2019-12-08T02:43:30Z
http://admt.iaumajlesi.ac.ir/?_action=export&rf=summon&issue=114655
ADMT Journal
2252-0406
2252-0406
2016
9
2
Experimental Investigation of the Flow Control of Wake Cylinder by a Plate with Different Geometrical Ends
A.B.
Khoshnevis
AmirReza
Mamouri
AmirReza
Mamouri
V.
Barzenoni
An experimental study was carried out on the wake of a cylinder on the back of which a plate is installed parallel to the fluid flow, with different terminal angles, where the Reynolds number is 50000. At the end of the plate, blades with the height of 0.25 equal to the cylinder diameter and with 45, 90 and 135 degrees angle from the horizon, are installed where the cylinder diameter is equal to the plate length. The plate effects on the variation of drag coefficient, medium velocity profiles, reduced velocity, half of the entrance, turbulence intensity and Strouhal number are investigated. The results showed that the drag coefficient for cylinder including the plate, regardless of the end angle, is smaller than the isolated cylinder. The existence of a plate with a terminal angle of 45 degree led to more reduction in drag coefficient of the cylinder.
Cylinder
Drag coefficient
Strouhal number
Turbulence intensity
2016
06
01
1
10
http://admt.iaumajlesi.ac.ir/article_534963_9722337c2aea5576c1b5a87cf030a62c.pdf
ADMT Journal
2252-0406
2252-0406
2016
9
2
Energy Absorption by Thin-Walled Tubes with various Thicknesses in Rectangular and Square Sections under Different Quasi-Static Conditions: Experimental and Numerical Studies
K. Hoseini
Safari
Y.
Mohammadi
Sajjad
Dehghanpour
Impact is one of the most important subjects which always have been considered in mechanical science. Nature of impact is such that which makes its control a hard task. Therefore it is required to adopt a safe and secure mechanism for transferring the impact to other vulnerable parts of a structure, when it is necessary. One of the best methods of absorbing impact energy is using Thin-walled tubes, where the tubes collapse under impact by absorbing energy, while this prevents the damage to other parts. Purpose of the present study is to survey the deformation and energy absorption of tubes with different type of cross section (rectangular or square) and with similar volumes, height, mean cross section, and material under different speed loading. Lateral loading of tubes are quasi-static type and in addition to the numerical analysis, also experimental experiment has been performed to evaluate the accuracy of the results. Results from the survey indicates that at the same conditions which mentioned above, samples with square cross sections, absorb more energy compared to rectangular cross sections; also by increasing the loading speed and thickness, the energy absorption would be more..
energy absorption
In-plane loading
LS-DYNA
Quasi-Static
2016
06
01
11
18
http://admt.iaumajlesi.ac.ir/article_534964_24407bd4e35326c9c98a7dbac1ad421b.pdf
ADMT Journal
2252-0406
2252-0406
2016
9
2
The Effects of Local Variation in Thermal Conductivity on Heat Transfer of a Micropolar Fluid Flow Over a Porous Sheet
Reza
Keimanesh
Cyrus
Aghanajafi
This study is considering a micropolar fluid flow over a porous stretching sheet in the presence of thermal radiation and uniform magnetic field. The effects of local variation in thermal conductivity of micropolar fluid on heat transfer rate from the sheet are investigated; besides, the impacts of radiation, magnetic field and porous sheet on variations of thermal boundary layer thickness are considered. The results show that the increase of thermal conductivity thickens thermal boundary layer, so heat transfer rate decreases. In addition, intensification of magnetic field and the presence of radiation lower the absolute values of temperature gradient on the wall, and reduce the cooling rate of the sheet. On the contrary, the increase of suction and material parameter has positive influence on cooling rate of the sheet.
