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A deep feed-forward neural network for damage detection in functionally graded carbon nanotube-reinforcedcomposite plates using modal kinetic energy

《结构与土木工程前沿（英文）》 2021年 第15卷 第6期   页码 1453-1479 doi: 10.1007/s11709-021-0767-z

摘要： 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 20 000 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.

关键词： damage detection     deep feed-forward neural networks     functionally graded carbon nanotube-reinforced composite plates     modal kinetic energy    

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Nonlinear dynamic analysis of functionally graded carbon nanotube-reinforced composite plates using MISQ20

《结构与土木工程前沿（英文）》   页码 1072-1085 doi: 10.1007/s11709-023-0951-4

摘要： The main objective of this study is to further extend the mixed integration smoothed quadrilateral element with 20 unknowns of displacement (MISQ20) to investigate the nonlinear dynamic responses of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) plates with four types of carbon nanotube distributions. The smooth finite element method is used to enhance the accuracy of the Q4 element and avoid shear locking without using any shear correction factors. This method yields accurate results even if the element exhibits a concave quadrilateral shape and reduces the error when the element meshing is rough. Additionally, the element stiffness matrix is established by integrating the boundary of the smoothing domains. The motion equation of the FG-CNTRC plates is solved by adapting the Newmark method combined with the Newton–Raphson algorithm. Subsequently, the calculation program is coded in the MATLAB software and verified by comparing it with other published solutions. Finally, the effects of the input parameters on the nonlinear vibration of the plates are investigated.

关键词： carbon nanotube     MISQ20     FG-CNTRC plate     nonlinear vibration     nonlinear dynamic analysis     SFEM    

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A novel finite element formulation for static bending analysis of functionally graded porous sandwichplates

Van Chinh NGUYEN; Trung Thanh TRAN; Trung NGUYEN-THOI; Quoc-Hoa PHAM

《结构与土木工程前沿（英文）》 2022年 第16卷 第12期   页码 1599-1620 doi: 10.1007/s11709-022-0891-4

摘要： This article aims to propose a finite element formulation based on Quasi-3D theory for the static bending analysis of functionally graded porous (FGP) sandwich plates. The FGP sandwich plates consist of three layers including the bottom skin of homogeneous metal, the top skin of fully ceramic and the FGP core layer with uneven porosity distribution. A quadrilateral (Q4) element with nine degrees of freedom (DOFs) per node is derived and employed in analyzing the static bending response of the plate under uniform and/or sinusoidally distributed loads. The accuracy of the present finite element formulation is verified by comparing the obtained numerical results with the published results in the literature. Then, some numerical examples are performed to examine the effects of the parameters including power-law index k and porosity coefficient ξ on the static bending response of rectangular FGP sandwich plates. In addition, a problem with a complicated L-shape model is conducted to illustrate the superiority of the proposed finite element method.

关键词： sandwich plates     functionally graded porous     static bending     Quasi-3D theory     Q4 element    

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Free vibration analysis of functionally graded porous curved nanobeams on elastic foundation in hygro–thermo–magnetic

《结构与土木工程前沿（英文）》 2023年 第17卷 第4期   页码 584-605 doi: 10.1007/s11709-023-0916-7

摘要： Herein, a two-node beam element enriched based on the Lagrange and Hermite interpolation function is proposed to solve the governing equation of a functionally graded porous (FGP) curved nanobeam on an elastic foundation in a hygro–thermo–magnetic environment. The material properties of curved nanobeams change continuously along the thickness via a power-law distribution, and the porosity distributions are described by an uneven porosity distribution. The effects of magnetic fields, temperature, and moisture on the curved nanobeam are assumed to result in axial loads and not affect the mechanical properties of the material. The equilibrium equations of the curved nanobeam are derived using Hamilton’s principle based on various beam theories, including the classical theory, first-order shear deformation theory, and higher-order shear deformation theory, and the nonlocal elasticity theory. The accuracy of the proposed method is verified by comparing the results obtained with those of previous reliable studies. Additionally, the effects of different parameters on the free vibration behavior of the FGP curved nanobeams are investigated comprehensively.

