Amirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29372220181201A Simplified Description of the Uniaxial Tensile Test Used for Calibrating Constitutive Models of Orthotropic Porous Sheet Metals127136294710.22060/ajme.2018.13862.5693ENA.KamiMechanical Engineering Department, Semnan University, Semnan, IranD.-S.ComsaCERTETA Research Centre, Technical University of Cluj-Napoca, Cluj-Napoca, RomaniaJournal Article20171223In the present work, a simplified model of the uniaxial tensile test is developed for orthotropic metallic sheets. This model is mainly established for tensile test analysis and calibration of material parameters. The constitutive equations included in the model are based on an anisotropic Gurson-Tvergaard-Needleman model combined with the Hill 1948 quadratic yield criterion. At first, a detailed description of the constitutive equations along with their computer implementation is presented. Then, by comparing the force and void evolution diagrams predicted by the model with numerical and experimental results the efficiency and accuracy of the model are assessed. Finally, the effect of different parameters on the traction force and evolution of voids during uniaxial tensile tests are studied. The material parameters used in the calibration procedure are as follows: initial void volume fraction, two adjusting parameters, nucleation of void volume fraction, standard deviation, mean value of void nucleation strain, and sample orientation with respect to the rolling direction. The tests performed by the authors prove the capability of the simplified model to describe accurately the mechanical response of orthotropic sheet metals.Amirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29372220181201Experimental and Numerical Study on the Accuracy Residual Stress Measurement by Incremental Ring-Core Method137148295710.22060/ajme.2018.13954.5697ENM. A.MoazamFaculty of Mechanical Engineering, University of Kashan, Kashan, IranM.HonarpishehFaculty of Mechanical Engineering, University of Kashan, Kashan, IranJournal Article20180113In this study, the calibration constants of incremental step method have been determined by finite element analysis to calculate the residual stresses by the ring-core method. The calibration coefficients have been determined by simulation the uniaxial and biaxial loading. It is indicated that the loading approach has not effect on the calibration constants and they are unique. The uniaxial condition has been used to determine the calibration coefficients in the experimental method. To verify the determined constants, the calibration factors have been used to calculate the residual stresses in the case of uniform and non-uniform residual stresses. The axial and biaxial conditions have been studied and the results are in good accordance with applied stresses in simulations. In the uniaxial loading the measured residual stresses in finite element model completely accommodated by the applied stresses and presented formula and calibration constants determined the direction of the maximum principal stress by clearance less than 0.7%. Clearance of the measures stresses and applied stresses in the non-uniform case was about 1 %. An experimental test has been used to show the effectiveness of the obtained calibration coefficient by finite element analysis. Also, it is indicated that the results of the experimental test are satisfactory.Amirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29372220181201Experimental Investigations of Static and Fatigue Crack Growth in Sandwich Structures with Foam Core and Fiber-Metal Laminates Face Sheets149164295610.22060/ajme.2018.14222.5714ENF.MazaheriDepartment of Aerospace Engineering, Amirkabir University of Technology, Tehran, IranH.Hosseini-ToudeshkyDepartment of Aerospace Engineering, Amirkabir University of Technology, Tehran, IranJournal Article20180319Debonding of face-core interface is the most important damage mechanisms which make loss of structural integrity in sandwich structures. In this paper, mode-I and mode-II fracture of face-core interface in sandwich structures have been investigated under both static and fatigue loadings. The considered sandwich structures contain of different face sheet fiber-metal laminates and the core material is polyvinyl chloride foam. Several specimens are fabricated and the experiments are carried out to find the effects of initial debonding location and various fiber-metal laminate face sheets on the fracture toughness under static and fatigue loadings. Double cantilever beam specimens are used for mode-I and end notch flexure specimens for mode-II loading conditions. The resistance strength curves are plotted for mode-I and mode-II under static loading to find the instability