Vibration analysis

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1 - Vibration Analysis of 2-PR(Pa)U- 2-PR(Pa)R New Parallel Mechanism
Mehran Mahboubkhah Sajjad Pakzad Morteza Homayoun Sadeghi Mir Mohammad Ettefagh

Parallel kinematic machines, are closed loop structures which have more accuracy, stiffness and ability to withstand high loads. In this paper the vibration equations of the new parallel mechanism, that has higher stiffness because of parallelogram system and fixed leng أکثر

Parallel kinematic machines, are closed loop structures which have more accuracy, stiffness and ability to withstand high loads. In this paper the vibration equations of the new parallel mechanism, that has higher stiffness because of parallelogram system and fixed length pods, have been derived by analytical approach. Whereas the proposed mechanism is applied as a machine tools, its vibrational behavior investigation has key impact factor. All the kinematic chains of the mechanism have been taken into consideration to achieve the coupled system of equations. To extract mechanism natural frequencies, modal analysis is carried out using three methods including analytical, finite element (FEM) and experimental method on parallel mechanism which has four degrees of freedom including three linear motion along the x, y and z axes and a rotary motion about x axis. Finally the natural frequencies and mode shapes obtained from analytical, experimental and FEM were compared. It is worth noting that all the frequencies obtained from three methods had little differences. تفاصيل المقالة

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2 - Vibration Analysis of a Multi-disk, Bearing and Mass Unbalance Rotor Using Assumed Modes Method
R. Norouzi M. Rafeeyan H. Dalayeli

In this paper, a simple and efficient method for modeling and solving the equations of a rotor with any number of disks, bearings and mass unbalances is presented using the assumed modes method. This model consists of a continuous shaft, arbitrary number of mass unbalan أکثر

In this paper, a simple and efficient method for modeling and solving the equations of a rotor with any number of disks, bearings and mass unbalances is presented using the assumed modes method. This model consists of a continuous shaft, arbitrary number of mass unbalances in any axial location and phase angle, and any number of rigid disks and bearings. This arrangement is extensively used in diverse applications. In this study, final governing differential equations are not derived because the assumed modes method is directly inserted to solving process. Some examples in both cases of free and forced vibration are performed. The results show the accuracy of this modeling and the ability of it to predicting the vibration behavior of the rotor in a complex combination of shaft, disk and bearing. This study also shows that the present approach can give the results as accurate as the most popular approach, i.e. the Finite Element Method. تفاصيل المقالة

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3 - Vibration Analysis of Rotary Tapered Axially Functionally Graded Timoshenko Nanobeam in Thermal Environment
N Shafiei M Hamisi M Ghadiri

10.22034/jsm.2019.563759.1273

In 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 أکثر

In 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. تفاصيل المقالة

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4 - Vibration Analysis of Size-Dependent Piezoelectric Nanobeam Under Magneto-Electrical Field
M Ghadiri M Karimi Asl M Noroozi

10.22034/jsm.2019.1864682.1446

The 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 أکثر

The 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. تفاصيل المقالة

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5 - Influence of Viscoelastic Foundation on Dynamic Behaviour of the Double Walled Cylindrical Inhomogeneous Micro Shell Using MCST and with the Aid of GDQM
A Mohammadi H Lashini M Habibi H Safarpour

10.22034/jsm.2019.665264

In this article, dynamic modeling of double walled cylindrical functionally graded (FG) microshell is studied. Size effect of double walled cylindrical FG microshell are investigated using modified couple stress theory (MCST). Each layer of microshell is embedded in a v أکثر

In this article, dynamic modeling of double walled cylindrical functionally graded (FG) microshell is studied. Size effect of double walled cylindrical FG microshell are investigated using modified couple stress theory (MCST). Each layer of microshell is embedded in a viscoelasticmedium. For the first time, in the present study, has been considered, FG length scale parameter in double walled cylindrical FG microshells, which this parameter changes along the thickness direction. Taking into consideration the first-order shear deformation theory (FSDT), double walled cylindrical FG microshell is modeled and its equations of motions are derived using Hamilton's principle. The novelty of this study is considering the effects of double layers and MCST, in addition to considering the various boundary conditions of double walled cylindrical FG microshell. Generalized differential quadrature method (GDQM) is used to discretize the model and to approximate the equation of motions and boundary conditions. Also, for confirmation, the result of current model is validated with the results obtained from molecular dynamics (MD) simulation. Considering length scale parameter (l=R/3) on MCST show, the results have better agreement with MD simulation. The results show that, length, thickness, FG power index, Winkler and Pasternak coefficients and shear correction factor have important role on the natural frequency of double walled cylindrical FG microshell. تفاصيل المقالة

