Amirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29376220220601An Experimental Study on Fuzzy Controller Robustness Augmented by Fuzzy Supervisor for Cutting Force Control of End-Milling167178462710.22060/ajme.2021.19774.5966ENMohsenAbediFaculty of Satellite Research Institute, Iranian Space Research Center, Tehran, IranJournal Article20210328In this paper, the robustness of controlling the cutting force of an end-milling process using a supervisory fuzzy controller has been experimentally investigated. In the proposed controller an ordinary fuzzy controller is augmented by implementing a fuzzy supervisor. The ordinary fuzzy controller is the highly-used cutting force fuzzy controller due to its advantages. However, because of participating only one cutting parameter in its structure, i.e. mostly feed-rate, the ordinary fuzzy controller is suitable only when other parameters such as depth of cut, spindle speed, etc. have a small amount of variations. Since in practice this assumption is not valid, an ordinary fuzzy controller needs to be augmented. This augmentation has had suggestions in the literature. However, these suggestions never have been on the basis of the fuzzy logic; while fuzzy being is the major advantage of ordinary fuzzy controller for controlling cutting force. Due to this deficit, in this paper, a supervisory fuzzy controller has been added to the system. The designed fuzzy supervisor inspects the dynamic behavior of the cutting force, estimates a pre-defined sensitivity parameter, and cancels the output fluctuations arising from this parameter’s variation. The numerous experiments conducted in different cutting situations proved that this supervisory structure increases the robustness and applicability of the fuzzy controller with respect to an ordinary fuzzy controller. These experiments are conducted on two different computerized numerical control machines to confirm the efficiency of the presented method.https://ajme.aut.ac.ir/article_4627_0d1a9651497a38d8b1c3871c84528bd4.pdfAmirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29376220220601Comprehensive Evaluation of Human Hand Manipulability During Walking at Different Speeds179188476110.22060/ajme.2022.20391.5999ENBehnamMiripour FardFaculty of Mechanical Engineering, University of Guilan, Rasht, Iran0000-0002-2791-6591Sjoerd MBruijnDepartment of Human Movement Sciences, VU University, Amsterdam, NetherlandsAmirHajilooIndependent Scholar, Los Angeles, California, USAJournal Article20210811Using the experimental kinematic data of 11 healthy subjects, the kinematic manipulability of human hands during walking is evaluated. A total of 37 degrees of freedom mechanical model of the human body is used for this purpose. The forward kinematics and Jacobian of the model have been derived using the Denavit-Hartenberg convention. Experimental kinematics are mapped on the model using the inverse kinematic method based on optimization. The effect of walking speed on the profile and symmetry of manipulability for both right and left hands are studied. Statistical analysis showed that the walking speed can change the manipulability of hands and there is no quantitative symmetry between the manipulability of right and left hands. The results showed that there is more ability to create velocity for the hands-on horizontal plane than on other anatomical planes during walking. The results of sensitivity analysis showed the importance of the values of the hip and shoulder joints on the manipulability of the hands. The experimental manipulability profile of healthy human hands presented in this article can be used as a reference in rehabilitation to evaluate the effectiveness of physiotherapy as well as evaluation of hand function after surgery and also designing realistic motions for humanoids.https://ajme.aut.ac.ir/article_4761_0d2b2061826a5df3221116a5085a6052.pdfAmirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29376220220601Synthesis of a Six-Link Mechanism for Generating the Ankle Motion Trajectory Using Shadow Robot Control Method189200465210.22060/ajme.2021.20455.6004ENAshkanValiBiomechatronics and Cognitive Engineering Research Lab, School of Mechanical Engineering, Iran University of Science and Technology,
IranMohammad RezaHaghjooDepartment of Mechanical Engineering, Shahid Beheshti University, Tehran, Iran0000-0003-4436-8379BorhanBeigzadehBiomechatronics and Cognitive Engineering Research Lab, School of Mechanical Engineering, Iran University of Science and Technology,
