Smart Layer Research Articles

Vibration analysis of sandwich composite micro-plate under electro-magneto-mechanical loadings

In this research, free vibration of sandwich composite micro-plate (SCMP) made of five smart layers is studied. The core of sandwich is a piezomagnetic micro-plate integrated with two layers of piezoelectric materials. Also the composite layers are placed the top and bottom of structure as the face sheets. The sandwich micro-plate is subjected to electric and magnetic fields besides the compression and extension in-plane forces in both longitudinal and transverse directions. The structure rests on the elastic medium and Pasternak foundation is used for its modeling, including normal and shear modules. First order shear deformation theory is utilized in order to derive the seven coupled equations of motion using Hamilton's principle. These equations are solved by differential quadrature method (DQM). A detailed numerical study is carried out based on Piezoelectricity and modified couple stress theories to indicate the significant effect of length scale parameter, shear correction factor, aspect and thickness ratios, different fiber angles, boundary conditions and electro–magneto-mechanical (EMM) loadings on dimensionless frequency of sandwich composite plate. These finding can be used to automotive, aerospace and building industries.

Nonlinear electromechanical analysis of a functionally graded square plate integrated with smart layers resting on Winkler-Pasternak foundation

This paper presents nonlinear analysis of a functionally graded square plate integrated with two functionally graded piezoelectric layers resting on the Winkler-Pasternak foundation. Geometric nonlinearity was considered in the strain-displacement relation based on the Von-Karman assumption. All the mechanical and electrical properties except Poisson's ratio can vary continuously along the thickness of the plate based on a power function. Electric potential was assumed as a quadratic function along the thickness direction and trigonometric function along the planar coordinate. The effect of non homogeneous index was investigated on the responses of the system. Furthermore, a comprehensive investigation has been performed for studying the effect of two parameters of assumed foundation on the mechanical and electrical components. A comparison between linear and nonlinear responses of the system presents necessity of this study.

A New Method for On-Line Monitoring of Pressure-Retaining Equipment in Nuclear Power Plants

The on-line monitoring technology is very important to keep safe operation of the pressure-retaining equipment in nuclear power plants (NPPs). In this paper, some currently used monitoring methods in NPPs have been studied carefully, their main characteristics have been generalized. It found that some fatigue cracking of the pressure-retaining equipment can’t be effectively monitored by those systems. In order to solve this problem, a multifunctional smart layer has been designed to monitor the pressure-retaining equipment in NPPs. The structure schematic diagram of the smart layer has been drawn and basic functions of the monitoring system have been developed. Some key techniques to apply the smart layer into the on-line monitoring system of the pressure-retaining equipment in NPPs are generalized. It will be a promising method for monitoring the degradation state of pressure-retaining equipment in NPPs.

Research on the Crack Detection of Subway Station Double-Layer Framework Structure Based on ANSYS

By introducing the basic theory of finite element method and commercial software ANSYS, the coupling field modeling theory, according to the structure of three point bending test to establish the finite element model for the electric and mechanical coupling field simulation test structure. At the same time, with the change of load structure deformation, due to smart layer piezoresistive effect, its potential changes, which can be implemented using intelligent layer resistivity changes of structural damage detection and monitoring.

A robust absorbing layer method for anisotropic seismic wave modeling

When applied to wave propagation modeling in anisotropic media, Perfectly Matched Layers (PML) exhibit instabilities. Incoming waves are amplified instead of being absorbed. Overcoming this difficulty is crucial as in many seismic imaging applications, accounting accurately for the subsurface anisotropy is mandatory. In this study, we present the SMART layer method as an alternative to PML approach. This method is based on the decomposition of the wavefield into components propagating inward and outward the domain of interest. Only outgoing components are damped. We show that for elastic and acoustic wave propagation in Transverse Isotropic media, the SMART layer is unconditionally dissipative: no amplification of the wavefield is possible. The SMART layers are not perfectly matched, therefore less accurate than conventional PML. However, a reasonable increase of the layer size yields an accuracy similar to PML. Finally, we illustrate that the selective damping strategy on which is based the SMART method can prevent the generation of spurious S-waves by embedding the source in a small zone where only S-waves are damped.