point which is the border of stable and unstable crack growth and determine the critical crack length too. The strain energy release rates of mode-I and mode-II are also obtained for fatigue loading to investigate the resistance against damage evolution. Also, the global damage parameter is defined for both static and fatigue loading which is the combination of all damage mechanisms occurred in sandwich structures. Finally, the more efficient layup configurations under static and fatigue loadings among the investigated layups are introduced in mode-I and mode-II fracture conditions separately.Amirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29372220181201Pertinence of Sheep Knee Joint for Calibration of Ligaments’ Constitutive Equations; Experimental and Theoretical Study165176288810.22060/ajme.2018.13821.5322ENM.AsgariFaculty of Mechanical Engineering, K. N. Toosi University of Technology, Tehran, IranB.RashediFaculty of Mechanical Engineering, K. N. Toosi University of Technology, Tehran, IranJournal Article20171209The knee joint is one of the most complex joints in human body because of its complex geometry and articulations. On the other hand, due to many practical constraints for studying the anatomy and biomechanics of the human knee, in vivo and in vitro animal models have been widely used. Based on this fact, an objective comparison of the sheep samples especially from mechanical behavior point of view is needed. Therefore, a purpose of the present study is to evaluate priority of usage of sheep specimens via comparing the biomechanical differences of normal ligaments between sheep and human. To this end, some experimental tensile tests have been done on the different knee ligaments of sheep including hyperelastic behavior of the anterior cruciate ligament, medial collateral ligament, posterior cruciate ligament, and lateral collateral ligament. So, an objective comparison of the sheep and human samples has been done. Furthermore, the magnitude of material constants of different hyperelastic constitutive equations including 3rd order Ogden, Yeoh and Fung–Demiray models, as well as the maximum experienced stress by the knee ligaments have been considered.Amirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29372220181201Surface Stress Effect on Nonlinear Instability of Imperfect Piezoelectric Nanoshells under Combination of Hydrostatic Pressure and Lateral Electric Field177190278810.22060/ajme.2018.13624.5687ENS.SahmaniDepartment of Mechanical Engineering, Amirkabir University of Technology, Tehran, IranM.Mohammadi AghdamDepartment of Bioresource Engineering, McGill University, Ste-Anne-de-Bellevue, Island of Montreal, CanadaA.AkbarzadehDepartment of Mechanical Engineering, McGill University, Montreal, CanadaJournal Article20171106In this paper, the nonlinear instability of piezoelectric cylindrical nanoshells under the combined radial compression and electrical load including the effects of surface free energy is studied. To consider the surface effects, the Gurtin-Murdoch elasticity theory is utilized along with the classical shell theory to develop an efficient size-dependent shell model. To satisfy the balance conditions on the surfaces of nanoshells, a linear variation of normal stress is assumed through the thickness of the bulk. Electrical field is also exerted along the transverse direction. Based on the virtual work principle, the size-dependent nonlinear governing differential equations are derived in which transverse displacement and Airy stress function are considered as independent variables. After that, a boundary layer theory is used incorporating the surface free energy effects in conjunction with the nonlinear prebuckling deformation, the large deflections in the postbuckling regime, and the initial geometrical imperfection. Finally, a two-stepped singular perturbation technique is employed to obtain the size-dependent critical buckling pressure and the associated postbuckling equilibrium path for alternative electrical loadings. It is revealed that the electrical load increases or decreases the critical buckling pressure and critical end-shortening of nanoshell which depends on the sign of applied voltage. Moreover, it is found that by taking surface free energy effects into account, the influence of electrical load on the postbuckling behavior of nanoshell increases.Amirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29372220181201Nonlinear Free Vibration of Buckled Size-Dependent Functionally Graded Nanobeams Using Homotopy Perturbation Method191206278710.22060/ajme.2018.13562.5669ENS.ZiaeeDepartment of Mechanical Engineering, College of Engineering, Yasouj University, Yasouj, IranS. A.MohammadiDepartment of Mathematics, College of