyzed by the finite element method using continuum damage mechanics. The Lemaitre's damage model is employed to analyze the damage behavior of a FGM disk subjected to thermal shock and a FGM coating subjected to thermal cycle. The effect of FGM on the thermal damage is discussed through some numerical examples for industrial materials. Numerical results show the validity of the present method for the evaluation and the development of new FGM. (author)

  1. Heat Conduction in a Functionally Graded Plate Subjected to Finite Cooling/Heating Rates: An Asymptotic Solution

    Directory of Open Access Journals (Sweden)

    Zhihe Jin

    2011-12-01

    Full Text Available This work investigates transient heat conduction in a functionally graded plate (FGM plate subjected to gradual cooling/heating at its boundaries. The thermal properties of the FGM are assumed to be continuous and piecewise differentiable functions of the coordinate in the plate thickness direction. A linear ramp function describes the cooling/heating rates at the plate boundaries. A multi-layered material model and Laplace transform are employed to obtain the transformed temperatures at the interfaces between the layers. An asymptotic analysis and an integration technique are then used to obtain a closed form asymptotic solution of the temperature field in the FGM plate for short times. The thermal stress intensity factor (TSIF for an edge crack in the FGM plate calculated based on the asymptotic temperature solution shows that the asymptotic solution can capture the peak TSIFs under the finite cooling rate conditions.

  2. Nonlinear Dynamic Behavior of Functionally Graded Truncated Conical Shell Under Complex Loads

    Science.gov (United States)

    Yang, S. W.; Hao, Y. X.; Zhang, W.; Li, S. B.

    Nonlinear dynamic behaviors of ceramic-metal graded truncated conical shell subjected to complex loads are investigated. The shell is modeled by first-order shear deformation theory. The nonlinear partial differential governing equation in terms of transverse displacements of the FGM truncated conical shell is derived from the Hamilton's principle. Galerkin's method is then utilized to discretize the partial governing equations to a two-degree-of-freedom nonlinear ordinary differential equation. The temperature-dependent materials properties of the constituents are graded in the radial direction in accordance with a power-law distribution. The aerodynamic pressure can be calculated by using the first-order piston theory. The temperature field is assumed to be a steady-state constant-temperature distribution. Bifurcation diagrams, the maximum Lyapunov exponents, wave forms and phase portraits are obtained by numerical simulation to demonstrate the complex nonlinear dynamics response of the FGM truncated conical shell. The influences of the semi-vertex angle, the material gradient index, in-plane and aerodynamic load on the nonlinear dynamics are studied.

  3. Developing Essential Understanding of Functions for Teaching Mathematics in Grades 9-12

    Science.gov (United States)

    Lloyd, Gwendolyn; Beckmann, Sybilla; Zbiek, Rose Mary; Cooney, Thomas

    2010-01-01

    Are sequences functions? What can't the popular "vertical line test" be applied in some cases to determine if a relation is a function? How does the idea of rate of change connect with simpler ideas about proportionality as well as more advanced topics in calculus? Helping high school students develop a robust understanding of functions requires…

  4. Processing and Characterization of Functionally Graded Aluminum (A319)—SiCp Metallic Composites by Centrifugal Casting Technique

    Science.gov (United States)

    Jayakumar, E.; Jacob, Jibin C.; Rajan, T. P. D.; Joseph, M. A.; Pai, B. C.

    2016-08-01

    Functionally graded materials (FGM) are successfully adopted for the design and fabrication of engineering components with location-specific properties. The present study describes the processing and characterization of A319 Aluminum functionally graded metal matrix composites (FGMMC) with 10 and 15 wt pct SiCp reinforcements. The liquid stir casting method is used for composite melt preparation followed by FGMMC formation by vertical centrifugal casting method. The process parameters used are the mold preheating temperature of 523 K (250 °C), melt pouring temperature of 1013 K (740 °C), and mold rotation speed of 1300 rpm. The study analyzes the distribution and concentration of reinforcement particles in the radial direction of the FGMMC disk along with the effects of gradation on density, hardness, mechanical strength, the variation in coefficient of thermal expansion and the wear resistance properties at different zones. Microstructures of FGMMC reveal an outward radial gradient distribution of reinforcements forming different zones. Namely, matrix-rich inner, transition, particles-rich outer, and chill zone of a few millimeters thick at the outer most periphery of the casting are formed. From 10-FGM, a radial shift in the position of SiCp maxima is observed in 15-FGM casting. The mechanical characterization depicts enhanced properties for the particle-rich zone. The hardness shows a graded nature in correlation with particle concentration and a maximum of 94.4 HRB has been obtained at the particle-rich region of 15-FGM. In the particle-rich zone, the lowest CTE value of 20.1 µm/mK is also observed with a compressive strength of 650 MPa and an ultimate tensile strength of 279 MPa. The wear resistance is higher at the particle-rich zone of the FGMMC.

  5. Processing and Characterization of Functionally Graded Aluminum (A319)—SiCp Metallic Composites by Centrifugal Casting Technique

    Science.gov (United States)

    Jayakumar, E.; Jacob, Jibin C.; Rajan, T. P. D.; Joseph, M. A.; Pai, B. C.

    2016-06-01

    Functionally graded materials (FGM) are successfully adopted for the design and fabrication of engineering components with location-specific properties. The present study describes the processing and characterization of A319 Aluminum functionally graded metal matrix composites (FGMMC) with 10 and 15 wt pct SiCp reinforcements. The liquid stir casting method is used for composite melt preparation followed by FGMMC formation by vertical centrifugal casting method. The process parameters used are the mold preheating temperature of 523 K (250 °C), melt pouring temperature of 1013 K (740 °C), and mold rotation speed of 1300 rpm. The study analyzes the distribution and concentration of reinforcement particles in the radial direction of the FGMMC disk along with the effects of gradation on density, hardness, mechanical strength, the variation in coefficient of thermal expansion and the wear resistance properties at different zones. Microstructures of FGMMC reveal an outward radial gradient distribution of reinforcements forming different zones. Namely, matrix-rich inner, transition, particles-rich outer, and chill zone of a few millimeters thick at the outer most periphery of the casting are formed. From 10-FGM, a radial shift in the position of SiCp maxima is observed in 15-FGM casting. The mechanical characterization depicts enhanced properties for the particle-rich zone. The hardness shows a graded nature in correlation with particle concentration and a maximum of 94.4 HRB has been obtained at the particle-rich region of 15-FGM. In the particle-rich zone, the lowest CTE value of 20.1 µm/mK is also observed with a compressive strength of 650 MPa and an ultimate tensile strength of 279 MPa. The wear resistance is higher at the particle-rich zone of the FGMMC.

  6. Interface Behavior in Functionally Graded Ceramics for the Magnetic Refrigeration: Numerical Modeling

    DEFF Research Database (Denmark)

    Jabbari, Masoud; Spangenberg, Jon; Hattel, Jesper Henri

    2013-01-01

    influence of the different material properties, i.e. the density and the viscosity, on the interface between the flows, since this is highly important for the efficiency of the device. The Newtonian flow behavior with relatively high viscosity is assumed for each fluid and used in the simulation with a......The active magnetic regenerator refrigerator is currently the most common magnetic refrigeration device for near room temperature applications, and it is driven by the magnetocaloric effect in the regenerator material. In order to make this efficient, a graded configuration of the magnetocaloric...... commercial CFD code (ANSYS FLUENT). The results show that the density change does not affect the interface between the adjacent fluids. The viscosity of the fluids plays the most important role in the behavior of the interface. Moreover, increasing the viscosity difference of the adjacent flows, Δμ , leads...

  7. Modeling of the interface behavior in tape casting of functionally graded ceramics for magnetic refrigeration parts

    DEFF Research Database (Denmark)

    Jabbari, Masoud; Spangenberg, Jon; Hattel, Jesper Henri

    2013-01-01

    graded configuration of the magnetocaloric materials. The Newtonian flow behavior with relatively high viscosity is assumed for each fluid and used in the simulation with a commercial CFD code (ANSYS FLUENT). The results show that the density difference does not affect the interface between the adjacent......The main goal of this work is to study the multiple material flows in side-by-side (SBS) tape casting and analyze the influence of the different material properties, i.e. the density and the viscosity, on the interface between the fluids, since this is highly important for the efficiency of a...... fluids, whereas the viscosity of the fluids plays the most important role in the behavior of the interface. Moreover, increasing the viscosity difference of the adjacent fluids, Δμ, leads to increasing the diffusive region between them. However, this can be counteracted by decreasing the velocity by the...

  8. Functionally graded ZrO2-NiCrAlY coatings prepared by plasma spraying using pre-mixed, spheroidized powders

    International Nuclear Information System (INIS)

    Functionally graded ZrO2-NiCrAlY coatings were prepared by plasma spraying. Pre-mixed, plasma spheroidized powders were used as the feedstock. The advantage of using pre-mixed, spheroidized powders was to ensure chemical homogeneity and promote uniform density along the graded layers, and these pre-mixed powders are used to form the different interlayers of functionally graded coatings in the present study. The microstructure, density and microhardness changed gradiently in the ZrO2-NiCrAlY FGM (functionally graded materials) coatings. The bond strength of ZrO2-NiCrAlY FGM coatings with different graded layers was measured. Results showed that for as-sprayed coatings with the same thickness, the bond strength increased with the number of graded layers. The bond strength of the FGM coatings with five graded layers was about twice as high as that of the duplex coatings because of the significant reduction of the residual stress in the coatings. Experimental results also showed that the bond strength of as-sprayed FGM coating increased significantly after hot isostatic press (HIP) treatment and the reason can be attributed to the densification of the microstructure, the decrease of defects in the coatings, interdiffusion between layers and reduction in the residual thermal stresses. (orig.)

  9. Cognitive function after radiotherapy for supratentorial low-grade glioma: A North Central Cancer Treatment Group prospective study

    International Nuclear Information System (INIS)

    Purpose: To evaluate the effects of cranial radiotherapy (RT) on cognitive function in patients with supratentorial low-grade glioma. Methods and Materials: Twenty adult patients with supratentorial low-grade glioma were treated with 50.4 Gy (10 patients) or 64.8 Gy (10 patients) localized RT. The patients then were evaluated with an extensive battery of psychometric tests at baseline (before RT) and at approximately 18-month intervals for as long as 5 years after completing RT. To allow patients to serve as their own controls, cognitive performance was evaluated as change in scores over time. All patients underwent at least two evaluations. Results: Baseline test scores were below average compared with age-specific norms. At the second evaluation, the groups' mean test scores were higher than their initial performances on all psychometric measures, although the improvement was not statistically significant. No changes in cognitive performance were seen during the evaluation period when test scores were analyzed by age, treatment, tumor location, tumor type, or extent of resection. Conclusions: Cognitive function was stable after RT in these patients evaluated prospectively during 3 years of follow-up. Slight improvements in some cognitive areas are consistent with practice effects attributable to increased familiarity with test procedures and content

  10. Novel functionally graded acicular electrode for solid oxide cells fabricated by the freeze-tape-casting process

    Science.gov (United States)

    Chen, Yu; Bunch, Jacob; Li, Tingshuai; Mao, Zhengping; Chen, Fanglin

    2012-09-01

    The performance of electrode supported solid oxide cells is often limited by gas transport in the thick electrode support. In this study, a novel functionally graded acicular hydrogen electrode microstructure has been fabricated by the freeze-tape-casting method. The effects of freeze-tape-casting processing parameters such as solid loading, freezing bed temperature and tape pulling rate on the morphology of the hydrogen electrode support have been investigated. The electrochemical performance of the cells having the novel functionally graded acicular hydrogen electrode has been significantly improved. In the fuel cell mode, a high power output of 1.28 W cm-2 and a low polarization resistance of 0.166 Ω cm2 have been achieved at 800 °C with H2 as fuel and ambient air as oxidant using nickel-yttria-stabilized zirconia (YSZ) as the hydrogen electrode, YSZ as the electrolyte, and (La0.75Sr0.25)0.95MnO3-YSZ as the oxygen electrode. In the electrolysis mode, a high current density of 2.3 A cm-2 with 30 vol% absolute humidity in the hydrogen electrode at 800 °C has been achieved with an applied cell voltage of 1.6 V. It has been revealed that the novel acicular hydrogen electrode decreases the gas diffusion resistance, thus enhancing the cell performance.

  11. An evaluation of a coupled microstructural approach for the analysis of functionally graded composites via the finite-element method

    Science.gov (United States)

    Pindera, Marek-Jerzy; Dunn, Patrick

    1995-01-01

    A comparison is presented between the predictions of the finite-element analysis and a recently developed higher-order theory for functionally graded materials subjected to a thorough-thickness temperature gradient. In contrast to existing micromechanical theories that utilize classical (i.e., uncoupled) homogenization schemes to calculate micro-level and macro-level stress and displacement fields in materials with uniform or nonuniform fiber spacing (i.e., functionally graded materials), the new theory explicitly couples the microstructural details with the macrostructure of the composite. Previous thermo-elastic analysis has demonstrated that such coupling is necessary when: the temperature gradient is large with respect to the dimension of the reinforcement; the characteristic dimension of the reinforcement is large relative to the global dimensions of the composite and the number of reinforcing fibers or inclusions is small. In these circumstances, the standard micromechanical analyses based on the concept of the representative volume element used to determine average composite properties produce questionable results. The comparison between the predictions of the finite-element method and the higher-order theory presented herein establish the theory's accuracy in predicting thermal and stress fields within composites with a finite number of fibers in the thickness direction subjected to a thorough-thickness thermal gradient.

  12. Effect of Chloride ion and Zirconium hydride on thr corrosion and SCC behaviors of functionally graded Zirconium alloy p.683

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Y. [Department of Metallurgical and Materials Engineering, Sunmoon University, Asam (Korea, Republic of); Kim, B. G.; Lee, J. W.; Kang, Y. H. [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    2000-07-01

    Effect of chloride ion and zirconium hydride on the corrosion and stress corrosion cracking behaviors of functionally graded zirconium alloy was studied to develop an advanced nuclear cladding tubing. The functionally graded zirconium alloy had composition gradient of niobium, which was prepared with a hot pressing followed by cold deformation. The corrosion rates and potentials decreased with increasing FeCl{sub 3} and hydride content. The corrosion potentials before and after hydriding are -4.3 V{sub SHE}, 8.8x10{sup -5} A{sub cm}{sup -2} and -12.5 V{sub SHE}, 3.9x10{sup -4} A{sub cm}{sup -2}, respectively. The stress corrosion cracking susceptibility decreased with elongation rate, indicating the saturation value at 5x10{sup -7} sec{sup -1}. SEM observation showed that brittle fracture with corrosion products and pits were observed on the failed surface of hydrided zirconium alloy, suggesting anodic dissolution occurred during exposure after cracking growth along zirconium hydrides. (author)

  13. Experimental investigation and analysis on flexural performance of functionally graded composite beam crack-controlled by ultrahigh toughness cementitious composites

    Institute of Scientific and Technical Information of China (English)

    LI QingHua; XU ShiLang

    2009-01-01

    Based on the concept of functionally graded concrete, UHTCC (ultrahigh toughness cementitious composites) material with excellent crack-controlling ability is strategically substituted for part of the concrete, which surrounds the main longitudinal reinforcement in a reinforced concrete member. In-vestigations on bending behavior of such a functionally graded composite beam crack-controlled by UHTCC (abbreviated as UHTCC-FGC beam) have been carried out. After establishing a theoretical cal-culation model, the paper discusses the results of four-point bending experiment on long composite beams without web reinforcement, and validates the theoretical formulae through experimental results of UHTCC-FGC beams with different thicknesses of UHTCC layer. Besides improving bearing capacity and saving steel reinforcements, the results indicate that UHTCC-FGC beams can also effectively con-trol the deformation and enhance the ductility of members. At last, the optimal thickness of UHTCC layer in UHTCC-FGC beams has been confirmed, which can not only save materials and improve me-chanical performance of members, but also be very effective in preventing corrosion-induced damage and enhancing the durability of members by controlling crack width below 0.05 mm under service con-ditions.

  14. Experimental investigation and analysis on flexural performance of functionally graded composite beam crack-controlled by ultrahigh toughness cementitious composites

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Based on the concept of functionally graded concrete,UHTCC(ultrahigh toughness cementitious composites)material with excellent crack-controlling ability is strategically substituted for part of the concrete,which surrounds the main longitudinal reinforcement in a reinforced concrete member.Investigations on bending behavior of such a functionally graded composite beam crack-controlled by UHTCC(abbreviated as UHTCC-FGC beam)have been carried out.After establishing a theoretical cal-culation model,the paper discusses the results of four-point bending experiment on long composite beams without web reinforcement,and validates the theoretical formulae through experimental results of UHTCC-FGC beams with different thicknesses of UHTCC layer.Besides improving bearing capacity and saving steel reinforcements,the results indicate that UHTCC-FGC beams can also effectively control the deformation and enhance the ductility of members.At last,the optimal thickness of UHTCC layer in UHTCC-FGC beams has been confirmed,which can not only save materials and improve mechanical performance of members,but also be very effective in preventing corrosion-induced damage and enhancing the durability of members by controlling crack width below 0.05mm under service conditions.

  15. Orientation of Al3Ti platelets in Al-Al3Ti functionally graded material manufactured by centrifugal method

    International Nuclear Information System (INIS)

    Al-Al3Ti functionally graded materials (FGMs) were manufactured by the centrifugal method with a commercial ingot of Al-5 mass% Ti master alloy. The alloy was melted at a liquid/solid coexisting temperature, at which Al3Ti remains as a solid, and then it was cast into a thick-walled ring. It was found that the Al-Al3Ti functionally graded material can be successfully fabricated by the centrifugal method. It was also found that the volume fraction of the Al3Ti can be increased by repetition of the centrifugal method. Since the shape of Al3Ti particles in a commercial alloy ingot is that of a platelet, the Al3Ti particles are arranged with their platelet planes nearly perpendicular to the radial direction. The orientation effects become stronger when the G number becomes larger. Although the final centrifugal casting was conducted under a very large centrifugal force for the specimen cast three times, the orientation effects were weaker than those in the specimen cast one time. From these observations, it is concluded that the origin of orientation of Al3Ti platelets can be attributed to the angular velocity gradient of the melt along the radial direction produced by the difference in the viscosity. (orig.)

  16. Application of the Reverberation-Ray Matrix to the Non-Fourier Heat Conduction in Functionally Graded Materials

    Science.gov (United States)

    Zhou, Feng-xi

    2016-02-01

    The method of the reverberation-ray matrix has been developed and successfully applied to analyse the wave propagation in a multibranched framed structure or in a layered medium. However, the method is confined to the case of mechanical loads applied at the medium until now. This paper aims to extend the formulation of the reverberation-ray matrix to cases of thermal propagation and diffusion. The thermal response in functionally graded materials (FGM) with the non-Fourier heat conduction model is analysed. In the present work, it is assumed that the material properties of an FG plate vary only in the thickness direction by following the power law function. The effect of non-Fourier and material inhomogeneity in the plate subjected to a periodic thermal disturbance is investigated. The present approach is validated by comparing it with the solutions obtained by other methods.

  17. Two Dimensional Functionally Graded Material Finite Thick Hollow Cylinder Axisymmetric Vibration Mode Shapes Analysis Based on Exact Elasticity Theory

    Directory of Open Access Journals (Sweden)

    Asgari Masoud

    2015-06-01

    Full Text Available A thick hollow cylinder with finite length made of two- dimensional functionally graded material (2D-FGM is considered and its natural modes are determined, based on great importance of mode shapes information in order to understand vibration behaviour of structures. Three dimensional theory of elasticity implemented for problem formulation, since mode shapes of a thick cylinder are three dimensional even with axisymmetric conditions. The axisymmetric conditions are assumed for the 2D-FGM cylinder. The material properties of the cylinder are varied in the radial and axial directions, with power law functions. Effects of volume fraction distribution on the different types of symmetric mode shapes configuration and vibration behaviour of a simply supported cylinder are analyzed. Three dimensional equations of motion are used and the eigen value problem is developed, based on direct variation method.

  18. Refractive error and visual functions in children with special needs compared with the first grade school students in Oman

    Directory of Open Access Journals (Sweden)

    Vora Urmi

    2010-01-01

    Full Text Available Background: We evaluated the refractive status and visual function of children with special needs (other handicap in 2010 and compared them with healthy 1 st grade school students in Oman. Materials and Methods: This was a cohort study. Optometrists recorded vision using a logarithm of minimum angle of resolution (LogMAR chart. Preferential looking method was used for testing 31 children. Cycloplegic refraction was performed on all children. Contrast sensitivity was tested using 2.5%, 10%, and 100% contrast charts. Ocular movement, alignment, and anterior segment were also assessed. A pediatrician reviewed the health records of all the children at the time of their enrollment in this study to determine if the child had been diagnosed with a systemic condition or syndromes. The visual functions were assessed by study investigators. We estimated the rates and the risk of different visual function defects in children with special needs. Result: The prevalence of refractive error in 70 children (4.7 ± 0.8 years with special needs (group 1 and 175 normal healthy first grade students (group 2 were 58.5% and 2.9%, respectively. The risk of refractive error was significantly higher in children with special needs [relative risk, 48.1 (95% confidence interval, 17.54-131.8]. Hyperopia (>1.00 D, myopia (≥ 1.00D and astigmatism (≥ ±1.00 D were found in 18.6%, 24.3%, and 27.1%, respectively, in group 1. Six children in this group had defective near vision. Sixteen (80% children with Down syndrome had refractive error. Seven (50% children with developmental disorder showed decreased contrast sensitivity. Conclusion: Prevalence of uncorrected refractive error was much higher in children with special needs. Prevalence of strabismus, nystagmus, and reduced contrast sensitivity was also higher in children with special needs. Early vision screening, visual function assessment, correction of refractive error, and frequent follow-up are recommended.

  19. Exact analytical solution of shear-induced flexural vibration of functionally graded piezoelectric beam

    Science.gov (United States)

    Sharma, Pankaj; Parashar, Sandeep Kumar

    2016-05-01

    The priority of this paper is to obtain the exact analytical solution for free flexural vibration of FGPM beam actuated using the d15 effect. In piezoelectric actuators, the potential use of d15 effect has been of particular interest for engineering applications since shear piezoelectric coefficient d15 is much higher than the other piezoelectric coupling constants d31 and d33. The applications of shear actuators are to induce and control the flexural vibrations of beams and plates. In this study, a modified Timoshenko beam theory is used where electric potential is assumed to vary sinusoidaly along the thickness direction. The material properties are assumed to be graded across the thickness in accordance with power law distribution. Hamilton`s principle is employed to obtain the equations of motion along with the associated boundary conditions for FGPM beams. Exact analytical solution is derived thus obtained equations of motion. Results for clamped-clamped and clamped-free boundary conditions are presented. The presented result and method shell serve as benchmark for comparing the results obtained from the other approximate methods.

  20. Microstructure and Resisting Thermal Shock Behaviors of TiC-Al2O3/Fe Functionally Graded MaterialsPrepared by SHS/PHIP

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The microstructure and composition of TiC-Al2O3/Fe functionally graded materials (FGM) prepared by self-propagating high temperature synthesis and pseudo-hot isostatic pressing (SHS/PHIP) were studied, and the resisting thermal shock behaviors were analyzed. The results show that TiC-Al2O3/Fe FGM has graded composition distribution. No cross-section crack through the layers was found in the tests of thermal shock and fatigue.

  1. Design and development of a powder mixing device used in the deposition of high velocity oxy-fuel (HVOF) thermal spray functionally graded coatings; Kabir Al Mamun

    OpenAIRE

    Al Mamun, Md. Kabir

    2007-01-01

    The application of Functionally Graded Materials (FGMs) is quite difficult, but thermal spray processes like Plasma spray have demonstrated their unique potential in producing graded deposits, where researchers have used twin powder feed systems to mix different proportions of powders. However the HVOF (High Velocity Oxy-Fuel) process does not possess this feature. FGMs vary in composition and/or microstructure from one boundary (substrate) to another (top service surface), and innovative cha...

  2. Nonlinear dynamic response of a simply supported rectangular functionally graded material plate under the time-dependent thermal mechanical loads

    Energy Technology Data Exchange (ETDEWEB)

    Hao, Y. X. [Beijing Information Science and Technology University, Beijing (China); Zhang, W. [Beijing University of Technology, Beijing (China); Yang, J. [RMIT University, Bundoora (Australia); Li, S. Y. [Ttianjin University of Technology and Education, Tianjin (China)

    2011-07-15

    An analysis on nonlinear dynamic characteristics of a simply supported functionally graded materials (FGMs) rectangular plate subjected to the transversal and in-plane excitations is presented in the time dependent thermal environment. Here we look the FGM Plates as isotropic materials which is assumed to be temperature dependent and graded in the thickness direction according to the power-law distribution in terms of volume fractions of the constituents. The geometrical nonlinearity using Von Karman's assumption is introduced. The formulation also includes in-plane and rotary inertia effects. In the framework of Reddy's third-order shear deformation plate theory, the governing equations of motion for the FGM plate are derived by the Hamilton's principle. Then the equations of motion with two degree- of-freedom under combined the time-dependent thermomechanical loads can be obtained by using Galerkin's method. Using numerical method, the control equations are analyzed to obtain the response curves. Under certain conditions the periodic and chaotic motions of the FGM plate are found. It is found that because of the existence of the temperature which relate to the time the motions of the FGM plate show the great difference. A period motion can be changed into the chaotic motions which are affected by the time dependent temperature.

  3. Fabrication of ZrO2/Mo-Si/Ni Functionally Graded Material by Dip-Coating

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    A slurry dip-coating technique was developed for fabrication of ZrO2/Mo-Si/Ni functionally graded material (FGM)on the stainless steel substrate. The rheological behavior of ZrO2-Ni-ethanol slurry was characterized by viscositytest. The amount of polyvinyl butyral (PVB) additives, which served as the dispersant and binder in ZrO2-Ni-ethanolslurry, was optimized. The results showed that the characters of mixed slurries with added 9 vol. pct (relativelyto total powders) MoSi2 powders prepared by mechanical alloying changed little. The stainless steel substrate wascoated several times by dipping in the slurries, and followed by drying in air every dipping. After debinding in Arin graphite die, the coated FGM plate was finally hot pressed at 1300℃ for 1 h under the pressure of 5 MPa in Arin the same die. Microstructural observations of the sintered FGM specimens revealed that the graded layers wereformed on the stainless steel substrate, in which no cracks were observed.

  4. Nonlinear dynamic response of a simply supported rectangular functionally graded material plate under the time-dependent thermal mechanical loads

    International Nuclear Information System (INIS)

    An analysis on nonlinear dynamic characteristics of a simply supported functionally graded materials (FGMs) rectangular plate subjected to the transversal and in-plane excitations is presented in the time dependent thermal environment. Here we look the FGM Plates as isotropic materials which is assumed to be temperature dependent and graded in the thickness direction according to the power-law distribution in terms of volume fractions of the constituents. The geometrical nonlinearity using Von Karman's assumption is introduced. The formulation also includes in-plane and rotary inertia effects. In the framework of Reddy's third-order shear deformation plate theory, the governing equations of motion for the FGM plate are derived by the Hamilton's principle. Then the equations of motion with two degree- of-freedom under combined the time-dependent thermomechanical loads can be obtained by using Galerkin's method. Using numerical method, the control equations are analyzed to obtain the response curves. Under certain conditions the periodic and chaotic motions of the FGM plate are found. It is found that because of the existence of the temperature which relate to the time the motions of the FGM plate show the great difference. A period motion can be changed into the chaotic motions which are affected by the time dependent temperature

  5. Buckling of Functionally Graded Nanobeams Based on the Nonlocal New First-Order Shear Deformation Beam Theory

    Directory of Open Access Journals (Sweden)

    Houari M.S.A.

    2014-04-01

    Full Text Available In this work, the size-dependent buckling behavior of functionally graded (FG nanobeams is investigated on the basis of the nonlocal continuum model. The material properties of FG nanobeams are assumed to vary through the thickness according to the power law. In addition, Poisson’s ratio is assumed constant in the current model. The nanobeams is modelled according to the new first order shear beam theory with small deformation and the equilibrium equations are derived using the Hamilton’s principle. The Naviertype solution is developed for simply-supported boundary conditions, and exact formulas are proposed for the buckling load. The effects of nonlocal parameter, aspect ratio, various material compositions on the stability responses of the FG nanobeams are discussed.

