

مجله مكانيك جامدات
Journal of Solid Mechanics
ISSN 20083505
فصلنامه داراي رتبه علمي  پژوهشي (فني مهندسي) به زبان انگليسي
سال دهم، شماره 2، Spring 2018




 Wave Propagation Analysis of CNT Reinforced Composite MicroTube Conveying Viscose Fluid in ViscoPasternak Foundation Under 2D MultiPhysical Fields A.H. Ghorbanpour Arani , M.M. Aghdam , M.J. Saeedian Pages 232248 Abstract Full Text [PDF 1022KB]   In this research، wave propagation analysis in polymeric smart nanocomposite microtubes reinforced by singlewalled carbon nanotubes (SWCNT) conveying fluid is studied. The surrounded elastic medium is simulated by viscoPasternak model while the composite microtube undergoes electromagnetomechanical 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 NavierStokes equation. Microtube is simulated by EulerBernoulli 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.
Keywords: Waves; Beams; Fibre reinforced composites; Piezoelectricity; Fluid dynamics; Magnetic field.
  
 Combination Resonance of Nonlinear Rotating Balanced Shafts Subjected to Periodic Axial Load M.S. Qaderi , S.A.A. Hosseini , M. Zamanian Pages 249262 Abstract Full Text [PDF 787KB]   Dynamic behavior of a circular shaft with geometrical nonlinearity and constant spin، subjected to periodic axial load is investigated. The case of parametric combination resonance is studied. Extension of shaft center line is the source of nonlinearity. The shaft has gyroscopic effect and rotary inertia but shear deformation is neglected. The equations of motion are derived by extended Hamilton principle and discretized by Galerkin method. The multiple scales method is applied to the complex form of equation of motion and the system under parametric combination resonance is analyzed. The attention is paid to analyze the effect of various system parameters on the shape of resonance curves and amplitude of system response. Furthermore، the role of external damping on combination resonance of linear and nonlinear systems is discussed. It will be shown that the external damping has different role in linear and nonlinear shaft models. To validate the perturbation results، numerical simulation is used.
Keywords: Rotating shaft; Parametric excitation; Multiple scales method.
  
 Fracture Analysis of Externally SemiElliptical Crack in a Spherical Pressure Vessel with HoopWrapped Composite H. Eskandari , Gh. Rashed , F. Mirzade Pages 263270 Abstract Full Text [PDF 913KB]   In this paper the effect of composite hoopwrapped on stress intensity factor for semielliptical external crack which located in spherical pressure vessel، were investigated through the Finite Element Analysis. In order to find the effect of some parameters such as composite thickness and width، internal pressure and crack geometry، comparisons between different cases were done and discussed in detail. The result show that repairing crack with composite hoopwrapped، can significantly reduce the stress intensity factor along the crack front.
Keywords: Stress intensity factor; Semi, elliptical crack; Spherical pressure vessel; Composite layer.
  
 Mathematical Modeling for Thermoelastic Double Porous MicroBeam Resonators R. Kumar , R. Vohra , M.G. Gorla Pages 271284 Abstract Full Text [PDF 618KB]   In the present work، the mathematical model of a homogeneous، isotropic thermoelastic double porous microbeam، based on the EulerBernoulli theory is developed in the context of LordShulman [1] theory of thermoelasticity. Laplace transform technique has been used to obtain the expressions for lateral deflection، axial stress، axial displacement، volume fraction field and temperature distribution. A numerical inversion technique has been applied to recover the resulting quantities in the physical domain. Variations of axial displacement، axial stress، lateral deflection، volume fraction field and temperature distribution with axial distance are depicted graphically to show the effects of porosity and thermal relaxation time. Some particular cases are also deduced.
Keywords: Double porosity; Thermoelasticity; Lord, shulman theory; Micro, beam.
  
 InPlane and out of Plane Free Vibration of UShaped AFM Probes Based on the Nonlocal Elasticity M. Ghadiri , S.A.H. Hosseini , M. Karami , M. Namvar Pages 285299 Abstract Full Text [PDF 1163KB]   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 singlebeam probes to make vibration models simple. Recently، the Ushaped 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 Ushaped 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 Ushaped 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 Ushaped AFM decrease with increasing the nonlocal parameter.
Keywords: U, shaped probe; AFM; Nonlocal elasticity theory; Euler–Bernoulli beam theory; Vibration analysis.
  
