IFC
text
article
2016
per
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
0
0
http://mme.modares.ac.ir/article_14849_1c1da377f980d4f5139d56ed20af6bd7.pdf
An investigation of the effect of microstructure on determination of acoustoelastic constants in austenitic stainless steel welding
Iman
Rahimi
Graduate / Amirkabir University of Technology
author
Shayan
Nejadshamsi
Graduated / Amirkabir University of Tehran
author
Farzam
Ghasimakbari
Graduated / University of Tehran
author
Mahdi
Ahmad Najafabadi
دانشیار دانشگاه صنعتی امیرکبیر، دانشکده مکانیک
author
text
article
2016
per
Residual stress measurement of in-service parts of a system is practically impossible by means of destructive methods. Therefore, the use of ultrasonic method as a non-destructive method has an important role. One of the problems in non-destructive measurement of residual stresses by means of ultrasonic waves is determination of acoustoelastic constants. In fact, for conversion of ultrasonic method data to stress state, it is needed to determine these coefficients very precisely. But for reasons like HAZ inclination and small width of this zone, determination of coefficient of this zone does not perform accurately. In this study, the practical simulation is performed for determination of acoustoelastic coefficient of HAZ. For this simulation, the heat affected zone divided to four separate zones and then the microstructure of those four zones has been simulated on standard tensile test specimen by different heat treatment cycles. This coefficient has been used in evaluation of welding residual stresses of austenitic stainless steel by LCR Ultrasonic waves and the results has been compared with the hole-drilling strain-gage method. By comparison of stress values achieved by HAZ simulation method, the conventional method and hole-drilling strain-gage method, it is seen that the HAZ simulation method cause an improvement in welding residual stress measurement accuracy.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
1
9
http://mme.modares.ac.ir/article_14603_478cea3d502b1f81db6cd08d4d6de0b2.pdf
Feedback-Feedforward Control System Design and Optimizing the Performance of Crude Oil Fired Heater Furnace Using Genetic Algorithm for Abnormal Conditions Management
Ali
Chaibakhsh
University of Guilan
author
Zohreh
Rostamnezhad
University of Guilan
author
Tahmineh
Adili
University of Guilan
author
Ali
Jamali
University of Guilan
author
text
article
2016
per
In this study, feedback-feedforward control system design and optimizing the performance of crude oil furnace process was investigated in order to be recovered from possible abnormal conditions. First, by developing an accurate nonlinear analytical model, the effects of changes in input parameters and operating conditions on the system’s outputs were determined. Then, in order to eliminate the effects of disturbances on furnace, a feedback- feedforward control system for combustion management was suggested, where its performances were optimized genetic algorithm (GA). In addition, to enhance the thermal stability and to maintain product quality, output difference temperature control system was considered for load distribution between furnace’s streams. Also, in order to recover the furnace from abnormal conditions due to burners’ failures, a supervisory system was designed to change the firing rate setpoints. With respect to different failure scenarios, the optimal burners’ firing rate were captured by applying genetic algorithms to the system model. A multilayer perceptron neural network was employed as the core of the controller to interpolate between different conditions. The obtained results indicate the superior performances of the designed control systems.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
10
18
http://mme.modares.ac.ir/article_14543_6787c06cce37fe65f6b18b562f8c681d.pdf
Investigation of the inertia of the lateral motions effect on free axial vibration of nanorods using nonlocal Rayleigh theory
Reza
Nazemnezhad
استادیار مهندسی مکانیک/ دانشکده فنی و مهندسی دانشگاه دامغان
author
Kamran
Kamali
کارشناسی ارشد مهندسی مکانیک/دانشگاه علم و صنعت ایران
author
text
article
2016
per
In this paper, free axial vibration of nanorods is investigated by focusing on the inertia of the lateral motions effects. To this end, Rayleigh and nonlocal theories considering the inertia of the lateral motions and the small scale effects, respectively, are used. Then, by implementing the Hamilton’s principle nonlocal governing equation of motion and boundary conditions are derived. Since using nonlocal elasticity causes that the 2-order local governing equation is changed to the 4-order nonlocal governing equation while number of boundary condition remains constant (one boundary condition at each end of nanorod), the governing equation is solved using Rayleigh-Ritz method. In Rayleigh-Ritz method a suitable shape function for the problem should be selected. The shape function must at least satisfy the geometrical boundary conditions. In the present study, orthogonal polynomials are selected as shape functions then they are normalized by using the Gram-Schmidt process for more rapid convergence. Then, the first five axial natural frequencies of nanorod with clamped-clamped and clamped-free end conditions are obtained. In the next step, effects of various parameters like length of nanorod, diameter of nanorod and nonlocal parameter value on natural frequencies are investigated. Results of the present study can be useful in more accurate design of nano-electro-mechanical systems in which nanotubes are used.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
19
28
http://mme.modares.ac.ir/article_14544_e38d5a4c80d3de841059760e591fe999.pdf
Studying the effects of design parameters on the final topology of planar structures by improved bi-directional evolutionary structural optimization method
Saeed
Shabani Nodehi
دانشجوی کارشناسی ارشد، مهندسی مکانیک، دانشگاه گیلان
author
Seyed Reza
Falahatgar
عضو هیات علمی/دانشگاه گیلان
author
Reza
Ansari
هیات علمی مهندسی مکانیک، دانشگاه گیلان
author
text
article
2016
per
Topology optimization of structure seeks to achieve the best material distribution in the Pre-determined design domain. In this paper, the effect of design parameters contains length scale parameter and evolutionary volume ratio in improved bi-directional evolutionary structural optimization method with soft kill approach is discussed. The main aim of this method is searching for the stiffest structure with a given volume of material using finite element method. At each iteration of finite element analysis, sensitivity number is calculated for each individual element in design domain and then converted to the nodal sensitivity number. With Filter Scheme and using length scale, an improved sensitivity numbers is defined. This number is used as a criterion for rating each element in design domain and determining the addition and elimination (remove) of elements. To increase the convergence of the optimization process, the accuracy of the new elemental sensitivity numbers is improved by considering the sensitivity history. This method is convergent and mesh-independent and there are no checkerboard pattern and local solutions in optimal topologies. Using three design samples, a cantilever and classical beam and Michell type structure, affecting factors will be discussed on the final design of the structure. Change of length scale parameter makes various schemes in final structures in which with increasing this parameter, more iteration is needed for convergent solution. Reducing evolutionary volume ratio forms different and even asymmetric topologies. Better final topologies are obtained with higher evolutionary volume ratios.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
29
38
http://mme.modares.ac.ir/article_14545_9d4257963788734f16ec946384046003.pdf
Experimental and numerical investigation of interlayer crack effects on the Free-vibration of corrugated-face sheet composite sandwich plates
Arash
Naeimi_Abkenari
فارغ التحصیل کارشناسی ارشد مهندسی مکانیک دانشگاه بوعلی سینا همدان
author
Mahdi
Karimi
Assistant Professor of Mechanical Engineering
author
text
article
2016
per
Today, composite material and sandwich plate structures are used more and more due to the unique properties such as a high ratio of strength to weight, corrosion resistance and energy or sound absorption ability. Corrugating sandwich structures is an effective method to reinforce mechanical properties of the composite materials. In this paper, dynamic analysis of these corrugated structures was carried out for a desired performance in the vibratory condition. One of the most important damages in the composite material layers is an inter-layer crack and also the separation between two layers. Vibration analysis of the trapezoidal corrugated sandwich plate was accomplished with ANSYS software using the finite element method. Simulated sandwich plate is a new model of corrugated sandwich plate which has a soft corrugated foam core and a cover of composite layers made from epoxy/glass. In order to validate the vibration behavior of the simulated sandwich plate, the results of experimental modal analysis were compared to the finite element method. The geometry and location effects of inter-layer crack on natural frequencies of the plate were investigated. It was found that with increasing crack dimensions the natural frequencies of the plate decreases and also depth of crack causes decreasing the natural frequencies which are promising results compared to the other references. The changes in vibration characteristics of the sandwich plate can produce comprehensive data to be used in training and designing of the artificial neural network for a promising approach in fault detection and prediction field.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
