The ex-situ incorporation of the secondary SiC reinforcement,along with the in-situ incorporation of the tertiary and quaternary Mg_(3)N_(2) and Si_(3)N_(4) phases,in the primary matrix of Mg_(2)Si is employed in orde...The ex-situ incorporation of the secondary SiC reinforcement,along with the in-situ incorporation of the tertiary and quaternary Mg_(3)N_(2) and Si_(3)N_(4) phases,in the primary matrix of Mg_(2)Si is employed in order to provide ultimate wear resistance based on the laser-irradiation-induced inclusion of N_(2) gas during laser powder bed fusion.This is substantialized based on both the thermal diffusion-and chemical reactionbased metallurgy of the Mg_(2)Si–SiC/nitride hybrid composite.This study also proposes a functional platform for systematically modulating a functionally graded structure and modeling build-direction-dependent architectonics during additive manufacturing.This strategy enables the development of a compositional gradient from the center to the edge of each melt pool of the Mg_(2)Si–SiC/nitride hybrid composite.Consequently,the coefficient of friction of the hybrid composite exhibits a 309.3%decrease to–1.67 compared to–0.54 for the conventional nonreinforced Mg_(2)Si structure,while the tensile strength exhibits a 171.3%increase to 831.5 MPa compared to 485.3 MPa for the conventional structure.This outstanding mechanical behavior is due to the(1)the complementary and synergistic reinforcement effects of the SiC and nitride compounds,each of which possesses an intrinsically high hardness,and(2)the strong adhesion of these compounds to the Mg_(2)Si matrix despite their small sizes and low concentrations.展开更多
Buckling and postbuckling characteristics of laminated graphene-enhanced composite(GEC)truncated conical shells exposed to torsion under temperature conditions using finite element method(FEM)simulation are presented ...Buckling and postbuckling characteristics of laminated graphene-enhanced composite(GEC)truncated conical shells exposed to torsion under temperature conditions using finite element method(FEM)simulation are presented in this study.In the thickness direction,the GEC layers of the conical shell are ordered in a piece-wise arrangement of functionally graded(FG)distribution,with each layer containing a variable volume fraction for graphene reinforcement.To calculate the properties of temperaturedependent material of GEC layers,the extended Halpin-Tsai micromechanical framework is used.The FEM model is verified via comparing the current results obtained with the theoretical estimates for homogeneous,laminated cylindrical,and conical shells,the FEM model is validated.The computational results show that a piece-wise FG graphene volume fraction distribution can improve the torque of critical buckling and torsional postbuckling strength.Also,the geometric parameters have a critical impact on the stability of the conical shell.However,a temperature rise can reduce the crucial torsional buckling torque as well as the GEC laminated truncated conical shell’s postbuckling strength.展开更多
In this study,the first-order shear deformation theory(FSDT)is used to establish a nonlinear dynamic model for a conical shell truncated by a functionally graded graphene platelet-reinforced composite(FG-GPLRC).The vi...In this study,the first-order shear deformation theory(FSDT)is used to establish a nonlinear dynamic model for a conical shell truncated by a functionally graded graphene platelet-reinforced composite(FG-GPLRC).The vibration analyses of the FG-GPLRC truncated conical shell are presented.Considering the graphene platelets(GPLs)of the FG-GPLRC truncated conical shell with three different distribution patterns,the modified Halpin-Tsai model is used to calculate the effective Young’s modulus.Hamilton’s principle,the FSDT,and the von-Karman type nonlinear geometric relationships are used to derive a system of partial differential governing equations of the FG-GPLRC truncated conical shell.The Galerkin method is used to obtain the ordinary differential equations of the truncated conical shell.Then,the analytical nonlinear frequencies of the FG-GPLRC truncated conical shell are solved by the harmonic balance method.The effects of the weight fraction and distribution pattern of the GPLs,the ratio of the length to the radius as well as the ratio of the radius to the thickness of the FG-GPLRC truncated conical shell on the nonlinear natural frequency characteristics are discussed.This study culminates in the discovery of the periodic motion and chaotic motion of the FG-GPLRC truncated conical shell.展开更多
The nonlinear stability of sandwich cylindrical shells comprising porous functionally graded material(FGM) and carbon nanotube reinforced composite(CNTRC)layers subjected to uniform temperature rise is investigated. T...The nonlinear stability of sandwich cylindrical shells comprising porous functionally graded material(FGM) and carbon nanotube reinforced composite(CNTRC)layers subjected to uniform temperature rise is investigated. Two sandwich models corresponding to CNTRC and FGM face sheets are proposed. Carbon nanotubes(CNTs) in the CNTRC layer are embedded into a matrix according to functionally graded distributions. The effects of porosity in the FGM and the temperature dependence of properties of all constituent materials are considered. The effective properties of the porous FGM and CNTRC are determined by using the modified and extended versions of a linear mixture rule, respectively. The basic equations governing the stability problem of thin sandwich cylindrical shells are established within the framework of the Donnell shell theory including the von K’arm’an-Donnell nonlinearity. These equations are solved by using the multi-term analytical solutions and the Galerkin method for simply supported shells.The critical buckling temperatures and postbuckling paths are determined through an iteration procedure. The study reveals that the sandwich shell model with a CNTRC core layer and relatively thin porous FGM face sheets can have the best capacity of thermal load carrying. In addition, unlike the cases of mechanical loads, porosities have beneficial effects on the nonlinear stability of sandwich shells under the thermal load. It is suggested that an appropriate combination of advantages of FGM and CNTRC can result in optimal efficiency for advanced sandwich structures.展开更多
