@article { author = {Kosarineia, A.}, title = {Thermal Analysis Circular Couette Flow of Non-Newtonian Fluid with Viscous Dissipation}, journal = {AUT Journal of Mechanical Engineering}, volume = {2}, number = {1}, pages = {3-12}, year = {2018}, publisher = {Amirkabir University of Technology}, issn = {2588-2937}, eissn = {2588-2945}, doi = {10.22060/mej.2017.12675.5394}, abstract = {The forced convection heat transfer in the circular couette flow of Non-Newtonian fluid is investigated when the inner cylinder is rotated at angular speed and the outer cylinder is fixed. The fluid viscosity is considered concurrently to be dependent on the temperature and shear rate. The temperature dependency of viscosity is modeled exponentially according to the Nahme law and dependence of viscosity on shear is modeled with the Carreau equation. The Viscous dissipation term is adding intricacy to the already highly interdependent set of governing motion and energy equations. The highly nonlinear governing equations are derived for the steady state base flow in the narrow gap limit. The perturbation method has been applied to obtain an approximate solution for these equations. The effect of governing parameter such as Brinkman numbers and Deborah number on the thermal stability is examined. In addition, the analysis illustrated that the Nusselt number of the outer cylinder increases as the Deborah number increases. It, although, decreases by increasing Brinkman number. The pseudoplastic fluid between concentric cylinders is heated as Brinkman number and increases due to frictional loss and it is cooled as Deborah number increases due to the fluid elasticity behavior.}, keywords = {Circular couette flow,forced convection,Friction loss,Deborah number,Perturbation method}, url = {https://ajme.aut.ac.ir/article_2760.html}, eprint = {https://ajme.aut.ac.ir/article_2760_bc10910d72bf7ea482f69bbeb34e2eff.pdf} } @article { author = {jafari, S. and afari, S. and Rahnama, M.}, title = {Simulation of Natural Convection in Eccentric Annulus: A Combined Lattice Boltzmann and Smoothed Profile Approach}, journal = {AUT Journal of Mechanical Engineering}, volume = {2}, number = {1}, pages = {13-26}, year = {2018}, publisher = {Amirkabir University of Technology}, issn = {2588-2937}, eissn = {2588-2945}, doi = {10.22060/mej.2017.13013.5500}, abstract = { In the present study, a hybrid method of thermal lattice Boltzmann and smoothed profile methods have been applied to simulate free convection in an eccentric annulus with a constant temperature wall. Smoothed profile method employs an Eulerian approach to consider the fluid-solid interaction without using an extra mesh for capturing solid boundary. As a result of this property, the combination of this method and Lattive Boltzmann method can be considered as an efficient method to simulate free convection in complex geometries like annulus. In order to investigate the effect of inner cylinder position on the natural convection, the inner cylinder was placed in different horizontal, vertical and diagonal positions. Influences of the Rayleigh number (103 ≤ Ra ≤ 105), eccentricity (-0.75 ≤ e ≤ 0.75)) and the radial ratio (Ro /Ri=2, 2.6 and 3.2) on the streamlines, isotherms and Nusselt number were studied. It was found that the Nusselt number has a positive relationship with Rayleigh number and radial ratio. Also, it can be confirmed that Nusselt number in the case with the negative eccentricity (e=−0.75) was larger than the others. It was found that a very good agreement exists between the present results and those from the open literature.}, keywords = {Lattice Boltzmann method,Natural convection,Smoothed profile method,Annulus}, url = {https://ajme.aut.ac.ir/article_2740.html}, eprint = {https://ajme.aut.ac.ir/article_2740_3e336b2340d4e3915b6eda13ae89939a.pdf} } @article { author = {Mousavi Kolousforoushi, S. F. and Mahmoudimehr, J.