Iran0000-0001-8408-5096Journal Article20210826In this paper, one degree of freedom Stephenson type III mechanism is synthesized to generate the human ankle gait trajectory by considering prescribed timing. The produced trajectory must be consistent with the natural motion of the human foot in terms of position and timing. In this regard, we used the robust and effective shadow robot algorithm that synthesizes the mechanism’s dimensions and considers prescribed timing, which is a crucial topic in gait rehabilitation devices. In this method, a mechanism with multiple fixed links is replaced by a hypothetical equivalent shadow robot with several degrees of freedom. Then, optimizing a suitable controller for the shadow robot leads to finding optimal mechanism dimensions. Afterward, the adjustability of this mechanism for generating other similar ankle gait trajectories is shown. Adjustability has been accomplished through the little change in the crank and coupler link sizes. The optimized mechanism generates ankle movement for different people with different leg lengths and has the least spatial and timing error. The reasonable error confirms the usage of the mechanism in gait rehabilitation devices.https://ajme.aut.ac.ir/article_4652_d8074a35855a7f4935e3e19222d9a9eb.pdfAmirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29376220220601Analysis of the Effect of Indenter Deformation and Presence of Voids on Silicon Nanoindentation Using Molecular Dynamics Simulation201216461310.22060/ajme.2021.20122.5990ENNafiseMahdiyarDepartment of Mechanical and Mechatronics Engineering, Shahrood University of Technology, Shahrood, IranSeyed VahidHosseiniDepartment of Mechanical and Mechatronics Engineering, Shahrood University of Technology, Shahrood, IranHadiParvazDepartment of Mechanical and Mechatronics Engineering, Shahrood University of Technology, Shahrood, Iran0000-0003-4806-7311MehdiHeidariDepartment of Mechanical and Mechatronics Engineering, Shahrood University of Technology, Shahrood, IranJournal Article20210605In the present study, a three-dimensional molecular dynamics simulation was carried out to investigate the nanoindentation of single-crystalline Silicon. The simulations were performed using the spherical shape rigid and non-rigid indenters. Subsequently, the effects of the substrate crystalline surfaces were investigated on the force-displacement curve of the indenter. The influence of the indentation force and depth were also studied on the hardness of the substrate. The findings of the simulation were then compared to the force-displacement curve published in the previous studies. The results of comparison between the rigid and non-rigid indenters revealed that the level of the force-displacement and hardness-displacement curves decrease by changing the assumption of the rigid indenter to the non-rigid one. Moreover, the effects of void presence in a silicon substrate (in various sizes at different positions) were investigated on the material hardness. According to the results, the larger the void and the closer it is to the surface of the workpiece, the more it can reduce the hardness. It was also concluded that the presence of voids in silicon substrate could reduce the hardness of the workpiece by 54%. Nevertheless, small voids near the surface may be eliminated during the nanoindentation process.https://ajme.aut.ac.ir/article_4613_eeaebbffb5d29ff62799637fc51adb7b.pdfAmirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29376220220601Effects of Shape Memory Alloys and Carbon Nanotubes on the Nonlinear Aerothermal Flutter Characteristics of Hybrid Nanocomposite Beam217228466610.22060/ajme.2022.20395.6000ENHamidrezaHeidariDepartment of Mechanical Engineering, Malayer University, Malayer, IranSajadEsmaeiliDepartment of Mechanical Engineering, Malayer University, Malayer, IranAlirezaHakimiDepartment of Mechanical Engineering, Malayer University, Malayer, IranJournal Article20210812 In this study, the effect of aerodynamic and thermal forces on the flutter stability of an epoxy / fiber-based hybrid nanocomposite beam containing shape memory alloy wires and reinforced by functionally graduated distribution of carbon nanotubes are investigated. Carbon nanotubes help to increase the stiffness of the nanocomposite beam, and the shape memory alloys will increase the flutter stability boundaries by inducing tensile stress in the beam due to the increase in temperature and the aerodynamic pressure. In this study, the Brinson model is supposed to present the properties of shape memory alloy wires, also, the Euler-Bernoulli beam model is assumed to be in line with van-Karmen nonlinear strains. The boundaries of buckling stability and aerothermodynamics flutter have been investigated by studying the natural frequencies of the hybrid nanocomposite beam and the thermal bifurcation points. The primary objective of this study is to examine the impact of carbon nanotubes and shape memory alloy wire on improving the behavior of a composite beam flutter under the effect of airflow and temperature increase, simultaneously. The