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دسترسی آزاد مقاله
1 - Cellular polypropylene electromechanical properties: exploring the nonlinear region
Pavlos Sgardelis Michele PozziAbstractMany studies have been conducted in the last decades on cellular polypropylene (Cell-PP) films. Most of them focus on the optimisation of the material for sensor applications. Processed under Gas Diffusion Expansion (GDE), Cell-PP films show high piezoelectric a چکیده کاملAbstractMany studies have been conducted in the last decades on cellular polypropylene (Cell-PP) films. Most of them focus on the optimisation of the material for sensor applications. Processed under Gas Diffusion Expansion (GDE), Cell-PP films show high piezoelectric activity and low stiffness/density, properties that make them ideal for sensors. GDE increases the height and decreases the length over height ratio (aspect ratio) of individual voids within the material. This change in void morphology, and eventually stiffness, results in a nonlinear piezoelectric response of these materials. In this study, a Cell-PP sample was tested under static, quasi-static and low-frequency compressive stress. The main aim is to evaluate its mechanical and piezoelectric properties in the nonlinear region of its response over strain. The load–deflection curves as well as the piezoelectric responses were obtained for stresses up to 270 kPa (engineering strain close to 0.26). It is shown that both the magnitude of the initial load and the strain rate have a critical effect on the creep/stress relaxation of the film and eventually on its piezoelectric response. Finally, it is shown that under dynamic conditions, and for the same engineering strain region, it is more relevant to present the piezoelectric response, in terms of strain rather than stress. پرونده مقاله -
دسترسی آزاد مقاله
2 - طراحی سازه های پیش ساخته و پایدار با رسوب نمک با الهام از الگوی بهینه سازی مصرف مصالح در استخوان ترابکولار انسان
آذین جلالی محمود گلابچیمعماری بیونیک، رویکرد نوینی در جهان معاصر است که از راه حل های پایدار طبیعت برای پاسخگویی به مشکلات انسان بهره میبرد. برای حل مشکل استخراج بیش از حد مصالح از محیط زیست که یکی از عوامل ایجاد کننده ناپایداری در صنعت ساخت و ساز و معماری است، به کشف و بازخوانی راه حل بهینه چکیده کاملمعماری بیونیک، رویکرد نوینی در جهان معاصر است که از راه حل های پایدار طبیعت برای پاسخگویی به مشکلات انسان بهره میبرد. برای حل مشکل استخراج بیش از حد مصالح از محیط زیست که یکی از عوامل ایجاد کننده ناپایداری در صنعت ساخت و ساز و معماری است، به کشف و بازخوانی راه حل بهینه سازی مصرف مصالح در طبیعت پرداخته میشود. سازه های طبیعی، مانند استخوان انسان، بتدریج مصالح خود را از محیط استخراج میکنند. چگونگی شبیه سازی ساختار پیش ساخته هوشمند که توانایی تخریب و ترمیم خود را دارد و به مرور زمان با جذب مصالح از محیط اطراف خود، رشد می یابند ارائه می شود. آبهای خلیج فارس و دریاچه ارومیه با بحران شورشدگی بیش از حد مواجه اند. استخراج نمک، به عنوان مصالح تکمیل کننده، از آب شور و برگرداندن آب با غلظت کمتر ، پایداری زیست محیطی این روش ساخت و ساز را تامین میکند. پرونده مقاله -
دسترسی آزاد مقاله
3 - Several Horizontal and Vertical Cracks in a Piezoelectric Rectangular Plane
R BagheriIn this article, using the method of dislocation distribution and separation of variables, the mechanical fracture behavior of a thin rectangular plane made of piezoelectric material with limited length and width containing several cracks under out-of-plane mechanical a چکیده کاملIn this article, using the method of dislocation distribution and separation of variables, the mechanical fracture behavior of a thin rectangular plane made of piezoelectric material with limited length and width containing several cracks under out-of-plane mechanical and in-plane electrical loading is investigated. It is assumed that the behavior of the elastic medium is linear and the surfaces of the cracks are smooth. At first, the governing equations of the problem are solved according to the boundary conditions, and then the components of stress and electrical displacement in the body without cracks under external loading at the hypothetical crack location are presented. Then, according to Buckner's principle, the stress field obtained in the main problem and using the dislocation distribution method, the equations for analyzing the problem of several cracks are presented. By solving these equations and obtaining the distribution functions of dislocations, it is possible to obtain the stress and electric displacement factors at the tips of cracks. In this article, examples are given to verify the results and also to investigate the effects of the length, arrangement and interaction between the cracks on the field intensity factors پرونده مقاله -
دسترسی آزاد مقاله
4 - Review of Smart Metallic Materials Classification
H Sabet B Karbakhsh RavariAlong with material science progress, many new high-quality and cost-effective engineering materials have been introduced in various fields. Smart materials are the new generation of materials superior to construction and commonly used materials. With their inherent int چکیده کاملAlong with material science progress, many new high-quality and cost-effective engineering materials have been introduced in various fields. Smart materials are the new generation of materials superior to construction and commonly used materials. With their inherent intelligence, these materials can adapt to external stimuli such as loads or the environment. Smart materials refer to those materials that understand and react to their environment and surrounding conditions. The crystal structure of these materials responds to applied force (mechanical, electrical, magnetic, etc.). According to NASA's definition, smart materials remember positions and can return to them with certain stimuli. Smart materials are used in systems whose inherent properties can be changed to achieve the required performance. In this article, while introducing the application and development of memory metal smart materials, the relationship between the development of advancing technologies and the development and application of this class of material is discussed. پرونده مقاله -
دسترسی آزاد مقاله
5 - Modelling of Non-Uniform Piezoelectric Micro-Cantilever in Different Environments
Mitra Taghizade A. H. Korayem M. H. KorayemIn recent years, Atomic Force Microscopy (AFM) has been known as a powerful and efficient tool for surface imaging in different environment. To enhance image quality and more precise prediction of Micro-cantilever (MC) behaviour, accuracy in the MC modeling and simulati چکیده کاملIn recent years, Atomic Force Microscopy (AFM) has been known as a powerful and efficient tool for surface imaging in different environment. To enhance image quality and more precise prediction of Micro-cantilever (MC) behaviour, accuracy in the MC modeling and simulation and detecting the MC sensitivity to geometric parameters has great importance. To model the vibration motion of the AFM non-uniform piezoelectric MC, Timoshenko beam theory is used in order to consider the effect of shear effect in air and liquid environment. In addition, the effect of the forces imposed by the ambient and sample surface is considered. Frequency response has been studied in the air and different liquid environments and the obtained results have been compared with experiential results as well as with results obtained from Euler-Bernoulli beam theory that is reflective of higher precision exercised in the modeling in respect to Euler-Bernoulli beam theory. Efast statistical method, which is found efficient and quick in the survey of linear and nonlinear models and takes the inter-parameter coupling effect into consideration besides calculating the sensitivities unique to each of the factors, has been applied in order to analyse the geometrical parameters’ effects on the MC natural frequencies in the air and water environments. پرونده مقاله -
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6 - Vibration Sensitivity Analysis of Nano-mechanical Piezo-Laminated Beams with Consideration of Size Effects
mostafa nazemizadeh Firooz Bakhtiari-Nejad Behrooz ShahriariThe presented article investigates vibration sensitivity analysis of Nano-mechanical piezo-laminated beams with consideration of size effects. To do this, the vibration governing equation of the stepped Nano-mechanical piezo-laminated beam is firstly derived by implemen چکیده کاملThe presented article investigates vibration sensitivity analysis of Nano-mechanical piezo-laminated beams with consideration of size effects. To do this, the vibration governing equation of the stepped Nano-mechanical piezo-laminated beam is firstly derived by implementation of the nonlocal elasticity theory. The nonlocal formulation is considered for both of the beam and the piezoelectric layer and the obtained equation is solved analytically. Moreover, there is a need to recognize the importance and relative effects of the beam parameters on the natural frequencies and resonant amplitudes of the nonlocal beam. Therefore, the Sobol sensitivity analysis is utilized to investigate the relative effects of geometrical and the nonlocal parameters on the natural frequencies and the resonant amplitude of the nanobeam. The obtained results show that the length and the thickness of the piezoelectric layer have prominent effects on the vibration characteristics of the beam. Moreover, it is indicated that nonlocal parameter effect on the resonant amplitudes is more than resonant frequency. Also, the effect of the nonlocal term is more important at higher modes of vibration. Therefore, the nonlocal size effects cannot be ignored in vibration analysis of the nanobeam especially at higher modes. پرونده مقاله -
دسترسی آزاد مقاله
7 - Sensitivity Analysis of Piezoelectric Microcantilever Excitability as Resonator
Reza GhaderiPiezoelectric Microcantilevers (MCs) are efficient tools in switches of MEMS, AFMs and nano-resonators. Creating maximum vibrating motion with minimum excitation voltage is important in reducing power consumption and noise in this type of MCs. Therefore, investigating t چکیده کاملPiezoelectric Microcantilevers (MCs) are efficient tools in switches of MEMS, AFMs and nano-resonators. Creating maximum vibrating motion with minimum excitation voltage is important in reducing power consumption and noise in this type of MCs. Therefore, investigating the factors affecting the excitability of MCs, as well as the degree of the effect of each of these factors, have an important role in the design and optimal selection of this type of resonators. Therefore, the aim of this paper was to investigate the excitability of this type of MCs. Modeling is conducted according to Hamilton principle and Euler-Bernoulli theory. Equation of motion was solved using Galerkin method with respect to geometrical discontinuities. Finally, eFAST sensitivity analysis was performed on excitability of MCs using statistical methods. Sensitivity analysis results show that the length and thickness of the piezoelectric layer are the most influential parameters on the excitability of MCs. At L1/L=0.74, the excitability reaches its maximum value. پرونده مقاله -
دسترسی آزاد مقاله
8 - Analytical and Numerical Study of Pre-Stress Effect in Piezoelectric Sandwich Type Ultrasonic Transducer
Hamidreza Nadri Mahdi Shaban Abbas PakIn this paper, the effect of pre-stress condition on the resonance frequency of the transducer is studied by using numerical and analytical methods. To compare the obtained results, two sandwich-type transducers with nominal frequency of 25 kHz and 30 kHz are considered چکیده کاملIn this paper, the effect of pre-stress condition on the resonance frequency of the transducer is studied by using numerical and analytical methods. To compare the obtained results, two sandwich-type transducers with nominal frequency of 25 kHz and 30 kHz are considered. Experimental determination of pre-stress value in transducer is described and measured. Then resonance frequency of transducers in the presence of pre-stress is determined by impedance analyser. Numerical analysis is conducted by modelling three-dimensional transducer in details at ABAQUS software. The resonance frequency is determined with and without pre-stress. The FE results show that by applying pre-stress on the transducers, the resonance frequency of transducers decreased. Furthermore, the FE results are very close to experimental results. Furthermore, a systematic analytical solution is presented based on one-dimensional wave propagation. The resultant displacement for each sub-section of the transducer is calculated and then all of them are assembled and solved by considering the continuity conditions of displacement and force components. It is found that pre-load condition that is produced by central bolt reduces resonance frequency of the transducer. The obtained analytical results provide fast and reliable model for predicting resonance frequency of transducer. پرونده مقاله -
دسترسی آزاد مقاله
9 - Vibration Analysis and Sensitivity Analysis of Semi-Submerged Multilayer Piezoelectric Microcantilever
