Amirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29375320210901Effects of gas temperature rise on steady state behavior of non-circular two-lobe micro gas bearings343360424810.22060/ajme.2021.18654.5910ENAziz MohammadGharanjikFaculty of Mechanical Engineering, Shahrood University of Technology, Shahrood, IranArdeshirKarami MohammadiFaculty of Mechanical Engineering, Shahrood University of Technology, Shahrood, IranJournal Article20200630In this paper, the molecular gas lubrication model is used to analyze the steady state behavior of two-lobe non-circular gas lubricated micro bearings. In this way, the effects of increasing temperature and gas rarefaction can be considered and then examined and analyzed. Behavior characteristics of two-lobe non-circular bearings with very small sizes differ from conventional sizes, especially at high temperatures and/or high rotational speeds. At high temperatures, in addition to diluting the gas, its viscosity and friction also change, and slippage may occur at the boundaries. The nonlinear equation governing the behavior of the gas is discretized using the finite element method and then solved together with the static equations of the rotor. Then the effects of temperature increase and gas rarefaction on gas pressure profile, load bearing capacity, angle of attitude, eccentricity ratio and frictional power loss have been studied and analyzed. The results show that the temperature rise and the gas rarefaction have significant effects on the steady state behavior of micro gas bearings. Among the results is that with increasing gas rarefaction, the gas pressure and consequently the load carrying capacity decrease more, and the attitude angle also increases more.https://ajme.aut.ac.ir/article_4248_5f245ebebce62ddcfacd1b6292c69392.pdfAmirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29375320210901Vibration analysis of piezoelectric graphene platelets micro-plates361386423410.22060/ajme.2021.18655.5911ENFatemehAbbaspourFaculty of Engineering, Shahrekord University, Shahrekord, IranHadiArvinFaculty of Engineering, Shahrekord University, Shahrekord, IranJournal Article20200630Free and forced vibration analyses of micro-plates reinforced with graphene platelets integrated with piezoelectric layers are presented. For thermo-electrical vibration examination, a uniform temperature field and a constant external electric field along the thicknesses of the piezoelectric layers are considered. On the other hand, a uniform in-plane load is regarded along the micro-plate edges for a mechanical free vibration analysis. The Halpin–Tsai micromechanical model is used to estimate the material properties of each layer of the graphene platelets of core layer. A convergence examination is conducted to reach a functionally graded dispersion of graphene platelets layers despite the implementation of several individual graphene platelets layers. Four different distribution patterns of graphene platelets are considered to examine the vibration features for simply-supported boundary condition employing Navier’s technique. Several numerical studies are accomplished to demonstrate the effects of the weight fraction, the distribution pattern, the width and the length of the graphene platelets besides the material length scale parameter, the thickness of the piezoelectric layers, the micro-plate length to the core layer thickness ratio, the applied voltage, the temperature change and the in-plane force on the natural frequencies and the time history response. The results demonstrate that in thermal environment not only reinforcing with graphene platelets does not improve the structural stiffness but also deteriorates it.https://ajme.aut.ac.ir/article_4234_fd45ebc1e1d76bc1fe0ba933e60e9957.pdfAmirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29375320210901Optimum design and comparison of four soft reinforced actuators by Taguchi experimental design method387400422510.22060/ajme.2020.18667.5915ENAmirJanghorbanFaculty of Mechanical and Materials Engineering, Graduate University of Advanced Technology, Kerman, IranRezaDehghaniFaculty of Mechanical and Materials Engineering, Graduate University of Advanced Technology, Kerman, Iran0000-0002-5268-0402MasoudRezaeizadehFaculty of Mechanical and Materials Engineering, Graduate University of Advanced Technology, Kerman, IranJournal Article20200706In this paper, four soft reinforced actuators are studied and their performance is compared. The soft actuators, because of their ability to match their shape with unknown environment, could be utilized in medical instruments such as rehabilitation devices, grippers, manipulators and bio-mimic hand. Here, the considered actuators are included a single elastomer channel wrapped with fiber reinforcements and an inextensible layer. Four actuators with half-circular and rectangular