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6 - A Novel Spring-Based Model for Damage Investigation of Functionally Graded Beams
S Karimi M Bozorgnsab R Taghipour M.M Alipour

10.22034/jsm.2021.1928249.1690

In this paper, free vibration analysis of damaged functionally graded beams based on the first-order shear deformation theory (FSDT) is carried out. In this regard, a new model of springs is introduced to model the damaged elements of the beam. The proposed model is ach أکثر

In this paper, free vibration analysis of damaged functionally graded beams based on the first-order shear deformation theory (FSDT) is carried out. In this regard, a new model of springs is introduced to model the damaged elements of the beam. The proposed model is achieved from stress resultants. The springs equations for homogeneous and functionally graded (FG) beams are presented; furthermore, equations for equivalent springs are also provided which can be used for both homogeneous and FG beams. The proposed method can be applied for the analysis of structures with fewer computation costs and high accuracy. To show the accuracy of the proposed model, the natural frequencies of the beams with real elements and the ones which are modeled by the proposed springs are compared considering various support conditions. Good agreement has been observed. Thereafter, the model is used to detect the damaged elements. The result shows that the model can properly detect the damage location. تفاصيل المقالة

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7 - Vibration Analysis of Magneto-Electro-Elastic Timoshenko Micro Beam Using Surface Stress Effect and Modified Strain Gradient Theory under Moving Nano-Particle
M Mohammadimehr H Mohammadi Hooyeh

In this article, the free vibration analysis of magneto-electro-elastic (MEE) Timoshenko micro beam model based on surface stress effect and modified strain gradient theory (MSGT) under moving nano-particle is presented. The governing equations of motion using Hamilton& أکثر

In this article, the free vibration analysis of magneto-electro-elastic (MEE) Timoshenko micro beam model based on surface stress effect and modified strain gradient theory (MSGT) under moving nano-particle is presented. The governing equations of motion using Hamilton’s principle are derived and these equations are solved using differential quadrature method (DQM). The effects of dimensionless electric potential, dimensionless magnetic parameter, material length scale parameter, external electric voltage, external magnetic parameter, slenderness ratio, temperature change, surface stress effect, two parameters of elastic foundation on the dimensionless natural frequency are investigated. It is shown that the effect of electric potential and magnetic parameter simultaneously increases the dimensionless natural frequency. On the other hands, with considering two parameters, the stiffness of MEE Timoshenko micro beam model increases. It can be seen that the dimensionless natural frequency of micro structure increases by MSGT more than modified couple stress theory (MCST) and classical theory (CT). It is found that by increasing the mass of nano-particle, the dimensionless natural frequency of system decreases. The results of this study can be employed to design and manufacture micro-devices to prevent resonance phenomenon or as a sensor to control the dynamic stability of micro structures. تفاصيل المقالة

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8 - A New Approach to the Study of Transverse Vibrations of a Rectangular Plate Having a Circular Central Hole
K Torabi A.R Azadi

In this study, the analysis of transverse vibrations of rectangular plate with circular central hole with different boundary conditions is studied and the natural frequencies and natural modes of a rectangular plate with circular hole have been obtained. To solve the pr أکثر

In this study, the analysis of transverse vibrations of rectangular plate with circular central hole with different boundary conditions is studied and the natural frequencies and natural modes of a rectangular plate with circular hole have been obtained. To solve the problem, it is necessary to use both Cartesian and polar coordinate system. The complexity of the method is to apply an appropriate model, which can solve the problem of transverse vibrations of a plate. So, it has been tried that the functions of the deflection of plate, in the form of polynomial functionsproportionate with finite degrees, to be replaced by Bessel function, which is used in the analysis of the vibrations of a circular plate. Then with the help of a semi-analytical method and orthogonality properties of the eliminated position angle, without any need to analyze so many points on the edges of the rectangular plate, we can prevent the coefficients matrix from becoming so much large as well as the equations from becoming complicated. The above mentioned functions will lead to reducing the calculation time and simplifying the equations as well as speeding up the convergence. تفاصيل المقالة

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9 - Global Optimization of Stacking Sequence in a Laminated Cylindrical Shell Using Differential Quadrature Method
M.R Saviz A Ziaei Asl

Based on 3-D elasticity approach, differential quadrature method (DQM) in axial direction is adopted along with Globalized Nelder–Mead (GNM) algorithm to optimize the stacking sequence of a laminated cylindrical shell. The anisotropic cylindrical shell has finite أکثر

