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RISS 인기검색어
- 검색키워드
- 저자 : Mehrdad Poursina (검색결과 5 건)
- 무료
- 기관 내 무료
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An analytical determining the internal ring gear rim stiffness for practical purpose
Saeed Tavassoli,Mehrdad Poursina,Davood Poursina 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.10
Internal ring gears have a wide application in planetary gearboxes and transmission systems. The mesh stiffness of planetary gearboxes is an essential parameter for dynamic and vibration analysis. No direct practical method for calculating the stiffness of the internal ring gear rim has been investigated yet to the authors' knowledge. For the first time in this research, a practical method is presented to determine the stiffness of the internal ring gear rim with an appropriate accuracy based on strain energy. To accomplish this goal, every part of the internal ring gear rim, which is between two consecutive pins or bolts, is modeled as a curved beam. The deflection of the curved beam is determined according to Castigliano's theorem. Then, the stiffness of the internal ring gear rim is obtained through this deflection. Fourier’s series of deflections are calculated to make analytical results more comfortable to use. Finally, the analytical results are validated by FEM using ABAQUS software.
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Mohsen Rezaei,Mehrdad Poursina,Shahram Hadian Jazi,Farhad Haji Aboutalebi 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.8
Time-dependent mesh stiffness is a most important reason of vibration and dynamic excitation in gear sets. In this research, analytical formulas of the helical gear set and the planetary gear system are combined to calculate the time-dependent mesh stiffness of the helical planetary gear system. For this purpose, at the first step, the analytical equations are derived for the spur gear pair. Then by dividing a helical tooth into the several independent thin spur tooth slices, the helical gear pair mesh stiffness is extracted. Finally, these equations are extended to the helical planetary gear system. The suggested analytical results and those which obtained by the finite element method (FEM) are compared and are in good agreement when the helix angle is less than 15 degrees. Also, the helical planetary gear system mesh stiffness in different cases such as fixed carrier, fixed sun gear and fixed ring gears is calculated. These results show that the value of mesh frequency ratio in each case scales the mesh stiffness shapes in the rotation angle direction. In other words, mesh frequency ratio parameter determines the number of meshing period in each rotation of planets.
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Multi crack detection in helical gear teeth using transmission error ratio
Mohsen Rezaei,Mehrdad Poursina,Shahram Hadian Jazi,Farhad Haji Aboutalebi 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.3
Gear systems are used to transmit power in the industry when accuracy and synchrony are needed and helical gear systems are used in more accurate and high-speed industries. It is important to ensure that these systems work faultlessly, therefore the detection of the crack location and situation is very efficient in the gear systems. In this research, a new approach is proposed to detect the multi crack location and length in the helical gear teeth. To this end, after giving an explanation of helical gear mesh stiffness and demonstrating the helical gear pair dynamic modeling, the transmission error ratio method is used to detect the cracks locations and lengths. Then, according to solved examples, when the cracks locations are far enough that their effects on the transmission error are completely separated, the cracked teeth and the lengths of cracks can be detected exactly, and when the cracks are in adjacent teeth, according to the cracks lengths and depths and their effects overlap, the number of cracks and their lengths can be detected exactly, approximately or absolutely undetectable.
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A Study on Fracture Locus of St12 Steel And Implementation Ductile Damage Criteria
Mohammad Khataei,Mehrdad Poursina,Mahmoud Kadkhodaei 한국소성가공학회 2010 기타자료 Vol.2010 No.6
In a metal forming process, the state of stress is one of the most important parameters on forming and behavior of the material. According to ductile damage criteria, the magnitudes of fracture strain for various stress triaxiality values should be determined for prediction of the place and time of ductile fracture. In this paper, the magnitudes of fracture strain of St12 steel is measured using several tensile tests on notched samples. Johnson-Cook equation for fracture strain as a function of stress triaxiality is calibrated for St12 steel, using the obtained experimental data. The accuracy of this function is achieved by comparison of the FEM results with experimental data which are achieved during simple tension and Erichsen tests. The simulation results have shown that the ductile damage model is a suitable criterion for prediction of fracture in St12 steel. In addition, notched samples tensile tests are suitable for calibration of Johnson-Cook equation for St12 steel.
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The effect of anisotropy on wrinkling of tube under rotary draw bending
Kourosh Hasanpour,Mahmoud Barati,Behnaz Amini,Mehrdad Poursina 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.3
Rotary draw tube bending is one of the most complex tube forming processes subject to different process parameters such as mate-rial properties and geometry. This process is being practiced in more and more applications in industry due to its high efficiency, high forming precision and quality. However, improper process parameters can lead to wrinkling which restrict the thin walled tube bending. Therefore, the prediction and prevention of wrinkling is very important. Despite its importance, the effect of anisotropy on the occurrence of wrinkling was not considered in the literature up to now. In this investigation, a quantitative study on the wrinkling of thin walled tube bending is carried out through a finite element model of the process using velocity integral parameter, which is used for the detection of wrinkles. The other methods usually warn the wrinkling initiation with no precise location prediction. In addition, the effects of some process parameters, specially normal and planar anisotropy on the tube wrinkling are investigated. It is shown that increasing normal and planar anisotropy (increasing r0 and r90 values) result in a decrease in tube wrinkling.
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