Applied Mathematics and Mechanics (English Edition) ›› 2016, Vol. 37 ›› Issue (10): 1375-1392.doi: https://doi.org/10.1007/s10483-016-2138-9

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Vibration and wave propagation analysis of twisted micro-beam using strain gradient theory

M. MOHAMMADIMEHR, M. J. FARAHI, S. ALIMIRZAEI   

  1. Department of Solid Mechanics, Faculty of Mechanical Engineering, University of Kashan, Kashan 87317-53153, Iran
  • 收稿日期:2016-01-26 修回日期:2016-05-10 出版日期:2016-10-01 发布日期:2016-10-01
  • 通讯作者: M. MOHAMMADIMEHR E-mail:mmohammadimehr@kashanu.ac.ir
  • 基金资助:

    Project supported by the Iranian Nanotechnology Development Committee and the University of Kashan (No.463855/11)

Vibration and wave propagation analysis of twisted micro-beam using strain gradient theory

M. MOHAMMADIMEHR, M. J. FARAHI, S. ALIMIRZAEI   

  1. Department of Solid Mechanics, Faculty of Mechanical Engineering, University of Kashan, Kashan 87317-53153, Iran
  • Received:2016-01-26 Revised:2016-05-10 Online:2016-10-01 Published:2016-10-01
  • Supported by:

    Project supported by the Iranian Nanotechnology Development Committee and the University of Kashan (No.463855/11)

摘要:

In this research, vibration and wave propagation analysis of a twisted microbeam on Pasternak foundation is investigated. The strain-displacement relations (kinematic equations) are calculated by the displacement fields of the twisted micro-beam. The strain gradient theory (SGT) is used to implement the size dependent effect at microscale. Finally, using an energy method and Hamilton’s principle, the governing equations of motion for the twisted micro-beam are derived. Natural frequencies and the wave propagation speed of the twisted micro-beam are calculated with an analytical method. Also, the natural frequency, the phase speed, the cut-off frequency, and the wave number of the twisted micro-beam are obtained by considering three material length scale parameters, the rate of twist angle, the thickness, the length of twisted micro-beam, and the elastic medium. The results of this work indicate that the phase speed in a twisted micro-beam increases with an increase in the rate of twist angle. Moreover, the wave number is inversely related with the thickness of micro-beam. Meanwhile, it is directly related to the wave propagation frequency. Increasing the rate of twist angle causes the increase in the natural frequency especially with higher thickness. The effect of the twist angle rate on the group velocity is observed at a lower wave propagation frequency.

关键词: twisted micro-beam, vibration and wave propagation analysis, strain gradient theory (SGT), rate of twist angle

Abstract:

In this research, vibration and wave propagation analysis of a twisted microbeam on Pasternak foundation is investigated. The strain-displacement relations (kinematic equations) are calculated by the displacement fields of the twisted micro-beam. The strain gradient theory (SGT) is used to implement the size dependent effect at microscale. Finally, using an energy method and Hamilton’s principle, the governing equations of motion for the twisted micro-beam are derived. Natural frequencies and the wave propagation speed of the twisted micro-beam are calculated with an analytical method. Also, the natural frequency, the phase speed, the cut-off frequency, and the wave number of the twisted micro-beam are obtained by considering three material length scale parameters, the rate of twist angle, the thickness, the length of twisted micro-beam, and the elastic medium. The results of this work indicate that the phase speed in a twisted micro-beam increases with an increase in the rate of twist angle. Moreover, the wave number is inversely related with the thickness of micro-beam. Meanwhile, it is directly related to the wave propagation frequency. Increasing the rate of twist angle causes the increase in the natural frequency especially with higher thickness. The effect of the twist angle rate on the group velocity is observed at a lower wave propagation frequency.

Key words: strain gradient theory (SGT), vibration and wave propagation analysis, rate of twist angle, twisted micro-beam

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