Mohamadreza Khosravi Reza GhaderiThe growing development of nanobiotechnology and its applicability resulted in a wider range of use of Microcantilevers (MCs) in liquid. Considering the applications of piezoelectric MCs in the microelectromechanical systems and Atomic Force Microscope (AFM), as well as چکیده کاملThe growing development of nanobiotechnology and its applicability resulted in a wider range of use of Microcantilevers (MCs) in liquid. Considering the applications of piezoelectric MCs in the microelectromechanical systems and Atomic Force Microscope (AFM), as well as the high performance of these beams, this article investigates the vibrating behavior of multilayer piezoelectric MCs with geometric discontinuity in liquid environment. Due to the extreme complexity of hydrodynamic forces introduced to MCs, this force may reduce their accuracy. As a result, the MC was considered to be semi-submerged in the liquid medium to reduce the effect of hydrodynamic force. In addition, to reduce the effect of hydrodynamic force on vibrating behavior of the MC, sensitivity analysis was performed on its geometric dimensions to obtain the optimal dimensions, aiming at minimizing the effect of this force. The differential equation of motion was derived using the Euler–Bernoulli theory and the Lagrange method. The hydrodynamic force was exerted on the MC through the sphere string model. The Simulation results indicated that due to reducing resonance frequency variations in the third vibrating mode, the effect of hydrodynamic force on vibrating motion is minimized in this mode and considered as the optimal vibrating mode among the first three modes. The sensitivity analysis results showed that the MC length and piezoelectric layer were geometric parameters with the greatest effect on frequency sensitivity of MC, which should be considered in semi-submerged piezoelectric MC design. پرونده مقاله -
دسترسی آزاد مقاله
10 - Vibration Analysis of Size-Dependent Piezoelectric Nanobeam Under Magneto-Electrical Field
M Ghadiri M Karimi Asl M NorooziThe damping vibration characteristics of magneto-electro-viscoelastic (MEV) nanobeam resting on viscoelastic foundation based on nonlocal strain gradient elasticity theory (NSGT) is studied in this article. For this purpose, by considering the effects of Winkler-Pastern چکیده کاملThe damping vibration characteristics of magneto-electro-viscoelastic (MEV) nanobeam resting on viscoelastic foundation based on nonlocal strain gradient elasticity theory (NSGT) is studied in this article. For this purpose, by considering the effects of Winkler-Pasternak, the viscoelastic medium consists of linear and viscous layers. with respect to the displacement field in accordance with the refined shear deformable beam theory (RSDT) and the Kelvin-Voigt viscoelastic damping model, the governing equations of motion are obtained using Hamilton’s principle based on nonlocal strain gradient theory (NSGT). Using Fourier Series Expansion, The Galerkin’s method adopted to solving differential equations of nanobeam with both of simply supported and clamped boundary conditions. Numerical results are obtained to show the influences of nonlocal parameter, the length scale parameter, slenderness ratio and magneto-electro-mechanical loadings on the vibration behavior of nanobeam for both types of boundary conditions. It is found that by increasing the magnetic potential, the dimensionless frequency can be increased for any value of the damping coefficient and vice versa. Moreover, negative/positive magnetic potential decreases/increases the vibration frequencies of thinner nanobeam. Also, the vibrating frequency decreases and increases with increasing nonlocal parameter and length scale parameter respectively. پرونده مقاله -
دسترسی آزاد مقاله
11 - Free Vibration Analysis of Functionally Graded Piezoelectric Material Beam by a Modified Mesh Free Method
M Foroutan Sh Sharafi S MohammadiA mesh-free method based on moving least squares approximation (MLS) and weak form of governing equations including two dimensional equations of motion and Maxwell’s equation is used to analyze the free vibration of functionally graded piezoelectric material (FGPM چکیده کاملA mesh-free method based on moving least squares approximation (MLS) and weak form of governing equations including two dimensional equations of motion and Maxwell’s equation is used to analyze the free vibration of functionally graded piezoelectric material (FGPM) beams. Material properties in beam are determined using a power law distribution. Essential boundary conditions are imposed by the transformation method. The mesh-free method is verified by comparison with a finite element method (FEM) which performed for FGPM beams. Comparisons showed that this model has a good accuracy. After validation of the presented model, a parametric study was carried out to investigate the effect of mechanical and electrical boundary conditions, slenderness ratio and distribution of constituent materials on natural frequencies of FGPM beams. It is concluded that slenderness ratio has more significant effect on lower frequencies. On the other hand higher frequencies are affected by the volume fraction power index much more than lower frequencies. پرونده مقاله -
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12 - Effect of Micropolarity on the Propagation of Shear Waves in a Piezoelectric Layered Structure
R Kumar K Singh D.S PathaniaThis paper studies the propagation of shear waves in a composite structure consisting of a piezoelectric layer perfectly bonded over a micropolar elastic half space. The general dispersion equations for the existence of shear waves are obtained analytically in the close چکیده کاملThis paper studies the propagation of shear waves in a composite structure consisting of a piezoelectric layer perfectly bonded over a micropolar elastic half space. The general dispersion equations for the existence of shear waves are obtained analytically in the closed form. Some particular cases have been discussed and in one special case the relation obtained is in agreement with existing results of the classical –Love wave equation. The micropolar and piezoelectric effects on the phase velocity are obtained for electrically open and mechanically free structure. To illustrate the utility of the problem numerical computations are carried out by considering PZT-4 as a piezoelectric and aluminium epoxy as micropolar elastic material. It is observed that the micropolarity present in the half space influence the phase velocity significantly in a particular region. The micropolar effects on the phase velocity in the piezoelectric coupled structure can be used to design high performance acoustic wave devices. پرونده مقاله -
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13 - Method of Green’s Function for Characterization of SH Waves in Porous-Piezo Composite Structure with a Point Source
S Karmakar Sanjeev A Sahu S NirwalAn approach of Green’s function is adopted to solve the inhomogeneous linear differential equations representing wave equations in piezo-composite materials. In particular, transference of horizontally polarised shear (SH) waves is considered in bedded structure c چکیده کاملAn approach of Green’s function is adopted to solve the inhomogeneous linear differential equations representing wave equations in piezo-composite materials. In particular, transference of horizontally polarised shear (SH) waves is considered in bedded structure comprising of porous-piezo electric layer lying over a heterogeneous half-space. Propagation of SH-waves is considered to be influenced by point source, situated in the heterogeneous substrate. A closed form analytical solution is obtained to establish the dispersion relation. Remarkable influence of different parameters (like elastic constant, piezoelectric constant, heterogeneity parameter, initial stress and layers thickness) on the phase and group velocity are shown graphically. Moreover, a special case of present study is shown by replacing the porous piezoelectric material with piezoelectric material. Some numerical examples are illustrated by taking the material constants of Lead Zirconate Titanate (PZT-1, PZT-5H and PZT-7) for the porous piezoelectric layer where the phase velocity of SH waves is high rather than that of piezoelectric layer. پرونده مقاله -
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14 - Size-Dependent Vibration Problem of Two Vertically-Aligned Single-Walled Boron Nitride Nanotubes Conveying Fluid in Thermal Environment Via Nonlocal Strain Gradient Shell Model
P Roodgar Saffari M Fakhraie M. A RoudbariThe free vibration behavior of two fluid-conveying vertically-aligned single-walled boron nitride nanotubes are studied in the present paper via the nonlocal strain gradient piezoelectric theory in conjunction with the first-order shear deformation shell assumption in t چکیده کاملThe free vibration behavior of two fluid-conveying vertically-aligned single-walled boron nitride nanotubes are studied in the present paper via the nonlocal strain gradient piezoelectric theory in conjunction with the first-order shear deformation shell assumption in thermal environments. It is supposed that the two adjacent boron nitride nanotubes are coupled with each other in the context of linear deformation by van der Waals interaction according to Lennard–Jones potential function. To achieve a more accurate modeling for low-scale structures, both hardening and softening effects of materials are considered in the nonlocal strain gradient approach. Themotion equations and associated boundary conditions are derived by means of Hamilton’s variational principle, then solved utilizing differential quadrature method. Numerical studies are done to reveal the effect of different boundary conditions, size scale parameters, aspect ratio, inter-tube distance, and temperature change on the variations of dimensionless eigenfrequency and critical flow velocity. پرونده مقاله -
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15 - Non-Linear Response of Torsional Buckling Piezoelectric Cylindrical Shell Reinforced with DWBNNTs Under Combination of Electro-Thermo-Mechanical Loadings in Elastic Foundation
M Sarvandi M.M Najafizadeh H SeyyedhasaniNanocomposites provide new properties and exploit unique synergism between materials. Polyvinylidene fluoride (PVDF) is an ideal piezoelectric matrix applicable in nanocomposites in a broad range of industries from oil and gas to electronics and automotive. And boron ni چکیده کاملNanocomposites provide new properties and exploit unique synergism between materials. Polyvinylidene fluoride (PVDF) is an ideal piezoelectric matrix applicable in nanocomposites in a broad range of industries from oil and gas to electronics and automotive. And boron nitride nanotubes (BNNTs) show high mechanical, electrical and chemical properties. In this paper, the critical torsional load of a composite tube made of PVDF reinforced with double-walled BNNTs is investigated, under a combination of electro-thermo-mechanical loading. First, a nanocomposite smart tube is modeled as an isotropic cylindrical shell in an elastic foundation. Next, employing the classical shell theory, strain-displacement equations are derived so loads and moments are obtained. Then, the total energy equation is determined, consisting of strain energy of shell, energy due to external work, and energy due to elastic foundation. Additionally, equilibrium equations are derived in cylindrical coordinates as triply orthogonal, utilizing Euler equations; subsequently, stability equations are developed through the equivalent method in adjacent points. The developed equations are solved using the wave technique to achieve critical torsional torque. Results indicated that critical torsional buckling load occurred in axial half-wave number m = 24 and circumferential wave number n = 1, for the investigated cylindrical shell. The results also showed that with the increase in the length-to-radius ratio and in the radius-to-shell thickness ratio, the critical torsional buckling load increased and decreased, respectively. Lastly, results are compared in various states through a numerical method. Moreover, stability equations are validated via comparison with the shell and sheet equations in the literature. پرونده مقاله -
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16 - In-Plane Analysis of an FGP Plane Weakened by Multiple Moving Cracks
R Bagheri M Mahmoudi MonfaredIn this paper, the analytical solution of an electric and Volterra edge dislocation in a functionally graded piezoelectric (FGP) medium is obtained by means of complex Fourier transform. The system is subjected to in-plane mechanical and electrical loading. The material چکیده کاملIn this paper, the analytical solution of an electric and Volterra edge dislocation in a functionally graded piezoelectric (FGP) medium is obtained by means of complex Fourier transform. The system is subjected to in-plane mechanical and electrical loading. The material properties of the medium vary exponentially with coordinating parallel to the crack. In this study, the rate of the gradual change of the shear moduli and mass density is assumed to be same. At first, the Volterra edge dislocation solutions are employed to derive singular integral equations in the form of Cauchy singularity for an FGP plane containing multiple horizontal moving cracks. Then, these equations are solved numerically to obtain dislocation density functions on moving crack surfaces. Finally, the effects of the crack moving velocity, material properties, electromechanical coupling factor and cracks arrangement on the normalized mode I and mode II stress intensity factors and electric displacement intensity factor are studied. پرونده مقاله -
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17 - Free Vibration and Transient Response of Heterogeneous Piezoelectric Sandwich Annular Plate Using Third-Order Shear Deformation Assumption
