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
This paper aims to explore and quantify the nonlinear vibration response of tri-directional functionally graded sandwich(3D-FGSW)plates partially supported by a Pasternak foundation(PF)subjected to blast loading(BL).A...This paper aims to explore and quantify the nonlinear vibration response of tri-directional functionally graded sandwich(3D-FGSW)plates partially supported by a Pasternak foundation(PF)subjected to blast loading(BL).A key objective is to develop a computationally efficient finite element framework capable of accurately capturing the complex behavior of 3D-FGSW plates.The studied configuration features a two-dimensional functionally graded material(2D-FGM)core between two threedimensional functionally graded material(3D-FGM)face layers.Nonlinear geometric effects,including mid-plane stretching,are modeled using von K arm an-type assumptions,and the governing equations are formulated via Hamilton's principle within an improved first-order shear deformation theory(iFSDT).The accuracy and computational efficiency of the proposed method are validated through comparison with existing benchmark solutions.Subsequently,a comprehensive parametric study is carried out to examine the effects of geometric dimensions,material properties,foundation sizes,and boundary conditions(BCs)on the nonlinear vibration of 3D-FGSW plates.The findings of this work are expected to provide valuable insights for the design and manufacturing of advanced sandwich structures subjected to BL.展开更多
This study explores the dynamic contact response of a viscoelastic functionally graded material(FGM)-coated half-plane under a rigid flat punch subjected to a time-harmonic vertical force.The elastic modulus and mass ...This study explores the dynamic contact response of a viscoelastic functionally graded material(FGM)-coated half-plane under a rigid flat punch subjected to a time-harmonic vertical force.The elastic modulus and mass density of the FGM coating vary exponentially along the thickness direction.The FGM coating and the homogeneous half-plane possess viscoelastic properties,which are described by a linearly hysteretic damping model.By applying the asymptotic method and the Fourier integral transform technique,the contact problem is converted into a Cauchy singular integral equation.The effects of excitation frequency,gradient index,damping factor ratio,and punch width on the vertical impedance and dynamic contact stress are analyzed.The results indicate that adjusting the gradient index of the FGM coating can significantly affect the contact stress and vertical impedance.展开更多
The global discussion surrounding Functionally Graded Materials(FGMs)highlights their unique and diverse micro-material properties that result from varying two or more materials in a strategic combination profile.Thes...The global discussion surrounding Functionally Graded Materials(FGMs)highlights their unique and diverse micro-material properties that result from varying two or more materials in a strategic combination profile.These combinations produce distinct physical and chemical characteristics.Changes in these characteristics may occur continuously,referred to as a gradient function,or discontinuously as a stepwise function.The changes can appear within homogeneous or heterogeneous material geometries.The variation in material properties depends on the volume fraction index function.This variation can occur in 1D,2D,or 3D,either in the thickness or length direction within a material model.The vacuum in the review study on mechanically toughened and thermally resistant Functionally Graded(FG)pipelines prompted the current review study.This study addresses the absence of an appropriate variational function for FG cylindrical pipelines.It proposes a gradation function pattern to improve pipeline structural performance.An appraisal based on relevant FGM literature was conducted to improve the temperature differentials in traditional composite materials and stress-related issues in carbon steel pipelines.The review identifies specific FGM property variations that reduce failures that are possible in conventional materials.Reviewed articles and evaluation procedures followed the 2020 PRISMA guidelines.Literature was obtained from Scopus,Connected Papers,and other reputable sources.The study also discusses potential FG pipelines for gas and green energy transportation.The reviewed literature establishes the context for this research and addresses the gap in 3D FG model variation functions involving multiple materials.展开更多