geometry are discussed. Two actuators have constant cross section and others have variable cross section. To study their performance they are modeled in Abaqus software. Also, a prototype of the soft actuator is manufactured and the numerical results are validated by the experiment results. Moreover, for studying the effect of each parameter and their interactions and finding the optimum design of the actuators the Taguchi method is used with a set of experiments. To this end, L27 array experiments are designed and each experiment is performed by finite element analysis in Abaqus. Then, the performance of each actuator is discussed and compared with each other and the optimum values of the parameters are determined. Results show the rectangular actuator has a more range of motion in comparison to half-circular one.https://ajme.aut.ac.ir/article_4225_d0ac1ed0c5cb9ecbca3d2496ec1ad984.pdfAmirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29375320210901Numerical and experimental investigation of effective parameters on separation force in bottom-up stereolithography process401418416210.22060/ajme.2020.18408.5903ENFarzadYadegariNew Technologies Research Center, Amirkabir University of Technology, Tehran, Iran
- Mechanical Engineering Department, Amirkabir University of Technology, Tehran, IranRasulFesharakifardNew Technologies Research Center, Amirkabir University of Technology, Tehran, Iran0000-0003-4789-3603FarshadBarazandehMechanical Engineering Department, Amirkabir University of Technology, Tehran, IranJournal Article20200530Bottom-up stereolithography is included among the additive manufacturing methods, which gives many advantages over top-down stereolithography. The major advantages are related to better fabrication resolution, higher material feed-rate, shorter production time and less material waste. During this process, a separation force is generated as a solidified layer separates from the base of resin container. This force leads to product delamination which in turn stimulates the product failure. An efficient solution to this problem is achieved by studying the interaction force on the specimen contact zone. The approach proposed in this study is based on experimental measurements of the force exerted during the process. Different parameters regarding process characteristics are varied in several tests and a comprehensive analysis is conducted to correspond test condition to the resulting separation force. The significant parameters are process speed, cross-section area, the complexity of geometry and orientation of solidification. For some different cases, the separation force varies between 3 and 36N, and the highest difference between the simulated and experimental results remains beyond 5%. It is observed that higher velocity, larger cross-section area or more part geometry complexity increase the separation force. Another novelty concerns the study of the producing orientation on the separation force. Related experimentation is performed to determine the effect of cross-sectional and geometrical complexity. This article finally gives some preliminary propositions for the part design.<br /><strong> </strong>https://ajme.aut.ac.ir/article_4162_56c51a39a7c77d8084838cc920585bd0.pdfAmirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29375320210901An experimental investigation on temperature distribution in high-speed milling of AZ91C magnesium alloy419426416410.22060/ajme.2020.18635.5909ENMahdiKarimiModern Manufacturing Technologies Research Center, Department of Mechanical Engineering, Najafabad Branch, Islamic Azad University,
Najafabad, IranRezaNosuhiModern Manufacturing Technologies Research Center, Department of Mechanical Engineering, Najafabad Branch, Islamic Azad University,
Najafabad, IranJournal Article20200624Magnesium alloys are widely used materials in industry because of their formability and low density. The machining process of these alloys; however; is a challenging problem due to their flammability. This challenge demands extensive studies on the work-piece and machining zone temperature, especially in processes with elevated temperature; such as high-speed machining. In this research, the temperature distribution of the AZ91C magnesium alloy in high-speed milling is investigated. In order to study the temperature distribution, two temperature measurement methods are employed (i.e. the infrared thermometer for measurement of the machining zone temperature, and the contact method for the work-piece temperature) and the results are presented. The experiments are carried out in different cutting speeds (both in high-speed range and normal speed range) in two different depths of cut. The results show that the work-piece temperature is reduced as the cutting speed passes the cutting speed of 452 m/min in high-speed milling, while the machining zone