Based on 3-D elasticity approach, differential quadrature method (DQM) in axial direction is adopted along with Globalized Nelder–Mead (GNM) algorithm to optimize the stacking sequence of a laminated cylindrical shell. The anisotropic cylindrical shell has finite length with simply supported boundary conditions. The elasticity approach, combining the state space method and DQM is used to obtain a relatively accurate objective function. Shell thickness is fixed and orientations of layers change in a set of angles. The partial differential equations are reduced to ordinary differential equations with variable coefficients by applying DQM to the equations, then, the equations with variables at discrete points are obtained. Natural frequencies are attained by solving the Eigen-frequency equation, which appears by incorporating boundary conditions into the state equation. A GNM algorithm is devised for optimizing composite lamination. This algorithm is implemented for maximizing the lowest natural frequency of cylindrical shell. The results are presented for stacking sequence optimization of two to five-layered cylindrical shells. Accuracy and convergence of developed formulation is verified by comparing the natural frequencies with the results obtained in the literature. Finally, the effects of mid-radius to thickness ratio, length to mid-radius ratio and number of layers on vibration behavior of optimized shell are investigated. Results are compared with those of Genetic Algorithm (GA) method, showing faster and more accurate convergence. تفاصيل المقالة

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10 - Dynamic Analysis of a Nano-Plate Carrying a Moving Nanoparticle Considering Eelectrostatic and Casimir Forces
A Ghgorbanpour Arani M Shokravi

This paper reports an analytical method to show the effect of electrostatic and Casimir forces on the pull-in instability and vibration of single nano-plate (SNP) carrying a moving nanoparticle. Governing equations for nonlocal forced vibration of the SNP under a moving أکثر

This paper reports an analytical method to show the effect of electrostatic and Casimir forces on the pull-in instability and vibration of single nano-plate (SNP) carrying a moving nanoparticle. Governing equations for nonlocal forced vibration of the SNP under a moving nanoparticle considering electrostatic and Casimir forces are derived by using Hamilton’s principle for the case when two ends are simply supported. The problem is solved by using the analytically and the time integration methods. The detailed parametric study is considered, focusing on the remarkable effects of the nanoparticle position, nonlocal parameters, nano-plate length, mode number, electric voltage of the Casimir parameter, and dielectric spacer with an initial gap on vibration of SNP. تفاصيل المقالة

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11 - Generalized Differential Quadrature Method for Vibration Analysis of Cantilever Trapezoidal FG Thick Plate
K Torabi H Afshari

This paper presents a numerical solution for vibration analysis of a cantilever trapezoidal thick plate. The material of the plate is considered to be graded through the thickness from a metal surface to a ceramic one according to a power law function. Kinetic and strai أکثر

This paper presents a numerical solution for vibration analysis of a cantilever trapezoidal thick plate. The material of the plate is considered to be graded through the thickness from a metal surface to a ceramic one according to a power law function. Kinetic and strain energies are derived based on the Reissner-Mindlin theory for thick plates and using Hamilton's principle, the governing equations and boundary conditions are derived in the Cartesian coordinates. A transformation of coordinates is used to convert the equations and boundary conditions from the original coordinate into a new computational coordinates. Generalized differential quadrature method (GDQM) is selected as a strong method and natural frequencies and corresponding modes are derived. The accuracy and convergence of the proposed solution are confirmed using results presented by other authors. Finally, the effect of the power law index, angles and thickness of the plate on the natural frequencies are investigated. تفاصيل المقالة

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12 - 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 Mohandes

In 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 أکثر

In 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. تفاصيل المقالة

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13 - In-Plane and out of Plane Free Vibration of U-Shaped AFM Probes Based on the Nonlocal Elasticity
M Ghadiri S.A.H Hosseini M Karami M Namvar

Atomic force microscope (AFM) has been developed at first for topography imaging; in addition, it is used for characterization of mechanical properties. Most researches have been primarily focused on rectangular single-beam probes to make vibration models simple. Recent أکثر

Atomic force microscope (AFM) has been developed at first for topography imaging; in addition, it is used for characterization of mechanical properties. Most researches have been primarily focused on rectangular single-beam probes to make vibration models simple. Recently, the U-shaped AFM probe is employed to determine sample elastic properties and has been developed to heat samples locally. In this study, a simplified analytical model of these U-shaped AFM is described and three beams have been used for modelling this probe. This model contains two beams are clamped at one end and connected with a perpendicular cross beam at the other end. The beams are supposed only in bending flexure and twisting, but their coupling allows a wide variety of possible dynamic behaviors. In the present research, the natural frequency and sensitivity of flexural and torsional vibration for AFM probes have been analyzed considering influence of scale effect. For this purpose, governing equations of dynamic behavior of U-shaped AFM probe are extracted based on Eringen's theory using Euler–Bernoulli beam theory and an analytical method is employed to solve these equations. The results in this paper have been extracted for different values of nonlocal parameters; it is shown that for a special case, there is a good agreement between reported results in available references and our results. The obtained results show that the frequencies of U-shaped AFM decrease with increasing the nonlocal parameter. تفاصيل المقالة