P Roodgar Saffari M Fakhraie M.A RoudbariBased on the third-order shear deformation theory (TSDT), this paper numerically investigates the natural frequencies and time response of three-layered annular plate with functionally graded materials (FGMs) sheet core and piezoelectric face sheets, under initial exter چکیده کاملBased on the third-order shear deformation theory (TSDT), this paper numerically investigates the natural frequencies and time response of three-layered annular plate with functionally graded materials (FGMs) sheet core and piezoelectric face sheets, under initial external electric voltage. The impressive material specifications of FGM core are assumed to vary continuously across the plate thickness utilizing a power law distribution. The equilibriumequations are obtained employing Hamilton’s method and then solved applying differential quadrature method (DQM) in conjunction with Newmark-β. Numerical studies are carried out to express the influences of the external electric voltage, aspect ratio, and material gradient on the variations of the natural frequencies and time response curves of FGM piezoelectric sandwich annular plate. It is precisely shown that these parameters have considerable effects on the free vibration and transient response. پرونده مقاله -
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18 - Elasticity Exact Solution for an FGM Cylindrical Shaft with Piezoelectric Layers Under the Saint-Venant Torsion by Using Prandtl’s Formulation
M. R Eslami M Jabbari A Eskandarzadeh SabetFunctionally graded materials (FGMs) belong to a noble family of composite material possess material properties varying gradually in a desired direction or orientation. In a past decade, functionally graded materials were remained in an interest of material investigator چکیده کاملFunctionally graded materials (FGMs) belong to a noble family of composite material possess material properties varying gradually in a desired direction or orientation. In a past decade, functionally graded materials were remained in an interest of material investigators due to its prominent features, and have extensively used in almost every discipline of engineering which in turn significantly increases the number of research publication of FGM. In this paper the exact elasticity solution for an FGM circular shaft with piezo layers is analysed. piezoelectric layers are homogeneous and the modulus of elasticity for FGM varies continuously with the form of an exponential function. The shear modulus of the non-homogeneous FGM shaft is a given function of the Prandtl’s stress function of considered circular shaft when its material is homogeneous. state equations are derived. The Prandtl’s stress function and electric displacement potential function satisfy all conditions. The shearing stresses, torsional rigidity, torsional function for FGM layer and shearing stresses, electric displacements, torsional rigidity, electrical torsional rigidity ,torsional and electrical potential functions for piezoelectric layers are obtained. Exact analytical solution for hollow circular cross-section presented. At the end some graphs and conclusions are given. پرونده مقاله -
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19 - Mathematical Study for the Rayleigh Wave Propagation in a Composite Structure with Piezoelectric Material
B Paswan P Singh Sanjeev A SahuThe undulated characteristics of the irregular boundaries in the layered structure with piezoelectric materials generate some prominent effects on wave propagation. On the other hand, initial stress in the layered structure also play an important role in velocity charac چکیده کاملThe undulated characteristics of the irregular boundaries in the layered structure with piezoelectric materials generate some prominent effects on wave propagation. On the other hand, initial stress in the layered structure also play an important role in velocity characterization of the surface seismic waves. In light of the above, this paper studies the Rayleigh-type wave propagation in a composite structure with piezoelectric materials. Mathematical expressions for the mechanical displacement and electric potential function are obtained for both the piezoelectric layer and elastic substrate with the aid of coupled electromechanical field equations. Frequency equations for the waves are derived for both electrically open and short cases. The effects of the corrugation parameters, initial stress, piezoelectric constant, dielectric constant and thickness of the piezoelectric layer on the phase velocity of Rayleigh-type wave are discussed graphically for both the electrically open and short cases. Numerical examples and discussions are made to exhibit the findings graphically. The validation of the problem is made with the classical result. پرونده مقاله -
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20 - Vibration and Stability Analysis of Composite Tube Conveying Fluid Flow Equipped with Piezoelectric Ring
M Nazarzadeh Ansarodi H Biglari M.R SavizIn this paper, dynamic behaviour of composite tube equipped with piezoelectric actuator ring and conveying fluid flow is studied. The effects of incompressible Newtonian internal fluid flow with constant velocity are considered. The stiffened composite shell with differ چکیده کاملIn this paper, dynamic behaviour of composite tube equipped with piezoelectric actuator ring and conveying fluid flow is studied. The effects of incompressible Newtonian internal fluid flow with constant velocity are considered. The stiffened composite shell with different boundary conditions is exposed to electro- mechanical loading. The governing equations of motion are obtained based on the classical shell theory and using Hamilton’s principle. Then, these equations are discretized by using differential quadrature (DQ) method in longitudinal direction and harmonic differential quadrature (HDQ) method in circumferential direction. Solving these equations results in eigenvalues and mode shapes of the smart pipe conveying fluid. After comparing results with those existing in the literature, the detailed parametric study is conducted, by concentrating on the effects of fluid flow properties, geometry, material and boundary conditions of composite pipe, temperature, and piezo-actuator ring (size and position) on the vibration behavior of the coupled system, as well as dimensionless critical fluid velocity. It is expected that stability of the coupled system strongly depends on the imposed electric load. The present study can be applied for optimum design of sensors and actuators in active control systems, MEMS and biomechanical applications. پرونده مقاله -
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21 - Free Vibration of Functionally Graded Beams with Piezoelectric Layers Subjected to Axial Load
M Karami KhorramabadiThis paper studies free vibration of simply supported functionally graded beams with piezoelectric layers subjected to axial compressive loads. The Young's modulus of beam is assumed to be graded continuously across the beam thickness. Applying the Hamilton’s prin چکیده کاملThis paper studies free vibration of simply supported functionally graded beams with piezoelectric layers subjected to axial compressive loads. The Young's modulus of beam is assumed to be graded continuously across the beam thickness. Applying the Hamilton’s principle, the governing equation is established. Resulting equation is solved using the Euler’s Equation. The effects of the constituent volume fractions, the influences of applied voltage and axial compressive loads on the vibration frequency are presented. To investigate the accuracy of the present analysis, a compression study is carried out with a known data. پرونده مقاله -
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22 - Effect of Electric Potential Distribution on Electromechanical Behavior of a Piezoelectrically Sandwiched Micro-Beam
A Shah-Mohammadi-Azar G Rezazadeh R ShabaniThe paper deals with the mechanical behavior of a micro-beam bonded with two piezoelectric layers. The micro-beam is suspended over a fixed substrate and undergoes the both piezoelectric and electrostatic actuation. The piezoelectric layers are poled through the thickne چکیده کاملThe paper deals with the mechanical behavior of a micro-beam bonded with two piezoelectric layers. The micro-beam is suspended over a fixed substrate and undergoes the both piezoelectric and electrostatic actuation. The piezoelectric layers are poled through the thickness and equipped with surface electrodes. The equation governing the micro-beam deflection under electrostatic pressure is derived according to Euler-Bernoulli beam theory and considering the voltage applied to the piezoelectric layers and Maxwell’s equations for the two dimensional electric potential distribution. The obtained nonlinear equation solved by step by step linearization method and Galerkin weighted residual method. The effects of the electric potential distribution and the ratio of the piezoelectric layer thickness respect to the elastic layer thickness on the mechanical behavior of the micro-beam are investigated. The obtained results are compared with the results of a model in which electric potential distribution is not considered. پرونده مقاله -
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23 - Reflection From Free Surface of a Rotating Generalized Thermo-Piezoelectric Solid Half Space
Baljeet Singh B SinghThe analysis of rotational effect on the characteristics of plane waves propagating in a half space of generalized thermo-piezoelectric medium is presented in context of linear theory of thermo-piezoelectricity including Coriolis and centrifugal forces. The governing eq چکیده کاملThe analysis of rotational effect on the characteristics of plane waves propagating in a half space of generalized thermo-piezoelectric medium is presented in context of linear theory of thermo-piezoelectricity including Coriolis and centrifugal forces. The governing equations for a rotating generalized thermo-piezoelectric medium are formulated and solved for plane wave solutions to show the propagation of three quasi plane waves in the medium. A problem on the reflection of these plane waves is considered from a thermally insulated/isothermal boundary of a rotating generalized thermo-piezoelectric solid half space. The expressions for reflection coefficients of three reflected waves are obtained in explicit from. For experimental data of LiNbO3 and BaTiO3, the speeds of various plane waves are computed. The reflection coefficients of various reflected waves are also obtained numerically by using the data of BaTiO3. The dependence of speeds of plane waves and reflection coefficients of various reflected waves is shown graphically on the rotation parameter at each angle of incidence. پرونده مقاله -
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24 - Improving Power Density of Piezoelectric Vibration-Based Energy Scavengers
R Hosseini O Zargar M HamediVibration energy harvesting with piezoelectric materials currently generate up to 300 microwatts per cm2, using it to be mooted as an appropriate method of energy harvesting for powering low-power electronics. One of the important problems in bimorph piezoelectric energ چکیده کاملVibration energy harvesting with piezoelectric materials currently generate up to 300 microwatts per cm2, using it to be mooted as an appropriate method of energy harvesting for powering low-power electronics. One of the important problems in bimorph piezoelectric energy harvesting is the generation of the highest power with the lowest weight. In this paper the effect of the shape and geometry of a bimorph piezoelectric cantilever beam harvester on the electromechanical efficiency of the system is studied. An analytic model has been presented using Rayleigh cantilever beam approximations for piezoelectric harvesters with tapered bimorph piezoelectric cantilever beam. In order to study the effect of a cantilever beam length and geometry on the generated voltage, finite element simulation has been performed using ABAQUS. Design optimization has been used to obtain the maximum output power and tapered beams are observed to lead to more uniform distribution of strain in the piezoelectric layer, thus increasing efficiency. پرونده مقاله -
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25 - Dynamic Stability of Functionally Graded Beams with Piezoelectric Layers Located on a Continuous Elastic Foundation
N Omidi M Karami Khorramabadi A NiknejadThis paper studies dynamic stability of functionally graded beams with piezoelectric layers subjected to periodic axial compressive load that is simply supported at both ends lies on a continuous elastic foundation. The Young’s modulus of beam is assumed to be gra چکیده کاملThis paper studies dynamic stability of functionally graded beams with piezoelectric layers subjected to periodic axial compressive load that is simply supported at both ends lies on a continuous elastic foundation. The Young’s modulus of beam is assumed to be graded continuously across the beam thickness. Applying the Hamilton’s principle, the governing dynamic equation is established. The effects of the constituent volume fractions, the influences of applied voltage, foundation coefficient and piezoelectric thickness on the unstable regions are presented. پرونده مقاله -
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26 - Inhomogeneity Material Effect on Electromechanical Stresses, Displacement and Electric Potential in FGM Piezoelectric Hollow Rotating Disk
A Ghorbanpour Arani H Khazaali M Rahnama M DadkhahIn this paper, a radially piezoelectric functionally graded rotating disk is investigated by the analytical solution. The variation of material properties is assumed to follow a power law along the radial direction of the disk. Two resulting fully coupled differential e چکیده کاملIn this paper, a radially piezoelectric functionally graded rotating disk is investigated by the analytical solution. The variation of material properties is assumed to follow a power law along the radial direction of the disk. Two resulting fully coupled differential equations in terms of the displacement and electric potential are solved directly. Numerical results for different profiles of inhomogeneity are also graphically displayed. پرونده مقاله -