The purpose of the present study is to examine the impact of initial geometric imperfection on the nonlinear dynamical characteristics of functionally graded carbon nanotube-reinforced composite(FG-CNTRC) rectangular ...The purpose of the present study is to examine the impact of initial geometric imperfection on the nonlinear dynamical characteristics of functionally graded carbon nanotube-reinforced composite(FG-CNTRC) rectangular plates under a harmonic excitation transverse load. The considered plate is assumed to be made of matrix and single-walled carbon nanotubes(SWCNTs). The rule of mixture is employed to calculate the effective material properties of the plate. Within the framework of the parabolic shear deformation plate theory with taking the influence of transverse shear deformation and rotary inertia into account, Hamilton’s principle is utilized to derive the geometrically nonlinear mathematical formulation including the governing equations and corresponding boundary conditions of initially imperfect FG-CNTRC plates. Afterwards, with the aid of an efficient multistep numerical solution methodology, the frequency-amplitude and forcing-amplitude curves of initially imperfect FG-CNTRC rectangular plates with various edge conditions are provided, demonstrating the influence of initial imperfection,geometrical parameters, and edge conditions. It is displayed that an increase in the initial geometric imperfection intensifies the softening-type behavior of system, while no softening behavior can be found in the frequency-amplitude curve of a perfect plate.展开更多
This paper presents an analytical solution for the free vibration behavior of functionally graded carbon nanotube-reinforced composite(FG-CNTRC) doubly curved shallow shells with integrated piezoelectric layers. Here,...This paper presents an analytical solution for the free vibration behavior of functionally graded carbon nanotube-reinforced composite(FG-CNTRC) doubly curved shallow shells with integrated piezoelectric layers. Here, the linear distribution of electric potential across the thickness of the piezoelectric layer and five different types of carbon nanotube(CNT) distributions through the thickness direction are considered. Based on the four-variable shear deformation refined shell theory, governing equations are obtained by applying Hamilton's principle. Navier's solution for the shell panels with the simply supported boundary condition at all four edges is derived. Several numerical examples validate the accuracy of the presented solution. New parametric studies regarding the effects of different material properties, shell geometric parameters, and electrical boundary conditions on the free vibration responses of the hybrid panels are investigated and discussed in detail.展开更多
Compositionally graded composite of alumina-20%zirconia (volume fraction) was fabricated by using centrifugal casting incorporated with relatively thin slip. An EPMA analysis exhibited a nearly linear variation of the...Compositionally graded composite of alumina-20%zirconia (volume fraction) was fabricated by using centrifugal casting incorporated with relatively thin slip. An EPMA analysis exhibited a nearly linear variation of the alumina/zirconia ratio along the centrifugal direction; zirconia tended to accumulate in the bottom section, while alumina in the top section. Such a graded structure exhibited a considerably higher flexural strength when the alumina rich surface was subjected to a tensile stress than compositionally uniform composite of the same average composition. Fracture toughness measurement across the specimen thickness by indentation method revealed that the crack lengths along the vertical and horizontal directions were different. The anisotropy of the fracture toughness was accounted for by the variation of the residual stress across the specimen thickness.展开更多
W/Cu functionally gradient material (FGM) has excellent mechanical properties since it can effectively relax interlayer thermal stresses caused by the mismatch between their thermal expansion coefficients. W/Cu FGM co...W/Cu functionally gradient material (FGM) has excellent mechanical properties since it can effectively relax interlayer thermal stresses caused by the mismatch between their thermal expansion coefficients. W/Cu FGM combines the advantages of tungsten such as high melting point and service strength, with heat conductivity and plasticity of copper at room temperature. Thus it demonstrates satisfactory heat corrosion 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 (0-100%W) has been successfully fabricated. Suitable amount of transition metals (such as nickel, zirconium, vanadium) is employed as additives to activate tungsten's sintering, enhance phase wettability and bonding strength between W and Cu. Densification effects of different layer of FGM were investigated. Microstructure morphology and interface elements distribution were observed and analyzed. The thermal shock performance of W/Cu FGM was also preliminarily tested.展开更多
This study presents the size-dependent nonlinear thermal postbuckling characteristics of a porous functionally graded material(PFGM) microplate with a central cutout with various shapes using isogeometric numerical te...This study presents the size-dependent nonlinear thermal postbuckling characteristics of a porous functionally graded material(PFGM) microplate with a central cutout with various shapes using isogeometric numerical technique incorporating nonuniform rational B-splines. To construct the proposed non-classical plate model, the nonlocal strain gradient continuum elasticity is adopted on the basis of a hybrid quasithree-dimensional(3D) plate theory under through-thickness deformation conditions by only four variables. By taking a refined power-law function into account in conjunction with the Touloukian scheme, the temperature-porosity-dependent material properties are extracted. With the aid of the assembled isogeometric-based finite element formulations,nonlocal strain gradient thermal postbuckling curves are acquired for various boundary conditions as well as geometrical and material parameters. It is portrayed that for both size dependency types, by going deeper in the thermal postbuckling domain, gaps among equilibrium curves associated with various small scale parameter values get lower, which indicates that the pronounce of size effects reduces by going deeper in the thermal postbuckling regime. Moreover, we observe that the central cutout effect on the temperature rise associated with the thermal postbuckling behavior in the presence of the effect of strain gradient size and absence of nonlocality is stronger compared with the case including nonlocality in absence of the strain gradient small scale effect.展开更多