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14 - Semi-Analytical Solution for Free Vibration Analysis of Thick Laminated Curved Panels with Power-Law Distribution FG Layers and Finite Length Via Two-Dimensional GDQ Method
V Tahouneh M.H Naei

This paper deals with free vibration analysis of thick Laminated curved panels with finite length, based on the three-dimensional elasticity theory. Because of using two-dimensional generalized differential quadrature method, the present approach makes possible vibratio أکثر

This paper deals with free vibration analysis of thick Laminated curved panels with finite length, based on the three-dimensional elasticity theory. Because of using two-dimensional generalized differential quadrature method, the present approach makes possible vibration analysis of cylindrical panels with two opposite axial edges simply supported and arbitrary boundary conditions including Free, Simply supported and Clamped at the curved edges. The material properties vary continuously through the layers thickness according to a three-parameter power-low distribution. It is assumed that the inner surfaces of the FG sheets are metal rich while the outer surfaces of the layers can be metal rich, ceramic rich or made of a mixture of two constituents. The benefit of using the considered power-law distribution is to illustrate and present useful results arising from symmetric and asymmetric profiles. The effects of geometrical and material parameters together with the boundary conditions on the frequency parameters of the laminated FG panels are investigated. The obtained results show that the outer FGM Layers have significant effects on the vibration behavior of cylindrical panels. This study serves as a benchmark for assessing the validity of numerical methods or two-dimensional theories used to analysis of laminated curved panels. تفاصيل المقالة

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15 - A Simple and Systematic Approach for Implementing Boundary Conditions in the Differential Quadrature Free and Forced Vibration Analysis of Beams and Rectangular Plates
S.A Eftekhari

This paper presents a simple and systematic way for imposing boundary conditions in the differential quadrature free and forced vibration analysis of beams and rectangular plates. First, the Dirichlet- and Neumann-type boundary conditions of the beam (or plate) are expr أکثر

This paper presents a simple and systematic way for imposing boundary conditions in the differential quadrature free and forced vibration analysis of beams and rectangular plates. First, the Dirichlet- and Neumann-type boundary conditions of the beam (or plate) are expressed as differential quadrature analog equations at the grid points on or near the boundaries. Then, similar to CBCGE (direct Coupling the Boundary Conditions with the discrete Governing Equations) approach, the resulting analog equations are used to replace the differential quadrature analog equations of the governing differential equations at these points in order to solve the problem. But, unlike the CBCGE approach, the grid points near the boundaries are not treated as boundary points in the proposed approach. In other words, the degrees of freedom related to Dirichlet-type boundary conditions are only eliminated from the original discrete equations. This simplifies significantly the solution procedure and its programming. A comparison of the proposed approach with other existing methodologies such as the CBCGE approach and MWCM (modifying weighting coefficient matrices) method is presented by their application to the vibration analysis of beams and rectangular plates with general boundary conditions to highlight the advantages of the new approach. تفاصيل المقالة

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16 - Vibration Analysis of Orthotropic Triangular Nanoplates Using Nonlocal Elasticity Theory and Galerkin Method
A.R Shahidi S.H Shahidi A Anjomshoae E Raeisi Estabragh

In this article, classical plate theory (CPT) is reformulated using the nonlocal differential constitutive relations of Eringen to develop an equivalent continuum model for orthotropic triangular nanoplates. The equations of motion are derived and the Galerkin’s a أکثر

In this article, classical plate theory (CPT) is reformulated using the nonlocal differential constitutive relations of Eringen to develop an equivalent continuum model for orthotropic triangular nanoplates. The equations of motion are derived and the Galerkin’s approach in conjunction with the area coordinates is used as a basis for the solution. Nonlocal theories are employed to bring out the effect of the small scale on natural frequencies of nano scaled plates. Effect of nonlocal parameter, lengths of the nanoplate, aspect ratio, mode number, material properties, boundary condition and in-plane loads on the natural frequencies are investigated. It is shown that the natural frequencies depend highly on the non-locality of the nanoplate, especially at the very small dimensions, higher mode numbers and stiffer edge condition. تفاصيل المقالة

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17 - Coupled Vibration of Partially Fluid-Filled Laminated Composite Cylindrical Shells
M.R Saviz

In this study, the free vibration of partially fluid-filled laminated composite circular cylindrical shell with arbitrary boundary conditions has been investigated by using Rayleigh-Ritz method. The analysis has been carried out with strain-displacement relations based أکثر