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27 - Surface Stress Effect on the Nonlocal Biaxial Buckling and Bending Analysis of Polymeric Piezoelectric Nanoplate Reinforced by CNT Using Eshelby-Mori-Tanaka Approach
M Mohammadimehr B Rousta Navi A Ghorbanpour AraniIn this article, the nonlocal biaxial buckling load and bending analysis of polymeric piezoelectric nanoplate reinforced by carbon nanotube (CNT) considering the surface stress effect is presented. This plate is subjected to electro-magneto-mechanical loadings. Eshelby- چکیده کاملIn this article, the nonlocal biaxial buckling load and bending analysis of polymeric piezoelectric nanoplate reinforced by carbon nanotube (CNT) considering the surface stress effect is presented. This plate is subjected to electro-magneto-mechanical loadings. Eshelby-Mori-Tanaka approach is used for defining the piezoelectric nanoplate material properties. Navier’s type solution is employed to obtain the critical buckling load of polymeric piezoelectric nanoplate for classical plate theory (CPT) and first order shear deformation theory (FSDT). The influences of various parameters on the biaxial nonlocal critical buckling load with respect to the local critical buckling load ratio () of nanoplate are examined. Surface stress effects on the surface biaxial critical buckling load to the non-surface biaxial critical buckling load ratio () can not be neglected. Moreover, the effect of residual surface stress constant on is higher than the other surface stress parameters on it. increases by applying the external voltage and magnetic fields. The nonlocal deflection to local deflection of piezoelectric nanocomposite plate ratio () decreases with an increase in the nonlocal parameter for both theories. And for FSDT, decreases with an increase in residual stress constant and vice versa for CPT. پرونده مقاله -
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28 - Application of Piezoelectric and Functionally Graded Materials in Designing Electrostatically Actuated Micro Switches
A Hosseinzadeh M.T AhmadianIn this research, a functionally graded microbeam bonded with piezoelectric layers is analyzed under electric force. Static and dynamic instability due to the electric actuation is studied because of its importance in micro electro mechanical systems, especially in micr چکیده کاملIn this research, a functionally graded microbeam bonded with piezoelectric layers is analyzed under electric force. Static and dynamic instability due to the electric actuation is studied because of its importance in micro electro mechanical systems, especially in micro switches. In order to prevent pull-in instability, two piezoelectric layers are used as sensor and actuator. A current amplifier is used to supply input voltage of the actuator from the output of the sensor layer. Using Hamilton’s principle and Euler-Bernoulli theory, equation of motion of the system is obtained. It is shown that the load type (distributed or concentrated) applied to the micro beam from the piezoelectric layer, depends on the shape of the actuator layer (E.g. rectangle, triangular). Finite element method is implemented for evaluation of displacement field in the micro beam and dynamic response of the micro beam under electric force is calculated using finite difference method. Effect of squeeze film damping on pull-in voltage and time-response of the system is considered using nonlinear Reynolds equation. Effect of several parameters such as gain value between piezoelectric sensor and actuator layer, profile of functionally material, and geometry of the system is considered on dynamic behavior of the micro beam especially on pull-in instability. Results are verified for simple cases with previous related studies in the literature and good agreements were achieved. Results indicate that increasing gain value between sensor and actuator enhances stiffness of the system and will raise pull-in voltage. Also, dependency of dynamic properties of the system such as amplitude and frequency of vibration on functionally graded material profile is shown. The material distribution of the functionally graded material is designed in such a way that results in a specific pull-in voltage. پرونده مقاله -
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29 - In-plane Band Gaps in a Periodic Plate with Piezoelectric Patches
H.J Xiang Z.B Cheng Z.F Shi X.Y YuA plate periodically bonded with piezoelectric patches on its surfaces is considered. The differential quadrature element method is used to solve the wave motion equation for the two-dimensional periodic structure. The method is very simple and easy to implement. Based چکیده کاملA plate periodically bonded with piezoelectric patches on its surfaces is considered. The differential quadrature element method is used to solve the wave motion equation for the two-dimensional periodic structure. The method is very simple and easy to implement. Based on the method, band structures for in-plane wave propagating in the periodic piezoelectric plate are studied, from which the frequency band gap is then obtained. Parametric studies are also performed to highlight geometrical and physical parameters on the band gaps. It is found that the thickness of the piezoelectric patches have no effect on the upper bound frequency of the band gap. Physical mechanism is explained for the phenomena. Dynamic simulations are finally conducted to show how the band gap works for a finite quasi-periodic plate. Numerical results show that the vibration in periodic plates can be dramatically attenuated when the exciting frequency falls into the band gap. پرونده مقاله -
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30 - Buckling Analysis of FG Plate with Smart Sensor/Actuator
N.S Viliani S.M.R Khalili H PorrostamiIn this paper, the active buckling control of smart functionally graded (FG) plates using piezoelectric sensor/actuator patches is studied. A simply supported FG rectangular plate which is bonded with piezoelectric rectangular patches on the top and/or the bottom surfac چکیده کاملIn this paper, the active buckling control of smart functionally graded (FG) plates using piezoelectric sensor/actuator patches is studied. A simply supported FG rectangular plate which is bonded with piezoelectric rectangular patches on the top and/or the bottom surface(s) as actuators/sensors is considered. When a constant electric charge is imposed, the governing differential equations of motion are derived using the classical laminated plate theory (CLPT). The solution for the equation of motion is obtained using a Fourier series method and the effect of feedback gain on the critical buckling load for PZT-4 is studied .The buckling behavior of smart plate subjected to compressive load is also investigated. The sensor output is used to determine the input to the actuator using the feedback control algorithm. The forces induced by the piezoelectric actuators under the applied voltage field, enhance the critical buckling load پرونده مقاله -
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31 - Wave Propagation Analysis of CNT Reinforced Composite Micro-Tube Conveying Viscose Fluid in Visco-Pasternak Foundation Under 2D Multi-Physical Fields
A. H Ghorbanpour Arani M.M Aghdam M.J SaeedianIn this research, wave propagation analysis in polymeric smart nanocomposite micro-tubes reinforced by single-walled carbon nanotubes (SWCNT) conveying fluid is studied. The surrounded elastic medium is simulated by visco-Pasternak model while the composite micro-tube u چکیده کاملIn this research, wave propagation analysis in polymeric smart nanocomposite micro-tubes reinforced by single-walled carbon nanotubes (SWCNT) conveying fluid is studied. The surrounded elastic medium is simulated by visco-Pasternak model while the composite micro-tube undergoes electro-magneto-mechanical fields. By means of micromechanics method, the constitutive structural coefficients of nanocomposite are obtained. The fluid flow is assumed to be incompressible, viscous and irrotational and the dynamic modelling of fluid flow and fluid viscosity are calculated using Navier-Stokes equation. Micro-tube is simulated by Euler-Bernoulli and Timoshenko beam models. Based on energy method and the Hamilton’s principle, the equation of motion are derived and modified couple stress theory is utilized to consider the small scale effect. Results indicate the influences of various parameters such as the small scale, elastic medium, 2D magnetic field, velocity and viscosity of fluid and volume fraction of carbon nanotube (CNT). The result of this study can be useful in micro structure and construction industries. پرونده مقاله -
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32 - Dynamics Analysis of the Steady and Transient States of a Nonlinear Piezoelectric Beam by a Finite Element Method
M Jabbari M Ghayour H.R MirdamadiThis paper presents a finite element formulation for the dynamics analysis of the steady and transient states of a nonlinear piezoelectric beam. A piezoelectric beam with damping is studied under harmonic excitation. A numerical method is used for this analysis. In the چکیده کاملThis paper presents a finite element formulation for the dynamics analysis of the steady and transient states of a nonlinear piezoelectric beam. A piezoelectric beam with damping is studied under harmonic excitation. A numerical method is used for this analysis. In the paper, the central difference formula of four order is used and compared with the central difference formula of two order in the time response of the structure. The NPBDA program is developed with Matlab software. In this program, the Newmark technique for dynamic analysis is used, the Newton-Raphson iterative and Simpson methods are used for the nonlinear solution. To verify the NPBDA results, the experimental results of Malatkar are used for the nonlinear vibration analysis of a beam without piezoelectric properties. Then, the piezoelectric effect on the frequency mode values and the time response are obtained. Afterwards, the modulation frequency in the nonlinear beam and the piezoelectric effect in this parameter are verified. پرونده مقاله -
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33 - Stress Waves in a Generalized Thermo Elastic Polygonal Plate of Inner and Outer Cross Sections
R SelvamaniThe stress wave propagation in a generalized thermoelastic polygonal plate of inner and outer cross sections is studied using the Fourier expansion collocation method. The wave equation of motion based on two-dimensional theory of elasticity is applied under the plane s چکیده کاملThe stress wave propagation in a generalized thermoelastic polygonal plate of inner and outer cross sections is studied using the Fourier expansion collocation method. The wave equation of motion based on two-dimensional theory of elasticity is applied under the plane strain assumption of generalized thermoelastic plate of polygonal shape, composed of homogeneous isotropic material. The frequency equations are obtained by satisfying the irregular boundary conditions along the inner and outer surface of the polygonal plate. The computed non-dimensional wave number and wave velocity of triangular, square, pentagonal and hexagonal plates are given by dispersion curves for longitudinal and flexural antisymmetric modes of vibrations. The roots of the frequency equation are obtained by using the secant method, applicable for complex roots. پرونده مقاله -
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34 - Temperature Effects on Nonlinear Vibration of FGM Plates Coupled with Piezoelectric Actuators
F Ebrahimi A RastgooAn analytical solution for a sandwich circular FGM plate coupled with piezoelectric layers under one-dimension heat conduction is presented in this paper. A nonlinear static problem is solved first to determine the initial stress state and pre-vibration deformations. By چکیده کاملAn analytical solution for a sandwich circular FGM plate coupled with piezoelectric layers under one-dimension heat conduction is presented in this paper. A nonlinear static problem is solved first to determine the initial stress state and pre-vibration deformations. By adding an incremental dynamic state to the pre-vibration state, the differential equations are derived. The role of thermal environment and control effects on nonlinear static deflections and natural frequencies imposed by the piezoelectric actuators using high input voltages are investigated. The good agreement between the results of this paper and those of the finite element (FE) analyses validated the presented approach. The emphasis is placed on investigating the effect of varying the applied actuator voltage and thermal environment as well as gradient index of FG plate on the dynamics and control characteristics of the structure. پرونده مقاله -
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35 - The Effect of Modified Couple Stress Theory on Buckling and Vibration Analysis of Functionally Graded Double-Layer Boron Nitride Piezoelectric Plate Based on CPT