This paper analyzes the nonlocal thermal buckling and postbuckling behaviors of a multi-layered graphene nanoplatelet(GPL)reinforced piezoelectric micro-plate.The GPLs are supposed to disperse as a gradient pattern in...This paper analyzes the nonlocal thermal buckling and postbuckling behaviors of a multi-layered graphene nanoplatelet(GPL)reinforced piezoelectric micro-plate.The GPLs are supposed to disperse as a gradient pattern in the composite micro-plate along its thickness.The effective material properties are calculated by the Halpin-Tsai parallel model and mixture rule for the functionally graded GPL reinforced piezoelectric(FG-GRP)micro-plate.Governing equations for the nonlocal thermal buckling and postbuckling behaviors of the FG-GRP micro-plate are obtained by the first-order shear deformation theory,the von Kármán nonlinear theory,and the minimum potential energy principle.The differential quadrature(DQ)method and iterative method are introduced to numerically analyze the effects of the external electric voltage,the distribution pattern and characteristic of GPLs,and the nonlocal parameter on the critical buckling behaviors and postbuckling equilibrium path of the FG-GRP micro-plate in thermal environment.展开更多
In this paper,we propose a specific two-layer model consisting of a functionally graded(FG)layer and a piezoelectric semiconductor(PS)layer.Based on the macroscopic theory of PS materials,the effects brought about by ...In this paper,we propose a specific two-layer model consisting of a functionally graded(FG)layer and a piezoelectric semiconductor(PS)layer.Based on the macroscopic theory of PS materials,the effects brought about by the attached FG layer on the piezotronic behaviors of homogeneous n-type PS fibers and PN junctions are investigated.The semi-analytical solutions of the electromechanical fields are obtained by expanding the displacement and carrier concentration variation into power series.Results show that the antisymmetry of the potential and electron concentration distributions in homogeneous n-type PS fibers is destroyed due to the material inhomogeneity of the attached FG layer.In addition,by creating jump discontinuities in the material properties of the FG layer,potential barriers/wells can be produced in the middle of the fiber.Similarly,the potential barrier configuration near the interface of a homogeneous PS PN junction can also be manipulated in this way,which offers a new choice for the design of PN junction based devices.展开更多
Wear-driven tool failure is one of the main hurdles in the industry.This issue can be addressed through surface coating with ceramic-reinforced metal matrix composites.However,the maximum ceramic content is limited by...Wear-driven tool failure is one of the main hurdles in the industry.This issue can be addressed through surface coating with ceramic-reinforced metal matrix composites.However,the maximum ceramic content is limited by cracking.In this work,the tribological behaviour of the functionally graded WC-ceramic-particlereinforced Stellite 6 coatings is studied.To that end,the wear resistance at room temperature and 400°C is investigated.Moreover,the tribological analysis is supported by crack sensitivity and hardness evaluation,which is of utmost importance in the processing of composite materials with ceramic-particle-reinforcement.Results indicate that functionally graded materials can be employed to increase the maximum admissible WC content,hence improving the tribological behaviour,most notably at high temperatures.Additionally,a shift from abrasive to oxidative wear is observed in high-temperature wear testing.展开更多
In INs study, the fabrication of multilayer AI(Zn)-A1203 with different volume fractions of A1203 was investigated. A1 and ZnO powders were milled by a plaaetaxy ball mill, after which five-layer functionally graded...In INs study, the fabrication of multilayer AI(Zn)-A1203 with different volume fractions of A1203 was investigated. A1 and ZnO powders were milled by a plaaetaxy ball mill, after which five-layer functionally graded samples were produced flarough hot pressing at 580~C and 90 MPa pressure for 30 min. Formation of reinforcing A1203 particles occurred in the aluminum matrix via the aluminolkermic reaction. Determination of the ignition temperature of the aluminolkennic reaction was accomplished using differential lkermal and lkermo- gravimelric amlyses. Scaaming electron microscopy, energy dispersive spectroscopy, and X-ray diffractometery amlyses were utilized to characterize the specimens. The lkermal amlysis results showed that the ignition temperatures for the aluminolkennic reaction of layers with the highest and lowest ZnO contents were 667 and 670~C, respectively. Microslxuctural observation and chemical amlysis confirmed the fa- brication of AI(Zn)-A1203 functionally graded materials composites with precipitation of additional Zn in the matrix. Moreover, nearly dense functionally graded samples demonstrated minimum and maximum hacdness values of HV 75 and HV 130, respectively.展开更多
A new approach for fabricating B4C/Cu graded composite by rapid self-resistance sintering under ultra-high pressure was presented, by which a near dense B4C/Cu graded composite with a compositional spectrum of 0-100% ...A new approach for fabricating B4C/Cu graded composite by rapid self-resistance sintering under ultra-high pressure was presented, by which a near dense B4C/Cu graded composite with a compositional spectrum of 0-100% was successfully fabricated. Plasma relevant performances of sintered B4C/Cu composite were preliminarily characterized, it is found that its chemical sputtering yield is 70% lower than that of SMF800 nuclear graphite under 2.7keV D+ irradiation, and almost no damages after 66 shots of in situ plasma discharge in HL-1 Tokamak facility, which indicates B4C/Cu plasma facing component has a good physical and chemical sputtering resistance performance compared with nuclear graphite.展开更多