An improved meshfree moving-Kriging(MK)formulation for free vibration analysis of functionally graded material-functionally graded carbon nanotube-reinforced composite(FGM-FGCNTRC)sandwich shells is first proposed in ...An improved meshfree moving-Kriging(MK)formulation for free vibration analysis of functionally graded material-functionally graded carbon nanotube-reinforced composite(FGM-FGCNTRC)sandwich shells is first proposed in this article.The proposed sandwich structure consists of skins of FGM layers and an FGCNTRC core.This structure possesses all the advantages of FGM and FGCNTRC,including high electrical or thermal insulating properties,high fatigue resistance,good corrosion resistance,high stiffness,low density,high strength,and high aspect ratios.Such sandwich structures can be used to replace conventional FGM structures.The present formulation has been established by using an improved meshfree MK method and the first-order shear deformation shell theory(FSDT).The effective material characteristics of the FGM-skin layers and the FGCNTRC core were calculated using the rule of mixture.Key parameters and factors such as the thickness-to-radius ratio,the length-to-radius ratio,layer-thickness ratios,CNT distributions,the volume fraction of CNTs,the power-law index,and various boundary conditions were rigorously investigated.A nonlinear CNT distribution that we term FG-nX is first proposed in this work,and many new results of FGM-FGCNTRC sandwich shells have been provided.展开更多
This paper proposes a novel three-directional functionally graded(3D FG)vibration energy harvesting model based on a bimorph pipe structure.A rectangular pipe has material properties that vary continuously along the a...This paper proposes a novel three-directional functionally graded(3D FG)vibration energy harvesting model based on a bimorph pipe structure.A rectangular pipe has material properties that vary continuously along the axial,width,and height directions,and a steady fluid flows inside the pipe.Two piezoelectric layers are attached to the upper and lower surfaces of the pipe,and are connected in series with a load resistance.The output electricity is predicted theoretically and validated by finite element(FE) simulation.The complex mechanisms regulating the energy harvesting performance are investigated,focusing particularly on the effects of 3D FG material(FGM) parameters,load resistance,fluid-structure interaction(FSI),and geometry.Numerical results indicate that among several material gradient parameters,the axial gradient index has the most significant impact.Increasing the axial and height gradient indices can markedly enhance the energy harvesting performance.The optimal resistances differ between the first two modes.Overall,the maximum power is generated at lower resistances.The FSI effect can also improve the energy harvesting performance;however,higher flow velocities may destabilize the system,causing failure of harvesting energy.This research is capable of providing new insights into the design of a pipe energy harvester in engineering applications.展开更多
This study examines the nonlinear behaviors of a clamped-clamped porous pipe made of a functionally graded material(FGM)that conveys fluids and is equipped with a retaining clip,focusing on primary resonance and subcr...This study examines the nonlinear behaviors of a clamped-clamped porous pipe made of a functionally graded material(FGM)that conveys fluids and is equipped with a retaining clip,focusing on primary resonance and subcritical dynamics.The nonlinear governing equations for the FGM pipe are derived by the extended Hamilton's principle,and subsequently discretized through the application of the Galerkin method.The direct method of multi-scales is then used to solve the derived equations.A thorough analysis of various parameters,including the clip stiffness,the power-law index,the porosity,and the clip location,is conducted to gain a comprehensive understanding of the system's nonlinear dynamics.Through the analysis of the first natural frequency,the study highlights the influence of the flow velocity and the clip stiffness,while the comparisons with metallic pipes emphasize the role of FGM composition.The examination of the forced response curves reveals saddle-node bifurcations and their dependence on parameters such as the detuning parameter and the power-law index,offering valuable insights into the system's nonlinear resonant behavior.Furthermore,the frequency-response curves illustrate the hardening nonlinearities influenced by factors such as the porosity and the clip stiffness,revealing nuanced effects on the system response and resonance characteristics.This comprehensive analysis enhances the understanding of nonlinear behaviors in FGM porous pipes with a retaining clip,providing key insights for practical engineering applications in system design and optimization.展开更多
本文主要研究了FGM Copula相依下随机变量二阶顺序统计量的随机比较,给出了二阶顺序统计量之间普通随机序、增凸序与增凹序关系成立的充分条件,并通过数值例子说明了主要结论。This paper investigates the stochastic comparison of se...本文主要研究了FGM Copula相依下随机变量二阶顺序统计量的随机比较,给出了二阶顺序统计量之间普通随机序、增凸序与增凹序关系成立的充分条件,并通过数值例子说明了主要结论。This paper investigates the stochastic comparison of second-order statistics from dependent random samples with FGM Copula. Sufficient conditions are established on the usual stochastic order, the increasing convex order and the increasing concave order for the second-order statistic. And some numerical examples are provided to illustrate the theoretical results.展开更多
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.
