This paper considers the pure bending problem of simply supported transversely isotropic circular plates with elastic compliance coefficients being arbitrary functions of the thickness coordinate. First, the partial d...This paper considers the pure bending problem of simply supported transversely isotropic circular plates with elastic compliance coefficients being arbitrary functions of the thickness coordinate. First, the partial differential equation, which is satisfied by the stress functions for the axisymmetric deformation problem is derived. Then, stress functions are obtained by proper manipulation. The analytical expressions of axial force, bending moment and displacements are then deduced through integration. And then, stress functions are employed to solve problems of transversely isotropic functionally graded circular plate, with the integral constants completely determined from boundary conditions. An elasticity solution for pure bending problem, which coincides with the available solution when degenerated into the elasticity solutions for homogenous circular plate, is thus obtained. A numerical example is finally presented to show the effect of material inhomogeneity on the elastic field in a simply supported circular plate of transversely isotropic functionally graded material (FGM).展开更多
The electric field distributions along gas-solid interfaces determine the reliability,lifetimes and sizes of gaseous insulated switchgears/pipelines(GIS/GIL),which also affect the reliability of power systems.In this ...The electric field distributions along gas-solid interfaces determine the reliability,lifetimes and sizes of gaseous insulated switchgears/pipelines(GIS/GIL),which also affect the reliability of power systems.In this study,the characteristics of steady and transient electric field distributions were first introduced,followed by the concept of functionally graded materials(FGMs).The development histories of FGM applied in electrical engineering and the related optimisation methods were described in detail.The field regulation effect and fabrication technology of different FGM insulators were also compared.To overcome the limitations of traditional FGM insulators,the design of surface FGM(SFGM)was proposed,together with their preparation methods and electrical performance.Furthermore,the future development prospects of FGM and SFGM insulators for compact GIS/GIL were summarised.展开更多
Cylinder-like in-situ AI/24Si FGMs were produced by using electromagnetic separating process. Si primary phase reinforced layer with volume fraction as high as 16 pct was formed at the outer region of the cylinder-lik...Cylinder-like in-situ AI/24Si FGMs were produced by using electromagnetic separating process. Si primary phase reinforced layer with volume fraction as high as 16 pct was formed at the outer region of the cylinder-like samples where the local hardness and wear resistance were enhanced remarkably. Moreover, both of strength and ductility in the inner region provided insurance of reliable strength for this as-cast gradient material. It indicated that general mechanical properties such as good wear resistance at the outer region and good ductility in the central part could be obtained with the optimized redistribution of the Si primary particles under the electromagnetic force.展开更多
This paper is concerned with the wave propagation behavior of rotating functionally graded（FG）temperature-dependent nanoscale beams subjected to thermal loading based on nonlocal strain gradient stress field.Uniform...This paper is concerned with the wave propagation behavior of rotating functionally graded（FG）temperature-dependent nanoscale beams subjected to thermal loading based on nonlocal strain gradient stress field.Uniform,linear and nonlinear temperature distributions across the thickness are investigated.Thermo-elastic properties of FG beam change gradually according to the Mori–Tanaka distribution model in the spatial coordinate.The nanobeam is modeled via a higher-order shear deformable refined beam theory which has a trigonometric shear stress function.The governing equations are derived by Hamilton’s principle as a function of axial force due to centrifugal stiffening and displacement.The solution of these equations is provided employing a Galerkin-based approach which has the potential to capture various boundary conditions.By applying an analytical solution and solving an eigenvalue problem,the dispersion relations of rotating FG nanobeam are obtained.Numerical results illustrate that various parameters including temperature change,angular velocity,nonlocality parameter,wave number and gradient index have significant effects on the wave dispersion characteristics of the nanobeam under study.The outcome of this study can provide beneficial information for the next-generation research and the exact design of nano-machines including nanoscale molecular bearings,nanogears,etc.展开更多
The preparation of functionally graded materials （FGMs） of （TiB2）pNi with an intermetallic compound media layer of Ni3Al and a substrate of nickel by field-activated pressure-assisted synthesis process （FAPAS） w...The preparation of functionally graded materials （FGMs） of （TiB2）pNi with an intermetallic compound media layer of Ni3Al and a substrate of nickel by field-activated pressure-assisted synthesis process （FAPAS） was investigated. Ni3Al was chosen as a layer of FGM for the first time due to its great deal of heat released during its synthesis from nickel and aluminium powder. The microstructure, phase composition of layers, micro-hardness and elemental concentration profiles across interfaces were characterized. The significant inter-diffusion of elements between layers showed the formation of good bonds. The measured micro-hardness values of the sample increased monotonically to more than 3 500 HK over a distance of 2 mm from the nickel substrate to the surface layer （TiB2）pNi. The results of this investigation demonstrate the feasibility of the FAPAS process for rapid formation of FGMs with good diffusion bonds.展开更多