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 t...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.展开更多
The objective of present work is to apply the friction stir processing (FSP) to fabricate functionally graded SiC particulate reinforced Al6061 composite and investigate the effect of SiC particle mass fraction dist...The objective of present work is to apply the friction stir processing (FSP) to fabricate functionally graded SiC particulate reinforced Al6061 composite and investigate the effect of SiC particle mass fraction distribution on the mechanical properties and wear behavior ofAl6061/SiC composite. Regarding the obtained results in this work, with increasing SiC mass fraction, elongation decreased, but hardness enhanced. However, the optimized functionally graded composite with the highest tensile strength and wear resistance was achieved for composite with 10 wt% surface SiC. Also, the results showed that wear resistance and tensile strength decreased for composite with 13 wt% surface SiC, due to reinforcement particle clustering depending on high SiC mass fraction.展开更多
In the last decade,the functionally graded carbon nanotube reinforced composites(FG-CNTRCs)have attracted considerable interest due to their excellent mechanical properties,and the structures made of FG-CNTRCs have fo...In the last decade,the functionally graded carbon nanotube reinforced composites(FG-CNTRCs)have attracted considerable interest due to their excellent mechanical properties,and the structures made of FG-CNTRCs have found broad potential applications in aerospace,civil and ocean engineering,automotive industry,and smart structures.Here we review the literature regarding the mechanical analysis of bulk CNTR nanocomposites and FG-CNTRC structures,aiming to provide a clear picture of the mechanical modeling and properties of FG-CNTRCs as well as their composite structures.The review is organized as follows:(1)a brief introduction to the functionally graded materials(FGM),CNTRCs and FG-CNTRCs;(2)a literature review of the mechanical modeling methodologies and properties of bulk CNTRCs;(3)a detailed discussion on the mechanical behaviors of FG-CNTRCs;and(4)conclusions together with a suggestion of future research trends.展开更多
Copper matrix composites have received more attentions as possible candidate for thermal and electrical conductive materials to be used in electrical contact applications. In this study, five-layered Cu/YSZ (yttria-s...Copper matrix composites have received more attentions as possible candidate for thermal and electrical conductive materials to be used in electrical contact applications. In this study, five-layered Cu/YSZ (yttria-stabilized zirconia) functionally graded material (FGM) and copper matrix composite specimens containing 3 and 5 vol% YSZ particles plus pure Cu specimen were synthesized using powder metallurgy (PM) route and spark plasma sintering (SPS) consolidation process. The microstructural and some physical, mechanical features of all specimens were characterized. Microscopic examinations showed that ultrafine YSZ particles were distributed in the copper matrix almost homoge- neously. An appropriate interface was observed at each layer of FGM. The density measurement indicated that the graded structure of the composite could be well densified after the SPS process. The microhardness values of various layers of Cu/ YSZ FGM specimen were gradually altered from 56.3 (pure copper side) to 75.2 HV (Cu-5 vol% YSZ side). The increase of YSZ content resulted in a decrease in electrical conductivity. Additionally, thermal conductivity of Cu/YSZ FGM specimen [308.0 W/(m K)] was determined to be higher than that of the Cu-5 vol% YSZ composite specimen [260.7 W/ (m K)]. Accordingly, it can be concluded that the Cu/YSZ FGM can be a good candidate for the electrical applications, like sliding electrical contacts, where different material characteristics in the same component are required.展开更多
This paper proposes a new Deep Feed-forward Neural Network(DFNN)approach for damage detection in functionally graded carbon nanotube-reinforced composite(FG-CNTRC)plates.In the proposed approach,the DFNN model is deve...This paper proposes a new Deep Feed-forward Neural Network(DFNN)approach for damage detection in functionally graded carbon nanotube-reinforced composite(FG-CNTRC)plates.In the proposed approach,the DFNN model is developed based on a data set containing 20000 samples of damage scenarios,obtained via finite element(FE)simulation,of the FG-CNTRC plates.The elemental modal kinetic energy(MKE)values,calculated from natural frequencies and translational nodal displacements of the structures,are utilized as input of the DFNN model while the damage locations and corresponding severities are considered as output.The state-of-the art Exponential Linear Units(ELU)activation function and the Adamax algorithm are employed to train the DFNN model.Additionally,in order to enhance the performance of the DFNN model,the mini-batch and early-stopping techniques are applied to the training process.A trial-and-error procedure is implemented to determine suitable parameters of the network such as the number of hidden layers and the number of neurons in each layer.The accuracy and capability of the proposed DFNN model are illustrated through two distinct configurations of the CNT-fibers constituting the FG-CNTRC plates including uniform distribution(UD)and functionally graded-V distribution(FG-VD).Furthermore,the performance and stability of the DFNN model with the consideration of noise effects on the input data are also investigated.Obtained results indicate that the proposed DFNN model is able to give sufficiently accurate damage detection outcomes for the FG-CNTRC plates for both cases of noise-free and noise-influenced data.展开更多