39
50
http://mme.modares.ac.ir/article_14576_c4d168d56b38b1ba8c271d122171bbbd.pdf
Experimental and Numeral Analysis of Composite metal Vessel under Dynamic Loading
Ali Asghar
Masumi
دانشگاه تربیت مدرس
author
Golam Hossein
Rahimi
استاد، مهندسی مکانیک، دانشگاه تربیت مدرس، تهران
author
Golam Hossein
Liyaghat
استاد، مهندسی مکانیک، دانشگاه تربیت مدرس، تهران
author
text
article
2016
per
In this paper, numeral and experimental analysis of composite metal vessel is investigated under variable pressure loading. For this purpose, a sample of multi section cylindrical vessel is considered. The pizo electric 1000 bars sensors are used to measure pressure. The sensors are installed in the holes on the metal cylindrical vessel. The amplification parts are used to adjust sensors. The test is done under dynamic loading. The results are recorded by data logers in pressure-time chart. The aim of this study is to optimize the weight and strength of the vessel with using trial and error by numeral analysis inverse explosive loading. In order to, a sample of multi section cylindrical vessel is analyzed with abaqus finite element software. The load in the vessel is derived by charts from experimental tests. The load obtained from experimental tests as a dynamic load is analyzed and compared with metal vessel and metal- Composite vessel. The results obtained from abaqus finite element software have discussion in different case. Finally, geometric and material properties of liner and composite is suggested for optimize the weight and strength of the vessel.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
51
62
http://mme.modares.ac.ir/article_14577_03dea97af543346cc31831716c8ae8c8.pdf
Input acoustic impedance measurement of Ney with Pulse reflectometry method
Ayoub
Banoushi
سازمان انرژی اتمی ایران
author
Edris
Mohammady Talvar
دانشجوی کارشناسی ارشد
author
Mohsen
Broghany
دانشجوی کارشناسی ارشد
author
text
article
2016
per
Investigation of frequency variations of acoustic impedance can play an important role in identification and optimization of a musical instrument. For a simple tube, the input acoustic impedance can be calculated by analytical methods; for complex geometry objects like wind instrument, however, it cannot be simply computed. Therefore, the impedance is measured for wind instruments. This paper is report of first experiment for measuring the input acoustic impedance of Ney (an Iranian woodwind instrument). For this purpose, a pulse reflectometer device was made. For assurance of correct operation of the reflectometer, in the first step, the input acoustic impedance of a three sections step tube was measured and the results were compared with calculated results using well known formula. the acoustic impedances of a Do-ney for various fingering in six case (from closed all holes to opened all holes) were measured. The results show that, contrary to what seen for flout, the frequencies of minima of the impedance curves have some discrepancies with the frequencies of corresponding playable notes. This may relate to the role of mouth of instrument player in producing tones of ney.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
63
69
http://mme.modares.ac.ir/article_14578_f1b4ab759781bae5bede4f43d3e3d9c6.pdf
Investigation on effect of exhaust vents location on reduction of pollution in enclosed car parks
Javad
Amnian
دانشجو/ دانشگاه تربیت مدرس
author
Mehdi
Maerefat
هیئت علمی دانشگاه تربیت مدرس
author
Ghasem
Heidarinejad
هیات علمی دانشگاه تربیت مدرس
author
text
article
2016
per
The correct placement of supply air inlets and pollution extraction outlets play an important role in increasing indoor air quality and reducing the amount of pollution in enclosed car parks. In this paper the effect of exhaust locations, exhaust height and parking dimensions on indoor air quality of car park is investigated with numerical simulation. For this purpose conservation equations are solved with openFoam. For validation, air flow and pollution is simulated in a simple car park and compared with experimental results. In the next section, the effect of exhaust vent locations on increasing indoor air quality is investigated and is compared with other solutions. The result of numerical simulation indicates that, if inlets and exhausts are located in end sides of car park and if exhaust vent locations are in the optimized height, the indoor air quality in the car park is increased.in this paper, the graph of CO concentration in different heights is explained and by using it, the optimum range for exhaust vent locations is proposed. Moreover the standard criteria for using jet fans is expressed and the results showed that, for ventilation of car parks with length more than criterion, jet fans should be used.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
70
80
http://mme.modares.ac.ir/article_14579_abb9bd0814981b0b013e07149d7a5daf.pdf
Investigating the Effect of single wall carbon nanotubes in the context of epoxy resin on the electromagnetic waves in the X-band
Rasoul
Tarkesh esfahani
هیئت علمی دانشگاه آزاد اسلامی واحد نجف آباد
author
Seyyed Alireza
Hashemi
فارغ التحصیل
author
text
article
2016
per
Carbon nanotubes have excellent mechanical, electrical, thermal and magnetic properties, among the extraordinary properties of these materials can be traced to the absorption of electromagnetic waves. By placement of this materials in direction of electromagnetic waves, significant volumes of this waves have been absorbed and also it’s reduce the radar cross section from a finder view, in this study we have produced composite samples containing SWCNTs in the context of an epoxy resin based on standard dimensions for X-band with a multi-stage built method and then these samples have been analyzed by Vector Network Analyzer. Composite samples have been made in three weight percent, 1, 3 and 10. The result of this experiment shows the high amount of wave absorption for samples reinforced by carbon nanotubes. This amount of absorption greatly increase due to increasing of nanotubes weight percent, so that the average amount of absorption in the whole X-band for the mentioned percentages is 3.33712, 4.5889 and 12.6542 dB respectively. Also the amplified samples with 1, 3 and 10 weight percentages, showing increase in wave absorption about 22, 67 and 362 percent in comparison with pure resin. Finally samples have been evaluated with Micro Raman Spectroscopy and SEM images.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
81
89
http://mme.modares.ac.ir/article_14591_1f0e6c3e2f1727e533477ca1a3e9d8e4.pdf
Small scale effect on the dynamic pull-in instability of torsional nano-actuators using 2-DOF model
Soroosh
Malihi
دانشگاه شهرکرد
author
Yaghoub
Tadi Bani
دانشیار دانشکده فنی و مهندسی دانشگاه شهرکرد
author
text
article
2016
per
Consideration of dynamic and static behavior of structures in nano and micro scale for analysis and predicting of their performance and accuracy have more importance. In this study, the effect of size and intermolecular van der Waals force on dynamic behavior of torsional nanomirror considering bending-torsion two degree of freedom model using the higher order modified couple stress theory has been investigated. First considering the higher order modified couple stress theory and intermolecular van der Waals force, equation of motion of system is developed, afterwards using Rung-Kuta method, this equations is solved and dynamic performance of nanomirror and its phase portraits have been obtained. Also translational and torsional natural frequencies of system considering applied voltage are investigated. So pull-in instability parameters of system are considered and their dependency upon van der Waals force and size effects are determined. Results demonstrate that equilibrium points of system include center points and focus points that phase portraits related to these points exhibit periodic orbits and heteroclinic orbits. Also size effect and modified couple stress model on amplitude and frequency of vibration of system have been investigated. Proposed model in this study is able to predict experimental results with higher precision than previous classic models and reduce the difference between past theories and empirical results.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
90
100
http://mme.modares.ac.ir/article_14610_d67a2ca6178d46b708c457cb527b38f8.pdf
An Optimized Method for Upper-stage System design
Mehran
Nosratollahi
دانشگاه صنعتی مالک اشتر
author
Mostafa
Zakeri
دانشگاه مالک اشتر
author
Alireza
Novinzadeh
دانشگاه خواجه نصیر
author
text
article
2016
per
The purpose of this article is the implementing the upper stage design according to multistep sequential optimization design process for specific maneuvers with less mass in reality. In this method there is two optimization and design loops which are connected to each other in mass analysis. So all the output parameters in inner loop are used as input parameters of outer loop. In the inner loop, optimization control algorithm is used to optimize the target function, as for two control factors including thrust vector angle and thrust magnitude for putting upper stage into final orbit. In outer loop, subdivision designed separately according to design matrix using input parameters from inner loop. Design convergence checked in mass analysis. Innovation of this article is implementing a fully systematic upper stages design. Also a system-based method is provided by cooperation of human and machine (multistep collaborative design) which in addition to system design discussed subsystem design such as orbital optimization and subdivision algorithms. Results of this design are verified according to result of statistical analysis.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
