2019-01-22T07:51:56Z
http://ijstm.shirazu.ac.ir/?_action=export&rf=summon&issue=234
Iranian Journal of Science and Technology Transactions of Mechanical Engineering
2228-6187
2228-6187
2012
36
1
FEM simulation and experimental validation of flash-less cold forging for producing auv propeller blade
Manufacturing of the Autonomous Underwater Vehicle (AUV) is a challenge for researchers because of the hazardous ocean environment. The propeller is the most complex part in AUV because of its elaborately shaped blade designed to increase the thrust. The selection of the manufacturing process, flash-less cold forging die design and optimization of the work-piece are the major issues to reduce the overall cost of the propeller. Numerous investigations have been carried out in this area by many researchers using various tools and techniques. However, cold forging of complex geometries such as the propeller blade is still lacking. Moreover, volumetric analysis and optimization of work-piece have not been reported so far for complex geometries. In this work, the cold forging process is adopted to produce the propeller blade. Three-dimensional finite element (FE) analysis and experimental flash-less cold forging of aluminum blade of the AUV propeller is presented. The work-piece used is of AISI AL6061 and the die material is die steel (AISI D2).Based on the simulation results, the flash-less cold forging is successfully done on a 100 ton C-type machine.
Autonomous under water vehicle
cold forging
FEM
flash-less
under-filling
2012
04
28
1
12
http://ijstm.shirazu.ac.ir/article_883_c3eeb60e4b4d35d62d929af1e38a629e.pdf
Iranian Journal of Science and Technology Transactions of Mechanical Engineering
2228-6187
2228-6187
2012
36
1
Molecular dynamics simulation of melting, solidification and remelting processes of aluminum
A molecular dynamics simulation study has been performed to investigate the solidification and remelting of aluminum using Sutton-Chen many body potential. Different numbers of atoms from 108 to 2048 atoms were considered to find an adequate size for the system. Three different cooling and heating rates, i.e. 10<sup>12</sup> K/s, 10<sup>13</sup> K/s and 10<sup>14 </sup>K/s, were used. The structure of the system was examined using radial distribution function. The melting and crystallization temperatures of aluminum were evaluated by calculating the variation of heat capacity during the phase transformation. Additionally, Wendt–Abraham parameters were calculated to determine the glass transition temperature. It is shown that the melting temperature of aluminum increases as the heating rate increases. During solidification, a crystalline or amorphous-like structure is formed depending on the cooling rate. Remelting of the amorphous solidified material is accompanied by crystallization before melting at heating rates <10<sup>14</sup>K/s. The melting temperature also depends on the degree of structural crystallinity before remelting.
molecular dynamics
rapid solidification
remelting
metallic glasses
aluminum
2012
04
28
13
23
http://ijstm.shirazu.ac.ir/article_884_730996b7278e2fa74ea4701e6844f9a0.pdf
Iranian Journal of Science and Technology Transactions of Mechanical Engineering
2228-6187
2228-6187
2012
36
1
Towards implementation and autonomous navigation of an intelligent automated guided vehicle in material handling systems
Automated Guided Vehicles (AGV) have been a conventional solution and choice made by many manufacturing enterprises as means for Flexible Material Handling Systems (FMHS). In recent years, a considerable number of these vehicles have been installed on shop floors worldwide, effectively proving the usefulness of material handling systems. However, the increasing complexity of demand as well as a need for “make to order” rather than “make to stock” policy implies usage of more intelligent material handling solutions. This paper discusses the usage of an intelligent AGV as means for FMHS which should have Intelligent Material Handling System (IMHS) as the final outcome. This paper presents the experimental results of hybrid robotic control architecture. To evaluate the performance of the architecture, a mobile robot built on LEGO<sup>®</sup> Mindstorms NXT technology was used. Some of the architectural modules are based on the implementation of Artificial Neural Networks in order to achieve the needed robustness in exploitation. Then, through simulation using AnyLogic<sup>®</sup>6 software, the performance in terms of manufacturing system effectiveness and workstation utilization is analyzed. Based on the experimental results, the proposed IMHS can have significant advantages over conventional material handling systems.
Flexible material handling system
intelligent automated guided vehicle
Artificial Neural Networks
discrete event simulation
2012
04
28
25
40
http://ijstm.shirazu.ac.ir/article_885_2b1276effc8089df77eb155124271e05.pdf
Iranian Journal of Science and Technology Transactions of Mechanical Engineering
2228-6187
2228-6187
2012
36
1
Use of augmented continuum theory for modeling the size dependent material behavior of nano-actuators
In this paper, an augmented continuum mechanics is applied to investigate the size dependent pull-in instability of torsional nano-electromechanical actuator considering the coupling effect between torsion and bending. A set of dimensionless governing equations of the system is derived using the effective size dependent flexural and torsional rigidity of the actuator. The governing equations are solved using implicit function theorem. The static instability parameters i.e pull-in angle, pull-in displacement and pull-in voltage are computed as a function of bending/torsion coupling ratio as well as the actuator geometrical characteristics and size effect parameter. It is found that pull-in characteristics computed by the augmented continuum mechanics has a considerable difference with those predicted via classical theory when the dimensions of the nano-actuator are of the order of the internal material length scale parameter.