  6. Analytic investigation of effect of electric field on elasto-plastic response of a functionally graded piezoelectric hollow sphere

    Energy Technology Data Exchange (ETDEWEB)

    Atai, Ali Asghar [University of Tehran, Tehran (Iran, Islamic Republic of); Lak, Davaod [National Iranian Oil Co., Tehran (Iran, Islamic Republic of)

    2016-01-15

    In this work, the effect of electric potential on the mechanical (Stresses, strains, displacement) and electrical (electrical displacement and intensity) response of a Functionally graded piezoelectric (FGP) hollow sphere is analytically investigated. The sphere is under the action of internal/external pressure and temperature gradient as well. The inhomogeneity is based on power law in radial direction. The analysis is done in two parts: elastic response and plastic response, using Tresca yield criterion. It is shown by illustrative example that under internal pressure and assumed model parameters, the commencement of plastic region is from outside surface towards inside in the plastic zone is extended with the increase of electric potential. Interestingly, radial stress and displacement have an extreme not on the boundaries, but on the inside.

  7. Property Estimation of Functionally Graded Materials Between M2 Tool Steel and Cu Fabricated by Powder Metallurgy

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Jong-Seol; Shin, Ki-Hoon [Seoul National University of Science and Technology, Seoul (Korea, Republic of)

    2014-09-15

    The use of functionally graded materials (FGMs) may enhance thermal conductivity without reducing the desired strength in many applications such as injection molds embedding conformal cooling channels and cutting tools with heat sinks (or cooling devices). As a fundamental study for cutting tools having FGM heat sinks between M2 tool steel and Cu, six FGM specimens (M2 and Cu powders were premixed such that the relative compositions of M2 and Cu were 100:0, 80:20, 60:40, 40:60, 20:80, and 0:100 wt%) were fabricated by powder metallurgy in this study. The cross sections of these specimens were observed by optical microscopy, and then the material properties (such as thermal conductivity, specific heat, and coefficient of thermal expansion) related to heat transfer were measured and analyzed.

  8. Fast fabrication of W-Cu functionally graded material by high-gravity combustion synthesis and melt-infiltration

    Science.gov (United States)

    Zhao, P.; Guo, S. B.; Liu, G. H.; Chen, Y. X.; Li, J. T.

    2014-02-01

    W-Cu functionally graded material (FGM, 75 wt% W + 25 wt% Cu-40 wt% W + 60 wt% Cu) has been prepared by a method of high-gravity combustion synthesis and melt-infiltration in a short time (∼5 min). The infiltration mechanism in the high-gravity field was investigated. The W-Cu FGM showed an overall relative density of ∼97% and gradually-varying properties in terms of density, micro hardness, coefficient of thermal expansion. Especially, the W-Cu FGM exhibited a coefficient of thermal expansion between those of W and Cu, and thus could be used as a transition layer between W and Cu to relax the thermal stresses.

  9. Fast fabrication of W–Cu functionally graded material by high-gravity combustion synthesis and melt-infiltration

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, P. [Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); Graduate School of the Chinese Academy of Sciences, Beijing 100039 (China); Guo, S.B.; Liu, G.H.; Chen, Y.X. [Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); Li, J.T., E-mail: ljt0012@vip.sina.com [Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China)

    2014-02-01

    W–Cu functionally graded material (FGM, 75 wt% W + 25 wt% Cu—40 wt% W + 60 wt% Cu) has been prepared by a method of high-gravity combustion synthesis and melt-infiltration in a short time (∼5 min). The infiltration mechanism in the high-gravity field was investigated. The W–Cu FGM showed an overall relative density of ∼97% and gradually-varying properties in terms of density, micro hardness, coefficient of thermal expansion. Especially, the W–Cu FGM exhibited a coefficient of thermal expansion between those of W and Cu, and thus could be used as a transition layer between W and Cu to relax the thermal stresses.

  10. Fabrication of functionally graded materials between P21 tool steel and Cu by using laser aided layered manufacturing

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Jong Seol; Shin, Ki Hoon [Seoul Nat' l Univ., Seoul (Korea, Republic of)

    2013-01-15

    With the development of layered manufacturing, thermally conductive molds or molds embedding conformal cooling channels can be directly fabricated. Although P21 tool steel is widely used as a mold material because of its dimensional stability, it is not efficient for cooling molds owing to its low thermal conductivity. Hence, the use of functionally graded materials (FGMs) between P21 and Cu may circumvent a tradeoff between the strength and the heat transfer rate. As a preliminary study for the layered manufacturing of thermally conductive molds having FGM structures, one dimensional P21 Cu FGMs were fabricated by using laser aided direct metal tooling (DMT), and then, material properties such as the thermal conductivity and specific heat that are related to the heat transfer were measured and analyzed.

  11. A Novel Fabrication Method for Functionally Graded Materials under Centrifugal Force: The Centrifugal Mixed-Powder Method

    Directory of Open Access Journals (Sweden)

    Eri Miura-Fujiwara

    2009-12-01

    Full Text Available One of the fabrication methods for functionally graded materials (FGMs is a centrifugal solid-particle method, which is an application of the centrifugal casting technique. However, it is the difficult to fabricate FGMs containing nano-particles by the centrifugal solid-particle method. Recently, we proposed a novel fabrication method, which we have named the centrifugal mixed-powder method, by which we can obtain FGMs containing nano-particles. Using this processing method, Cu-based FGMs containing SiC particles and Al-based FGMs containing TiO2 nano-particles on their surfaces have been fabricated. In this article, the microstructure and mechanical property of Cu/SiC and Al/TiO2 FGMs, fabricated by the centrifugal mixed-powder method are reviewed.

  12. Fabrication of functionally graded materials between P21 tool steel and Cu by using laser aided layered manufacturing

    International Nuclear Information System (INIS)

    With the development of layered manufacturing, thermally conductive molds or molds embedding conformal cooling channels can be directly fabricated. Although P21 tool steel is widely used as a mold material because of its dimensional stability, it is not efficient for cooling molds owing to its low thermal conductivity. Hence, the use of functionally graded materials (FGMs) between P21 and Cu may circumvent a tradeoff between the strength and the heat transfer rate. As a preliminary study for the layered manufacturing of thermally conductive molds having FGM structures, one dimensional P21 Cu FGMs were fabricated by using laser aided direct metal tooling (DMT), and then, material properties such as the thermal conductivity and specific heat that are related to the heat transfer were measured and analyzed

  13. Fast fabrication of W–Cu functionally graded material by high-gravity combustion synthesis and melt-infiltration

    International Nuclear Information System (INIS)

    W–Cu functionally graded material (FGM, 75 wt% W + 25 wt% Cu—40 wt% W + 60 wt% Cu) has been prepared by a method of high-gravity combustion synthesis and melt-infiltration in a short time (∼5 min). The infiltration mechanism in the high-gravity field was investigated. The W–Cu FGM showed an overall relative density of ∼97% and gradually-varying properties in terms of density, micro hardness, coefficient of thermal expansion. Especially, the W–Cu FGM exhibited a coefficient of thermal expansion between those of W and Cu, and thus could be used as a transition layer between W and Cu to relax the thermal stresses

  14. Aluminum matrix texture in Al-Al3Ti functionally graded materials analyzed by electron back-scattering diffraction

    Science.gov (United States)

    Watanabe, Yoshimi; Sequeira, Paulo D.; Sato, Hisashi; Inamura, Tomonari; Hosoda, Hideki

    2016-01-01

    Al matrix functionally graded materials (FGMs) with oriented Al3Ti platelets were fabricated by a centrifugal solid-particle method. The applied centrifugal forces were 30, 60, and 120G (units of gravity). The orientation and volume fraction gradients of the Al3Ti platelets within the samples were measured. Since a good lattice correspondence was reported for the close-packed directions and the close-packed planes between Al and Al3Ti, the Al matrix in the Al-Al3Ti FGMs fabricated by the centrifugal solid-particle method should have some texture. Al matrix texture was, therefore, analyzed by electron back-scattering diffraction (EBSD). Analysis of the resulting pole figures indicates a preferred orientation along the (200) plane for the Al matrix crystals. Furthermore, increasing the applied centrifugal force enhances the orientation effect. A correlation appears to exist between platelet orientation and the preferred texture of the Al matrix.

  15. Synthesis and characterization of Al/SiC and Ni/Al2O3 functionally graded materials

    International Nuclear Information System (INIS)

    Two-multilayered functionally graded materials (FGMs), namely aluminium-silicon carbide (Al/SiC) and nickel-alumina (Ni/Al2O3) systems are designed, synthesized and characterized considering 10, 20, 30 and 40 vol.% ceramic concentrations. Two, three and five-layered FGMs are fabricated into flat beam samples following powder metallurgy route for Al/SiC and thermal spraying technique for Ni/Al2O3 system. Apart from microstructural studies, porosity content and microhardness are also determined. Three bulk properties are evaluated for FGM characterizations, namely effective flexural strength, thermal fatigue behavior and thermal shock resistance. Progressive and appreciable enhancement in FGM performance is observed as the number of layers is increased from two to five keeping the extreme layers same. Microhardness variation across the interfaces is found to be consistent with the analytically obtained jump in the inplane stresses at the interfaces

  16. Property Estimation of Functionally Graded Materials Between M2 Tool Steel and Cu Fabricated by Powder Metallurgy

    International Nuclear Information System (INIS)

    The use of functionally graded materials (FGMs) may enhance thermal conductivity without reducing the desired strength in many applications such as injection molds embedding conformal cooling channels and cutting tools with heat sinks (or cooling devices). As a fundamental study for cutting tools having FGM heat sinks between M2 tool steel and Cu, six FGM specimens (M2 and Cu powders were premixed such that the relative compositions of M2 and Cu were 100:0, 80:20, 60:40, 40:60, 20:80, and 0:100 wt%) were fabricated by powder metallurgy in this study. The cross sections of these specimens were observed by optical microscopy, and then the material properties (such as thermal conductivity, specific heat, and coefficient of thermal expansion) related to heat transfer were measured and analyzed

  17. Three-Dimensional Elasticity Solutions for Sound Radiation of Functionally Graded Materials Plates considering State Space Method

    Directory of Open Access Journals (Sweden)

    Tieliang Yang

    2016-01-01

    Full Text Available This paper presents an analytical study for sound radiation of functionally graded materials (FGM plate based on the three-dimensional theory of elasticity. The FGM plate is a mixture of metal and ceramic, and its material properties are assumed to have smooth and continuous variation in the thickness direction according to a power-law distribution in terms of volume fractions of the constituents. Based on the three-dimensional theory of elasticity and state space method, the governing equations with variable coefficients of the FGM plate are derived. The sound radiation of the vibration plate is calculated with Rayleigh integral. Comparisons of the present results with those of solutions in the available literature are made and good agreements are achieved. Finally, some parametric studies are carried out to investigate the sound radiation properties of FGM plates.

  18. Effects of acute hypoxia on renal and endocrine function at rest and during graded exercise in hydrated subjects

    DEFF Research Database (Denmark)

    Olsen, Niels Vidiendal; Kanstrup, I L; Richalet, J P;

    1992-01-01

    Renal effects of altitude hypoxia are unclear. Renal and hormonal function was investigated in eight males at rest and during graded exercise at sea level (SL) and 48 h after rapid ascent to 4,350 m (HA). HA did not change resting values of effective renal plasma flow (ERPF), glomerular filtration...... rate (GFR), sodium clearance (CNa), urine flow, or lithium clearance (CLi), which was used as an index of proximal tubular outflow. At rest, HA increased plasma norepinephrine concentration and decreased plasma concentrations of renin and aldosterone. Exercise decreased ERPF similarly in both...... environments. Normoxic exercise progressively reduced GFR, but at HA GFR only decreased during heavy exercise. This resulted in a higher filtration fraction during light and moderate hypoxic exercise. However, calculated absolute proximal reabsorption rate (GFR-CLi) at HA was higher during low...

  19. Functionally graded polymeric materials: A brif review of current fabrication methods and introduction of a novel fabrication method.

    Science.gov (United States)

    Almasi, Davood; Sadeghi, Maliheh; Lau, Woei Jye; Roozbahani, Fatemeh; Iqbal, Nida

    2016-07-01

    The present work reviews the current fabrication methods of the functionally graded polymeric material (FGPM) and introduces a novel fabrication method that is versatile in applications as compared to those of existing used methods. For the first time electrophoresis was used to control the distribution of the tetracycline hydrochloride (TC) in a film made of polylactic acid (PLA), aiming to induce antimicrobial effect on the film prepared. The elemental analysis on the film surface showed that by employing electrophoresis force, higher amount of TC was detected near the top surface of the film. Results also showed that the FGPM samples with higher percentage of the TC on the film surface were highly effective to minimize the growth of Escherichia coli. These findings are useful and important to improve dispersion quality of the particles in the composite material and further enhance its antibacterial property. PMID:27127033

  20. Impact of Writing Interventions Informed by Systemic Functional Linguistics with a Focus on Tenor, on Sixth, Seventh and Eighth Grade English Language Learners

    Science.gov (United States)

    Holmgren, Katherine Hayes

    2012-01-01

    This action research study examines the impact instruction informed by Systemic Functional Linguistics (SFL) with a particular focus on tenor and socio-cultural theory has on sixth, seventh and eighth grade English language learners in an urban school. Over the course of seven and 1/2 months I used Systemic Functional Linguistics with a focus on…

  1. The Role of the Executive Functions in School Achievement at the End of Grade 1

    Science.gov (United States)

    Monette, Sebastien; Bigras, Marc; Guay, Marie-Claude

    2011-01-01

    The aim of this study was to determine the role of executive functions (EFs) in early school achievement when a variety of potential confounding factors were controlled. Measures of EF (inhibition, flexibility, and working memory) and school readiness were administered to a sample of 85 kindergartners (39 boys and 46 girls, 5-6 years old). School…

  2. The Relationship Between Empathy, Self-Concept and Family Functioning among 5th Grade Elementary Students

    OpenAIRE

    Yüksel, Asuman

    2009-01-01

    The purpose of this study is to investigate the relationship between empathy, selfconcept and family functioning among elementary students. Data were gathered from 208 (105 male, 103 female) from Bursa Setbaşı Elemantary School, in 2003- 2004 academic year, fall semester. Data were gathered by using Index of Empathy for Children (IEC; Bryant, 1982), Family Assessment Device Scale (FAD; Epstein, et al., 1983), and Piers-Harris Self-Concept Scale Child Form (PHCSCS; Piers-Harris, 1984). T...

  3. Nonlinear dynamic analysis of eccentrically stiffened functionally graded circular cylindrical thin shells under external pressure and surrounded by an elastic medium

    International Nuclear Information System (INIS)

    A semi-analytical approach eccentrically stiffened functionally graded circular cylindrical shells surrounded by an elastic medium subjected to external pressure is presented. The elastic medium is assumed as two-parameter elastic foundation model proposed by Pasternak. Based on the classical thin shell theory with the geometrical nonlinearity in von Karman-Donnell sense, the smeared stiffeners technique and Galerkin method, this paper deals the nonlinear dynamic problem. The approximate three-term solution of deflection shape is chosen and the frequency-amplitude relation of nonlinear vibration is obtained in explicit form. The nonlinear dynamic responses are analyzed by using fourth order Runge-Kutta method and the nonlinear dynamic buckling behavior of stiffened functionally graded shells is investigated according to Budiansky-Roth criterion. Results are given to evaluate effects of stiffener, elastic foundation and input factors on the frequency-amplitude curves, natural frequencies, nonlinear responses and nonlinear dynamic buckling loads of functionally graded cylindrical shells. (authors)

  4. Nanoscale Graphene Disk: A Natural Functionally Graded Material–How is Fourier’s Law Violated along Radius Direction of 2D Disk

    Science.gov (United States)

    Yang, Nuo; Hu, Shiqian; Ma, Dengke; Lu, Tingyu; Li, Baowen

    2015-01-01

    In this Paper, we investigate numerically and analytically the thermal conductivity of nanoscale graphene disks (NGDs), and discussed the possibility to realize functionally graded material (FGM) with only one material, NGDs. Different from previous studies on divergence/non-diffusive of thermal conductivity in nano-structures with different size, we found a novel non-homogeneous (graded) thermal conductivity along the radius direction in a single nano-disk structure. We found that, instead of a constant value, the NGD has a graded thermal conductivity along the radius direction. That is, Fourier’s law of heat conduction is not valid in two dimensional graphene disk structures Moreover, we show the dependent of NGDs’ thermal conductivity on radius and temperature. Our study might inspire experimentalists to develop NGD based versatile FGMs, improve understanding of the heat removal of hot spots on chips, and enhance thermoelectric energy conversion efficiency by two dimensional disk with a graded thermal conductivity. PMID:26443206

  5. Nanoscale Graphene Disk: A Natural Functionally Graded Material-How is Fourier’s Law Violated along Radius Direction of 2D Disk

    Science.gov (United States)

    Yang, Nuo; Hu, Shiqian; Ma, Dengke; Lu, Tingyu; Li, Baowen

    2015-10-01

    In this Paper, we investigate numerically and analytically the thermal conductivity of nanoscale graphene disks (NGDs), and discussed the possibility to realize functionally graded material (FGM) with only one material, NGDs. Different from previous studies on divergence/non-diffusive of thermal conductivity in nano-structures with different size, we found a novel non-homogeneous (graded) thermal conductivity along the radius direction in a single nano-disk structure. We found that, instead of a constant value, the NGD has a graded thermal conductivity along the radius direction. That is, Fourier’s law of heat conduction is not valid in two dimensional graphene disk structures Moreover, we show the dependent of NGDs’ thermal conductivity on radius and temperature. Our study might inspire experimentalists to develop NGD based versatile FGMs, improve understanding of the heat removal of hot spots on chips, and enhance thermoelectric energy conversion efficiency by two dimensional disk with a graded thermal conductivity.

  6. Resecting diffuse low-grade gliomas to the boundaries of brain functions: a new concept in surgical neuro-oncology.

    Science.gov (United States)

    Duffau, H

    2015-12-01

    The traditional dilemma making surgery for diffuse low-grade gliomas (DLGGs) challenging is underlain by the need to optimize tumor resection in order to significantly increase survival versus the risk of permanent neurological morbidity. Development of neuroimaging led neurosurgeons to achieve tumorectomy according to the oncological limits provided by preoperative or intraoperative structural and metabolic imaging. However, this principle is not coherent, neither with the infiltrative nature of DLGGs nor with the limited resolution of current neuroimaging. Indeed, despite technical advances, MRI still underestimates the actual spatial extent of gliomas, since tumoral cells are present several millimeters to centimeters beyond the area of signal abnormalities. Furthermore, cortical and subcortical structures may be still crucial for brain functions despite their invasion by this diffuse tumoral disease. Finally, the lack of reliability of functional MRI has also been demonstrated. Therefore, to talk about "maximal safe resection" based upon neuroimaging is a non-sense, because oncological MRI does not show the tumor and functional MRI does not show critical neural pathways. This review proposes an original concept in neuro-oncological surgery, i.e. to resect DLGG to the boundaries of brain functions, thanks to intraoperative electrical mapping performed in awake patients. This paradigmatic shift from image-guided resection to functional mapping-guided resection, based upon an accurate study of brain connectomics and neuroplasticity in each patient throughout tumor removal has permitted to solve the classical dilemma, by increasing both survival and quality of life in DLGG patients. With this in mind, brain surgeons should also be neuroscientists. PMID:25907410

  7. Hippocampal Dosimetry Predicts Neurocognitive Function Impairment After Fractionated Stereotactic Radiotherapy for Benign or Low-Grade Adult Brain Tumors

    Energy Technology Data Exchange (ETDEWEB)

    Gondi, Vinai [Department of Human Oncology, University of Wisconsin, Madison, WI (United States); Hermann, Bruce P. [Department of Neurology, University of Wisconsin, Madison, WI (United States); Mehta, Minesh P. [Department of Radiation Oncology, Northwestern University Feinberg School of Medicine, Chicago, IL (United States); Tome, Wolfgang A., E-mail: tome@humonc.wisc.edu [Department of Human Oncology, University of Wisconsin, Madison, WI (United States); Department of Medical Physics, University of Wisconsin, Madison, WI (United States); Department of Biomedical Engineering, University of Wisconsin, Madison, WI (United States)

    2013-02-01

    Purpose: To prospectively evaluate the association between hippocampal dose and long-term neurocognitive function (NCF) impairment for benign or low-grade adult brain tumors treated with fractionated stereotactic radiotherapy (FSRT). Methods and Materials: Adult patients with benign or low-grade adult brain tumors were treated with FSRT per institutional practice. No attempt was made to spare the hippocampus. NCF testing was conducted at baseline and 18 months follow-up, on a prospective clinical trial. Regression-based standardized z scores were calculated by using similar healthy control individuals evaluated at the same test-retest interval. NCF impairment was defined as a z score {<=}-1.5. After delineation of the bilateral hippocampi according to the Radiation Therapy Oncology Group contouring atlas, dose-volume histograms were generated for the left and right hippocampi and for the composite pair. Biologically equivalent doses in 2-Gy fractions (EQD{sub 2}) assuming an {alpha}/{beta} ratio of 2 Gy were computed. Fisher's exact test and binary logistic regression were used for univariate and multivariate analyses, respectively. Dose-response data were fit to a nonlinear model. Results: Of 29 patients enrolled in this trial, 18 completed both baseline and 18-month NCF testing. An EQD{sub 2} to 40% of the bilateral hippocampi >7.3 Gy was associated with impairment in Wechsler Memory Scale-III Word List (WMS-WL) delayed recall (odds ratio [OR] 19.3; p = 0.043). The association between WMS-WL delayed recall and EQD{sub 2} to 100% of the bilateral hippocampi >0.0 Gy trended to significance (OR 14.8; p = 0.068). Conclusion: EQD{sub 2} to 40% of the bilateral hippocampi greater than 7.3 Gy is associated with long-term impairment in list-learning delayed recall after FSRT for benign or low-grade adult brain tumors. Given that modern intensity-modulated radiotherapy techniques can reduce the dose to the bilateral hippocampi below this dosimetric threshold

  8. Hippocampal Dosimetry Predicts Neurocognitive Function Impairment After Fractionated Stereotactic Radiotherapy for Benign or Low-Grade Adult Brain Tumors

    International Nuclear Information System (INIS)

    Purpose: To prospectively evaluate the association between hippocampal dose and long-term neurocognitive function (NCF) impairment for benign or low-grade adult brain tumors treated with fractionated stereotactic radiotherapy (FSRT). Methods and Materials: Adult patients with benign or low-grade adult brain tumors were treated with FSRT per institutional practice. No attempt was made to spare the hippocampus. NCF testing was conducted at baseline and 18 months follow-up, on a prospective clinical trial. Regression-based standardized z scores were calculated by using similar healthy control individuals evaluated at the same test–retest interval. NCF impairment was defined as a z score ≤−1.5. After delineation of the bilateral hippocampi according to the Radiation Therapy Oncology Group contouring atlas, dose–volume histograms were generated for the left and right hippocampi and for the composite pair. Biologically equivalent doses in 2-Gy fractions (EQD2) assuming an α/β ratio of 2 Gy were computed. Fisher’s exact test and binary logistic regression were used for univariate and multivariate analyses, respectively. Dose–response data were fit to a nonlinear model. Results: Of 29 patients enrolled in this trial, 18 completed both baseline and 18-month NCF testing. An EQD2 to 40% of the bilateral hippocampi >7.3 Gy was associated with impairment in Wechsler Memory Scale-III Word List (WMS-WL) delayed recall (odds ratio [OR] 19.3; p = 0.043). The association between WMS-WL delayed recall and EQD2 to 100% of the bilateral hippocampi >0.0 Gy trended to significance (OR 14.8; p = 0.068). Conclusion: EQD2 to 40% of the bilateral hippocampi greater than 7.3 Gy is associated with long-term impairment in list-learning delayed recall after FSRT for benign or low-grade adult brain tumors. Given that modern intensity-modulated radiotherapy techniques can reduce the dose to the bilateral hippocampi below this dosimetric threshold, patients should be enrolled in

  9. Meshless Local Petrov-Galerkin Method for Shallow Shells with Functionally Graded and Orthotropic Material Properties

    Science.gov (United States)

    Sladek, J.; Sladek, V.; Zhang, Ch.

    2008-02-01

    A meshless local Petrov-Galerkin (MLPG) formulation is presented for analysis of shear deformable shallow shells with orthotropic material properties and continuously varying material properties through the shell thickness. Shear deformation of shells described by the Reissner theory is considered. Analyses of shells under static and dynamic loads are given here. For transient elastodynamic case the Laplace-transform is used to eliminate the time dependence of the field variables. A weak formulation with a unit test function transforms the set of the governing equations into local integral equations on local subdomains in the plane domain of the shell. The meshless approximation based on the Moving Least-Squares (MLS) method is employed for the implementation.

  10. Potential of direct metal deposition technology for manufacturing thick functionally graded coatings and parts for reactors components

    International Nuclear Information System (INIS)

    Direct metal deposition (DMD) is an automated 3D deposition process arising from laser cladding technology with co-axial powder injection to refine or refurbish parts. Recently DMD has been extended to manufacture large-size near-net-shape components. When applied for manufacturing new parts (or their refinement), DMD can provide tailored thermal properties, high corrosion resistance, tailored tribology, multifunctional performance and cost savings due to smart material combinations. In repair (refurbishment) operations, DMD can be applied for parts with a wide variety of geometries and sizes. In contrast to the current tool repair techniques such as tungsten inert gas (TIG), metal inert gas (MIG) and plasma welding, laser cladding technology by DMD offers a well-controlled heat-treated zone due to the high energy density of the laser beam. In addition, this technology may be used for preventative maintenance and design changes/up-grading. One of the advantages of DMD is the possibility to build functionally graded coatings (from 1 mm thickness and higher) and 3D multi-material objects (for example, 100 mm-sized monolithic rectangular) in a single-step manufacturing cycle by using up to 4-channel powder feeder. Approved materials are: Fe (including stainless steel), Ni and Co alloys, (Cu,Ni 10%), WC compounds, TiC compounds. The developed coatings/parts are characterized by low porosity (<1%), fine microstructure, and their microhardness is close to the benchmark value of wrought alloys after thermal treatment (Co-based alloy Stellite, Inox 316L, stainless steel 17-4PH). The intended applications concern cooling elements with complex geometry, friction joints under high temperature and load, light-weight mechanical support structures, hermetic joints, tubes with complex geometry, and tailored inside and outside surface properties, etc

  11. Potential of direct metal deposition technology for manufacturing thick functionally graded coatings and parts for reactors components

    Science.gov (United States)

    Thivillon, L.; Bertrand, Ph.; Laget, B.; Smurov, I.

    2009-03-01

    Direct metal deposition (DMD) is an automated 3D deposition process arising from laser cladding technology with co-axial powder injection to refine or refurbish parts. Recently DMD has been extended to manufacture large-size near-net-shape components. When applied for manufacturing new parts (or their refinement), DMD can provide tailored thermal properties, high corrosion resistance, tailored tribology, multifunctional performance and cost savings due to smart material combinations. In repair (refurbishment) operations, DMD can be applied for parts with a wide variety of geometries and sizes. In contrast to the current tool repair techniques such as tungsten inert gas (TIG), metal inert gas (MIG) and plasma welding, laser cladding technology by DMD offers a well-controlled heat-treated zone due to the high energy density of the laser beam. In addition, this technology may be used for preventative maintenance and design changes/up-grading. One of the advantages of DMD is the possibility to build functionally graded coatings (from 1 mm thickness and higher) and 3D multi-material objects (for example, 100 mm-sized monolithic rectangular) in a single-step manufacturing cycle by using up to 4-channel powder feeder. Approved materials are: Fe (including stainless steel), Ni and Co alloys, (Cu,Ni 10%), WC compounds, TiC compounds. The developed coatings/parts are characterized by low porosity (joints under high temperature and load, light-weight mechanical support structures, hermetic joints, tubes with complex geometry, and tailored inside and outside surface properties, etc.