magnetic field
Micropolar fluid
Radiation
Thermal conductivity
2016
06
01
19
25
http://admt.iaumajlesi.ac.ir/article_534965_8f3668d0ac0d54893c054f02e9fb1e89.pdf
ADMT Journal
2252-0406
2252-0406
2016
9
2
Investigation of Mechanical Property and Microstructure of Nanocomposite AZ31/SiC Fabricated by Friction Stir Process
ahmad
haghani
Sayed Hassan
Nourbakhsh
Mehdi
Jahangiri
The friction stir process (FSP) is a solid state process, which has been used to insert reinforcing particles into the structure of a material to create a composite with improved properties. Magnesium is a light structural metal that is increasingly used in the aerospace and automobile industries. In this research, SiC nanoparticles were added to AZ31 alloy using FSP in two overlaps of 100% and 50% passes. In 100% pass overlapping, nanoparticles were added in 4, 8 and 16 volume percentages and in 50% pass overlapping only nanoparticles in 4 volume percent were added. The FSP process performed as 4 consecutive passes in both overlaps along with rapid cooling. Microstructure, hardness and tensile strength of created composites were examined. The results suggested that adding reinforcing materials causes reduction in the size of the grains, uniformity of structure and increase in the hardness of material. SiC nanoparticles distributed uniformly through the AZ31 alloy. By increasing volume fraction of reinforcing materials, yield stress of the material increased but ultimate stress and formability properties reduced. In 50% overlapping state, the yield stress in directions, either parallel or perpendicular to the pin direction, increased rather than 100% overlapping state, but the ultimate stress and elongation properties reduced. This reduction was greater in the perpendicular direction relative to the pin direction.
Friction stir process
Magnesium AZ31
Mechanical strength
SiC nanoparticles
2016
06
01
27
34
http://admt.iaumajlesi.ac.ir/article_534966_9503f159fa169d689c0caa8aaeb181c8.pdf
ADMT Journal
2252-0406
2252-0406
2016
9
2
Development of Boundary Layer of Highly Elastic Flow of the Upper Convected Maxwell Fluid over a Stretching Sheet
Meysam
Mohamadali
Nariman
Ashrafi
High Weissenberg boundary layer flow of viscoelastic fluids on a stretching surface has been studied. The flow is considered to be steady and two dimensional. Flows of viscoelastic liquids at high Weissenberg number exhibit stress boundary layers near walls. These boundary layers are caused by the memory of the fluid. Upon proper scaling and by means of an exact similarity transformation, the non-linear momentum and constitutive equations of each layer transform into the respective system of highly nonlinear and coupled ordinary differential equations. Effects of variation in pressure gradient and Weissenberg number on velocity profile and stress components are investigated. It is observed that the value of stress components decrease by Weissenberg number. Moreover, the results show that increasing the pressure gradient results in thicker velocity boundary layer. It is observed that unlike the Newtonian flows, in order to maintain a potential flow, normal stresses must inevitably develop in far fields.
Boundary layer
High weissenberg flow
Nonlinear viscoelastic fluid
Similarity solution
2016
06
01
35
44
http://admt.iaumajlesi.ac.ir/article_534967_3b32ac425be0e3a17bce9f9f85d07df1.pdf
ADMT Journal
2252-0406
2252-0406
2016
9
2
Investigation of The Effects of Process Parameters on The Welding Line Movement in Deep Drawing of Tailor Welded Blanks
Ali
Fazli
In this paper, the deep drawing process of tailor welded blanks is simulated using the finite element modelling and verified using the experimental results available in the literature. Then the effect of die and material properties on the welding line movement is investigated. It is seen that the most effective material parameters on weld line movement are different between sheet metal thicknesses and strength coefficient of two welded sheets. Also it is seen that the most effective die parameter on weld line movement is the friction coefficient between punch and blank. Finite element simulations show that in the wall section of the drawn cup, the welding line moves toward the material with smaller thickness and lower strength coefficient while in the bottom of the drawn cup, the welding line moves toward the material with larger thickness, and higher strength coefficient. Based on the results, increasing the friction coefficient between blank and die, decreases the welding line movement considerably.