temperature is increased as a result of the increase in the cutting speed. The results also show that the temperature is increased 13.9% and 14.2% as the depth of cut is increased from 0.5 mm to 1 mm in the cutting zone and workpiece respectively, which is the result of an increase in the uncut chip area that results in higher cutting forces.https://ajme.aut.ac.ir/article_4164_861578d797aeb0634f77aff3f488cca2.pdfAmirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29375320210901An experimental investigation on low-velocity impact response of nanoclay-reinforced fiber metal laminates427438409410.22060/ajme.2020.18284.5893ENAzadehArjangpayYoung Researchers and Elite Club, Islamic Azad University, West Tehran Branch, Tehran, IranAmirDehdariDepartment of Mechanical Engineering, Islamic Azad University, South Tehran Branch, Tehran, IranMehdiYarmohammad TooskiDepartment of Mechanical Engineering, Islamic Azad University, South Tehran Branch, Tehran, IranJournal Article20200420In this experimental study, the effect of nanoclay addition into fiber metal laminates on low-velocity impact response is investigated. The reinforced fiber metal laminates considering 0, 1, 3, and 5 weight percentages of nanoclay were manufactured by hand lay-up technique. The specimens were then subjected to low-velocity impact tests using an instrumented drop-weight test setup at three different energy levels. To gain the range of tolerable impact energies before the fracture occurs, quasi-static tests were performed. Impact behaviors of the fiber metal laminates were compared in terms of force-time and force-displacement responses as well as the final energy absorption of the samples in addition to visual inspection of the damaged area. The results showed that the addition of 1 to 3 wt.% nanoclay into the laminates can improve their impact characteristics. Moreover, a noticeable reduction in physical damage was observed in nano-fiber metal laminates as compared to nano-free ones. On the other hand, it was found that the extra addition of nanoclay into the laminates can decrease their impact characteristics and make them be more brittle specimens than the nano-free samples.https://ajme.aut.ac.ir/article_4094_64c53a52cb3bd1a01c03a64db985c0cc.pdfAmirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29375320210901Evaluation of thermodynamics effect on mineral scale formation in water injection wells supported by laboratory experiments439450431910.22060/ajme.2021.18473.5900ENMostafaShajariDepartment of Chemical Engineering, Amirkabir University of Technology, Tehran, IranFariborzRashidiDepartment of Chemical Engineering, Amirkabir University of Technology, Tehran, IranJournal Article20200521Usually, some amount of unwanted water is being produced along with oil production in most of the oil fields. These waters are dangerous to environment and must be managed safely. In most cases, they are injected into water disposal wells. Scale formation and well plugging during water injection to disposal wells is a critical problem in waste water management. Main reasons for inorganic scale formation in these wells are incompatibilities of injection water and reservoir water, and thermodynamics condition variation of injection water. These mechanisms lead to the mineral scales precipitation and consequently, they are deposited in porous media which leads to injection rate reduction in water disposal wells. The critical place of scale formation is the well bottom. It is the entrance of injected fluids and commonly results in the increase of injection pressure and reduction of water injection. In the current study, the effect of pressure and temperature would be assessed on precipitation of inorganic scale by lab testing and software simulation at different mixing ratio of injection water to formation water. Also, some core flooding tests are run to evaluate the effect of deposited mineral scales on water injection process in the core samples. All input data of software modeling and core samples belong to a water injection well in a sand stone reservoir in south west of Iran.https://ajme.aut.ac.ir/article_4319_8e1ad7941398486f8cede7799b886b58.pdfAmirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29375320210901Computational fluid dynamics modeling of effect of dipleg geometry on separation efficiency of a square cyclone451464426010.22060/ajme.2021.18498.5902ENEsmaeelFatahianDepartment of Mechanical Engineering, Nour Branch, Islamic Azad University, Nour, IranHosseinFatahianDepartment of Mechanical Engineering, Nour Branch, Islamic Azad University, Nour, IranJournal Article20200604In the present work, an effective way is introduced to improve the efficiency of a square cyclone separator. For this aim, a dipleg is attached under the square cyclone to investigate its geometry effect on the performance of square cyclone