results showed that applying these two advanced reinforcing materials has a significant impact on increasing the static and dynamic stabilities of hybrid nanocomposite beams in the thermo-aerodynamic environment.https://ajme.aut.ac.ir/article_4666_9f9e8cba3700df6a947a8cf91035ab84.pdfAmirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29376220220601Numerical Simulation of Blood Flow in a Stented Aneurysm Using Lattice Boltzmann Method229248476010.22060/ajme.2022.20044.5987ENMaryamAhangariDepartment of Mechanical Engineering, Golpayegan College of Engineering, Isfahan University of Technology, Golpayegan, IranMarzieRezazadeDepartment of Mechanical Engineering, Golpayegan College of Engineering, Isfahan University of Technology, Golpayegan, IranJournal Article20210515An aneurysm is a local deformation of a blood vessel caused by high pressure and wall weakness. The rupture of aneurysms leads to a cerebral hemorrhage and severe complications in the patient. Hemorrhagic stroke is one of the common causes of death by cardiovascular diseases and affects 15% of stroke patients worldwide. Recently, stent placement has been considered a promising and minimally invasive technique to prevent the rupture of an aneurysm. Hemodynamic characteristics of the blood flow are affected by the aneurysm geometry and stent properties. In this study, the effect of the stent size and strut shape on the blood flow parameters are investigated numerically. The Lattice Boltzmann Method is used in this simulation since it is convenient for modeling complex fluid flow and transport phenomena based on kinetic theory and statistic physics. The results show that with reduced pore size, speed and momentum in the aneurysm sac decrease, and stent-struts with a rectangular cross-section perform the best. Additionally, the height of the stent is more effective in reducing the blood flow than the width of the stent.https://ajme.aut.ac.ir/article_4760_e7d161ac8d8a76529d39d9f5b4249ccb.pdfAmirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29376220220601Numerical Study of Kelvin-Helmholtz Instability of Newtonian and Non-Newtonian Fluids249260464910.22060/ajme.2021.20382.5996ENReyhanehFarajzadehDepartment of Mechanical Engineering, Shahrekord University, Shahrekord, IranMortezaBayarehDepartment of Mechanical Engineering, Shahrekord University, Shahrekord, IranJournal Article20210807Kelvin-Helmholtz instability is a hydrodynamic instability generated by the relative motion of immiscible, irrotational, incompressible, and inviscid fluids. In the present study, the Kelvin-Helmholtz instability is assessed for Newtonian and non-Newtonian fluids by solving two-dimensional Navier-Stokes equations using the finite volume method. ANSYS FLUENT software is used to simulate the two-phase flow field. The numerical method is the finite volume method. Using the semi-implicit method for pressure-linked equations algorithm, the velocity and pressure fields are coupled and the Navier-Stokes equations are solved. The second-order upwind method is used to discretize the convection terms in Navier-Stokes equations and the central difference method is employed to approximate the time derivative. In the case of Newtonian fluids, it was found that for the growth rate of Kelvin-Helmholtz instability depends on the surface tension when the surface tension is in the range of 0.000192-0.000993 N/m. The results demonstrate that the critical wavenumber is enhanced by increasing the power-law index (<em>n</em>) for shear-thinning and shear-thickening non-Newtonian fluids; however, at a specific time, the amount of critical wavenumber for shear-thickening fluids is smaller than that for shear-thinning ones. It is also concluded that as the power-law index increases, the wave stability can be reached more rapidly.https://ajme.aut.ac.ir/article_4649_205c3608ecb984c1f5f5d2f52c934428.pdfAmirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29376220220601A New Metaheuristic Method with Applications to Airfoil Shape Optimization261278465010.22060/ajme.2021.20376.5998ENMasoudHeidari SoreshjaniDepartment of Aerospace Engineering, Amirkabir University of Technology, Tehran, IranAlirezaJahangirianDepartment of Aerospace Engineering, Amirkabir University of Technology, Tehran, IranJournal Article20210808This paper proposes an efficient meta-heuristic method called expert groups' optimization algorithm. The method strategy relies on four principles and starts from a random initial population. The population members are divided into two expert groups: the free group and the guided group. Each group has specific tasks for effective domain search, but with one new operator. This operator has an intelligent mechanism so that exploration and exploitation of the population can lead the members