W/ Cu functionally gradient materials （FGMs） containing 1% La2O3 and 1% TiC were prepared using graded sintering under tdtra-high pressure （GSUHP）. The specimens have been found to exhibit low porosity （11.57% an...W/ Cu functionally gradient materials （FGMs） containing 1% La2O3 and 1% TiC were prepared using graded sintering under tdtra-high pressure （GSUHP）. The specimens have been found to exhibit low porosity （11.57% and 11.35%, respectively）. Shearing strength of the specimens between layers is good. Moreover, the specimens have still demonstrated good performance in testing thermal-shock resistance. When power density of laser is 200MWm^-2, the specimens have been tested for thermal-shock resistance （1000 times）; the specimens that contained 1%La2O3 were not subjected to damage, whereas those that contained 1%TiC began to crack. Finally, effect of additives on thermal-shock resistance was also preliminarily discussed.展开更多
An improved multi-step sintering process was used to in-situ prepare TiB2-TiB-Ti FGMs. According to the sintering temperatures, the functionally graded materials （FGMs） were divided into three sections. After sinter...An improved multi-step sintering process was used to in-situ prepare TiB2-TiB-Ti FGMs. According to the sintering temperatures, the functionally graded materials （FGMs） were divided into three sections. After sintering at a proper temperature, the three sections were sintered together in turn. The experimental results showed that there were no obvious pores and cracks in the whole TiB2-TiB-Ti FGMs, and no delamination was found in the impacting test with good performance features, which indicated that there were no interface effects in FGMs during penetration, so that the TiB2-TiB-Ti FGMs were an ideal FGM.展开更多
This paper investigated the nonlinear vibration of functionally graded beams containing an open edge crack based on Timoshenko beam theory.The cracked section is modeled by a massless elastic rotational spring.It is a...This paper investigated the nonlinear vibration of functionally graded beams containing an open edge crack based on Timoshenko beam theory.The cracked section is modeled by a massless elastic rotational spring.It is assumed that material properties follow exponential distributions through the beam thickness.The differential quadrature(DQ) method is employed to discretize the nonlinear governing equations which are then solved by a direct iterative method to obtain the nonlinear vibration frequencies of beams with different boundary conditions.The effects of the material gradient,crack depth and boundary conditions on nonlinear free vibration characteristics of the cracked FGM beams are studied in detail.展开更多
基金Project (Nos. 10472102 and 10432030) supported by the NationalNatural Science Foundation of China
文摘This paper considers the pure bending problem of simply supported transversely isotropic circular plates with elastic compliance coefficients being arbitrary functions of the thickness coordinate. First, the partial differential equation, which is satisfied by the stress functions for the axisymmetric deformation problem is derived. Then, stress functions are obtained by proper manipulation. The analytical expressions of axial force, bending moment and displacements are then deduced through integration. And then, stress functions are employed to solve problems of transversely isotropic functionally graded circular plate, with the integral constants completely determined from boundary conditions. An elasticity solution for pure bending problem, which coincides with the available solution when degenerated into the elasticity solutions for homogenous circular plate, is thus obtained. A numerical example is finally presented to show the effect of material inhomogeneity on the elastic field in a simply supported circular plate of transversely isotropic functionally graded material (FGM).
基金the National Natural Science Foundation of China(51807136,51537008 and U196620069)the Natural Science Foundation of Tianjin City(18JCQNJC07300)+3 种基金the National Postdoctoral Program for Innovative Talents(BX201700168)the Key Laboratory of Engineering Dielectrics and Its Application(Harbin University of Science and Technology)the Ministry of Education(KFY1804)Project supported by the China State Key Lab.of Power System(SKLD19KM08).
文摘The electric field distributions along gas-solid interfaces determine the reliability,lifetimes and sizes of gaseous insulated switchgears/pipelines(GIS/GIL),which also affect the reliability of power systems.In this study,the characteristics of steady and transient electric field distributions were first introduced,followed by the concept of functionally graded materials(FGMs).The development histories of FGM applied in electrical engineering and the related optimisation methods were described in detail.The field regulation effect and fabrication technology of different FGM insulators were also compared.To overcome the limitations of traditional FGM insulators,the design of surface FGM(SFGM)was proposed,together with their preparation methods and electrical performance.Furthermore,the future development prospects of FGM and SFGM insulators for compact GIS/GIL were summarised.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 59871029)the National Key Research Foundation of China (Grant No. G1999064900-4).