Deep drawing process
Tailor welded blanks
Welding line movement
2016
06
01
45
52
http://admt.iaumajlesi.ac.ir/article_534968_578f1574c891bd4bbd51a7d13e4f0734.pdf
ADMT Journal
2252-0406
2252-0406
2016
9
2
Numerical Investigation of Laser Bending of Perforated Sheets
Mehdi
Safari
Mehdi
Ebrahimi
In this work, laser bending of perforated sheets has been investigated numerically. Laser bending of perforated sheets is more complicated than non-perforated sheets due to their complex geometries. In this paper, laser bending of perforated sheets is studied numerically in the form of thermo-mechanical analysis with ABAQUS/IMPLICIT code. For this purpose, the effects of process and sheet parameters such as laser output power, laser scanning speed, laser beam diameter and the number of punches in the sheet are investigated on the bending angle of laser formed perforated sheet. The results show that the larger punch diameters lead to decrease in bending angle in the laser formed perforated sheets. Also, it is concluded that the bending angle of the perforated sheet is decreased with increasing laser scanning speed. In addition, bending angle is decreased with decreasing laser beam diameter.
Bending angle
Laser bending
Perforated sheets
2016
06
01
53
60
http://admt.iaumajlesi.ac.ir/article_534969_e25e7aa3f4aebfa6fd06a21deab9b401.pdf
ADMT Journal
2252-0406
2252-0406
2016
9
2
Experimental Study on Surface Roughness and Flatness in Lapping of AISI 52100 Steel
Masoud
Farahnakian
H.
ُُShahrajabian
Lapping is one of the most important polishing processes which can be used to fabricate flat and smooth surfaces. In this paper, the effect of lapping characteristics and mesh number of abrasive particles are studied on the surface roughness and flatness for the machining of hardened AISI 52100 rings. The most significant lapping characteristics are pressure, lap plate speed and time. Scanning electron microscopy and optical microscopy are used to investigate micro cracks and surface textures. Results showed that surface roughness increased by rising the lapping pressure and plate speed. Also, reduction of the lapping time and mesh number of abrasive particles led to lower surface roughness. Application of lapping process decreased the flatness to 1.2 µm and surface roughness (Ra) from 0.58 to 0.051 µm. The lapping pressure was a significant factor on the surface roughness; and the lapping time was a significant factor on flatness. However, surface roughness increased with rising of mesh number and lapping time, and increased with decreasing the lapping pressure. The minimum surface roughness was 0.051 μm which was obtained in lapping pressure of 7 kPa, lapping speed of 0.164 m/s, time of 15 min and mesh number of 600.The flatness decreased with lapping speed, and reduced with increasing the pressure, mesh number and lapping time.
ANOVA
Flatness
Hardened steel
Lapping
Surface Roughness
2016
06
01
61
68
http://admt.iaumajlesi.ac.ir/article_534970_2b1c2d79477c20481ecb7ad5a6ea90a5.pdf
ADMT Journal
2252-0406
2252-0406
2016
9
2
Evaluation of γ-Al2O3/n-decane Nanofluid Performance in Shell and Tube Heat Recovery Exchanger in a Biomass Heating Plant
Navid
Bozorgan
Maryam
Shafahi
The performance of a γ-Al2O3/n-decane nanofluid shell-and-tube heat exchanger in a biomass heating plant is analyzed to specify the optimum condition based on the maximum heat transfer rate and performance index for wide range of nanoparticle volume fraction (0–7%). Compared with pure n-decane, the obtained results in this research show that by using γ-Al2O3/n-decane nanofluid as coolant at optimum values of particle volume concentration for maximum heat transfer rate (ϕ=0.021) and for maximum performance index (ϕ=0.006), the heat transfer rate and pumping power increased by 10.84%, 13.18% and 6.72%, 2.3%, respectively. Increasing particles concentration raises the fluid viscosity, decreases the Reynolds number and consequently decreases the heat transfer coefficient. As a result, determining the optimum value of the particle volume fraction of nanofluid as the working fluid, can improve the performance of shell-and-tube heat exchangers.