SMART layers: a simple and robust alternative to PML approaches for elastodynamics

For considering elastic seismic wave propagation in large domains, efficient absorbing boundary conditions are required with numerical modelling in finite domains. Since their introduction by Berenger, the perfectly matched layers (PML) has become the state-of-the art method because of its efficiency and ease of implementation. However, for anisotropic media, theoretical analysis and numerical experiments show that the PML method is amplifying, that is it exhibits numerical instabilities. Numerical experiments can also exhibit numerical instabilities of the PML when dealing with long time simulations even for isotropic media, especially for finite element methods in unstructured grids. Recently, a new method, called SMART layers approach, has been proposed. This method is shown to be stable even for anisotropic media. The drawback is that the SMART layers are not perfectly matched. We have implemented this new approach in a discontinuous Galerkin method and we illustrate that this method does not exhibit numerical instabilities while PML do for an isotropic elastodynamic simulation. We show that this approach is also competitive with respect to the PML method in terms of efficiency and computational cost.

Layer-wise and equivalent single layer models for smart multilayered plates

Layer-wise and equivalent single layer plate models for magneto-electro-elastic multiphysics laminates are presented in a unified framework. They are based on variable kinematics and quasi-static behavior of the electromagnetic fields. The electromagnetic state of each single layer is preliminary determined by solving the corresponding governing equations coupled with the proper interface continuity and external boundary conditions. By so doing, the electromagnetic state is condensed into the plate kinematics and the layer governing equations are inferred by the principle of virtual displacements. This approach identifies effective mechanical layers, which are kinematically equivalent to the original smart layers. These effective layers are characterized by stiffness, inertia and load properties which take the multifield coupling effects into account as their definitions involve the electromagnetic coupling material properties. The layers governing equations are finally assembled enforcing the mechanical interface conditions. This allows to obtain the smart plate resolving system, which involves primary mechanical variables only. Results for thick simply-supported multilayered plates are obtained by an exact closed-form Navier-type solution and compared with benchmark 3D solutions to investigate the features and accuracy of the proposed modeling approach.

Electro-elastic analysis of fiber-reinforced multilayered cylindrical composites with integrated piezoelectric actuators

Based on the electro-mechanical coupling theory and the laminate elasticity theory, an electro-elastic solution is obtained for the fiber-reinforced cylindrical composites with integrated piezoelectric actuators when subjected to mechanical and electrical loadings. The hybrid composite is composed of three parts: internal piezoelectric actuator, fiber-reinforced laminated interlayer, and external piezoelectric actuator. The general solution in each piezoelectric smart layer is obtained by introducing three undetermined constants, and the general solutions in the fiber-reinforced laminated interlayer are obtained by means of the state-space method. The mechanical behaviors of the hybrid fiber-reinforced cylindrical composites are investigated. The illustrative examples show that the fiber’s angle, the stacking sequence as well as the applied electric loading strongly affect the physical fields in the fiber-reinforced multilayered cylindrical composites.

Application of sensor technologies for local and distributed structural health monitoring

SUMMARY The work presented in this paper deals with the application of different sensor technologies for fatigue crack damage monitoring of metallic helicopter fuselages. A test programme has been conducted, consisting of seven fatigue crack propagation tests on aluminium panels (skin with riveted stringers) representative of the rear fuselage of a helicopter. Electrical crack gauges and comparative vacuum monitoring sensors have been used locally to monitor propagating cracks. A network of optical fibre Bragg gratings is presented as a valid possibility for distributed monitoring (based on strain field dependence on damage), alternative to consolidated electrical resistance-based strain gauges. A Smart Layer based on piezoelectric transducers that emit and receive Lamb wave signals has also been analysed in this paper for distributed monitoring. Two damages have been considered: a skin crack artificially initiated on a panel bay and a skin crack propagating from a rivet hole after stringer failure. Damage sensitivity has been evaluated and compared among the considered technologies, thus providing useful recommendations for each considered system, together with advantages and drawbacks concerning their suitability for on-board installation and monitoring. The damage index sensitivity to operative condition, load in particular, is verified and compared with damage effect for distributed networks. A finite element model able to describe any selected feature sensitivity to the monitored damage is also presented as a useful tool for the optimization of the structural health monitoring system design process. Copyright © 2013 John Wiley & Sons, Ltd.