关键词： functionally graded porous material     curved nanobeam     hygro–thermo–magnetic     enriched finite element method    

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

Baoguo MA, Dinghua ZOU, Li XU

《结构与土木工程前沿（英文）》 2009年 第3卷 第1期   页码 101-104 doi: 10.1007/s11709-009-0011-8

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

关键词： shield tunnel     functionally graded concrete segment (FGCS)     manufacturing technology     performance    

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Consumption of carbon fiber plates in the reinforced concrete beams strengthened with CFPs

BU Liangtao, SHI Chuxian, SONG Li

《结构与土木工程前沿（英文）》 2007年 第1卷 第4期   页码 393-398 doi: 10.1007/s11709-007-0053-8

摘要： Four-point bending flexural tests were conducted to one full-size reinforced concrete (RC) beam and three full-size RC beams strengthened with carbon fiber plates (CFPs). The experimental results showed that the consumption of CFP

关键词： flexural     full-size     Four-point     consumption     experimental    

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Strengthening mechanisms in carbon nanotube reinforced bioglass composites

Jing ZHANG, Chengchang JIA, Zhizhong JIA, Jillian LADEGARD, Yanhong GU, Junhui NIE

《化学科学与工程前沿（英文）》 2012年 第6卷 第2期   页码 126-131 doi: 10.1007/s11705-012-1279-0

摘要： Carbon nanotube reinforced bioglass composites have been successfully synthesized by two comparative sintering techniques, i.e., spark plasma sintering (SPS) and conventional compaction and sinteirng. The composites show improved mechanical properties, with SPS technique substantially better than conventional compact and sintering approach. Using SPS, compared with the 45S5Bioglass matrix, the maximum flexural strength and fracture toughness increased by 159% and 105%, respectively. Enhanced strength and toughness are attributed to the interfacial bonding and bridging effects between the carbon nanotubes and bioglass powders during crack propagations.

关键词： 45S5Bioglass     multi-wall carbon nanotubes     biocomposite     mechanical properties     sintering    

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Cross-stacked super-aligned carbon nanotube/activated carbon composite electrodes for efficient water

Min Li, Shuai Liang, Yang Wu, Meiyue Yang, Xia Huang

《环境科学与工程前沿（英文）》 2020年 第14卷 第6期 doi: 10.1007/s11783-020-1286-1

摘要： Abstract • A high-performance electrode was prepared with super-aligned carbon nanotubes. • SACNT/AC electrode achieved a ~100% increase in desalination capacity and rate. • SACNT/AC electrode achieved a ~26% increase in charge efficiency. • CUF process with SACNT/AC achieved an up to 2.43-fold fouling reduction. • SACNT/AC imparts overall improved water purification efficiency. The practical application of the capacitive deionization (CDI) enhanced ultrafiltration (CUF) technology is hampered due to low performance of electrodes. The current study demonstrated a novel super-aligned carbon nanotube (SACNT)/activated carbon (AC) composite electrode, which was prepared through coating AC on a cross-stacked SACNT film. The desalination capability and water purification performance of the prepared electrode were systematically investigated at different applied voltages (0.8–1.2 V) with a CDI system and a CUF system, respectively. In the CDI tests, as compared with the control AC electrode, the SACNT/AC electrode achieved an approximately 100% increase in both maximum salt adsorption capacity and average salt adsorption rate under all the applied voltage conditions, demonstrating a superior desalination capability. Meanwhile, a conspicuous increase by an average of ~26% in charge efficiency was also achieved at all the voltages. In the CUF tests, as compared with the control run at 0 V, the treatment runs at 0.8, 1.0, and 1.2 V achieved a 2.40-fold, 2.08-fold, and 2.43-fold reduction in membrane fouling (calculated according to the final transmembrane pressure (TMP) data at the end of every purification stage), respectively. The average TMP increasing rates at 0.8, 1.0, and 1.2 V were also roughly two times smaller than that at 0 V, indicating a dramatical reduction of membrane fouling. The SACNT/AC electrode also maintained its superior desalination capability in the CUF process, resulting in an overall improved water purification efficiency.

关键词： Carbon nanotube     Super aligned     Conductive membrane     Capacitive deionization     Ultrafiltration     Desalination    

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Static and dynamic analysis of functionally graded fluid-infiltrated porous skew and elliptical nanoplates

《结构与土木工程前沿（英文）》 2023年 第17卷 第3期   页码 477-502 doi: 10.1007/s11709-023-0918-5

摘要： The analysis of static bending and free and forced vibration responses of functionally graded fluid-infiltrated porous (FGFP) skew and elliptical nanoplates placed on Pasternak’s two-parameter elastic foundation is performed for the first time using isogeometric analysis (IGA) based on the non-uniform rational B-splines (NURBSs) basis function. Three types of porosity distributions affect the mechanical characteristics of materials: symmetric distribution, upper asymmetric distribution, and lower asymmetric distribution. The stress–strain relationship for Biot porous materials was determined using the elastic theory. The general equations of motion of the nanoplates were established using the four-unknown shear deformation plate theory in conjunction with the nonlocal elastic theory and Hamilton’s principle. A computer program that uses IGA to determine the static bending and free and forced vibration of a nanoplate was developed on MATLAB software platform. The accuracy of the computational program was validated via numerical comparison with confidence assertions. This set of programs presents the influence of the following parameters on the static bending and free and forced vibrations of nanoplates: porosity distribution law, porosity coefficient and geometrical parameters, elastic foundation, deviation angle, nonlocal coefficient, different boundary conditions, and Skempton coefficients. The numerical findings demonstrated the uniqueness of the FGFP plate’s behavior when the porosities are saturated with liquid compared with the case without liquid. The findings of this study have significant implications for engineers involved in the design and fabrication of the aforementioned type of structures. Furthermore, this can form the basis for future research on the mechanical responses of the structures.