文摘This paper aims to explore and quantify the nonlinear vibration response of tri-directional functionally graded sandwich(3D-FGSW)plates partially supported by a Pasternak foundation(PF)subjected to blast loading(BL).A key objective is to develop a computationally efficient finite element framework capable of accurately capturing the complex behavior of 3D-FGSW plates.The studied configuration features a two-dimensional functionally graded material(2D-FGM)core between two threedimensional functionally graded material(3D-FGM)face layers.Nonlinear geometric effects,including mid-plane stretching,are modeled using von K arm an-type assumptions,and the governing equations are formulated via Hamilton's principle within an improved first-order shear deformation theory(iFSDT).The accuracy and computational efficiency of the proposed method are validated through comparison with existing benchmark solutions.Subsequently,a comprehensive parametric study is carried out to examine the effects of geometric dimensions,material properties,foundation sizes,and boundary conditions(BCs)on the nonlinear vibration of 3D-FGSW plates.The findings of this work are expected to provide valuable insights for the design and manufacturing of advanced sandwich structures subjected to BL.
基金Project supported by the National Natural Science Foundation of China(Nos.12021002,12192212,and 12462007)。
文摘This study explores the dynamic contact response of a viscoelastic functionally graded material(FGM)-coated half-plane under a rigid flat punch subjected to a time-harmonic vertical force.The elastic modulus and mass density of the FGM coating vary exponentially along the thickness direction.The FGM coating and the homogeneous half-plane possess viscoelastic properties,which are described by a linearly hysteretic damping model.By applying the asymptotic method and the Fourier integral transform technique,the contact problem is converted into a Cauchy singular integral equation.The effects of excitation frequency,gradient index,damping factor ratio,and punch width on the vertical impedance and dynamic contact stress are analyzed.The results indicate that adjusting the gradient index of the FGM coating can significantly affect the contact stress and vertical impedance.
基金The Petroleum Training Development Fund(PTDF)is highly acknowledged for sponsorship.
文摘The global discussion surrounding Functionally Graded Materials(FGMs)highlights their unique and diverse micro-material properties that result from varying two or more materials in a strategic combination profile.These combinations produce distinct physical and chemical characteristics.Changes in these characteristics may occur continuously,referred to as a gradient function,or discontinuously as a stepwise function.The changes can appear within homogeneous or heterogeneous material geometries.The variation in material properties depends on the volume fraction index function.This variation can occur in 1D,2D,or 3D,either in the thickness or length direction within a material model.The vacuum in the review study on mechanically toughened and thermally resistant Functionally Graded(FG)pipelines prompted the current review study.This study addresses the absence of an appropriate variational function for FG cylindrical pipelines.It proposes a gradation function pattern to improve pipeline structural performance.An appraisal based on relevant FGM literature was conducted to improve the temperature differentials in traditional composite materials and stress-related issues in carbon steel pipelines.The review identifies specific FGM property variations that reduce failures that are possible in conventional materials.Reviewed articles and evaluation procedures followed the 2020 PRISMA guidelines.Literature was obtained from Scopus,Connected Papers,and other reputable sources.The study also discusses potential FG pipelines for gas and green energy transportation.The reviewed literature establishes the context for this research and addresses the gap in 3D FG model variation functions involving multiple materials.
