
text
article
2012
per

Modares Mechanical Engineering
Tarbiat Modares University
10275940
12
v.
2
no.
2012
0
0
http://mme.modares.ac.ir/article_1486_a6868c440523fe8e6bca18626525b87c.pdf
Constant and Variable Assuming Strain Rate Methods for Identification of Constitutive Model of Metals Using Hopkinson Pressure Bar Test
Hassan
Shokrollahi
M. Sc., Mechanical Engineering Department, Iran Univ. of Science and Tech.
author
M.
Sedighi
School of Mechanical Engineering
Iran University of Science and Technology
author
Mehrdad
Khandaei
Ph. D., Mechanical Engineering Department, Iran Univ. of Science and Tech.
author
text
article
2012
per
In the present paper, the parameters of Johnson  Cook (JC) constitutive model for two steels have been identified, based on the Hopkinson pressure bar test results. The experimental data has been taken from the split Hopkinson pressure bar data found in the literature. Using the measured strain pulses, the experimental stress  strain and deformation  time curves can be extracted. The experimental data have been processed using two different methods. In the first method strain rate assume to be constant during deformation and in the other one the deformation has been applied to a modeled specimen. In each method, an optimal set of material constants for JC constitutive model have been computed by minimizing the standard deviation of the numerically obtained stress  strain curve from the experimental data. Also a sensitivity analysis has been performed on JC constitutive model parameters and temperature changes during test have been investigated. The obtained results show that using constant strain rate method, leads to considerable error in results; for example in this study the minimum error is about 14%.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
12
v.
2
no.
2012
1
10
http://mme.modares.ac.ir/article_1472_5eb1ad97e27bd79d804a6f84fb00dfc6.pdf
Analytical Modelling of perforation of projectiles into Glass/Epoxy Composites
Mohammad
Pol
PhD Student
author
غلامحسین
لیاقت
استاد دانشگاه تربیت مدرس
author
text
article
2012
per
In this paper an analytical model for investigating of the ballistic impact behavior of two dimensional woven Eglass/epoxy composites is presented on the basis dividing the impact duration to several time intervals and calculating the energy absorbed during each time interval. The major components of energy lost by projectile during ballistic impact are identified, namely the cone kinetic energy formed on the back face of the target, the secondary yarns deformation energy, the tensile failure energy of primary yarns, the delamination and matrix cracking energy. It is assumed that the shear plug formation is not observed for glass reinforced composites and the energy lost in overcoming the frictional force between projectile and composite is negligible. Analytical formulations have been presented for calculating energy absorbed by each mechanism in each time interval. Finally, a good correlation has been observed, comparing the analytical model presented in this paper to the experimental results presented by others investigators.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
12
v.
2
no.
2012
11
19
http://mme.modares.ac.ir/article_1473_bf2e34a5fc1acfb41977788836ff0d27.pdf
Modeling of Depressed Center Wagon and Optimization of Its Suspension for Transporting of High Weight Transformers on Straight Rail in Vertical Direction
محسن
حاجی زین العابدینی
دانشگاه آزاد اسلامی واحد تهران جنوب
author
حبیب الله
ملاطفی
هیئت علمی / دانشگاه علم و صنعت ایران
author
حسن
ظهور
استاد تمام دانشکده مهندسی مکانیک دانشگاه صنعتی شریف
author
محسن
درگزی
کارشناس مرکز تحقیقات راه آهن ایران
author
text
article
2012
per
Abstract In this study, first the six axle depressed center wagon modeled with computer then its suspension optimized for transporting of high weight transformers in vertical direction on straight rails . For this purpose, We simulate dynamics of depressed center wagon in two ways,one by ADAMS / Rail software and by newtoneuler analysis Dynamics method. Nonlinear equations of motion and kinematical constraints have been solved in time domain. Then we define parameters that are influence on dynamics behavior of suspension element of the six axle depressed center wagon. In addition, optimization function defined base on Non Operating Shock Specification (NOSS) factor that is factor of Vulnerability when carry transformer. And in the end, suspension of this wagon optimized for Transporting of Transformers by perform many simulations on variation interval of choice parameters. Results show that stiffness of suspension element must change a little to dynamics behavior of depressed center wagon is improved.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
12
v.
2
no.