heat transfer
Nanofluid
pressure drop
Shell and Tube Heat Exchanger
2016
06
01
69
77
http://admt.iaumajlesi.ac.ir/article_534971_c3a78d6e1b8ae8db2fc91cb0c2b19384.pdf
ADMT Journal
2252-0406
2252-0406
2016
9
2
Investigation on Stress Distribution of Functionally Graded Nanocomposite Cylinders Reinforced by Carbon Nanotubes in Thermal Environment
Mohammad morad
Sheikhi
Hamidreza
Shamsolhoseinian
Rasool
Moradi dastjerdi
In this paper, stress and displacement fields of functionally graded (FG) nanocomposite cylinders reinforced by carbon nanotubes (CNTs) subjected to internal pressure and in thermal environment are investigated by finite element method. The nanocomposite cylinders are combinations of single-walled carbon nanotubes (SWCNTs) and isotropic matrix. Material properties are estimated by a micro mechanical model (Rule of mixture), using some effective parameters. In this simulation, an axisymmetric model is used; uniform and four kinds of linear functionally graded (FG) distributions of CNTs along the radial direction is assumed, in order to study the stress distributions. Effects of the kind of distribution and volume fraction of CNT and also, thermal environment, and geometry dimension of cylinder are investigated on the stress and displacement distributions of the FG nanocomposite cylinders. It is shown that, CNTs distribution and environment temperature are important factors on the stresses distribution of the nanocomposite cylinders.
Carbon nanotubes
Finite element method
Functionally graded
Nanocomposite cylinders
stress distribution
2016
06
01
79
91
http://admt.iaumajlesi.ac.ir/article_534972_9af681e79862a6a1f98174643d7f005c.pdf
ADMT Journal
2252-0406
2252-0406
2016
9
2
Effect of Welding Parameters on Microstructure and Mechanical Properties of Friction Stir Spot Welded of Titanium Alloy TiAl6V4
Saeid
Nader
Masoud
Kasiri- Asgarani
kamran
amini
Morteza
Shamanian
In this study, friction stir spot welding (FSSW) is applied to join the TiAl6V4 titanium alloy with 1.5 mm thickness and then the effect of rotational speed and tool dwell time on microstructure and mechanical properties is investigated. In this regard, the speed of the tool rotation was considered as 800, 1000, and 1200 rpm, as well as the tool dwell time was set at 7 and 12s. Microstructural evaluation was carried out using optical microscopy (OM) and scanning electron microscopy (SEM). In addition, tensile-shear and hardness studies were performed to analyze mechanical properties. The obtained results from microstructural evaluation show that the welded joints consist of two regions, namely the SZ and the HAZ-regions. Additionally, microstructure of the SZ-region was identified in the form of α/β layer within the initial β-phase. The results of tensile/shear tests and micro-hardness test indicated that the joint strength and hardness are enhanced with increasing the rotational speed and dwell time. The tensile/shear strength is increased from 2.7 to 15 KN with increasing the rotational speed at constant dwell time of 7s, and also is increased from 7.3 to 17.25 KN with increasing the rotational speed at constant dwell time of 12s. The maximum tensile/shear strength was achieved for the welded joint with the dwell time of 12s and rotational speed of 1250 rpm. The hardness of SZ, HAZ regions and base metal are measured around 380 to 420, 340 to 380, and 300 to 340, respectively.
Dwell time
Friction stir spot welding
Rotation speed
Titanium alloy
2016
06
01
93
100
http://admt.iaumajlesi.ac.ir/article_534973_86d3c2012b0addcc74820040ba943853.pdf