基金supported by the Learning & Academic Research Institution for Master’s and Ph.D. Students and Postdocs (LAMP) Program of the National Research Foundation of Korea (NRF) grant funded by the Ministry of Education (No. RS-2023-00285353)supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIP) (NRF-2021R1A2C3006662, NRF-2022R1A5A1030054, and 2021R1A2C1091301)+3 种基金the support from Natural Sciences and Engineering Research Council of Canada (NSERC)Canada Foundation for Innovation (CFI)Atlantic Canada Opportunities Agency (ACOA)the New Brunswick Innovation Foundation (NBIF)
文摘The ex-situ incorporation of the secondary SiC reinforcement,along with the in-situ incorporation of the tertiary and quaternary Mg_(3)N_(2) and Si_(3)N_(4) phases,in the primary matrix of Mg_(2)Si is employed in order to provide ultimate wear resistance based on the laser-irradiation-induced inclusion of N_(2) gas during laser powder bed fusion.This is substantialized based on both the thermal diffusion-and chemical reactionbased metallurgy of the Mg_(2)Si–SiC/nitride hybrid composite.This study also proposes a functional platform for systematically modulating a functionally graded structure and modeling build-direction-dependent architectonics during additive manufacturing.This strategy enables the development of a compositional gradient from the center to the edge of each melt pool of the Mg_(2)Si–SiC/nitride hybrid composite.Consequently,the coefficient of friction of the hybrid composite exhibits a 309.3%decrease to–1.67 compared to–0.54 for the conventional nonreinforced Mg_(2)Si structure,while the tensile strength exhibits a 171.3%increase to 831.5 MPa compared to 485.3 MPa for the conventional structure.This outstanding mechanical behavior is due to the(1)the complementary and synergistic reinforcement effects of the SiC and nitride compounds,each of which possesses an intrinsically high hardness,and(2)the strong adhesion of these compounds to the Mg_(2)Si matrix despite their small sizes and low concentrations.
文摘Buckling and postbuckling characteristics of laminated graphene-enhanced composite(GEC)truncated conical shells exposed to torsion under temperature conditions using finite element method(FEM)simulation are presented in this study.In the thickness direction,the GEC layers of the conical shell are ordered in a piece-wise arrangement of functionally graded(FG)distribution,with each layer containing a variable volume fraction for graphene reinforcement.To calculate the properties of temperaturedependent material of GEC layers,the extended Halpin-Tsai micromechanical framework is used.The FEM model is verified via comparing the current results obtained with the theoretical estimates for homogeneous,laminated cylindrical,and conical shells,the FEM model is validated.The computational results show that a piece-wise FG graphene volume fraction distribution can improve the torque of critical buckling and torsional postbuckling strength.Also,the geometric parameters have a critical impact on the stability of the conical shell.However,a temperature rise can reduce the crucial torsional buckling torque as well as the GEC laminated truncated conical shell’s postbuckling strength.
基金Project supported by the National Natural Science Foundation of China(Nos.12002057,11872127,11832002)the Scientific Research Project of Beijing Educational Committee(No.KM202111232023)the Qin Xin Talents Cultivation Program,Beijing Information Science&Technology University(Nos.QXTCP C202102,A201901)。
文摘In this study,the first-order shear deformation theory(FSDT)is used to establish a nonlinear dynamic model for a conical shell truncated by a functionally graded graphene platelet-reinforced composite(FG-GPLRC).The vibration analyses of the FG-GPLRC truncated conical shell are presented.Considering the graphene platelets(GPLs)of the FG-GPLRC truncated conical shell with three different distribution patterns,the modified Halpin-Tsai model is used to calculate the effective Young’s modulus.Hamilton’s principle,the FSDT,and the von-Karman type nonlinear geometric relationships are used to derive a system of partial differential governing equations of the FG-GPLRC truncated conical shell.The Galerkin method is used to obtain the ordinary differential equations of the truncated conical shell.Then,the analytical nonlinear frequencies of the FG-GPLRC truncated conical shell are solved by the harmonic balance method.The effects of the weight fraction and distribution pattern of the GPLs,the ratio of the length to the radius as well as the ratio of the radius to the thickness of the FG-GPLRC truncated conical shell on the nonlinear natural frequency characteristics are discussed.This study culminates in the discovery of the periodic motion and chaotic motion of the FG-GPLRC truncated conical shell.
基金the Vietnam National Foundation for Science and Technology Development(NAFOSTED)(No.107.02-2019.318)。
文摘The nonlinear stability of sandwich cylindrical shells comprising porous functionally graded material(FGM) and carbon nanotube reinforced composite(CNTRC)layers subjected to uniform temperature rise is investigated. Two sandwich models corresponding to CNTRC and FGM face sheets are proposed. Carbon nanotubes(CNTs) in the CNTRC layer are embedded into a matrix according to functionally graded distributions. The effects of porosity in the FGM and the temperature dependence of properties of all constituent materials are considered. The effective properties of the porous FGM and CNTRC are determined by using the modified and extended versions of a linear mixture rule, respectively. The basic equations governing the stability problem of thin sandwich cylindrical shells are established within the framework of the Donnell shell theory including the von K’arm’an-Donnell nonlinearity. These equations are solved by using the multi-term analytical solutions and the Galerkin method for simply supported shells.The critical buckling temperatures and postbuckling paths are determined through an iteration procedure. The study reveals that the sandwich shell model with a CNTRC core layer and relatively thin porous FGM face sheets can have the best capacity of thermal load carrying. In addition, unlike the cases of mechanical loads, porosities have beneficial effects on the nonlinear stability of sandwich shells under the thermal load. It is suggested that an appropriate combination of advantages of FGM and CNTRC can result in optimal efficiency for advanced sandwich structures.