In this study, the free vibration of partially fluid-filled laminated composite circular cylindrical shell with arbitrary boundary conditions has been investigated by using Rayleigh-Ritz method. The analysis has been carried out with strain-displacement relations based on Love’s thin shell theory and the contained fluid is assumed irrotational, incompressible and inviscid. After determining the kinetic and potential energies of fluid filled laminated composite shell, the eigenvalue problem has been obtained by means of Rayleigh-Ritz method. To demonstrate the validity and accuracy of the results, comparison has been made with the results of similar works for the empty and partially fluid-filled shells. Finally, an extensive parameter study on a typical composite tank is accomplished and some conclusions are drawn. تفاصيل المقالة

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18 - شناسایی عیوب یک الکتروگیربکس همزن مخزن با استفاده از آنالیز ارتعاشی
محسن غیاث ابادی فراهانی احمد عزیزی

در تحقیق حاضر به آنالیز ارتعاشات یک الکتروگیربکس همزن از نوع دنده حلزونی و علل پیدایش ارتعاشات شدید در این سیستم پرداخته شده است. نصب و نگهداری نادرست این سیستم‌ها می‌تواند آسیبهای جدی را برکارایی یک ماشین وارد آورد. داده برداری ارتعاشات توسط دستگاه دیتا آنالایزر Viber أکثر

در تحقیق حاضر به آنالیز ارتعاشات یک الکتروگیربکس همزن از نوع دنده حلزونی و علل پیدایش ارتعاشات شدید در این سیستم پرداخته شده است. نصب و نگهداری نادرست این سیستم‌ها می‌تواند آسیبهای جدی را برکارایی یک ماشین وارد آورد. داده برداری ارتعاشات توسط دستگاه دیتا آنالایزر Viber X5 انجام شده و تحلیل و تفسیر آن توسط نرم افزار SpectraPro صورت گرفته است. به کمک نتایج تحلیل از مهمترین آسیب‌های جدی گیربکس و تخریب قطعات جلوگیری شد و با انجام تعمیرات به موقع و جزئی در هزینه‌ها صرفه جویی بعمل آمد. در نتیجه ی آنالیز ارتعاشات با هدف ایجاد اطمینان جهت پیدا کردن عیوب سیستم، کمک مؤثری به جلوگیری از توقف‌های ناگهانی دستگاه‌ها و فرایند شکل گیری هزینه در سیستم می شود. این امر مهم، موجب شده است تا درسال‌های اخیر تمایل به استفاده از روش‌های آنالیز ارتعاشات و پیشرفت‌های تکنولوژی در این راستا بطور قابل توجهی افزایش یابد . تفاصيل المقالة

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19 - تحلیل ارتعاشی پوسته جعبه دنده ماشین سنگین با استفاده از روش اجزا محدود
حسام تراب زاده کاشی محسن مردانی

در این این مقاله بررسی تاثیر خواص مواد مختلف بر روی فرکانسهای طبیعی و شکل مود ارتعاشی پوسته دیفرانسیل نوعی ماشین سنگین مورد بررسی قرار گرفته است. خواص مکانیکی مواد مختلف نقش بسزایی در تعیین فرکانسهای خروجی و تغییر شکلهای ارتعاشی در یک سیستم ایفا میکنند. به این منظور در أکثر

در این این مقاله بررسی تاثیر خواص مواد مختلف بر روی فرکانسهای طبیعی و شکل مود ارتعاشی پوسته دیفرانسیل نوعی ماشین سنگین مورد بررسی قرار گرفته است. خواص مکانیکی مواد مختلف نقش بسزایی در تعیین فرکانسهای خروجی و تغییر شکلهای ارتعاشی در یک سیستم ایفا میکنند. به این منظور در نرم افزار طراحی CATIA مدل دیفرانسیل ایجاد و به نرم افزار شبیه ساز ABAQUS وارد شده است که قابلیت بالایی در تخمین رفتار دینامیکی سیستم‌های مختلف دارد. موادی نظیر چدن خاکستری با قابلیت جذب ارتعاش بالا، فولاد با چگالی و صلبیت زیاد و آلیاژهای آلومینیوم و منیزیم با چگالی پایین برای پوسته دیفرانسیل مورد بررسی قرار گرفته‌اند. نتایج بررسی نشان داد که محدوده فرکانس طبیعی پنج مود اول ارتعاشی در این مواد با یکدیگر متفاوت و انتخاب چدن خاکستری می‌تواند ضمن کاهش ارتعاش از ایجاد پدیده تشدید جلوگیری نماید. بخش دیگری از شبیه‌سازی عددی به بررسی تاثیر نوع اتصال بین دو قسمت دیفرانسیل بر روی رفتار دینامیکی اختصاص یافته است. به این منظور یکی از پیچ‌های اتصال دو قسمت دیفرانسیل به صورت محکم نشده در نرم افزار وارد شد، عیبی که ممکن است در هنگام تعمیرات توسط اپراتور ایجاد شود. نتایج شبیه‌سازی عددی حاکی از اینست که با محکم نکردن تنها یکی از پیچ‌های اتصال، فرکانس‌های طبیعی حدود 3 تا 4 درصد کاهش می‌یابد که این امر می‌تواند احتمال ایجاد پدیده تشدید را افزایش دهد. تفاصيل المقالة