  12. An investigation on thermoelastic behaviour of functionally graded thick spherical vessels under combined thermal and mechanical loads

    Directory of Open Access Journals (Sweden)

    D. Karimi

    2008-12-01

    Full Text Available Purpose: The subject of this paper is to study the thermoelastic behavior of thick functionally graded hollow sphere under thermal and mechanical loads. The mechanical and thermal properties of FG sphere are assumed to be functions of radial position.Design/methodology/approach: In present study, two methods are used to estimate the effective mechanical properties of FG sphere. One of the simplest methods in estimation of the effective mechanical and thermal properties of a mixture of two constituent materials is the Rule of Mixture (R-M scheme. Another scheme for estimating the mechanical properties is due to the work of Mori-Tanaka. When the mechanical properties of FG sphere are estimated by using the Mori-Tanaka scheme, thermal material properties of FG body may be determined utilizing the R-M or the other methods which will be discussed as follows.Findings: Results for the temperature, radial displacement, radial stress and hoop stress fields through the geometry of the sphere are give. The figures reveal that some minor difference may be obtained for two schemes and the difference between the results for displacement distribution is larger than difference of temperature and stress distributions.Practical implications: The thermal material properties are obtained utilizing the Hatta-Taya and Rosen-Hashin relations. Also, the mechanical properties are estimated using the Mori-Tanaka scheme. In addition to the methods of approximation of material properties cited above, the rule of mixture scheme for determination of thermal and mechanical properties is also considered and results of these two schemes are compared for two cases of material composition through the geometry of FG sphere. The FG sphere is assumed to be symmetrically loaded and one-dimensional steady-state analysis of isotropic linear thermoelastic FG sphere under combined thermal and mechanical loads is investigated. Solution of the heat conduction equation and the Navier

  13. Optimal design of functionally graded PmPV/CNT nanocomposite cylindrical tube for purpose of torque transmission

    Institute of Scientific and Technical Information of China (English)

    Abolfazl Khalkhali; Sharif Khakshournia; Parvaneh Saberi

    2016-01-01

    Carbon nanotube (CNT)/polymer nanocomposites have vast application in industry because of their light mass and high strength. In this work, a cylindrical tube which is made up of functionally graded (FG) PmPV/CNT nanocomposite, is optimally designed for the purpose of torque transmission. The main confining parameters of a rotating shaft in torque transmission process are mass of the shaft, critical speed of rotation and critical buckling torque. It is required to solve a multi-objective optimization problem (MOP) to consider these three targets simultaneously in the process of design. The three-objective optimization problem for this case is defined and solved using a hybrid method of FEM and modified non-dominated sorting genetic algorithm (NSGA-II), by coupling two softwares, MATLAB and ABAQUS. Optimization process provides a set of non-dominated optimal design vectors. Then, two methods, nearest to ideal point (NIP) and technique for ordering preferences by similarity to ideal solution (TOPSIS), are employed to choose trade-off optimum design vectors. Optimum parameters that are obtained from this work are compared with the results of previous studies for similar cylindrical tubes made from composite or a hybrid of aluminum and composite that more than 20% improvement is observed in all of the objective functions.

  14. Investigating the thermal environment effects on geometrically nonlinear vibration of smart functionally graded plates

    Energy Technology Data Exchange (ETDEWEB)

    Ebrahimi, Farzad; Rastgoo, Abbas; Bahrami, Mansoor Nikkhah [University of Tehran, Tehran (Iran, Islamic Republic of)

    2010-03-15

    An analytical solution for a sandwich circular FGM plate coupled with piezoelectric layers under one-dimensional heat conduction is presented. All materials of the device may be of any functional gradients in the direction of thickness. The solution exactly satisfies all the equilibrium conditions and continuity conditions for the stress, displacement and electric displacement as well as electric potential on the interfaces between adjacency layers. A nonlinear static problem is solved first to determine the initial stress state and pre-vibration deformations of the FG plate that is subjected to in-plane forces and applied actuator voltage in thermal environment in the case of simply supported boundary conditions. By adding an incremental dynamic state to the pre-vibration state, the differential equations that govern the nonlinear vibration behavior of pre-stressed piezoelectric coupled FGM plates are derived. The role of thermal environment as well as control effects on nonlinear static deflections and natural frequencies imposed by the piezoelectric actuators using high input voltages are investigated. Numerical examples are provided and simulation results are discussed. Numerical results for FGM plates with a mixture of metal and ceramic are presented in dimensionless forms. The good agreement between the results of this paper and those of the finite element (FE) analyses validated the presented approach. In a parametric study the emphasis is placed on investigating the effect of varying the applied actuator voltage and thermal environment as well as gradient index of FG plate on the dynamics and control characteristics of the structure

  15. Investigating the thermal environment effects on geometrically nonlinear vibration of smart functionally graded plates

    International Nuclear Information System (INIS)

    An analytical solution for a sandwich circular FGM plate coupled with piezoelectric layers under one-dimensional heat conduction is presented. All materials of the device may be of any functional gradients in the direction of thickness. The solution exactly satisfies all the equilibrium conditions and continuity conditions for the stress, displacement and electric displacement as well as electric potential on the interfaces between adjacency layers. A nonlinear static problem is solved first to determine the initial stress state and pre-vibration deformations of the FG plate that is subjected to in-plane forces and applied actuator voltage in thermal environment in the case of simply supported boundary conditions. By adding an incremental dynamic state to the pre-vibration state, the differential equations that govern the nonlinear vibration behavior of pre-stressed piezoelectric coupled FGM plates are derived. The role of thermal environment as well as control effects on nonlinear static deflections and natural frequencies imposed by the piezoelectric actuators using high input voltages are investigated. Numerical examples are provided and simulation results are discussed. Numerical results for FGM plates with a mixture of metal and ceramic are presented in dimensionless forms. The good agreement between the results of this paper and those of the finite element (FE) analyses validated the presented approach. In a parametric study the emphasis is placed on investigating the effect of varying the applied actuator voltage and thermal environment as well as gradient index of FG plate on the dynamics and control characteristics of the structure

  16. Mechanical characterization of hybrid and functionally-graded aluminum open-cell foams with nanocrystalline-copper coatings

    Science.gov (United States)

    Sun, Yi

    Cellular/foam materials found in nature such as bone, wood, and bamboo are usually functionally graded by having a non-uniform density distribution and inhomogenous composition that optimizes their global mechanical performance. Inspired by such naturally engineered products, the current study was conducted towards the development of functionally graded hybrid metal foams (FGHMF) with electrodeposited (ED) nanocrystalline coatings. First, the deformation and failure mechanisms of aluminum/copper (Al/Cu) hybrid foams were investigated using finite element analyses at different scales. The micro-scale behavior was studied based on single ligament models discretized using continuum elements and the macro-scale behavior was investigated using beam-element based finite element models of representative unit volumes consisting of multiple foam cells. With a detailed constitutive material behavior and material failure considered for both the aluminum ligament and the nano-copper coating, the numerical models were able to capture the unique behavior of Al/Cu hybrid foams, such as the typically observed sudden load drop after yielding. The numerical models indicate that such load drop is caused by the fracture of foam ligaments initiated from the rupture of the ED nano-copper coating due to its low ductility. This failure mode jeopardizes the global energy absorption capacity of hybrid foams, especially when a thick coating is applied. With the purpose of enhancing the performance of Al/Cu hybrid foams, an annealing process, which increased the ductility of the nanocrystalline copper coating by causing recovery, recrystallination and grain growth, was introduced in the manufacturing of Al/Cu hybrid foams. Quasi-static experimental results indicate that when a proper amount of annealing is applied, the ductility of the ED copper can be effectively improved and the compressive and tensile behavior of Al/Cu hybrid foams can be significantly enhanced, including better energy

  17. Markers of T cell infiltration and function associate with favorable outcome in vascularized high-grade serous ovarian carcinoma.

    Directory of Open Access Journals (Sweden)

    Katelin N Townsend

    Full Text Available BACKGROUND: When T cells infiltrate the tumor environment they encounter a myriad of metabolic stressors including hypoxia. Overcoming the limitations imposed by an inadequate tumor vasculature that contributes to these stressors may be a crucial step to immune cells mounting an effective anti-tumor response. We sought to determine whether the functional capacity of tumor infiltrating lymphocytes (TIL could be influenced by the tumor vasculature and correlated this with survival in patients with ovarian cancer. METHODOLOGY AND PRINCIPAL FINDINGS: In 196 high-grade serous ovarian tumors, we confirmed that the tumor vascularity as measured by the marker CD31 was associated with improved patient disease-specific survival. We also found that tumors positive for markers of TIL (CD8, CD4 and forkhead box P3 (FoxP3 and T cell function (granzyme B and T-cell restricted intracellular antigen-1 (TIA-1 correlated significantly with elevated vascularity. In vitro, hypoxic CD8 T cells showed reduced cytolytic activity, secreted less effector cytokines and upregulated autophagy. Survival analysis revealed that patients had a significant improvement in disease-specific survival when FoxP3 expressing cells were present in CD31-high tumors compared to patients with FoxP3 expressing cells in CD31-low tumors [HR: 2.314 (95% CI 1.049-5.106; p = 0.0377]. Patients with high vascular endothelial growth factor (VEGF expressing tumors containing granzyme B positive cells had improved survival compared to patients with granzyme B positive cells in VEGF-low tumors [HR: 2.522 (95% CI 1.097-5.799; p = 0.0294]. SIGNIFICANCE: Overall, this data provides a rationale for developing strategies aimed at improving the adaptability and function of TIL to hypoxic tumor conditions.

  18. Processing of W-Cu functionally graded materials (FGM) through the powder metallurgy route: application as plasma facing components for ITER-like thermonuclear fusion reactor

    International Nuclear Information System (INIS)

    The aim of this study was to study and optimize the sintering of W-Cu graded composition materials, for first wall of ITER-like thermonuclear reactor application. The graded composition in the material generates graded functional properties (Functionally Graded Materials - FGM). Rough thermomechanical calculations have shown the interest of W-Cu FGM to improve the lifetime of Plasma Facing Components (PFC). To process W-Cu FGM, powder metallurgy route was analyzed and optimized from W-CuO powder mixtures. The influence of oxide reduction on the sintering of powder mixtures was highlighted. An optimal heating treatment under He/H2 atmosphere was determined. The sintering mechanisms were deduced from the analysis of the effect of the Cu-content. Sintering of W-Cu materials with a graded composition and grain size has revealed two liquid migration steps: i) capillary migration, after the Cu-melting and, ii) expulsion of liquid, at the end of sintering, from the dense part to the porous part, due to the continuation of W-skeleton sintering. These two steps were confirmed by a model based on capillary pressure calculation. In addition, thermal conductivity measurements were conducted on sintered parts and showed values which gradually increase with the Cu-content. Hardness tests on a polished cross-section in the bulk are consistent with the composition profiles obtained and the differential grain size. (author)

  19. Preparation and characterization of Al2O3-Ti3SiC2 composites and its functionally graded materials

    International Nuclear Information System (INIS)

    Alumina/titanium silicon carbide (Al2O3-Ti3SiC2) composites and its functionally graded materials (FGMs) were fabricated by a powder metallurgy processes and their microstructure and properties were investigated, respectively. The experimental results showed that the Vickers hardness of composites decreased with increasing Ti3SiC2 content while the fracture toughness and strength exhibited the opposite trend. Minimum Vickers hardness (4 GPa), maximum strength (598 MPa) and maximum toughness (11.24 MPa m1/2) were reached in the pure Ti3SiC2 material. Strength and hardness of FGMs were evaluated. Observation using an scanning electron microscope (SEM) indicated that the presence of Ti3SiC2 of FGMs inhibited the growth of alumina grains through a pinning mechanism. The study shows that the combination of the layered Ti3SiC2 structure and the fine alumina grains can result in a Al2O3-Ti3SiC2 composites possessing a high toughness and low Vickers hardness without a sacrifice in the strength

  20. Fracture of functionally graded materials: application to hydrided zircaloy; Fissuration des materiaux a gradient de proprietes: application au zircaloy hydrure

    Energy Technology Data Exchange (ETDEWEB)

    Perales, F

    2005-12-15

    This thesis is devoted to the dynamic fracture of functionally graded materials. More particularly, it deals with the toughness of nuclear cladding at high burnup submitted to transient loading. The fracture is studied at local scale using cohesive zone model in a multi body approach. Cohesive zone models include frictional contact to take into account mixed mode fracture. Non smooth dynamics problems are treated within the Non-Smooth Contact Dynamics framework. A multi scale study is necessary because of the dimension of the clad. At microscopic scale, the effective properties of surface law, between each body, are obtained by periodic numerical homogenization. A two fields Finite Element formulation is so written. An extended formulation of the NSCD framework is obtained. The associated software allows to simulate, in finite deformation, from the crack initiation to post-fracture behavior in heterogeneous materials. At microscopic scale, random RVE calculations are made to determine effective properties. At macroscopic scale, calculations of part of clad are made to determine the role of the mean hydrogen concentration and gradient of hydrogen parameters in the toughness of the clad under dynamic loading. (author)

  1. Cis-eQTL analysis and functional validation of candidate susceptibility genes for high-grade serous ovarian cancer

    Science.gov (United States)

    Lawrenson, Kate; Li, Qiyuan; Kar, Siddhartha; Seo, Ji-Heui; Tyrer, Jonathan; Spindler, Tassja J.; Lee, Janet; Chen, Yibu; Karst, Alison; Drapkin, Ronny; Aben, Katja K. H.; Anton-Culver, Hoda; Antonenkova, Natalia; Bowtell, David; Webb, Penelope M.; deFazio, Anna; Baker, Helen; Bandera, Elisa V.; Bean, Yukie; Beckmann, Matthias W.; Berchuck, Andrew; Bisogna, Maria; Bjorge, Line; Bogdanova, Natalia; Brinton, Louise A.; Brooks-Wilson, Angela; Bruinsma, Fiona; Butzow, Ralf; Campbell, Ian G.; Carty, Karen; Chang-Claude, Jenny; Chenevix-Trench, Georgia; Chen, Anne; Chen, Zhihua; Cook, Linda S.; Cramer, Daniel W.; Cunningham, Julie M.; Cybulski, Cezary; Dansonka-Mieszkowska, Agnieszka; Dennis, Joe; Dicks, Ed; Doherty, Jennifer A.; Dörk, Thilo; du Bois, Andreas; Dürst, Matthias; Eccles, Diana; Easton, Douglas T.; Edwards, Robert P.; Eilber, Ursula; Ekici, Arif B.; Fasching, Peter A.; Fridley, Brooke L.; Gao, Yu-Tang; Gentry-Maharaj, Aleksandra; Giles, Graham G.; Glasspool, Rosalind; Goode, Ellen L.; Goodman, Marc T.; Grownwald, Jacek; Harrington, Patricia; Harter, Philipp; Hasmad, Hanis Nazihah; Hein, Alexander; Heitz, Florian; Hildebrandt, Michelle A. T.; Hillemanns, Peter; Hogdall, Estrid; Hogdall, Claus; Hosono, Satoyo; Iversen, Edwin S.; Jakubowska, Anna; James, Paul; Jensen, Allan; Ji, Bu-Tian; Karlan, Beth Y.; Kruger Kjaer, Susanne; Kelemen, Linda E.; Kellar, Melissa; Kelley, Joseph L.; Kiemeney, Lambertus A.; Krakstad, Camilla; Kupryjanczyk, Jolanta; Lambrechts, Diether; Lambrechts, Sandrina; Le, Nhu D.; Lee, Alice W.; Lele, Shashi; Leminen, Arto; Lester, Jenny; Levine, Douglas A.; Liang, Dong; Lissowska, Jolanta; Lu, Karen; Lubinski, Jan; Lundvall, Lene; Massuger, Leon F. A. G.; Matsuo, Keitaro; McGuire, Valerie; McLaughlin, John R.; Nevanlinna, Heli; McNeish, Ian; Menon, Usha; Modugno, Francesmary; Moysich, Kirsten B.; Narod, Steven A.; Nedergaard, Lotte; Ness, Roberta B.; Azmi, Mat Adenan Noor; Odunsi, Kunle; Olson, Sara H.; Orlow, Irene; Orsulic, Sandra; Weber, Rachel Palmieri; Pearce, Celeste L.; Pejovic, Tanja; Pelttari, Liisa M.; Permuth-Wey, Jennifer; Phelan, Catherine M.; Pike, Malcolm C.; Poole, Elizabeth M.; Ramus, Susan J.; Risch, Harvey A.; Rosen, Barry; Rossing, Mary Anne; Rothstein, Joseph H.; Rudolph, Anja; Runnebaum, Ingo B.; Rzepecka, Iwona K.; Salvesen, Helga B.; Schildkraut, Joellen M.; Schwaab, Ira; Sellers, Thomas A.; Shu, Xiao-Ou; Shvetsov, Yurii B.; Siddiqui, Nadeem; Sieh, Weiva; Song, Honglin; Southey, Melissa C.; Sucheston, Lara; Tangen, Ingvild L.; Teo, Soo-Hwang; Terry, Kathryn L.; Thompson, Pamela J.; Timorek, Agnieszka; Tsai, Ya-Yu; Tworoger, Shelley S.; van Altena, Anne M.; Van Nieuwenhuysen, Els; Vergote, Ignace; Vierkant, Robert A.; Wang-Gohrke, Shan; Walsh, Christine; Wentzensen, Nicolas; Whittemore, Alice S.; Wicklund, Kristine G.; Wilkens, Lynne R.; Woo, Yin-Ling; Wu, Xifeng; Wu, Anna H.; Yang, Hannah; Zheng, Wei; Ziogas, Argyrios; Monteiro, Alvaro; Pharoah, Paul D.; Gayther, Simon A.; Freedman, Matthew L.

    2015-01-01

    Genome-wide association studies have reported 11 regions conferring risk of high-grade serous epithelial ovarian cancer (HGSOC). Expression quantitative trait locus (eQTL) analyses can identify candidate susceptibility genes at risk loci. Here we evaluate cis-eQTL associations at 47 regions associated with HGSOC risk (P≤10−5). For three cis-eQTL associations (P<1.4 × 10−3, FDR<0.05) at 1p36 (CDC42), 1p34 (CDCA8) and 2q31 (HOXD9), we evaluate the functional role of each candidate by perturbing expression of each gene in HGSOC precursor cells. Overexpression of HOXD9 increases anchorage-independent growth, shortens population-doubling time and reduces contact inhibition. Chromosome conformation capture identifies an interaction between rs2857532 and the HOXD9 promoter, suggesting this SNP is a leading causal variant. Transcriptomic profiling after HOXD9 overexpression reveals enrichment of HGSOC risk variants within HOXD9 target genes (P=6 × 10−10 for risk variants (P<10−4) within 10 kb of a HOXD9 target gene in ovarian cells), suggesting a broader role for this network in genetic susceptibility to HGSOC. PMID:26391404

  2. Fabrication of Al{sub 2}O{sub 3}-W Functionally Graded Materials by Slipcasting Method

    Energy Technology Data Exchange (ETDEWEB)

    Katayama, Tomoyuki; Sukenaga, Sohei; Saito, Noritaka; Nakashima, Kunihiko [Department of Materials Science and Engineering, Kyushu University, 744, Motooka, Nishiku, Fukuoka 819-0395 (Japan); Kagata, Hajime, E-mail: saito@zaiko.kyushu-u.ac.jp [Advanced Ceramic Section, TOTO Ltd., 2-1-1, Nakashima, Kokura, Kitakyushu, Fukuoka 802-8601 (Japan)

    2011-10-29

    We have successfully fabricated a functionally graded material (FGM) from tungsten and alumina powders by a slip-casting method. This FGM has applications as a sealing and conducting component for high-intensity discharge lamps (HiDLs) that have a translucent alumina envelope. Two types of W powder, with different oxidizing properties, were used as the raw powders for the Al{sub 2}O{sub 3}-W FGM. 'Oxidized W' was prepared by heat-treatment at 200 deg. C for 180 min in air. Alumina and each of the W powders were mixed in ultrapure water by ultrasonic stirring. The slurry was then cast into a cylindrical acrylic mold, which had a base of porous alumina, under controlled pressure. The green compacts were subsequently dried, and then sintered using a vacuum furnace at 1600 deg. C for a fixed time. The microstructures of the FGMs were observed by scanning electron microscopy (SEM) of the polished section. The Al{sub 2}O{sub 3}-W FGM with the 'oxidized W' powder resulted in a microscopic compositional gradient. However, the FGM with 'as-received W' showed no compositional gradient. This result was mainly attributed to the difference between the {zeta}-potentials of the W powders with the different oxidizing conditions; basically 'oxidized W' powder tends to disperse because of the larger {zeta}-potential of the oxide layer coated on the W powder core.

  3. Dynamic propagation of a weak-discontinuous interface crack between two dissimilar functionally graded layers under anti-plane shear

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Jeong Woo [Korea Aerospace Research Institute, Daejeon (Korea, Republic of); Lee, Young Shin [Chungnam National University, Daejeon (Korea, Republic of)

    2011-10-15

    The dynamic propagation of an interface crack between two functionally graded material (FGM) layers under anti-plane shear is analyzed using the integral transform method. The properties of the FGM layers vary continuously along their thicknesses. The properties of the two FGM layers vary and the two layers are connected weak-discontinuously. A constant velocity Yoffe-type moving crack is considered. The Fourier transform is used to reduce the problem to a dual integral equation, which is then expressed to a Fredholm integral equation of the second kind. Numerical values on the dynamic energy release rate (DERR) are presented for the FGM to show the effect of the gradient of material properties, crack moving velocity, and thickness of FGM layers. The following are helpful to increase resistance to interface crack propagation in FGMs: a) increasing the gradient of material properties, b) an increase of shear modulus and density from the interface to the upper and lower free surface, and c) increasing the thickness of the FGM layer. The DERR increases or decreases with increase of the crack moving velocity.

  4. Preparation of W–Cu functionally graded material coated with CVD–W for plasma-facing components

    Energy Technology Data Exchange (ETDEWEB)

    Song, Jiupeng, E-mail: jiupeng.song@hotmail.com [Xiamen Honglu Tungsten Molybdenum Industry Co. Ltd., 361021 Xiamen (China); Yu, Yang [Xiamen Honglu Tungsten Molybdenum Industry Co. Ltd., 361021 Xiamen (China); Zhuang, Zhigang [China National R and D Center for Tungsten Technology, Xiamen Tungsten Co. Ltd., 361026 Xiamen (China); Lian, Youyun; Liu, Xiang [Fusion Reactor Design and Material Division, Southwestern Institute of Physics, P.O. Box 432, 610041 Chengdu (China); Qi, Yang [College of Science, Northeastern University, 110819 Shenyang (China)

    2013-11-15

    W–Cu functionally graded materials (FGMs) are designed to be a transition layer between CuCrZr bulk material and a W surface layer in plasma-facing components. In this study, a type of in-house developed ultrafine W–Cu composite powder has been used to fabricate a W–Cu FGM, which consists of three layers of W–10Cu, W–32Cu, and W–60Cu respectively. The sintered FGM has a homogeneous microstructure and a residual porosity of less than 3.3%. The W–10Cu side of the FGM has been coated with pure W using an optimized chemical vapor deposition (CVD) process with an increased deposition rate of 0.8 mm/h. The thickness of the coating is around 2 mm and the density is as high as 19.23 g/cm{sup 3}. The columnar grain size of CVD–W at the end of deposition is approximately 20–50 μm in the direction parallel to the substrate and 1–1.5 mm in the direction perpendicular to the substrate. Compared with plasma-sprayed W–Cu FGM and W coating, the FGM and CVD–W developed in this study have a better microstructure, which is important for the thermal and physical properties of the components.

  5. Free vibration of functionally graded beams based on both classical and first-order shear deformation beam theories

    Institute of Scientific and Technical Information of China (English)

    李世荣; 万泽青; 张静华

    2014-01-01

    The free vibration of functionally graded material (FGM) beams is studied based on both the classical and the first-order shear deformation beam theories. The equations of motion for the FGM beams are derived by considering the shear deforma-tion and the axial, transversal, rotational, and axial-rotational coupling inertia forces on the assumption that the material properties vary arbitrarily in the thickness direction. By using the numerical shooting method to solve the eigenvalue problem of the coupled ordinary differential equations with different boundary conditions, the natural frequen-cies of the FGM Timoshenko beams are obtained numerically. In a special case of the classical beam theory, a proportional transformation between the natural frequencies of the FGM and the reference homogenous beams is obtained by using the mathematical similarity between the mathematical formulations. This formula provides a simple and useful approach to evaluate the natural frequencies of the FGM beams without dealing with the tension-bending coupling problem. Approximately, this analogous transition can also be extended to predict the frequencies of the FGM Timoshenko beams. The numerical results obtained by the shooting method and those obtained by the analogous transformation are presented to show the effects of the material gradient, the slenderness ratio, and the boundary conditions on the natural frequencies in detail.

  6. Studies on Interfacial Phenomena in Titanium Carbide/Liquid Steel Systems for Development of Functionally Graded Material

    Science.gov (United States)

    Kiviö, Miia; Holappa, Lauri; Louhenkilpi, Seppo; Nakamoto, Masashi; Tanaka, Toshihiro

    2016-08-01

    In modern materials' applications, versatile, often contradictory requirements are set for properties like high strength, hardness, and toughness. However, e.g., in steel castings, typically only certain surfaces should be hard and wear resistant, whereas the other "bulk" might have only standard properties. Then the critical parts of the surface should be "locally reinforced" to get functionally graded material. Expensive alloying elements are saved, and manufacturing stages are minimized. Titanium carbide is an extremely hard material widely applied in carbide tools. It could be used to reinforce steel castings. When TiC particles are added to liquid steel, wettability, stability, and dissolution are key phenomena that should be understood to better design and control manufacturing processes. In this work, the interfacial phenomena and reactions between TiC and iron/steel melts were examined by wetting experiments with special emphasis on the influence of Cr, Ni, and Mo. No significant effect on wettability was observed by Ni or Mo. High Cr melts showed somewhat higher contact angles. Partial penetration of liquid metal took place in the substrate along the grain boundaries. Ni seemed to promote penetration. During longer experiments, re-precipitation of carbides occurred on the liquid droplet influencing the apparent wetting angle. Cr and Mo promoted carbide formation.

  7. Fabrication of functionally graded PZT/Pt piezoelectric actuators; PZT/Pt den'atsu actuator no keisha kinoka

    Energy Technology Data Exchange (ETDEWEB)

    Terakubo, N.; Li, J.F.; Ono, M.; Watanabe, R. [Tohoku University, Sendai (Japan)

    2000-11-15

    Piezoelectric materials have received increasing attention in the field of electromechanical system because they can readily transfer an electrical signal to a mechanical movement. Unimorph and bimorph actuators that contain a piezoelectric plate and a metal plate are widely used to generate a larger bending displacement than an extensional-mode transducer. However, degradation may occur at the organic bonding interfaces after long time service. In this work, to develop a functionally graded PZT/Pt piezoelectric actuator, PZT/Pt composites with various composition ratios were prepared and characterized. (1) Dense PZT/Pt composite samples without any chemical reaction between the PZT and Pt phases were obtained by sintering in air at 1,200 degree C for 1 h. (2) The PZT/Pt composites that contained 20vol% Pt or less exhibited dielectric and piezoelectric properties, with piezoelectric constant decreasing with increasing Pt content. (3) FGM PZT/Pt bimorph actuators were designed using Taya's model and successfully fabricated via powder metallurgical routes. (author)

  8. Limit load analysis of shallow arches made of functionally bi-directional graded materials under mechanical loading

    International Nuclear Information System (INIS)

    Thin shallow arches may become unstable under transverse loading if the built-up internal compressive forces reach a limiting value beyond which the structure undergoes a sudden large displacement towards a new stable configuration. This phenomenon could be both desirable (in toggle switches) and disastrous (collapse of a dome or truss). Hence, the so-called snap- or limit-load analysis becomes important as to which factors influence it to give guidelines in designing structures to behave favorably. By the introduction of functionally graded materials (FGMs) in recent years, and incorporating them into this phenomenon, interesting results can be obtained which can give structures with favorable instability properties. In this work, a thin shallow arch with a modulus that can be varied along the thickness or the arch length or both is considered. Based on the governing equations of the deflected arch, the snap load is obtained in a mixed analytical-numerical approach and a parameter study of the critical load is carried out. Several verifying and interesting examples are presented

  9. Fabrication and characterization of functionally graded poly(vinylidine fluoride)-silver nanocomposite hollow fibers for sustainable water recovery

    KAUST Repository

    Francis, Lijo

    2014-12-01

    Poly(vinylidine fluoride) (PVDF) asymmetric hydrophobic hollow fibers were fabricated successfully using dryjet wet spinning. Hydrophobic silver nanoparticles were synthesized and impregnated into the PVDF polymer matrix and functionally graded PVDF-silver nanocomposite hollow fibers are fabricated and tested in the direct contact membrane distillation (DCMD) process. The as-synthesized silver nanoparticles were characterized for Transmission Electron Microscopy (TEM), particle size distribution (PSD) and Ultra Violet (UV) visible spectroscopy. Both the PVDF and PVDF-silver nanocomposite asymmetric hollow fibers were characterized for their morphology, water contact angle and mechanical strength. Addition of hydrophobic silver nanoparticles was found to enhance the hydrophobicity and ~ 2.5 fold increase the mechanical strength of the hollow fibers. A water vapor flux of 31.9kg m-2 h-1 was observed at a feed inlet temperature of 80 °C and at a permeate temperature of 20 °C in the case of hollow fiber membrane modules fabricated using PVDF hollow fibers; the water vapor flux was found to be increased by about 8% and to reach 34.6kg m-2 h-1 for the hollow fiber membrane modules fabricated from the PVDF-silver nanocomposite hollow fibers at the same operating conditions with 99.99% salt rejection.