文摘The purpose of the present study is to examine the impact of initial geometric imperfection on the nonlinear dynamical characteristics of functionally graded carbon nanotube-reinforced composite(FG-CNTRC) rectangular plates under a harmonic excitation transverse load. The considered plate is assumed to be made of matrix and single-walled carbon nanotubes(SWCNTs). The rule of mixture is employed to calculate the effective material properties of the plate. Within the framework of the parabolic shear deformation plate theory with taking the influence of transverse shear deformation and rotary inertia into account, Hamilton’s principle is utilized to derive the geometrically nonlinear mathematical formulation including the governing equations and corresponding boundary conditions of initially imperfect FG-CNTRC plates. Afterwards, with the aid of an efficient multistep numerical solution methodology, the frequency-amplitude and forcing-amplitude curves of initially imperfect FG-CNTRC rectangular plates with various edge conditions are provided, demonstrating the influence of initial imperfection,geometrical parameters, and edge conditions. It is displayed that an increase in the initial geometric imperfection intensifies the softening-type behavior of system, while no softening behavior can be found in the frequency-amplitude curve of a perfect plate.
基金Project supported by the Foundation for Science and Technology Development of National University of Civil Engineering-Ha Noi-Vietnam (No. 27-2020/KHXD-TD)。
文摘This paper presents an analytical solution for the free vibration behavior of functionally graded carbon nanotube-reinforced composite(FG-CNTRC) doubly curved shallow shells with integrated piezoelectric layers. Here, the linear distribution of electric potential across the thickness of the piezoelectric layer and five different types of carbon nanotube(CNT) distributions through the thickness direction are considered. Based on the four-variable shear deformation refined shell theory, governing equations are obtained by applying Hamilton's principle. Navier's solution for the shell panels with the simply supported boundary condition at all four edges is derived. Several numerical examples validate the accuracy of the presented solution. New parametric studies regarding the effects of different material properties, shell geometric parameters, and electrical boundary conditions on the free vibration responses of the hybrid panels are investigated and discussed in detail.
文摘Compositionally graded composite of alumina-20%zirconia (volume fraction) was fabricated by using centrifugal casting incorporated with relatively thin slip. An EPMA analysis exhibited a nearly linear variation of the alumina/zirconia ratio along the centrifugal direction; zirconia tended to accumulate in the bottom section, while alumina in the top section. Such a graded structure exhibited a considerably higher flexural strength when the alumina rich surface was subjected to a tensile stress than compositionally uniform composite of the same average composition. Fracture toughness measurement across the specimen thickness by indentation method revealed that the crack lengths along the vertical and horizontal directions were different. The anisotropy of the fracture toughness was accounted for by the variation of the residual stress across the specimen thickness.
基金China National Committee of High Technology New Materials under grant No.863-715-011-0230.]
文摘W/Cu functionally gradient material (FGM) has excellent mechanical properties since it can effectively relax interlayer thermal stresses caused by the mismatch between their thermal expansion coefficients. W/Cu FGM combines the advantages of tungsten such as high melting point and service strength, with heat conductivity and plasticity of copper at room temperature. Thus it demonstrates satisfactory heat corrosion 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 (0-100%W) has been successfully fabricated. Suitable amount of transition metals (such as nickel, zirconium, vanadium) is employed as additives to activate tungsten's sintering, enhance phase wettability and bonding strength between W and Cu. Densification effects of different layer of FGM were investigated. Microstructure morphology and interface elements distribution were observed and analyzed. The thermal shock performance of W/Cu FGM was also preliminarily tested.
基金Project supported by the Natural Science Foundation of Jiangxi Science and Technology Department(No. 20202BAB204027)。
文摘This study presents the size-dependent nonlinear thermal postbuckling characteristics of a porous functionally graded material(PFGM) microplate with a central cutout with various shapes using isogeometric numerical technique incorporating nonuniform rational B-splines. To construct the proposed non-classical plate model, the nonlocal strain gradient continuum elasticity is adopted on the basis of a hybrid quasithree-dimensional(3D) plate theory under through-thickness deformation conditions by only four variables. By taking a refined power-law function into account in conjunction with the Touloukian scheme, the temperature-porosity-dependent material properties are extracted. With the aid of the assembled isogeometric-based finite element formulations,nonlocal strain gradient thermal postbuckling curves are acquired for various boundary conditions as well as geometrical and material parameters. It is portrayed that for both size dependency types, by going deeper in the thermal postbuckling domain, gaps among equilibrium curves associated with various small scale parameter values get lower, which indicates that the pronounce of size effects reduces by going deeper in the thermal postbuckling regime. Moreover, we observe that the central cutout effect on the temperature rise associated with the thermal postbuckling behavior in the presence of the effect of strain gradient size and absence of nonlocality is stronger compared with the case including nonlocality in absence of the strain gradient small scale effect.