M Mohammadimehr M MohandesIn this article, the effect of size-dependent on the buckling and vibration analysis of functionally graded (FG) double-layer boron nitride plate based on classical plate theory (CPT) under electro-thermo-mechanical loadings which is surrounded by elastic foundation is چکیده کاملIn this article, the effect of size-dependent on the buckling and vibration analysis of functionally graded (FG) double-layer boron nitride plate based on classical plate theory (CPT) under electro-thermo-mechanical loadings which is surrounded by elastic foundation is examined. This subject is developed using modified couple stress theory. Using Hamilton's principle, the governing equations of motion are obtained by applying a modified couple stress and von Karman nonlinear strain for piezoelectric material and Kirchhoff plate. These equations are coupled for the FG double-layer plate using Pasternak foundation and solved using Navier’s type solution. Then, the dimensionless natural frequencies and critical buckling load for simply supported boundary condition are obtained. Also, the effects of material length scale parameter, elastic foundation coefficients and power law index on the dimensionless natural frequency and critical buckling load are investigated. The results demonstrate that the dimensionless natural frequency of the piezoelectric plate increases steadily by growing the power law index. Also, the effect of the power law index on the dimensionless critical buckling load of double layer boron nitride piezoelectric for higher dimensionless material length scale parameter is the most. پرونده مقاله -
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36 - Buckling of Piezoelectric Composite Cylindrical Shell Under Electro-thermo-mechanical Loading
A Ghorbanpour Arani S Shams S Amir M.J MaboudiUsing principle of minimum total potential energy approach in conjunction with Rayleigh-Ritz method, the electro-thermo-mechanical axial buckling behavior of piezoelectric polymeric cylindrical shell reinforced with double-walled boron-nitride nanotube (DWBNNT) is inves چکیده کاملUsing principle of minimum total potential energy approach in conjunction with Rayleigh-Ritz method, the electro-thermo-mechanical axial buckling behavior of piezoelectric polymeric cylindrical shell reinforced with double-walled boron-nitride nanotube (DWBNNT) is investigated. Coupling between electrical and mechanical fields are considered according to a representative volume element (RVE)-based micromechanical model. This study indicates how buckling resistance of composite cylindrical shell may vary by applying thermal and electrical loads. Applying the reverse voltage or decreasing the temperature, also, increases the critical axial buckling load. This work showed that the piezoelectric BNNT generally enhances the buckling resistance of the composite cylindrical shell. پرونده مقاله -
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37 - Asymmetric Thermal Stresses of Hollow FGM Cylinders with Piezoelectric Internal and External Layers
M Jabbari M.B AghdamIn this paper ,the general solution of steady-state one dimensional asymmetric thermal stresses and electrical and mechanical displacements of a hollow cylinder made of functionally graded material and piezoelectric layers is developed .The material properties ,except t چکیده کاملIn this paper ,the general solution of steady-state one dimensional asymmetric thermal stresses and electrical and mechanical displacements of a hollow cylinder made of functionally graded material and piezoelectric layers is developed .The material properties ,except the Poisson's ration, are assumed to depend on the variable radius and they are expressed as power functions of radius. The temperature distribution is assumed to be a function of radius with general thermal and mechanical boundary conditions on the inside and outside surfaces. By using the separation of variables method and complex Fourier series, the Navier equations in term of displacements are derived and solved. پرونده مقاله -
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38 - Theoretical Formulations for Finite Element Models of Functionally Graded Beams with Piezoelectric Layers
J.N Reddy S Doshi A MulianaIn this paper an overview of functionally graded materials and constitutive relations of electro elasticity for three-dimensional deformable solids is presented, and governing equations of the Bernoulli–Euler and Timoshenko beam theories which account for through- چکیده کاملIn this paper an overview of functionally graded materials and constitutive relations of electro elasticity for three-dimensional deformable solids is presented, and governing equations of the Bernoulli–Euler and Timoshenko beam theories which account for through-thickness power-law variation of a two-constituent material and piezoelectric layers are developed using the principle of virtual displacements. The formulation is based on a power-law variation of the material in the core with piezoelectric layers at the top and bottom. Virtual work statements of the two theories are also developed and their finite element models are presented. The theoretical formulations and finite element models presented herein can be used in the analysis of piezolaminated and adaptive structures such as beams and plates. پرونده مقاله -
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39 - Analytical Solution for Response of Piezoelectric Cylinder Under Electro-Thermo-Mechanical Fields
S Golabi J Jafari FesharakiThis paper presents an analytical solution for response of a piezoelectric hollow cylinder under two-dimensional electro thermo mechanical fields. The solution is based on a direct method and the Navier equations were solved using the complex Fourier series. The advanta چکیده کاملThis paper presents an analytical solution for response of a piezoelectric hollow cylinder under two-dimensional electro thermo mechanical fields. The solution is based on a direct method and the Navier equations were solved using the complex Fourier series. The advantage of this method is its generality and from mathematical point of view, any type of the thermo mechanical and electrical boundary conditions can be considered without any restrictions. The thermo mechanical and electrical displacements are assumed that vary in radial and circumferential directions. Finally, three examples were considered to confirm the results and investigate the effect of in-phase and opposite-phase electro thermo mechanical boundary loads on two-dimensional electro thermo mechanical behavior of piezoelectric hollow cylinder. The results are compared with the previous work and FEM analysis. The main result of this study is that, by applying a proper distribution of thermal, electrical and mechanical fields, the distributions of electric and mechanical displacement, thermal and mechanical stresses can be controlled. پرونده مقاله -
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40 - Electro-Mechanical Buckling of a Piezoelectric Annular Plate Reinforced with BNNTs Under Thermal Environment
A Ghorbanpour Arani E HaghparastIn this article, axisymmetric buckling behavior of piezoelectric fiber reinforced polymeric composite (PFRPC) annular plate subjected to electro-thermo-mechanical field is presented utilizing principle of minimum potential energy. Boron-nitride nanotubes (BNNTs) are use چکیده کاملIn this article, axisymmetric buckling behavior of piezoelectric fiber reinforced polymeric composite (PFRPC) annular plate subjected to electro-thermo-mechanical field is presented utilizing principle of minimum potential energy. Boron-nitride nanotubes (BNNTs) are used as fibers. Full coupling between electrical, mechanical and thermal fields are considered according to a representative volume element (RVE)-based XY piezoelectric fiber reinforce composite (PEFRC) model. Assuming PFRPC material and its composite constituents to be linear, homogenous, orthotropic, and perfectly bonded with uniform applied field, the basic relation for the axisymmetric buckling of a circular plate subjected to radial compression, radial electrical field, and uniform temperature change are derived. The presented results show that BNNTs can be used as an effective supplement to improve mechanical behavior of polyvinylidene fluoride (PVDF). Also, at normal working conditions, the influence of thermal and mechanical fields is much higher than the electric one on the critical load; hence, this smart structure is best suited for applications as sensors than actuators. پرونده مقاله -
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41 - Two-dimensional Axisymmetric Electromechanical Response of Piezoelectric, Functionally Graded and Layered Composite Cylinders
T Kant P DesaiA mixed semi-analytical cum numerical approach is presented in this paper which accounts for the coupled mechanical and electrical response of piezoelectric, functionally graded (FG) and layered composite hollow circular cylinders of finite length. Under axisymmetric me چکیده کاملA mixed semi-analytical cum numerical approach is presented in this paper which accounts for the coupled mechanical and electrical response of piezoelectric, functionally graded (FG) and layered composite hollow circular cylinders of finite length. Under axisymmetric mechanical and electrical loadings, the three-dimensional problem (3D) gets reduced to a two-dimensional (2D) plane strain problem of elasticity. The 2D problem is further simplified and reduced to a one-dimensional (1D) by assuming an analytical solution in longitudinal direction (z) in terms of Fourier series expansion which satisfies the simply (diaphragm) supported boundary conditions exactly at the two ends z = 0, l. Fundamental (basic) dependent variables are chosen in the radial direction (thickness coordinate) of the cylinder. The resulting mathematical model is cast in the form of first order simultaneous ordinary differential equations which are integrated through an effective numerical integration technique by first transforming the BVP into a set of initial value problems (IVPs). The cylinder is subjected to internal/external pressurized mechanical and an electrical loading. Finally, numerical results are obtained which govern the active and sensory response of piezoelectric and FG cylinders. Numerical results are compared for their accuracy with available results. New results of finite length cylinders are generated and presented for future reference. پرونده مقاله -
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42 - Reflection of Plane Wave at Traction-Free Surface of a Pre-Stressed Functionally Graded Piezoelectric Material (FGPM) Half-Space
P.K Saroj S.A SahuThis paper is devoted to study a problem of plane waves reflection at a traction-free surface of a pre-stressed functionally graded piezoelectric material (FGPM). The effects of initial stress and material gradient on the reflection of plane waves are studied in this pa چکیده کاملThis paper is devoted to study a problem of plane waves reflection at a traction-free surface of a pre-stressed functionally graded piezoelectric material (FGPM). The effects of initial stress and material gradient on the reflection of plane waves are studied in this paper. Secular equation has been derived analytically for the pre-stressed FGPM half-space and used to show the existence of two coupled waves namely and Continuity condition of stress, electrical potential and electrical displacement at traction free surface is used to obtain the reflection coefficient of and waves. Results of the problem are shown graphically and effects of initial stress and material gradient are discussed for a particular case of Lithium niobate material. پرونده مقاله -
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43 - An Investigation into Resonant Frequency of Triangular V-Shaped Cantilever Piezoelectric Vibration Energy Harvester
R Hosseini M HamediPower supply is a bottle-neck problem of wireless micro-sensors, especially where the replacement of batteries is impossible or inconvenient. Now piezoelectric material is being used to harvest vibration energy for self-powered sensors. However, the geometry of a piezoe چکیده کاملPower supply is a bottle-neck problem of wireless micro-sensors, especially where the replacement of batteries is impossible or inconvenient. Now piezoelectric material is being used to harvest vibration energy for self-powered sensors. However, the geometry of a piezoelectric cantilever beam will greatly affect its vibration energy harvesting ability. This paper deduces a remarkably precise analytical formula for calculating the fundamental resonant frequency of V-shaped cantilevers using Rayleigh-Ritz method. This analytical formula, which is very convenient for mechanical energy harvester design based on Piezoelectric effect, is then validated by ABAQUS simulation. This formula raises a new perspective that, among all the V-shaped cantilevers and in comparison with rectangular one, the simplest tapered cantilever can lead to maximum resonant frequency and highest sensitivity. پرونده مقاله -
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44 - Nonlocal Piezomagnetoelasticity Theory for Buckling Analysis of Piezoelectric/Magnetostrictive Nanobeams Including Surface Effects
A Ghorbanpour Arani M Abdollahian A.H RahmatiThis paper presents the surface piezomagnetoelasticity theory for size-dependent buckling analysis of an embedded piezoelectric/magnetostrictive nanobeam (PMNB). It is assumed that the subjected forces from the surrounding medium contain both normal and shear components چکیده کاملThis paper presents the surface piezomagnetoelasticity theory for size-dependent buckling analysis of an embedded piezoelectric/magnetostrictive nanobeam (PMNB). It is assumed that the subjected forces from the surrounding medium contain both normal and shear components. Therefore, the surrounded elastic foundation is modeled by Pasternak foundation. The nonlocal piezomagnetoelasticity theory is applied so as to consider the small scale effects. Based on Timoshenko beam (TB) theory and using energy method and Hamilton’s principle the motion equations are obtained. By employing an analytical method, the critical magnetic, electrical and mechanical buckling loads of the nanobeam are yielded. Results are presented graphically to show the influences of small scale parameter, surrounding elastic medium, surface layers, and external electric and magnetic potentials on the buckling behaviors of PMNBs. Results delineate the significance of surface layers and external electric and magnetic potentials on the critical buckling loads of PMNBs. It is revealed that the critical magnetic, electrical and mechanical buckling loads decrease with increasing the small scale parameter. The results of this work is hoped to be of use in micro/nano electro mechanical systems (MEMS/NEMS) especially in designing and manufacturing electromagnetoelastic sensors and actuators. پرونده مقاله -