  10. Fabrication of Al-Al3Ti/Ti3Al Functionally Graded Materials under a Centrifugal Force

    Directory of Open Access Journals (Sweden)

    Yoshimi Watanabe

    2010-09-01

    Full Text Available Fabrication of Al-Al3Ti functionally graded materials (FGMs under the centrifugal force has recently attracted some attention. The controlled compositional gradient of the fabricated FGMs, the low cost of the process, and the good mold filling, are the main advantages of the centrifugal method (CM. Using the conventional CM techniques such as the centrifugal solid-particle method and centrifugal in-situ method, FGMs rings with gradually distributed properties could be achieved. As a more practical choice, the centrifugal mixed-powder method (CMPM was recently proposed to obtain FGMs containing nano-particles selectively dispersed in the outer surface of the fabricated parts. However, if a control of the particles morphology, compound formulas or sizes, is desired, another CM technique is favored. As a development of CMPM, our novel reaction centrifugal mixed-powder method (RCMPM has been presented. Using RCMPM, Al‑Al3Ti/Ti3Al FGMs with good surface properties and temperature controlled compositional gradient could be achieved. In this short review, this novel method will be discussed in detail and the effect of RCMPM processing temperature on the reinforcement particles morphology, size and distribution through the fabricated samples, will be reviewed.

  11. Micromechanical Simulation of Thermal Cyclic Behavior of ZrO2/Ti Functionally Graded Thermal Barrier Coatings

    Directory of Open Access Journals (Sweden)

    Hideaki Tsukamoto

    2015-03-01

    Full Text Available This study numerically investigates cyclic thermal shock behavior of ZrO2/Ti functionally graded thermal barrier coatings (FG TBCs based on a nonlinear mean-field micromechanical approach, which takes into account the time-independent and dependent inelastic deformation, such as plasticity of metals, creep of metals and ceramics, and diffusional mass flow at the ceramic/metal interface. The fabrication processes for the FG TBCs have been also considered in the simulation. The effect of creep and compositional gradation patterns on micro-stress states in the FG TBCs during thermal cycling has been examined in terms of the amplitudes, ratios, maximum and mean values of thermal stresses. The compositional gradation patterns highly affect thermal stress states in case of high creep rates of ZrO2. In comparison with experimental data, maximum thermal stresses, amplitudes and ratios of thermal stresses can be effective parameters for design of such FG TBCs subject to cyclic thermal shock loadings.

  12. The nonlocal solution of two parallel cracks in functionally graded materials subjected to harmonic anti-plane shear waves

    Institute of Scientific and Technical Information of China (English)

    Jun Liang; Shiping Wu; Shanyi Du

    2007-01-01

    In this paper, the dynamic interaction of two parallel cracks in functionally graded materials (FGMs) is investigated by means of the non-local theory. To make the analysis tractable, the shear modulus and the material den-sity are assumed to vary exponentially with the coordinate vertical to the crack. To reduce mathematical difficulties, a one-dimensional non-local kemel is used instead of a two-dimensional one for the dynamic problem to obtain stress fields near the crack tips. By use of the Fourier transform,the problem can be solved with the help of two pairs of dual integral equations, in which the unknown variables are the jumps of displacements across the crack surfaces. To solve the dual integral equations, the jumps of displace-ments across the crack surfaces are expanded in a series of Jacobi polynomials. Unlike the classical elasticity solu-tions, it is found that no stress singularity is present at the crack tips. The non-local elastic solutions yield a finite hoop stress at the crack tips. The present result provides theoret-ical references helpful for evaluating relevant strength and preventing material failure of FGMs with initial cracks. The magnitude of the finite stress field depends on relevant param-eters, such as the crack length, the distance between two parallel cracks, the parameter describing the FGMs, the fre-quency of the incident waves and the lattice parameter of materials.

  13. Preparation of W–Cu functionally graded material coated with CVD–W for plasma-facing components

    International Nuclear Information System (INIS)

    W–Cu functionally graded materials (FGMs) are designed to be a transition layer between CuCrZr bulk material and a W surface layer in plasma-facing components. In this study, a type of in-house developed ultrafine W–Cu composite powder has been used to fabricate a W–Cu FGM, which consists of three layers of W–10Cu, W–32Cu, and W–60Cu respectively. The sintered FGM has a homogeneous microstructure and a residual porosity of less than 3.3%. The W–10Cu side of the FGM has been coated with pure W using an optimized chemical vapor deposition (CVD) process with an increased deposition rate of 0.8 mm/h. The thickness of the coating is around 2 mm and the density is as high as 19.23 g/cm3. The columnar grain size of CVD–W at the end of deposition is approximately 20–50 μm in the direction parallel to the substrate and 1–1.5 mm in the direction perpendicular to the substrate. Compared with plasma-sprayed W–Cu FGM and W coating, the FGM and CVD–W developed in this study have a better microstructure, which is important for the thermal and physical properties of the components

  14. Dynamic propagation of a weak-discontinuous interface crack between two dissimilar functionally graded layers under anti-plane shear

    International Nuclear Information System (INIS)

    The dynamic propagation of an interface crack between two functionally graded material (FGM) layers under anti-plane shear is analyzed using the integral transform method. The properties of the FGM layers vary continuously along their thicknesses. The properties of the two FGM layers vary and the two layers are connected weak-discontinuously. A constant velocity Yoffe-type moving crack is considered. The Fourier transform is used to reduce the problem to a dual integral equation, which is then expressed to a Fredholm integral equation of the second kind. Numerical values on the dynamic energy release rate (DERR) are presented for the FGM to show the effect of the gradient of material properties, crack moving velocity, and thickness of FGM layers. The following are helpful to increase resistance to interface crack propagation in FGMs: a) increasing the gradient of material properties, b) an increase of shear modulus and density from the interface to the upper and lower free surface, and c) increasing the thickness of the FGM layer. The DERR increases or decreases with increase of the crack moving velocity

  15. Thermal-mechanical analysis on W/CuCrZr plasma facing component with functionally graded material interlayer

    International Nuclear Information System (INIS)

    Thermal-mechanical analysis is performed on W/CuCrZr plasma facing component with functionally graded material (FGM) interlayer under the steady-state heat load of 5 MW/m2 using a finite element method (ANSYS code). The influences of the FGM interlayer on the stress, strain and temperature distribution in the whole component is evaluated and compared to the joint without an interlayer and with OFHC interlayer. It is shown that the inserting of W/CuCrZr FGM interlayer between W and CuCrZr effectively alleviates the thermal stress, whose reduction can reach up to 70% when the W/CuCrZr FGM interlayer thickness exceeds 6 mm. Meanwhile, the optimization of the structure and component distribution for W/CuCrZr FGM interlayer was also carried out. The thermal stress tends to saturate with the layer number exceeding 4. For 6 mm 4-layered FGM interlayer, the preferred component distribution exponent (p) is 1.8.

  16. Vibration analysis of rotating functionally graded Timoshenko microbeam based on modified couple stress theory under different temperature distributions

    Science.gov (United States)

    Ghadiri, Majid; Shafiei, Navvab

    2016-04-01

    In this study, thermal vibration of rotary functionally graded Timoshenko microbeam has been analyzed based on modified couple stress theory considering temperature change in four types of temperature distribution on thermal environment. Material properties of FG microbeam are supposed to be temperature dependent and vary continuously along the thickness according to the power-law form. The axial forces are also included in the model as the thermal and true spatial variation due to the rotation. Governing equations and boundary conditions have been derived by employing Hamiltonian's principle. The differential quadrature method is employed to solve the governing equations for cantilever and propped cantilever boundary conditions. Validations are done by comparing available literatures and obtained results which indicate accuracy of applied method. Results represent effects of temperature changes, different boundary conditions, nondimensional angular velocity, length scale parameter, different boundary conditions, FG index and beam thickness on fundamental, second and third nondimensional frequencies. Results determine critical values of temperature changes and other essential parameters which can be applicable to design micromachines like micromotor and microturbine.

  17. Nonlocal three-dimensional theory of elasticity with application to free vibration of functionally graded nanoplates on elastic foundations

    Science.gov (United States)

    Ansari, R.; Shahabodini, A.; Faghih Shojaei, M.

    2016-02-01

    In the present work, a three-dimensional (3D) elastic plate model capturing the small scale effects is developed for the free vibration of functionally graded (FG) nanoplates resting on elastic foundations. The theoretical model is formulated employing the nonlocal differential constitutive relations of Eringen in conjunction with the 3D equations of motion of elasticity.The material properties are assumed to vary continuously along the thickness of the nanoplate in accordance with the power law formulation. Through extending the generalized differential quadrature (GDQ) method to the three-dimensional case, the governing equations are simultaneously discretized in every three coordinate directions and are then recast to the standard form of an eigen value problem. Solving the acquired problem, the natural frequencies of the nanoplates with different boundary conditions are calculated. The convergence behavior of the numerical results is checked out and comparison studies are conducted to make sure of the accuracy and reliability of the present model. Finally, the dependence of the vibration behavior of the nanoplate on edge conditions, elastic coefficients of the foundation, scale coefficient, mode number, material and geometric parameters are discussed.

  18. Investigation on 316L/W functionally graded materials fabricated by mechanical alloying and spark plasma sintering

    Science.gov (United States)

    Tan, Chao; Wang, Guoyu; Ji, Lina; Tong, Yangang; Duan, Xuan-Ming

    2016-02-01

    316L-W (Tungsten) composite materials were fabricated by spark plasma sintering (SPS) of mechanically alloyed 316L-W powders for the development of functionally graded materials (FGMs). The effect of milling parameters on the morphology of the blended 316L/W powders and its subsequent effect on the transition between 316L and W particles during the SPS process were investigated. Samples were characterized by SEM, EDS and XRD analyses. The results so obtained show that with the increase of milling time, the mechanically activated W powder particles become thinner and smoother, with some broken fragments aggregated or inserted in the severely deformed 316L particles. A further SPS process under the conditions of 1050 °C × 45.5 MPa × 5 min leads to the densification of the powder compact and the formation of a distinguishable gray belt surrounding the retained W particles. Such a belt, which has a width of about 2-8 μm depending on different milling parameters and mainly contains Fe7W6, Fe3W3C and Fe2W phases, is bound to be a transitional region between the retained W particles and the 316L matrix. This favorable behavior with regards to the formation of a transitional belt, is accompanied by a substantial increase in the hardness values of the composite.

  19. Studies on Interfacial Phenomena in Titanium Carbide/Liquid Steel Systems for Development of Functionally Graded Material

    Science.gov (United States)

    Kiviö, Miia; Holappa, Lauri; Louhenkilpi, Seppo; Nakamoto, Masashi; Tanaka, Toshihiro

    2016-04-01

    In modern materials' applications, versatile, often contradictory requirements are set for properties like high strength, hardness, and toughness. However, e.g., in steel castings, typically only certain surfaces should be hard and wear resistant, whereas the other "bulk" might have only standard properties. Then the critical parts of the surface should be "locally reinforced" to get functionally graded material. Expensive alloying elements are saved, and manufacturing stages are minimized. Titanium carbide is an extremely hard material widely applied in carbide tools. It could be used to reinforce steel castings. When TiC particles are added to liquid steel, wettability, stability, and dissolution are key phenomena that should be understood to better design and control manufacturing processes. In this work, the interfacial phenomena and reactions between TiC and iron/steel melts were examined by wetting experiments with special emphasis on the influence of Cr, Ni, and Mo. No significant effect on wettability was observed by Ni or Mo. High Cr melts showed somewhat higher contact angles. Partial penetration of liquid metal took place in the substrate along the grain boundaries. Ni seemed to promote penetration. During longer experiments, re-precipitation of carbides occurred on the liquid droplet influencing the apparent wetting angle. Cr and Mo promoted carbide formation.

  20. Nondestructive observation of pore structure deformation behavior of functionally graded aluminum foam by X-ray computed tomography

    International Nuclear Information System (INIS)

    Cellular materials are expected to be used for the components of automobiles and as railway and building materials owing to their lightweight structures and desirable mechanical properties. The newest class of cellular materials consists of functionally graded aluminum (FG Al) foams, in which the properties vary with the position. In this study, closed-cell FG Al foam with a varying pore structure was fabricated and its deformation behavior during the compression tests was nondestructively observed by X-ray computed tomography (X-ray CT). The fabricated FG Al foam had different pore structures (different densities) in the same Al foam. The FG Al foam initially started to deform only in the low-density region, which was followed by deformation in the high-density region. The deformation of the FG Al foam indicated its novel mechanical properties, such as multiple plateau stresses, corresponding to the pore structures of the regions where deformation occurred. Consequently, it was shown that the FG Al foam with a varying pore structure and a seamless bonding interface has the potential to be deformed at a controlled and desired location and with a desired plateau stress.

  1. Amine-functionalized low-cost industrial grade multi-walled carbon nanotubes for the capture of carbon dioxide

    Institute of Scientific and Technical Information of China (English)

    Qing; Liu; Yao; Shi; Shudong; Zheng; Liqi; Ning; Qing; Ye; Mengna; Tao; Yi; He

    2014-01-01

    Industrial grade multi-walled carbon nanotubes(IG-MWCNTs) are a low-cost substitute for commercially purified multi-walled carbon nanotubes(P-MWCNTs). In this work, IG-MWCNTs were functionalized with tetraethylenepentamine(TEPA) for CO2capture. The TEPA impregnated IG-MWCNTs were characterized with various experimental methods including N2adsorption/desorption isotherms, elemental analysis, X-ray diffraction, Fourier transform infrared spectroscopy and thermogravimetric analysis. Both the adsorption isotherms of IGMWCNTs-n and the isosteric heats of different adsorption capacities were obtained from experiments. TEPA impregnated IG-MWCNTs were also shown to have high CO2adsorption capacity comparable to that of TEPA impregnated P-MWCNTs. The adsorption capacity of IG-MWCNTs based adsorbents was in the range of 2.145 to 3.088 mmol/g, depending on adsorption temperatures. Having the advantages of low-cost and high adsorption capacity, TEPA impregnated IG-MWCNTs seem to be a promising adsorbent for CO2capture from flue gas.

  2. Static/dynamic Analysis of Functionally Graded and Layered Magneto-electro-elastic Plate/pipe under Hamiltonian System

    Institute of Scientific and Technical Information of China (English)

    Dai Haitao; Cheng Wei; Li Mingzhi

    2008-01-01

    The 3-dimensional couple equations of magneto-electro-elastic structures are derived under Hamiltonian system based on the Hamilton principle. The problem of single sort of variables is converted into the problem of double sorts of variables, and the Hamilton canonical equations are established. The 3-dimensional problem of magneto-electro-elastic structure which is investigated in Euclidean space commonly is converted into symplectic system. At the same time the Lagrange system is converted into Hamiltonlan system. As an example, the dynamic characteristics of the simply supported functionally graded magneto-electro-elastic material (FGMM) plate and pipe are investigated. Finally, the problem is solved by symplectic algorithm. The results show that the physical quantifies of displace-ment, electric potential and magnetic potential etc. change continuously at the interfaces between layers under the transverse pressure while some other physical quantifies such as the stress, electric and magnetic displacement are not continuous. The dynamic stiffness is increased by the piezoelectric effect while decreased by the piezomagnetic effect.

  3. Effect of Heat Treatment on the Wear Behaviour of Functionally Graded LM13/B4C Composite

    Directory of Open Access Journals (Sweden)

    L.V. Priyanka Muddamsetty

    2016-03-01

    Full Text Available Aluminium alloy reinforced with boron carbide (10 wt.% was fabricated using stir casting method followed by centrifugal casting and the cylindrical specimen with dimension 150 x 150 x 15 mm was obtained. The composite specimens were heat treated at various aging temperatures and aging time for property improvement. Solution treatment was done at 525 ℃ for 5 hrs. Taguchi’s method was used for designing the plan of experiments and L27 orthogonal array was formulated for the analysis of data. The wear test was conducted on the outer periphery of centrifugally cast Functionally Graded composites using pin-on-disc tribometer. Optimization of parameters such as applied load (10 N, 20 N, 30 N, agingtemperature (150 ℃, 175 ℃, 200 ℃ and aging time (2 hrs, 6 hrs, 10 hrs was done using Signal-to-Noise ratio. “Smaller-the-better” criterion was used for analyzing the results. Results ended up with a conclusion that aging time (92.19 % had major influence on tribological behavior followed by aging temperature (5.36 % and applied load (1.95 %. Scanning Electron Microscope (SEM analysis was performed to understand the wear mechanism in heat treated specimens.

  4. Physical Properties of Normal Grade Biodiesel and Winter Grade Biodiesel

    OpenAIRE

    Azmi Zakaria; W. Mahmood Mat Yunus; Monir Norozi; Harrison Lau Lik Nang; Mohd Maarof Moksin; Amir Reza Sadrolhosseini

    2011-01-01

    In this study, optical and thermal properties of normal grade and winter grade palm oil biodiesel were investigated. Surface Plasmon Resonance and Photopyroelectric technique were used to evaluate the samples. The dispersion curve and thermal diffusivity were obtained. Consequently, the variation of refractive index, as a function of wavelength in normal grade biodiesel is faster than winter grade palm oil biodiesel, and the thermal diffusivity of winter grade biodiesel is higher than the the...

  5. Design of Co-sedimentation Experiments Used to Fabricate Functionally Graded Materials with a Continuous Change of Composition

    Institute of Scientific and Technical Information of China (English)

    YANG Zhong-min; GONG Dao-ren; ZHANG Lian-meng

    2004-01-01

    In the process of particle settling in a dilute,a density graded distribution of the liquid below the suspension needs to be designed according to the gravity of the suspension prior to sedimentation.In the present paper a compositionally graded W-Mo composite was formed via the settling of the W and Mo particles,with a density gradient distributed in the initial clear liquid along the settling direction.

  6. Evaluation of low-grade glioma structural changes after chemotherapy using DTI-based histogram analysis and functional diffusion maps

    International Nuclear Information System (INIS)

    To explore the role of diffusion tensor imaging (DTI)-based histogram analysis and functional diffusion maps (fDMs) in evaluating structural changes of low-grade gliomas (LGGs) receiving temozolomide (TMZ) chemotherapy. Twenty-one LGG patients underwent 3T-MR examinations before and after three and six cycles of dose-dense TMZ, including 3D-fluid-attenuated inversion recovery (FLAIR) sequences and DTI (b = 1000 s/mm2, 32 directions). Mean diffusivity (MD), fractional anisotropy (FA), and tensor-decomposition DTI maps (p and q) were obtained. Histogram and fDM analyses were performed on co-registered baseline and post-chemotherapy maps. DTI changes were compared with modifications of tumour area and volume [according to Response Assessment in Neuro-Oncology (RANO) criteria], and seizure response. After three cycles of TMZ, 20/21 patients were stable according to RANO criteria, but DTI changes were observed in all patients (Wilcoxon test, P ≤ 0.03). After six cycles, DTI changes were more pronounced (P ≤ 0.005). Seventy-five percent of patients had early seizure response with significant improvement of DTI values, maintaining stability on FLAIR. Early changes of the 25th percentiles of p and MD predicted final volume change (R2 = 0.614 and 0.561, P < 0.0005, respectively). TMZ-related changes were located mainly at tumour borders on p and MD fDMs. DTI-based histogram and fDM analyses are useful techniques to evaluate the early effects of TMZ chemotherapy in LGG patients. (orig.)

  7. Evaluation of low-grade glioma structural changes after chemotherapy using DTI-based histogram analysis and functional diffusion maps

    Energy Technology Data Exchange (ETDEWEB)

    Castellano, Antonella; Iadanza, Antonella; Falini, Andrea [San Raffaele Scientific Institute and Vita-Salute San Raffaele University, Neuroradiology Unit and CERMAC, Milano (Italy); Donativi, Marina [University of Salento, Department of Mathematics and Physics ' ' Ennio De Giorgi' ' and A.D.A.M. (Advanced Data Analysis in Medicine), Lecce (Italy); Ruda, Roberta; Bertero, Luca; Soffietti, Riccardo [University of Torino, Department of Neuro-oncology, Turin (Italy); De Nunzio, Giorgio [University of Salento, Department of Mathematics and Physics ' ' Ennio De Giorgi' ' and A.D.A.M. (Advanced Data Analysis in Medicine), Lecce (Italy); INFN (National Institute of Nuclear Physics), Lecce (Italy); Riva, Marco; Bello, Lorenzo [Universita degli Studi di Milano, Milan, and Humanitas Research Hospital, Department of Medical Biotechnology and Translational Medicine, Rozzano, MI (Italy); Rucco, Matteo [University of Camerino, School of Science and Technology, Computer Science Division, Camerino, MC (Italy)

    2016-05-15

    To explore the role of diffusion tensor imaging (DTI)-based histogram analysis and functional diffusion maps (fDMs) in evaluating structural changes of low-grade gliomas (LGGs) receiving temozolomide (TMZ) chemotherapy. Twenty-one LGG patients underwent 3T-MR examinations before and after three and six cycles of dose-dense TMZ, including 3D-fluid-attenuated inversion recovery (FLAIR) sequences and DTI (b = 1000 s/mm{sup 2}, 32 directions). Mean diffusivity (MD), fractional anisotropy (FA), and tensor-decomposition DTI maps (p and q) were obtained. Histogram and fDM analyses were performed on co-registered baseline and post-chemotherapy maps. DTI changes were compared with modifications of tumour area and volume [according to Response Assessment in Neuro-Oncology (RANO) criteria], and seizure response. After three cycles of TMZ, 20/21 patients were stable according to RANO criteria, but DTI changes were observed in all patients (Wilcoxon test, P ≤ 0.03). After six cycles, DTI changes were more pronounced (P ≤ 0.005). Seventy-five percent of patients had early seizure response with significant improvement of DTI values, maintaining stability on FLAIR. Early changes of the 25th percentiles of p and MD predicted final volume change (R{sup 2} = 0.614 and 0.561, P < 0.0005, respectively). TMZ-related changes were located mainly at tumour borders on p and MD fDMs. DTI-based histogram and fDM analyses are useful techniques to evaluate the early effects of TMZ chemotherapy in LGG patients. (orig.)

  8. The Development and Production of a Functionally Graded Composite for Pb-Bi Service.Final report

    International Nuclear Information System (INIS)

    A material that resists lead-bismuth eutectic (LBE) attack and retains its strength at 700 C would be an enabling technology for LBE-cooled reactors. No single alloy currently exists that can economically meet the required performance criteria of high strength and corrosion resistance. A Functionally Graded Composite (FGC) was developed with layers engineered to perform these functions. F91 was chosen as the structural layer of the composite for its strength and radiation resistance. Fe-12Cr-2Si, an alloy developed from previous work in the Fe-Cr-Si system, was chosen as the corrosion-resistant cladding layer because of its chemical similarity to F91 and its superior corrosion resistance in both oxidizing and reducing environments. Fe-12Cr-2Si experienced minimal corrosion due to its self-passivation in oxidizing and reducing environments. Extrapolated corrosion rates are below one micron per year at 700 C. Corrosion of F91 was faster, but predictable and manageable. Diffusion studies showed that 17 microns of the cladding layer will be diffusionally diluted during the three year life of fuel cladding. 33 microns must be accounted for during the sixty year life of coolant piping. 5 cm coolant piping and 6.35 mm fuel cladding preforms were produced on a commercial scale by weld-overlaying Fe-12Cr-2Si onto F91 billets and co-extruding them. An ASME certified weld was performed followed by the prescribed quench-and-tempering heat treatment for F91. A minimal heat affected zone was observed, demonstrating field weldability. Finally, corrosion tests were performed on the fabricated FGC at 700 C after completely breaching the cladding in a small area to induce galvanic corrosion at the interface. None was observed. This FGC has significant impacts on LBE reactor design. The increases in outlet temperature and coolant velocity allow a large increase in power density, leading to either a smaller core for the same power rating or more power output for the same size core

  9. The non-local theory solution of a Griffith crack in functionally graded materials subjected to the harmonic anti-plane shear waves

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In this paper, the dynamic stress field near crack tips in the functionally graded materials subjected to the harmonic anti-plane shear stress waves was investi- gated by means of the non-local theory. The traditional concepts of the non-local theory were extended to solve the fracture problem of functionally graded materials. To make the analysis tractable, it was assumed that the material properties vary exponentially with coordinate parallel to the crack. By use of the Fourier transform, the problem can be solved with the help of a pair of dual integral equations, in which the unknown variable was the displacement on the crack surfaces. To solve the dual integral equations, the displacement on the crack surfaces was expanded in a series of Jacobi polynomials. Unlike the classical elasticity solutions, it is found that no stress singularities are present at crack tips. The non-local elastic solutions yield a finite hoop stress at crack tips, thus allowing us to use the maximum stress as a fracture criterion. The magnitude of the finite dynamic stress field depends on the crack length, the parameter describing the functionally graded materials, the circular frequency of the incident waves and the lattice parameter of materials.

  10. The non-local theory solution of a Griffith crack in functionally graded materials subjected to the harmonic anti-plane shear waves

    Institute of Scientific and Technical Information of China (English)

    ZHANG PeiWei; ZHOU ZhenGong; WU LinZhi

    2007-01-01

    In this paper, the dynamic stress field near crack tips in the functionally graded materials subjected to the harmonic anti-plane shear stress waves was investigated by means of the non-local theory. The traditional concepts of the non-local theory were extended to solve the fracture problem of functionally graded materials.To make the analysis tractable, it was assumed that the material properties vary exponentially with coordinate parallel to the crack. By use of the Fourier transform,the problem can be solved with the help of a pair of dual integral equations, in which the unknown variable was the displacement on the crack surfaces. To solve the dual integral equations, the displacement on the crack surfaces was expanded in a series of Jacobi polynomials. Unlike the classical elasticity solutions, it is found that no stress singularities are present at crack tips. The non-local elastic solutions yield a finite hoop stress at crack tips, thus allowing us to use the maximum stress as a fracture criterion. The magnitude of the finite dynamic stress field depends on the crack length, the parameter describing the functionally graded materials, the circular frequency of the incident waves and the lattice parameter of materials.

  11. [The role of functional status and recursive partition analysis (RPA) classes for the choice of fractionation regimen in patients with high-grade gliomas].

    Science.gov (United States)

    Izmaĭlov, T R; Pan'shin, G A; Datsenko, P V

    2012-01-01

    The treatment results of 396 patients with morphologically verified grade 3-4 malignant brain tumors receiving conventional irradiation regimen and irradiation by medium-sized fractions were analyzed to form institutional guidelines.The standard mode of fractionation with a single dose of 2 Gy and total focal dose (TFD) of 60 Gy is appropriate for patients with initial Karnofsky status of 60-100% and Recursive Partition Analysis (RPA) class I-III. TFD increase to 60-62 Gy in grade 4 gliomas and 54-56 Gy in grade 3 gliomas grants a significant improve in overall survival. An increase of a single irradiation fraction to 3 Gy may be used for patients with initially low functional status (Karnofsky 30-50%) and RPA classes IV-VI. In these cases it is advisable to use the TFD of 45 Gy or more (TFD of equivalent regimen with a dose greater than 54 Gy). The mentioned fractionation regimens could be recommended for the use in clinical practice to improve the results of high-grade gliomas treatment. PMID:22888653

  12. Effect of functionally graded material (FGM) layers on the residual stress of polytypoidally joined Si3N4-Al2O3

    International Nuclear Information System (INIS)

    A unique approach introducing sialon polytypoids as a functionally graded material (FGM) bonding has been used to join silicon nitride and alumina. The various multilayered FGM samples ranging from 3 to 20 layers were sintered to fabricate a crack-free joining of heterogeneous ceramics. To calculate thermal stresses for the various multilayered FGM samples, the finite element analysis program (FEAP) was used. These analyses results matched experimental results and showed why some samples had large residual stresses that resulted in fracture. Moreover, the electron probe X-ray microanalysis (EPMA) from a crack-free FGM sample had a smooth concentration profile, which verifies the interface diffusion during sintering at each graded layer and confirms a successful joining

  13. Functional variables associated with the clinical grade of dyspnoea in coal miners with pneumoconiosis and mild bronchial obstruction

    Energy Technology Data Exchange (ETDEWEB)

    Bauer, T.T.; Schultze-Werninghaus, G.; Kollmeier, J.; Weber, A.; Eibel, R.; Lemke, B.; Schmidt, E.W. [Berufsgenossen Kliniken Bergmannsheil, Bochum (Germany)

    2001-12-01

    Dyspnoea is a common symptom in coal miners with pneumoconiosis. Among others, gas exchange disturbances due to airway obstruction or mismatch between ventilation and perfusion may be underlying mechanisms. The validation of dyspnoea by the degree of airway obstruction is controversial, because the extent of airway obstruction often does not correlate with the clinical grade of breathlessness. The association was investigated between breathlessness (self reported, on a six point scale) and indices of submaximal spiroergometry in 66 coal workers with radiographically confirmed pneumoconiosis. The clinical degree of breathlessness was independently associated with minute ventilation/oxygen consumption ratio and smoking in a multiple linear regression analysis. It is concluded that the given minute ventilation/oxygen consumption ratio as a measurement of mismatch between ventilation and perfusion predicted the clinical grade of breathlessness better than measurements of bronchial obstruction at rest in coal workers with pneumoconiosis.