101
110
http://mme.modares.ac.ir/article_14592_6891aa7cdde357fd77a0e860d117e455.pdf
Investigation of the geometry effects on the thermo-hydrodynamic performance of noncircular journal bearings using GDQ method
Asghar
Dashti Rahmatabadi
Associate Professor- Yazd University
author
Abolfazl
Rasoolizadeh Shooroki
Yazd university
author
Mahdi
Zare Mehrjardi
Ardakan university
author
text
article
2016
per
Noncircular lobed journal bearing performance, in comparison with circular types, depends on various design parameters such as tilt and mount angles. Mounting orientation of this kind of bearings with respect to machine frame (mount angle) and also the way of setting their lobes with respect to each other (tilt angle), can change the bearings configuration and as the result their performances. In present study the thermo-hydrodynamic performance of noncircular two, three and four lobed journal bearings for different values of tilt and mount angles, using generalized differential quadrature (GDQ) method, are investigated. The results show that the thermal effects on these bearings performance are considerable and that the thermal consideration makes the results closer to real performance situations. The results of bearings performances due to rise in temperature in rotor, lubricant fluid and bearing shell, when compared to their isothermal conditions, show that viscosity of lubricant as well as load carrying capacity of bearings are decreased, depending on tilt and mount angles especially in case of two lobed bearings. The results also show that the effects of tilt and mount angles on bearing performance are periodic and so it is possible to select these angles suitably for bearings to be optimum.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
111
122
http://mme.modares.ac.ir/article_14602_1c82b571d434950c30d9b56a1cd43447.pdf
Predicting the bending limit of AA8112 tubes using failure criterion in Hydro-Rotary draw bending process
Mehrdad
Paluch
دانش آموخته کارشناسی ارشد دانشگاه صنعتی نوشیروانی بابل
author
Majid
Elyasi
استادیار دانشگاه صنعتی نوشیروانی بابل
author
Morteza
Hoseinzadeh
عضو هیات علمی دانشگاه آزاد آیت الله آملی
author
text
article
2016
per
Nowadays thin-walled tube rotary draw bending in small bending ratio is a production process widely used in advanced industries such as aerospace and automotive. Cross section ovality, wall thickness changing during tube bending are the main inevitable defects in this process. The purpose of this research is to obtain the smallest bending ratio and maximum pressure applicable in hydro-rotary draw bending of thin-walled aluminum alloy 8112 tube using failure criterion. For this purpose, the equivalent plastic strain at the critical extrados region used for necking prediction. Concluded results showed that this failure criterion by a maximum difference of 12.5% from experimental tests, is a useful method for predicting the necking onset in the bending process. Moreover, the effects of bending ratio and internal pressure on the defects such as cross section ovality and thickness changing are investigated with simulation in the ABAQUS software and experimental methods. The maximum ovality is not located at the mid-cross section of bent tube unexpectedly and regardless of the internal pressure and bending ratio, occurs at the cross-section with an angle of approximately θ=33°. The minimum achievable amounts of ovality at R/D1.6, R/D1.8 and R/D2 were 11.42%, 7.72% and 4.35% respectively. Furthermore, bending ratio and internal pressure had noticeable effects on the cross section of the bent tubes, so that as the bending ratio or pressure increased, cross-section ovality and the thickening of the tube wall at the intrados decreased, but contrary to bending ratio, as the internal pressure increased, extrados thinning increased.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
123
134
http://mme.modares.ac.ir/article_14607_04afb584f213cd167c169a0c5b2b5f48.pdf
Numerical optimization of “Planar twist channel angular extrusion” as a novel severe plastic deformation method by DOE method
Mahmoud
Shamsborhan
Asistant professor of engineering faculty of Islamic Azad university- Mahabad branch
author
Mahmoud
Moradi
استادیار- دانشکده مهندسی- دانشگاه ملایر
author
Ali
Shokuhfar
استاد، مهندسی مکانیک، دانشگاه صنعتی خواجه نصیرالدین طوسی، تهران
author
text
article
2016
per
The most successful ‘‘top–down’’ approach to produce bulk ultra-fine grained or nanostructured materials involves the use of severe plastic deformation (SPD) processing. The amount of higher effective plastic strain per pass plays a key role on the final microstructure of SPD processed samples. In the present study the numerical experiments of the combination of the equal channel angular pressing (ECAP) and simple shear extrusion (SSE) as a new process entitled “planar twist channel angular extrusion (PTCAE)” was performed based on the Response Surface Methodology (RSM), as a statistical design of experiment approach, in order to investigate the effect of parameters on the response variations, achieving the mathematical equations, predicting the results to impose higher effective plastic strain values. Α and ϕ angles, radius and friction coefficient was imposed as the input parameters while average, minimum and maximum effective strain and maximum load was imposed as the output parameters. Governing regression equations obtained after analysis of the simulation data by Minitab software. Optimum process parameters are: α=450, Φ =450, r=2 mm and µ=0.1. Verification of the optimum results using simulation experiment was done. Good agreement between simulation, experimental and optimization was occurred.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
135
144
http://mme.modares.ac.ir/article_14608_f4c2884daa956777b4e90f3fe5cd8526.pdf
Fracture analysis of a unidirectional composite double cantilever beam specimen with finite length
AmirReza
Shahani
استاد دانشکده مکانیک دانشگاه صنعتی خواجه نصیر الدین طوسی
author
Razieh
Abolfathitabar
PhD student of K. N. Toosi university of technology
author
text
article
2016
per
The unidirectional composite DCB specimen is considered as two finite length Timoshenko beams, attached together along a common edge except at the initial delamination length. Because of symmetry, only one half of the specimen is considered, which is partly free and partly resting on an elastic foundation. The problem is analytically solved by considering Timoshenko beam resting on Winkler and Pasternak elastic foundations and fracture toughness is generally derived. In the prior researches on this specimen using Timoshenko beam theory, the effect of the ligament length on the energy release rate was ignored. This research presents the solution for finite ligament length. Besides, the effect of ligament length on energy release rate and its minimum value that makes the energy release rate independent of the ligament length, is presented. For the special case when the ligament is large compared with the beam thickness, a closed form solution is derived for Timoshenko beam resting on Winkler elastic foundation. The analytical results are compared to prior researches on this subject and a good agreement is observed. The fracture toughness and compliance obtained by Timoshenko beam resting on Winkler elastic foundation predicts more accurate results with respect to experimental results.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
145
152
http://mme.modares.ac.ir/article_14609_4ea2d975fadfae6f99ead1fc047737f4.pdf
Analytical approach to estimate supercavity length based on cavity and Reynolds numbers
Mehdi
Maerefat
هیئت علمی دانشگاه تربیت مدرس
author
Sohrab
Tahmasebi
دانشجوی دکتری
author
Mohammad Reza
Ansari
عضو هیئت علمی دانشگاه تربیت مدرس
author
text
article
2016
per
Cavity length estimation is important as supercavity condition is generated. The cavity length is function of cavity number and is calculated by relations deduced from experimental results which are different from each other and are not driven from analytical approaches. Literature survey shows that correlations based on cavity length in relation with Reynolds and cavity numbers have not been attempted. The present work purpose is to estimate analytical based relations for cavity length with respect to mass transfer, continuity and momentum conservation equations. This effort which has been conducted by order of magnitude method resulted in three relations. The first analytical based relation calculates cavity length versus cavity number. The obtained relation shows that cavity length is proportional with the inverse square root of cavity number. The second analytical relation calculates cavity length in respect to Reynolds number. It shows cavity length has proportional relation to Reynolds square root. The third analytical relation considers cavity number in respect to Reynolds number. The third relation shows that cavity number has inverse relation to Reynolds number. Unknown coefficients values of the relations obtained through comparison with the already existed experimental results. These analytical relations which are appropriate alternative to experimental based relations estimate cavity length in respect to cavity and Reynolds number.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