}, title = {Influence of Burner Head Design on Its Thermal and Environmental Characteristics}, journal = {AUT Journal of Mechanical Engineering}, volume = {2}, number = {1}, pages = {27-38}, year = {2018}, publisher = {Amirkabir University of Technology}, issn = {2588-2937}, eissn = {2588-2945}, doi = {10.22060/mej.2017.13172.5561}, abstract = {In this paper, for the first time, four thermal and environmental objective functions are simultaneously taken into account in the process of the optimal design of a natural gas diffusion burner. The burner thermal efficiency and the emissions of carbon monoxide, nitrogen oxide, and unburned methane constitute the objective functions of the present study. In the first step, the burner is numerically simulated, and the simulation results are verified through being compared with the available experimental data. Next, the simulation is carried out for the different set values of design variables (the dimensions of the air and fuel inlets, and the overall equivalence ratio) and the optimum design is chosen by using “Pareto front concept”. The paper will show that as a result of the mentioned procedure, the burner thermal efficiency is increased by 29.4%, and the emissions of carbon monoxide, nitrogen oxide, and unburned methane are decreased by 81.2%, 98.6%, and 83.9%, respectively. The manuscript explains the reasoning for the superiority of the modified design over the reference one in detail.}, keywords = {Diffusion burner,Numerical modeling,Multi-objective design,Thermal efficiency,Pollutants}, url = {https://ajme.aut.ac.ir/article_2741.html}, eprint = {https://ajme.aut.ac.ir/article_2741_2819ea8eeb484a25553709779082692e.pdf} } @article { author = {Abbasian Arani, A.A. and Sadripour, S. and Kermani, S.}, title = {Energy and Exergy Analysis and Optimization of a Heat Sink Collector Equipped with Rotational Obstacles}, journal = {AUT Journal of Mechanical Engineering}, volume = {2}, number = {1}, pages = {39-50}, year = {2018}, publisher = {Amirkabir University of Technology}, issn = {2588-2937}, eissn = {2588-2945}, doi = {10.22060/mej.2017.12960.5486}, abstract = {In this paper, the forced convection flow in a heat sink collector equipped with stationary and rotational obstacles is studied numerically. Three-dimensional governing equations are solved by control volume approach based on the SIMPLE algorithm and k.. turbulence model. Reynolds numbers are considered in the laminar-turbulent range of 50 < Re < 12,000. The optimization was carried out by variation of related parameters. It is concluded that using heat sink, instead of a customary instrument, increases the outlet temperature from the collector and exergy efficiency due to longer installing of the fluid inside the collector. Also, it is realized that using the stationary and rotational obstacles enhance the outlet fluid temperature (about 2.5°C), energy efficiency and exergy efficiency. Nevertheless, using the rotational obstacles is more effective than the stationary obstacles. While the trend of exergy efficiency variation with effective parameters is increasing, applying the obstacles precipitates the efficiency increment (from 4% to 5.3%). In addition, for the case that the trend of exergy efficiency variation by changing these parameters is decreasing, the decreasing trend gets slow. There is a unique mass flow rate (0.005 kg/s) that the exergy efficiency gets a maximum value and for the higher mass flow rates, the efficiency decreases slightly and then remains unchanged.}, keywords = {Heat sink collector,Rotational obstacles,Exergy optimization,forced convection,Radiation}, url = {https://ajme.aut.ac.ir/article_2744.html}, eprint = {https://ajme.aut.ac.ir/article_2744_17bf4343deebd78d21cfc32e04b3f60a.pdf} } @article { author = {Afrasiab, H.}, title = {A Fluid-Structure Interaction Study on Vulnerability of Different Coronary Plaques to Blood Flow Increase During Physical Exercise}, journal = {AUT Journal of Mechanical Engineering}, volume = {2}, number = {1}, pages = {51-60}, year = {2018}, publisher = {Amirkabir University of Technology}, issn = {2588-2937}, eissn = {2588-2945}, doi = {10.22060/mej.2017.13415.5625}, abstract = {Pathological studies have shown that coronary atherosclerotic plaques are more prone to rupture under physical exercise. In this paper, using a fully coupled fluid-structure interaction (FSI) analysis based on arbitrary Lagrangian-Eulerian (ALE) finite element method, the effect of the coronary blood flow rate increase during physical exercise on the plaque rupture risk is investigated