  14. Optimal Grading

    OpenAIRE

    Robertas Zubrickas

    2010-01-01

    Assuming that teachers are concerned with human capital formation and students - with ability signaling, in this paper we model a teacher-student relationship as an agency problem with conflicting interests. In our model, the teacher elicits effort from the student rewarding for it with a grade, the utility of which to the student is an ability signal inferred by the job market. In the event that the job market does not observe individual teachers' grading practice, teachers find grades as co...

  15. Three-dimensional analytical solution for a transversely isotropic functionally graded piezoelectric circular plate subject to a uniform electric potential difference

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    This paper studies the problem of a functionally graded piezoelectric circular plate subjected to a uniform electric potential difference between the upper and lower surfaces. By assuming the generalized displacements in appropriate forms,five differential equations governing the generalized displacement functions are derived from the equilibrium equations. These displacement functions are then obtained in an explicit form,which still involve four undetermined integral constants,through a step-by-step integration which properly incorporates the boundary conditions at the upper and lower surfaces. The boundary conditions at the cylindrical surface are then used to determine the integral constants. Hence,three-dimen sional analytical solutions for electrically loaded functionally graded piezoelectric circular plates with free or simply-supported edge are completely determined. These solutions can account for an arbitrary material variation along the thickness,and thus can be readily degenerated into those for a homogenous plate. A numerical example is finally given to show the validity of the analysis,and the effect of material inhomogeneity on the elastic and electric fields is discussed.

  16. Semi-analytical solution for three-dimensional transient response of functionally graded annular plate on a two parameter viscoelastic foundation

    Science.gov (United States)

    Liang, Xu; Wang, Zhenyu; Wang, Lizhong; Liu, Guohua

    2014-06-01

    The three-dimensional transient analysis of functionally graded annular plates with arbitrary boundary conditions is carried out in this paper. The material properties of the FGM plate are assumed to vary smoothly in an exponential law along the thickness direction. The plate is assumed to rest on a two parameter viscoelastic foundation. A semi-analytical method, which integrates the state space method (SSM), Laplace transform and its inversion, as well as the one-dimensional differential quadrature method (DQM), is proposed to obtain the transient response of the plate. The state space method is used to obtain the analytical solution in the thickness direction. The differential quadrature method is employed to approximate the solution in the radial direction. The Laplace transform and the numerical inversion are used to obtain the solution in time domain. Numerical results show a good agreement between the response histories obtained by the present method and finite element method. The effects of the boundary conditions at the edges, the material graded index, the Winkler and shearing layer elastic coefficients, and the damping coefficient are studied. Numerical examples show that the peak response decreases as the material graded index, the Winkler and shearing layer elastic coefficients, and the damping coefficient increase. The results obtained in this paper can serve as benchmark data in further research.

  17. High-Grade Articular, Bursal, and Intratendinous Partial-Thickness Rotator Cuff Tears: A Retrospective Study Comparing Functional Outcomes After Completion and Repair.

    Science.gov (United States)

    Donohue, Nicholas K; Nickel, Brian T; Grindel, Steven I

    2016-01-01

    We conducted a study to assess the impact of tear location on functional outcomes in high-grade partial-thickness rotator cuff tears (PTRCTs) after arthroscopic completion and repair. Retrospectively, we evaluated the preoperative and postoperative findings of 60 patients who underwent arthroscopic completion and repair of Ellman grade 3 partial-thickness tears of the supraspinatus. The 60 patients were grouped by tear subtype (20 articular, 20 bursal, 20 intratendinous) as identified by preoperative imaging and confirmed at time of surgery. After surgery, the 3 subtypes showed similar significant (P < .001) improvements in American Shoulder and Elbow Surgeons scores (articular, 46.9, 85.1; bursal, 44.3, 80.3; intratendinous, 43.6, 86.1), Constant scores (articular, 54.3, 79.4; bursal, 49.9, 75.0; intratendinous, 56.8, 80.9), and visual analog scale scores (articular, 5.1, 1.2; bursal, 5.8, 1.6; intratendinous, 6.0, 1.2). Our study findings validate use of the current algorithm for Ellman grade 3 PTRCTs of the supraspinatus and advocate their completion and repair, regardless of tear location. PMID:27552462

  18. Microstructure and property of a functionally graded aluminum silicon alloy fabricated by semi-solid backward extrusion process

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Kai [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Yu, Hao, E-mail: yhzhmr@126.com [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Liu, Jun-you [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Li, Yan-xia [Department of Materials, North China Institute of Aerospace Engineering, Langfang 065000 (China); Liu, Jian; Zhang, Jia-liang [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China)

    2015-01-29

    In this paper, the microstructure and mechanical property of a graded aluminum silicon alloy were investigated and a new preparation method for the graded material was proposed. The cup-shaped sample was fabricated by the backward extrusion process during the semi-solid state of A390 cast alloy. Characteristics and distribution of the primary particles were assessed by the optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectrum (EDS) and image analyzer software. The results showed that the content of primary Si gradually decreased from the bottom region to the upper region. The hardness and wear rate of the samples were measured to evaluate the variation in the mechanical properties corresponding to the variation in microstructure. The hardness values and wear resistance along the axis of the cup-shaped sample gradually increased from the upper region to the bottom region and from the inner region to the outer layer, respectively. The maximum average hardness value is 138.7 HB. The observations of fracture surface were analyzed by scanning electron microscopy to understand the fracture mechanism. The results also indicated that the ultimate tensile strength (UTS) of the graded material after T6 treatment are 275 MPa, increases 32.3% compared to the original backward extrusion alloy. Optical microscopy and electron probe micro-analyzer were used to study the distribution of elements and the microstructure of different intermetallic phases formed. Electron microprobe analysis (EMPA) results showed that the content of the prominent elements (Cu, Fe, Mg) in the upper region was higher than for the bottom part of the cup-shaped specimens.

  19. Microstructure and property of a functionally graded aluminum silicon alloy fabricated by semi-solid backward extrusion process

    International Nuclear Information System (INIS)

    In this paper, the microstructure and mechanical property of a graded aluminum silicon alloy were investigated and a new preparation method for the graded material was proposed. The cup-shaped sample was fabricated by the backward extrusion process during the semi-solid state of A390 cast alloy. Characteristics and distribution of the primary particles were assessed by the optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectrum (EDS) and image analyzer software. The results showed that the content of primary Si gradually decreased from the bottom region to the upper region. The hardness and wear rate of the samples were measured to evaluate the variation in the mechanical properties corresponding to the variation in microstructure. The hardness values and wear resistance along the axis of the cup-shaped sample gradually increased from the upper region to the bottom region and from the inner region to the outer layer, respectively. The maximum average hardness value is 138.7 HB. The observations of fracture surface were analyzed by scanning electron microscopy to understand the fracture mechanism. The results also indicated that the ultimate tensile strength (UTS) of the graded material after T6 treatment are 275 MPa, increases 32.3% compared to the original backward extrusion alloy. Optical microscopy and electron probe micro-analyzer were used to study the distribution of elements and the microstructure of different intermetallic phases formed. Electron microprobe analysis (EMPA) results showed that the content of the prominent elements (Cu, Fe, Mg) in the upper region was higher than for the bottom part of the cup-shaped specimens

  20. A seven-year storage report of good manufacturing practice-grade naked plasmid DNA: stability, topology, and in vitro/in vivo functional analysis

    OpenAIRE

    Walther, W.; Schmeer, M.; Kobelt, D.; Baier, R.; Harder , A.; Walhorn, V.; Anselmetti, D; Aumann, J; Fichtner, I.; Schleef, M

    2013-01-01

    The great interest of naked plasmid DNA in gene therapy studies is reflected by the fact, that it is currently used in 18% of all gene therapy trials. Therefore, validation of topology and functionality of DNA resulting from its long-term stability is an essential requirement for safe and effective gene transfer. To this aim, we analyzed the stability of GMP-grade pCMV-{beta} reporter plasmid DNA by capillary gel electrophoresis, agarose gel electrophoresis and atomic force microscopy. The pl...

  1. Mechanical analyses of pipeline repair and reinforcement with use of composite functionally graded materials; Analise mecanica de reforco de dutos submarinos com materiais compositos com gradacao funcional

    Energy Technology Data Exchange (ETDEWEB)

    Queiroz, Marcos S.M. [Sondotecnica Engenharia de Solos S.A., Rio de Janeiro, RJ (Brazil); Roehl, Deane de Mesquita [Pontificia Universidade Catolica do Rio de Janeiro (PUC-Rio), RJ (Brazil)

    2008-07-01

    This work presents a methodology for design of stiffener sleeve constituted by functionally graded composite materials in offshore pipelines located in extreme-deep waters, where high mechanical resistance allied to an efficient system of thermal isolation is necessary, in view of the excellent thermomechanical behavior of composites. For the case of FGMs, due to continuous variation in its featuring, is necessary to employ an adapted model, based on a model typically adopted for conventional composites (Rule of Mixture), as the model idealized by Tamura, Tomato e Ozawa, the TTO model. In this report, the influence of geometric and materials parameters in mechanical behavior of pipelines under propagating collapse is analyzed. (author)

  2. Optimized functionally graded La{sub 2}Zr{sub 2}O{sub 7}/8YSZ thermal barrier coatings fabricated by suspension plasma spraying

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Chaohui [Laboratory of Nano Surface Engineering, School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); College of Materials Science and Engineering, Qiqihar University, Qiqihar 161006 (China); Wang, You, E-mail: wangyou@hit.edu.cn [Laboratory of Nano Surface Engineering, School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Fan, Shan; You, Yuan [College of Materials Science and Engineering, Qiqihar University, Qiqihar 161006 (China); Wang, Liang [Key Laboratory of Inorganic Coating Materials, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 201899 (China); Yang, Changlong [College of Materials Science and Engineering, Qiqihar University, Qiqihar 161006 (China); Sun, Xiaoguang [National Engineering Research Center for High-speed EMU, CSR Qingdao Sifang Co. Ltd., Qingdao 266111 (China); Li, Xuewei [Laboratory of Nano Surface Engineering, School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China)

    2015-11-15

    In this paper, an optimized functionally graded coating (OFGC) was successfully fabricated by suspension plasma spraying (SPS) with feedstocks of the suspension of nanoparticles. La{sub 2}Zr{sub 2}O{sub 7}/8YSZ OFGC with gradual compositional variation along the through-thickness direction is proposed to mitigate spallation and crack formation owing to the high residual stresses caused by frequent thermal cycling for TBCs. The single ceramic layer coatings (SCLC) of LZ and double ceramic layer coatings (DCLC) of LZ/8YSZ were fabricated by SPS as comparison. The phase composition and microstructure of the SCLC, OFGC and DCLC were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and Energy Dispersive Spectrometer (EDS). Moreover, the thermal cycling tests were carried out to evaluate their thermal shock behavior. Changes in weight and morphology of specimens were analyzed during thermal cycling tests. The results showed that OFGC has extended lifetime compared with SCLC and DCLC. The failure of DCLC with clear interface between different ceramic layers occurred via delamination mode, as a result of crack initiation and propagation generated by thermal mismatch between LZ and 8YSZ. While the failure of OFGC occurred in thermally grown oxide (TGO) layers, indicating that the gradual compositional variation avoided thermal stress concentration in the top ceramic layers. - Highlights: • Optimized functionally graded coatings and double ceramic layer coatings were deposited by suspension plasma spray. • The graded area of OFGC is continuously changed from inner 8YSZ to outer La{sub 2}Zr{sub 2}O{sub 7} (LZ). • The OFGC shows a more extended thermal cycling life than the LZ SCLC and LZ/8YSZ DCLC. • Various failure mechanisms were proposed to explain thermal cycling behavior.

  3. Tables of phase functions, opacities, albedos, equilibrium temperatures, and radiative accelerations of dust grains in exoplanets

    CERN Document Server

    Budaj, Jan; Salmeron, Raquel; Hubeny, Ivan

    2015-01-01

    There has been growing observational evidence for the presence of condensates in the atmospheres and/or comet-like tails of extrasolar planets. As a result, systematic and homogeneous tables of dust properties are useful in order to facilitate further observational and theoretical studies. In this paper we present calculations and analysis of non-isotropic phase functions, asymmetry parameter (mean cosine of the scattering angle), absorption and scattering opacities, single scattering albedos, equilibrium temperatures, and radiative accelerations of dust grains relevant for extrasolar planets. Our assumptions include spherical grain shape, Deirmendjian particle size distribution, and Mie theory. We consider several species: corundum/alumina, iron, olivines with 0% and 50% iron content, pyroxenes with 0%, 20% and 60% iron content, carbon at two different temperatures, water ice, liquid water, and ammonia. The presented tables cover the wavelength range of 0.2 to 500 micron and modal particle radii from 0.01 mi...

  4. Classical entropy generation analysis in cooled homogenous and functionally graded material slabs with variation of internal heat generation with temperature, and convective–radiative boundary conditions

    International Nuclear Information System (INIS)

    This article investigates the classical entropy generation in cooled slabs. Two types of materials are assumed for the slab: homogeneous material and FGM (functionally graded material). For the homogeneous material, the thermal conductivity is assumed to be a linear function of temperature, while for the FGM slab the thermal conductivity is modeled to vary in accordance with the rule of mixtures. The boundary conditions are assumed to be convective and radiative concurrently, and the internal heat generation of the slab is a linear function of temperature. Using the DTM (differential transformation method) and resultant temperature fields from the DTM, the local and total entropy generation rates within slabs are derived. The effects of physically applicable parameters such as the thermal conductivity parameter for the homogenous slab, β, the thermal conductivity parameter for the FGM slab, γ, gradient index, j, internal heat generation parameter, Q, Biot number at the right side, Nc2, conduction–radiation parameter, Nr2, dimensionless convection sink temperature, δ, and dimensionless radiation sink temperature, η, on the local and total entropy generation rates are illustrated and explained. The results demonstrate that considering temperature- or coordinate-dependent thermal conductivity and radiation heat transfer at both sides of the slab have great effects on the entropy generation. - Highlights: • The paper investigates entropy generation in a slab due to heat generation and convective–radiative boundary conditions. • Both homogeneous material and FGM (functionally graded material) were considered. • The calculations are carried out using the differential transformation method which is a well-tested analytical technique

  5. Development of rheological characterization and twin-screw extrusion/spiral winding processing methods for functionally-graded tissue engineering scaffolds and characterization of cell/biomaterial interactions

    Science.gov (United States)

    Ozkan, Seher

    Tissue engineering involves the fabrication of biodegradable scaffolds, on which various types of cells are grown, to provide tissue constructs for tissue repair/regeneration. Native tissues have complex structures, with functions and properties changing spatially and temporally, and require special tailoring of tissue engineering scaffolds to allow mimicking of their complex elegance. The understanding of the rheological behavior of the biodegradable polymer and the thermo-mechanical history that the polymer experiences during processing is critical in fabricating scaffolds with appropriate microstructural distributions. This study has first focused on the rheological material functions of various gel-like fluids including biofluids and hydrogels, which can emulate the viscoelastic behavior of biofluids. Viscoplasticity and wall slip were recognized as key attributes of such systems. Furthermore, a new technology base involving twin-screw extrusion/spiral winding (TSESW) process was developed for the shaping of functionally-graded scaffolds. This novel scaffold fabrication technology was applied to the development of polycaprolactone (PCL) scaffolds, incorporated with tricalcium phosphate nanoparticles and various porogens in graded fashion. The protein encapsulation and controlled release capabilities of the TSESW process was also demonstrated by dispersing bovine serum albumin (BSA) protein into the PCL matrix. Effects of processing conditions and porosity distributions on compressive properties, surface topography, encapsulation efficiency, release profiles and the secondary structure of BSA were investigated. The PCL scaffolds were determined to be biocompatible, with the proliferation rates of human fetal osteoblast cells (hFOB) increasing with increasing porosity and decreasing concentration of TCP. BSA proteins were determined to be denatured to a greater extent with melt extrusion in the 80-100°C range (in comparison to wet extrusion using organic

  6. Changes in the aromatic profile of espresso coffee as a function of the grinding grade and extraction time: a study by the electronic nose system.

    Science.gov (United States)

    Severini, C; Ricci, I; Marone, M; Derossi, A; De Pilli, T

    2015-03-01

    The changes in chemical attributes and aromatic profile of espresso coffee (EC) were studied taking into account the extraction time and grinding level as independent variables. Particularly, using an electronic nose system, the changes of the global aromatic profile of EC were highlighted. The results shown as the major amounts of organic acids, solids, and caffeine were extracted in the first 8 s of percolation. The grinding grade significantly affected the quality of EC probably as an effect of the particle size distribution and the percolation pathways of water through the coffee cake. The use of an electronic nose system allowed us to discriminate the fractions of the brew as a function of the percolation time and also the regular coffee obtained from different grinding grades. Particularly, the aromatic profile of a regular coffee (25 mL) was significantly affected by the grinding level of the coffee grounds and percolation time, which are two variables under the control of the bar operator. PMID:25665600

  7. Degradation of functional group of cation exchange nuclear grade resin loaded with different metal ions due to gamma radiation exposure

    International Nuclear Information System (INIS)

    Ion exchange resins undergo degradation due to ionizing radiation while processing the radioactive water treatment. During this process, the cation resin used for this purpose gets loaded with various metal ions and presence of different metal ions in the resin may result into different degradation behaviors of functional group(s) (lowering the capacity). This work deals with the effect of few cations such as H+, Li+, Na+, Cs+ and Cu2+ on the degradation behavior of functional groups of strong acid cation resins exposed in different dose of 60Co gamma ray. Degradations were estimated by measuring the sulphate ion concentration in leach solution. (author)

  8. The properties of thickness-twist (TT) wave modes in a rotated Y-cut quartz plate with a functionally graded material top layer.

    Science.gov (United States)

    Wang, Bin; Qian, Zhenghua; Li, Nian; Sarraf, Hamid

    2016-01-01

    We propose the use of thickness-twist (TT) wave modes of an AT-cut quartz crystal plate resonator for measurement of material parameters, such as stiffness, density and material gradient, of a functionally graded material (FGM) layer on its surface, whose material property varies exponentially in thickness direction. A theoretical analysis of dispersion relations for TT waves is presented using Mindlin's plate theory, with displacement mode shapes plotted, and the existence of face-shear (FS) wave modes discussed. Through numerical examples, the effects of material parameters (stiffness, density and material gradient) on dispersion curves, cutoff frequencies and mode shapes are thoroughly examined, which can act as a theoretical reference for measurements of unknown properties of FGM layer. PMID:26254981

  9. High heat flux testing of B4C/Cu and SiC/Cu functionally graded materials simulated by laser and electron beam

    International Nuclear Information System (INIS)

    B4C, SiC and C, Cu functionally graded-materials (FGMs) have been developed by plasma spraying and hot pressing. Their high-heat flux properties have been investigated by high energy laser and electron beam for the simulation of plasma disruption process of the future fusion reactors. And a study on eroded products of B4C/Cu FGM under transient thermal load of electron beam was performed. In the experiment, SEM and EDS analysis indicated that B4C and SiC were decomposed, carbon was preferentially evaporated under high thermal load, and a part of Si and Cu were melted, in addition, the splash of melted metal and the particle emission of brittle destruction were also found. Different erosive behaviors of carbon-based materials (CBMs) caused by laser and electron beam were also discussed

  10. Phenotypic and functional characterization of clinical grade dendritic cells generated from patients with advanced breast cancer for therapeutic vaccination

    DEFF Research Database (Denmark)

    Pedersen, Anders Elm; Thorn, M; Gad, M;

    2005-01-01

    utilizing granulocyte macrophage colony-stimulating factor and rh-interleukin-4 (IL-4) and used for cancer immunotherapy. In this study, we tested the effect of various maturation cocktails and performed a comparative evaluation of the DC phenotype and functional characteristics. Polyriboinosinic...

  11. Study on the preparation of the SiCp/Al-20Si-3Cu functionally graded material using spray deposition

    International Nuclear Information System (INIS)

    Research highlights: → The SiCp/Al-20Si-3Cu functionally gradient material (FGM) was successfully prepared via the spray deposition technique. → The SiCp/Al-20Si-3Cu functionally gradient material (FGM) was successfully prepared via the spray deposition technique. → In the experimental setup, the novel devices play an important role in adjusting the output of SiCp to prepare the FGM. → The experiment results reveal that the SiCp weight fraction of the as-deposited preform from the top to the bottom ranges almost continuously from 0% to 30%. → The fraction of SiC particles has no obvious influence on the phase constitutions of the SiCp/Al-20Si-3Cu FGM. - Abstract: The SiCp/Al-20Si-3Cu functionally gradient material (FGMs) was successfully prepared via the spray deposition technique accompanied with an automatic control system. The results reveal that the SiCp weight fraction of the as-deposited preform from the top to the bottom ranges almost continuously from 0% to 30%. The part with the higher SiCp weight fraction exhibits a relatively smaller density than that with the lower SiCp weight fraction. However, the microhardness and the porosity increase with the increasing SiCp weight fraction in the as-deposited preform. The X-ray diffraction results exhibit that the secondary phases in the regions with the different amount of SiC particles are the same such as Al2Cu and AlCuMg. The spray deposition technology is promising to produce a wide range of other FGMs.

  12. Study on the preparation of the SiCp/Al-20Si-3Cu functionally graded material using spray deposition

    Energy Technology Data Exchange (ETDEWEB)

    Su, B. [College of Materials Science and Engineering, Hunan University, 410082 Changsha (China); Yan, H.G., E-mail: subindier2008@126.com [College of Materials Science and Engineering, Hunan University, 410082 Changsha (China); Chen, G.; Shi, J.L.; Chen, J.H.; Zeng, P.L. [College of Materials Science and Engineering, Hunan University, 410082 Changsha (China)

    2010-09-25

    Research highlights: {yields} The SiCp/Al-20Si-3Cu functionally gradient material (FGM) was successfully prepared via the spray deposition technique. {yields} The SiCp/Al-20Si-3Cu functionally gradient material (FGM) was successfully prepared via the spray deposition technique. {yields} In the experimental setup, the novel devices play an important role in adjusting the output of SiCp to prepare the FGM. {yields} The experiment results reveal that the SiCp weight fraction of the as-deposited preform from the top to the bottom ranges almost continuously from 0% to 30%. {yields} The fraction of SiC particles has no obvious influence on the phase constitutions of the SiCp/Al-20Si-3Cu FGM. - Abstract: The SiCp/Al-20Si-3Cu functionally gradient material (FGMs) was successfully prepared via the spray deposition technique accompanied with an automatic control system. The results reveal that the SiCp weight fraction of the as-deposited preform from the top to the bottom ranges almost continuously from 0% to 30%. The part with the higher SiCp weight fraction exhibits a relatively smaller density than that with the lower SiCp weight fraction. However, the microhardness and the porosity increase with the increasing SiCp weight fraction in the as-deposited preform. The X-ray diffraction results exhibit that the secondary phases in the regions with the different amount of SiC particles are the same such as Al{sub 2}Cu and AlCuMg. The spray deposition technology is promising to produce a wide range of other FGMs.

  13. 低级别胶质瘤患者脑功能区的可塑性%Brain Functional Areas Plasticity of Patients with Low Grade Glioma

    Institute of Scientific and Technical Information of China (English)

    郑刚

    2013-01-01

    Low grade glioma( LGG ) is a common disease in neurosurgery, it often invades brain functional regions with infiltrative growth. Patients with LGG always have no neurological deficits when they are discovered. Nowadays operation is still the first-line treatment, how to resect the tumor in maximum extent while preserving neurological function is still an challenge to neurosurgeons. In recent years,it's found much plasticity of brain functional areas exists in patients with LGG, and the reorganization of functional regions have different models. According to this LGG's feature,the operative strategy can be adjusted based on different reorganization models of functional regions in different patients, to increase the extent of resection and decrease the morbidity.%低级别胶质瘤是神经外科的常见疾病,其呈浸润性生长,多累及脑功能区,发病时多无神经功能障碍.目前手术切除仍是首选的治疗方案,如何在最大程度地切除肿瘤的同时保留神经功能,对神经外科医师来说仍是一项挑战.近年来发现,在低级别胶质瘤患者中,脑功能区存在较大的可塑性,并且存在着不同的功能区重构模式.对低级别胶质瘤的这种特性的研究和利用,可针对不同患者脑功能重构的不同模式调整相应的手术策略,从而提高手术切除率,降低病残率.

  14. Effects of WC Particle Size and Co Content on the Graded Structure in Functionally Gradient WC-Co Composites

    Directory of Open Access Journals (Sweden)

    Yuan Yigao

    2016-01-01

    Full Text Available Functionally gradient WC-Co composites having a Co depleted surface zone and not comprising the h phase can be manufactured via carburizing process. During carburizing, besides carburizing process parameters, the microstructural parameters of WC-Co materials, such as WC grain size and Co content, also have significant influences on the formation of Co gradient structure. In this study, the effects of WC particle size and Co content on the gradient structure within gradient hardmetals have been studied, based on a series of carburizing experiments of WC-Co materials with different WC particle sizes and cobalt contents. The results show that both the thickness and the amplitude of the gradients within gradient WC-Co materials increase with increasing initial WC particle size and Co content of WC-Co alloys. The reason for this finding is discussed.

  15. Graded effects of unregulated smooth muscle myosin on intestinal architecture, intestinal motility and vascular function in zebrafish.

    Science.gov (United States)

    Abrams, Joshua; Einhorn, Zev; Seiler, Christoph; Zong, Alan B; Sweeney, H Lee; Pack, Michael

    2016-05-01

    Smooth muscle contraction is controlled by the regulated activity of the myosin heavy chain ATPase (Myh11). Myh11 mutations have diverse effects in the cardiovascular, digestive and genitourinary systems in humans and animal models. We previously reported a recessive missense mutation, meltdown (mlt), which converts a highly conserved tryptophan to arginine (W512R) in the rigid relay loop of zebrafish Myh11. The mlt mutation disrupts myosin regulation and non-autonomously induces invasive expansion of the intestinal epithelium. Here, we report two newly identified missense mutations in the switch-1 (S237Y) and coil-coiled (L1287M) domains of Myh11 that fail to complement mlt Cell invasion was not detected in either homozygous mutant but could be induced by oxidative stress and activation of oncogenic signaling pathways. The smooth muscle defect imparted by the mlt and S237Y mutations also delayed intestinal transit, and altered vascular function, as measured by blood flow in the dorsal aorta. The cell-invasion phenotype induced by the three myh11 mutants correlated with the degree of myosin deregulation. These findings suggest that the vertebrate intestinal epithelium is tuned to the physical state of the surrounding stroma, which, in turn, governs its response to physiologic and pathologic stimuli. Genetic variants that alter the regulation of smooth muscle myosin might be risk factors for diseases affecting the intestine, vasculature, and other tissues that contain smooth muscle or contractile cells that express smooth muscle proteins, particularly in the setting of redox stress. PMID:26893369

  16. Honest Grading, Grade Inflation and Reputation

    OpenAIRE

    Ehlers, Tim; Schwager, Robert

    2012-01-01

    When grades lose their informative value because the percentage of students receiving the best grade rises without any corresponding increase in ability, this is called grade inflation. Conventional wisdom says that such grade inflation is unavoidable since it is essentially costless to award good grades. In this paper, we point out an effect driving into the opposite direction: Grade inflation is not actually costless, since it has an impact on future cohorts of graduates, or, put differentl...

