2018-03-24T20:39:42Z
http://scientiairanica.sharif.edu/?_action=export&rf=summon&issue=351
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
4
Parameter identification of a parametrically excited rate micro-gyroscope using recursive least squares method
Z.
Mohammadi
H.
Salarieh
Estimation of physical parameters of a parametrically excited gyroscope is studied in this paper. This estimation is possible by reading the input and output data of the gyroscope. Because of dierent faults in the manufacturing process and tolerances, physical parameters of a gyroscope are not exactly same as the expected values of the manufacturer. Moreover, changing of temperature, humidity, external acceleration,etc. can change the physical parameters of the gyro. Thus, the physical parameters of gyroscope are not xed values and may deviate from the desired designed values. The physical parameters of gyroscope determine the optimal region for working of gyroscope. Thus, if the parameters deviate from the original ones but the excitation frequency is fixed at its initial value, the sensitivity of the gyroscope will be reduced. The newparameters of the gyroscope can determine the new point of excitation frequency and, because of this, estimation of these parameters should be done to prevent sensitivity reduction. Estimation of these new parameters using the input and output values is studied here.
Gyroscope
Parametric excitation
Estimation
Physical parameters
Least squares method
2017
08
01
1889
2019
http://scientiairanica.sharif.edu/article_4280_8241549c0e8aaa18107a798698e15651.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
4
Surface modification of biomaterial embedded with pits using die sinker machine
D.M.
Razak
S.
Syahrullail
N.
Nuraliza
Y.
Azli
N.
Sapawe
Surface modication has been applied in many ways to enhance exclusive implant product. Electrical Discharge Machine Die Sinker (EDM DS) is a new approach to machine a macro surface on the biomaterial. In this study, investigations of current properties of EDM DS to obtain a new surface in titanium alloy (Ti-6Al-4V) and stainless steel (E-316-L), which placed pit on the material-sized (25 mm) diameter sample with a radius of 6.3 mm, were conducted. All the samples of concave textured circular pits with a fixed diameter and depth of 0.5 mm were successfully machined. This study revealed that the pits were produced in the concave cup and the lubricant was conned inside the pits, making easier contact between metal ball and metal concave surface. The results also show that the discharge machine is an attractive machining method for surface modication ofbiomaterial. This paper suggests that concave implant surface embedded with pits will work as a trap for lubricant and wear debris; in addition, it is possible to increase the lifespan of implant structure.
Surface modification
Pit
Biomaterial
Die sinker
Tribology
2017
08
01
1901
1911
http://scientiairanica.sharif.edu/article_4281_c802340d85ca777d19e6b361e04577b6.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
4
Impact crushing behavior of foam-filled paraboloid shells using numerical and experimental methods
Sh.
Shams
H.
Haddadpour
H.
Tuzandejani
S.A.A.
Hosseini
M.
Vatanparast
S.
Zahab
This paper deals with the dynamic response and energy absorption of foam-filled aluminum parabolic tubes under axial impact loading. The numerical crush analysis of empty and foam-lled tubes is performed using non-linear nite element techniques. The effects of geometrical (wall thickness) and material parameters (foam density and Young's relaxation modulus) on the impact response and energy absorption capacity of foam-filled tube are investigated using numerical models. The results show that the foam propertieshave signicant eect on the crushing behavior, force and impact acceleration magnitude, and energy absorption capacity. Furthermore, there is a critical foam density beyond which the structure loses its energy absorption performance. Experimental results acquired from a test setup are used for validating the Finite-Element Analysis (FEA). There is good agreement between numerical and experimental results.
dynamic response
Energy absorption
Impact loading
Foam-filled parabolic aluminum tube
Finite element analysis
2017
08
01
1912
1921
http://scientiairanica.sharif.edu/article_4282_9f3f75ae8d43bb025e57aa8c8e473815.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
4
Discrete mass modeling for dynamic response of buildings in the vicinity of railway tracks due to train-induced ground vibrations
M.A.
Rezvani
M.
Esmaeili
M.M.
