This paper presents,for the first time,an effective numerical approach based on the isogeometric analysis(IGA)and the six-variable quasi-three dimensional(3D)higher-order shear deformation theory(HSDT)to study the fre...This paper presents,for the first time,an effective numerical approach based on the isogeometric analysis(IGA)and the six-variable quasi-three dimensional(3D)higher-order shear deformation theory(HSDT)to study the free vibration characteristics of functionally-graded(FG)graphene origami(GOri)-enabled auxetic metamaterial(GOEAM)plates submerged in a fluid medium.The plate theory incorporates the thickness stretching and the effects of transverse shear deformation without using any shear correction factors.The velocity potential function and Bernoulli's equation are used to derive the hydrodynamic pressure acting on the plate surface.Both horizontally and vertically immersed plate configurations are considered here in the form of inertia effects.The plates are composed of multilayer GOEAMs,with the GOri content varying through the plate's thickness in a layer-wise manner.This design results in graded auxetic growth.The material properties are evaluated by mixing rules and a genetic programming(GP)-assisted micromechanical model.The governing equations of motion for the FG-GOEAM plates immersed in a fluid medium are derived by Hamilton's principle.After validating the convergence and accuracy of the present model,a comprehensive parametric study is carried out to examine the effects of the GOri content,GOri distribution pattern,GOri folding degree,fluid level,immersed depth,and geometric parameter on the natural frequencies of the FG-GOEAM plates.The results show that the natural frequencies for the four GOri distribution patterns increase with the increase in the layer number when the lay number is fewer than 10,and then stabilize after the layer number reaches 10.Besides,in general,the natural frequency of the FG-GOEAM plate in a vacuum or fluid increases when the GOri content increases,while decreases when the GOri folding degree increases.Some additional findings related to the numerical results are presented in the conclusions.It is believed that the present results are useful for the precise design and optimization of FG-GOEAM plates immersed in a fluid medium.展开更多
Use of composite structures is exponentially growing in different fields due to their higher strength-to-weight ratio. This application trend requires that accurate theoretical explanations and their finite element mo...Use of composite structures is exponentially growing in different fields due to their higher strength-to-weight ratio. This application trend requires that accurate theoretical explanations and their finite element models be developed for analyzing sandwich plates before finalizing the designs. This paper reviews the recent research trends of finite element formulations developed for analyzing sandwich plates. This paper reviews the finite element models developed after the year 2000. Initially, the finite element formulations based on first order shear deformation theory, higher order shear deformation theories, mixed solid-shell elements, zig-zag theories and global–local theories are presented. Then, some finite element formulations developed to analyze a very new class of structures called piezoelectric structures are presented. At the end, some formulations to analyze a very critical phenomenon called buckling are presented.展开更多
In this paper,the stresses and buckling behaviors of a thick-walled mi-cro sandwich panel with a flexible foam core and carbon nanotube reinforced composite(CNTRC)face sheets are considered based on the high-order she...In this paper,the stresses and buckling behaviors of a thick-walled mi-cro sandwich panel with a flexible foam core and carbon nanotube reinforced composite(CNTRC)face sheets are considered based on the high-order shear deformation theory(HSDT)and the modified couple stress theory(MCST).The governing equations of equi-librium are obtained based on the total potential energy principle.The effects of various parameters such as the aspect ratio,elastic foundation,temperature changes,and volume fraction of the canbon nanotubes(CNTs)on the critical buckling loads,normal stress,shear stress,and deflection of the thick-walled micro cylindrical sandwich panel consider-ing different distributions of CNTs are examined.The results are compared and validated with other studies,and showing an excellent compatibility.CNTs have become very use-ful and common candidates in sandwich structures,and they have been extensively used in many applications including nanotechnology,aerospace,and micro-structures.This paper also extends further applications of reinforced sandwich panels by providing the modified equations and formulae.展开更多