关键词： static bending     free and forced vibrations     nonlocal theory     isogeometric analysis     fluid-infiltrated porous nanoplates    

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Thermal buckling behavior of laminated composite plates: a finite-element study

Houdayfa OUNIS,Abdelouahab TATI,Adel BENCHABANE

《机械工程前沿（英文）》 2014年 第9卷 第1期   页码 41-49 doi: 10.1007/s11465-014-0284-z

摘要：

In this paper, the thermal buckling behavior of composite laminated plates under a uniform temperature distribution is studied. A finite element of four nodes and 32 degrees of freedom (DOF), previously developed for the bending and mechanical buckling of laminated composite plates, is extended to investigate the thermal buckling behavior of laminated composite plates. Based upon the classical plate theory, the present finite element is a combination of a linear isoparametric membrane element and a high precision rectangular Hermitian element. The numerical implementation of the present finite element allowed the comparison of the numerical obtained results with results obtained from the literature: 1) with element of the same order, 2) the first order shear deformation theory, 3) the high order shear deformation theory and 4) the three-dimensional solution. It was found that the obtained results were very close to the reference results and the proposed element offers a good convergence speed. Furthermore, a parametrical study was also conducted to investigate the effect of the anisotropy of composite materials on the critical buckling temperature of laminated plates. The study showed that: 1) the critical buckling temperature generally decreases with the increasing of the modulus ratio EL/ET and thermal expansion ratio αT/αL, and 2) the boundary conditions and the orientation angles significantly affect the critical buckling temperature of laminated plates.

关键词： thermal buckling     laminated composite plates     anisotropy     critical buckling temperature     finite-element method     high precision rectangular Hermitian element    

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Axisymmetric loading on nanoscale multilayered media

《结构与土木工程前沿（英文）》 2023年 第17卷 第1期   页码 152-164 doi: 10.1007/s11709-022-0895-0

摘要： Multilayered nanoscale structures are used in several applications. Because the effect of surface energy becomes nontrivial at such a small scale, a modified continuum theory is required to accurately predict their mechanical behaviors. A Gurtin–Murdoch continuum model of surface elasticity is implemented to establish a computational scheme for investigating an elastic multilayered system under axisymmetric loads with the incorporation of surface/interface energy. Each layer stiffness matrix is derived based on the general solutions of stresses and displacements obtained in the form of the Hankel integral transform. Numerical solutions to the global equation, which are formulated based on the continuity conditions of tractions and displacements across interfaces between layers, yield the displacements at each layer interface and on the top surface of the multilayered medium. The numerical solutions indicate that the elastic responses of multilayered structures are affected significantly by the surface material properties of both the top surface and interfaces, and that they become size dependent. In addition, the indentation problem of a multilayered nanoscale elastic medium under a rigid frictionless cylindrical punch is investigated to demonstrate the application of the proposed solution scheme.

关键词： functionally graded layer     Gurtin–Murdoch surface elasticity     multilayered medium     size dependency     stiffness matrix    

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Finite element analysis of stress concentrations and failure criteria in composite plates with circular

null

《机械工程前沿（英文）》 2014年 第9卷 第3期   页码 281-294 doi: 10.1007/s11465-014-0307-9

摘要：

In this study, the stress concentration factors (SCF) in cross-and-angle-ply laminated composite plates as well as in isotropic plates with single circular holes subjected to uniaxial loading is studied. A quadrilateral finite element of four-node with 32 degrees of freedom at each node, previously developed for the bending and mechanical buckling of laminated composite plates, is used to evaluate the stress distribution in laminated composite plates with central circular holes. Based up on the classical plate theory, the present finite element is a combination of a linear isoparametric membrane element and a high precision rectangular Hermitian element. The numerical results obtained by the present element compare favorably with those obtained by the analytic approaches published in literature. It is observed that the obtained results are very close to the reference results, which demonstrates the accuracy of the present element. Additionally, to determine the first ply failure (FPF) of laminated plate, several failure criterions are employed. Finally, to show the effect of ratio on the failure of plates, a number of figures are given for different fiber orientation angles.

关键词： laminated composite plates     stress concentration     geometric singularity     anisotropic effect    

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Nonpolar cross-stacked super-aligned carbon nanotube membrane for efficient wastewater treatment

《环境科学与工程前沿（英文）》 2023年 第17卷 第3期 doi: 10.1007/s11783-023-1630-3

摘要：

● A novel nonpolar super-aligned carbon nanotube (SACNT) membrane was prepared.

