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دسترسی آزاد مقاله
1 - تحلیل یک مدولاتور الکترواپتیک بر پایه کاواک نانو پرتو بلور فوتونی تک‌بعدی همراه با ساختار متناوب گرافن بر اکسید آلومینیوم
مظفرالدین فردوسیان طهرانی رحیم غیور مریم محیط پوردر این مقاله، ما یک مدولاتور الکترو - اپتیک بر اساس جذب گرافن ارائه می‌کنیم. در این ساختار، گرافن بر روی اکسید آلومینیوم قرار گرفته که ساختار به صورت متناوب تکرار می‌شود. این ساختار متناوب گرافن بر اکسید آلومینیوم در داخل یک حفره نیم‌استوانه‌ای، درون یک کاواک نانو پرتو چکیده کاملدر این مقاله، ما یک مدولاتور الکترو - اپتیک بر اساس جذب گرافن ارائه می‌کنیم. در این ساختار، گرافن بر روی اکسید آلومینیوم قرار گرفته که ساختار به صورت متناوب تکرار می‌شود. این ساختار متناوب گرافن بر اکسید آلومینیوم در داخل یک حفره نیم‌استوانه‌ای، درون یک کاواک نانو پرتو بلور فوتونی یک بعدی قرار گرفته است. برخلاف مقالات قبلی که کاواک نانو پرتو بلور فوتونی یک بعدی شامل حفره‌های استوانه‌ای بوده و نواحی مختلف با تغییر شعاع این حفره‌ها ایجاد می‌شد، در این ساختار از حفره‌های نیمه استوانه‌ای استفاده شده و با چرخش این نیم‌استوانه‌ها، نواحی مختلف ساختار کاواک نانو پرتو بلور فوتونی ایجاد می‌شود. این نوع بلور فوتونی دارای ضریب کیفیت بالایی است. همچنین این نوع مدولاتورها پس از ساخت به فضای کمی نیاز دارند، بنابراین گزینه بسیار مناسبی برای مدارهای مجتمع هستند. در این مقاله از روش دامنه محدود در حوزه زمان - سه‌بعدی برای تحلیل استفاده شده است. در این مدولاتور مشاهده می‌شود که با تغییر ولتاژ بایاس میزان پیک جذب و همچنین طول موج رزونانس آن تغییر می‎کند. در نتیجه این تغییرات، به عمق مدولاسیونی در حدود ۷ دسی‌بل دست می‌یابیم. ساختار پیشنهادی ما می‌تواند کاربردهای بالقوه‌ای در مدارهای مجتمع نوری، به‌ویژه در فرکانس‌های مخابراتی داشته باشد. پرونده مقاله -
دسترسی آزاد مقاله
2 - Vibration Analysis of Rotary Tapered Axially Functionally Graded Timoshenko Nanobeam in Thermal Environment
N Shafiei M Hamisi M GhadiriIn this paper, vibration analysis of rotary tapered axially functionally graded (AFG) Timoshenko nanobeam is investigated in a thermal environment based on nonlocal theory. The governing equations of motion and the related boundary conditions are derived by means of Ham چکیده کاملIn this paper, vibration analysis of rotary tapered axially functionally graded (AFG) Timoshenko nanobeam is investigated in a thermal environment based on nonlocal theory. The governing equations of motion and the related boundary conditions are derived by means of Hamilton’s principle based on the first order shear deformation theory of beams. The solution method is considered using generalized differential quadrature element (GDQE) method. The accuracy of results are validated by other results reported in other references. The effect of various parameters such as AFG index, rate of cross section change, angular velocity, size effect and boundary conditions on natural frequencies are discussed comprehensively. The results show that with increasing angular velocity, non-dimensional frequency is increased and it depends on size effect parameter. Also, in the zero angular velocity, it can be seen with increasing AFG index, the frequencies are reducing, but in non-zero angular velocity, AFG index shows complex behavior on frequency. پرونده مقاله -
دسترسی آزاد مقاله
3 - Refined Zigzag Theory for Nonlinear Dynamic Response of an Axially Moving Sandwich Nanobeam Embedded on Visco-Pasternak Medium Using MCST
A Ghorbanpour Arani M AbdollahianThis paper develops the Refined Zigzag Theory (RZT) for nonlinear dynamic response of an axially moving functionally graded (FG) nanobeam integrated with two magnetostrictive face layers based on the modified couple stress theory (MCST). The sandwich nanobeam (SNB) subj چکیده کاملThis paper develops the Refined Zigzag Theory (RZT) for nonlinear dynamic response of an axially moving functionally graded (FG) nanobeam integrated with two magnetostrictive face layers based on the modified couple stress theory (MCST). The sandwich nanobeam (SNB) subjected to a temperature difference and both axial and transverse mechanical loads. The material properties of FG core layer depend on the environment temperature and are assumed to vary in thickness direction. The SNB is surrounded by elastic medium which is simulated by visco-Pasternak model. The von-Karman nonlinear strain-displacement relationships are employed to consider the effect of geometric nonlinearities. In order to obtain governing motion equations and boundary conditions the energy method as well as Hamilton’s principle is applied. The differential quadrature method (DQM) is used for space domain and the Newmark-β method is taken into account for time domain response of the axially moving SNB. The detailed parametric study is conducted to investigate the effects of surrounding elastic medium, material length scale parameter, magnetostrictive layers, temperature difference, environment temperature, velocity of the SNB, axial and transverse mechanical loads and volume fraction exponent on the dynamic response of the SNB. Results indicate that the maximum deflection of the system can be controlled by employing negative values of velocity feedback gain values. Also, the system loses its stability when the velocity of SNB is increased. پرونده مقاله -
دسترسی آزاد مقاله
4 - 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
5 - Considering Bending and Vibration of Homogeneous Nanobeam Coated by a FG Layer