 Determination of Optimal Parameters for Finite Plates with a QuasiSquare Hole M. Jafari , M. H. Bayati Chaleshtari , E. Ardalani Pages 300314 Abstract Full Text [PDF 1009KB]   This paper aims at optimizing the parameters involved in stress analysis of perforated plates، in order to achieve the least amount of stress around the squareshaped holes located in a finite isotropic plate using metaheuristic optimization algorithms. Metaheuristics may be classified into three main classes: evolutionary، physicsbased، and swarm intelligence algorithms. This research uses Genetic Algorithm (GA) from evolutionary algorithm category، Gravitational Search Algorithm (GSA) from physicsbased algorithm category and Bat Algorithm (BA) from Swarm Intelligence (SI) algorithm category. The results obtained from the present study necessitate the determination of the actual boundary between finite and infinite plate for the plates with squareshaped holes. The design variables such as bluntness، hole orientation، and plate dimension ratio as effective parameters on stress distribution are investigated. The results obtained from comparing BA، GA and GSA indicate that BA as SI algorithm category competitive results، proper convergence to global optimal solution and more optimal stress level than the two mentioned algorithms. The obtained results showed that the aforementioned parameters have a significant impact on stress distribution around a squareshaped holes and that the structure’s loadbearing capability can be increased by proper selection of these parameters without needing any change in material properties.
Keywords: Isotropic finite plate; Analytical solution; Complex variable method; Metaheuristic algorithms.
  
 Analytical Solutions of the FG Thick Plates with InPlane Stiffness Variation and Porous Substances Using Higher Order Shear Deformation Theory M. Karimi darani , A. Ghasemi Pages 315325 Abstract Full Text [PDF 692KB]   This paper presents the governing equations on the rectangular plate with the variation of material stiffness through their thick using higher order shear deformation theory (HSDT). The governing equations are obtained by using Hamilton's principle with regard to variation of Young's modulus in through their thick with regard sinusoidal variation of the displacement field across the thickness. In addition، the effects of the substances in FGporous plate are investigated.
Keywords: Functionally graded materials; Navier solution; Porous material; Rectangular plate.
  
 Stress Analysis in Thermosensitive Elliptical Plate with Simply Supported Edge and Impulsive Thermal Load V. Varghese , P. Bhad , L. Khalsa Pages 326337 Abstract Full Text [PDF 756KB]   The paper concerns the thermoelastic problems in a thermosensitive elliptical plate subjected to the activity of a heat source which changes its place on the plate surface with time. The solution of conductivity equation and the corresponding initial and boundary conditions is obtained by employing a new integral transform technique. In addition، the intensities of bending moments، resultant force، etc. are formulated involving the Mathieu and modified functions and their derivatives. The analytical solution for the thermal stress components is obtained in terms of resultant forces and resultant moments.
Keywords: Elliptical plate; Thermosensitive; Temperature distribution; Thermal stresses; Mathieu function; Thermal moment.
  
 Fatigue Life of Graphite Powder Mixing Electrical Discharge Machining AISI D2 Tool Steel A. AlKhazraji , S.A. Amin , S.M. Ali Pages 338353 Abstract Full Text [PDF 2538KB]   The present paper deals with the design of experimental work matrices for two groups of experiments by using Response surface methodology (RSM). The first EDM group was dealt with the use of kerosene dielectric alone، while the second was treated by adding the graphite micro powders mixing to dielectric fluid (PMEDM). The total heat flux generated and fatigue lives after EDM and PMEDM models were developed by FEM using ANSYS 15.0 software. The graphite electrodes gave a total heat flux higher than copper electrodes by (82.4 %). The use of graphite powder and both electrodes yielded more heat flux by (270.1 %) and (102.9 %) than the copper and graphite electrodes، respectively with use of kerosene dielectric alone. Using graphite electrodes and kerosene dielectric alone improved the WLT by (40.0 %) when compared with the use of copper electrodes. Whereas، using copper electrodes and the graphite powder improved the WLT by (66.7 %) compared with the use of graphite electrodes under the same machining conditions. Copper electrodes with graphite powder gave experimental fatigue safety factor higher by (30.38 %) when compared with using graphite electrodes and higher by (15.73%) and (19.77%) when compared with using the copper and graphite electrodes and kerosene dielectric alone، respectively.
Keywords: EDM; PMEDM; Graphite powder; RSM; ANOVA; FEM; AISI D2 Die Steel; WLT; Total heat flux; Fatigue life; Fatigue safety factors.
  