Augmented continuum theory
electrostatic torsional actuator
pull-in instability
torsion/bending coupling
2013
01
28
41
52
http://ijstm.shirazu.ac.ir/article_886_dd59c02767b38a561b556c8b611c6910.pdf
Iranian Journal of Science and Technology Transactions of Mechanical Engineering
2228-6187
2228-6187
2012
36
1
Simultaneous effects of brownian motion and clustering of nanoparticles on thermal conductivity of nanofluids
In this paper, Brownian motion of nanoparticles and clusters and resulted micromixing are combined with the aggregation kinetics of clusters to capture the effects of nanoparticles on the thermal conductivity of nanofluids. Starting from kinetic theory, random motion of nanoparticles and induced micro-convection were combined with the kinetics of aggregates and a theoretical model which depends on two semi-empirical parameters was derived. The proposed model attributes the thermal conductivity of nanofluids not only to the intrinsic physical properties, but also to physicochemical parameters which affect the stability state of nanofluids. The more nanofluid is stabilized, the more <em>k</em><sub>eff</sub>increases. We have also demonstrated that the thermal conductivity either increases or decreases with respect to the particle size and there is an optimum value for the particle radius at which the thermal conductivity of the nanofluid is maximum. Depending on the chemistry of the solution, the optimized radius of the nanoparticles in a suspension depends on the temperature and pH of the suspension and the volume fraction of the nanoparticles. This behaviour is not feasible without including the effects of aggregation kinetics combined with Brownian motion and induced micro-convection.
Nanofluids
Brownian motion
thermal conductivity
heat transfer
2012
04
28
53
68
http://ijstm.shirazu.ac.ir/article_887_6944efedab2965c13ed21d621f24fa61.pdf
Iranian Journal of Science and Technology Transactions of Mechanical Engineering
2228-6187
2228-6187
2012
36
1
Numerical simulation of a buoyant suspending drop in plane couette flow: the equilibrium position of the drop
The lateral migration of a two-dimensional buoyant drop in simple shear flow is studied numerically. For a <span style="font-size: x-small;">slightly</span><span style="font-size: x-small;"> buoyant drop, the drop migrates to an equilibrium position which is close to the walls </span><span style="font-size: x-small;">depending</span><span style="font-size: x-small;"> on whether the drop leads or lags the flow. If the drop is relatively more buoyant, the equilibrium position moves back to the midplane. The equilibrium position of the drop depends on the Froude number of the flow. The behavior has been investigated for various Froude numbers. The equilibrium position also depends on the drop deformation. When the Capillary number is raised, the equilibrium position moves away from the wall. At relatively large Capillary numbers, the drop shape is not stable, and the equilibrium position shows small oscillations due to an unstable drop shape. The effect of the Reynolds number on the equilibrium position has also been studied by a few simulations. It is found that at a relatively large Reynolds numbers (<em>Re<sub>h</sub></em> = 80) and a moderate Froude number (<em>Fr</em> = 160) the drop oscillates with a finite amplitude inside the channel. The equilibrium position of the drop agrees qualitatively with perturbation theories and numerical results available for solid particles. </span>
Non-neutrally buoyant drop
Shear flow
density ratio
capillary number
Froude number
Reynolds number
2012
04
28
69
82
http://ijstm.shirazu.ac.ir/article_888_2fe6f77ca1dfe1f4d731c8306ebd9f40.pdf
Iranian Journal of Science and Technology Transactions of Mechanical Engineering
2228-6187
2228-6187
2012
36
1
How to find spatial periodic orbits Around the moon in the tbp
Finding special periodic orbit in the highly chaotic problems is very complicated. Thus, deriving an effective algorithm for finding such orbits is important. In this paper, the spatial orbits in three-body problems are studied. Then, an algorithm is derived in order to help to find these orbits. This algorithm includes scanning the space, refining better points, and finally, minimizing the position error of the orbit by means of numerical methods.
Restricted three body problem
periodic orbits
algorithm
chaotic orbit
2012
04
28
83
93
http://ijstm.shirazu.ac.ir/article_889_338cfe82dd45a98b6ad29f5d36b2030f.pdf
Iranian Journal of Science and Technology Transactions of Mechanical Engineering
2228-6187
2228-6187
2012
36
1
Computer simulation of fast hydraulic actuators
Mathematical model of fast hydraulic actuator dynamics, based on Riemann’s equations, is presented in the paper. Fast hydraulic actuator can be assumed as two serially connected compressible fluid flows controlled by supply and return variable flow restrictors enclosed in control servo-valve and separated by actuator piston. Exhibited dynamic model includes several physical effects, such as: fluid viscosity and compressibility, compression and expansion, wave propagation, actuator equivalent inertia, potential external load and arbitrary servo-valve control input. Solution of the presented mathematical model is evaluated by using the method of characteristics. Corresponding boundary conditions assume the actuator piston position as a movable boundary between the direct and the reverse part of the actuator chamber.
Compressible fluid flow
fast hydraulic actuator
characteristics
Riemann’s equations
Wave propagation
2012
04
28
95
106
http://ijstm.shirazu.ac.ir/article_890_83849e7981461484e75e93cfe4c5ab50.pdf