153
159
http://mme.modares.ac.ir/article_14611_5ff3089616399558fc36c676218e28d8.pdf
Determination of Pressure Path and Punch Velocity in Hydroforming of Cup-Shaped Products Using Adaptive Simulation-Based Optimization
Abbas
Hashemi
دانشجوی دکتری/دانشگاه تربیت دبیر شهید رجایی
author
Mohammad
Hosseinpour
استادیار عضو هیئت علمی دانشگاه تربیت دبیر شهید رجایی
author
S. M. Hossein
Seyedkashi
استادیار/دانشگاه بیرجند
author
text
article
2016
per
In this paper, a practical method of combined finite element simulation and adaptive simulated annealing (ASA) optimization was developed to design and analyze sheet hydroforming process. Process simulation using finite element code with parametric definition of process parameters creates flexibility on the proposed method in which geometrical dimensions and properties of the workpiece and the die comprise a part of input data of optimization program. Redefinition of simulated annealing parameters with respect to hydroforming process caused to achieve data convergence in a shorter time and higher precision. An intermediate MATLAB code was developed to manage data transfer automatically between optimization and simulation codes, in which there would be no need to any interference of user/designer during the optimization process. The aim of this research for presenting the combinatorial procedure of flexible simulation is to achieve optimal forming pressure loading path, determine the desired punch velocity, produce the desired workpiece with minimum thinning, and avoid wrinkling and rupturing. Two different loading paths proportionate to the ram’s stroke of press unit are proposed to synchronize optimal pressure path and desired punch velocity in forming of cup-shaped products. Using the optimization approaches of constant and variable velocity, thinning values of 12.9778 and 12.3295 for a steel part with conical shape were obtained by implementing simulation iteration of 202 and 148, respectively. This result demonstrates improvement of product quality and decrease of simulation iterations in variable velocity. Appropriate conformity between numerical and experimental results verified the reliability and accuracy of the proposed optimization method.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
160
168
http://mme.modares.ac.ir/article_14612_6547646be261287f6ab596d019c54e24.pdf
Simulation of film boiling heat transfer on flat plate and the impact of various phase change models on it
Seyed Amirreza
Hosseini
دانشجوی دکتری/ دانشگاه گیلان
author
Ramin
Kouhikamali
دانشیار دانشکده فنی دانشگاه گیلان
author
text
article
2016
per
Numerical simulation of boiling has always been a challenging problem in terms of the variety and effectiveness of two-phase models. Furthermore choosing an appropriate heat and mass transfer model increases the complexity of the solution. Problem of film boiling of saturated liquid is numerically simulated in this investigation by using of VOF (volume of fluid) model together with the geo-reconstruction of interface. Three phase change models of sharp interface model, Lee model and Tanasawa model are used at the same time on a single problem in order to calculate the rate of phase change and source terms. One-dimensional Stephan benchmark is solved for verification the numerical solver. The periodic Nusselt, flow pattern, bubble form and its detachment time have been studied in mentioned various phase change models. Also empirical coefficients used in both models of Lee and Tanasawa are presented. The results of Nusselt number obtained from simulation is compared with two empirical Nusselt correlations of Berenson and Klimenko. The results show good agreement with the Klimenko’s Nusselt. The results reveal although the Lee model is dependent on empirical coefficient, it is more accurate than the two other models for prediction of film boiling on flat plate.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
169
177
http://mme.modares.ac.ir/article_14613_b3a1a6839da2d81c34ca482f17c2f883.pdf
Optimal Switching Times of Bang-Bang Controller for Uncertain Overhead Crane System
Seyed Ali
Moafi
موسسه آموزش عالی احرار
author
Mojtaba
Masoumnezhad
دانشکده شهید چمران دانشگاه فنی و حرفه ای
author
text
article
2016
per
These days overhead crane is widely used in different industries such as automobile companies, harbor, navigation and also transportation of tools in storerooms. Most of models which is done through industrial dynamic systems include some vitiated parameter with noise and disturbance which overhead crane model is not also an exception. Disturbance in system can be due to its model or measuring tool. Kalman filter is a practical method in order to recognize the model and also filtration of disordered data. By the note of that overhead crane is a nonlinear model, asymmetric sigma-point Kalman filter improved by genetic algorithm (GA-ASKF) is intended to estimate system parameters. One of common ways in controlling overhead crane parameters is using controlling force, Bang-Bang. By the way, function of Bang-Bang controller depends on controlling force switched times. In this paper, beside using this controller, its switched times is found by using genetic algorithm for noisy system. The design aim is to achieve the target point in minimum time with minimum error. Also by considering Bang-Bang controller entrance part, the article is compared situation of the system in different mass relativeness. Simulation results shows improved performance of the GA-ASKF algorithm to determine the switching time of controller and also achieving the target point in minimum time.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
178
186
http://mme.modares.ac.ir/article_14615_0fcea7a43d958d411dddd5271822ae9f.pdf
Numerical analysis of blade flutter in low-pressure turbine
Amir
Meshkati Shahmirzadi
دانشکده مهندسی هوافضا
دانشگاه صنعتی خواجه نصیرالدین طوسی
author
Saeid
Irani
عضو هیات علمی
دانشکده مهندسی هوافضا
دانشگاه صنعتی خواجه نصیرالدین طوسی
author
Mojtaba
Farrokh
استادیار دانشگاه صنعتی خواجه نصیرالدین طوسی
author
text
article
2016
per
In this paper the flutter phenomenon in turbomachinary is introduced. The importance and characteristics of the flutter as a dynamic aeroelastic instability is presented. Conventional methods for the blade flutter test and different approaches in flutter analysis of blade are described. Among the existing analysis methods, one approach which only examines the stabilizing effect of fluid is used in order to analyze the flutter in this paper. Firstly, its equations are described and a criterion for the determination of the stability based on the analysis results is presented. According to the criterion the local and global stability can be concluded. Numerical analysis has been performed by ANSYS CFX. Mesh independence and two different turbulence models have been examined and results have been validated by test results. Numerical analysis has been carried out for two steady and unsteady states. In unsteady state the response of fluid to blade vibration in three modes has been calculated. In order to assess the total response two methods have been used and the results have been compared. Eventually local instability has been calculated and the results presented in figures which illustrate the contribution of adjacent blades in instability of specific blade. The evaluation of global instability for three modes has been presented and the obtained results are in excellent agreement with experiment.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
187
198
http://mme.modares.ac.ir/article_14616_7144fa8df934bb7b8c8b8521f1e46acf.pdf
A new analytical model to study heat transfer in Borehole heat exchangers in a short time periods
Mehdi
Maerefat
هیئت علمی دانشگاه تربیت مدرس
author
Asgar
Minaei
دانشجوی دکتری مکانیک- تربیت مدرس
author
text
article
2016
per
This paper presents a new analytical model to study the thermal behavior of borehole heat exchangers (BHE) in short time periods. Transient heat transfer considered inside the borehole and at the ground around the borehole, transient heat conduction is considered inside the borehole and ground around the borehole. For this purpose, the analytical solution has been developed in two stages. First, a new analytical equation is provided for the short-time thermal response of the BHE (dimensionless G-function). In the second phase, the outlet temperature calculation using the G-function is described. Inside the borehole, the analogy between thermal and electrical conduction is used for derivation heat balance equations. For this purpose, a new equivalent thermal network for modeling of the heat transfer inside the borehole is developed. In ground around the borehole, the conduction equation in the radial direction is considered. The governing equations are solved by Laplace transform. Finally, the mean fluid temperature and short thermal response of the BHE is computed. Then in the second phase, the outlet temperature in the on and off times of the system is calculated using the G-function. The solution of the proposed analytical model is compared with experimental measurements. Results show that the outlet temperature of the analytical model matches very well with the reference experimental measurements.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
199
209
http://mme.modares.ac.ir/article_14617_cbf7d20634597798992db55ece0eb4d7.pdf
Study of formability of aluminum truncated pyramid in single-stage and two-stage incremental sheet forming
Amir Hossein
Nikdooz
مهندسی مکانیک، دانشگاه صنعتی نوشیروانی بابل
author
Mohammad Javad
Mirnia
Mechanical Engineering Department, Babol Noshirvani University of Technology