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45 - One-Dimensional Transient Thermal and Mechanical Stresses in FGM Hollow Cylinder with Piezoelectric Layers
S.M Mousavi M Jabbari M.A KianiIn this paper, an analytical method is developed to obtain the solution for the one dimensional transient thermal and mechanical stresses in a hollow cylinder made of functionally graded material (FGM) and piezoelectric layers. The FGM properties are assumed to depend o چکیده کاملIn this paper, an analytical method is developed to obtain the solution for the one dimensional transient thermal and mechanical stresses in a hollow cylinder made of functionally graded material (FGM) and piezoelectric layers. The FGM properties are assumed to depend on the variable r and they are expressed as power functions of r but the Poisson’s ratio is assumed to be constant. Transient temperature distribution, as a function of radial direction and time with general thermal boundary conditions on the inside and outside surfaces, is analytically obtained for different layers, using the method of separation of variables and generalized Bessel function. A direct method is used to solve the Navier equations, using the Euler equation and complex Fourier series. This method of solution does not have the limitations of the potential function or numerical methods as to handle more general types of the mechanical and thermal boundary conditions. پرونده مقاله -
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46 - Pull-In Instability of MSGT Piezoelectric Polymeric FG-SWCNTs Reinforced Nanocomposite Considering Surface Stress Effect
A Ghorbanpour Arani B Rousta Navi M Mohammadimehr S Niknejad A.A Ghorbanpour Arani A HosseinpourIn this paper, the pull-in instability of piezoelectric polymeric nanocomposite plates reinforced by functionally graded single-walled carbon nanotubes (FG-SWCNTs) based on modified strain gradient theory (MSGT) is investigated. Various types of SWCNTs are distributed i چکیده کاملIn this paper, the pull-in instability of piezoelectric polymeric nanocomposite plates reinforced by functionally graded single-walled carbon nanotubes (FG-SWCNTs) based on modified strain gradient theory (MSGT) is investigated. Various types of SWCNTs are distributed in piezoelectric polymeric plate and also surface stress effect is considered in this research. The piezoelectric polymeric nanocomposite plate is subjected to electro-magneto-mechanical loadings. The nonlinear governing equations are derived from Hamilton's principle. Then, pull-in voltage and natural frequency of the piezoelectric polymeric nanocomposite plates are calculated by Newton-Raphson method. There is a good agreement between the obtained and other researcher results. The results show that the pull-in voltage and natural frequency increase with increasing of applied voltage, magnetic field, FG-SWCNTs orientation angle and small scale parameters and decrease with increasing of van der Waals and Casimir forces, residual surface stress constant. Furthermore, highest and lowest pull-in voltages are belonging to FG-X and FG-O distribution types of SWCNTs. پرونده مقاله -
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47 - Investigating the Effect of Stiffness/Thickness Ratio on the Optimal Location of Piezoelectric Actuators Through PSO Algorithm
S Jafari Fesharaki S.Gh Madani S GolabiThis article has studied the effect of ratio of stiffness and thickness between piezoelectric actuators and host plat has been explored on optimal pattern for placement of piezoelectric work pieces around a hole in thin isotropic plate under static loading to reduce str چکیده کاملThis article has studied the effect of ratio of stiffness and thickness between piezoelectric actuators and host plat has been explored on optimal pattern for placement of piezoelectric work pieces around a hole in thin isotropic plate under static loading to reduce stress concentration. The piezoelectric actuators reduce directly or indirectly the stress concentration by applying positive and negative strains on the host plate. For this purpose, various modes as the thickness/stiffness ratios of the plate to the piezoelectric patches as ≥1 or ≤1 were considered. Then, a Python code was developed using particle swarm optimization algorithm in order to achieve the best model of piezoelectric actuators around the hole for maximum reduction in stress concentration factor. Also, the maximum stress concentration on the top and bottom of the hole was moved to another point around the edge by changing the location of piezoelectric patches. The results obtained from software solutions were confirmed by experimental tests. پرونده مقاله -
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48 - ارزیابی تاثیر ثوابت ناهمگنی مواد بر ضرایب شدت تنش در ورق پیزوالتریک مدرج تابعی با استفاده از روش بدون المان پتروف گالرکین محلی(MLPG)
محمد معدل شهرام شهروئیدر این مقاله از روش بدون المان پتروف گالرکین محلی برای به دست آوردن ضریب شدت تنش در ورق پیزو الکتریک مدرج تابعی تحت بارگذاری کششی یکنواخـت استفاده شده است. جهت مدل سازی میدان جابجایی و تنش، اطراف نوک ترک از روش مشاهده پذیری و اضافه نمودن گره ها و غنی سازی توابع پایه به چکیده کاملدر این مقاله از روش بدون المان پتروف گالرکین محلی برای به دست آوردن ضریب شدت تنش در ورق پیزو الکتریک مدرج تابعی تحت بارگذاری کششی یکنواخـت استفاده شده است. جهت مدل سازی میدان جابجایی و تنش، اطراف نوک ترک از روش مشاهده پذیری و اضافه نمودن گره ها و غنی سازی توابع پایه به دلیل وجود تکینگی اطراف نوک بهره گرفته شده است. همچنین از مدل تابع نمایی برای بیان تغییرات خواص جنس ماده پیزوالکتریک استفاده گردید. سپس میدان های جابجایی و پتانسیل الکتریکی تولید شده در اثر بارگذاری مکانیکی و تنش ها به ازای ثوابت ناهمگنی جنس متفاوت ماده پیزوالکتریک مدرج تابعی در راستاهای متفاوت ورق تنش از روش بدون المان محاسبه و با نتایج حاصل از نرم افزار اجزا محدود کامسول مقایسه گردید. در نهایت ضرایب شدت تنش از روش بدون المان با نتایج از حل تحلیلی مقایسه گردید که انطباق قابل قبولی را نشان داده است. پرونده مقاله -
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49 - مقایسه عملکرد برداشت کننده انرژی مدل دو درجه آزادی در دو پیکربندی متفاومت با تحریک اتفاقی پایه
امیرحشمت خدمتی بازکیائیبمنظور تبدیل ارتعاشات مکانیکی به انرژی الکتریکی مفید از اهداف بسیاری از پژوهش‌ها در علم روز بوده و بدین منظور از تجهیزات برداشت‌کننده با اجزای پیزوالکتریک استفاده شده است. برای بررسی عملکرد این سامانه، آگاهی از رفتار و خروجی سیستم ارتعاشی، تاثیر پارامترهای مختلف آن ساما چکیده کاملبمنظور تبدیل ارتعاشات مکانیکی به انرژی الکتریکی مفید از اهداف بسیاری از پژوهش‌ها در علم روز بوده و بدین منظور از تجهیزات برداشت‌کننده با اجزای پیزوالکتریک استفاده شده است. برای بررسی عملکرد این سامانه، آگاهی از رفتار و خروجی سیستم ارتعاشی، تاثیر پارامترهای مختلف آن سامانه از اهمیت بالایی برخوردار است. در پژوهش حاضر سعی برآن است که با مدلسازی سامانه ارتعاشی بصورت مدل دو درجه آزادی، در دو پیکربندی مختلف، تاثیرات پارامترهای مختلف بر عملکرد برداشت‌کننده مورد بررسی قرار گیرد. برای بررسی دقیقتر و یافتن نتیجه نزدیکتر به واقعیت، با استفاده از تئوری ارتعاشات اتفاقی خطی، تحریک مورد در بحث، از نوع نویز سفید بوده است. در مدلسازی ریاضی، دو حالت دو درجه آزادی مورد بررسی قرارگرفته شده که در حالت اول، پیزوالکتریک بین پایه و جرم اول و در حالت دوم پیزوالکتریک بین پایه و جرم دوم مفروض بوده است. پس از استخراج معادلات حاکم در هر پیکربندی و اعمال ورودی به سیستم با تحریک اتفاقی، تاثیر تمامی پارامترهای شناسایی و معرفی شده در سامانه مورد مطالعه قرار گرفته، پیکربندی با کارآیی بالاتر، برحسب میانگین برداشت کننده انرژی، معرفی و نتایج به صورت ترسیمی بیان شده است. پرونده مقاله -
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50 - Investigating Output Voltage and Mechanical Stability of a Piezoelectric Nanogenerator Based on ZnO Nanowire
S. Fathi T. Fanaei SheikholeslamiThe output of a piezoelectric nanogenerator based on ZnO nanowire is largely affected by the shape of nanowire. In order to obtain mechanically stable nanogenerator with high performance, the investigation of mechanical and electrical characteristics related to the nano چکیده کاملThe output of a piezoelectric nanogenerator based on ZnO nanowire is largely affected by the shape of nanowire. In order to obtain mechanically stable nanogenerator with high performance, the investigation of mechanical and electrical characteristics related to the nanowires and materials used in nanogenerators are of great interest and significance. This paper presents the various behavior of the conduction band, carrier concentration and the magnitude and distribution of the piezoelectric potential in cylindrical and conical shape ZnO nanowire (NW) by using finite element (FE) method. It is shown that symmetry reduction in nanowire shape and replacement the cylindrical NW with the conical NW, results in more advantageous both in terms of mechanical stability and piezoelectric potential. The large variation of the conduction band at the tip of conical nanowire results in receiving a large increase of maximum piezoelectric potential from -70 mv (cylindrical nanowire with radius of 30 nm) to -1750 mv (conical nanowire with tip radius of 5 nm and base radius of 30 nm). It is also shown that the insulating materials with lower Young’s modulus and lower relative permittivity are the best options in nanogenerator device fabrication. This numerical study can provide a guideline to design of the piezoelectric nanogenerator with high performance. پرونده مقاله -
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51 - مکان یابی بهینه المانهای پیزوالکتریک برای میرانمودن ارتعاشات سازهها
مجتبی حسنلو احمد باقری فرید نجفیکاهش مصرف انرژی بعنوان هدف اساسی در طراحی محسوب میشود. بالطبع هدر رفت انرژی در هر سیستمی میتواند آینده یک سیستم را به مخاطره بیندازد. این موضوع چند دهه ای است که توجه فراوانی از سوی پژوهشگران سراسر دنیا قرارگرفته است. سیستم های پیوسته همانند یک سازه مهندسی از قبیل تیر چکیده کاملکاهش مصرف انرژی بعنوان هدف اساسی در طراحی محسوب میشود. بالطبع هدر رفت انرژی در هر سیستمی میتواند آینده یک سیستم را به مخاطره بیندازد. این موضوع چند دهه ای است که توجه فراوانی از سوی پژوهشگران سراسر دنیا قرارگرفته است. سیستم های پیوسته همانند یک سازه مهندسی از قبیل تیر – ورق- پوسته کاربرد وسیعی در صنایع مختلف دارد و بخش عمده سیستم‌های صنعتی دربرگیرنده این نوع سازهها هستند اما مهمترین نکته در طراحی این نوع سیستم‌ها جلوگیری از خرابی، کاهش هزینه‌های تعمیرات و نگهداری و افزایش عمر و سلامت سیستم میباشد و این نکات مذکور بطور مستقیم و غیرمستقیم توصیف کننده مصرف انرژی میباشند و می‌توانند به نوعی اهداف طراحی را ارضا نسازند و به یک محصول و خروجی مطلوب دست نیابند. ارتعاش هر نوع سیستم پیوسته ای میتواند نتیجه نامطلوبی در عملکرد سیستم بجای گذارد و طراحی یک سیستم را تضعیف سازد بنابراین تلاش برای کاهش ارتعاش و کنترل این پدیده دینامیکی تاثیر بسزایی در کاهش اتلاف انرژی ( انرژی جنبشی – انرژی پتانسیل) یک سازه پیوسته خواهد گذاشت. در این گزارش قرار است مجموعه فعالیتهای علمی و پژوهشی که از سال 1980 تا 2013 در زمینه کاهش ارتعاشات سیستم های پیوسته با تمرکز بر رویکرد یافتن مکان بهینه بر روی سازه و نصب تکه های حسگر و عملگر پیزوالکتریک و ترکیب مدل هوشمند ساخته‌شده با انواع رویکردهای کنترلی جهت مهار و کنترل ارتعاشات ناخواسته سیستم در برابر تحریکات و اغتشاشات خارجی گزارش داده شود. پرونده مقاله -
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52 - تحلیل ارتعاشات و کنترل میکروتیر یکسر گیردار به همراه لایه های عملگر و حسگر پیزوالکتریک با فرض اثرات سطح
سید علی افتخاری محمد خواجه خباز محمد هاشمیانامروزه پیش‌بینی رفتار ارتعاشی و دینامیکی سازه‌های میکرو مورد توجه بسیاری از پژوهشگران قرار گرفته است. در این پژوهش تحلیل ارتعاشات و کنترل میکروتیر یکسر گیردار به همراه لایه‌های پیزوالکتریک عملگر و حسگر با فرض اثرات تنش سطح مورد ارزیابی قرار گرفته است. معادلات دیفرانسیل چکیده کاملامروزه پیش‌بینی رفتار ارتعاشی و دینامیکی سازه‌های میکرو مورد توجه بسیاری از پژوهشگران قرار گرفته است. در این پژوهش تحلیل ارتعاشات و کنترل میکروتیر یکسر گیردار به همراه لایه‌های پیزوالکتریک عملگر و حسگر با فرض اثرات تنش سطح مورد ارزیابی قرار گرفته است. معادلات دیفرانسیل حاکم با استفاده از روش انرژی و اصل همیلتون استخراج شده و از روش مجموع مربعات دیفرانسیلی تعمیم یافته برای گسسته-سازی و تبدیل معادلات دیفرانسیل پاره‌ای به دسته معادلات دیفرانسیل معمولی استفاده شده است. اثر تغییرات هندسه مدل و مدول الاستیسیته سطح، تنش پسماند سطح و چگالی سطحی بر فرکانس طبیعی مدل میکروتیر با لایه‌های پیزوالکتریک بررسی شده است. همچنین تأثیر طراحی کنترلر بهینه خطی بر تغییرات پاسخ دینامیکی و ولتاژ کنترلی پیزوالکتریک مورد ارزیابی قرار گرفته است. نتایج نشان دهنده‌ی افزایش سرعت پاسخ و کاهش سریعتر دامنه ارتعاشی مدل با طراحی کنترل بهینه خطی است. پرونده مقاله -
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53 - Finite element modeling of a pavement piezoelectric energy harvester
