Sharif University of TechnologyScientia Iranica1026-309826220190401Experimental investigation of magnetic abrasive polishing of paramagnetic workpieces7897952041510.24200/sci.2018.20415ENS.M.SafaviDepartment of Mechanical Engineering, Isfahan University of technology, Isfahan 84156-83111, IranS.HasnvandDepartment of Mechanical Engineering, Isfahan University of technology, Isfahan 84156-83111, IranR.Jafari NedoushanDepartment of Mechanical Engineering, Isfahan University of technology, Isfahan 84156-83111, IranJournal Article20160830In the current paper application of magnetic abrasive polishing process, on paramagnetic workpieces is investigated. A magnetic disc which comprises of six magnetic coils and is electrified with three phase AC current is used to perform the experiments. In the experimental setup various parameters including; rotational speed of abrasive pins, quantity of abrasive pins, working gap, abrasive pins' dimensions and process's time can be changed. Changing this parameters surface quality is investigated. Two kinds of workpieces with different mechanical properties are examined. It is observed that both increasing the rotational speed and using smaller pins improve final surface quality but the rotational speed has a sharper effect. There are optimum abrasive pins quantity and working gap in which the best surface quality is obtained. The results are similar for the both selected materials.Sharif University of TechnologyScientia Iranica1026-309826220190401Trajectory modification of a transonic spherical projectile under hop-up mechanism7968072022410.24200/sci.2018.20224ENS.E.SalimipourDepartment of Mechanical Engineering, Faculty of Engineering, Ferdowsi University of Mashhad, Mashhad, P.O. Box 91775-1111,
Iran.A.R.TeymourtashDepartment of Mechanical Engineering, Faculty of Engineering, Ferdowsi University of Mashhad, Mashhad, P.O. Box 91775-1111,
Iran.M.MamourianDepartment of Mechanical Engineering, Faculty of Engineering, Ferdowsi University of Mashhad, Mashhad, P.O. Box 91775-1111,
Iran.Journal Article20161219<em>Improvement of shooting accuracy of air gun pellets is important in sport competitions which is questioned by shooting</em> <em>enthusiasts. Hence, the performance of a transonic spherical projectile as an air gun pellet with 4.5 mm-caliber under a mechanism known as Hop-up is numerically examined in the present study. </em><em>Hop-up mechanism is resulted in a rotational motion of spherical projectile, so a Magnus Force is generated which prevents the altitude loss of the projectile caused by its weight. </em><em>The motion of the projectile is assumed in four degrees of freedom including three </em><em>translational motions and one transverse rotational motion. The projectile confronts the continuous variations of velocity due to the influence of the aerodynamic forces so experiences an unsteady flow. In order to numerical analysis of the problem, </em><em>the 3-D compressible turbulent Navier-Stokes equations</em> <em>based on “Roe” scheme and dynamic equations of the projectile motion are solved in a coupled form as a fluid-structure interaction and in a moving computational grid. The results obtained from these studies show that the proper rotation of the projectile for a certain distance, can neutralize the altitude loss. It is also demonstrated that the momentum of the projectile is decreased by increasing its angular velocity.</em>Sharif University of TechnologyScientia Iranica1026-309826220180120Plasma based surface modification of poly (dimethylsiloxane) electrospun membrane proper fororgan-on-a-chip applications8088142014810.24200/sci.2018.20148ENA.KiyoumarsioskoueiDepartment of Mechanical Engineering, Sharif University of Technology, 11365/8639, Tehran, Iran., Dalio Institute of Cardiovascular Imaging, Department of Radiology, Weill Cornell Medicine.M.S.SaidiDepartment of Mechanical Engineering, Sharif University of Technology, 11365/8639, Tehran, Iran.H.MoghadasDepartment of Mechanical Engineering, Sharif University of Technology, 11365/8639, Tehran, Iran.B.FiroozabadiDepartment of Mechanical Engineering, Sharif University of Technology, 11365/8639, Tehran, Iran.Journal Article20170101Constructing of the scaffolds for cell culture applications has long been of interest for engineering researchers and biologist. In this study, a novel process is utilized for construction of suitable membrane with a high mechanical strength and appropriate surface behavior. Poly (dimethylsiloxane) (PDMS) is electrospun into fine fibers using poly (methyl methacrylate) (PMMA) as the carrier polymer in different weight ratios. Since the surface behavior of all PDMS substrates is moderately hydrophobic (120 < contact angle (CA) < 150), the electrospun membranes with higher PDMS ratios show slightly higher hydrophilicity. Direct plasma treatment is utilized to change the interfacial wettability of the membrane. Applying plasma changes the surface energy and renders the PDMS/PMMA substrates superhydrophilic (CASharif University of TechnologyScientia Iranica1026-309826220190401Nonlinear free vibration analysis of functionally graded plate resting on elastic foundation in thermal environment using higher order shear deformation theory8158332022710.24200/sci.2018.20227ENS.ParidaDepartment of Mechanical Engineering, NIT Rourkela, Rourkela, 769008, India.S. C.MohantyDepartment of Mechanical Engineering, NIT Rourkela, Rourkela, 769008, India.Journal Article20170424This paper deals with nonlinear vibration analysis of functionally graded plate resting on Pasternak elastic foundation in thermal environment. A mathematical model is developed based on higher-order shear deformation theory using Green-Lagrange type nonlinearity. The model includes all the nonlinear terms to obtain a general form and to present the original flexure