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20 - 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 هاشمیان

امروزه 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 أکثر

امروزه 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. تفاصيل المقالة

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21 - تشخیص عیوب ماشینهای دوار با آنالیز ارتعاشات و استفاده از شبکه ‏عصبی
سید مجید عطایی اردستانی

مبنای تشخیص معایب احتمالی یک ماشین، مقایسه طیف‌های فرکانسی ارتعاشات نقاط مختلف آن با طیف‌های مرجع موجود است. استفاده از این روش عیب‌یابی مقرون به صرفه است چرا که بدون نیاز به توقف ماشین، می‌توان وضعیت نقاط مختلف آن را تحت بررسی قرار داد و همچنین فقط در مواقع لازم و أکثر

مبنای تشخیص معایب احتمالی یک ماشین، مقایسه طیف‌های فرکانسی ارتعاشات نقاط مختلف آن با طیف‌های مرجع موجود است. استفاده از این روش عیب‌یابی مقرون به صرفه است چرا که بدون نیاز به توقف ماشین، می‌توان وضعیت نقاط مختلف آن را تحت بررسی قرار داد و همچنین فقط در مواقع لازم و با توجه به میزان پیشرفت عیوب احتمالی، می‌توان اقدام به تعمیر آن نمود. در این تحقیق، از شبکه‌ی عصبی پرسپترون چند لایه ( MLP ) و شبکه عصبی پیشخور ( FNN ) استفاده شده است. همچنین عیوب متداول در ماشین‌آلات دوار بطور جداگانه ایجاد شد و فرکانس ارتعاشی تولیدی توسط دستگاه آنالیزور ADASH 4400&lrm; اندازه‌گیری گردید. با معرفی چهار ویژگی ارتعاشی شامل ناهمراستایی زاویه‌ای، لقی، خرابی و نابالانسی بیرینگ بعنوان داده‌های ورودی به شبکه‌های عصبی مصنوعی، نتایج با سیگنالهای فرکانسی مرجع مقایسه گردید. &lrm; &lrm;نتایج نشان می‌دهد که شبکه‌های عصبی MLP و FNN به ترتیب تا 73% و 78% توانایی تشخیص عیوب را دارند. بنابراین روش FNN برای پیش‌بینی و شناسایی عمر مفید قطعات دوار پیشنهاد می‌گردد. تفاصيل المقالة

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22 - Free vibration analysisof soft-core composite-faced sandwich plates using three-dimensional finite element method
Mohammad Mahdi Kheirikhah Hasan Aghabarati Pooneh Khosravi

In this paper, natural frequencies of the sandwich plates with soft flexible core and composite face sheets are obtained. Three-Dimensional (3D) finite element method (FEM) is used for constructing and analyzing of the sandwich plates to obtain their natural frequencies أکثر

In this paper, natural frequencies of the sandwich plates with soft flexible core and composite face sheets are obtained. Three-Dimensional (3D) finite element method (FEM) is used for constructing and analyzing of the sandwich plates to obtain their natural frequencies. Continuity conditions for transverse shear stresses at the interfaces as well as transverse flexibility and transverse normal strain and stress of the core are considered.The effects of plate dimensions such as aspect ratio and thickness ratio are studied. Also, different boundary conditions such as all edges clamped (CCCC), all edges simply supported (SSSS) and combined boundary conditions including (CFCF)are applied to the sandwich plates. Comparison of the present results in special case with those of the accurate plate theories confirms the accuracy of the proposedmodel. تفاصيل المقالة

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23 - به کارگیری تکنیک پایش وضعیت برای دست یابی به بهبود کارایی در صنعت (مطالعه موردی: صنایع چوب و کاغذ مازندران)
محمد مهدی موحدی ولی الله رضایی نصرتی