关键词： Membrane fouling     Wastewater     Membrane separation     Antifouling     Aligned carbon nanotube    

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Velocity gradient elasticity for nonlinear vibration of carbon nanotube resonators

Hamid M. SEDIGHI, Hassen M. OUAKAD

《结构与土木工程前沿（英文）》 2020年 第14卷 第6期   页码 1520-1530 doi: 10.1007/s11709-020-0672-x

摘要： In this study, for the first time, we investigate the nonlocality superimposed to the size effects on the nonlinear dynamics of an electrically actuated single-walled carbon-nanotube-based resonator. We undertake two models to capture the nanostructure nonlocal size effects: the strain and the velocity gradient theories. We use a reduced-order model based on the differential quadrature method (DQM) to discretize the governing nonlinear equation of motion and acquire a discretized-parameter nonlinear model of the system. The structural nonlinear behavior of the system assuming both strain and velocity gradient theories is investigated using the discretized model. The results suggest that nonlocal and size effects should not be neglected because they improve the prediction of corresponding dynamic amplitudes and, most importantly, the critical resonant frequencies of such nanoresonators. Neglecting these effects may impose a considerable source of error, which can be amended using more accurate modeling techniques.

关键词： velocity gradient elasticity theory     nanotube resonators     differential-quadrature method     nonlinear vibration    

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The role of ions in plasma catalytic carbon nanotube growth: A review

Erik C. Neyts

《化学科学与工程前沿（英文）》 2015年 第9卷 第2期   页码 154-162 doi: 10.1007/s11705-015-1515-5

摘要： While it is well-known that the plasma-enhanced catalytic chemical vapor deposition (PECVD) of carbon nanotubes (CNTs) offers a number of advantages over thermal CVD, the influence of the various individual contributing factors is not well understood. Especially the role of ions is unclear, since ions in plasmas are generally associated with sputtering rather than with growing a material. Even so, various studies have demonstrated the beneficial effects of ion bombardment during the growth of CNTs. This review looks at the role of the ions in plasma-enhanced CNT growth as deduced from both experimental and simulation studies. Specific attention is paid to the beneficial effects of ion bombardment. Based on the available literature, it can be concluded that ions can be either beneficial or detrimental for carbon nanotube growth, depending on the exact conditions and the control over the growth process.

关键词： plasma-enhanced chemical vapor deposition (PECVD)     carbon nanotube (CNT)     ion bombardment     defect healing    

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标题 作者 时间 类型 操作

A deep feed-forward neural network for damage detection in functionally graded carbon nanotube-reinforcedcomposite plates using modal kinetic energy

期刊论文

Nonlinear dynamic analysis of functionally graded carbon nanotube-reinforced composite plates using MISQ20

期刊论文

A novel finite element formulation for static bending analysis of functionally graded porous sandwichplates

Van Chinh NGUYEN; Trung Thanh TRAN; Trung NGUYEN-THOI; Quoc-Hoa PHAM

期刊论文

Free vibration analysis of functionally graded porous curved nanobeams on elastic foundation in hygro–thermo–magnetic

期刊论文

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

Baoguo MA, Dinghua ZOU, Li XU

期刊论文

Consumption of carbon fiber plates in the reinforced concrete beams strengthened with CFPs

BU Liangtao, SHI Chuxian, SONG Li

期刊论文

Strengthening mechanisms in carbon nanotube reinforced bioglass composites

Jing ZHANG, Chengchang JIA, Zhizhong JIA, Jillian LADEGARD, Yanhong GU, Junhui NIE

期刊论文

Cross-stacked super-aligned carbon nanotube/activated carbon composite electrodes for efficient water

Min Li, Shuai Liang, Yang Wu, Meiyue Yang, Xia Huang

期刊论文

Static and dynamic analysis of functionally graded fluid-infiltrated porous skew and elliptical nanoplates

期刊论文

Thermal buckling behavior of laminated composite plates: a finite-element study

Houdayfa OUNIS,Abdelouahab TATI,Adel BENCHABANE

期刊论文

Axisymmetric loading on nanoscale multilayered media

期刊论文

Finite element analysis of stress concentrations and failure criteria in composite plates with circular

null

期刊论文

Nonpolar cross-stacked super-aligned carbon nanotube membrane for efficient wastewater treatment

期刊论文

Velocity gradient elasticity for nonlinear vibration of carbon nanotube resonators

Hamid M. SEDIGHI, Hassen M. OUAKAD

期刊论文

The role of ions in plasma catalytic carbon nanotube growth: A review

Erik C. Neyts

期刊论文