for different plaque types. It is proved that the increase in coronary blood flow rate during physical exercise considerably increases the maximum stress in the plaque fibrous cap which can potentially lead to the plaque rupture. The issue is investigated for different plaque shapes and their vulnerability to exercise condition is compared. It is observed that the diffused plaque type which experiences the maximum stress of 187.9 kPa at rest and 544 kPa at exercise is the most critical plaque type. Because it is subjected to the highest stress in both of these conditions. However, the descending plaque type exhibits the highest susceptibility to physical activity, since its maximum stress increases from 68.9 kPa at rest to 280.5 kPa at exercise which means an increase of about 308%.}, keywords = {Atherosclerosis plaque rupture,Physical exercise,Fluid–structure interaction analysis,finite element method,Plaque shape}, url = {https://ajme.aut.ac.ir/article_2739.html}, eprint = {https://ajme.aut.ac.ir/article_2739_d61e5a59a647cc9d8d13c9515fe24180.pdf} } @article { author = {Hemmasian Ettefagh, M. and Naraghi, M. and Mahzoon, M.}, title = {Robustness of Controlled Lagrangian Method to the Structured Uncertainties}, journal = {AUT Journal of Mechanical Engineering}, volume = {2}, number = {1}, pages = {61-72}, year = {2018}, publisher = {Amirkabir University of Technology}, issn = {2588-2937}, eissn = {2588-2945}, doi = {10.22060/mej.2017.12758.5431}, abstract = {Controlled Lagrangian method uses the inherent geometric structure of the energy of the mechanical systems to provide a stabilizing algorithm for underactuated mechanical systems. The presented method belongs to a larger family of nonlinear control algorithms, namely energy shaping methods in which the controller is designed by providing necessary modifications in the mechanical energy of the system. This paper presents a sensitivity analysis of Controlled Lagrangian method. It is shown that the method presents a suitable performance under the effect of structured (or parametric) uncertainties such as masses values, their positions and their influence on the inertia tensor. Then, the sequel investigates the robustness level of the designed controller in the presence of structured uncertainties. A detailed robustness proof of the scheme is established in this paper. Simulations are provided for a linear inverted pendulum cart system to validate analytical results of robustness to parametric uncertainties. Simulation results confirm that the designed controller for the inverted pendulum, which is unstable and underactuated, is well robust against parametric uncertainties as the analytical studies predicted. The method was also compared with the sliding mode approach, which showed a superior robustness against parametric uncertainties and a more practical control input value.}, keywords = {Controlled Lagrangian,Sensitivity analysis,Robustness,Structured uncertainties,Underactuated systems}, url = {https://ajme.aut.ac.ir/article_2753.html}, eprint = {https://ajme.aut.ac.ir/article_2753_86fbfb9c1e4968b5f982619fc684d807.pdf} } @article { author = {Afshari, H. and Torabi, K. and Hajiaboutalebi, F.}, title = {Exact Closed-Form Solution for Vibration Analysis of Beams Carrying Lumped Masses with Rotary Inertias}, journal = {AUT Journal of Mechanical Engineering}, volume = {2}, number = {1}, pages = {73-90}, year = {2018}, publisher = {Amirkabir University of Technology}, issn = {2588-2937}, eissn = {2588-2945}, doi = {10.22060/mej.2017.12932.5475}, abstract = {In this paper, an exact closed-form solution is presented for free vibration analysis of Bernoulli–Euler beams carrying attached masses with rotary inertias. The proposed technique explicitly provides frequency equation and corresponding mode as functions with two integration constants which should be determined by external boundary conditions implementation and leads to the solution to a two by two eigenvalue problem. The concentrated masses and their rotary inertia are modeled using Dirac’s delta generalized functions without implementation of continuity conditions. The non-dimensional inhomogeneous differential equation of motion is solved by applying integration procedure. Using the fundamental solutions which are made of the appropriate linear composition of trigonometric and hyperbolic functions leads to making the implementation of boundary conditions much easier. The proposed technique is employed to study the effects of quantity, position and translational and rotational inertia of the concentrated masses on the dynamic behavior of the beam for all standard boundary conditions. Unlike many of the previous exact approaches, the presented solution has no limitation in a number of concentrated masses.