2012
20
29
http://mme.modares.ac.ir/article_1474_c6066991485660d5383b027c9ca673c8.pdf
Dynamic Modeling of a Solar Adsorption Refrigeration System
علی
بهبهانی نیا
عضو هیئت علمی
author
مهسا
صیفی کار
خواجه نصیرالدین طوسی
author
text
article
2012
per
This article presents a transient model of a solar adsorption cooling system. A computer program is developed to simulate the operation of a twobed silica gel water adsorption cooling system as well as flat plate collectors and the hot water storage tank. This program is then utilized to simulate the performance of a sample solar adsorption cooling system used for cooling a set of rooms that comprises an area of 52 m2 located in Ahwaz city in Iran. The results include the temperature profiles of hot, cooling and chilled water in addition to adsorption/desorption beds, evaporator and condenser, collector hot water temperature, auxiliary heater fuel consumption and solar fraction of the system. Furthermore, the effect of the cycle time on COP (coefficient of performance), SCP (Specific Cooling Power), refrigeration capacity, fuel consumption and solar fraction is studied. The results show that the cycle time increases COP and SF of the cycle but decreases cooling capacity and supplementary heater fuel consumption.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
12
v.
2
no.
2012
30
44
http://mme.modares.ac.ir/article_1475_33b12c16f0ff37e45451086b8cc0ed5b.pdf
Analysis and optimization of betatype Stirling engine taking into account the nonideal regenerator thermal
and hydraulic losses effects
مسعود
ضیاء بشرحق
دانشیار دانشکده مکانیک دانشگاه صنعتی خواجه نصیر طوسی
author
mostafa
mahmoodi
عضو هیات علمی دانشگاه
author
text
article
2012
per
Abstract In this paper, numerical solution of betatype Stirling engine was presented considering its nonideal regenerator. To this end, the secondorder model including thermal and hydraulic losses of regenerator was used and their effect on the output power and efficiency of the engine was obtained. Then, a numerical code was used for calculating dimensional and functional optimum values of regenerator. To confirm the obtained result, the functional and geometrical parameters of the engine made by General Motors Corporation called GPU3 were used. According to the obtained results, the values of hydraulic and thermal losses in the regenerator were considerable and led to the decrease in the engine power and efficiency by 23% and 8%, respectively. Using the obtained results and numerical code, the amounts of porosity, frequency and length of the regenerator were suggested as less than 0.7, 35 Hz and 24 mm, respectively, in the optimum physical and geometrical conditions of the engine.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
12
v.
2
no.
2012
45
57
http://mme.modares.ac.ir/article_1476_3c57ad8d691fdc4795ecb96a96e1f810.pdf
Numerical Modeling of Shrinkage of a Ceramic Material in Drying Process
خلیل
خلیلی
هیات علمی دانشگاه بیرجند
author
محسن
حیدری
دانشجوی تحصیلات تکمیلی/دانشگاه بیرحند
author
text
article
2012
per
In the present study the phenomenon of drying a clay brick ceramic is analyzed. Strain–Stress equations coupled to heat and mass transfers during drying of deformable twophase media has been modeled and both 2D and 3D arrangements have been studied. In order to compare the results, two samples with identical compositions are used for both configurations. The material is considered as a twophase, homogeneous, isotropic, and highly shrinkable medium. The principal equations of the model, because of the shrinkage behavior are written in a Lagrangian formulation. The model is solved numerically by a finite difference method and Validation of results is achieved by comparing the numerical results with experimental data. The model being developed allows the derivation of the time and space moisture contents, strains, and stresses incurred as a result of drying. A significant difference was observed between the results obtained for the two different configurations particularly in intensity of the stress causing cracking
Modares Mechanical Engineering
Tarbiat Modares University
10275940
12
v.
2
no.
2012
58
71
http://mme.modares.ac.ir/article_1477_3b8f270fdd479fd91ac5f665ada16b99.pdf
Optimization of a 10Stage Axial Flow Compressor Using Streamline Curvature Method with Respect to Aerodynamic Criteria
alireza
fathi
دانشجو
author
Abdollah
Shadaram
استاد/دانشگاه صنعتی خواجه نصیر
author
text
article
2012
per
This paper has been presented a new method for optimum design of multistage axial flow compressor blades considering overall performance and stage matching. This tool is made up of an optimization algorithm, a flow solver and a parametric geometry generation system. A twodimensional streamline curvature code has been improved to evalute the compressor performance parameters and flow field. Design parameters consist of geometrical parameters and aerodynamic performance parameters include the minimum loss of blade and allowable range of incidence. The efficiency increment of a 10stage compressor has been investigated to evaluate the proposed method. The geometry of three front stages of compressor is fixed, the geometry of three middle stages is optimized and four rear stages have been restaggered. At the first, compressor is optimized by redesigning middle stages and second, it is optimized by redesigning middle stages and restaggering rear stages. In best case, compressor efficiency has been improved by 1.18 in nominal speed and 1.83 percent in 95% of nominal speed.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
12
v.