  17. TRANSFORAMINAL L U MBAR INTERBODY FUSION IN LOW GRADE COMBINED LYTIC AND DEGENERATIVE SPONDYLOLIDTHESIS : FUNCTIONAL OUTCOME OF 21 CASES

    Directory of Open Access Journals (Sweden)

    Suresh

    2015-10-01

    Full Text Available BACKGROUND: Spondylolisthesis is a heterogenous disorder characterised by subluxation of a vertebral body in sagittal plane occuring frequently at l4 - 5 and l5 - S1commonest being isthmic and degenerative variety. While majority are asymptomatic, a subset do produce pain with neurology. Complete decompression of roots is essential, as is the need for solid stabi lization. Several fusion techniques were reported in literature like PLF, TLIF, PLF, ALIF On theoretical grounds, TLIF has been suggested to be safe and result in an improved outcome compared to other techniques. Data to support this view, are lacking. M ETHODS: A total of 21 patients (age range, 27 - 62 years with adult isthmic and degenerative spondylolisthesis were operated. There were 8 males and 13 females with mean age of 46.8 pre - op and 2 - year follow - up, pain (VAS and functional disability were quan tified by Oswestry Disability Index (ODI.Radiological union assessed with xrays by Brantigen and Steffee criteria. The global outcome was excellent in 90%.and 92% fusion. 2 patients presented motor deficit which did not recover. RESULTS: The follow - up was for 2 years. The mean VAS score for low back pain improved from 7.0 preoperatively to 2.1, as did the mean VAS score for leg pain from 6.7 to 1.4 and the mean ODI from 59.5% to 11.3%. CONCLUSION: TLIF does affect the 2 - year outcome of surgical treatment of spondylolisthesis with decreased back pain and ODI’s, with advantages of minimal thecal retraction, restored segmental lordosis and preserved posterior tension band.

  18. Evaluation of the Early In Vivo Response of a Functionally Graded Macroporous Scaffold in an Osteochondral Defect in a Rabbit Model.

    Science.gov (United States)

    Barron, Valerie; Neary, Martin; Mohamed, Khalid Merghani Salid; Ansboro, Sharon; Shaw, Georgina; O'Malley, Grace; Rooney, Niall; Barry, Frank; Murphy, Mary

    2016-05-01

    Cartilage tissue engineering is a multifactorial problem requiring a wide range of material property requirements from provision of biological cues to facilitation of mechanical support in load-bearing diarthrodial joints. The study aim was to design, fabricate and characterize a template to promote endogenous cell recruitment for enhanced cartilage repair. A polylactic acid poly-ε-caprolactone (PLCL) support structure was fabricated using laser micromachining technology and thermal crimping to create a functionally-graded open pore network scaffold with a compressive modulus of 9.98 ± 1.41 MPa and a compressive stress at 50% strain of 8.59 ± 1.35 MPa. In parallel, rabbit mesenchymal stem cells were isolated and their growth characteristics, morphology and multipotency confirmed. Sterilization had no effect on construct chemical structure and cellular compatibility was confirmed. After four weeks implantation in an osteochondral defect in a rabbit model to assess biocompatibility, there was no evidence of inflammation or giant cells. Moreover, acellular constructs performed better than cell-seeded constructs with endogenous progenitor cells homing through microtunnels, differentiating to form neo-cartilage and strengthening integration with native tissue. These results suggest, albeit at an early stage of repair, that by modulating the architecture of a macroporous scaffold, pre-seeding with MSCs is not necessary for hyaline cartilage repair. PMID:26438451

  19. Improving Grading Consistency through Grade Lift Reporting

    Science.gov (United States)

    Millet, Ido

    2010-01-01

    We define Grade Lift as the difference between average class grade and average cumulative class GPA. This metric provides an assessment of how lenient the grading was for a given course. In 2006, we started providing faculty members individualized Grade Lift reports reflecting their position relative to an anonymously plotted school-wide…

  20. Mechanical and physical behavior of newly developed functionally graded materials and composites of stainless steel 316L with calcium silicate and hydroxyapatite.

    Science.gov (United States)

    Ataollahi Oshkour, Azim; Pramanik, Sumit; Mehrali, Mehdi; Yau, Yat Huang; Tarlochan, Faris; Abu Osman, Noor Azuan

    2015-09-01

    This study aimed to investigate the structural, physical and mechanical behavior of composites and functionally graded materials (FGMs) made of stainless steel (SS-316L)/hydroxyapatite (HA) and SS-316L/calcium silicate (CS) employing powder metallurgical solid state sintering. The structural analysis using X-ray diffraction showed that the sintering at high temperature led to the reaction between compounds of the SS-316L and HA, while SS-316L and CS remained intact during the sintering process in composites of SS-316L/CS. A dimensional expansion was found in the composites made of 40 and 50 wt% HA. The minimum shrinkage was emerged in 50 wt% CS composite, while the maximum shrinkage was revealed in samples with pure SS-316L, HA and CS. Compressive mechanical properties of SS-316L/HA decreased sharply with increasing of HA content up to 20 wt% and gradually with CS content up to 50 wt% for SS-316L/CS composites. The mechanical properties of the FGM of SS-316L/HA dropped with increase in temperature, while it was improved for the FGM of SS-316L/CS with temperature enhancement. It has been found that the FGMs emerged a better compressive mechanical properties compared to both the composite systems. Therefore, the SS-316L/CS composites and their FGMs have superior compressive mechanical properties to the SS-316L/HA composites and their FGMs and also the newly developed FGMs of SS-316L/CS with improved mechanical and enhanced gradation in physical and structural properties can potentially be utilized in the components with load-bearing application. PMID:26072197

  1. Exploring differential item functioning (DIF) with the Rasch model: A comparison of gender differences on eighth-grade science items in the United States and Spain

    Science.gov (United States)

    Calvert, Tasha

    Despite the attention that has been given to gender and science, boys continue to outperform girls in science achievement, particularly by the end of secondary school. Because it is unclear whether gender differences have narrowed over time (Leder, 1992; Willingham & Cole, 1997), it is important to continue a line of inquiry into the nature of gender differences, specifically at the international level. The purpose of this study was to investigate gender differences in science achievement across two countries: United States and Spain. A secondary purpose was to demonstrate an alternative method for exploring gender differences based on the many-faceted Rasch model (1980). A secondary analysis of the data from the Third International Mathematics and Science Study (TIMSS) was used to examine the relationship between gender DIF (differential item functioning) and item characteristics (item type, content, and performance expectation) across both countries. Nationally representative samples of eighth grade students in the United States and Spain who participated in TIMSS were analyzed to answer the research questions in this study. In both countries, girls showed an advantage over boys on life science items and most extended response items, whereas boys, by and large, had an advantage on earth science, physics, and chemistry items. However, even within areas that favored boys, such as physics, there were items that were differentially easier for girls. In general, patterns in gender differences were similar across both countries although there were a few differences between the countries on individual items. It was concluded that simply looking at mean differences does not provide an adequate understanding of the nature of gender differences in science achievement.

  2. Is the Sky Falling? Grade Inflation and the Signaling Power of Grades

    Science.gov (United States)

    Pattison, Evangeleen; Grodsky, Eric; Muller, Chandra

    2013-01-01

    Grades are the fundamental currency of our educational system; they signal academic achievement and noncognitive skills to parents, employers, postsecondary gatekeepers, and students themselves. Grade inflation compromises the signaling value of grades and undermines their capacity to achieve the functions for which they are intended. We challenge…

  3. In vitro assessment of Function Graded (FG artificial Hip joint stem in terms of bone/cement stresses: 3D Finite Element (FE study

    Directory of Open Access Journals (Sweden)

    Al-Jassir Fawzi F

    2013-01-01

    Full Text Available Abstract Background Stress shielding in the cemented hip prosthesis occurs due to the mismatching in the mechanical properties of metallic stem and bone. This mismatching in properties is considered as one of the main reasons for implant loosening. Therefore, a new stem material in orthopedic surgery is still required. In the present study, 3D finite element modeling is used for evaluating the artificial hip joint stem that is made of Function Graded (FG material in terms of joint stress distributions and stem length. Method 3D finite element models of different stems made of two types of FG materials and traditional stems made of Cobalt Chromium alloy (CoCrMo and Titanium alloy (Ti were developed using the ANSYS Code. The effects on the total artificial hip joint stresses (Shear stress and Von Mises stresses at bone cement, Von Mises stresses at bone and stem due to using the proposed FG materials stems were investigated. The effects on the total artificial hip joint system stresses due to using different stem lengths were investigated. Results Using FG stem (with low stiffness at stem distal end and high stiffness at its proximal end resulted in a significant reduction in shear stress at the bone cement/stem interface. Also, the Von Mises stresses at the bone cement and stem decrease significantly when using FG material instead of CoCrMo and Ti alloy. The stresses’ distribution along the bone cement length when using FG material was found to be more uniform along the whole bone cement compared with other stem materials. These more uniform stresses will help in the reduction of the artificial hip joint loosening rate and improve its short and long term performance. Conclusion FE results showed that using FG stem increases the resultant stresses at the femur bone (reduces stress shielding compared to metallic stem. The results showed that the stem length has significant effects on the resultant shear and Von Mises stresses at bone, stem and

  4. Cis-eQTL analysis and functional validation of candidate susceptibility genes for high-grade serous ovarian cancer

    DEFF Research Database (Denmark)

    Lawrenson, Kate; Li, Qiyuan; Kar, Siddhartha;

    2015-01-01

    Genome-wide association studies have reported 11 regions conferring risk of high-grade serous epithelial ovarian cancer (HGSOC). Expression quantitative trait locus (eQTL) analyses can identify candidate susceptibility genes at risk loci. Here we evaluate cis-eQTL associations at 47 regions assoc...

  5. AN EIGHTH GRADE ORTHOGRAPHY TEST

    Directory of Open Access Journals (Sweden)

    Саша С. Чорболоковић

    2013-12-01

    Full Text Available The paper examines an eighth grade orthography test with the aim of improving current methods in teaching orthography and encouraging the development of functional knowledge in elementary school students. Besides general considerations concerning the test in the context of teaching and all the elements connected with its preparation and implementation (clear rules and persistent adherence to rules, clear instructions for tasks, appropriate teacher instruction during classes, the paper also provides a description of a test model which can be used during a revision class of eight grade Serbian language orthography.

  6. Investigation on SiC/C Functionally Graded Plasma-facing Material%面向等离子体SiC/C功能梯度材料的研究

    Institute of Scientific and Technical Information of China (English)

    武安华; 葛昌纯; 李江涛; 曹文斌

    2002-01-01

    用热压制备了SiC/C功能梯度材料(Functionally Graded Materials, FGM).评估了SiC/C FGM的微观组织和物理性能.其中SiC/C FGM的耐等离子体冲刷行为显示了它们在核聚变实验装置中作为面向等离子体材料的良好应用前景.

  7. Corrosion behaviour of Al/Al3Ti and Al/Al3Zr functionally graded materials produced by centrifugal solid-particle method: Influence of the intermetallics volume fraction

    OpenAIRE

    Ferreira, S. C.; L. A. Rocha; Ariza, E.; Sequeira, P. D.; WATANABE, Yoshimi; Fernandes, J. C. S.

    2011-01-01

    Intermetallic particles, Al3Ti and Al3Zr were formed in Al–5mass%Ti and Al–5mass%Zr alloys, respectively, by centrifugal casting, in order to create functionally graded materials (FGMs). At present, no information is available on the influence of the amount of intermetallics on the electrochemical properties of these alloys. In this paper, the corrosion resistance of Al/Al3Ti and Al/Al3Zr FGMs was investigated by open-circuit measurements, potentiodynamic polarization and electrochemical ...

  8. Gleason grading system

    Science.gov (United States)

    ... medlineplus.gov/ency/patientinstructions/000920.htm Gleason grading system To use the sharing features on this page, ... score of between 5 and 7. Gleason Grading System Sometimes, it can be hard to predict how ...

  9. Preparation and Dielectric Properties of (BaxSr1-xTiO3/Mg2TiO4 Composite Ceramics withA Functionally Graded Structure

    Directory of Open Access Journals (Sweden)

    LI Jun, WANG Xu-Sheng, CHAI Xiao Na, LIU Peng

    2014-01-01

    Full Text Available (BaxSr1-xTiO3/Mg2TiO4 composite ceramics with a constituent graded structure were prepared by a solid-state reaction method. Their microstructure and dielectric properties were analyzed by X-Ray diffraction (XRD, Scanning Electron Microscope (SEM, Energy Dispersive Spectroscope (EDS and dielectric property measurements. The results show that the samples sintered at 1375°C for 3 h are a composite phase of perovskite and spinel structure with a Ba/Sr ratio composition gradient. Compared with the composite samples with a fixed Ba/Sr ratio, the graded samples possess higher tunability and better temperature stability of dielectric properties. At room temperature (20°C, the tunability of a typical sample is 21.9% under an external DC field of 2 kV/mm, and it maintains a high value of 9.3% at high temperature of 60°C. The improvement of temperature stability is due to the difference in Curie temperature for different layers in gradient (Ba,SrTiO3. Meanwhile, the introduction of the composition gradient in this material helps us to obtain a wide temperature application range for the related device.

  10. New similarity search based glioma grading

    International Nuclear Information System (INIS)

    MR-based differentiation between low- and high-grade gliomas is predominately based on contrast-enhanced T1-weighted images (CE-T1w). However, functional MR sequences as perfusion- and diffusion-weighted sequences can provide additional information on tumor grade. Here, we tested the potential of a recently developed similarity search based method that integrates information of CE-T1w and perfusion maps for non-invasive MR-based glioma grading. We prospectively included 37 untreated glioma patients (23 grade I/II, 14 grade III gliomas), in whom 3T MRI with FLAIR, pre- and post-contrast T1-weighted, and perfusion sequences was performed. Cerebral blood volume, cerebral blood flow, and mean transit time maps as well as CE-T1w images were used as input for the similarity search. Data sets were preprocessed and converted to four-dimensional Gaussian Mixture Models that considered correlations between the different MR sequences. For each patient, a so-called tumor feature vector (= probability-based classifier) was defined and used for grading. Biopsy was used as gold standard, and similarity based grading was compared to grading solely based on CE-T1w. Accuracy, sensitivity, and specificity of pure CE-T1w based glioma grading were 64.9%, 78.6%, and 56.5%, respectively. Similarity search based tumor grading allowed differentiation between low-grade (I or II) and high-grade (III) gliomas with an accuracy, sensitivity, and specificity of 83.8%, 78.6%, and 87.0%. Our findings indicate that integration of perfusion parameters and CE-T1w information in a semi-automatic similarity search based analysis improves the potential of MR-based glioma grading compared to CE-T1w data alone. (orig.)

  11. New similarity search based glioma grading

    Energy Technology Data Exchange (ETDEWEB)

    Haegler, Katrin; Brueckmann, Hartmut; Linn, Jennifer [Ludwig-Maximilians-University of Munich, Department of Neuroradiology, Munich (Germany); Wiesmann, Martin; Freiherr, Jessica [RWTH Aachen University, Department of Neuroradiology, Aachen (Germany); Boehm, Christian [Ludwig-Maximilians-University of Munich, Department of Computer Science, Munich (Germany); Schnell, Oliver; Tonn, Joerg-Christian [Ludwig-Maximilians-University of Munich, Department of Neurosurgery, Munich (Germany)

    2012-08-15

    MR-based differentiation between low- and high-grade gliomas is predominately based on contrast-enhanced T1-weighted images (CE-T1w). However, functional MR sequences as perfusion- and diffusion-weighted sequences can provide additional information on tumor grade. Here, we tested the potential of a recently developed similarity search based method that integrates information of CE-T1w and perfusion maps for non-invasive MR-based glioma grading. We prospectively included 37 untreated glioma patients (23 grade I/II, 14 grade III gliomas), in whom 3T MRI with FLAIR, pre- and post-contrast T1-weighted, and perfusion sequences was performed. Cerebral blood volume, cerebral blood flow, and mean transit time maps as well as CE-T1w images were used as input for the similarity search. Data sets were preprocessed and converted to four-dimensional Gaussian Mixture Models that considered correlations between the different MR sequences. For each patient, a so-called tumor feature vector (= probability-based classifier) was defined and used for grading. Biopsy was used as gold standard, and similarity based grading was compared to grading solely based on CE-T1w. Accuracy, sensitivity, and specificity of pure CE-T1w based glioma grading were 64.9%, 78.6%, and 56.5%, respectively. Similarity search based tumor grading allowed differentiation between low-grade (I or II) and high-grade (III) gliomas with an accuracy, sensitivity, and specificity of 83.8%, 78.6%, and 87.0%. Our findings indicate that integration of perfusion parameters and CE-T1w information in a semi-automatic similarity search based analysis improves the potential of MR-based glioma grading compared to CE-T1w data alone. (orig.)

  12. Are grades really oppressive?

    Institute of Scientific and Technical Information of China (English)

    张心宇

    2015-01-01

    Are grades really oppressive? The broad question's answer is of course open: it varies in different condition and in prerequisites. Like in Daily Californian,"Why Grades are Oppressive", the title tells us it standing: yes, grades are oppressive. In the article, the authors (this article was written by 16 students of the class) pointed out that the grading system has had a violent and powerfully destructive effect on our lives. Because grading focuses our attention on class requirements that we have no say in determination. And this makes many students equate their self-worth with the grades they get in exams. Besides, grades are intimately connected with a larger system of control in community, which trains students to be submissive and not to question or challenge it. In the end, the authors conclude that they should take responsibility for evaluating their own learning process.

  13. Collegiate Grading Practices and the Gender Pay Gap

    Directory of Open Access Journals (Sweden)

    Alicia C. Dowd

    2000-01-01

    Full Text Available Extending research findings by R. Sabot and J. Wakeman-Linn (1991, this article presents a theoretical analysis showing that relatively low grading quantitative fields and high grading verbal fields create a disincentive for college women to invest in quantitative study. Pressures on grading practices are modeled using higher education production functions.

  14. Collegiate Grading Practices and the Gender Pay Gap.

    Science.gov (United States)

    Dowd, Alicia C.

    2000-01-01

    Presents a theoretical analysis showing that relatively low grading quantitative fields and high grading verbal fields create a disincentive for college women to invest in quantitative study. Extends research by R. Sabot and J. Wakeman-Linn. Models pressures on grading practices using higher education production functions. (Author/SLD)

  15. Graded cluster algebras

    OpenAIRE

    Grabowski, Jan

    2015-01-01

    In the cluster algebra literature, the notion of a graded cluster algebra has been implicit since the origin of the subject. In this work, we wish to bring this aspect of cluster algebra theory to the foreground and promote its study. We transfer a definition of Gekhtman, Shapiro and Vainshtein to the algebraic setting, yielding the notion of a multi-graded cluster algebra. We then study gradings for finite type cluster algebras without coefficients, giving a full classification. Translating ...

  16. Integration of functional reliability analysis with hardware reliability: An application to safety grade decay heat removal system of Indian 500 MWe PFBR

    International Nuclear Information System (INIS)

    A passive system can fail either due to classical mechanical failure of components, referred to as hardware failure, or due to the failure of physical phenomena to fulfill the intended function, referred to as functional failure. In this paper a methodology is discussed for the integration of these two kinds of unreliability and applied to evaluate the integrated failure probability of the passive decay heat removal system of Indian 500 MWe prototype fast breeder reactor (PFBR). The probability of occurrence of various system hardware configurations is evaluated using the fault tree method and functional failure probabilities on the corresponding configurations are determined based on the overall approach reported in the reliability methods for passive system (RMPS) project. The variation of functional reliability with time, which is coupled to the probability of occurrence of various hardware system configurations is studied and incorporated in the integrated reliability analysis. It is observed that this consideration of the dependence of functional reliability on time will give significant advantages on system reliability. The integrated reliability analysis is also explained using an event tree. The impact of the provision for forced circulation in the primary circuit on functional reliability is also studied with this procedure and it is found that the forced circulation capability helps to bring down the total decay heat removal failure probability by lowering the peak temperatures after the reactor shut down.

  17. Dietary proteins improve endothelial function under fasting conditions but not in the postprandial state, with no effects on markers of low-grade inflammation.

    Science.gov (United States)

    Teunissen-Beekman, Karianna F M; Dopheide, Janneke; Geleijnse, Johanna M; Bakker, Stephan J L; Brink, Elizabeth J; de Leeuw, Peter W; Schalkwijk, Casper G; van Baak, Marleen A

    2015-12-14

    Endothelial dysfunction (ED) and low-grade inflammation (LGI) have a role in the development of CVD. The two studies reported here explored the effects of dietary proteins and carbohydrates on markers of ED and LGI in overweight/obese individuals with untreated elevated blood pressure. In the first study, fifty-two participants consumed a protein mix or maltodextrin (3×20 g/d) for 4 weeks. Fasting levels and 12 h postprandial responses of markers of ED (soluble intercellular adhesion molecule 1 (sICAM), soluble vascular cell adhesion molecule 1 (sVCAM), soluble endothelial selectin and von Willebrand factor) and markers of LGI (serum amyloid A, C-reactive protein and sICAM) were evaluated before and after intervention. Biomarkers were also combined into mean Z-scores of ED and LGI. The second study compared 4 h postprandial responses of ED and LGI markers in forty-eight participants after ingestion of 0·6 g/kg pea protein, milk protein and egg-white protein. In addition, postprandial responses after maltodextrin intake were compared with a protein mix and sucrose. The first study showed significantly lower fasting ED Z-scores and sICAM after 4 weeks on the high-protein diet (P≤0·02). The postprandial studies found no clear differences of ED and LGI between test meals. However, postprandial sVCAM decreased more after the protein mix compared with maltodextrin in both studies (P≤0·04). In conclusion, dietary protein is beneficial for fasting ED, but not for fasting LGI, after 4 weeks of supplementation. On the basis of Z-scores, postprandial ED and LGI were not differentially affected by protein sources or carbohydrates. PMID:26400262

  18. Math Academy: Can You See It in Nature? Explorations in Patterns & Functions. Book 2: Supplemental Math Materials for Grades 3-8

    Science.gov (United States)

    Rimbey, Kimberly

    2007-01-01

    Created by teachers for teachers, the Math Academy tools and activities included in this booklet were designed to create hands-on activities and a fun learning environment for the teaching of mathematics to students. This booklet contains the "Math Academy--Can You See It in Nature? Explorations in Patterns & Functions," which a teacher can use to…

  19. The Impact of Using Technology on Student Achievement: Teaching Functions with the TI-Nspire to 9th Grade Algebra Students

    Science.gov (United States)

    Buckner, Barbara Renee

    2011-01-01

    The purpose of this study was to determine the effect of TI-Nspire graphing calculator use on student achievement and on teacher behavior variables of planning, teaching, and assessing. This study investigated the teaching of functions by teachers using the TI-Nspire graphing calculator versus teachers using a non-graphing scientific calculator. …

  20. An Exploratory Study of the Relationships between Family Functioning and Parenting Styles: The Perceptions of Mothers of Young Grade School Children.

    Science.gov (United States)

    Mupinga, Emily Evellyne; Garrison, M. E. Betsy; Pierce, Sarah H.

    2002-01-01

    A study of 151 mothers of elementary students identified relationships between parenting styles (authoritative, authoritarian, permissive) and family functioning (adaptability, cohesion). Families with balanced and moderately balanced levels of adaptability and cohesion had higher levels of authoritative parenting. Midrange balance was associated…

  1. Classroom: Efficient Grading

    Science.gov (United States)

    Shaw, David D.; Pease, Leonard F., III.

    2014-01-01

    Grading can be accelerated to make time for more effective instruction. This article presents specific time management strategies selected to decrease administrative time required of faculty and teaching assistants, including a multiple answer multiple choice interface for exams, a three-tier grading system for open ended problem solving, and a…

  2. Controlling Grade Inflation

    Science.gov (United States)

    Stanoyevitch, Alexander

    2008-01-01

    In this article concerning grade inflation, the author restricts his attention to the college and university level, although many of the tools and ideas developed here should be useful for high schools as well. The author considers the relationships between grades instructors assign and scores they receive on end-of-the semester student…

  3. [Grading of neuroendocrine tumors].

    Science.gov (United States)

    Saeger, W; Schnabel, P A; Komminoth, P

    2016-07-01

    The current WHO classification of neuroendocrine tumors (NET) differentiates between typical carcinoids (low grade NET), atypical carcinoids (intermediate grade NET) and small cell and large cell carcinomas (high grade NET) according to the prognosis. Neuroendocrine neoplasms (NEN) of the gastrointestinal tract and the pancreas are graded in an identical way. Together with the TNM system this enables a preoperative estimation of the prognosis in biopsies and fine needle aspirates. Well-differentiated tumors are graded into G1 tumors by the number of mitoses, tumors (2-20 mitoses/10 HPF, Ki-67 3-20 %). Discrepancies between the number of mitoses and the Ki-67 index are not uncommon and in these cases the higher value of the two should be applied. The more differentiated tumors of the G3 type have to be differentiated from undifferentiated carcinomas of the small cell type and large cell type with a much poorer prognosis. Prognosis relevant grading of thyroid cancers is achieved by special subtyping so that the G1-G3 system is not applicable. The rare cancers of the parathyroid gland and of the pituitary gland are not graded. Adrenal tumors also have no grading system. The prognosis is dependent on the Ki-67 index and with some reservations on the established scoring systems. PMID:27379621

  4. Grading Exceptional Learners

    Science.gov (United States)

    Jung, Lee Ann; Guskey, Thomas R.

    2010-01-01

    Teachers often grapple with the challenge of giving report card grades to students with learning disabilities and English language learners. The authors offer a five-step model that "offers a fair, accurate, and legal way to adapt the grading process for exceptional learners." The model begins with a high-quality reporting system for all students…

  5. Beef grading by ultrasound

    Science.gov (United States)

    Gammell, P. M.

    1981-01-01

    Reflections in ultrasonic A-scan signatures of beef carcasses indicate USDA grade. Since reflections from within muscle are determined primarily by fat/muscle interface, richness of signals is direct indication of degree of marbling and quality. Method replaces subjective sight and feel tests by individual graders and is applicable to grade analysis of live cattle.

  6. Making Grading Work.

    Science.gov (United States)

    Lotto, Edward; Smith, Bruce

    Two teachers have developed a procedure for grading student compositions that seems fairer to both them and their students. The students are given a choice of which papers they wish to submit for grading, and when they do submit work, the papers are identified by a number only (chosen by the student and indexed in a class card file). Each teacher…

  7. SIMULATION AND OPTIMIZATION OF THERMAL RESIDUAL STRESS IN COATING STRUCTURE WITH FUNCTIONALLY GRADED MATERIAL LAYER%含FGM的涂层结构中热残余应力的分析与优化

    Institute of Scientific and Technical Information of China (English)

    张榕京; 黄晨光; 段祝平

    2001-01-01

    An elasto-plastic finite element method is developed to predict the thermal residual stress of thermal spraying coatings with functionally graded material (FGM) layer. The optimized distribution form and parameter p about the volume fractions of various constituents in the FGM are obtained by the first order optimization method in the AL2O3 -Ni model system. The effects of geometry and material behavior on the optimization results are investigated numerically, including the temperature sensitivity of FGM and substrate material. It is found that the optimization of the constituent contents in FGM reduces the magnitude of residual stresses to a large degree. And the maximum residual stresses shun the weakest part of the coating structure by the optimization designing. When the length of specimen, the thickness of FGM layer and the thermal expansion coefficient of the substrate increase, while the distribution parameter p decreases. The results presented in this paper are useful for the design of thermal spraying coatings.%本文利用有限元方法和优化理论,对含FGM(Functionally Graded Materials)层的热喷涂构件中的残余应力进行了数值分析,并获得了FGM内各组份体积含量分布的最优化形式和参数p。同时,我们也研究了喷涂构件的几何形状、涂层及基底的材料性能对于p的影响规律。在本文的分析中,考虑了基底材料和FGM的塑性变形以及其性能对于温度的依赖。本文的工作将有利于含FGM层的热喷涂构件的设计与生产。

  8. Vascular grading of angiogenesis

    DEFF Research Database (Denmark)

    Hansen, S; Grabau, D A; Sørensen, Flemming Brandt; Bak, M; Vach, W; Rose, C

    2000-01-01

    The study aimed to evaluate the prognostic value of angiogenesis by vascular grading of primary breast tumours, and to evaluate the prognostic impact of adding the vascular grade to the Nottingham Prognostic Index (NPI). The investigation included 836 patients. The median follow-up time was 11...... years and 4 months. The microvessels were immunohistochemically stained by antibodies against CD34. Angiogenesis was graded semiquantitatively by subjective scoring into three groups according to the expected number of microvessels in the most vascular tumour area. The vascular grading between observers...... had clinical impact for 24% of the patients, who had a shift in prognostic group, as compared to NPI, and implied a better prognostic dissemination. We concluded that the angiogenesis determined by vascular grading has independent prognostic value of clinical relevance for patients with breast cancer....