}, keywords = {Vibration analysis,Concentrated mass,Rotary inertia,Dirac’s delta function}, url = {https://ajme.aut.ac.ir/article_2754.html}, eprint = {https://ajme.aut.ac.ir/article_2754_dcadc9c4fcb956e606786b3ec673d8ea.pdf} } @article { author = {Zeinolabedini, M. R. and Rafeeyan, M.}, title = {Effect of Concentrated Axial Harmonic Force on Lateral Vibration of a Mono- Disk Rotating Shaft}, journal = {AUT Journal of Mechanical Engineering}, volume = {2}, number = {1}, pages = {91-96}, year = {2018}, publisher = {Amirkabir University of Technology}, issn = {2588-2937}, eissn = {2588-2945}, doi = {10.22060/ajme.2018.12951.5485}, abstract = { Rotors are widely used in industry and studying their vibrations is important. Lateral vibration of the rotors during operation is more important than its other vibration modes such as axial and torsional. The aim of this paper is to determine the effects of loads axially exerted on the assembled disk on a rotor as an introduction to modeling common phenomena such as surge and chock in rotors. Therefore, in this paper, the effect of a concentrated axial force acted on disk on the lateral vibration of a jeffcott rotor is investigated. Also, the effect of unbalance force on vibration behavior of the rotor is studied. The equation of motion was derived from Timoshenko beam model. The set of governing equations for vibration analysis of the rotor consist of four coupled partial differential equations. Since the derived equations are complex and coupled, and they have time-varying coefficients, they are solved by a combination of Galerkin and Newmark methods. Numerical examples are analyzed. The accuracy of derived equations is verified for a simple beam. Results show that the axial load is considerably effective on the amplitude of the lateral vibration of the rotor.}, keywords = {Jeffcott rotor,Axial load,Lateral vibration,Time response}, url = {https://ajme.aut.ac.ir/article_2770.html}, eprint = {https://ajme.aut.ac.ir/article_2770_f8d532b1ff6c60f0f8109d009dd1cdeb.pdf} } @article { author = {Moazam, M.A. and Honarpisheh, M.}, title = {Residual Stresses Measurement in UIC 60 Rail by Ring-Core Method and Sectioning Technique}, journal = {AUT Journal of Mechanical Engineering}, volume = {2}, number = {1}, pages = {99-106}, year = {2018}, publisher = {Amirkabir University of Technology}, issn = {2588-2937}, eissn = {2588-2945}, doi = {10.22060/mej.2017.12879.5457}, abstract = {The measurement of residual stress in rail foot, according to manufacturing standards is mandatory. In this study, the ring-core method and the sectioning technique are used to measure the residual stresses. A calibration technique for the ring-core method has been explained and simulated by the finite element analysis. The calibration coefficient has been determined for certain parameters and various depths of the annular groove. The ring-core method has been simulated for the uniaxial residual stress field and it is observed that the maximum error in the maximum principal residual stress was about 13% which is about 5% of material yield stress. The residual stresses have been measured at the UIC 60 rail foot by the ring-core method and the sectioning technique, and the results are in a good agreement with earlier investigations in this field. Also, it has been indicated that maximum residual stresses on the rail foot are not in the longitudinal direction and in the subsurface of the rail foot, the maximum principal direction coincides with the longitudinal direction. Both methods indicated tensile residual stresses on the rail foot, but the ring-core method predicted 27% higher longitudinal residual stress on the rail foot in comparing with the sectioning technique.