On Health Monitor Technology Development for Damaged Aircraft Structures

This paper seeks to outline the concept and application of health monitoring system in aircraft structure. The focus is placed on the principles and methods of the structural health monitoring system, including SMART layers, electric potential method, Acoustic Emission, etc. The difference between the above monitoring methods is justified and clarified. Finally a perspective view on structural health monitor techniques is discussed.

Active control of acoustic radiation from laminated cylindrical shells integrated with a piezoelectric layer

Active control of sound radiation from piezoelectric laminated cylindrical shells is theoretically investigated in the wavenumber domain. The governing equations of the smart cylindrical shells are derived by using first-order shear deformation theory. The smart layer is divided into lots of actuator patches, each of which is coated with two very thin electrodes at its inner and outer surfaces. Proportional derivative negative feedback control is applied to the actuator patches and the stiffness of the controlled layer is derived in the wavenumber domain. The equivalent driving forces and moments generated by the piezoelectric layer can produce distinct sound radiation. Large actuator patches cause strong wavenumber conversion and fluctuation of the far-field sound pressure, and do not make any contribution to sound reduction. Nevertheless, suitable small actuator patches induce weak wavenumber conversion and play an important role in the suppression of vibration and acoustic power. The derivative gain of the active control can effectively suppress sound radiation from smart cylindrical shells. The effects of small proportional gain on the sound field can be neglected, but large proportional gain has a great impact on the acoustic radiation of cylindrical shells. The influence of different piezoelectric materials on the acoustic power is described in the numerical results.

902 スマートレイヤを用いた多点パルスエコー法による欠陥同定

902 スマートレイヤを用いた多点パルスエコー法による欠陥同定

Layer alignment tooling and bonding process for the fully dense freeform fabrication (FDFF) adaptive layering process

The Fully Dense Freeform Fabrication (FDFF) process utilises an adaptive layering method for predefined sheets and uses slices cut by an abrasive waterjet cutter or laser cutter machine for manufacturing functional parts through smart layer alignment and compatible bonding materials. Under pressure and heat, layers are attached and form a 3D prototype from a fully dense material. This paper presents an integrated alignment and compression bonding mechanism that is functional for a variety of complex parts. It also explores the benefits of using induction heaters to reach the brazing quality layer bonding heat for the metallic parts. Finally, feasible settings for producing functional metallic parts for variety of geometries and materials are presented.

Temperature Sensibility of Epoxy-Matrix Carbon Fiber Smart Layer

The paper deals with the temperature sensitivity of a new type strain sensor named carbon fiber smart layer (CFSL) made of epoxy-matrix composites with short carbon fiber mats. The experiment result indicated that the epoxy matrix CFSL is sensitive to temperature variation. It exhibits NTC effect in -5°C~25°C and exhibits PTC effect in 25°C~50°C. The NTC effect is relatively gentle and the PTC effect is relatively dramatic. The mechanism of both NTC effect and PTC effect is discussed based on the temperature sensitivities of carbon fiber itself and the fiber to fiber interface. Further experiment demonstrated its temperature sensing properties in the temperature scale in which the NTC effect or PTC effect exhibits individually.

Studying the nonlinear behavior of the functionally graded annular plates with piezoelectric layers as a sensor and actuator under normal pressure

The present paper deals with the nonlinear analysis of the functionally graded piezoelectric (FGP) annular plate with two smart layers as sensor and actuator. The normal pressure is applied on the plate. The geometric nonlinearity is considered in the strain-displacement equations based on Von-Karman assumption. The problem is symmetric due to symmetric loading, boundary conditions and material properties. The radial and transverse displacements are supposed as two dominant components of displacement. The constitutive equations are derived for two sections of the plate, individually. Total energy of the system is evaluated for elastic solid and piezoelectric sections in terms of two components of displacement and electric potential. The response of the system can be obtained using minimization of the energy of system with respect to amplitude of displacements and electric potential. The distribution of all material properties is considered as power function along the thickness direction. Displacement-load and electric potential-load curves verify the nonlinearity nature of the problem. The response of the linear analysis is investigated and compared with those results obtained using the nonlinear analysis. This comparison justifies the necessity of a nonlinear analysis. The distribution of the displacements and electric potential in terms of non homogenous index indicates that these curves converge for small value of piezoelectric thickness with respect to elastic solid thickness.