Feizi
Annoying vibration waves generated by passing trains highlight the necessity for the assessment of the effects of railways on their environment. Dynamics of structures close to railway tracks is amongst such important issues. Contrary to the past studies, this article proposes a modeling method that is totally based on the idea of discrete masses. It considers three major parts as the accomplices causing undesirable oscillations including the track, the ground bed, and the structure in the vicinity of the track. The ground bed is considered as an elastic half space subdivided into discrete masses. It facilitates modeling for the track systems that may include any deliberate discontinuity, such as voids and trenches, in the ground bed that supports the railway track. Such discontinuities arise from engineering perception and are useful in controlling the spread of noise and vibrations. A MATLAB" based computer program is written to solve the motion equations in the timedomain. The proposed method provides flexibility in modeling. Variety of track loading and wave propagation scenarios can be simulated without the need to rebuild the model. This method can be practically used when seeking remedies for controlling the levels of unwanted vibrations in the structures.
dynamic response
Ground borne vibrations
Structural vibration
Discrete mass modeling
Vibration annoyance
Railway track
2017
08
01
1922
1939
http://scientiairanica.sharif.edu/article_4283_318d64f8f0d2133a779c77e68757671c.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
4
Particle flow simulation in a channel with symmetric protuberances using combination of lattice Boltzmann and smoothed profile methods
A.
Kouhestani
M.
Rahnama
S.
Jafari
E.
Jahanshahi Javaran
In the present study, a combination of Lattice Boltzmann Method (LBM) and Smoothed Prole Method (SPM) is used to simulate one, two, and many particles motion in a planar channel with two symmetric protuberances. LBM is applied as the fluid flow solver and SPM is used to satisfy the no-slip boundary condition at particles surfaces. Bounceback boundary conditions are used for lower and upper walls while pressure boundaryconditions are applied for the fluid inlet and outlet boundaries. Horizontal, vertical, and angular velocities of particles are recorded during the simulation. It is concluded that the combined LBM-SPM can be considered as a good candidate for simulation of particle motion in a channel with stenotic geometry.
lattice Boltzmann method
Smoothed profile method
Stenosis
Blood
Particle
2017
08
01
1940
1949
http://scientiairanica.sharif.edu/article_4284_cc51808987a53d7fd2496b9647f59636.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
4
Effect of deep sub-zero treatment on mechanical properties of AA5XXX aluminum plates adjoined by MIG welding technique
H.
Ates
A.
Tamer Ozdemir
M.
Uzun
I.
Uygur
In this study, mechanical and microstructural characteristics of AA5XXX aluminum plates connected by MIG welding were investigated. Thus, after several preliminary experiments done to ensure quality requirements of the parameters, specimens in the form of long aluminum plates were welded, and then some of them were spared for the subsequent sub-zero treatment at about 146C for 12 and 24 h, respectively. To investigate the eect of this super cooling on the welded parts, several tensile, bending, and hardness tests in conjunction with micro-structure examinations were carried out and results were discussed in detail. It was concluded that during sub-zero treatment, microstructure gets finer and stabilized, positively aecting the overall strength of the material. There is no signicant dierence in the overall strength of the material right after the subzerotreatment and that of the specimens rested for one year at room temperature after cryogenics treatments.
Aluminum alloy
Sub-zero treatment
MIG welding
2017
08
01
1950
1957
http://scientiairanica.sharif.edu/article_4285_e37531f2b44be6541d6f1fdf3531411d.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
4
Numerical study on the effect of the concave rigid boundaries on the cavitation intensity
M.T.
Shervani-Tabar
R.
Rouhollahi
In this paper, we study the motion of a cavitation bubble near a concave boundary from a theoretical perspective. To illustrate the eect of the surface concavity of the boundary, boundary integral and nite dierence methods are utilized to investigate the more detailed process of jet formation. Bubble shapes and its lifetime, movement of the bubble centroid, pressure contours, and velocity vectors are used to demonstrate thenumerical results. The velocity of a liquid jet impacting on the far side of the bubble surface tends to increase with decreasing boundary concavity. This result suggests that higher pressures can occur when cavitation bubbles collapse near a concave boundary. With the increase of boundary concavity, the time evolutions of the bubble growth and collapse tend to increase, and the liquid jet is formed later.