基金Project supported by the National Natural Science Foundation of China(Nos.11802005,12172012,11832002,and 11427801)the General Program of Science and Technology Development Project of Beijing Municipal Education Commission of China(No.KM201910005035)
文摘This paper analyzes the nonlocal thermal buckling and postbuckling behaviors of a multi-layered graphene nanoplatelet(GPL)reinforced piezoelectric micro-plate.The GPLs are supposed to disperse as a gradient pattern in the composite micro-plate along its thickness.The effective material properties are calculated by the Halpin-Tsai parallel model and mixture rule for the functionally graded GPL reinforced piezoelectric(FG-GRP)micro-plate.Governing equations for the nonlocal thermal buckling and postbuckling behaviors of the FG-GRP micro-plate are obtained by the first-order shear deformation theory,the von Kármán nonlinear theory,and the minimum potential energy principle.The differential quadrature(DQ)method and iterative method are introduced to numerically analyze the effects of the external electric voltage,the distribution pattern and characteristic of GPLs,and the nonlocal parameter on the critical buckling behaviors and postbuckling equilibrium path of the FG-GRP micro-plate in thermal environment.
基金supported by the National Natural Science Foundation of China(Nos.12061131013,11972276,1211101401,12172171,and 12102183)the State Key Laboratory of Mechanics and Control of Mechanical Structures of Nanjing University of Aeronautics and Astronautics(No.MCMS-E-0520K02)+5 种基金the Fundamental Research Funds for the Central Universities of China(Nos.NE2020002 and NS2019007)the National Natural Science Foundation of China for Creative Research Groups(No.51921003)the Postgraduate Research&Practice Innovation Program of Jiangsu Province of China(No.KYCX210179)the National Natural Science Foundation of Jiangsu Province of China(No.BK20211176)the Local Science and Technology Development Fund Projects Guided by the Central Government of China(No.2021Szvup061)the Jiangsu High-Level Innovative and Entrepreneurial Talents Introduction Plan(Shuangchuang Doctor Program,No.JSSCBS20210166)。
文摘In this paper,we propose a specific two-layer model consisting of a functionally graded(FG)layer and a piezoelectric semiconductor(PS)layer.Based on the macroscopic theory of PS materials,the effects brought about by the attached FG layer on the piezotronic behaviors of homogeneous n-type PS fibers and PN junctions are investigated.The semi-analytical solutions of the electromechanical fields are obtained by expanding the displacement and carrier concentration variation into power series.Results show that the antisymmetry of the potential and electron concentration distributions in homogeneous n-type PS fibers is destroyed due to the material inhomogeneity of the attached FG layer.In addition,by creating jump discontinuities in the material properties of the FG layer,potential barriers/wells can be produced in the middle of the fiber.Similarly,the potential barrier configuration near the interface of a homogeneous PS PN junction can also be manipulated in this way,which offers a new choice for the design of PN junction based devices.
基金supported by the Basque Government(Eusko Jaurlaritza)(Nos.KK-2022/00080 Minaku,KK-2022/00070 Edison)tthe Spanish Ministry of Science and Innovation(Nos.PID2019-109220RB-I00 Alasurf,PDC2021-121042-I00 EHU-Coax)the Basque Government(Eusko Jaurlaritza)in call IT 1573-22 for the financial support of the research group.
文摘Wear-driven tool failure is one of the main hurdles in the industry.This issue can be addressed through surface coating with ceramic-reinforced metal matrix composites.However,the maximum ceramic content is limited by cracking.In this work,the tribological behaviour of the functionally graded WC-ceramic-particlereinforced Stellite 6 coatings is studied.To that end,the wear resistance at room temperature and 400°C is investigated.Moreover,the tribological analysis is supported by crack sensitivity and hardness evaluation,which is of utmost importance in the processing of composite materials with ceramic-particle-reinforcement.Results indicate that functionally graded materials can be employed to increase the maximum admissible WC content,hence improving the tribological behaviour,most notably at high temperatures.Additionally,a shift from abrasive to oxidative wear is observed in high-temperature wear testing.
文摘In INs study, the fabrication of multilayer AI(Zn)-A1203 with different volume fractions of A1203 was investigated. A1 and ZnO powders were milled by a plaaetaxy ball mill, after which five-layer functionally graded samples were produced flarough hot pressing at 580~C and 90 MPa pressure for 30 min. Formation of reinforcing A1203 particles occurred in the aluminum matrix via the aluminolkermic reaction. Determination of the ignition temperature of the aluminolkennic reaction was accomplished using differential lkermal and lkermo- gravimelric amlyses. Scaaming electron microscopy, energy dispersive spectroscopy, and X-ray diffractometery amlyses were utilized to characterize the specimens. The lkermal amlysis results showed that the ignition temperatures for the aluminolkennic reaction of layers with the highest and lowest ZnO contents were 667 and 670~C, respectively. Microslxuctural observation and chemical amlysis confirmed the fa- brication of AI(Zn)-A1203 functionally graded materials composites with precipitation of additional Zn in the matrix. Moreover, nearly dense functionally graded samples demonstrated minimum and maximum hacdness values of HV 75 and HV 130, respectively.
基金This work was financially supported by "863 " key foundation of China (No. 715-011-0230).