This study determines the natural frequencies of the lock gate structure,considering the coupled effect of reservoir fluid on one side using the finite element method(FEM).The gate is assumed to be a uniformly thick p...This study determines the natural frequencies of the lock gate structure,considering the coupled effect of reservoir fluid on one side using the finite element method(FEM).The gate is assumed to be a uniformly thick plate,and its material is isotropic,homogeneous,and elastic.The reservoir fluid is assumed to be inviscid and incompressible in an irrotational flow field.The length of the reservoir domain is truncated using the far boundary condition by adopting the Fourier series expansion theory.Two different assumptions on the free surface,i.e.,undisturbed and linearized,are considered in the fluid domain analysis.The computer code is written based on the developed finite element formulations.The natural frequencies of the lock gate are computed when interacting with and without reservoir fluid.Several numerical problems are studied considering the effects of boundary conditions,aspect ratios,and varying dimensions of the gate and the fluid domain.The frequencies of gate reduce significantly due to the presence of fluid.The frequencies increase when the fluid extends to either side of the gate.The frequencies reduce when the depth of the fluid domain above the top edge of the gate increases.The frequencies drop considerably when the free surface condition is taken into account.The results of frequencies of lock gate structure may be useful to the designer if it is experienced in natural catastrophes.展开更多
Inspired by the structural adaptations of natural biological organisms,helicoidal composite architectures have shown significant potential for enhancing toughness,strength,and weight efficiency in engineering applicat...Inspired by the structural adaptations of natural biological organisms,helicoidal composite architectures have shown significant potential for enhancing toughness,strength,and weight efficiency in engineering applications.However,temperature and moisture's adverse effects pose challenges during service,potentially compromising their overall performance.This study meticulously analyzes the buckling and vibration behavior of carbon nanotube(CNT)-reinforced bioinspired helicoidal composite plates under different hygrothermal conditions.A novel aspect of this study lies in the proposition of a multiscale analysis combining the analytical and numerical techniques to assess the effects of temperature,moisture,weight fraction of CNTs,layup configurations of bioinspired designs,aspect ratios,loading and boundary conditions,and geometric shapes of bioinspired helicoidal composite structures on their vibration and buckling characteristics.In this context,the stiffness properties are computed with the Halpin-Tsai model,incorporating the size-dependent features of CNTs along with their waviness and agglomeration.In addition,the Chamis micro-mechanical equations are used to determine the elastic properties of individual layers constituting bioinspired composites,considering the effects of temperature and moisture.The kinematics of the laminated bioinspired structures are captured with the third-order shear deformation theory(TSDT)within the isogeometric framework employing the non-uniform rational B-splines(NURBSs)as the basis functions.The isogeometric framework ensures higher-order inter-element continuity and provides an exact geometric representation,offering various advantages over the traditional finite element method.The developed framework is validated against the existing literature,and thereafter several numerical examples are presented,providing valuable insights for the design and optimization of bioinspired composite structures,with potential benefits for various engineering fields,including marine and aerospace sectors.展开更多
基金Project supported by the National Natural Science Foundation of China(Nos.12162004 and 11562001)the Doctoral Research Start-up Fund Project at University of South China(No.Y00043-13)。
文摘This paper presents,for the first time,an effective numerical approach based on the isogeometric analysis(IGA)and the six-variable quasi-three dimensional(3D)higher-order shear deformation theory(HSDT)to study the free vibration characteristics of functionally-graded(FG)graphene origami(GOri)-enabled auxetic metamaterial(GOEAM)plates submerged in a fluid medium.The plate theory incorporates the thickness stretching and the effects of transverse shear deformation without using any shear correction factors.The velocity potential function and Bernoulli's equation are used to derive the hydrodynamic pressure acting on the plate surface.Both horizontally and vertically immersed plate configurations are considered here in the form of inertia effects.The plates are composed of multilayer GOEAMs,with the GOri content varying through the plate's thickness in a layer-wise manner.This design results in graded auxetic growth.The material properties are evaluated by mixing rules and a genetic programming(GP)-assisted micromechanical model.The governing equations of motion for the FG-GOEAM plates immersed in a fluid medium are derived by Hamilton's principle.After validating the convergence and accuracy of the present model,a comprehensive parametric study is carried out to examine the effects of the GOri content,GOri distribution pattern,GOri folding degree,fluid level,immersed depth,and geometric parameter on the natural frequencies of the FG-GOEAM plates.The results show that the natural frequencies for the four GOri distribution patterns increase with the increase in the layer number when the lay number is fewer than 10,and then stabilize after the layer number reaches 10.Besides,in general,the natural frequency of the FG-GOEAM plate in a vacuum or fluid increases when the GOri content increases,while decreases when the GOri folding degree increases.Some additional findings related to the numerical results are presented in the conclusions.It is believed that the present results are useful for the precise design and optimization of FG-GOEAM plates immersed in a fluid medium.