Sciences, Yasouj University, Yasouj, IranJournal Article20171017The present study aims at investigating nonlinear free vibration of thermally buckled functionally graded nanobeam. The nonlocal nonlinear Euler-Bernoulli beam theory as well as linear eigenmodes of a functionally graded nanobeam vibrating around the first buckling configuration are employed to derive a system of ordinary differential equations via the Galerkin method. Semi-analytical solutions are obtained based on both the homotopy perturbation method and the variational iteration method. Results show that the difference between nonlinear and linear frequencies increases with a rise in the maximum lateral initial deflection, small scale parameter value, and index of the power law. Investigating the effect of the ratio of length to thickness on the variance between the nonlinear and linear frequencies shows that the aspect ratio makes no difference on the classical ratio of nonlinear to linear frequencies although the difference between the nonlocal nonlinear and linear frequencies decreases with a rise in the aspect ratio. In contrast to the ratio of the first nonlinear frequency to the first linear one which will decrease if compressive axial load increases, the values of the compressive axial load which are beyond the load bearing capacity of the functionally graded nanobeam do not affect the ratio of the second nonlinear to linear frequencies.Amirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29372220181201Fault Analysis of Complex Systems via Dynamic Bayesian Network207216289010.22060/ajme.2018.13711.5692ENM. A.FarsiAerospace Research Institute, Ministry of science, research and technology, Tehran, IranJournal Article20171114<span class="A4"><span>Nowadays, several components and systems are designed and produced based on reliability. Since the reliability criterion has an important role in purchasing and implementation of these systems. In the design of a reliable system, fault and failure analysis must be carried out in order to reduce fault probability of the system. When dependency and the relation between components of a complex system are important and should be mentioned, determination of system reliability is very difficult. In this paper, dynamic fault tree is used to evaluate the systems reliability that their behavior is varied with time. Dynamic fault tree is constructed and then it converted to dynamic bayesian network. In this paper, the principle of dynamic fault tree gates and their mapping into dynamic bayesian are explained and some new relations between events and gates for this mapping are proposed. GeNIe package is used to determine dynamic bayesian network based on stochastic sampling algorithms. Four systems (cardiac assist system, hypothetical cascaded priority-and system, inertial navigation system/ global positioning system integrated, and emergency detection system) are investigated; reliability and fault probability of these systems are calculated. Comparison of the results with those obtained by other researches shows the proposed method effectiveness for systems reliability modeling and assessment via dynamic bayesian network. </span></span>Amirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29372220181201Nonlinear Aerothermoelastic Analysis of Functionally Graded Rectangular Plates Subjected to Hypersonic Airflow Loadings217232278610.22060/ajme.2018.12712.5407ENV.KhalafiAerospace Research Institute, Tehran, IranH.ShahverdiDepartment of Aerospace Engineering, Amirkabir University of Technology, Tehran, IranS.NooriDepartment of Mechanical Engineering, Amirkabir University of Technology, Tehran, IranJournal Article20170403<span class="A6"><span>In this study, the aerothermoelastic behavior of functionally graded plates under hypersonic airflow is investigated. The classical plate theory based on both mid-surface and the neutral surface position is used to model the structural treatment. Also, Von Karman strain-displacement relations are utilized to involve the structural nonlinearity. To consider the applied hypersonic aerodynamic loads, nonlinear (third-order) piston theory is employed to model unsteady aerodynamic pressure in hypersonic flow regime. Material properties of the functionally graded panel is assumed to be temperature dependent and altered in the thickness direction according to a simple power law distribution. The generalized differential quadrature method is used to transfer the governing partial differential equation into an ordinary differential equation. The onset of flutter instability, the stability boundaries, and the time response analysis of a functionally graded plate are determined by applying the fourth order Runge-Kutta method. Moreover, the effect of some