Ehsan Latifi Pakdehi Ali Akbar Pasha ZanoosiOne of the best methods to achieving renewable and clean energy is piezoelectric energy harvesters (PEHs), which convert mechanical and vibration energy into electrical energy. These generators appeared after the special and unique capabilities of piezoelectric and vibr چکیده کاملOne of the best methods to achieving renewable and clean energy is piezoelectric energy harvesters (PEHs), which convert mechanical and vibration energy into electrical energy. These generators appeared after the special and unique capabilities of piezoelectric and vibration to electrical energy can be directly converted. The use of these generators is seen in many fields including the use of roads and bridges to convert vibrations caused by the vehicles in to electrical energy and other thing. In this study a piezoelectric energy harvester with the feature of parallel piezoelectric connections was computer simulated using a finite element method. In a computer simulation unlike laboratory method that can only analyze one form of a system, different states and situations of factors can be simulated. In this study, to achieve an optimal state of power and output voltage of an existing PEH, the effects and behaviors of different parameters such as forces, frequencies, temperatures, housing dimensions, piezoelectric materials and the presence of isolators have been investigated. In addition, to obtain the significance of these factors, using the analysis of variance method, the importance and effectiveness of each of these parameters has been investigated. The results revealed that increasing the amount of force and frequency and decreasing the temperature increases the output voltage of this kind of PEH. Changing the dimensions of the housing if its area is constant, does not change the output result and the use of isolators reduces the output voltage. The effect of these parameters is compared to previous studies and the results are presented. پرونده مقاله -
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54 - Damage detection and structural health monitoring of ST-37 plate using smart materials and signal processing by artificial neural networks
Hamid Reza Mirdamadi Farshad Ghasemi Javad JafariStructural health monitoring (SHM) systems operate online and test different materials using ultrasonic guided waves and piezoelectric smart materials. These systems are permanently installed on the structures and display information on the monitor screen. The user info چکیده کاملStructural health monitoring (SHM) systems operate online and test different materials using ultrasonic guided waves and piezoelectric smart materials. These systems are permanently installed on the structures and display information on the monitor screen. The user informs the engineers of the existing damage after observing signal loss which appears after damage is caused. In this paper health monitoring is done for plate shaped structures made of ST-37 steel. After conducting the experimental tests, the stored signals by the multi-layer artificial neural network algorithm is processed and the damage caused in the plate is detected. By analyzing the graphs, it becomes clear that after causing damage the signal amplitude decreases. In the experimental test two piezoelectric discs are used on a steel plate which have been installed using a strong adhesive. Using a strong adhesive improves wave, propagation in the structure. Developing innovative testing methods for the SHM system has caused better control in structures after assembly. پرونده مقاله -
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55 - Design and Fabrication of a Longitudinal-Torsional Ultrasonic Transducer
Yahya Radi Najafabadi Reza Nosouhi Frahad SajajidA hybrid longitudinal-torsional ultrasonic transducer is designed and fabricated in this research. Thedesign of the transducer was performed using the FE method with ABAQUS software, with the aimof combining the longitudinal and torsional vibration modes. The transducer چکیده کاملA hybrid longitudinal-torsional ultrasonic transducer is designed and fabricated in this research. Thedesign of the transducer was performed using the FE method with ABAQUS software, with the aimof combining the longitudinal and torsional vibration modes. The transducer horn is then fabricatedusing a 4-axis milling machine. The PZT stacks are employed in order to excite the transducer. Thetransducer body is fabricated with grade 5 titanium for its appropriate mechanical properties. Thetransducer is then assembled and the experimental tests are carried out to measure the vibrationamplitude in both longitudinal and torsional directions using an Eddy current displacement sensor.Theresults showed that the resonance frequencies of both the torsional and longitudinal modes arethe same and experimental results are in good agreement with the FE results. The transducer can beused as a vibration tool for vibration assisted drilling which can produce both longitudinal andtorsional vibrations. پرونده مقاله -
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56 - بررسی تاثیر ضخامت و فشار در دیافراگم های میکرو الکترو مکانیکی در میزان جابجائی در کاربردهای پزشکی
نازلی زرگرپورفردیندر این مقاله، تاثیر پارامترهای طراحی در دیافراگم بر روی حساسیت میکروفن به منظور استفاده در کاربردهای پزشکی قابل کاشت ارائه گردیده است. پارامترهای متفاوتی از دیافراگم همچون شکل، ابعاد، ضخامت و فشارهای اعمالی مختلف بر روی دیافراگم در نظر گرفته شده‌است. تاثیر تغییرات در ای چکیده کاملدر این مقاله، تاثیر پارامترهای طراحی در دیافراگم بر روی حساسیت میکروفن به منظور استفاده در کاربردهای پزشکی قابل کاشت ارائه گردیده است. پارامترهای متفاوتی از دیافراگم همچون شکل، ابعاد، ضخامت و فشارهای اعمالی مختلف بر روی دیافراگم در نظر گرفته شده‌است. تاثیر تغییرات در این پارامترها بر روی میزان جابجائی و استرس در انواع شکل دیافراگم ها مورد بحث و بررسی واقع شده است. به منظور طراحی بهینه، انواع شکل دیافراگم های پیشنهادی، از جهت پارامترهای در نظر گرفته شده در نرم افزار COMSOL شبیه سازی و آنالیز شده اند. با توجه به پارامترهای مورد بررسی، انواع اشکال دیافراگم مربعی، مستطیلی و بیضوی شکل با توجه به شرایط در نظر گرفته شده، دارای میانگین جابجائی مرکزی در محدوده فرکانس شنوائی انسان 20Hz-20KHz به ترتیب nm2. 6 ، nm 5. 5 و nm 130می باشد. نتایج حاصل از شبیه سازی ها بدین صورت می باشد که دیافراگم بیضوی شکل نسبت به اشکال دیگر مورد بررسی در این مقاله، برای کاربردهای پزشکی و امکان کاشته شدن، دارای کارائی بهینه و مطلوبی می باشد. به علاوه، ماده ی پیزوالکتریک مورد استفاده در طراحی دیافراگم PZT است. پرونده مقاله -
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57 - Extraction of the governing equations for steady state and axisymmetric behavior of a porous piezoelectric circular solid plate
علی ابجدی محسن جباری احمد رضا خورشیدوندBased on the available evidence, porous piezoelectric materials have great potential for the development of smart (active) structures with high strength, high stiffness and light weight such as ceramics and composites. Among the ceramic materials with porous piezoelectr چکیده کاملBased on the available evidence, porous piezoelectric materials have great potential for the development of smart (active) structures with high strength, high stiffness and light weight such as ceramics and composites. Among the ceramic materials with porous piezoelectric compounds, can be mentioned Lead-zirconate-titanate (PZT), Lead-titanate (PbTiO2), Lead-zirconate (PbZrO3), Barium-titanate (BaTiO3), Cadmium-selenide (CdSe), etc. This study extracts the governing partial differential equations for steady- state and axisymmetric behavior of a circular solid plate is made of an undrained saturated porous piezoelectric hexagonal material symmetry of class 6 mm. The porosities of the plate vary through the thickness; thus, material properties, except poisson’s ratio, are assumed as exponential functions of axial variable z in cylindrical coordinates. Additionally, piezothermoelastic behavior of a circular plate subject to external thermal, mechanical and electrical loads is considered, so various concepts including three-dimensional linear elasticity theory and dielectric theory are used in combination to create a linear piezoelectric model. The extraordinary and special industrial properties of porous piezoelectric materials, their increasing use and the need to know the behavior of these materials, doubles the importance of this research. پرونده مقاله -
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58 - A Robust Controller Design for Piezoelectric Positioning Stage with Bouc-Wen Hysteresis Compensator
Abbas Rasaienia Mina Asnaashari Mona HemmatiIn this paper, an inverse compensator based on the Bouc-Wen model is used to reduce the effect of hysteresis on a piezoelectric micro-actuator. This compensator is used as an open loop controller which partially eliminates the system hysteresis effect. In the last step, چکیده کاملIn this paper, an inverse compensator based on the Bouc-Wen model is used to reduce the effect of hysteresis on a piezoelectric micro-actuator. This compensator is used as an open loop controller which partially eliminates the system hysteresis effect. In the last step, in order to increase the reliability of the system and to achieve the desired goals, a H∞ robust controller is proposed in the presence of a compensator, to detect in the presence of modeling error and compensator error. At the end, simulation results are provided by MATLAB to demonstrate the effectiveness of the proposed control scheme. These results indicate that the proposed scheme provides a robust system performance and the tracking error reaches zero with acceptable accuracy. پرونده مقاله -
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59 - مطالعه تاثیر افزودن بیسموت قبل و بعد از کلسیناسیون بر خواص الکتریکی پیزوسرامیک‌های (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3
راضیه حیاتی محمد علی بهره ورترکیب پیزوالکتریک عاری از سرب Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) با استفاده از روش متداول سرامیک‌ها سنتز و اثر افزودن 1/0% مولی Bi2O3 بر فرایند زینتر و خواص دی الکتریک، فروالکتریک و پیزوالکتریک این ترکیب مطالعه شد. در راستای کاهش اتلاف بیسموت در دماهای بالای کلسیناسیون و ز چکیده کاملترکیب پیزوالکتریک عاری از سرب Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) با استفاده از روش متداول سرامیک‌ها سنتز و اثر افزودن 1/0% مولی Bi2O3 بر فرایند زینتر و خواص دی الکتریک، فروالکتریک و پیزوالکتریک این ترکیب مطالعه شد. در راستای کاهش اتلاف بیسموت در دماهای بالای کلسیناسیون و زینتر BCZT، ، دو روش متفاوت برای افزودن بیسموت به ساختار این ترکیب بکار گرفته شد؛ در روش اول، Bi2O3 مطابق فرمولاسیون ([(Ba0.85,Ca0.15)1-xBi3x/2](Zr0.1,Ti0.9)O3 با جبران بار در مکان‌های A-ی ساختار با سایر مواد اولیه مخلوط گردید و در روش دوم، ابتدا ترکیب BCZT سنتز و سپس Bi2O3 بدون جبران بار با این ترکیب مخلوط شد و پس از شکل دهی، سرامیک‌های BCZT-Bi زینتر گردیدند. آنالیزهای فازی و ریزساختاری با استفاده از تکنیک پراش اشعه‌‌ی X (XRD) و میکروسکوپ الکترونی روبشی (SEM) انجام گردید. نمودارهای وابستگی دمایی و فرکانسی خواص دی الکتریک، بیانگر آن بود که با اضافه کردن 1/0% مولی Bi2O3 این سرامیک‌ها از رفتار طبیعی مواد فروالکتریک تبعیت می کنند. نتایج به دست آمده حاکی از آن بود که اضافه کردن بیسموت بعد از سنتز BCZT نسبت به روش دوم در افزایش چگالی و بهبود خواص الکتریکی موثرتر میباشد. در دمای زینتر °C1350 برای ترکیب BCZT-Bi0.1 ضرایب پیزوالکتریک مستقیم و معکوس، فاکتور جفت‌شدگی الکترومکانیکی و قطبش باقی مانده به ترتیب d33=325 pC/m، d33*=675 pm/V، kp=0.42 و Pr=10.4 µC/cm2 به دست آمد. پرونده مقاله -
دسترسی آزاد مقاله
60 - تحلیل و بررسی اثر افزودنی‌های مولیبدن و کبالت روی خواص ساختاری و الکتریکی ماده پیزوسرامیکPZT5
محمد هادی همتی حسین لکزیان محمد حسین قزل ایاغهدف از این تحقیق تحلیل و بررسی اثر افزودنی‌های مولیبدن و کبالت روی خواص دی‌الکتریک، فرو الکتریک و پیزوالکتریک ماده پیزوسرامیک Pb(Zr0.52Ti0.48)O3با افزودن مولیبدن و کبالت در محل زیرکونات و تیتانات در محدوده (2– 0 ) درصد میباشد. بدین منظور ابتدا پودرها با روش شیمیا چکیده کاملهدف از این تحقیق تحلیل و بررسی اثر افزودنی‌های مولیبدن و کبالت روی خواص دی‌الکتریک، فرو الکتریک و پیزوالکتریک ماده پیزوسرامیک Pb(Zr0.52Ti0.48)O3با افزودن مولیبدن و کبالت در محل زیرکونات و تیتانات در محدوده (2– 0 ) درصد میباشد. بدین منظور ابتدا پودرها با روش شیمیایی تر آماده شدند. سپس برای 2 ساعت در دمای 850 درجه سانتی گراد کلسینه شدند. خواص ساختاری ترکیبات با استفاده از روش پراش اشعه ایکس (XRD) برای تایید تشکیل ترکیبات تک فاز (با ساختار پروسکایت) در دمای اتاق موردبررسی قرار گرفت. تجزیه و تحلیل ریزساختاری سطح دیسک های پخته شده با میکروسکوپ الکترونی روبشی (SEM) نشان می‌دهد که تغییر قابل‌توجهی در اندازه دانه با افزایش مولیبدن و کبالت وجود دارد. مطالعات دقیق از خواص دی‌الکتریکPZTتغییر قابل توجه در ضریب شارژ پیزوالکتریک D33(تا 84 ℅ کاهش)، ضریب ارتباط الکترومکانیکی Keff(تا 78 ℅ کاهش)،فرکانس رزونانس Fr(تا 25 ℅ افزایش) و کیفیت مکانیکی Qm(تا 110 ℅ افزایش) را درنمونه های ساخته شده و مورد آزمون قرارگرفته نشان می‌دهد. پرونده مقاله -
دسترسی آزاد مقاله
61 - Deflection and Free Vibration of Sandwich Panel with Honeycomb Core on Winkler Elastic Foundation
یونس یوسفی حسین وحدانی فر رضا شیرانی محمد دهقانیIn this paper deflection and free vibration of sandwich panel is studied. The core of Sandwich panels is made of hexagonal honeycomb and faces are made of two different materials of Carbon Fiber Reinforced Plastic and K-aryl/epoxy covering. The governing equations are d چکیده کاملIn this paper deflection and free vibration of sandwich panel is studied. The core of Sandwich panels is made of hexagonal honeycomb and faces are made of two different materials of Carbon Fiber Reinforced Plastic and K-aryl/epoxy covering. The governing equations are deduced from the First order Sheer Deformation Theory (FSDT) and they are solved using Generalized Differential Quadrature Method (GDQM). The classical method in the references is used to verify the DQ method and to show that the applied GDQM method has a good results with compared to the references. Deflection of sandwich panel is investigated with two different load types. Finally natural frequency for the first 4 modes and the two different faces materials are calculated and the effect of various lengths to core thickness ratios and faces to honeycomb core thickness ratios are studied. Further, the effect of foundation stiffness coefficient on deflection and natural frequency are showed پرونده مقاله -
دسترسی آزاد مقاله
62 - Energy Harvesting Electrical from Nano Beam with Layer Piezoelectric under Random Vibration