 Engineering Critical Assessments of Marine Pipelines with 3D Surface Cracks Considering Weld Mismatch S.M.H. Sharifi , M. Kaveh , H. Saeidi Googarchin Pages 354363 Abstract Full Text [PDF 730KB]   Offshore pipelines are usually constructed by the use of girth welds، while welds may naturally contain flaws. Currently، fracture assessment procedures such as BS 7910 are based on the stressbased methods and their responses for situations with large plastic strain is suspicious. DNVOSF101 with limited modifications proposes a strainbased procedure for such plastic loads. In this paper 3D nonlinear elasticplastic finite element analyses using the ABAQUS software are performed in order to compare existing stress and strainbased procedures beside newly strainbased method which is called CRES approach in order to improve the criteria used in current guidelines particularly at large plastic strains. It is concluded that although BS 7910 values are closer to finite element results than other methods in elastic region، but it is still conservative. In the area of large plastic strain، CRES method is very less conservative in both case of with and without internal pressure in comparison to others. The comparison of numerical simulation results with those available experimental data reveals a good agreement.
Keywords: Engineering critical assessment (ECA); Marine pipelines, Girth welds; Surface cracks; Weld mismatching; CTOD.
  
 Optimal Locations on Timoshenko Beam with PZT S/A for Suppressing 2Dof Vibration Based on LQRMOPSO M. Hasanlu , A. Bagheri Pages 364385 Abstract Full Text [PDF 1464KB]   Neutralization of external stimuli in dynamic systems has the major role in health، life، and function of the system. Today، dynamic systems are exposed to unpredicted factors. If the factors are not considered، it will lead to irreparable damages in energy consumption and manufacturing systems. Continuous systems such as beams، plates، shells، and panels that have many applications in different industries as the main body of a dynamic system are no exceptions for the damages، but paying attention to the primary design of model the automatic control against disturbances has highly met the objectives of designers and also has saved much of current costs. Beam structure has many applications in constructing blades of gas and wind turbines and robots. When it is exposed to external loads، it will have displacements in different directions. Now، it is the control approach that prevents from many vibrations by designing an automated system. In this study، a cantilever beam has been modeled by finite element and Timoshenko Theory. Using piezoelectric as sensor and actuator، it controls the beam under vibration by LQR controller. Now، in order to increase controllability of the system and reduce the costs، there are only spots of the beam where most displacement occurs. By controlling the spots and applying force on them، it has the most effect on the beam. By multiobjective particle swarm optimization or MOPSO algorithm، the best weighting matrices coefficients of LQR controller are determined due to sensor and actuator displacement or the beam vibration is controlled by doing a control loop.
Keywords: Vibration attenuation; Timoshenko beam; Optimal placement; PZT patches; LQR controller; Multi, objective particle swarm optimization.
  
 Vibration Suppression of Simply Supported Beam under a Moving Mass using OnLine Neural Network Controller S. Rezaei , M. Pourseifi Pages 386398 Abstract Full Text [PDF 859KB]   In this paper، model reference neural network structure is used as a controller for vibration suppression of the Euler–Bernoulli beam under the excitation of moving mass travelling along a vibrating path. The nondimensional equation of motion the beam acted upon by a moving mass is achieved. A Diracdelta function is used to describe the position of the moving mass along the beam and its inertial effects. Analytical solution the equation of motion is presented for simply supported boundary condition. The hybrid controller of system includes of a controller network and an identifier network. The neural networks are multilayer feed forward and trained simultaneously. The performance and robustness of the proposed controller are evaluated for various values mass ratio of the moving mass to the beam and dimensionless velocity of a moving mass on the time history of deflection. The simulations verify effectiveness and robustness of controller.
Keywords: Vibration control; Neural network controller; Euler–Bernoulli beam theory; Moving mass.
  