2
no.
2012
72
86
http://mme.modares.ac.ir/article_1478_a1a987d45eb7c7bc97c2844d940c746b.pdf
Optimal path planning of nonholonomic mobile robots Using optimal control method and verification of the method via experimental tests of the Scout mobile robot
محرم
حبیب نژاد کورایم
استاد
author
مصطفی
ناظمی زاده
دانشگاه صنعتی امیرکبیر
author
حسین
غفارپور
کارشناسی ارشد
author
text
article
2012
per
nonholonomic mobile robots are widely used in industrial environments due to their extended workspace. Also, to increase the productivity and efficiency of the mobile robot, their path planning is an important task, and is attracted attention of many of robotic scientists. In this paper, the optimal path planning of the wheeled mobile robots are performed considering their nonlinear dynamic equations and the nonholonomic constraints. Problem of the trajectory optimization is formulated, and conditions of the optimality are derived as a set of nonlinear differential equations by means of indirect method of optimal control method. Then, the optimality equations are solved numerically, and variant simulations are executed. To verify the simulation study, some experimental analysis are done for the Scout mobile robot and compared to the simulation results. The experimental analysis verifies the simulation results, and demonstrates the applicability of the proposed method for the optimal path planning of the mobile robots.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
12
v.
2
no.
2012
87
94
http://mme.modares.ac.ir/article_1479_8d1b4440dc760da2386e372db01b161d.pdf
Effect of nanoparticles on mixed convection heat transfer in a horizontal channel with heat source
ایمان
پیشکار
دانشجو دانشگاه شهرکرد
author
behzad
ghasemi
هیات علمی دانشگاه شهرکرد
author
text
article
2012
per
ABSTRACT A numerical investigation of mixed convection heat transfer with nanofluid and pure water from a heat source in a horizontal channel is performed. The walls of the channel are adiabatic and the heat source is placed at the bottom wall of the channel. Free flow at cold temperature enters channel and takes heat from heat source. Discretization of the continuity, momentums and energy equations are achieved through a finite volume method and solved with SIMPLE method. The Brownian motion of nanoparticles is simulated to determine the thermal conductivity of the nanofluid.The results show that using the nanofluid caused to heat diffusion and average temperature of source to increase. Also, increase in solid volume fraction causes increase in heat transfer especially at high Reynolds number. It is understand that with increase in ratio of length to height of source in its constant area, heat transfer decreases first and then increases.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
12
v.
2
no.
2012
95
108
http://mme.modares.ac.ir/article_1480_145a5b25214aafd0b55e4c6c38d87d07.pdf
Performance Improvement of a Centrifugal Compressor Using a Developed Inverse Design Method
Mahdi
Nili Ahmadabadi
Dept. of Mechanical Engineering, Isfahan Univ. of Tech.
author
Farzad
Poursadegh
Sharif University of Technology
author
Majid
Shahhosseini
Design Dept. Manager, Oil Turbo Compressor Equipment
author
text
article
2012
per
In this research, the aerodynamic design of a centrifugal compressor is carried out using an inverse design method. At the first step of the aerodynamic design, the shape modification capability of compressor meridional plane is generated by linking up the BallSpine inverse design algorithm as a shape modification algorithm and quasi 3D analysis code as a flow solver. Then, the meridional plane is modified by improving the hub and shroud pressure distribution and applying it to the inverse design code. At the second part of this research, by developing a novel design method on the blade to blade plane, and incorporating it into the quasi 3D flow solver, the 3D profiles of impellers will be obtained in order to reach the higher blade loading. Finally, to check the outcome of design process, the current and the modified impellers are analyzed using the full 3D flow solver, CFX. The results are the representatives of about 5 percent enhancement in compressor total pressure ratio.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
12
v.
2
no.