important parameters such as Mach number, in-plane thermal load, plate thickness ratio, and volume fraction index on the plate aerothermoelastic behavior is examined. Comparison of the obtained results with the available results in the literature confirms the accuracy and reliability of the proposed approach to analyzing aerothermoelastic behavior of functionally graded plates in hypersonic flow. </span></span>Amirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29372220181201Nonlinear Free Transverse Vibration Analysis of Beams Using Variational Iteration Method233242276110.22060/mej.2017.12332.5315ENK.TorabiDepartment of Mechanical Engineering, Faculty of Engineering, University of Isfahan, Isfahan, IranD.SharifiDepartment of Mechanical Engineering, University of Kashan, Kashan, IranM.GhassabiDepartment of Mechanical Engineering, Iran University of Science & Technology, Tehran, IranA.MohebbiDepartment of Mechanical Engineering, University of Kashan, Kashan, IranJournal Article20170103<span>In this study, Variational Iteration Method is employed so as to investigate the linear and non-linear transverse vibration of Euler-Bernoulli beams. This method is a very powerful approach with a high convergence speed providing an analytical and semi-analytical solution to the linear equations and is able to be extended to present semi-analytical solution to the non-linear ones. In this method, firstly, Lagrange`s multiplier and Initial Function should be chosen. The suitable choice of these two elements would effectively affect the convergence speed. In this attempt, in addition to presenting a discussion on how to choose these two functions appropriately, the calculated frequencies in the non-linear state are compared with the available results in the literature, and the accuracy and convergence speed are studied, as well. </span>Amirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29372220181201Determining a Suitable Location for Wind Turbines Using Inverse Solution and Mast Data in a Mountainous Terrain243252295410.22060/ajme.2018.13813.5319ENA.H.ZAREDepartment of Mechanical Engineering, Tafresh University, Tafresh, IranR.MehdipourDepartment of Mechanical Engineering, Tafresh University, Tafresh, IranE.MohammadiDepartment of Mechanical Engineering, Tafresh University, Tafresh, IranJournal Article20171207<span>Optimum design of a wind farm will ensure high output rated power and low operating costs. The aim of this study was to determine the optimum location to install a wind turbine in a mountainous terrain using computational fluid dynamics. This purpose is achieved by employing inverse method, with the objective of maximizing the efficiency of the turbines while minimizing loss expenses caused by placing them in a less optimum region. Boundary conditions are determined by steepest decent optimization method. 2-D mountain geometry alongside the mast data installed on the flat area are the references of evaluating the performance of the proposed method in this paper. Results indicated that in current turbulent flow, separation occurs in atmospheric boundary layer due to an adverse pressure gradient. Furthermore resultant pressure contours demonstrated that air flow pressure decreases over the hill and its minimum value is reported at the top of the hill, thus adverse pressure gradient happens in the back hill. Simulation results revealed a considerable difference among the power outputs of the same turbine installed at different points of the domain. Turbine performance in the initial installation point and in the point derived from the algorithm is then compared. The performance reported is nineteen times better in the new suggested location. </span>Amirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29372220181201Thermodynamic Analysis and Feasibility Study of Internal Combustion Engine Waste Heat Recovery to Run its Refrigeration System253262288910.22060/ajme.2018.13885.5694ENT.GhorbaniDepartment of Mechanical Engineering, Mechanical Engineering Faculty, University of Tabriz, Tabriz, IranM.YariDepartment of Mechanical Engineering, Mechanical Engineering Faculty, University of Tabriz, Tabriz, IranF.MohammadkhaniDepartment of Mechanical Engineering, Mechanical Engineering Faculty, University of Tabriz, Tabriz, Iran0000-0003-3399-3099Journal Article20171231<span>Automobiles refrigeration systems are mainly vapor compression refrigeration systems, and they use high power which is taken directly from the engine. The use of these systems will increase fuel consumption, and this fuel consumption will increase up to 15%. By considering the importance of fuel saving, optimum use of fuel will be necessary. One of the effective ways, is the waste heat recovery from the engine exhaust gas. The