of the plate. The material properties are considered as temperature dependent and graded along thickness direction obeying a simple power law distribution in terms of volume fraction of the constituents. The compression/traction free condition is employed to obtain the simplified model with seven parameters instead of nine parameters. The plate model has been discretized into C<sup>0</sup> eight noded quadratic elements with seven degrees of freedom per node. The governing equation of the functionally graded plate has been derived using Hamilton’s principle and is solved using direct iterative method. The present model is validated by comparing the obtained results with those published in the literature. The effects of volume fraction index, aspect ratio, thickness ratio, support conditions, elastic foundation modulus and temperature on the nonlinear frequencies of the functionally graded plates are discussed. It has been found that the intermediate material property does not necessarily give intermediate nonlinear frequencySharif University of TechnologyScientia Iranica1026-309826220190401Designing an axisymmetric aerospike nozzle based on modified MOC8348422016810.24200/sci.2018.5065.1072ENM.MasdariFaculty of New Sciences and Technologies, University of Tehran, Tehran, P.O. Box 1417614418, Iran.M.TahaniFaculty of New Sciences and Technologies, University of Tehran, Tehran, P.O. Box 1417614418, Iran.0000-0003-1852-7153F.Mohammadi FardFaculty of New Sciences and Technologies, University of Tehran, Tehran, P.O. Box 1417614418, Iran.Journal Article20170824In this study a direct method based on the method of characteristics with the assumptions of non-viscous flow and thermal perfect gas is provided to design of axisymmetric plug nozzle. Inputs for numeric code are including output Mach number, specific heat ratio, global gas constant and the number of discrete steps of Prandtl–Meyer expansion fan. In the design process, there has been no simplification and only to create unique spike geometry. Based on the criterion of locating the tip of the spike on the axis of symmetry, for each output Mach number, a correction factor has been extracted that it was the sole source of theoretical errors. Studied parameters include spike geometry, exhaust nozzle flow parallelism and uniformity. In the results by numerical analysis, consistent results with desired output Mach number and parallel of output flow with the axis of symmetry are obtained. The simple and direct formulation is used and so it performs very fast. Due to recognizing of the error resulted in the surface slope reduction factor, some movement in spike geometry relative to ideal conditions was raised so the effect of reduction factor will tend to zero by increasing of the design Mach number.Sharif University of TechnologyScientia Iranica1026-309826220190401Performance investigation into a diesel engine under effective efficiency-power-power density conditions8438552014610.24200/sci.2018.5164.1131ENG.GoncaDepartment of Naval Architecture and Marine Engineering, Yildiz Technical University, Besiktas, Istanbul, TR.0000-0001-7991-2421Y.PalaciDepartment of Naval Architecture and Marine Engineering, Yildiz Technical University, Besiktas, Istanbul, TR.Journal Article20170911A performance analysis of a Diesel engine in terms of effective power (EP), effective power density (EPD) and effective efficiency (EE) has been performed using a novel realistic finite-time thermodynamics (FTT) modeling. The effects of design and operating parameters of the diesel cycle such as bore-stroke length ratio (d/L), equivalence ratio (ER), compression ratio (CR), cycle temperature ratio (CTR), cycle pressure ratio (CPR), stroke length (L), friction coefficient (FRC), engine speed (N), mean piston speed, inlet pressure and inlet temperature on the engine performance have been investigated. In addition, the energy losses depending on incomplete combustion (IC) , friction losses (FRL), heat transfer losses (HTRL) and exhaust output losses (EOL) have been described as fuel input energy. In order to acquire reasonable results, variable specific heats with respect to temperature for working fluid have been used. The results presented could be an essential tool for Diesel engine designers.Sharif University of TechnologyScientia Iranica1026-309826220190401Chaos and bifurcation in nonlinear in-extensional rotating shafts8568682004110.24200/sci.2018.5217.1151ENS.A.A.HosseiniDepartment of Mechanical Engineering, Faculty of Engineering, Kharazmi University, Mofatteh Avenue, Tehran, P.O. Box 15719-14911, Iran.Journal Article20170919In this paper, bifurcation and chaotic behavior of in-extensional rotating shafts are investigated. The shaft is modeled as a Rayleigh simply supported beam, spinning with constant rotational speed. Using two–mode Galerkin truncation, the partial differential equations of motion are discretized and then with the aid of numerical simulations, the dynamical behavior of the rotating shaft is studied. Using tools from nonlinear dynamics, such as time history, bifurcation diagram, Poincaré map, Lyapunov exponents, and amplitude spectra, a comprehensive analysis is made to characterize the complex behavior of the rotating shaft. Periodic (synchronous), quasi-periodic, chaotic and transient chaotic responses are observed in the neighborhood of the second critical speed. The effect of rotary inertia and damping on the dynamics of the rotating shaft is considered. It is shown that the chaotic response is possible for a shaft with weak nonlinearity without the existence of any internal resonance.Sharif University of TechnologyScientia Iranica1026-309826220190401Using an optimized RBF neural network to predict the out-of-plane welding distortions based on the 3-2-1 locating scheme8698782004310.24200/sci.2018.5458.1282ENM.M.TafarrojDepartment