to the global optimum. The new method is validated through a standard test function. Then its performance is evaluated in the application of an inverse geometric reconstruction and the results are compared with a genetic algorithm, particle swarm optimization, and mean-variance mapping optimization. Results show that the new method outperforms the alternative methods in convergence rate and reaching the global optimum. Finally, the expert groups' optimization algorithm performance is evaluated in an engineering problem with high computational cost. In this case, the goal is drag coefficient minimization of the RAE 2822 airfoil in transonic flow at a fixed lift coefficient with constraints on the pitching moment and airfoil area. An unstructured grid Navier-Stokes flow solver with a two-equation turbulence model is used to evaluate the aerodynamic objective function. The results show that the optimal solutions obtained by the new method outperform those of mean-variance mapping optimization with considerably faster convergence.https://ajme.aut.ac.ir/article_4650_d19544ae709580379cd2523b0e72c86d.pdfAmirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29376220220601Numerical and Thermodynamic Study of a Gas Turbine Cycle with Evaporative Cooling279292471610.22060/ajme.2022.19980.5978ENGhodratGhassabiDepartment of Mechanical Engineering, Bozorgmehr University of Qaenat, Qaen, IranSeyyed EhsanShakibDepartment of Mechanical Engineering, Bozorgmehr University of Qaenat, Qaen, IranMohammadEbadianDepartment of Mechanical Engineering, Bozorgmehr University of Qaenat, Qaen, IranJournal Article20210501It has been demonstrated that thermal efficiency can be improved and Nox emission can be reduced in gas turbine cycles by inlet air evaporative cooling. For this method, few studies have been performed using numerical simulations due to the complexity of the combustion and evaporation process. This study numerically and thermodynamically investigated the effect of inlet evaporative cooling on the thermal efficiency and NOx emission of a V94.2 gas turbine. The compressor and turbine are simulated using thermodynamic modeling. However, thermodynamic modeling could be able to calculate the temperature only at the inlet and outlet of devices. Analysis of evaporating cooling effect on combustion chamber temperature distributions and species distribution could be achieved by numerical method. Therefore, the combustion chamber was simulated by numerical modeling using Ansys Fluent 16. The process was simulated at four humidity ratios, including, 0, 25%, 50%, and 75%. Combustion was assumed to occur in a diffusion-type flame. The mass flow rate of fuel and air was 3.64 kg/s and 214.2 kg/s, respectively. Results show that Numerical and thermodynamic solutions have a good agreement with the empirical result. Also, it is observed that the accuracy of the numerical solution is better than the thermodynamic solution. Results indicated a 0.44% improvement in thermal efficiency and a considerable 33.5% reduction of NOx emission at the highest humidity ratio.https://ajme.aut.ac.ir/article_4716_bc5fcb0018cecacba559dc512740091b.pdfAmirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29376220220601Combined Action of Gas Radiation and Airfoil Shaped Ribs in Improvement of Solar Heater Performance293312464610.22060/ajme.2021.20440.6003ENS. A.Gandjalikhan NassabDepartment of Mechanical Engineering, Shahid Bahonar University of Kerman, Kerman, IranJournal Article20210821A novel design of solar air heater is proposed in this paper based on the simultaneous exploitation of radiating gas and also airfoil-shaped ribs. Using participating gases with high radiative characteristics concerning the usual working gas, namely air, could show a more promising improvement in thermal performance, especially while this technique is combined with extending surface area. This new concept is demonstrated by simultaneous solution of the radiative transfer equation considering both the diffuse and collimated beams coupled with momentum, energy, and continuity equations. The set of governing equations are solved using the finite element method in a steady-state condition by the COMSOL Multi-physics. The well-known model is used in calculations of turbulent stress and heat flux in numerical simulation. Through the presented results, radiative gas proved its full potential to serve as a future working gas in solar gas heaters. Its combination with the airfoil-shaped ribs shows magnificent 88% thermal efficiency and gas outlet temperature up to 85°C in the test cases. The contributions of airfoil-shaped ribs and also the gas radiation to increase thermal performance are computed equal to 7% and 66%, respectively.https://ajme.aut.ac.ir/article_4646_50f3f8c42b998a48057e9d33f4144b8b.pdf