purpose of this study is the thermodynamic analysis of a new cogeneration system based on internal combustion engine. In fact, the system will generate power using heat recovery from exhaust the engine, and then the power will be used to run the refrigeration system. The system is used in the actual operating modes of gasoline and diesel engines. Different refrigerants are used in the system. Results show that the system can generate required refrigeration capacities of both automobiles and buses. Furthermore, additional refrigeration capacities will also be available. R245fa and R600 refrigerants have better performances in the system. Maximum refrigeration capacity generated by the system is 20 kW when using gasoline engine exhaust gases waste heat recovery, and 130 kW when using diesel engine exhaust gases waste heat recovery.</span>Amirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29372220181201Estimation of Waste Heat from Exhaust Gases of an Iron Ore Pelletizing Plant in Iran263276300310.22060/ajme.2018.14151.5707ENS.GoodarziDepartment of Energy, Institute of Science and High Technology and Environmental Sciences, Graduate University of Advanced Technology, Kerman, IranE.Jahanshahi JavaranDepartment of Energy, Institute of Science and High Technology and Environmental Sciences, Graduate University of Advanced Technology, Kerman, IranM.RahnamaMechanical Engineering Department, Faculty of Engineering, Shahid Bahonar University of Kerman, Kerman, IranM.AhmadiGolgohar Iron Ore and Steel Research Institute, Golgohar Mining and Industrial Company, Sirjan, IranJournal Article20180301Waste heat from the exhaust gases of Golgohar iron ore pelletizing Plant, in Sirjan, Iran, was studied using energy analysis based on input data extracted from measurements in a 5-month period. Constituents considered as inputs were fresh air, natural gas, green and indurated pellets, while the exhaust flue gas and hot indurated pellets were served as the output. Contribution of each part to energy production and/or consumption was separately determined, in addition to the energy produced from burning of natural gas and pyrite and magnetite oxidation to hematite. Special consideration was devoted to the energy leaving the furnace through exhaust flue gases as the main source of waste heat in addition to the latent heat of water vapor, the energy stored in materials such as indurated pellets, rail pallets and cooling water, and radiation from the furnace body. It was observed that the dominant portion of waste heat is in the form of thermal energy carried by flue gases generated from combustion which are released into the atmosphere. The present study can be considered as a case study for a specific plant which gives insights on how to handle and analysis the waste heat recovery of such plans in general.Amirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29372220181201Modeling and Analysis of a Hybrid Photovoltaic-Thermoelectric Solar Cavity-Receiver Power Generator277288298310.22060/ajme.2018.14018.5698ENO.Farhangian MarandiDepartment of Mechanical & Energy Engineering, Shahid Beheshti University, Tehran, IranM.AmeriDepartment of Mechanical & Energy Engineering, Shahid Beheshti University, Tehran, Iran0000-0001-5368-5443B.AdelshahianDepartment of Mechanical & Energy Engineering, Shahid Beheshti University, Tehran, IranJournal Article20180128In the present paper, a cavity configuration for the hybrid photovoltaic-thermoelectric generator is proposed and investigated theoretically. The cubical cavity-receiver is packed with five photovoltaic modules and four thermoelectric generator modules which are stacked at the backside of each photovoltaic module. The solution algorithm using the equations of heat transfer and generated power of photovoltaic and thermoelectric generator modules is developed via MATLAB and simulated under various irradiation levels. It is shown that under 1000 W/m2 irradiation, the hybrid system can produce 536 mW which is 2.4 times the photovoltaic-thermoelectric generator alone. After modeling the system with fully open aperture, the cavity with a small aperture modeled to investigate the opening size effect on the hybrid system under non-concentrating irradiation. The results show the efficiency improvement of 27% by applying small aperture in the opening of the cavity. Although the efficiency is increased by decreasing the aperture size, the total generated power for the wide aperture is larger than the generated power in the cavity with a smaller aperture due to more radiation absorption. By balancing between minimum re-radiation loss and maximum irradiation absorption for the cubic cavity, one can conclude that the optimum aperture opening area is 42.7% of cavity surface area.