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Publication Stability Analysis of Fluid Conveying Axially Functionally Graded Micro-Pipes Using a Refined Tube Model(SPRINGER HEIDELBERG, 2022) Aghazadeh, Reza; Aghazadeh, Reza; Turk Hava Kurumu University; Turkish Aeronautical AssociationThe aim of the current study is to put forward a new model for stability analysis of axially functionally graded micro-pipes conveying fluid. Modified couple stress theory is employed to capture the scale effects. The displacement field is presented in a unified form such that the formulations based on conventional Euler-Bernoulli and Timoshenko theories as well as newly developed higher order shear deformable tube model which properly satisfies transverse shear requirements on free surfaces, are retrievable. The material properties are assumed to be varying through-the-length according to a power-law function. Hamilton's principle is utilized to derive formulation governing the current fluid-solid interaction problem. In order to generate numerical results, the system of equations is discretized and converted to the standard generalized eigenvalue problem by utilizing differential quadrature technique. The influences of size which is captured by length scale parameter of modified couple stress theory, material distribution pattern, geometrical aspects, and fluid velocity upon the stability of axially functionally graded micro-pipes conveying fluid have been elucidated through detailed numerical investigations. Developed procedures also enable determination of the value of critical flow velocity, which is a significant parameter in designing small-scale pipes containing internal flow.Publication The Effects of Gravity and Material Gradation on the Stability of Axially Functionally Graded Cantilevered Pipes Conveying Fluid(CHINESE SOC MECHANICAL ENGINEERS, 2022) Aghazadeh, Reza; Aghazadeh, Reza; Turkish Aeronautical Association; Turk Hava Kurumu UniversityThis study deals with the dynamic problem of axially functionally graded (AFG) fluid conveying cantilevered pipes (FCCPs) aiming at improving stability of such fluid structure interaction systems. The model presented in the current paper also involves the effects of gravity. All material properties of the pipe assumed to be power-law functions of axial coordinate by incorporating a gradient index parameter. By choosing an appropriate value of gradient index different material distribution profiles such as homogeneous, linear, and nonlinear can be achieved. The model, comprised of equation of motion and boundary conditions, is solved by adopting Galerkin method. The influences of gravity, which is related to the mounting orientation of the pipe, longitudinal phase distribution profile, and flow velocity upon dynamics and stability of AFG-FCCPs are discussed in detail through generated numerical results. A special focus is also devoted to determination of critical flow velocity at which the instability occurs.Publication Torsional dynamics of bi-directional functionally graded small-scale tubes possessing a variable length scale parameter(TAYLOR & FRANCIS INC, 2022) Aghazadeh, Reza; Aghazadeh, Reza; Turkish Aeronautical Association; Turk Hava Kurumu UniversityThe aim of the current study is to investigate torsional vibrations of bi-directional functionally graded (FG) small-scale tubes. The size effect is captured using the modified couple stress theory (MCST). Through-the-thickness distribution profile of material properties are characterized by employing a power-law function, which incorporates a gradation index,beta, and longitudinal varation in material properties is featured by an exponential function which employs a gradient parameter,alpha. Similar to other material properties, continuous spatial variation of the length scale parameter is also incorporated into the analysis of two-dimensionally FG tubes. The model, including governing equations of motion and boundary conditions, is developed through the utilization of Hamilton's principle. By employing differential quadrature method (DQM) numerical results regarding torsional vibrations are provided. Accuracy of the proposed model and procedures are verified through verification comparisons made to limiting cases available in the literature. Numerical results reveal effects of various material and geometric parameters on natural frequencies and indicate that torsional free vibration characteristics of small-sized tubes are sensitive to distribution profile of constituents, geometric aspect ratios and effective length scale parameter. Results also demonstrate that length scale parameter variation has significant influence on natural frequencies which justifies the necessity of its consideration in analyses.Publication Tracking free surface and estimating sloshing force using image processing(ELSEVIER SCIENCE INC, 2017) Tosun, Ufuk; Aghazadeh, Reza; Sert, Cuneyt; Ozer, Mehmet Bulent; Aghazadeh, Reza; TOBB Ekonomi ve Teknoloji University; Middle East Technical University; Turkish Aeronautical Association; Turk Hava Kurumu UniversityUltrasonic level sensors are commonly used to measure the motion of the free surface in fluid sloshing. They are used to measure the elevation of the free surface at a single point. The sloshing forces are generally measured with load sensors, which require two sets of measurements, with and without the fluid in the tank. This paper develops a method, which tracks the free surface motion during sloshing with a camera and uses the captured images to estimate the forces due to sloshing in a rectangular tank. One of the major assumptions is that the displacement input which causes