Cavitation bubble
Boundary integral method
Liquid jet
Velocity vector
Pressure contour
Concavity
2017
08
01
1958
1965
http://scientiairanica.sharif.edu/article_4286_d039fb294734e915d29005af37fe7f22.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
4
Unsteady impulsive oblique stagnation-point flow impinging axisymmetrically on a vertical circular cylinder with mixed convection heat transfer
R.
Bayat
A.
B. Rahimi
For the rst time, the problem of impulsive oblique stagnation-point flow on a vertical cylinder along with mixed convection heat transfer due to buoyancy forces has been solved in this study. The uid at rest with uniform temperature, T1, around the cylinder starts flowing towards it at strength rate of k, and the cylinder temperature rises to Tw at t = 0, simultaneously. The governing equations induced by the impinging flow on the constant-temperature vertical cylinder at any obliqueness angle, , have been reducedto ODEs by using similarity transformations, and then they have been solved numerically. Considering a sample case of incompressible flow with Re = 1 and Pr = 0:7, the results of Nusselt number and similarity functions of velocity and temperature distributions have been obtained for dierent values of time and angle, . At the initial instants of time, the Nusselt number, regardless of 's magnitude, has large values; for example Nu = 5:1 at = 0:01. As time passes, the value of the Nusselt number reduces intensely within ashort period of time (until 0:4), and then it changes with a moderate reduction rate, such that in the steady-state situation, its value reaches 0.67, 0.61, and 0.51 for obliqueness angles = 10, 30, 60.
Unsteady
Oblique stagnation-point flow
Axisymmetric
vertical circular cylinder
mixed convection
2017
08
01
1966
1974
http://scientiairanica.sharif.edu/article_4287_223aebe933b109b00128c02b579f1fc9.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
4
An integrated approach of quality for polymer composite manufacturing validated and optimized through Taguchi method
M.
Asim
M.
Zubair Khan
L.
Alam Khan
M.
Umer
Quality problems in the polymer composite products are mainly attributed to design flaws, material inconsistencies, defects in manufacturing process, unqualied manpower, use of primitive technology, and defective machines. The purpose of this research is to develop a generic framework of quality for polymer composite manufacturing, which is validated and optimized through determining flexure properties by Taguchimethod. To test the proposed framework, 27 polymer composite laminates were produced according to Taguchi L27 orthogonal array by varying thirteen key process parameters including laminates' thickness, weight, ber pattern, matrix, core type, resin and hardener mixing time, viscosity, layup pattern, tooling, cure, temperature, labour and process techniques. Flexure strength was dened as quality characteristic, and accordingly, effects of the selected parameters on exural properties were studied through three-point bendingtest. Results of the study reveal that ber pattern, cure, tooling type, and layup pattern are the most signicant variables influencing flexure stress, whereas ber pattern, matrix, resin hardening mixing time, and process techniques have signicant effect on flexure strain. The optimized levels of each control parameter for exure stress and strain were obtained, and results were validated through predictive analysis. Findings of this study and the proposed framework are useful for polymer composite application in aviation, mechanical, sports, automobile, and civil industries.
Quality
Flexure strength
Flexure stress
Polymer
Composite
Taguchi Method
2017
08
01
1985
1995
http://scientiairanica.sharif.edu/article_4288_9cb72c820f32af1419f4ee1331d45336.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
4
Effect of size dependency on in-plane vibration of circular micro-rings
A.
Karimzadeh
M.T.
Ahmadian
M.
Rahaeifard
In this paper, based on the modied couple stress theory, the size-dependent dynamic behavior of circular rings on elastic foundation is investigated. The ring is modeled by Euler-Bernoulli and Timoshenko beam theories, and Hamilton's principle is utilized to derive the equations of motion and boundary conditions. The formulation derived is a general form of the equation of motion of circular rings and can be reduced to the classical form by eliminating the size-dependent terms. On this basis, the size-dependent natural frequencies of a circular ring are calculated based on the non-classical Euler-Bernoulli and Timoshenko beam theories. The ndings are compared with classical beam theories. Response of the micro-ring under application of static and dynamic loads is investigatedand compared with the classical theories. Results show that when the thickness of the ring is in the order of the length scale of the ring material, the natural frequencies evaluated using the modied couple stress are considerably more than those predicted based on the classical beam theories, while the defection and natural frequencies of the classical and non-classical beam theories approach one another for the rings with thickness much larger than the material length scale.