}, keywords = {Residual stress,Sectioning,Ring-Core,Calibration coefficient,Rail}, url = {https://ajme.aut.ac.ir/article_2737.html}, eprint = {https://ajme.aut.ac.ir/article_2737_46d4340a195ded3a0476354ed2e13dc3.pdf} } @article { author = {Talebi, S. and Sadighi, M. and Aghdam, M. M.}, title = {The Effect of Impact Energy Parameters on the Closed-Cell Aluminum Foam Crushing Behavior Using X-Ray Tomography Method}, journal = {AUT Journal of Mechanical Engineering}, volume = {2}, number = {1}, pages = {107-116}, year = {2018}, publisher = {Amirkabir University of Technology}, issn = {2588-2937}, eissn = {2588-2945}, doi = {10.22060/mej.2017.13385.5613}, abstract = { The present study is devoted to the numerical and experimental investigation of the influence of dominant impact parameters, including inertia and impact velocity, on the closed-cell aluminum foam behavior. In order to access 3D modeling of the internal microstructure of the foam samples, a new technique based on computerized tomography (CT) of 2D images is utilized. The influence of the abovementioned influential parameters is studied for three different foam densities. In order to validate finite element results, low-velocity impact tests were conducted. The results demonstrate that for a constant level of impactor energy, two primary impact quantities of interest, i.e. maximum stress and energy absorption, are highly dependent on the values of impactor momentum. In contrast, increasing the value of impactor inertia results in negligible variations of energy absorption for different foam densities. Similarly, increasing inertia at a constant foam density shows no significant variation in peak stress and a slight change in energy absorption. On the other hand, the velocity of impactor at a constant level of impactor energy plays a crucial role such that for all three different foam sample densities, the case of higher impactor velocity causes greater values of peak stress as well as energy absorption.}, keywords = {Finite element analysis,Experimental test,Low-velocity impact,Closed-cell aluminum foam,Energy Absorption}, url = {https://ajme.aut.ac.ir/article_2743.html}, eprint = {https://ajme.aut.ac.ir/article_2743_52bde5b0c3c6a909978520323ef2c481.pdf} } @article { author = {Abootorabi, M. M.}, title = {Multi-objective Optimization of Surface Roughness and Material Removal Rate Using an Improved Self-Adaptive Particle Swarm Optimization Algorithm in Milling process}, journal = {AUT Journal of Mechanical Engineering}, volume = {2}, number = {1}, pages = {117-124}, year = {2018}, publisher = {Amirkabir University of Technology}, issn = {2588-2937}, eissn = {2588-2945}, doi = {10.22060/ajme.2018.12581.5373}, abstract = {Surface roughness is one of the main characteristics of a work piece in the quality control process. Several parameters such as cutting tool material and geometry, cutting parameters, work piece material properties, machine tool and coolant type affect the surface quality. An important task of process planners is the proper selection of three main cutting parameters: cutting speed, feed rate, and depth of cut in order to have not only low surface roughness, but also to perform the process within a reasonable amount of time. In this paper, using full factorial experiment design, the multiple regression equation for the surface roughness in the climb milling process of DIN 1.4021 martensitic stainless steel has been obtained and then used as one of the objective functions in the Multi-objective Improved Self- Adaptive Particle Swarm Optimization (MISAPSO) algorithm. This algorithm has been used to obtain cutting parameters to achieve low surface roughness simultaneously with a high material removal rate. The relatively new algorithm MISAPSO developed with some changes in the common particle swarm optimization (PSO) technique, has been used in multi-objective optimization of machining processes and was shown to be able to help the process planners in selecting cutting parameters.}, keywords = {Surface roughness,Material removal rate,Milling,Regression,MISAPSO}, url = {https://ajme.aut.ac.ir/article_2769.html}, eprint = {https://ajme.aut.ac.ir/article_2769_45b67bc8dd25058fa23f5c52948ca9dc.pdf} }