separator. A three-dimensional computational fluid dynamics simulation is done by solving the Reynolds averaged Navier Stokes equations with the Reynolds stress model turbulence model and using the Eulerian-Lagrangian two phase method. The particle dispersion due to turbulence in the gas phase is predicted using the discrete random Walk model. The predicted results show that using a dipleg although produces an increase in pressure drop but it positively enhances the separation efficiency of the square cyclone. In the present results, the pressure drop is increased by about 19% by using dipleg at an inlet velocity of 28 m/s. Using dipleg significantly increases the separation efficiency of square cyclone especially at higher inlet velocity. This can be more obvious when using dipleg 1 which is minimized the 50% cut size of square cyclone by about 35.5%. Also, in higher inlet velocity, the reduction value of 50% cut size is higher which is proved that using dipleg is more effective due to stronger swirl flow.https://ajme.aut.ac.ir/article_4260_5101a4796c5127131b2112e2bc6fe02b.pdfAmirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29375320210901Numerical investigation of cardiac function parameters in left heart hemodynamics with stenosed mitral465476417710.22060/ajme.2020.18606.5906ENMaysamSaidiMechanical Engineering Department, Razi University, Kermanshah, Iran0000-0001-7423-334XRezaSamianEnergy Research Center, Amirkabir University of Technology, Tehran, IranJournal Article20200616This work studies the effect of cardiac function parameters on ventricular flow pattern in a stenosed mitral.A three-dimensional simulation is performed employing dynamic mesh based on a geometry and valve flow rates extracted from medical images. Different mitral areas from 6 to 2 cm<sup>2</sup> then different parameters for stenosed 2 cm<sup>2</sup> case are investigated. Special attention has been drawn to compare wall shear stress, blood velocity and pressure distribution, while the power used by ventricle and atrium to pump the blood are also highlighted. Computing the power used by the heart walls to move the blood shows that the stenosed mitral increases the needed force and the energy for the blood flow suction during the early diastole (from 0.06 W for mitral area of 6 cm<sup>2</sup> to 1.28 W for mitral area of 2 cm<sup>2</sup>). For the stenosed mitral area of 2 cm<sup>2</sup>, in the systole, decreasing the ejection fraction to half decreased the maximum ventricle power to around half. In the diastole, decreasing the E/A which is the ratio of early diastole (E wave) and late diastole (A wave) ratio from 4.8 to 1 decreased the maximum ventricle power to one-third. The numerical results confirmed that the compensation mechanism to afford the pumping power could be changing the E/A ratio which leads to enlarged atrium.https://ajme.aut.ac.ir/article_4177_13b919438259814cd5be8cb45877d577.pdfAmirkabir University of TechnologyAUT Journal of Mechanical Engineering2588-29375320210901Experimental investigation on laminar convective heat transfer of nano ferrofluids under constant and alternating magnetic field477494415810.22060/ajme.2020.18628.5908ENMatinGhadiriDepartment of Mechanical Engineering, Shahrood University of Technology, Shahrood, IranOmidHaghaniDepartment of Mechanical Engineering, Khayyam University, Mashhad, IranErfanEmam-jomehDepartment of Mechanical Engineering, Khayyam University, Mashhad, IranEbrahimBaratiDepartment of Mechanical Engineering, Khayyam University, Mashhad, IranJournal Article20200623Due to unique characteristic behavior of ferrofluids, their rheological and thermophysical properties will be able to change in the external magnetic field. In this paper, the effects of constant and alternating magnetic field on the convective heat transfer coefficient of ferrofluids in a heated circular tube under laminar flow regimes (200≤<em>Re</em>≤1600) are investigated experimentally. The fluids considered in the experiment are distilled water and a Fe<sub>3</sub>O<sub>4</sub>/water nanofluid with 1% and 3% concentrations by weight (wt%). The obtained results are validated and a good agreement between the experimental data and predicted results is observed. In the absence of a magnetic field, the results illustrate the significant improvement of convective heat transfer for 3 wt% ferrofluid, compared to that of the distilled water as a working fluid. The heat transfer enhancement varies by changing the Reynolds number as well as ferrofluid concentration and the type of applied magnetic field. The results also show that with application of alternating magnetic field with frequency of 50 Hz, the maximum of 5% enhancement in the convective heat transfer coefficient is obtained compared to the case with no magnetic field.https://ajme.aut.ac.ir/article_4158_3e3aa687770f55c704ca997c3be81634.pdf