H Salehipour M Jamshidi A ShahsavarIn this research static deflection and free vibration of homogeneous nanobeams coated by a functionally graded (FG) layer is investigated according to the nonlocal elasticity theory. A higher order beam theory is used that does not need the shear correction factor. The چکیده کاملIn this research static deflection and free vibration of homogeneous nanobeams coated by a functionally graded (FG) layer is investigated according to the nonlocal elasticity theory. A higher order beam theory is used that does not need the shear correction factor. The equations of motion (equilibrium equations) are extracted by using Hamilton’s principle. The material properties are considered to vary in the thickness direction of FG coated layer. This nonlocal nanobeam model incorporates the length scale parameter (nonlocal parameter) that can capture the small scale effects. In the numerical results section, the effects of different parameters, especially the ratio of thickness of FG layer to the total thickness of the beam are considered and discussed. The results reveal that the frequency is maximum for a special value of material power index. Also, increasing the ratio of thickness of FG layer to the total thickness of the beam increases the static deflection and decreases the natural frequencies. These results help with the understanding such coated structures and designing them carefully. The results also show that the new nonlocal FG nanobeam model produces larger vibration and smaller deflection than homogeneous nonlocal nanobeam. پرونده مقاله -
دسترسی آزاد مقاله
6 - Size-Dependent Higher Order Thermo-Mechanical Vibration Analysis of Two Directional Functionally Graded Material Nanobeam
M Mahinzare S Amanpanah M GhadiriThis paper represented a numerical technique for discovering the vibrational behavior of a two-directional FGM (2-FGM) nanobeam exposed to thermal load for the first time. Mechanical attributes of two-directional FGM (2-FGM) nanobeam are changed along the thickness and چکیده کاملThis paper represented a numerical technique for discovering the vibrational behavior of a two-directional FGM (2-FGM) nanobeam exposed to thermal load for the first time. Mechanical attributes of two-directional FGM (2-FGM) nanobeam are changed along the thickness and length directions of nanobeam. The nonlocal Eringen parameter is taken into the nonlocal elasticity theory (NET). Uniform temperature rise (UTR), linear temperature rise (LTR), non-linear temperature rise (NLTR) and sinusoidal temperature rise (STR) during the thickness and length directions of nanobeam is analyzed. Third-order shear deformation theory (TSDT) is used to derive the governing equations of motion and associated boundary conditions of the two-directional FGM (2-FGM) nanobeam via Hamilton’s principle. The differential quadrature method (DQM) is employed to achieve the natural frequency of two-directional FGM (2-FGM) nanobeam. A parametric study is led to assess the efficacy of coefficients of two-directional FGM (2-FGM), Nonlocal parameter, FG power index, temperature changes, thermal rises loading and temperature rises on the non-dimensional natural frequencies of two-directional FGM (2-FGM) nanobeam. پرونده مقاله -
دسترسی آزاد مقاله
7 - Surface Effects on Free Vibration Analysis of Nanobeams Using Nonlocal Elasticity: A Comparison Between Euler-Bernoulli and Timoshenko
Sh Hosseini – Hashemi M Fakher R NazemnezhadIn this paper, surface effects including surface elasticity, surface stress and surface density, on the free vibration analysis of Euler-Bernoulli and Timoshenko nanobeams are considered using nonlocal elasticity theory. To this end, the balance conditions between nanob چکیده کاملIn this paper, surface effects including surface elasticity, surface stress and surface density, on the free vibration analysis of Euler-Bernoulli and Timoshenko nanobeams are considered using nonlocal elasticity theory. To this end, the balance conditions between nanobeam bulk and its surfaces are considered to be satisfied assuming a linear variation for the component of the normal stress through the nanobeam thickness. The governing equations are obtained and solved for Silicon and Aluminum nanobeams with three different boundary conditions, i.e. Simply-Simply, Clamped-Simply and Clamped-Clamped. The results show that the influence of the surface effects on the natural frequencies of the Aluminum nanobeams follows the order CC پرونده مقاله -
دسترسی آزاد مقاله
8 - Effect of Surface Energy on the Vibration Analysis of Rotating Nanobeam
M Safarabadi M Mohammadi A Farajpour M GoodarziIn this study, the free vibration behavior of rotating nanobeam is studied. Surface effects on the vibration frequencies of nanobeam are considered. To incorporate surface effects, Gurtin–Murdoch model is proposed to satisfy the surface balance equations of the co چکیده کاملIn this study, the free vibration behavior of rotating nanobeam is studied. Surface effects on the vibration frequencies of nanobeam are considered. To incorporate surface effects, Gurtin–Murdoch model is proposed to satisfy the surface balance equations of the continuum surface elasticity. Differential quadrature method is employed and in order to establish the accuracy and applicability of the proposed model, the numerical results are presented to be compared with those available in the literature. The effects of angular velocity, boundary conditions and surface elastic constants on the vibration characteristics are presented. Numerical results show that the softer boundary conditions cause an increase in the influence of the angular velocity on the nanobeam vibration frequencies. پرونده مقاله -