author
Hamid
Baseri
دانشیار دانشکده مهندسی مکانیک، دانشگاه صنعتی نوشیروانی بابل
author
text
article
2016
per
Incremental sheet forming has already provided distinct advantages, such as inexpensive tools and the simplicity of the process, over conventional sheet forming processes. However, the method still has some limitations. Among these limitations, severe thinning has significant effects on the performance of the final product. Also, some parts with high wall angles cannot be formed by single stage incremental forming. To overcome these restrictions, multistage incremental forming can be implemented to achieve the desired wall angle, better thickness distribution, and the lower thinning. In this study, a two-stage incremental forming of an aluminum truncated pyramid with a wall angle of 70° was studied experimentally and numerically in order to improve the achievable minimum thickness. By introducing two-stage forming strategies and achieving their defining parameters using finite element simulation, the sheet thinning was compared to the one in the single-stage forming. Experiments were used to validate the finite element analysis. The results revealed that using the two-stage forming strategy, the minimum thickness can be improved twice than the one in the single-stage forming. A good agreement was observed between the thickness distribution obtained by experiments and predicted by the finite element modeling. Finally, the effect of forming strategies on the strain paths was investigated through the finite element simulation and the experimental fracture forming limit diagram.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
210
220
http://mme.modares.ac.ir/article_14622_4318cce950bf5e275298aa2deb679bc0.pdf
The effect of secondary flows created by curved micromixers with various geometries on mixing of non-Newtonian fluids
Sima
Baheri Islami
Academic Member (Assistant professor) / University of Tabriz
author
Marzieh
khezerloo
University of Tabriz
author
Reza
Gharraei
Azarbaijan Shahid Madani University
author
text
article
2016
per
Since the majority of fluids in engineering and biologic applications are non-Newtonian, the study on mixing of non-Newtonian fluids is very important. Secondary flows are used in curved micromixers to improve the mixing of fluids. In this study, a numerical study was performed on the mixing of non-Newtonian fluids in curved micromixers using Open source CFD code of OpenFOAM. The flow was assumed three-dimensional, steady and incompressible and Reynolds numbers were between 0.1-300. Also, water and CMC solution were used for simulation of Newtonian and non-Newtonian fluid flows, respectively. The effect of Reynolds number, power-law viscosity parameters and micromixer geometry on mixing index and non-dimensional pressure drop was studied and results were compared with those of the straight channel micromixer. The results showed that the mixing index decreased by decreasing the power law index. The mixing index was high for shear thinning flows in micromixers with sharp turns. Also, by increasing the Reynolds number, and therefore velocity, centrifugal force effects increased and mixing improved. Simultaneous investigation of mixing index and pressure drop showed that for low Reynolds numbers and small power law indexes micromixer-b had better performance.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
221
230
http://mme.modares.ac.ir/article_14620_2e429106cde8eeae75240c8e874e511f.pdf
Object Orientation Detection Based on Machine Vision and Artificial Neural Network
Ehsan
Moradi
Hamedan University of Technology
author
Mehdi
Tale Masouleh
استادیار مهندسی مکاترونیک دانشکده علوم و فنون نوین دانشگاه تهران-آزمایشگاه تعامل انسان و ربات
author
Mohmmad Javad
Najari
Hamedan University of Technology
author
text
article
2016
per
This paper focuses on the problem of finding object orientation around Yaw & Pitch & Roll angels. The object orientation is computed in a real time manner using a mono-camera and three points on a solid object in a machine vision software. Three points should be selected from environment at the beginning. In order to reduce wreckful effects of environmental lights on detecting colorful objects and also to reduce the number of used software filters, IR LEDs with 850nm invisible wavelength are used. Artificial Neural Network (ANN) is used for solving this problem since orientation's equations are nonlinear and real-time solving for them is impossible. For solving the problem a feed forward artificial neural network with one hidden layer and 21 nodes in that is used, which has 3 nodes for output layer and 6 nodes for input layer. For having high accuracy in ANN, output data is also obtained from a MPU-9150 installed on a 2-DOF orientional parallel robot and compared to ANN outputs. 7243 data from Roll and Yaw angles and 751 data from Pitch angle is obtained from MPU-9150 sensor and the later 2-DOF orientional parallel robot and 467 data remains nonuse for learning ANN. After learning the neural network, results compared to nonuse data for ANN learning and desire results obtained with 0.038 maximum error
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
231
240
http://mme.modares.ac.ir/article_14621_78be3dd03ef16ba4f6b4177b6d2c3373.pdf
Design and fabrication of robotic gripper for robust grasping various objects in unstructured environments
Hamidreza
Heidari
استادیار گروه مکانیک دانشگاه ملایر
author
Milad
Jafary Pouria
دانشجوی کارشناسی دانشگاه ملایر
author
Shahriar
Sharifi
دانشجوی کارشناسی دانشگاه ملایر
author
Mahmoud Reza
Karami
دانشجوی کارشناسی ارشد دانشگاه ملایر
author
text
article
2016
per
Grasping in unstructured environments is one of the most challenging issues currently facing robotics. The inherent uncertainty about the properties of the target object and its surroundings makes the use of robot hands, which typically involve complex hands, require elaborate sensor suites, and are difficult to control. For this purpose, in this paper combining the kinematic structure of a three and two links finger for design and fabrication of robotic gripper will be evaluated. At first, the challenges associated with grasping by careful mechanical design of gripper was analyzed. Then, will be described the design and fabrication of a sample gripper with combining a three-links finger similar to the human index finger and a two-links finger similar to the thumb. In the following, the performance of this hand for grasping various objects will be examined. The results show that with two fingers and simple design, without require to the complex control can grasp various objects successfully. Also the results demonstrate that compared with the previous researches and by proximity to the kinematic structure of the human hand fingers, by combining two with three link fingers this gripper will have a better performance than the previous symmetric gripper for successful grasping large objects.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
241
250
http://mme.modares.ac.ir/article_14623_6ede1a4cda3f23e3d4595706ff837613.pdf
Application of Isogeometric Analysis and Charged System Search Algorithm in Structural Shape Optimization
Seyed Mehdi
Tavakkoli
استادیار دانشکده مهندسی عمران دانشگاه صنعتی شاهرود
author
Seyedeh Sedigheh
Mashmoul
دانشجوی کارشناسی ارشد - دانشگاه آزاد اسلامی واحد شاهرود
author
Omid
Khadem Hosseini
داشجوی دکترای سازه - دانشکده عمران - دانشگاه صنعتی شاهرود
author
text
article
2016
per
Abstract In this article, the Charged System Search (CSS) algorithm is utilized for structural shape optimization that aims to minimize weight of a plane structure under stress constraints. Also, the Isogeometric Analysis (IA) is employed in order to analyze the structure. In the IA method, Non Uniform Rational B-Spline (NURBS) basis functions are used for approximation and interpolation of the displacement field as well as modelling geometry of the structure. Coordinates of the NURBS control points, that construct the geometry, can be considered as the design variables of the shape optimization problem. In earlier studies in structural shape optimization using the Finite Element (FE) method, boundaries of the structure were made by NURBS and the finite element discretization changed when the boundaries were modified in every iteration of the optimization process. As it mentioned, when the IA method is used the geometry is constructed by NURBS, therefore, contrary to using the FE method, the need for remeshing of the domain is eliminated and the computational cost will be remarkably decreased. In this paper, the IA method is briefly reviewed for analysis of the plane-stress elasticity problems. Also, the CSS formulation is derived based on physics laws for shape optimization problems. A few examples are presented to demonstrate the performance of the method and the results are compared when the Sequential Quadratic Programming (SQP) is used as a mathematical based method for structural shape optimization.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
251
260
http://mme.modares.ac.ir/article_14640_6fcb0c30a9ab8eb7f665cbbf9307b0ae.pdf
An algorithm for prediction of die geometry effects on strength behavior of sheets fabricated by groove pressing process
Hamed
Saeidi Googarchin
عضو هیات علمی دانشگاه علم و صنعت ایران
author
Behzad
Teimouri
دانشجو
author
text
article
2016
per