  9. Five Obstacles to Grading Reform

    Science.gov (United States)

    Guskey, Thomas R.

    2011-01-01

    Educators seeking to reform grading must combat five long-held traditions that stand as formidable obstacles to change: (1) Grades should provide the basis for differentiating students; (2) grade distributions should resemble a bell-shaped curve; (3) grades should be based on students' standing among classmates; (4) poor grades prompt students to…

  10. Novel UV Initiator for Functionalization of Multiwalled Carbon Nanotubes by Atom Transfer Radical Polymerization Applied on Two Different Grades of Nanotubes

    DEFF Research Database (Denmark)

    Daugaard, Anders Egede; Jankova Atanasova, Katja; Bøgelund, J.; Nielsen, J.K.; Hvilsted, Søren

    2010-01-01

    A novel nonoxidative method for preparation of functionalized multiwalled carbon nanotubes (MWCNT) has been developed based on a UV sensitive initiator for atom transfer radical polymerization (ATRP). The method has been investigated with respect to ligands and polymerization time for the...... differences in reactivity and polymer loading, underlining the importance of the choice of MWCNT starting material. In addition to styrene, also poly(ethylene glycol) methacrylate (PEGMA) was shown to polymerize from the surface of the MWCNT. Finally, initial results from composites of polystyrene or...

  11. Nebraska Science Standards: Grades K-12

    Science.gov (United States)

    Nebraska Department of Education, 2010

    2010-01-01

    This publication presents the Nebraska Science Standards for Grades K-12. The standards are presented according to the following grades: (1) Grades K-2; (2) Grades 3-5; (3) Grades 6-8; and (4) Grades 9-12.

  12. Estimating the lifetimes of titanium containers for nuclear fuel waste: A damage function for the crevice corrosion of grade-2 titanium

    International Nuclear Information System (INIS)

    The assumptions upon which the lifetime failure model used in the postclosure assessment is based are reevaluated. In particular, the conservations involved in assuming that crevice initiation would occur, and that sufficient oxygen would be present to maintain crevice propagation to failure, are discussed. Unless the period required to saturate the environment around the container can be specified with some certainty, it remains necessary to assume corrosion would initiate rapidly on all containers. A modified version of the container lifetime model has been developed which avoids the need to use averaged temperature profiles. In this model, these profiles are converted to propagation rate profiles using an experimental activation energy and then numerically integrated to predict container failure times. A damage function is developed relating the maximum depth of penetration by crevice corrosion to either the time since emplacement in the vault or the total amount of oxygen consumed. This function is used to estimate the maximum penetration depth expected if all the oxygen available in a borehole is consumed in crevice corrosion and to determine the impact on container lifetimes of various repassivation criteria. The factors likely to cause repassivation are summarized, and a number of engineering approaches to extending container lifetimes suggested. (author). 22 refs., 1 tab., 17 figs

  13. Grade inflation : fact or myth?

    OpenAIRE

    Bello, Amelia L.; Roger M. Valientes

    2008-01-01

    Real grade inflation is the upward shift in grades without a similar rise in achievement (Kohn [2002]; Rosovsky and Hartley [2002]). It implies a decline in standards and obscures the role of grades as a signal of academic ability. Guskey [2003] believes that resolving the debate on grade inflation depends on clarifying the purpose/meaning of grades. Grades may be used either to discriminate among students or to reflect the degree to which students have learned. The research attempts to valid...

  14. Post-bucking configuration of a functionally graded material column under distributed load%功能梯度压杆在均布载荷作用下的后屈曲形态

    Institute of Scientific and Technical Information of China (English)

    李清禄; 李世荣

    2011-01-01

    对受均布载荷作用功能梯度材料(FGM)压杆的屈曲及后屈曲行为进行了分析.基于杆的大变形理论,考虑杆的轴线伸长,建立了受均布载荷作用下细长FGM压杆的几何非线性平衡方程,其中假设FGM杆的性质沿厚度方向按照幂函数连续变化.采用打靶法和解析延拓法数值求解非线性两点边值问题,获得了一端自由一端固定FGM杆的后屈曲数值解.给出了不同梯度指标下FGM杆的后屈曲特征曲线,并与金属和陶瓷两种单相材料杆的相应特性进行了比较,分析和讨论了材料的梯度性质参数对杆变形的影响.结果表明:FGM杆后屈曲行为与各向同性均质杆有很大区别,梯度指数对杆的屈曲载荷以及后屈曲形态有明显的影响.%The buckling and post-buckling behaviors of a functionally graded material (FGM) column under distributed load were analysed. Based on the large deformation theory and consideration of the axial extension of the column, the quilibrium equations with geometric nonlinearity of an elastic FGM column subjected to distributed load were established. In the analysis, it was assumed that the material properties of the column vary continuously as a power function of the thickness coordinate. By using shooting method and analytical continuation, the nonlinear boundary-value problem was solved numerically and buckling and post-buckling response of FGM column with freefixed edges were obtained. The post-buckling characteristics curves of FGM column under the different graded index were plotted, which were compared with the those of pure metal and ceramic material columns. The effects of material gradient property on the buckling deformation and critical load of beam were discussed in details. The results show that the post-buckling behavior of the FGM column are different from that of homogenous column, and the gradient index of the material have significant effect on the bucking load and post-buckling behavior

  15. Scattering of SH Wave on an Eccentric Crack in a Functionally Graded Piezoelectric Strip%功能梯度压电带中偏心裂纹对SH波的散射问题

    Institute of Scientific and Technical Information of China (English)

    白艳艳; 李星

    2012-01-01

    功能梯度材料在机械、光电、核能、生物工程领域的应用非常广泛.但由于生产技术及工作环境等方面的原因,功能梯度材料内部常常产生各种形式的裂纹并最终导致材料破坏,这将会给材料所处的整个系统带来巨大损失.因此研究功能梯度材料的断裂问题对于该种材料的设计,制备和合理、安全的应用具有极大的促进作用.本文在压电材料线性宏观理论下,研究了功能梯度压电带中偏心裂纹对SH波的散射问题.借助于积分变换方法,在电非渗透型边界条件的情况下,将所考虑的问题转化为奇异积分方程,运用Gauss-Chebyshev数值积分方法对奇异积分方程进行了数值求解,进而得到了裂纹尖端的应力和电位移强度因子.%Functionally graded materials (FGMs) have been used in many fields, such as machinery, photoelectron, nuclear energy and biomedical imaging. But due to the reasons of limited technology, working condition and some other factors, various cracks always arise in real FGMs. Therefore, it is significantly meaningful to study the crack problems of FGMs. In this paper, the scattering of SH wave on eccentric crack problems of the functionally graded piezoelectric strip is investigated on the basis of linear macroscopic theory of piezoelectric materials. By employing the integral transform method, the problem in consideration is transformed into a system of singular integral equations of the first kind under impermeable boundary conditions. The singular integral equations for impermeable cracks are numerically solved by using the Gauss-Chebyshev integration method. Stress intensity factors at crack tips are thus obtained.

  16. Processing of W-Cu functionally graded materials (FGM) through the powder metallurgy route: application as plasma facing components for ITER-like thermonuclear fusion reactor; Elaboration de materiaux W-Cu a gradient de proprietes fonctionnelles (FGM) par metallurgie des poudres: application en tant que composants face au plasma de machines de fusion thermonucleaire de type Iter

    Energy Technology Data Exchange (ETDEWEB)

    Raharijaona, J.J.

    2009-11-15

    The aim of this study was to study and optimize the sintering of W-Cu graded composition materials, for first wall of ITER-like thermonuclear reactor application. The graded composition in the material generates graded functional properties (Functionally Graded Materials - FGM). Rough thermomechanical calculations have shown the interest of W-Cu FGM to improve the lifetime of Plasma Facing Components (PFC). To process W-Cu FGM, powder metallurgy route was analyzed and optimized from W-CuO powder mixtures. The influence of oxide reduction on the sintering of powder mixtures was highlighted. An optimal heating treatment under He/H{sub 2} atmosphere was determined. The sintering mechanisms were deduced from the analysis of the effect of the Cu-content. Sintering of W-Cu materials with a graded composition and grain size has revealed two liquid migration steps: i) capillary migration, after the Cu-melting and, ii) expulsion of liquid, at the end of sintering, from the dense part to the porous part, due to the continuation of W-skeleton sintering. These two steps were confirmed by a model based on capillary pressure calculation. In addition, thermal conductivity measurements were conducted on sintered parts and showed values which gradually increase with the Cu-content. Hardness tests on a polished cross-section in the bulk are consistent with the composition profiles obtained and the differential grain size. (author)

  17. Bending Analysis of Functionally Graded Materials Beam Considering Different Shear Deformation Theory%计及不同剪切变形的功能梯度材料梁的弯曲分析

    Institute of Scientific and Technical Information of China (English)

    赵凤群; 王忠民

    2014-01-01

    研究矩形截面功能梯度材料(Functionally graded materials,FGM)梁在不同剪切变形理论下的静力弯曲问题.假设FGM梁由金属和陶瓷两种材料构成,其等效物性参数沿厚度方向连续变化,且遵从简单幂率变化规律.基于最小势能原理,建立以轴向位移、横向位移及转角为未知函数的FGM梁的运动微分方程组.对简支FGM梁,采用Fourier级数法获得5种剪切变形理论下FGM梁的挠度、轴向位移及转角曲线,分析梁的长高比、梯度指标对弯曲变形的影响,分析不同剪切变形理论下FGM梁的切应力和正应力的分布特性,并与均质材料梁的静力弯曲特性进行比较.给出FGM梁的中性轴位置随梯度指标的变化曲线并进行分析.

  18. 论“音乐反应”训练在中国舞考级教学中的作用%On Functions of “Music Response" Training in Education of Chinese Dance Graded Examination

    Institute of Scientific and Technical Information of China (English)

    姚平

    2012-01-01

    Music and dance are sister arts,so music training is greatly emphasized in teaching of Chinese Dance Graded Examination courses.The author of the paper expounds the significance and necessity of "music response" training in dance teaching based on its four functions-improvement of brain growth,cultivation of imaginativeness and creativeness,improvement and perfection of combination performance,as well as learning of dance improvisation.%音乐与舞蹈是姊妹艺术,中国舞考级教学非常强调对音乐的训练。笔者从音乐反应训练能够美化人的心灵,促进大脑发育,能够促进想象力和创造力的培养,能够促进组合的表演与完善以及能够促进对即兴舞的学习这四个方面进行论述,旨在强调"音乐反应"训练在中国舞考级教学中的重要性和必要性。

  19. Game Theory based Peer Grading Mechanisms for MOOCs

    OpenAIRE

    Wu, William; Kaashoek, Nicolaas; Tzamos, Christos; Weinberg, Matthew; Daskalakis, Konstantinos

    2015-01-01

    An efficient peer grading mechanism is proposed for grading the multitude of assignments in online courses. This novel approach is based on game theory and mechanism design. A set of assumptions and a mathematical model is ratified to simulate the dominant strategy behavior of students in a given mechanism. A benchmark function accounting for grade accuracy and workload is established to quantitatively compare effectiveness and scalability of various mechanisms. After multiple iterations of m...

  20. Discrimination in Grading

    OpenAIRE

    Hanna, Rema N.; Linden, Leigh L.

    2012-01-01

    We report the results of an experiment that was designed to test for discrimination in grading in India. We recruited teachers to grade exams. We randomly assigned child "characteristics" (age, gender, and caste) to the cover sheets of the exams to ensure that there is no relationship between these observed characteristics and the exam quality. We find that teachers give exams that are assigned to be lower caste scores that are about 0.03 to 0.08 standard deviations lower than those that are ...

  1. Methods of graded rings

    CERN Document Server

    Nastasescu, Constantin

    2004-01-01

    The topic of this book, graded algebra, has developed in the past decade to a vast subject with new applications in noncommutative geometry and physics. Classical aspects relating to group actions and gradings have been complemented by new insights stemming from Hopf algebra theory. Old and new methods are presented in full detail and in a self-contained way. Graduate students as well as researchers in algebra, geometry, will find in this book a useful toolbox. Exercises, with hints for solution, provide a direct link to recent research publications. The book is suitable for courses on Master level or textbook for seminars.

  2. Nonsmooth fracture dynamics of functionally graded materials

    Science.gov (United States)

    Perales, F.; Monerie, Y.; Chrysochoos, A.

    2006-08-01

    This paper presents a numerical framework for the simulation of dynamic fracture of heterogeneous material. It consists in a multibody approach based both on the concept of Frictional Cohesive Zone Model and on NonSmooth Contact Dynamics. The heterogeneities of the material are taken into account using a multiscale method. The microscopic scale corresponds to the scale of heterogeneities. The macroscopic scale corresponds to the structure where gradients of properties will be invoked. The ability of the framework is illustrated by the fracture of hydrided Zircaloy-4, constituting nuclear cladding tube, under transient loading.

  3. The Maximal Graded Left Quotient Algebra of a Graded Algebra

    Institute of Scientific and Technical Information of China (English)

    Gonzalo ARANDA PINO; Mercedes SILES MOLINA

    2006-01-01

    We construct the maximal graded left quotient algebra of every graded algebra A without homogeneous total right zero divisors as the direct limit of graded homomorphisms (of left A-modules)from graded dense left ideals of A into a graded left quotient algebra of A. In the case of a superalgebra,and with some extra hypothesis, we prove that the component in the neutral element of the group of the maximal graded left quotient algebra coincides with the maximal left quotient algebra of the component in the neutral element of the group of the superalgebra.

  4. Pay for Grades

    Science.gov (United States)

    Johnston, Howard

    2008-01-01

    The practice of paying students to earn good grades either in class or on standardized achievement tests has touched off a storm of controversy. Praised by some educators as a way of linking economic rewards to school performance, it is being tested in a number of large cities, such as New York, Baltimore and Chicago, as well as some smaller…

  5. Purpose-Driven Grading

    Science.gov (United States)

    Carlson, Jane A. K.; Kimpton, Ann

    2010-01-01

    Allowing students to improve their grade by revising their written work may help students learn to revise, but it gives them no incentive to turn in quality work from the start. This article proposes a way to invert the process, thereby teaching students how to revise, while enforcing a more disciplined approach to good writing. (Contains 3…

  6. Grades as Information

    Science.gov (United States)

    Grant, Darren

    2007-01-01

    We determine how much observed student performance in microeconomics principles can be attributed, inferentially, to three kinds of student academic "productivity," the instructor, demographics, and unmeasurables. The empirical approach utilizes an ordered probit model that relates student performance in micro to grades in prior coursework,…

  7. Social Studies: Grade 8.

    Science.gov (United States)

    Manitoba Dept. of Education, Winnipeg.

    This Manitoba (Canada) curriculum guide for eighth grade social studies students contains suggested teaching strategies and learning activities in four units covering: (1) life during prehistoric and early historic times; (2) ancient civilizations; (3) life in early modern Europe; and (4) life in the modern world. Each unit includes an overview,…

  8. Endangered Animals. Second Grade.

    Science.gov (United States)

    Popp, Marcia

    This second grade teaching unit centers on endangered animal species around the world. Questions addressed are: What is an endangered species? Why do animals become extinct? How do I feel about the problem? and What can I do? Students study the definition of endangered species and investigate whether it is a natural process. They explore topics…

  9. FY 1995 development of fluorinated hydriding alloys with multi functional and functionally-graded surface and their application to energy conversion devices; 1995 nendo keishagata fukugo kino wo hyomen ni motsu suiso kyuzo gokin no kaihatsu to energy henkan gijutsu eno oyo

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-03-01

    The project is the extended researches of a fluorination technique invented by the project leader (Suda) for improving the surface properties and characteristics of conventional hydriding alloys from the following viewpoints; (1) To investigate the roles of fluorinated surface during hydrogen uptake both in the gas-solid and the electrochemical reactions. (2) To elucidate the factors which increase the protective nature of the surface. (3) To develop a material design procedure for synthesizing thin layer of functionally graded surface which is composed of metallic Ni and the fluoride compound. (1) An advanced fluorination technique was developed to incorporate metallic Ni in the surface fluoride layer. (2) Metallic Ni was successfully distributed in a functionally graded manner in the Surface fluoride layer. (3) Through the technique developed, the following properties and characteristics were successfully donated in the fluorinated hydriding alloys such as AB{sub 5}, AB{sub 2}, and AB; (3-1)Surface oxides which act as the resistant layer to the hydrogen up take was completely eliminated to result in the enhancement of the initial activation characteristics. (3-2) Hydrogen selectivity and permeability was greatly improved. (3-3) Surface protective nature against the impurity gases and contaminants was significantly improved. (3-4) Initial activation characteristics both in the gas-solid and the electrochemical reactions were distinguishably improved. (3-5) Fluorinated surface was found to function as the catalyst for a methanation reaction between the CO{sub 2} gas adsorbed over the fluorinated surface and the monatomic hydrogen absorbed in the metal lattice of the crystalline structure of the hydriding alloys. (4) A technique was developed for increasing the specific surface area and decreasing the specific surface diameter of the fluorinated hydriding alloy articles. (NEDO)

  10. THE ACOUSTIC RADIATION CHARACTERISTICS OF FUNCTIONALLY GRADED CYLINDRICAL SEHLLS IN THERMAL ENVIRONMENT%热环境中功能梯度圆柱壳声辐射特性研究

    Institute of Scientific and Technical Information of China (English)

    姚熊亮; 叶曦; 王献忠

    2013-01-01

    基于经典壳体理论,推导了热环境下,流场中功能梯度圆柱壳的受迫振动方程,研究了不同温度分布方式、壳体材料参数以及周围流场参数对功能梯度圆柱壳声辐射特性的影响.研究结果表明:温度变化会引起功能梯度圆柱壳材料特性的改变,在壳体内产生热应力,影响流场中壳体的声辐射特性.温度变化对不同频段壳体辐射声功率的影响不同.重流体中,温度变化对声功率的影响随着频率的增高而增大;轻流体中,温度升高使频率较低时的声功率峰值向低频方向移动,且峰值减小,当接近环频率时,随着温度升高,辐射声功率下降.均匀升温对壳体声辐射特性的影响高于非均匀升温.非均匀升温时,重流体中体积分数指数对辐射声功率的影响比轻流体中更明显,且主要体现在对峰值位置的影响.%Based on the classical shell theory,the forced vibration equations of functionally graded cylindrical shells in the thermal environment with fluid are deduced.The influences of different temperature distribution patterns,shell material parameters and surrounding fluid field parameters on sound radiation induced by functionally graded cylindrical shells are studied.The results show that the temperature variation will change the shell material properties,and generate the thermal stress in the shell,which will impact the characteristics of sound radiation from the shell in the fluid field.The influence of temperature variation is different on the sound power in different frequencies.In the heavy fluid,the impact of temperature variation to the sound power is enhanced with the rising of frequency.In the light fluid,the peak value of sound power is decreased and moved to the low-frequency with the rising of temperature when the frequency is lower,and the sound power near the loop frequency is reduced as well.The influence of uniform temperature rise on sound radiation characteristics is more

  11. Phantom energy from graded algebras

    OpenAIRE

    Chaves, Max; Singleton, Douglas

    2006-01-01

    We construct a model of phantom energy using the graded Lie algebra SU(2/1). The negative kinetic energy of the phantom field emerges naturally from the graded Lie algebra, resulting in an equation of state with w

  12. Four Steps in Grading Reform

    Science.gov (United States)

    Guskey, Thomas R.; Jung, Lee Ann

    2012-01-01

    The field of education is moving rapidly toward a standards-based approach to grading. School leaders have become increasingly aware of the tremendous variation that exists in grading practices, even among teachers of the same courses in the same department in the same school. Consequently, students' grades often have little relation to their…

  13. Cognitive impairments in patients with low grade gliomas and high grade gliomas

    Directory of Open Access Journals (Sweden)

    Eliane C. Miotto

    2011-08-01

    Full Text Available OBJECTIVE: The relationship between brain tumors and cognitive deficits is well established in the literature. However, studies investigating the cognitive status in low and high-grade gliomas patients are scarce, particularly in patients with average or lower educational level. This study aimed at investigating the cognitive functioning in a sample of patients with low and high-grade gliomas before surgical intervention. METHOD: The low-grade (G1, n=19 and high-grade glioma (G2, n=8 patients underwent a detailed neuropsychological assessment of memory, executive functions, visuo-perceptive and visuo-spatial abilities, intellectual level and language. RESULTS: There was a significant impairment on verbal and visual episodic memory, executive functions including mental flexibility, nominal and categorical verbal fluency and speed of information processing in G2. G1 showed only specific deficits on verbal and visual memory recall, mental flexibility and processing speed. CONCLUSION: These findings demonstrated different levels of impairments in the executive and memory domains in patients with low and high grade gliomas.

  14. Some "Big Ideas" of Algebra in the Middle Grades.

    Science.gov (United States)

    Edwards, Thomas G.

    2000-01-01

    Identifies big ideas for the informal study of algebra-related topics in the middle grades including notation, variable, function, and properties of number. Suggests meaningful ways to accomplish them. (YDS)

  15. 7 CFR 810.1404 - Grades and grade requirements for sorghum.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 7 2010-01-01 2010-01-01 false Grades and grade requirements for sorghum. 810.1404... OFFICIAL UNITED STATES STANDARDS FOR GRAIN United States Standards for Sorghum >grades and Grade Requirements § 810.1404 Grades and grade requirements for sorghum. Grading factors Grades U.S. Nos. 1 1 2 3...

  16. Looking Forward to High School and College: Middle Grade Indicators of Readiness in Chicago Public Schools

    Science.gov (United States)

    Allensworth, Elaine M.; Gwynne, Julia A.; Moore, Paul; de la Torre, Marisa

    2014-01-01

    There is a very large population of students who struggle with the transition from the middle grades to high school, raising concerns that high school failures are partially a function of poor middle grade preparation. As a result, middle grade practitioners are grappling with questions about what skills students need to succeed in high school,…

  17. TCM syndromes of CHD-related heart failure, cardiac function grading and ultrasonic cardiogram indexes%冠心病心力衰竭中医证候与心功能分级及超声心动相关指标的研究

    Institute of Scientific and Technical Information of China (English)

    陈婵; 张鹏; 王娟; 赵慧辉; 孟永梅; 王伟

    2011-01-01

    Objective To investigate the relationship among TCM syndromes, cardiac function grading and ultrasonic cardiogram indexes of coronary heart disease (CHD) -related heart failure. Methods The table for collecting clinical information of TCM four examinations was made based on the literature survey and experts consultation. The patients ( n = 98) with CHD-related heart failure were examined with ultrasonic cardiogram for estimating their cardiac function grades and TCM syndrome types, and their information of four examinations were collected at the same time. All data were analyzed statistically. Results The group of qi-deficiency blood-stasis, and group of qi-deficiency blood-stasis combining phlegm-turbidity distributed mainly in group II cardiac function. The type of qi-deficiency blood-stasis combining water-retention and group of qi-deficiency blood-stasis combining phlegm-water intermingling distributed mainly in grade M cardiac function. The occurrence rate of left atrial enlargement was higher in the group of qi-deficiency blood-stasis combining water-reter-retention and group of qi-deficiency blood-stasis combiming phlegm-water intermingling compared with other two syndrome groups ( P < 0.05). The occurrence rate of left ventricle systolic dysfunction was higher in the group of qi-deficiency blood-stasis combining phlegm-water intermingling compared with the group of qi-deficiency blood-stasis(P <0. 01). The occurrence rate of left atrial enlargement was higher in the group of grade IE cardiac function compared with group of grade Ⅱ cardiac function ( P < 0. 05 ). The occurrence rate of left ventricle diastolic dysfunction was higher significantly in the group of grade II cardiac function than that in the group of grade IV cardiac function ( P < 0.05 ). The occurrence rate of left ventricle systolic dysfunction was higher significantly in the group of grade M cardiac function and grade Ⅳ cardiac function than that in the group of grade II cardiac function

  18. A revision of the Cormack and Lehane laryngoscopic grading system with special consideration to grade II laryngoscopic view

    Directory of Open Access Journals (Sweden)

    Hussain khan Z

    2007-10-01

    Full Text Available Background: The major responsibility of an anesthesiologist is to provide adequate respiration for the patient. The most vital element in providing functional respiration is the airway. No anesthetic is safe unless diligent efforts are devoted to maintaining an intact functional airway. Difficult intubation had been classified into four grades, according to the view obtainable at laryngoscopy by Cormack and Lehane in 1984. This grading system has been in use to evaluate and manage those patients with difficult airway by anesthesiologists. In clinical state, grades III and IV are quite rare, so the need for a modified Cormack and Lehane grading system was felt. The use of a modified Cormack-Lehane scoring system of laryngoscopic views during direct laryngoscopy, was previously examined in the Western population. Koh and his co-workers had examined this modified Cormack and Lehane grading system in Asian population in a study in Singapore General Hospital. The aim of this study was to investigate this scoring system in Iranian patients.Methods: In a cross sectional study, a modified version of the Cormack and Lehane grading system was evaluated in 300 patients requiring tracheal intubation. In the modified system, grade II (only part of the glottis is visible was divided into IIa (part of the cords is visible and IIb (only the arytenoids or the very posterior origin of the cords are visible. Difficult intubation was defined as requiring more than one laryngoscopy or the use of special equipments.Results: Sixty eight patients (22.7% were scored as grade IIa and 32 (7.7% as grade IIb. The prevalence of difficult intubation in grade IIb was significantly higher than patients in group IIa (47.8% vs. 2.9% respectively, Fisher's exact test, p= 0.001Conclusion: The modified grading system provides more information than the original Cormack and Lehane system."n 

  19. Lumbosacral epidural lipomatosis: MRI grading

    Energy Technology Data Exchange (ETDEWEB)

    Borre, Daniel G. [Department of MRI, RM-Hastings, Clinica Monte Grande, Monte Grande, Buenos Aires (Argentina); Department of MRI, Oncologic Center of Excellence, Gonnet, Buenos Aires (Argentina); Sociedad Argentina de Radiologia, Arenales 1985 P.B., Ciudad Autonoma de Buenos Aires C1124AAC (Argentina); Borre, Guillermo E. [Department of MRI, RM-Hastings, Clinica Monte Grande, Monte Grande, Buenos Aires (Argentina); Department of MRI, Oncologic Center of Excellence, Gonnet, Buenos Aires (Argentina); Aude, Flavio [Department of MRI, Oncologic Center of Excellence, Gonnet, Buenos Aires (Argentina); Palmieri, Gladys N. [Department of MRI, RM-Hastings, Clinica Monte Grande, Monte Grande, Buenos Aires (Argentina)

    2003-07-01

    Lumbosacral epidural lipomatosis (LEL) is characterized by excessive deposition of epidural fat (EF). The purpose of our retrospective study was to quantify normal and pathologic amounts of EF in order to develop a reproducible MRI grading of LEL. In this study of 2528 patients (1095 men and 1433 women; age range 18-84 years, mean age 47.3 years) we performed a retrospective analysis of MRI exams. We obtained four linear measurements at the axial plane parallel and tangent to the superior end plate of S1 vertebral body: antero-posterior diameter of dural sac (A-Pd DuS), A-Pd of EF, located ventrally and dorsally to the DuS, and A-Pd of the spinal canal (Spi C). We calculated (a) DuS/EF index and (b) EF/Spi C index. We developed the following MRI grading of LEL: normal, grade 0: DuS/EF index {>=}1.5, EF/Spi C index {<=}40%; LEL grade I: DuS/EF index 1.49-1, EF/Spi C index 41-50% (mild EF overgrowth); LEL grade II: DuS/EF index 0.99-0.34, EF/Spi C index 51-74% (moderate EF overgrowth); LEL grade III: DuS/EF index {<=}0.33, EF/Spi C index {>=}75% (severe EF overgrowth). The MRI exams were evaluated independently by three readers. Intra- and interobserver reliabilities were obtained by calculating Kappa statistics. The MRI grading showed the following distribution: grade 0, 2003 patients (79.2%); LEL grade I, 308 patients (12.2%); LEL grade II, 165 patients (6.5%); and LEL grade III, 52 patients (2.1%). The kappa coefficients for intra- and interobserver agreement in a four-grade classification system were substantial to excellent: intraobserver, kappa range 0.79 [95% confidence interval (CI), 0.65-0.93] to 0.82 (95% CI, 0.70-0.95); interobserver, kappa range 0.76 (95% CI, 0.62-0.91) to 0.85 (95% CI, 0.73-0.97). In LEL grade I, there were no symptomatic cases due to fat hypertrophy. LEL grade II was symptomatic in only 24 cases (14.5%). In LEL grade III, all cases were symptomatic. A subgroup of 22 patients (42.3%) showed other substantial spinal pathologies (e

  20. Mechanical properties of CNT reinforced hybrid functionally graded materials for bioimplants%生物植入用碳纳米管增强混合功能梯度材料的力学性能

    Institute of Scientific and Technical Information of China (English)

    M Asif HUSSAIN; Myong Ho KIM; Adnan MAQBOOL; F Ahmad KHALID; Nabi BAKHSH; Ali HUSSAIN; Jamil Ur RAHMAN; Jong Kyu PARK; Tae Gone PARK; Lee Jae HYUN

    2014-01-01

    The hybrid functionally graded materials (FGM) of hydroxyapatite (HA), stainless steel 316L (SS316L) and carbon nanotubes (CNT) were synthesized for biomedical implants. Three different types of FGM were produced by the combination of SS316L and CNT to reinforce HA in discrete layers of FGM. In the first type of FGM, concentration of SS316L was varied from 10% to 40% (mass fraction) with an increment of 10% to reinforce micro HA. In the second type of FGM, 0.5% (mass fraction) functionalized CNT was added by maintaining the rest of composition as that of the first type of FGM. In the third type of FGM, mixture of micro and nano HA (mass ratio1:1) was used, keeping rest of composition similar to the second type of FGM. All types of FGM were subjected to uniaxial compaction and sintered by pressureless sintering technique at similar compaction and sintering parameters. The results show that the densification is enhanced with the addition of CNT and nanocrystalline HA in the FGM. Hardness and fracture toughness increase in both FGM reinforced with CNT, but the increase of the hardness and fracture toughness are more pronounced in FGM with micro and nanocrystalline HA.%利用羟基磷灰石(HA)、不锈钢316L(SS316L)和碳纳米管(CNT)制备生物医学植入体用混合功能梯度材料(FGM)。加入SS316L和CNT增强功能梯度材料离散层的HA制成三种不同类型的功能梯度材料。第一种功能梯度材料加入10%~40%(质量分数)的SS316L强化微米HA,浓度梯度为10%。第二种功能梯度材料,在第一种功能梯度材料的基础上加入0.5%(质量分数)的功能化碳纳米管。第三种功能梯度材料在第二种功能梯度材料的基础上加入微米HA和纳米HA(1:1)的混合物。所有类型的功能梯度材料在相似的压缩参数和烧结参数下,进行单轴压缩实验,并采用无压烧结技术进行烧结。结果表明,加入碳纳米管和纳米晶体HA提高了功能梯度材料的致密度。

  1. A Signaling Theory of Grade Inflation

    OpenAIRE

    William Chan; Hao Li; Wing Suen

    2005-01-01

    When employers cannot tell whether a school truly has many good students or just gives easy grades, schools have an incentive to inflate grades to help mediocre students, despite concerns about preserving the value of good grades for good students. We construct a signaling model where grades are inflated in equilibrium. The inability to commit to an honest grading policy reduces the informativeness of grades and hurts schools. Grade inflation by one school makes it easier for another school t...

