Search published articles
Showing 4 results for Farhid
Volume 15, Issue 7 (Supplementary Issue - 2013)
Abstract
The application of stepwise multivariate-linear regression models for determination of particleboard properties based on structural factors was studied. Poplar (Populus alba), Beech (Fagus orientaleis) and Hornbeam wood (Carpinus betulus) with dry density of 460, 630 and 790 kg/m3,respectively, were used as raw materials. Three levels of boards target density (520, 620 and 720 kg m-3) and urea formaldehyde (UF) resin (6, 7, and 8%) were compared. The variables were included in the regression equations of modulus of rupture (MOR), modulus of elasticity (MOE), shear strength, and thickness swell (TS) after 24 hours immersion based on the degree of importance. In order to obtain the optimum board density and resin content for each species, contour plots were drawn by Minitab 13 software. Regarding the results from contour plots, particleboards with density ranging from 520 to 620 kg m-3 and 6% resin had most of their mechanical properties within those required by the corresponding standards. Thickness swell values were higher than requirements. We suggest additional treatments such as using adequate amount of water resistant materials to improve TS after 24 hours immersion.
S.h. Hosseini, M. Mahboubkhah, M. Farhid,
Volume 20, Issue 8 (August 2020)
Abstract
One of the important challenges of the aerospace industry is the use of magnetic bearings and generating the electromagnetic flux in motor to increase its speed of rotation and angular momentum. In this paper, the passive magnetic bearing for the reaction wheel actuator which is used to modify the status of space satellite is designed and analyzed using the COMSOL software. The performance of constructed reaction wheel in various modes is evaluated. In the passive magnetic bearing system, when the rotor exits the center position of the rotational axis, the return force that results from repulsion between the poles of the same permanent magnet directs the rotor to the center axis position. In the paper, the axial passive magnetic bearing is designed, and the distribution of magnetic flux density and static force of the bearing is estimated using simulation in the software and the stiffness coefficient is obtained from the static properties. To reduce the power consumption of the reaction wheel, various layouts were investigated. Then, based on design and analysis results, the appropriate bearing to achieve the maximum rotational speed and the minimum power consumption is introduced. The results of the FEM analysis clarified the effects of the magnetic stacking structure on the force and magnetic stiffness of the bearing and finally, the experiments proved that the rotational speed and momentum of the reaction wheel are increased in the combined use of the mechanical and passive magnetic bearings.
M. Farhid, H. Amanpour Reyhani , H. Gouchi Esgandar , H. Beheshti Beyrami ,
Volume 20, Issue 10 (October 2020)
Abstract
In this paper, sources of micro-vibration in a reaction wheel assemblies (RWA) are analyzed in detail and their effects arising from flywheel unbalance are tested based on the related equations and by using Kistler table in Space Thruster Institute. RWAs that are used in satellites to control their situations are the major sources of instabilities leading to disturbances in the performance of instruments with high pointing precision. Thus, for the purpose of successful satellite missions, it is important to identify, study, and reduce these sources. To align with this goal, flywheel was balanced according to the equations and the requirements of the ECSS European Space Standard before assembling on the Kistler test table. With the step of 1Hz of rotation frequency, force and torque details were obtained and plotted in waterfall diagrams. These led to the verification of values obtained for static and dynamic unbalances on the graphs. The values achieved for the static and dynamic unbalances were 0.1 and 0.2gr.cm2, respectively.
Sina Akhbari, Morteza Farhid, Masoud Dehnad, Reza Golzarian,
Volume 22, Issue 9 (September 2022)
Abstract
In recent years, linear electromagnetic actuators have gained special attention in small robot actuation and calibration of milli newton thruster stands. In this paper, a linear electromagnetic actuator with a force range of milli newtons is designed and manufactured. In this regard, first the analytical relationships of the magnetic field and Lorentz force were derived and then, based on the desired design criteria meaning high force sensitivity, low heat loss and minimum geometric dimensions and weight, the appropriate design parameters of the electromagnetic actuator is obtained. According to the results, the obtained force constant is approximately 1 mN/A while the maximum power loss is 1 mW at available stroke of 10 mm. Finally, a prototype of the linear electromagnetic actuator is manufactured and experiments are performed to validate the electromagnetic actuator. For this purpose, a precision scale with an accuracy of 0.01 gr and a power supply with a resolution of 1 mA is utilized. The results showed that the maximum difference between the calculated and measured force was 2.5%. Therefore, there is a good correlation between the experimental data and the corresponding analytical values.