In this paper, the constrained groove pressing (CGP) process of Al 5052 sheets are experimentally and numerically studied. The CGP process produces the micro-grained-size sheets to enriched strength nano-grained-size ones. The goal of this investigation is the development of an algorithm for the mechanical behavior (Strength and Hardness) prediction of the sheets fabricated by the process. The algorithm enables one to evaluate the die geometry and pressing pass definition effects on mechanical behavior of the fabricated sheet. The proposed algorithm is based on the available relation in literature between the macroscopic behavior and the grain size in metal sheets and between the hardness and the strength properties of metal sheets. The Al 5052 samples are fabricated by two passes of the CGP process. The yield strength and the Vickers hardness of the annealed, the one and two pass CGPed samples are experimentally obtained. The predicted results by the developed algorithm are in good agreement with the experimental data. The comparison of the predicted results by the algorithm with available experimental data for the mechanical behavior of the CGPed pure aluminum sheets with different dies reveals the good accuracy of the proposed algorithm. The algorithm enables one to economical save from the time-consuming experimental evaluation of groove geometry effects on the fabricated sheets and optimum die selection. The effects of the die groove angle on the yield strength and the hardness of the CGPed Al 5052 sheets are estimated using the developed algorithm.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
261
270
http://mme.modares.ac.ir/article_14641_79ce55e9ca3c606bfc56b3c144547589.pdf
Experimental and numerical investigation of crack growth in adhesive bonding of two composites plates under mode I
Amir
Kariman Moghadam
University of Birjand
author
Saeed
Rahnama
University of Birjand
author
Sattar
Maleki
Quchan University of Advanced Technology
author
text
article
2016
per
In this paper, the strain energy release rate of first mode of failure in the adhesive bonding of two composite plates composed of unidirectional glass fiber is calculated using double cantilever beam specimen. Araldite 2011 adhesive connection which is widely used in the aerospace industry has been employed. Strain energy release rate is calculated by the modified beam method, compliance calibration method and modified compliance calibration method from experimental results. For modeling crack growth in adhesive bonding of two composite plates, the Extended Finite Element Method has been employed. Average value of critical strain energy release rate calculated by the modified compliance calibration method is considered as software input. After comparing force - displacement curve obtained from experimental data and numerical solution that represents good precision of the Extended Finite Element Method in calculating the maximum force and corresponding displacement and also linear part of force-displacement curve, strain energy release rate - force curve, stress intensity factor – force curve, strain energy release rate – displacement of the load effective point and failure stress - stress intensity factor curve are evaluated.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
271
280
http://mme.modares.ac.ir/article_14642_04e770c015abf3529dd38c998c4f9b59.pdf
Simulation and strength and fatigue life improvement of adhesively bonded single lap joint using cohesive zone model with cyclic degrading
Mohammad Hassan
Shojaeefard
عضو هیئت علمی دانشگاه علم و صنعت
author
Hamed
Saeidi Googarchin
عضو هیات علمی دانشگاه علم و صنعت ایران
author
Mohammad Reza
Gheybi
دانشجوی دکتری
author
Mohammad Amin
Nikkhah
دانشجوی کارشناسی ارشد
author
text
article
2016
per
In this paper, the static stiffness and strength as well as fatigue life of adhesively bonded single lap joint (SLJ) are numerically studied using the cohesive zone model (CZM). In order to simulation of the SLJ using mixed-mode bi-linear CZM, the failure behavior of adhesive in modes II and III is considered the same. Fatigue damage propagation is simulated through scripting USDFLD Subroutine in ABAQUS/Standard. Static stiffness and strength and fatigue life obtained in this study are consistent with experimental results available in literature. Then, the effect of geometric parameters including overlap length, substrate thickness, and tapered substrates are investigated. The obtained results reveal that the increase of the overlap length would lead to increase the static strength and fatigue life prediction. While increasing substrate thickness results improved fatigue life, there are no a known relation between the static strength and substrate thickness due to the changes of the loading modes. Tapered substrates have also positive effect on the strength and fatigue life because of more compatible rotations. Therefore, to improve the strength and fatigue life of a SLJ, authors suggest greater overlap length and thickness along with tapered substrates.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
281
289
http://mme.modares.ac.ir/article_14643_8a7fae02d1aea61cbb9075ac2b8e6650.pdf
Design and Simulation of a Broadband Sonar Transducer and the Experimental Validation
Amin
Yousefi
دانشجوی کارشناسی ارشد مهندسی مکانیک دانشگاه یزد
author
Mohammad Mahdi
Abootorabi Zarchi
Assist. Prof., Mech. Eng., Yazd Univ., Yazd, Iran
author
text
article
2016
per
Knowledge of broadband transducers is a new technology in the field of sonar science. Considering that Iran has sea water resources, its importance becomes more and more. In this article, after studying the performance of the kinds of transducers in the field of sonar transducers, a proper broadband transducer with the specific impedance and acoustical characteristics that can send and receive signals, is designed, simulated, fabricated and tested. At first, overall dimension of a broadband transducer with lumped parameter model and electrical equivalent circuit model was approximated and then, with increasing the degrees of freedom of analytical models, all characteristics of the optimum transducer parts were obtained in order to have a large bandwidth. By using a finite element software (COMSOL Multiphysics), the designed model was simulated and the obtained results have been compared with analytical design solution. Finally, the transducer was fabricated and tested in order to the modeled and simulated data be validated with practical ones. The obtained experimental results showed that the simulation with COMSOL Multiphysics can predict the resonance frequency and maximum transmitting voltage response (TVR) of the broad bandwidth transducer with a reasonable precision. The prediction error of resonance frequency and maximum TVR by COMSOL is 3.8% and 5.7%, respectively. The use of lumped parameter and electrical equivalent circuit models, however, gives an initial approximation for transducer dimensions, but in determination of the resonance frequency and the frequency of maximum TVR has a higher error in comparison with the finite element method.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
290
296
http://mme.modares.ac.ir/article_14644_0671f7b90e81c247474235333e9d36f5.pdf
On fracture analysis of exploded pressure vessels and pipes
Majid
Mirzaei
دانشیار، دانشگاه تربیت مدرس
author
Saharnaz
Tavakoli
دانشجو،دانشگاه تربیت مدرس
author
text
article
2016
per
The main scope of this paper is the analysis of the specifications of deflagration-induced and detonation-induced deformation and fracture behaviors of cylindrical tubes. The main characteristics of deformation and fracture behaviors were studied through experimentations on steel pipes and failure analysis of a compressed natural gas (CNG) cylinder. The paper also reports the results of transient-dynamic elasto-plastic finite element (FE) analyses of the combustion-induced deformation and fracture behaviors of the pipe and the CNG cylinder. The FE models were composed of 3D brick elements equipped with interface cohesive elements for crack growth analysis. Very good agreements were found between the simulation results and the observed deformation and fracture patterns. It was shown that, because of different loading conditions, specific deformation and fracture features can develop during the explosion process.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
297
302
http://mme.modares.ac.ir/article_14645_0105a7ffd229f748c96023f814121abb.pdf
Experimental investigation on aerodynamic coefficients of a flying wing aircraft with different leading edge sweep angle
Mojtaba
Dehghan Menshadi
دانشیار دانشگاه صنعتی مالک اشتر اصفهان
author
Mehdi
Eilbeigi
دانشجوی دکتری
author
Mehrdad
Bazaz zadeh
دانشیار
author
Mohammad Ali
Vaziry
عضو هیات علمی
author
text
article
2016
per
The aerodynamic coefficients characteristics over a lambda-shaped flying wing aircraft with 55°-30° leading edge sweep angles have been investigated in a closed circuit low speed wind tunnel. The experiments were conducted at tunnel velocity of 90 m/s, the angles of attack of -6 to 17 and the side-slip angles of -8 to 8 degrees. All forces and moments were measured using an external six-component force balance located below the wind tunnel. The wall corrections were also performed for all test conditions. To improve the aircraft longitudinal stability characteristics, a new model with an increased leading edge sweep angle of 2 degrees were also tested and compared with the original model. A “pitch-up” phenomenon identified to occur at a rather low angle of attack of α=7.7 degrees, although it occurred at the higher angle of attack of α=8.7 degrees for the increased swept angle model which means an increase in useable lift of the aircraft. Moreover, off-surface pressure measurement over the wing surface was conducted to examine the onset and development of the flow separation over the wing surface. The results showed that the flow separation started at the trailing edge crank location and extended to the other parts of the wing, especially the outer wing.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