Non linear analysis of a functionally graded square plate with two smart layers as sensor and actuator under normal pressure

Abstract. The present paper addresses the nonlinear response of a FG square plate with two smart layers asa sensor and actuator under pressure. Geometric nonlinearity was considered in the strain-displacement relationbased on the Von-Karman assumption. All the mechanical and electrical properties except Poisson’s ratio canvary continuously along the thickness of the plate based on a power function. Electric potential was assumedas a quadratic function along the thickness direction and trigonometric function along the planar coordinate.By evaluating the mechanical and electrical energy, the total energy equation can be minimized with respect toamplitude of displacements and electrical potential. The effect of non homogenous index was investigated onthe responses of the system. Obtained results indicate that with increasing the non homogenous index, thedisplacements and electric potential tend to an asymptotic value. Displacements and electric potential can bepresented in terms of planar coordinate system. A linear analysis was employed and then the achieved resultsare compared with those results that are obtained using the nonlinear analysis. The effect of the geometricnonlinearity is investigated by using the comparison between the linear and nonlinear results. Displacement-load and potential-load curves verified the necessity of a nonlinear analysis rather than a linear analysis.Improvement of the previous results (by the linear analysis) through employing a nonlinear analysis can bepresented as novelty of this study. Keywords: plate; mechanical properties; electrical properties; nonlinear; functionally graded material;piezoelectric; sensor.

Resistance Responses of Polymer-Matrix Carbon Fiber Smart Layer to Normal Strain and Shear Strain

The paper makes a comprehensive study on the sensitivity of a new type strain sensor named polymer-matrix carbon fiber smart layer. The sensitivity to tensile strain was gained by a uniaxial tension test. By a three-point bending test on a FRP bar stuck by the smart layer, the sensitivity to compressive strain was revealed and a lower gauge factor was obtained compared to the sensitivity to tensile strain. In addition, a pure shearing test was designed, revealing the sensitivity to shear strain.

Study on ERT System of Smart Layer of Carbon Fiber Composite

Electrical resistance tomography (ERT) is always used in the field of detection of medicine、prospecting、two phase flow at the present time. It is rarely used to measure structure under condition of loading. In this paper, with the characters of different response - resistance effect showed by carbon fiber felt when attached to the different matrix, we developed a new type of smart layer of carbon fiber composites, the composite material has a very high pressure-resistance sensitivity, combined with ERT technology, the structure surface electrical resistivity distribute can be conversed, thus the structure of the surface of the load situation can be analyzed.

Study on Electrical Resistance Tomography Simulation of Carbon Fiber Smart Layers on Two-Dimensional Curved Surface

Based on the piezoresistive function character and the conductivity of carbon fiber smart layer (CFSL), a novel electrical resistance tomography (ERT) system of spherical and cylindrical CFSL has been developed for global health monitoring. Based on the background of the third generation nuclear containment vessel, CFSL is stuck on the surface of the structure, and the effectiveness of the ERT system is verified by virtual experiment. The image reconstruction results show that CFSL on two-dimensional curved surface has good sensing characteristics in the complex strain state. Compared with structural volumetric strain in the monitoring area, it indicates that the high electrical resistance of CFSL is distributed in the high strain area of structures, and the low electrical resistance of CFSL is just distributed in the low strain area of structures. Therefore the resistivity’s distribution of CFSL can reflect qualitatively the structural volumetric strain field.

1013 スマートレイヤを用いた多点パルスエコー法による3次元き裂同定(OS10.逆問題解析手法の開発と最新応用(3),OS・一般セッション講演)

1013 スマートレイヤを用いた多点パルスエコー法による3次元き裂同定(OS10.逆問題解析手法の開発と最新応用(3),OS・一般セッション講演)