of Mechanical Engineering, Ferdowsi University of Mashhad, Mashhad, Iran.F.KolahanDepartment of Mechanical Engineering, Ferdowsi University of Mashhad, Mashhad, Iran.Journal Article20171028This study deals with the effect of locator positioning in 3-2-1 locating scheme to control the out-of-plane distortion in gas tungsten arc welding of sheet metals. To apply this locating scheme on the sheet metals, a suitable fixture is designed. The distortion of the welded plates has been predicted using the radial basis function (RBF) neural network. To gather the experimental data employed in the RBF modeling process, a set of welding tests is performed on the sheet specimens by varying the positions of the three locators. The parameters of the network are optimally selected using the simulated annealing (SA) optimization algorithm. The average and maximum error computed for the test dataset were respectively 2.43% and 5.30% while in some cases the error falls below 1%. The results of the RBF network show very good agreement with the experiments and it can be concluded that this modeling technique can be utilized successfully in predicting the welding distortions when the 3-2-1 locating scheme is used.Sharif University of TechnologyScientia Iranica1026-309826220190401A local differential transform approach to the cubic nonlinear Duffing oscillator with damping term8798862014210.24200/sci.2018.4934.1000ENH.TuncDepartment of Mathematics, Faculty of Arts and Science, Yildiz Technical University, Istanbul 34220, Turkey.M.SariDepartment of Mathematics, Faculty of Arts and Science, Yildiz Technical University, Istanbul 34220, Turkey.0000-0003-0508-2917Journal Article20170724Nonlinear behaviour of various problems is described by the Duffing model interpreted as a forced oscillator with a spring which has restoring force. In this paper, a new numerical approximation technique based on differential transform method has been introduced for the nonlinear cubic Duffing equation with and without damping effect. Since exact solutions of the corresponding equation for all initial guesses do not exist in the literature, we have first produced an exact solution for specific parameters by using the Kudryashov method to measure the accuracy of the currently suggested method. The innovative approach has been compared with the semi-analytic differential transform method and the fourth order Runge-Kutta method. Although the semi-analytic differential transform method is valid only for small time intervals, it has been proved that the innovative approach has ability to capture nonlinear behaviour of the process even in the long-time interval. In a comparison way, it has been shown that the present technique produces more accurate and computationally more economic results than the rival methods.Sharif University of TechnologyScientia Iranica1026-309826220190401Study of swelling behavior of temperature-sensitive hydrogels considering inextensibility of network8878962016910.24200/sci.2018.5266.1181ENH.MazaheriDepartment of Mechanical Engineering, Bu-Ali Sina University, Hamedan, Iran.0000-0002-1935-4648Journal Article20170928In this work, the equilibrium swelling of temperature sensitive hydrogel networks is studied with an emphasis on the chain locking of the network. Using Gent model for elastic part of free energy and modifying the mixing part of the free energy, a continuous model is developed which consider inextensibility of the network chains and has a good agreement with the experimental data particularly for smaller values of crosslinking density of the network and larger values of the swelling ratio. After validating the modified model, it is employed for the studying the inhomogeneous swelling of a spherical shell on a hard core both analytically and numerically. The analytical solution is used for validating the numerical method. Finally, the inhomogeneous swelling of a bilayer beam with an active temperature sensitive hydrogel is investigated and the results are presented. The obtained results show the importance level of considering the chain locking in swelling of the network in the applied problems.Sharif University of TechnologyScientia Iranica1026-309826220190401Investigation on the effect of using rubber as core material in sandwich composite plate subjected to low-velocity normal and oblique impact loadings8979072004410.24200/sci.2018.5538.1331ENM.VishwasDepartment of Mechanical Engineering, National Institute of Technology Karnataka, Surathkal, Mangalore, 575025, India.0000-0002-1315-9462Sh.JoladarashiDepartment of Mechanical Engineering, National Institute of Technology Karnataka, Surathkal, Mangalore, 575025, India.S.M.KulkarniDepartment of Mechanical Engineering, National Institute of Technology Karnataka, Surathkal, Mangalore, 575025, India.Journal Article20171108In this article, the structural performance of composite plate under low velocity impact is studied. Two forms of layup sequence namely jute-epoxy laminate (JE) and jute-epoxy-rubber sandwich (JE-R-JE) are considered for evaluation. Special emphasis is provided for evaluating the influence of normal and oblique loading. The various dynamic parameters such as energy, peak load, and deformation are analysed in detail to study the effect of impact angle on both laminate and sandwich. Stress analysis of both the laminate and sandwich structure is carried out to discuss the effect of introducing rubber as a core material. The results reveal that using rubber as a core material has a significant effect on energy absorption. In addition, it is noticed that increasing the angle of impact yields better performance of the composite plate. The results presented here may serve as benchmark for the effective utilization of composite plates in low velocity impact applications.