sloshing is one dimensional and the resulting sloshing motion is two dimensional. For the method to correctly estimate the sloshing forces along the displacement input direction, sloshing should be around the resonant sloshing frequency. This new method can track the motion of the complete free surface rather than a single point. It estimates the sloshing forces using image processing and potential flow theory, without the need for a load cell measurement. Free surface shapes and sloshing force estimates obtained by image processing are compared with those measured by the sensors. Good agreement is observed for low amplitude sloshing around fundamental resonance frequency. (C) 2017 Elsevier Inc. All rights reserved.Publication Thermal effect on bending, buckling and free vibration of functionally graded rectangular micro-plates possessing a variable length scale parameter(SPRINGER HEIDELBERG, 2018) Aghazadeh, Reza; Dag, Serkan; Cigeroglu, Ender; Aghazadeh, Reza; Middle East Technical University; Turk Hava Kurumu University; Turkish Aeronautical AssociationModified couple stress based model is presented to investigate statics, dynamics and stability of functionally graded micro-plates subjected to mechanical and thermal loadings. The features of FGM micro-plate including length scale parameter of modified couple stress theory assumed to be graded across the thickness by varying volume fractions of constituents. The governing equations of motion and boundary conditions are derived by means of Hamilton's principle. Displacement field is expressed in a unified way capable of producing results on the base of Kirchhoff, Mindlin, and third order shear deformation theories. The system of equations is solved numerically by implementing differential quadrature method. Verification studies are carried out by comparing the results of special cases to those available in the literature. Further numerical results regarding static thermal bending, natural frequencies and critical buckling loads of micro-plates undergoing uniform temperature change are provided. Presented numerical results clearly illustrate size effect at micro-scale, impact of length scale parameter variations and influence of initial thermal displacements and stresses upon mechanical behavior of functionally graded rectangular micro-plates.Publication Modelling of graded rectangular micro-plates with variable length scale parameters(TECHNO-PRESS, 2018) Aghazadeh, Reza; Dag, Serkan; Cigeroglu, Ender; Aghazadeh, Reza; Middle East Technical University; Turkish Aeronautical Association; Turk Hava Kurumu UniversityThis article presents strain gradient elasticity-based procedures for static bending, free vibration and buckling analyses of functionally graded rectangular micro-plates. The developed method allows consideration of smooth spatial variations of length scale parameters of strain gradient elasticity. Governing partial differential equations and boundary conditions are derived by following the variational approach and applying Hamilton's principle. Displacement field is expressed in a unified way to produce numerical results in accordance with Kirchhoff, Mindlin, and third order shear deformation theories. All material properties, including the length scale parameters, are assumed to be functions of the plate thickness coordinate in the derivations. Developed equations are solved numerically by means of differential quadrature method. Proposed procedures are verified through comparisons made to the results available in the literature for certain limiting cases. Further numerical results are provided to illustrate the effects of material and geometric parameters on bending, free vibrations, and buckling. The results generated by Kirchhoff and third order shear deformation theories are in very good agreement, whereas Mindlin plate theory slightly overestimates static deflection and underestimates natural frequency. A rise in the length scale parameter ratio, which identifies the degree of spatial variations, leads to a drop in dimensionless maximum deflection, and increases in dimensionless vibration frequency and buckling load. Size effect is shown to play a more significant role as the plate thickness becomes smaller compared to the length scale parameter. Numerical results indicate that consideration of length scale parameter variation is required for accurate modelling of graded rectangular micro-plates.Publication Material gradation effects on twisting statics of bi-directional functionally graded micro-tubes(AIP Publishing, 2024-02-01) Reza Aghazadeh; Mohammad Rafighi; Raman Kumar; Mohammed Al Awadh; Aghazadeh, RezaThis study aims to characterize the twisting behavior of bi-directional functionally graded (FG) micro-tubes under torsional loads within the modified couple stress theory framework. The two material properties involved in the torsional static model of FG small-scale tubes, i.e., shear modulus and material length scale parameter, are assumed to possess smooth spatial variations in both radial and axial directions. Through the utilization of Hamilton’s principle, the governing equations and boundary conditions are derived, and then, the system of partial differential equations is numerically solved by using the differential quadrature method. A verification study is conducted by comparing limiting cases with the analytical results available in the literature to check the validity of the developed procedures. A detailed study is carried out on the influences of the phase distribution profile and geometric parameters upon twist angles and shear stresses developed in FG micro-tubes undergoing external distributed torques.