文摘A new approach for fabricating B4C/Cu graded composite by rapid self-resistance sintering under ultra-high pressure was presented, by which a near dense B4C/Cu graded composite with a compositional spectrum of 0-100% was successfully fabricated. Plasma relevant performances of sintered B4C/Cu composite were preliminarily characterized, it is found that its chemical sputtering yield is 70% lower than that of SMF800 nuclear graphite under 2.7keV D+ irradiation, and almost no damages after 66 shots of in situ plasma discharge in HL-1 Tokamak facility, which indicates B4C/Cu plasma facing component has a good physical and chemical sputtering resistance performance compared with nuclear graphite.
基金Supported by the Key Program of the National Natural Science Foundation of China (Grant No.50438010)the Research and Application Programs of Key Technologies for Major Constructions in the South-North Water Transfer Project Construction in China (Grant No.JGZXJJ2006-13)
文摘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.
文摘The objective of present work is to apply the friction stir processing (FSP) to fabricate functionally graded SiC particulate reinforced Al6061 composite and investigate the effect of SiC particle mass fraction distribution on the mechanical properties and wear behavior ofAl6061/SiC composite. Regarding the obtained results in this work, with increasing SiC mass fraction, elongation decreased, but hardness enhanced. However, the optimized functionally graded composite with the highest tensile strength and wear resistance was achieved for composite with 10 wt% surface SiC. Also, the results showed that wear resistance and tensile strength decreased for composite with 13 wt% surface SiC, due to reinforcement particle clustering depending on high SiC mass fraction.
基金National Natural Science Foundation of China(Grant No.11872245)the Research Grants Council of the Hong Kong Special Administrative Region,China(Grant Nos.9042644,CityU11205518)。
文摘In the last decade,the functionally graded carbon nanotube reinforced composites(FG-CNTRCs)have attracted considerable interest due to their excellent mechanical properties,and the structures made of FG-CNTRCs have found broad potential applications in aerospace,civil and ocean engineering,automotive industry,and smart structures.Here we review the literature regarding the mechanical analysis of bulk CNTR nanocomposites and FG-CNTRC structures,aiming to provide a clear picture of the mechanical modeling and properties of FG-CNTRCs as well as their composite structures.The review is organized as follows:(1)a brief introduction to the functionally graded materials(FGM),CNTRCs and FG-CNTRCs;(2)a literature review of the mechanical modeling methodologies and properties of bulk CNTRCs;(3)a detailed discussion on the mechanical behaviors of FG-CNTRCs;and(4)conclusions together with a suggestion of future research trends.
文摘Copper matrix composites have received more attentions as possible candidate for thermal and electrical conductive materials to be used in electrical contact applications. In this study, five-layered Cu/YSZ (yttria-stabilized zirconia) functionally graded material (FGM) and copper matrix composite specimens containing 3 and 5 vol% YSZ particles plus pure Cu specimen were synthesized using powder metallurgy (PM) route and spark plasma sintering (SPS) consolidation process. The microstructural and some physical, mechanical features of all specimens were characterized. Microscopic examinations showed that ultrafine YSZ particles were distributed in the copper matrix almost homoge- neously. An appropriate interface was observed at each layer of FGM. The density measurement indicated that the graded structure of the composite could be well densified after the SPS process. The microhardness values of various layers of Cu/ YSZ FGM specimen were gradually altered from 56.3 (pure copper side) to 75.2 HV (Cu-5 vol% YSZ side). The increase of YSZ content resulted in a decrease in electrical conductivity. Additionally, thermal conductivity of Cu/YSZ FGM specimen [308.0 W/(m K)] was determined to be higher than that of the Cu-5 vol% YSZ composite specimen [260.7 W/ (m K)]. Accordingly, it can be concluded that the Cu/YSZ FGM can be a good candidate for the electrical applications, like sliding electrical contacts, where different material characteristics in the same component are required.
基金This research was funded by Vietnam National Foundation for Science and Technology Development(NAFOSTED)under No.107.02-2019.330.
文摘This paper proposes a new Deep Feed-forward Neural Network(DFNN)approach for damage detection in functionally graded carbon nanotube-reinforced composite(FG-CNTRC)plates.In the proposed approach,the DFNN model is developed based on a data set containing 20000 samples of damage scenarios,obtained via finite element(FE)simulation,of the FG-CNTRC plates.The elemental modal kinetic energy(MKE)values,calculated from natural frequencies and translational nodal displacements of the structures,are utilized as input of the DFNN model while the damage locations and corresponding severities are considered as output.The state-of-the art Exponential Linear Units(ELU)activation function and the Adamax algorithm are employed to train the DFNN model.Additionally,in order to enhance the performance of the DFNN model,the mini-batch and early-stopping techniques are applied to the training process.A trial-and-error procedure is implemented to determine suitable parameters of the network such as the number of hidden layers and the number of neurons in each layer.The accuracy and capability of the proposed DFNN model are illustrated through two distinct configurations of the CNT-fibers constituting the FG-CNTRC plates including uniform distribution(UD)and functionally graded-V distribution(FG-VD).Furthermore,the performance and stability of the DFNN model with the consideration of noise effects on the input data are also investigated.Obtained results indicate that the proposed DFNN model is able to give sufficiently accurate damage detection outcomes for the FG-CNTRC plates for both cases of noise-free and noise-influenced data.