  2. Predictors of General Chemistry Grades.

    Science.gov (United States)

    Ozsogomonyan, Ardas; Loftus, Drew

    1979-01-01

    Chemistry pretest scores, high school chemistry grades and, to a greater extent, math SAT scores were useful predictors of college general chemistry grades. Regression analysis of all these predictors combined was used to construct an expectancy table which is being used to identify and advise underprepared students. (BB)

  3. Annotated Bibliography, Grades K-6.

    Science.gov (United States)

    Massachusetts Dept. of Education, Boston. Bureau of Nutrition Education and School Food Services.

    This annotated bibliography on nutrition is for the use of teachers at the elementary grade level. It contains a list of books suitable for reading about nutrition and foods for pupils from kindergarten through the sixth grade. Films and audiovisual presentations for classroom use are also listed. The names and addresses from which these materials…

  4. Grading Exceptional and Struggling Learners

    Science.gov (United States)

    Jung, Lee Ann; Guskey, Thomas R.

    2011-01-01

    How can you ensure that you are grading your exceptional students fairly? Teachers receive very little guidance for grading students with disabilities, English learners, and those receiving services through a response-to-intervention (RTI) process. This practitioner-friendly book provides teachers and administrators with an effective framework for…

  5. A vision of graded hemispheric specialization.

    Science.gov (United States)

    Behrmann, Marlene; Plaut, David C

    2015-11-01

    Understanding the process by which the cerebral hemispheres reach their mature functional organization remains challenging. We propose a theoretical account in which, in the domain of vision, faces and words come to be represented adjacent to retinotopic cortex by virtue of the need to discriminate among homogeneous exemplars. Orthographic representations are further constrained to be proximal to typically left-lateralized language-related information to minimize connectivity length between visual and language areas. As reading is acquired, orthography comes to rely more heavily (albeit not exclusively) on the left fusiform region to bridge vision and language. Consequently, due to competition from emerging word representations, face representations that were initially bilateral become lateralized to the right fusiform region (albeit, again, not exclusively). We review recent research that describes constraints that give rise to this graded hemispheric arrangement. We then summarize empirical evidence from a variety of studies (behavioral, evoked response potential, functional imaging) across different populations (children, adolescents, and adults; left handers and individuals with developmental dyslexia) that supports the claims that hemispheric lateralization is graded rather than binary and that this graded organization emerges dynamically over the course of development. Perturbations of this system either during development or in adulthood provide further insights into the principles governing hemispheric organization. PMID:26199998

  6. Contact Mechanics Of Microscopically Rough Surfaces With Graded Elasticity

    OpenAIRE

    Paggi, Marco; Zavarise, Giorgio

    2011-01-01

    Abstract The well-known Greenwood and Williamson contact theory for microscopically homogeneous rough surfaces is generalized by considering functionally graded elastic rough surfaces. In particular, two distinct cases giving rise to a non-constant Young's modulus with depth are considered: (I) an initially plane layered (or graded) solid which is non-uniformly eroded so that the final product is a rough surface with asperities having an elastic modulus depending on the height; and...

  7. Determinants of Grades in Maths for Students in Economics

    OpenAIRE

    Cappellari, Lorenzo; Lucifora, Claudio; Pozzoli, Dario

    2009-01-01

    This paper investigates the determinants of grades achieved in mathematics by rst-year students in Economics. We use individual administrative data from 1993 to 2005 to t an educational production function. Our main ndings suggest that good secondary school achievements and the type of school attended are signi cantly associated with maths grades. Ceteris paribus, females typically do better than males. Since students can postpone the exam or repeat it when they fail, we also analyze the dete...

  8. A review of social grade

    OpenAIRE

    Higgins, Alisa

    1980-01-01

    The report is the result of an investigation by Cranfield School of Management into the effectiveness of social grade as a determinant of buyer behaviour. A study of usership by social grade of a wide range of products and over 10 years was undertaken, and it was found that while social grade discriminates to some extent for most products,it discriminates less well for many areas than it did ten years ago. The reason for this is not a change in the effectiveness of the measure so much as chan...

  9. The Implications of Grade Inflation

    DEFF Research Database (Denmark)

    Smith, David E.; Fleisher, Steven

    2011-01-01

    The authors review current and past practices of the grade inflation controversy and present ways to return to each institution’s established grading guidelines. Students are graded based on knowledge gathered. Certain faculty members use thorough evaluative methods, such as written and oral...... presentations, plus examinations. Others may require only midterm and final examinations; these latter are usually insufficient to measure learning/mastery of course objectives. Supporting this study are profiles from select universities: some have undertaken the gradeinflation controversy academically; others...... have been profiled in the news. The model is provided to ensure that degree candidates are academic experts in their field, having earned the credential through rigorous study....

  10. Graded Recombination Layers for Multijunction Photovoltaics

    KAUST Repository

    Koleilat, Ghada I.

    2012-06-13

    Multijunction devices consist of a stack of semiconductor junctions having bandgaps tuned across a broad spectrum. In solar cells this concept is used to increase the efficiency of photovoltaic harvesting, while light emitters and detectors use it to achieve multicolor and spectrally tunable behavior. In series-connected current-matched multijunction devices, the recombination layers must allow the hole current from one cell to recombine, with high efficiency and low voltage loss, with the electron current from the next cell. We recently reported a tandem solar cell in which the recombination layer was implemented using a progression of n-type oxides whose doping densities and work functions serve to connect, with negligible resistive loss at solar current densities, the constituent cells. Here we present the generalized conditions for design of efficient graded recombination layer solar devices. We report the number of interlayers and the requirements on work function and doping of each interlayer, to bridge an work function difference as high as 1.6 eV. We also find solutions that minimize the doping required of the interlayers in order to minimize optical absorption due to free carriers in the graded recombination layer (GRL). We demonstrate a family of new GRL designs experimentally and highlight the benefits of the progression of dopings and work functions in the interlayers. © 2012 American Chemical Society.

  11. 7 CFR 810.2204 - Grades and grade requirements for wheat.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 7 2010-01-01 2010-01-01 false Grades and grade requirements for wheat. 810.2204... OFFICIAL UNITED STATES STANDARDS FOR GRAIN United States Standards for Wheat Principles Governing the Application of Standards § 810.2204 Grades and grade requirements for wheat. (a) Grades and grade...

  12. Progressive problems higher grade physics

    CERN Document Server

    Kennedy, William

    2001-01-01

    This book fully covers all three Units studied in Scotland's Higher Grade Physics course, providing a systematic array of problems (from the simplest to the most difficult) to lead variously abled pupils to examination success.

  13. Grade 6 Science Curriculum Specifications.

    Science.gov (United States)

    Alberta Dept. of Education, Edmonton. Curriculum Branch.

    This material describes curriculum specifications for grade 6 science in Alberta. Emphases recommended are: (1) process skills (50%); (2) psychomotor skills (10%); (3) attitudes (10%); and (4) subject matter (30%). Priorities within each category are identified. (YP)

  14. Additive manufacturing of graded dielectrics

    International Nuclear Information System (INIS)

    A method for the fabrication of graded dielectrics within a structural composite is presented. This system employs an ultrasonic powder deposition head to print high dielectric powders onto a woven fabric composite substrate. It is shown how this system can integrate 3D variations of dielectric properties at millimeter resolution within a mechanically rugged substrate. To conclude, the system’s practical application is demonstrated with experimental results from a graded index lens. (paper)

  15. Streamlining Grading toward Better Feedback

    OpenAIRE

    Malan, David J.; MacWilliam, Thomas Matthew

    2013-01-01

    CS50 is Harvard University's introductory course aimed at majors and non-majors alike. Each week, students complete programming assignments and have traditionally received feedback from staff in the form of comments on PDFs of their code. Staff have historically reported spending significant amounts of time grading because of bottlenecks that included generating PDF documents and manually emailing feedback to students. Because we preferred that staff spend less of their time on grading logist...

  16. Mucositis Grades and Yeast Species

    OpenAIRE

    Ognjenović, Marina; Milatić, Katja; Parat, Katica; Kovačić, Ivan; Ježina Bušelić, Marina A.; Božić, Joško

    2013-01-01

    Surgically treated patients with oral, head and neck cancer commonly develop mucositis during additional irradiation therapy. Oral mucosa inflammation other than irradiation is mostly caused by Candida albicans, yeast of Candida genus. This study evaluated possible connection between grades of oral mucositis and oral yeast profile in irradiated patients before, during and after irradiation. In 25 examined patients mucosits grades »0« to »2« before irradiation with 20% positive smears and o...

  17. Apple Grading Using Fuzzy Logic

    OpenAIRE

    KAVDIR, İsmail

    2003-01-01

    Classification is vital for the evaluation of agricultural produce. However, the high costs, subjectivity, tediousness and inconsistency associated with manual sorting have been forcing the post harvest industry to apply automation in sorting operations. Fuzzy logic (FL) was applied as a decision making support to grade apples in this study. Quality features such as the color, size and defects of apples were measured through different equipment. The same set of apples was graded by both a hum...

  18. Boundary values as Hamiltonian variables. II. Graded structures

    Science.gov (United States)

    Soloviev, Vladimir O.

    2002-07-01

    It is shown that the new formula for the field theory Poisson brackets arises naturally in the proposed extension of the formal variational calculus incorporating divergences. The linear spaces of local functionals, evolutionary vector fields, functional forms, multi-vectors and differential operators become graded with respect to divergences. The bilinear operations, such as the action of vector fields onto functionals, the commutator of vector fields, the interior product of forms and vectors and the Schouten-Nijenhuis bracket are compatible with the grading. A definition of the adjoint graded operator is proposed and antisymmetric operators are constructed with the help of boundary terms. The fulfilment of the Jacobi identity for the new Poisson brackets is shown to be equivalent to vanishing of the Schouten-Nijenhuis bracket of the Poisson bivector with itself.

  19. Hybrid-microwave sintering of hardmetals and graded oxides composites

    International Nuclear Information System (INIS)

    Commercial WC-Co hardmetal grades and functionally graded ZrO2-AI2O3 ceramic composites were fully densified by means of hybrid microwave sintering in a cylindrical 2.45 GHz single-mode microwave furnace using a tubular susceptor concept. The hybrid sintering approach allowed immediate, smooth, programmable and reproducible thermal cycling of materials which do not couple with microwaves at room temperature. Unequivocal proof of microwave activity on the samples inside the cylindrical SiC susceptor was obtained from microstructural analysis of fast heated oxide ceramics. Densification of continuously graded Zr2-AI2O3 materials could be achieved in shorter sintering times when compared to conventional sintering in air, without influencing the material properties. Hybrid microwave annealing of these composites in an inert atmosphere allowed to increase the fracture toughness of the components significantly. The microstructural properties of commercial hardmetal grades obtained by conventional sintering could be fully reproduced by hybrid microwave sintering. (author)

  20. Grading: Why You Should Trust Your Judgment

    Science.gov (United States)

    Guskey, Thomas R.; Jung, Lee Ann

    2016-01-01

    Many educators consider grades calculated from statistical algorithms more accurate, objective, and reliable than grades they calculate themselves. But in this research, the authors first asked teachers to use their professional judgment to choose a summary grade for hypothetical students. When the researchers compared the teachers' grade with the…

  1. Dynamics of Peer Grading: An Empirical Study

    OpenAIRE

    Alfaro, L; Shavlovsky, M

    2016-01-01

    Peer grading is widely used in MOOCs and in standard university settings. The quality of grades obtained via peer grading is essential for the educational process. In this work, we study the factors that influence errors in peer grading. We analyze 288 assignments with 25,633 submissions and 113,169 reviews conducted with CrowdGrader, a web based peer grading tool. First, we found that large grading errors are generally more closely correlated with hard-to-grade submission, rather than ...

  2. On the union of graded prime ideals

    Directory of Open Access Journals (Sweden)

    Uregen Rabia Nagehan

    2016-04-01

    Full Text Available In this paper we investigate graded compactly packed rings, which is defined as; if any graded ideal I of R is contained in the union of a family of graded prime ideals of R, then I is actually contained in one of the graded prime ideals of the family. We give some characterizations of graded compactly packed rings. Further, we examine this property on h – Spec(R. We also define a generalization of graded compactly packed rings, the graded coprimely packed rings. We show that R is a graded compactly packed ring if and only if R is a graded coprimely packed ring whenever R be a graded integral domain and h – dim R = 1.

  3. Selective nonoperative management of high grade splenic trauma.

    Science.gov (United States)

    Branco, Bernardino C; Tang, Andrew L; Rhee, Peter; Fraga, Gustavo Pereira; Nascimento, Bartolomeu; Rizoli, Sandro; O'Keeffe, Terence

    2013-01-01

    The "Evidence-based Telemedicine - Trauma & Acute Care Surgery" (EBT-TACS) Journal Club performed a critical review of the literature and selected three up-to-date articles on the management of splenic trauma. Our focus was on high-grade splenic injuries, defined as AAST injury grade III-V. The first paper was an update of the 2003 Eastern Association for the Surgery of Trauma (EAST) practice management guidelines for nonoperative management of injury to the spleen. The second paper was an American Association for the Surgery of Trauma (AAST) 2012 plenary paper evaluating the predictive role of contrast blush on CT scan in AAST grade IV and V splenic injuries. Our last article was from Europe and investigates the effects of angioembolization of splenic artery on splenic function after high-grade splenic trauma (AAST grade III-V). The EBT-TACS Journal Club elaborated conclusions and recommendations for the management of high-grade splenic trauma. PMID:23912375

  4. Geological Modeling of Gold Deposit Based on Grade Domaining Using Plurigaussian Simulation Technique

    International Nuclear Information System (INIS)

    Mineral resource evaluation requires defining grade domains of an ore deposit. Common practice in mineral resource estimation consists of partitioning the ore body into several grade domains before the geostatistical modeling and estimation at unsampled locations. Many ore deposits are made up of different mineralogical ensembles such as oxide and sulfide zone: being able to model the spatial layout of the different grades is vital to good mine planning and management. This study addresses the application of the plurigaussian simulation to Sivas (Turkey) gold deposits for constructing grade domain models that reproduce the contacts between different grade domains in accordance with geologist’s interpretation. The method is based on the relationship between indicator variables from grade distributions on the Gaussian random functions chosen to represent them. Geological knowledge is incorporated into the model by the definition of the indicator variables, their truncation strategy, and the grade domain proportions. The advantages of the plurigaussian simulation are exhibited through the case study. The results indicated that the processes are seen to respect reproducing complex geometrical grades of an ore deposit by means of simulating several grade domains with different spatial structure and taking into account their global proportions. The proposed proportion model proves as simple to use in resource estimation, to account for spatial variations of the grade characteristics and their distribution across the studied area, and for the uncertainty in the grade domain proportions. The simulated models can also be incorporated into mine planning and scheduling.

  5. 7 CFR 810.1005 - Special grades and special grade requirements.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 7 2010-01-01 2010-01-01 false Special grades and special grade requirements. 810... Special Grade Requirements § 810.1005 Special grades and special grade requirements. (a) Bleached oats...) Bright oats. Oats, except bleached oats, that are of good natural color. (c) Ergoty oats. Oats...

  6. 基于灰AHP-白化权函数聚类评定法的多元精细化猪胴体分级方法研究%Study on multielement precise pig carcass grading methods based on grey AHP- whiten function clustering evaluation method

    Institute of Scientific and Technical Information of China (English)

    冷晟; 孙志超; 马万太

    2015-01-01

    提出的一种适用于自动化生猪屠宰线上的,多元、精细、智能化胴体肉品分级方法,创新性引入生猪养殖过程中饲料投喂与喂药信息,并采用适用于屠宰生产线上自动检测装置,快速有效地获取屠宰过程中胴体参数,依据生猪养殖信息、胴体特性和肉质特性这三类信息建立两阶段分级模型,采用灰色AHP-白化权函数聚类综合分级评定模型进行猪胴体肉品综合智能分级。使得猪胴肉品分级更加合理科学,适合中国生猪品种,易于推广,适用于现代化大规模自动化屠宰生产线。%A multiple indexes, refinement and intelligent pig carcass grading method had been pro⁃posed which could be adopted in modern automatic pig slaughtering line. The feed and medicine informa⁃tion of pigs breeding process was innovatively introduced. The automatic detection equipments which ap⁃plied to slaughtering line were used. The carcass parameters could be collected quickly and efficiently from slaughtering process. According to three kinds of information of breeding information, carcass char⁃acteristics and meat quality characteristics, the carcass grading model was set into two phases. AHP-Grey Whiten Function Clustering Evaluation Method was used to grade pig carcass quality. It made the carcass grading more reasonable. It is suitable for Chinese pig and easy to spread. It is suitable for large scale automation slaughtering production line.

  7. [Grading of gynecological tumors : Current aspects].

    Science.gov (United States)

    Horn, L-C; Mayr, D; Brambs, C E; Einenkel, J; Sändig, I; Schierle, K

    2016-07-01

    Histopathological assessment of the tumor grade and cell type is central to the management and prognosis of various gynecological malignancies. Conventional grading systems for squamous carcinomas and adenocarcinomas of the vulva, vagina and cervix are poorly defined. For endometrioid tumors of the female genital tract as well as for mucinous endometrial, ovarian and seromucinous ovarian carcinomas, the 3‑tiered FIGO grading system is recommended. For uterine neuroendocrine tumors the grading system of the gastrointestinal counterparts has been adopted. Uterine leiomyosarcomas are not graded. Endometrial stromal sarcomas are divided into low and high grades, based on cellular morphology, immunohistochemical and molecular findings. A chemotherapy response score was established for chemotherapeutically treated high-grade serous pelvic cancer. For non-epithelial ovarian malignancies, only Sertoli-Leydig cell tumors and immature teratomas are graded. At this time molecular profiling has no impact on the grading of tumors of the female genital tract. PMID:27379622

  8. School Grading and Institutional Contexts

    Science.gov (United States)

    Dardanoni, Valentino; Modica, Salvatore; Pennisi, Aline

    2011-01-01

    We study how the relationship between students' cognitive ability and their school grades depends on institutional contexts. In a simple abstract model, we show that unless competence standards are set at above-school level or the variation of competence across schools is low, students' competence valuation will be heterogeneous, with weaker…

  9. The Ninth-Grade Challenge

    Science.gov (United States)

    Habeeb, Scott

    2013-01-01

    Across the country, high schools have found that their ninth-grade students have the highest rates of truancy, discipline referrals, failures, and retentions. A school's worst data points are usually found among freshmen. For this reason, proactive schools seek strategies for transitioning freshmen into high school. An effective freshman…

  10. Elementary School Dance. Grade Six.

    Science.gov (United States)

    Wotherspoon, Bill

    Outlines are presented for 30 creative dance lessons for sixth grade children. Each lesson description includes: (1) a statement of the lesson objective; (2) an overview of how the lesson illuminates a general concept of dancing; (3) musical equipment needed; (4) introductory activities; (5) tasks for skill development; (6) suggestions for the…

  11. Elementary School Dance. Grade One.

    Science.gov (United States)

    Wotherspoon, Bill

    Outlines are presented for 30 creative dance lessons for first grade children. Each lesson description includes: (1) a statement of the lesson objective; (2) an overview of how the lesson illuminates a general concept of dancing; (3) musical equipment needed; (4) introductory activities; (5) tasks for skill development; (6) suggestions for the…

  12. Elementary School Dance. Grade Two.

    Science.gov (United States)

    Wotherspoon, Bill

    Outlines are presented for 30 creative dance lessons for second grade children. Each lesson description includes: (1) a statement of the lesson objective; (2) an overview of how the lesson illuminates a general concept of dancing; (3) musical equipment needed; (4) introductory activities; (5) tasks for skill development; (6) suggestions for the…

  13. Elementary School Dance. Grade Three.

    Science.gov (United States)

    Wotherspoon, Bill

    Outlines are presented for 30 creative dance lessons for third grade children. Each lesson description includes: (1) a statement of the lesson objective; (2) an overview of how the lesson illuminates a general concept of dancing; (3) musical equipment needed; (4) introductory activities; (5) tasks for skill development; (6) suggestions for the…

  14. Tumor diagnosis, grading, and staging

    International Nuclear Information System (INIS)

    Optimal use of radiation therapy for the treatment of animal tumors necessitates accurate clinical evaluation, diagnostic imaging, and pathology. This requires a coordinated effort between the clinical and radiation oncologist, radiologist, and pathologist. The histological appearance of the tumor, tumor grade, and tumor stage are important diagnostic criteria that need to be established. Diagnostic imaging, including radiographic, computerized tomographic, magnetic resonance imaging, and ultrasound studies are helpful in establishing an accurate tumor location and diagnosis. Biopsy and histological examination of tumor tissue are necessary for final diagnosis of tumor type. Determination of tumor type is critical because different tumor types vary in regard to radiosensitivity, local behavior, and propensity for regional and systemic metastasis. The histological grade of many tumors is an important indicator of the potential for local invasion or systemic metastases, and may influence treatment response. Tumor staging as determined by clinical evaluation, imaging studies, and histological evaluation is necessary to establish the extent of the tumor, both locally, regionally, and systemically. The clinical oncologist should have an understanding of the procedures involved in tumor diagnosis, tumor grading, and tumor staging. This provides a better understanding of the neoplastic condition and recognition of the limitations of diagnostic procedures. Tumor type, grade, and stage all impact radiation treatment planning and the need for adjuvant regional or systemic therapy

  15. Senegal : Early Grade Reading Assessment

    OpenAIRE

    Sprenger-Charolles, Liliane

    2008-01-01

    In international assessments (Progress in International Reading Literacy Study - Organization for Economic Co-operation and Development [PISA-OECD] and Progress in International Reading Literacy Study International Evaluation of Educational Achievement [PIRLS-IEA]), children's reading skills are not assessed before the fourth grade. For students who are poor readers, it is often too late b...

  16. Student Grade Expectations at Technical College, 2-, and 4-Year Institutions

    Science.gov (United States)

    McCann, Lee I.; Immel, Kathy R.; Kadah-Ammeter, Tammy L.; Priniski, Stacy J.

    2013-01-01

    Although students' final course grade expectations have been the focus of several studies, none have looked systematically at students' expectations for grade distributions for the whole class across institutional types, student year in school, and course levels. This study examined such differences as a function of gender, course level,…

  17. Strength grading of structural timber in different grade combinations

    OpenAIRE

    Plos, Mitja

    2012-01-01

    Good knowledge of the characteristics of building material is of the utmost importance in static calculations in civil engineering. The characteristics of a piece of timber may vary depending on the growth area, log, and cutting. Therefore, each piece of timber should be examined separately. The examination is based on non-destructive testing, distinguishing – as in our case – between different strength grades. Eurocode 5 refers to the EN 14081 standard, which allows visual and...

  18. Almost-graded central extensions of Lax operator algebra

    CERN Document Server

    Schlichenmaier, Martin

    2011-01-01

    Lax operator algebras constitute a new class of infinite dimensional Lie algebras of geometric origin. More precisely, they are algebras of matrices whose entries are meromorphic functions on a compact Riemann surface. They generalize classical current algebras and current algebras of Krichever-Novikov type. Lax operators for $\\gl(n)$, with the spectral parameter on a Riemann surface, were introduced by Krichever. In joint works of Krichever and Sheinman their algebraic structure was revealed and extended to more general groups. These algebras are almost-graded. In this article their definition is recalled and classification and uniqueness results for almost-graded central extensions for this new class of algebras are presented. The explicit forms of the defining cocycles are given. If the finite-dimensional Lie algebra on which the Lax operator algebra is based is simple then, up to equivalence and rescaling of the central element, there is a unique non-trivial almost-graded central extension. These results ...

  19. Grading of quality assurance requirements

    International Nuclear Information System (INIS)

    The present Manual provides guidance and illustrative examples for applying a method by which graded quality assurance requirements may be determined and adapted to the items and services of a nuclear power plant in conformance with the requirements of the IAEA Nuclear Safety Standards (NUSS) Code and Safety Guides on quality assurance. The Manual replaces the previous publication IAEA-TECDOC-303 on the same subject. Various methods of grading quality assurance are available in a number of Member States. During the development of the present Manual it was not considered practical to attempt to resolve the differences between those methods and it was preferred to identify and benefit from the good practices available in all the methods. The method presented in this Manual deals with the aspects of management, documentation, control, verification and administration which affect quality. 1 fig., 4 tabs

  20. SUSY gauge theory on graded manifolds

    OpenAIRE

    Sardanashvily, G.; Wachowski, W.

    2014-01-01

    Lagrangian classical field theory of even and odd fields is adequately formulated in terms of fibre bundles and graded manifolds. In particular, conventional Yang-Mills gauge theory is theory of connections on smooth principal bundles, but its BRST extension involves odd ghost fields an antifields on graded manifolds. Here, we formulate Yang-Mills theory of Grassmann-graded gauge fields associated to Lie superalgebras on principal graded bundles. A problem lies in a geometric definition of od...