مدیران امروز سعی می کنند تا با استفاده از روش‌های علمی علاوه بر افزایش کیفیت محصولات، قیمت تمام شده آن را هم کاهش دهند. پایش وضعیت[1] یکی از فنونی است که در سال‌های اخیر مورد استقبال بیشتر مدیران صنعت قرار گرفته و البته منافع زیادی را هم عاید سازمان‌ها نموده است. تحلیل أکثر

مدیران امروز سعی می کنند تا با استفاده از روش‌های علمی علاوه بر افزایش کیفیت محصولات، قیمت تمام شده آن را هم کاهش دهند. پایش وضعیت[1] یکی از فنونی است که در سال‌های اخیر مورد استقبال بیشتر مدیران صنعت قرار گرفته و البته منافع زیادی را هم عاید سازمان‌ها نموده است. تحلیل ارتعاشات[2] یکی از روش‌های پایش وضعیت است که با به کارگیری آن در صنعت به طور چشمگیری می‌توان از دوباره کاری ها جلوگیری نمود و هزینه‌های یک شرکت تولیدی را کاهش داد. برای نشان دادن تأثیر این فن در بهبود کارایی فرآیند تولید، شرکت صنایع چوب و کاغذ مازندران به عنوان مطالعه موردی انتخاب شده و نحوه‌ی استفاده صحیح از سیستم پایش وضعیت از طریق تحلیل ارتعاشات مورد بررسی قرار گرفته است. در این تحقیق مشخص شده است که چگونه می‌توان با آگاهی به موقع از خرابی‌های دستگاه‌ها و اعمال تعمیرات پیشگیرانه جلوی زیان قبل از وقوع گرفته شود و ثانیاً در مصرف قطعات و وقت نیروی انسانی در نگهداری و تعمیر ماشین‌آلات صرفه جویی شده و در نهایت سازمان به سمت بهبود کارایی هدایت شود. [1] . Condition Monitoring [2] . Vibration Analysis تفاصيل المقالة

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24 - Study of Vibration Specifications of a Three-axle Truck Using Lagrange Method
Seyed Mohammad Javad Zeidi Pedram Hoseini Ali Rahmani

In this research, Ride quality of a three-axle truck is investigated to understand its vibrationspecifications and influence of it on special load. The truck is Benz 2624, and the load is rathersensitive to vibrations. The system is considered for an off-road duty. Henc أکثر

In this research, Ride quality of a three-axle truck is investigated to understand its vibrationspecifications and influence of it on special load. The truck is Benz 2624, and the load is rathersensitive to vibrations. The system is considered for an off-road duty. Hence, the vehicle is modeledas a nineteen-degree of freedom system and its equations of motion are derived by employingLagrange equation. Since, the physical parameters of the vehicle were not available; the truck ismodeled in Solidworks CAD software in order to obtain the material and dynamic properties ofeach component of the truck. Then, a code is developed in MATLAB to calculate naturalfrequencies and mode shapes of the truck and their corresponding vibrating components in criticalspeed. A simple model of the truck in ADAMS is employed for validation. The adoption of theresults verifies the equations. The developed model can also be used in newer truck with somemodifications. It is also necessary to have accurate data for input information in order to change thecurrent model for other utilities. تفاصيل المقالة

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25 - Formulation of a new finite element based on assumed strains for membrane structures
Lahcene Fortas Lamine Belounar Tarek Merzouki

10.30495/ijase.2019.705775

AbstractIn this paper, a new triangular membrane finite element with in-plane drilling rotation has been developed using the strainbasedapproach for static and free vibration analyses. The proposed element, having three degrees of freedom at each of thethree corner node أکثر

AbstractIn this paper, a new triangular membrane finite element with in-plane drilling rotation has been developed using the strainbasedapproach for static and free vibration analyses. The proposed element, having three degrees of freedom at each of thethree corner nodes, is based on assumed strain functions satisfying both compatibility and equilibrium equations. Numericalinvestigations have been conducted using several tests, including static and free vibration problems, and the obtained resultsare compared with analytical and numerical available solutions. It is found that efficient convergence characteristics andaccurate results can be achieved using the developed element. تفاصيل المقالة

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26 - AN INTELLIGENT FAULT DIAGNOSIS APPROACH FOR GEARS AND BEARINGS BASED ON WAVELET TRANSFORM AS A PREPROCESSOR AND ARTIFICIAL NEURAL NETWORKS
Mahmuod Akbari Hadi Homaei Mohammad Heidari

In this paper, a fault diagnosis system based on discrete wavelet transform (DWT) and artificial neural networks (ANNs) is designed to diagnose different types of fault in gears and bearings. DWT is an advanced signal-processing technique for fault detection and identif أکثر