دسترسی آزاد مقاله
9 - A Modified Couple Stress Theory for Postbuckling Analysis of Timoshenko and Reddy-Levinson Single-Walled Carbon Nanobeams
M Akbarzadeh Khorshidi M ShariatiThe novelty of this study is presentation of an exact solution for prediction of postbuckling behavior of shear deformable micro- and nano-scale beams based on modified couple stress theory and using principle of minimum potential energy. Timoshenko and Reddy-Levinson b چکیده کاملThe novelty of this study is presentation of an exact solution for prediction of postbuckling behavior of shear deformable micro- and nano-scale beams based on modified couple stress theory and using principle of minimum potential energy. Timoshenko and Reddy-Levinson beam theories are applied to consider the shear deformation effect and Von Karman nonlinear kinematics is used to describe the nonlinear behavior of the postbuckling, and the Poisson's effect is also considered in stress-strain relation. Also, the size effect is exposed by introducing a material length scale parameter. Finally, the influences of shear deformation, Poisson's ratio and variations of length and thickness are investigated. The results indicate that the classical theory exaggerates the postbuckling amplitude of the nanobeam and overstates the effect of shear deformation on the postbuckling response of the nanobeam. پرونده مقاله -
دسترسی آزاد مقاله
10 - 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 -
دسترسی آزاد مقاله
11 - Dynamic stability analysis of functionally graded Euler-Bernoulli nanobeams under a sequence of moving nanoparticle based on nonlocal elasticity theory
Rahman Khanahmadi Mohammad Hashemian Mostafa PirmoradianThis study investigates the dynamic stability of the Euler-Bernoulli functionally graded (FGM) nanobeam based on the nonlocal elasticity theory while considering surface effects. Nanoparticles pass over nanobeam sequentially with a constant velocity, and the nanoparticl چکیده کاملThis study investigates the dynamic stability of the Euler-Bernoulli functionally graded (FGM) nanobeam based on the nonlocal elasticity theory while considering surface effects. Nanoparticles pass over nanobeam sequentially with a constant velocity, and the nanoparticle inertia is also considered. A thermal gradient with constant temperature changes is applied to this nanobeam. The functionally graded nanobeam properties, including Young’s modulus, density, surface residual stress, and surface modulus are taken by the power law. The classical equations of motion are obtained by applying the Hamilton’s principle according to the energy method. The governing equations are extracted using nonlocal elasticity theory, and the surface effects are taken by Gurtin-Murdoch theory. The dynamic stability graphs will be presented on nanoparticle mass-velocity coordinates. This article investigated the small scale effect parameter, temperature changes, Pasternak environment shearing and elastic constants, and the volume fraction parameter in power law. The results show that increasing Pasternak foundation constants increase the functionally graded nanobeam stability, and increasing small scale parameter reduces its stability. Increasing nanobeam temperature shifts the functionally graded stability region of nanobeam towards faster nanoparticle velocity, which indicates a higher dynamic stability for the nanobeam. پرونده مقاله -
دسترسی آزاد مقاله
12 - Dynamic Stability of Nano FGM Beam Using Timoshenko Theory
شهاب صفاری محمد هاشمیانBased on the nonlocal Timoshenko beam theory, the dynamic stability of functionally gradded (FG) nanoeams under axial load is studied in thermal environment, with considering surface effect. It is used power law distribution for FGM and the surface stress effects are co چکیده کاملBased on the nonlocal Timoshenko beam theory, the dynamic stability of functionally gradded (FG) nanoeams under axial load is studied in thermal environment, with considering surface effect. It is used power law distribution for FGM and the surface stress effects are considered based on Gurtin-Murdoch continuum theory. Using Von Karman geometric nonlinearity, governing equations are derived based on Hamilton’s principle. The developed nonlocal models have the capability to interpret small scale effects. Winkler and Pasternak types elastic foundation are employed to represent the interaction of the nano FG beam and the surrounding elastic medium. A parametric study is conducted to investigate the influences of the static load factor, temperature change, nonlocal elastic parameter, slenderness ratio, surface effect and springs constant of the elastic medium on the dynamic stability characteristics of the FG beam, with simply-supported boundary conditions. It is found that the difference between instability regions predicted by local and nonlocal beam theories is significant for nanobeams with lower aspect ratios. Moreover, it is observed that in contrast to high temperature environments, at low temperatures, increasing the temperature change moves the origins of the instability regions to higher excitation frequencies and leads to further stability of the system at lower excitation frequencies, considering surface stress effect shifts the FG beam to higher frequency zone پرونده مقاله
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