303
311
http://mme.modares.ac.ir/article_14670_da437141c2ff470a6bef7ea859032ed5.pdf
Numerical Simulation to improve underground room and pillar coal mine ventilation using stoppings and brattice
Ghassem
Heidarinejad
Tehran, Ale Ahmad Ave, Tarbiat Modares University, Department of Mechanical Engineering, Room 309
author
Pedram
Pakzad
Tehran, Fatemi Sq. Golha Sq. Hasht behesht St. number 17 unit 4
author
text
article
2016
per
Mine ventilation is one of the important functions in mining. The purpose of mine ventilation is providing enough oxygen to breath, create comfortable working conditions and dilute and remove the gases and dust from mine. Methane gas released from minerals while extraction in coal mines. To prevent the accumulation of this gas and intense explosions, the use of auxiliary ventilation beside main ventilation is essential. Auxiliary ventilation in room and pillar coal mining is used generally two methods of stopping and brattice.In this study, the equations of conservation of mass, momentum, species and energy is discrete by using computational fluid dynamics and the results have been validated with experimental work and then several scenarios have been predicted to improve mine ventilation. Results show that concentration of methane decreases 47 % using stoppings, but the concentration is still higher than the standard level. By using brattice the level of methane concentration decreased to 74.2%, but methane concentration in side walls of coal face is 3.4% that is still higher than the level of standard. Optimized case was simulated by using stoppings and brattice simultaneously and quality of air improved 88.8% and concentration of methane has been fully respected and mine safety and explosive gas concentration are desirable.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
312
320
http://mme.modares.ac.ir/article_14672_33da472145cec06891d827bfc958f8bc.pdf
Modeling of bubble growth behavior in the PS/CO2 batch foaming system using finite element method
Mostafa
Salehi
دانشگاه صنعتی سهند تبریز
author
Mahdi
Salami Hosseini
Faculty Member
author
Mostafa
Rezaei
عضو هیات علمی - دانشگاه صنعتی سهند
author
text
article
2016
per
Polymeric foams have a cellular structure composed of a polymeric matrix with gaseous cells which achieved by expansion of a blowing agent in polymer melt matrix during a foaming process. In the present study, the bubble expansion step in Polystyrene/CO2 batch foaming process was simulated and compared to the reported experimental results. A single spherical bubble surrounded by an incompressible viscoelastic fluid (upper-convected Maxwell model) was considered. To calculate concentration profile in the shell, mass diffusion equations were solved using finite element method, potential function definition and integral methods. The predicted results show that when the gas concentration profile obtained by finite element method and the concentration gradient near the bubble-shell interface was used to calculate the pressure inside the bubble, the predicted results were in good agreement with the experimental ones which there was less than 1% error at each foaming time. The effects of the thermo-physical and rheological properties on the bubble growth dynamics were also studied and It was found out that increasing the diffusivity coefficient by factor of 10 would increase the bubble size up to 1.5 times, whereas increasing the viscosity by 3 folds would only change the bubble size about 2% showing that the bubble growth step in foaming process was a mass transfer controlled process.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
321
328
http://mme.modares.ac.ir/article_14671_c9d076cb529c853afc521511a581a1b2.pdf
Experimental and Numerical Analysis of Fracture on Flexible Roll Forming Process of channel section in Aluminum 6061-T6 sheet
Yaghoub
Dadgar Asl
phd student/shahid rajaee teacher training university
author
Mohammad Morad
Sheikhi
دانشگاه تربیت دبیر شهید رجایی
author
Ali
Pourkamali Anaraki
Associate professor mechanical engineering/shahid rajaee teacher training university
author
Vali ollah
Panahizadeh Rahimloo
Assistant professor mechanical engineering/shahid rajaee teacher training university
author
Mohammad
Hosseinpour Gollo
Assistant professor mechanical engineering/shahid rajaee teacher training university
author
text
article
2016
per
Today, with the development of technology, industries such as automotive and construction require products with variable cross section. Multiplicity of steps, dimensional limitation and high production costs of the components caused flexible roll forming process used to produce these products. One of the main defects in this process is the fracture phenomenon. The fracture is observed on the bending edges at transition zone that sheet thickness is large compared to the bending radius. In this research the fracture phenomenon is investigated on flexible roll forming process of channel section using ductile fracture criteria. For this purpose finite element simulation of the process using Abaqus software is done. The fracture defect in this process is investigated using six ductile fracture criteria by developing a subroutine. Experimental tests are performed on 27 specimens precut sheet of AL6061-T6, using flexible roll forming machine built in Shahid Rajaee University. By comparing simulation results with experimental results, numerical results were validated. In addition, by comparing the results of ductile fracture criteria with experimental results, the Argon ductile fracture criteria, was chosen as the most appropriate criterion to predict fracture. Also the effects of parameters as sheet thickness, bending radius and bending angle on fracture with argon selected criterion is studied.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
329
338
http://mme.modares.ac.ir/article_14673_f502d3f185f0a16e2bebc86046db360d.pdf
A finite element study on the effect of the partial flexibility of the stent strut on hemodynamic parameters affecting the restenosis risk in the coronary stent deployment site
Hamed
Afrasiab
استادیار دانشکده مهندسی مکانیک دانشگاه صنعتی نوشیروان بابل
author
Bahereh
Kordrostami
دانشکده مهندسی مکانیک، دانشگاه صنعتی نوشیروانی بابل
author
text
article
2016
per
Stenting is considered to be the favoured tool for therapy of coronary stenosis disease. However, despite the many advantages of this treatment strategy, its outcome may be undermined by the restenosis occurrence in the stent deployment site. Observations have shown that stent deployment in the artery alters the hemodynamic parameters such as wall shear stress and vortices size and prepares the conditions for in-stent restenosis development. Considering this fact, in this paper, the effect of some geometrical parameters such as the shape and the size of the stent strut on the wall shear stress distribution and vortices size is investigated. Furthermore, employment of a stent with partial flexible strut is suggested to decrease the restenosis risk, and the effect of the flexible part stiffness is explored. For this purpose, the interaction between the blood flow and the flexible part is simulated by arbitrary Lagrangian-Eulerian approach in the framework of the finite element method. The results indicate that in stents with circular strut, the partial flexibility of the cross-section can be effective in reducing the restenosis risk by lowering the maximum value of the wall shear stress and considerably decreasing the vortices size. On the other hand, in stents with rectangular struts, it not only does not decrease the shear stress maximum value but also significantly increases the vortices size and may lead to increase of the restenosis risk.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
339
347
http://mme.modares.ac.ir/article_14674_1e4235b58951c27003c744ddafe724a1.pdf
The effect of journal vibration on the hydrodynamic pressure profile in a plain journal bearing
Mohammad
Hosseini
دانشگاه صنعتی سیرجان
author
Hossein
Abyar
دانشگاه آزاد اسلامی واحد سیرجان
author
text
article
2016
per
In many cases, journal vibrations in the radial direction have been observed in the various rotating machinery using journal bearing. In this investigation the effects of forced oscillation of a journal on the hydrodynamic pressure profile of a two dimensional plain journal bearing are evaluated. Gambit and ANSYS- Fluent software are used to produce mesh and simulate the flow field respectively. Fluid is Newtonian and viscosity is constant. Also, flow is laminar, isothermal, and heat transfer is neglected. It is assumed that there is no phase change and cavitation does not exist. A user defined function is written in C language and compiled by Fluent to apply the oscillation motion to the journal. Results are obtained for three non-dimensional vibration frequencies of journal (0.001, 0.1 and 1), and two eccentricity ratios (0.54 and 0.8). Results show that the hydrodynamic pressure profile is significantly dependent on the oscillation frequency of journal. It can be observed that the pressure distribution variations are independent of frequency when oscillation frequency is low. However, the pressure distribution is considerably affected by increasing oscillation frequency which leads to appearing different hydrodynamic pressure distribution. These influences become more and more intense by rising non-dimensional vibration frequency ratios specially when it is 1.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