Micro-ring
Modified couple stress theory
Resonant frequency
2017
08
01
1996
2008
http://scientiairanica.sharif.edu/article_4289_eca7975567c65d8ea81dce22fa990a34.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
4
Kinetics of reduction and oxidation reactions during pyrometallurgical metal extraction
S.
Borozova
S.
Jursova
P.
Pustejovska
J.
Bilik
The article deals with a sophisticated approach to the study of basic kinetic dynamic process in metal production. It is concerned with three agendas: study of reduction reactions of iron oxides and carbon as reducing agents with secondary created oxides; study of the eect of catalyst occurrence on the reaction space; study of the effect of variable temperature and pressure gradients on the processes. The main experimentswere carried out in the newly established Laboratory for Research on High Temperaturev Properties equipped with testing setup and upgraded with interpretive model system, enabling a generalization of experimentally obtained information to theoretical conclusions about processing of non-standard alternative and waste materials.
Pyrometallurgical extraction
Testing of reduction
Kinetic model
Iron oxides
Chemistry engineering application
2017
08
01
2009
2018
http://scientiairanica.sharif.edu/article_4290_f534b8d814d65b44214b6fb8da438fee.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
4
Surface tension simulation of free surface flows using smoothed particle hydrodynamics
M.
Ordoubadi
M.
Yaghoubi
F.
Yeganehdoust
SPH method is one of the most used numerical mesh-free methods in CFD simulations which can easily model problems with free surfaces. Considering the importance of surface tension in most engineering applications and the capability of SPH method in simulating free surfaces, a single-phase method for implementing surface tension is introduced in this study. Unlike time-consuming multi-phase simulations, this methoddoes not need to model the second lighter fluid, which reduces the CPU-time and memory requirements substantially. Mirror imaginary particles are used near the free surface to obtain surface properties such as surface normal vector and curvature, which are required in surface tension calculation. The advantages of using these imaginary particles are explained qualitatively through the use of some examples of droplet dynamics. This method is applied to several benchmark problems in surface tension simulations, and acceptable results are obtained.
SPH method
Free surface flows
Surface tension
Continuum surface force
2017
08
01
2019
2033
http://scientiairanica.sharif.edu/article_4291_46e365935a544e6609dc57682f4cae8e.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2017
24
4
Submicron particle deposition in pulmonary alveoli during cyclic breathing
M.
Monjezi
M.S.
Saidi
G.
Ahmadi
The prediction of deposition eciency of submicron particles in the pulmonary alveoli has received special attention due to its importance for drug delivery systems and for assessing air pollutants health risks. In this work, the pulmonary alveoli of a healthy human are idealized by a three-dimensional honeycomb-like conguration and a fluid-structure interaction analysis is performed. In contrast to previous works in which the inlet ow rate is predened, in this model, a negative pressure is imposed on the outside surface of the alveolus which causes air to flow in and out of the alveolus. The resulting flow patterns conrmed that there was no circulation in the terminal alveolus. The predicted alveolar air flow was used to calculate the trajectories of submicron particles using the Lagrangian approach. Our ndings suggest that an accurate simulation requires including at least ten breathing cycles, considering a parabolic radial distribution of injected particles andcontinuous injection. The presented results show high deposition eciency for submicron sizes in the alveolar region if these particles can reach the alveolar region. Therefore, the vesicles technology in which particle agglomerates would be released after the vesicle reaching the alveoli is suggested for targeted drug delivery to the alveolar region.
FSI
Particle deposition
Cyclic breathing
Difiusion
2017
08
01
1975
1984
http://scientiairanica.sharif.edu/article_4292_175b181263b1a1ca7ae20f227065f542.pdf