文摘An improved meshfree moving-Kriging(MK)formulation for free vibration analysis of functionally graded material-functionally graded carbon nanotube-reinforced composite(FGM-FGCNTRC)sandwich shells is first proposed in this article.The proposed sandwich structure consists of skins of FGM layers and an FGCNTRC core.This structure possesses all the advantages of FGM and FGCNTRC,including high electrical or thermal insulating properties,high fatigue resistance,good corrosion resistance,high stiffness,low density,high strength,and high aspect ratios.Such sandwich structures can be used to replace conventional FGM structures.The present formulation has been established by using an improved meshfree MK method and the first-order shear deformation shell theory(FSDT).The effective material characteristics of the FGM-skin layers and the FGCNTRC core were calculated using the rule of mixture.Key parameters and factors such as the thickness-to-radius ratio,the length-to-radius ratio,layer-thickness ratios,CNT distributions,the volume fraction of CNTs,the power-law index,and various boundary conditions were rigorously investigated.A nonlinear CNT distribution that we term FG-nX is first proposed in this work,and many new results of FGM-FGCNTRC sandwich shells have been provided.
基金Project supported by the National Natural Science Foundation of China (Nos. 12372025 and 12072311)。
文摘This paper proposes a novel three-directional functionally graded(3D FG)vibration energy harvesting model based on a bimorph pipe structure.A rectangular pipe has material properties that vary continuously along the axial,width,and height directions,and a steady fluid flows inside the pipe.Two piezoelectric layers are attached to the upper and lower surfaces of the pipe,and are connected in series with a load resistance.The output electricity is predicted theoretically and validated by finite element(FE) simulation.The complex mechanisms regulating the energy harvesting performance are investigated,focusing particularly on the effects of 3D FG material(FGM) parameters,load resistance,fluid-structure interaction(FSI),and geometry.Numerical results indicate that among several material gradient parameters,the axial gradient index has the most significant impact.Increasing the axial and height gradient indices can markedly enhance the energy harvesting performance.The optimal resistances differ between the first two modes.Overall,the maximum power is generated at lower resistances.The FSI effect can also improve the energy harvesting performance;however,higher flow velocities may destabilize the system,causing failure of harvesting energy.This research is capable of providing new insights into the design of a pipe energy harvester in engineering applications.
文摘This study examines the nonlinear behaviors of a clamped-clamped porous pipe made of a functionally graded material(FGM)that conveys fluids and is equipped with a retaining clip,focusing on primary resonance and subcritical dynamics.The nonlinear governing equations for the FGM pipe are derived by the extended Hamilton's principle,and subsequently discretized through the application of the Galerkin method.The direct method of multi-scales is then used to solve the derived equations.A thorough analysis of various parameters,including the clip stiffness,the power-law index,the porosity,and the clip location,is conducted to gain a comprehensive understanding of the system's nonlinear dynamics.Through the analysis of the first natural frequency,the study highlights the influence of the flow velocity and the clip stiffness,while the comparisons with metallic pipes emphasize the role of FGM composition.The examination of the forced response curves reveals saddle-node bifurcations and their dependence on parameters such as the detuning parameter and the power-law index,offering valuable insights into the system's nonlinear resonant behavior.Furthermore,the frequency-response curves illustrate the hardening nonlinearities influenced by factors such as the porosity and the clip stiffness,revealing nuanced effects on the system response and resonance characteristics.This comprehensive analysis enhances the understanding of nonlinear behaviors in FGM porous pipes with a retaining clip,providing key insights for practical engineering applications in system design and optimization.
文摘本文主要研究了FGM Copula相依下随机变量二阶顺序统计量的随机比较,给出了二阶顺序统计量之间普通随机序、增凸序与增凹序关系成立的充分条件,并通过数值例子说明了主要结论。This paper investigates the stochastic comparison of second-order statistics from dependent random samples with FGM Copula. Sufficient conditions are established on the usual stochastic order, the increasing convex order and the increasing concave order for the second-order statistic. And some numerical examples are provided to illustrate the theoretical results.