حسین وحدانی فر رضا شیرانی محمد دهقانی یونس یوسفیIn the present paper, electrical energy harvesting from random vibrations of an Euler-Bernoulli nano-beam with two piezoelectric layers is investigated. The beam is composed of an aluminum layer together with two piezoelectric ceramic layers (PZT 5A) serving as energy h چکیده کاملIn the present paper, electrical energy harvesting from random vibrations of an Euler-Bernoulli nano-beam with two piezoelectric layers is investigated. The beam is composed of an aluminum layer together with two piezoelectric ceramic layers (PZT 5A) serving as energy harvesting sensors. In the proposed method, the equations governing the bimorph nano-beam will be analytically derived using classical beam theory with corresponding modification coefficients to the nano-structure applied. Then, the derived system of equations will be solved following Kantorovich method. Assumed boundary conditions for the nano-beam are as follows: a clamped end with the mass concentrated at the free end of the beam. Further, the input activation function of the system for energy harvesting was taken as being random. Since the objective of this research is to investigate the amount of harvested energy, the section on the results provides associated voltage and maximum output power curves with the bimorph nano-beam under random activation and input white noise, while also presenting the effects of characteristics and scale factor of the nano-particles on the amount of harvested energy. پرونده مقاله -
دسترسی آزاد مقاله
63 - A Pitch-Catch Based Online Structural Health Monitoring of Pressure Vessels, Considering Corrosion Formation
سیدحمیدرضا هاشمی حمیدرضا هوشیارمنش مجتبی قدسیStructural health monitoring is a developing research field which is multifunctional and can estimate the health condition of the structure by data analyzing and also can prognosticate the structural damages. Illuminating the damages by using piezoelectric sensors is on چکیده کاملStructural health monitoring is a developing research field which is multifunctional and can estimate the health condition of the structure by data analyzing and also can prognosticate the structural damages. Illuminating the damages by using piezoelectric sensors is one of the most effective techniques in structural health monitoring. Pressurized equipments are very important components in process industries such as oil, gas, petrochemical and power plants, that their health monitoring is vital. The aim of this research is to introduce a technique to illuminate the damages in these equipments by using guided waves. Thereby, two different specimens were used as pressurized vessels at different conditions: pristine and corroded. Different internal pressures were also studied. Piezoelectric transducers were electromechanically coupled to the vessels and the guided waves were propagated by using pitch-catch method. The outcomes indicated that damage parameters in vessels such as corrosion and pressure changes have considerable effect on the signals that piezoelectric sensors receive. Corrosion, the most common damage in pressurized vessels, reduce the signal domain in frequency field to 11%. Also increasing pressure reduce the signal domain.We can used these outcomes to innovate a technique for structural health monitoring of pressure equipmentss. پرونده مقاله -
دسترسی آزاد مقاله
64 - Free vibration Study of simply supported cylindrical laminateds panels with piezoelectric layer
مصطفی معطری فرزان براتیIn the present study, vibration of cylindrical laminates with different layers and angles were studied. In order to actuate and polarize in radial direction, a piezoelectric layer was located at outer surface of composite shell. Laminates were assumed long enough so tha چکیده کاملIn the present study, vibration of cylindrical laminates with different layers and angles were studied. In order to actuate and polarize in radial direction, a piezoelectric layer was located at outer surface of composite shell. Laminates were assumed long enough so that plane strain state analysis in 2D can be used properly. In order to satisfy the boundary conditions, variables in terms of Fourier series were obtained. The governing equations reduced to ordinary differential equations at thickness direction and by power series method, the exact solution equations were obtained, unknown coefficient were calculated with rapid convergence. By using the matrix transfer method, vibration response of composite shell were obtained. Finally, results for the first seven modes of natural frequency of multi layer cylindrical shell were obtained. In addition, for both state of one single piezoelectric layer and five layer shell at the end, variable response such as displacement, principal stress and strain were achieved. پرونده مقاله -
دسترسی آزاد مقاله
65 - Dynamic modeling and nonlinear vibration simulation of piezoelectric micro-beam in self sensing mode of atomic force microscope
احمد حقانی رضا قادریNowadays, atomic force microscope is considered as a useful tool in the determination of intermolecular forces and surface topography with the resolution of nanometers. In this kind of microscope, micro cantilever is considered as the heart of the microscope and is used چکیده کاملNowadays, atomic force microscope is considered as a useful tool in the determination of intermolecular forces and surface topography with the resolution of nanometers. In this kind of microscope, micro cantilever is considered as the heart of the microscope and is used as a measuring tool. This paper is aimed towards investigating the behavior of a piezoelectric micro cantilever with a triangular head, in self-measure mode and close proximity to the surface of a sample. Output charge from the piezoelectric layer and also the output current, in this mode, is considered as an effective factor in the measurement of the bending. The micro cantilever’s vibration behavior becomes nonlinear, as it approaches the surface of the sample. Surely the piezoelectric layer in the self-measure mode can be considered as a good measuring tool, only when it reflects the effects of the nonlinear interaction between the tip of the probe and the surface of the sample in its measurements. In order to investigate this matter, first the differential equations that are ruling over the vibrating movements of the piezoelectric micro cantilever with a triangular head, are transformed into normal nonlinear differential equations using the Galerkin method. Then the resulting nonlinear differential equation is solved using the multi-scale method. After solving the differential equation ruling over the problem, the micro cantilevers behavior in the proximity of the surface of the sample is simulated and the effect of factors such as balancing distance, oscillation modes and the substance of piezoelectric layer are investigated. پرونده مقاله -
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66 - Resolution composite shell with a layer of piezoelectric vibration analysis
اکبر علی بیگلو عبدالمجید کنیIn this paper, the vibration of composite cylindrical shell with piezoelectric layers in the interior and exterior surfaces is investigated. The composite shell without piezoelectric layers can be studied and compared the results with the results of other researchers, t چکیده کاملIn this paper, the vibration of composite cylindrical shell with piezoelectric layers in the interior and exterior surfaces is investigated. The composite shell without piezoelectric layers can be studied and compared the results with the results of other researchers, the cylindrical shell laminated with layers of piezoelectric vibration checked. The result is a three-dimensional elasticity equations relationships because they do not apply any approximate gain are quite analytical. Shells intended, is closed and has restricted the mainstays in the end it was simple, and the results for the ratio of the radius and the radius of the different thickness are obtained پرونده مقاله -
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67 - Static Deflection of Hinged-Hinged piezoelectric Multilayer Beam Under Different Loading Conditions
افشین منوچهری‌فر علیرضا جلیلیIn this paper at first introduced constituent equations for piezoelectric and then by the help of this equations, internal energy of hinged-hinged piezoelectric multilayer beam was computed. Then by the principle of minimum potential energy and Rayleigh -Ritz method the چکیده کاملIn this paper at first introduced constituent equations for piezoelectric and then by the help of this equations, internal energy of hinged-hinged piezoelectric multilayer beam was computed. Then by the principle of minimum potential energy and Rayleigh -Ritz method the bending curvature equation of hinged-hinged piezoelectric multilayer beam under concentrated moment, concentrated force, uniform pressure load and applied electrical voltage with satisfaction of boundary conditions are guessed. Unknown coefficients are determined by the principle of minimum potential energy. Thereinafter obtained equations have simplified for hinged-hinged unimorph and bimorph beam. Electrical load and voltage produced in unimorph and bimorph beam as sensor are calculated. In order to verify the derived equations for a hinged-hinged piezoelectric multilayer bending beam, the analytical calculation compared with ANSYS 10 results by some finite element examples. پرونده مقاله -
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68 - Thermal Buckling Analysis of Circular FGM Plate with Actuator/Actuator Piezoelectric Layer Based on Neutral Plane
محمد مهدی نجفی زاده محسن مالمراد آرش شریفیIn this paper, the thermal buckling analysis of a circular plate made of FGM materials with actuator/actuator piezoelectric layers based on neutral plane, classical plate theory and first order shear deformation plate theory is investigated. Reddy's model is assumed for چکیده کاملIn this paper, the thermal buckling analysis of a circular plate made of FGM materials with actuator/actuator piezoelectric layers based on neutral plane, classical plate theory and first order shear deformation plate theory is investigated. Reddy's model is assumed for material properties of FGM plate. Plate under the thermal loading, nonlinear temperature rise through the thickness and clamped edges is considered. Equilibrium and stability equations are drived using the calculus of variations and applying Euler equations. The obtained results are compared with the numerical values of the critical buckling temperature based on the theories mentioned above, and good agreement is observed between them. پرونده مقاله -
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69 - Design Servo System Type and Positioning of Pole Observer Full Rank a Piezoelectric Servo Valve without Integrator
مهدیه حامدی هادی همایی خیام صفریIn this paper, the method of modern control approach for the design of controller and observer is used. Other functions such as neural controllers - or fuzzy sliding mode control can be found in this work and the results are compared. First, a dynamic model of the servo چکیده کاملIn this paper, the method of modern control approach for the design of controller and observer is used. Other functions such as neural controllers - or fuzzy sliding mode control can be found in this work and the results are compared. First, a dynamic model of the servo valve is intended for the governing equations in state-space form expression are obtained. Due to the system integrator is expressed by the non-zero, The servo system of a full-order state observer pole positioning method to measure the dominant pole, Bessel and ITAE is designed and evaluated. Response to a step input to the system is designed and the observer's response to initial conditions. The curves show the comparison between systems is designed to do. پرونده مقاله -
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70 - Severe Impact on the Behavior of Energy Absorbing Cylindrical Base in Frontal Impact
عبدالمجید کنی اکبر علی بیگلوIn this paper, the vibration characteristics of multi-layer shell that internal and external surfaces with a layer of piezoelectric sensor and actuator is investigated. The backrest shell laminated with simple analytical method to evaluate and the results were compared چکیده کاملIn this paper, the vibration characteristics of multi-layer shell that internal and external surfaces with a layer of piezoelectric sensor and actuator is investigated. The backrest shell laminated with simple analytical method to evaluate and the results were compared with results obtained by other researchers. The numerical solution methods (GDQ) for shells with piezoelectric layers and plain bearings, compared with analytical solution and then a variety of boundary conditions is studied. Using the equations of motion, the fundamental equations and relations Krnsh- displacement, State-space equations derived the equations using approximate separate layer, State-space equations with constant coefficients will become. These equations can be solved using natural frequencies in the backrest shell simple to obtain. If the abutments are not simple, solving equations differentials State-space analysis is not possible and should be used numerical methods. A fourth difference method numerical method common with the small number of sample points can be exact to achieve. By dq, State-space differential equations are solved and the non-traction conditions by applying high and low levels, can be found at the natural frequency. The direct and inverse piezoelectric effect, piezoelectric layer and composite layer thickness ratio of the radius of the middle of a thick crust on the vibrational behavior is studied پرونده مقاله
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