2012
109
124
http://mme.modares.ac.ir/article_1481_6f8a5366c812ed08cadd6e0dee023f02.pdf
The effect of various parameters on breakup length of the outflow from the nozzle
Soudeh
khosravi
Tarbiat Modares University
author
mohamadreza
ansari

author
text
article
2012
per
Abstract: in this article, jet flow from the nozzle exit was considered and calculated numerically in transient twophase flow and twodimensional axsymmetric turbulent condition using volume of fluid method (VOF). The hydrodynamical instability for jet flow was analyzed and the breakup length was calculated, the nozzle diameter of 0.11875mm, 0.2375mm and 0.475 mm, the center line velocity of the fluid in the 15.416 m/s and 7.708 m/s and the fluid inside the nozzle used for the calculation are water and gas oil. Fluent 6.3.26 was used for twophase flow analysis. The results obtained from the present numerical simulation compared with the experimental results of the previous researches, good agreement was obtained. It was concluded that the breakup length decreases as the relative velocity between the phases increase or the liquid density decreases. The nozzle diameter is an important parameter which effect of the nozzle outlet regime and the breakup length.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
12
v.
2
no.
2012
125
133
http://mme.modares.ac.ir/article_1482_a507d5f58cebf64efe5a1851fe349810.pdf
Vibroacoustical Optimzation of Mechanical Structures Using Geometry Modification Concepte and Genetic Algorithm Method
Mostafa
Ranjbar
Assistant Professor, Department of Mechanical Engineering, Pardis Branch, Islamic Azad University,Pardis, Iran
author
Steffen
Marburg
Professor, LRT, Institut für Mechanik, Universität der Bundeswehr München, 85577 Neubiberg, Germany.
author
text
article
2012
per
This paper introduces a new approach for the reduction of sound radiation from the mechanical structures. A combination of genetic algorithm method and geometry modification concept minimizes the root mean square level of structure borne sound for a square plate over a specific frequency range. The structure’s local geometry modification values at the selected surface keypoints considered as design variables. The model is under three nonsymmetric harmonic excitations. An iterative approach is used to develop new modified model until when a termination criterium is rached. The results show that this approach could produce significant reduction in the value of radiated sound power level of the structure.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
12
v.
2
no.
2012
134
143
http://mme.modares.ac.ir/article_1483_f66093697b7074f611722d801d8e4c07.pdf
Heat and Mass Transfer in a Porous Enclosure in the Presence of Biochemical Heat Source
Mohsen
Nazari
Assistant Prof. of Mechanical Eng.
Shahrood Univ. of Technology
author
محمد حسن
کیهانی
دانشگاه صنعتی شاهرود
author
اسماعیل
شاکری نژاد
دانشگاه صنعتی شاهرود
author
text
article
2012
per
In the present study, natural convection in a porous cavity in the presence of a nonisothermal biochemical heat source is investigated numerically. The porous cavity is assumed to be homogenous and the Darcy model is used for the momentum equation. The porous cavity includes two species namely biomass and substrate. The heat source generated in the cavity is equal to the rate of consumption of the substrate by the biomass. The biochemical source in the energy equation is proportional to the generation rate of solute concentration governed by a Monod model. Heat generation in the porous media, the rate of consumption of a substrate by a biomass, temperature distribution in the cavity, and the local Nusselt number are analyzed completely. The effect of porosity on the biochemical process is completely analyzed in this paper. Results showed that increasing the porosity leads to an increase in the biochemical heat generation in the cavity.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
12
v.
2
no.
2012
144
152
http://mme.modares.ac.ir/article_1484_2c6504a89f030806e8259b1f470f3d18.pdf
A new model to estimate the Young's modulus of polymer concrete using micromechanical relations
محمود مهرداد
شکریه
دانشکده مهندسی مکانیک، استاد
author
مجتبی
الهی
کارشناس ارشد
author
text
article
2012
per
This research is dedicated to the estimation of the effective elastic modulus of polymer concrete by a new micromechanical model. The capability of the equivalent inclusion methods have been proved by numerous researches. The MoriTanaka (MT) model is the most used homogenization scheme for twophase composite materials. The MT model provides good estimates of the stiffness tensor for twophase composites with low to moderate volume fraction of inclusions. However, when the volume fraction of reinforcing phase is high, MT model is unable to predict the stiffness tensor accurately. The major disadvantage of MT model is that when volume fraction is high, in the associated isolated inclusion medium (AIIM), the properties of the reinforcing phase does not affect the matrix properties. The idea of the proposed model is that in high volume fraction of the associated isolated inclusion medium, the matrix phase must be affected by the reinforcing phase properties. In order to evaluate this model, twelve components with two different compositions were manufactured and tested. Also, the results from other researches were used to evaluate this model. The validation of the proposed model with the experimental data and results by other researchers shows the remarkable predictive capability of this model.
Modares Mechanical Engineering
Tarbiat Modares University
10275940
12
v.
2
no.
2012
153
162
http://mme.modares.ac.ir/article_1485_94fcc92228f296e84a2261a4547b746e.pdf