文摘Cylinder-like in-situ AI/24Si FGMs were produced by using electromagnetic separating process. Si primary phase reinforced layer with volume fraction as high as 16 pct was formed at the outer region of the cylinder-like samples where the local hardness and wear resistance were enhanced remarkably. Moreover, both of strength and ductility in the inner region provided insurance of reliable strength for this as-cast gradient material. It indicated that general mechanical properties such as good wear resistance at the outer region and good ductility in the central part could be obtained with the optimized redistribution of the Si primary particles under the electromagnetic force.
文摘This paper is concerned with the wave propagation behavior of rotating functionally graded（FG）temperature-dependent nanoscale beams subjected to thermal loading based on nonlocal strain gradient stress field.Uniform,linear and nonlinear temperature distributions across the thickness are investigated.Thermo-elastic properties of FG beam change gradually according to the Mori–Tanaka distribution model in the spatial coordinate.The nanobeam is modeled via a higher-order shear deformable refined beam theory which has a trigonometric shear stress function.The governing equations are derived by Hamilton’s principle as a function of axial force due to centrifugal stiffening and displacement.The solution of these equations is provided employing a Galerkin-based approach which has the potential to capture various boundary conditions.By applying an analytical solution and solving an eigenvalue problem,the dispersion relations of rotating FG nanobeam are obtained.Numerical results illustrate that various parameters including temperature change,angular velocity,nonlocality parameter,wave number and gradient index have significant effects on the wave dispersion characteristics of the nanobeam under study.The outcome of this study can provide beneficial information for the next-generation research and the exact design of nano-machines including nanoscale molecular bearings,nanogears,etc.
基金Funded by the National Natural Science Foundation of China(No.50975190)
文摘The preparation of functionally graded materials （FGMs） of （TiB2）pNi with an intermetallic compound media layer of Ni3Al and a substrate of nickel by field-activated pressure-assisted synthesis process （FAPAS） was investigated. Ni3Al was chosen as a layer of FGM for the first time due to its great deal of heat released during its synthesis from nickel and aluminium powder. The microstructure, phase composition of layers, micro-hardness and elemental concentration profiles across interfaces were characterized. The significant inter-diffusion of elements between layers showed the formation of good bonds. The measured micro-hardness values of the sample increased monotonically to more than 3 500 HK over a distance of 2 mm from the nickel substrate to the surface layer （TiB2）pNi. The results of this investigation demonstrate the feasibility of the FAPAS process for rapid formation of FGMs with good diffusion bonds.
文摘W/ Cu functionally gradient materials （FGMs） containing 1% La2O3 and 1% TiC were prepared using graded sintering under tdtra-high pressure （GSUHP）. The specimens have been found to exhibit low porosity （11.57% and 11.35%, respectively）. Shearing strength of the specimens between layers is good. Moreover, the specimens have still demonstrated good performance in testing thermal-shock resistance. When power density of laser is 200MWm^-2, the specimens have been tested for thermal-shock resistance （1000 times）; the specimens that contained 1%La2O3 were not subjected to damage, whereas those that contained 1%TiC began to crack. Finally, effect of additives on thermal-shock resistance was also preliminarily discussed.
基金Funded by the National Natural Science Foundation of China(No.U12301013)the Innovation Fund of Wuhan University of Technology(No.123243005)
文摘An improved multi-step sintering process was used to in-situ prepare TiB2-TiB-Ti FGMs. According to the sintering temperatures, the functionally graded materials （FGMs） were divided into three sections. After sintering at a proper temperature, the three sections were sintered together in turn. The experimental results showed that there were no obvious pores and cracks in the whole TiB2-TiB-Ti FGMs, and no delamination was found in the impacting test with good performance features, which indicated that there were no interface effects in FGMs during penetration, so that the TiB2-TiB-Ti FGMs were an ideal FGM.
基金supported by the National Natural Science Foundation of China (Grant No. 11002019)Ph.D. Programs Foundation of the Ministry of Education of China (Grant No. 20100009120018)the Fundamental Research Funds for the Central Universities (Grant No. 2009JBM073)
文摘This paper investigated the nonlinear vibration of functionally graded beams containing an open edge crack based on Timoshenko beam theory.The cracked section is modeled by a massless elastic rotational spring.It is assumed that material properties follow exponential distributions through the beam thickness.The differential quadrature(DQ) method is employed to discretize the nonlinear governing equations which are then solved by a direct iterative method to obtain the nonlinear vibration frequencies of beams with different boundary conditions.The effects of the material gradient,crack depth and boundary conditions on nonlinear free vibration characteristics of the cracked FGM beams are studied in detail.