349
356
http://mme.modares.ac.ir/article_14693_c4a7d9ee87449bc04fd370906db00b25.pdf
Tow-Dimensional Investigation of Solitary Wave Propagating over a Submerged Vertical Thin Plate with PIV Technique
Mohammad Reza
Tavakoli
Department of Mechanical Engineering- Isfahan University of Technology (IUT)
author
Reza
Zaghian
دانشکده مهندسی مکانیک
دانشگاه صنعتی اصفهان
author
Mehran
Karbasipour
دانشکده مهندسی مکانیک
دانشگاه صنعتی اصفهان
author
Mahdi
Nili
دانشکده مهندسی مکانیک
دانشگاه صنعتی اصفهان
author
text
article
2016
per
The study of wave transmission over submerged obstacles and the flow pattern that formed around the obstacle has been always an important subject because of the affect directly on wave and the changes in wave energy that is crucial in the design of devices, which absorb wave’s energy and coastal breakwaters. In this research, the flow pattern induced by solitary wave passing over a submerged vertical thin plate has been studied. A wave maker piston has been used to generate the solitary wave and particle image velocimetry (PIV) technique has been used to flow visualization that this technique is non- introsire optic method, which can measure the fluid velocity with any changes in flow pattern. The study of the flow pattern visualization, velocity values and vorticity shows, at first the flow separation shear layer forms and the clockwise vortex generate at the rear edge of the obstacle before the wave arrives to the barrier. Then the vortex grows in size and cussed the water move upward like vertical jet on upstream. Then the fluid enters to the downstream and generates the counterclockwise vortex in this region, which is less than the first clockwise vortex in power that makes an important difference with the thick geometry researches. In addition, the non-dimensional horizontal components of fluid velocity at the time of shear layer formation at the rear edge of the plate have been studied and it has been compared with the case that the barrier is rectangular.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
357
366
http://mme.modares.ac.ir/article_14675_21b4c658a5e9d174d404f92267704b3b.pdf
Numerical Study on Formation of Liquid Flow Emerging from a Capillary Emitter due to Electric Potential Effects
Hadi
Dastourani
Post- Graduate PhD Student, Aerospace Research Institute and Iranian Space Research Center
author
Mohammad Reza
Jahannama
A Member of Academic Staff and Research Deputy, Space Transportation Research Institute, Iranian Space Research Center
author
Abdollah
Eslami Majd
A member of Academic Staff, Malek Ashtar University of Technology
author
text
article
2016
per
Electrospray is a branch of the scientific area of electrohydrodynamics which is based on electrical charging of liquids. The electrospray governing equations are a combination of hydrodynamic and electrostatic equations to which the addition of liquid breakup process escalates their complexity. This research work aims at developing a numerical solver to simulate the electrospray process in an emitter-disc configuration using Heptane as a working liquid under various electrical potentials. The simulation results in comparison with CFD and experimental data show good agreements both quantitatively and qualitatively. The results clearly have captured the formation of liquid flow profiles at the emitter exit demonstrating various electrospray modes. These modes initiate a microdripping mode at the lowest voltage, i.e. 3.5kV, prompting consecutively to spindle and pulsating cone-jet modes and ending in a stable cone-jet mode at the highest charging voltage, i.e. 6.5kV. In addition, it is also observed that the liquid cone and the vortex shaped within it would shrink as an increase in the electric potential is imposed. Although the increase in electric potential results in rise of the maximum magnitudes of electric field and velocity, the electric charge accumulation at all electric potential values occurs on the outer surface of the liquid flow implying its electrical conductivity.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
367
378
http://mme.modares.ac.ir/article_14691_a524550087c7a74e75339bce55df6d9b.pdf
Multiobjective Evolutionary Optimization of Turbofan Engine Min-Max Fuel Control Algorithm
Morteza
Montazeri
دانشگاه علم و صنعت ایران
author
Saied
Mikhchin
IUS
Mech. Eng. Dept
author
Ali
Rasti
IUST
Mech Eng Dept
author
text
article
2016
per
In this paper, modeling of Min-Max controller and evolutionary multiobjective optimization for gain tuning controller of turbofan engine are presented. To achieve this purpose, first a turbofan engine is modeledin GSP software. Then engine parameters model, by using extracted GSP simulation data and based onNARX structure of neural network is developed. For model validation a test fuel signal is produced and model performance is assessed by means of it. Next, turbofan engines control requirements and constraints are described and in accordance with it a fuel controller based on Min-Max strategy is designed and diverse control loops in controller is described. Each of theseloopshas aproportionalcontroller that are knownascontrol gains of the min-max controller. Then, for determining the gains of the controller, gain tuning process is formulated as a Genetic Algorithm Optimization problem in order to GA algorithm finds the best solution by its evolutionary generations. In this optimization problem, the settling time during acceleration and deceleration, engine fuel consumption and the amount of engine emission are considered as objective functions to be minimized. The obtained results from simulation of optimized controller and engine show, the final controller not only optimizes objective functions but also satisfies all control modes of engine during acceleration and deceleration modes.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
379
388
http://mme.modares.ac.ir/article_14692_8332f95a7b50af5747d1b2e2053120f0.pdf
Production of superhydrophobic copper surfaces by fabricating micro-nano features using wet etching process
Behnam
Ahmadi
دانشکده مهندسی مکانیک،
دانشگاه علم وصنعت ایران
author
Hamid Reza
Talesh Bahrami
دانشکده مهندسی مکانیک،
دانشگاه علم و صنعت ایران
author
Hamid
Saffari
Associate Prof., Head of Department, School of Mechanical Engineering/ Iran University of Science and Technology
author
text
article
2016
per
Superhydrophobic surfaces received many applications in various industries such as desalinization, heat exchanger, anti-fog and self-cleaning surface production. In this study a wet etching process were used to produce superhydrophobic copper surfaces. The specimens were etched by multiple ferric chloride and deionized water solutions to create micro-nano structures on their surfaces. The electronic scanning electron microscopy (SEM) images of the resulted surfaces show a formation of micro-nano structures with specific templates. Contact and sliding angle measurement of surfaces after etching process show that contact angles of specimens improve to nearly 140o while sliding angle of all samples were 180o , which is the same as a rose petal property. In the next step, to promote hydrophobicity of surfaces, increase contact angle and decrease sliding angle, specimens were immersed in an ethanol and stearic acid solution with a specific concentration. As well as, effects of etching time and etchant concentration on the sliding and contact angles with/without stearic acid modification were investigated. Results show that contact angles increased and sliding angles decreased remarkably so that it reduced to lower than 10o in some cases and lotus effect were achieved.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
389
395
http://mme.modares.ac.ir/article_14694_0b71aed206998ddcc605b9f3a027b8da.pdf
Performance analysis of single and couple radiant heaters under asymmetric flow field for providing uniform conditions in an industrial environment
Mahtab
Aminzadeh
دانشجوی کارشناسی ارشد، دانشگاه بیرجند
author
Ali
Safavinejad
عضو هیات علمی گروه مهندسی مکانیک دانشگاه بیرجند
author
Seyed Alireza
Zolfaghari
عضو هیات علمی گروه مهندسی مکانیک دانشگاه بیرجند
author
text
article
2016
per
In the present study, the effect of high temperature radiant heaters’ arrangement on providing appropriate and uniform thermal conditions under asymmetric flow field have been investigated in an industrial environment. For this reason, a sample industrial environment with one inlet and outlet opening has been considered with two different types of high temperature radiant heaters’ arrangement: single radiant heater and couple radiant heaters. For the mentioned conditions, continuity equation, momentum equations, energy equation and radiative transfer equations have been solved by OpenFoam numerical solver. Also energy consumption has been evaluated in the present study. The results show that in presence of asymmetric flow field, using couple high temperature radiant heaters in comparison with single radiant heater causes more uniform temperature distribution and decrease about 10 degrees of Celsius in maximum temperature of floor. Also, this can cause to decrease about 35 percent in floor temperature distribution deviation from the average appropriate temperature (27 degrees of Celsius). Moreover, the results indicate that utilizing couple high temperature radiant heaters leads to increase in energy consumption about 10 percent in comparison with single radiant heater.
Modares Mechanical Engineering
Tarbiat Modares University
1027-5940
16
v.
5
no.
2016
396
402
http://mme.modares.ac.ir/article_14701_b8b64464ca90392a29602bd590056449.pdf