 Free Vibration Analysis of NonUniform Circular Nanoplate M. Zarei , M. GhalamiChoobar , G.H. Rahimi , G.R. Faghani Pages 399414 Abstract Full Text [PDF 1029KB]   In this paper، axisymmetric free vibration analysis of a circular Nanoplate having variable thickness was studied. The variation in thickness of plate was considered as a linearly in radial direction. Nonlocal elasticity theory was utilized to take into account sizedependent effects. Ritz functions was utilized to obtain the frequency equations for simply supported and clamped boundary. To verify accuracy of Ritz method، differential transform method (DTM) also used to drive the size dependent natural frequencies of circular nanoplates. The validity of solutions was performed by comparing present results with those of the literature for both classical plate and nano plate. Effect of nonlocal parameter، mode number and taper parameter on the natural frequency are investigated. Results showed that taper parameter has significant effect on the nondimensional frequency and its effects on the clamped boundary condition is more than simply support.
Keywords: Nonlocal theory; Axisymmetric vibration; Variable thickness plate; Ritz method; Differential transform method.
  
 Transversely Isotropic MagnetoVisco Thermoelastic Medium with Vacuum and without Energy Dissipation R. Kumar , P. Kaushal , R. Sharma Pages 415433 Abstract Full Text [PDF 983KB]   In the present investigation the disturbances in a homogeneous transversely isotropic magnetoVisco thermoelastic rotating medium with two temperature due to thermomechanical sources has been addressed. The thermoelasticity theories developed by GreenNaghdi (Type II and Type III) both with and without energy dissipation has been applied to the thermomechanical sources. The Laplace and Fourier transform techniques have been applied to solve the present problem. As an application، the bounding surface is subjected to concentrated and distributed sources (mechanical and thermal sources). The analytical expressions of displacement، stress components، temperature change and induced magnetic field are obtained in the transformed domain. Numerical inversion techniques have been applied to obtain the results in the physical domain. Numerical simulated results are depicted graphically to show the effect of viscosity on the resulting quantities. Some special cases of interest are also deduced from the present investigation.
Keywords: Transversely isotropic; Magneto, Visco thermoelastic; Laplace transform; Fourier transform; Concentrated and distributed sources; Rotation.
  
 Thermoelastic Fracture Parameters for Anisotropic Plates S. Kebdani , A. Sahli , S. Sahli Pages 434448 Abstract Full Text [PDF 877KB]   This paper deals with the determination of the effect of varying material properties on the value of the stress intensity factors، KI and KII، for anisotropic plates containing cracks and subjected to a temperature change. Problems involving cracks and body forces، as well as thermal loads are analysed. The quadratic isoperimetric element formulation is utilized، and SIFs may be directly obtained using the ‘traction formula’ and the ‘displacement formula’. Three cracked plate geometries are considered in this study، namely: (1) a plate with an edgecrack; (2) a plate with a double edgecrack; (3) a plate with symmetric cracks emanating from a central hole. Where appropriate، finite element method (FEM) analyses are also performed in order to validate the results of the BEM analysis. The results of this study show that، for all crack geometries، the modeI stress intensity factor، K∗I decreases as the anisotropy of the material properties is increased. Additionally، for all these cases، K∗I decreases as the angle of orientation of the material properties، ، increases with respect to the horizontal axis. The results also show that BEM is an accurate and efficient method for twodimensional thermoelastic fracture mechanics analysis of cracked anisotropic bodies.
Keywords: Boundary element method; Stress intensity factors; Anisotropy.
  
 ElasticPlastic Transition of Pressurized Functionally Graded Orthotropic Cylinder using Seth’s Transition Theory S. Sharma , R. Panchal Pages 449462 Abstract Full Text [PDF 972KB]   In this paper the radial deformation and the corresponding stresses in a functionally graded orthotropic hollow cylinder with the variation in thickness and density according to power law and rotating about its axis under pressure is investigated by using Seth's transition theory. The material of the cylinder is assumed to be nonhomogeneous and orthotropic. This theory helps to achieve better agreement between experimental and theoretical results. Results has been mentioned analytically and numerically. From the analysis، it has been concluded that cylinder made up of orthotropic material whose thickness increases radially and density decreases radially is on the safer side of the design as circumferential stresses are high for cylinder made up of isotropic material as compared to orthotropic material. This paper is based on elasticplastic behavior which plays important role in practical design of structures for safety factor.
Keywords: Elastic, plastic; Orthotropic; Pressure; Functionally graded material; Cylinder.
  
تاريخ انتشار: 5/6/97 تلفن: 34134025 (086)
تاريخ درج در سايت: 10/6/97
شمار بازديدکنندگان اين شماره: 297