In this paper, a fault diagnosis system based on discrete wavelet transform (DWT) and artificial neural networks (ANNs) is designed to diagnose different types of fault in gears and bearings. DWT is an advanced signal-processing technique for fault detection and identification. Five features of wavelet transform RMS, crest factor, kurtosis, standard deviation and skewness of discrete wavelet coefficients of normalized vibration signals has been selected. These features are considered as the feature vector for training purpose of the ANN. A wavelet selection criteria, Maximum Energy to Shannon Entropy ratio, is used to select an appropriate mother wavelet and discrete level, for feature extraction. To ameliorate the algorithm, various ANNs were exploited to optimize the algorithm so as to determine the best values for ‘‘number of neurons in hidden layer” resulted in a high-speed, meticulous three-layer ANN with a small-sized structure. The diagnosis success rate of this ANN was 100% for experimental data set. Some experimental set of data has been used to verify the effectiveness and accuracy of the proposed method. To develop this method in general fault diagnosis application, three different examples were investigated in cement industry. In first example a MLP network with well-formed and optimized structure (20:15:7) and remarkable accuracy was presented providing the capability to identify different faults of gears and bearings. In second example a neural network with optimized structure (20:15:4) was presented to identify different faults of bearings and in third example an optimized network (20:15:3) was presented to diagnose different faults of gears. The performance of the neural networks in learning, classifying and general fault diagnosis were found encouraging and can be concluded that neural networks have high potential in condition monitoring of the gears and bearings with various faults. تفاصيل المقالة

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27 - On the dynamic stability of a flying vehicle under the follower and transversal forces
Omid Kavianipour Majid Sohrabian

This paper deals with the problem of the instability regions of a free-free uniform Bernoulli beam consisting of two concentrated masses at the two free ends under the follower and transversal forces as a model for a space structure. The follower force is the model for أکثر

This paper deals with the problem of the instability regions of a free-free uniform Bernoulli beam consisting of two concentrated masses at the two free ends under the follower and transversal forces as a model for a space structure. The follower force is the model for the propulsion force and the transversal force is the controller force. The main aim of this study is to analyze the effects of the concentrated masses on the beam instability. It is determined that the transverse and rotary inertia of the concentrated masses cause a change in the critical follower force. This paper also offers an approximation method as a design tool to find the optimal masses at the two tips using an artificial neural network (ANN) and genetic algorithm (GA). The results show that an increase in the follower and transversal forces leads to an increase of the vibrational motion of the beam which is not desirable for any control system and hence it must be removed by proper approaches. تفاصيل المقالة

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28 - Free Vibration Analysis of Sandwich Micro Beam with Piezoelectric Based on Modified Couple Stress Theory and Surface Effects
Mohammad khajekhabaz Ali Eftekhari Mohammad Hashemian

In this paper, the free vibration analysis of sandwich micro beam with piezoelectric layers based on the modified couple stress and surface elasticity theories are investigated. The Hamilton’s principle is employed to derive the sandwich micro beam with piezoelect أکثر

In this paper, the free vibration analysis of sandwich micro beam with piezoelectric layers based on the modified couple stress and surface elasticity theories are investigated. The Hamilton’s principle is employed to derive the sandwich micro beam with piezoelectric based on modified couple stress theory incorporating with Gurtin- Murdoch surface theory. The generalized differential quadrature method is used to discretize the partial differential equation into the ordinary differential equation. The effect of various parameters such as thickness to material length scale parameter ratio, the surface residual stress, Young's modulus of surface layer, surface mass density and surface piezoelectric constant are investigated by comparing the results obtained using the modified couple and classical theories. Numerical results of this problem evaluate the effect of micro length scale parameters on natural frequency. The results show that surface parameter effects are significant when the model is small, but can be neglected with increasing model size. تفاصيل المقالة

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29 - Disk Vibration Analysis of Functionally Graded Materials
محبوبه روائی حسن نحوی

Perforated discs have many applications in different parts of industry. By making such disks of functionally graded materials, more capabilities can be obtained from them. Vibration analysis of these kinds of disks can help us make them more efficient. In this paper, mo أکثر

Perforated discs have many applications in different parts of industry. By making such disks of functionally graded materials, more capabilities can be obtained from them. Vibration analysis of these kinds of disks can help us make them more efficient. In this paper, modeling and evaluation of disk vibration of functionally graded materials with regard to thickness were carried out using Abaqus software. Since no certain element has been defined regarding functionally graded materials for the design and analysis of a particular element in Abaqus software, molding of such materials has been used in this application. In order to verify the results, the results obtained from ABAQUS analysis have been compared with those available in the literature. The obtained results show that by defining more layers with regard to changes in properties, the obtained results approach the exact solutions. تفاصيل المقالة

فهرس المقالات Vibration analysis

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