文摘Use of composite structures is exponentially growing in different fields due to their higher strength-to-weight ratio. This application trend requires that accurate theoretical explanations and their finite element models be developed for analyzing sandwich plates before finalizing the designs. This paper reviews the recent research trends of finite element formulations developed for analyzing sandwich plates. This paper reviews the finite element models developed after the year 2000. Initially, the finite element formulations based on first order shear deformation theory, higher order shear deformation theories, mixed solid-shell elements, zig-zag theories and global–local theories are presented. Then, some finite element formulations developed to analyze a very new class of structures called piezoelectric structures are presented. At the end, some formulations to analyze a very critical phenomenon called buckling are presented.
基金the Iranian Nanotechnology Development Committee for their financial supportthe University of Kashan for supporting this work (No. 891238/11)。
文摘In this paper,the stresses and buckling behaviors of a thick-walled mi-cro sandwich panel with a flexible foam core and carbon nanotube reinforced composite(CNTRC)face sheets are considered based on the high-order shear deformation theory(HSDT)and the modified couple stress theory(MCST).The governing equations of equi-librium are obtained based on the total potential energy principle.The effects of various parameters such as the aspect ratio,elastic foundation,temperature changes,and volume fraction of the canbon nanotubes(CNTs)on the critical buckling loads,normal stress,shear stress,and deflection of the thick-walled micro cylindrical sandwich panel consider-ing different distributions of CNTs are examined.The results are compared and validated with other studies,and showing an excellent compatibility.CNTs have become very use-ful and common candidates in sandwich structures,and they have been extensively used in many applications including nanotechnology,aerospace,and micro-structures.This paper also extends further applications of reinforced sandwich panels by providing the modified equations and formulae.
文摘This study determines the natural frequencies of the lock gate structure,considering the coupled effect of reservoir fluid on one side using the finite element method(FEM).The gate is assumed to be a uniformly thick plate,and its material is isotropic,homogeneous,and elastic.The reservoir fluid is assumed to be inviscid and incompressible in an irrotational flow field.The length of the reservoir domain is truncated using the far boundary condition by adopting the Fourier series expansion theory.Two different assumptions on the free surface,i.e.,undisturbed and linearized,are considered in the fluid domain analysis.The computer code is written based on the developed finite element formulations.The natural frequencies of the lock gate are computed when interacting with and without reservoir fluid.Several numerical problems are studied considering the effects of boundary conditions,aspect ratios,and varying dimensions of the gate and the fluid domain.The frequencies of gate reduce significantly due to the presence of fluid.The frequencies increase when the fluid extends to either side of the gate.The frequencies reduce when the depth of the fluid domain above the top edge of the gate increases.The frequencies drop considerably when the free surface condition is taken into account.The results of frequencies of lock gate structure may be useful to the designer if it is experienced in natural catastrophes.
文摘Inspired by the structural adaptations of natural biological organisms,helicoidal composite architectures have shown significant potential for enhancing toughness,strength,and weight efficiency in engineering applications.However,temperature and moisture's adverse effects pose challenges during service,potentially compromising their overall performance.This study meticulously analyzes the buckling and vibration behavior of carbon nanotube(CNT)-reinforced bioinspired helicoidal composite plates under different hygrothermal conditions.A novel aspect of this study lies in the proposition of a multiscale analysis combining the analytical and numerical techniques to assess the effects of temperature,moisture,weight fraction of CNTs,layup configurations of bioinspired designs,aspect ratios,loading and boundary conditions,and geometric shapes of bioinspired helicoidal composite structures on their vibration and buckling characteristics.In this context,the stiffness properties are computed with the Halpin-Tsai model,incorporating the size-dependent features of CNTs along with their waviness and agglomeration.In addition,the Chamis micro-mechanical equations are used to determine the elastic properties of individual layers constituting bioinspired composites,considering the effects of temperature and moisture.The kinematics of the laminated bioinspired structures are captured with the third-order shear deformation theory(TSDT)within the isogeometric framework employing the non-uniform rational B-splines(NURBSs)as the basis functions.The isogeometric framework ensures higher-order inter-element continuity and provides an exact geometric representation,offering various advantages over the traditional finite element method.The developed framework is validated against the existing literature,and thereafter several numerical examples are presented,providing valuable insights for the design and optimization of bioinspired composite structures,with potential benefits for various engineering fields,including marine and aerospace sectors.
