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SUMMARY:Non-linear parametrically excited systems - Bahareh Zaghari\, Univ
 ersity of Southampton
DTSTART:20160212T163000Z
DTEND:20160212T170000Z
UID:TALK63594@talks.cam.ac.uk
CONTACT:Claire Whitaker
DESCRIPTION:Abstract: Parametric amplification in cable-stayed bridges\, f
 ree hanging marine flexible risers\, ships\, and planetary gear systems ca
 n be disastrous if not accounted for. However\, parametric amplification i
 s exploited in MEMS filters\, low-noise signal amplifiers\, and micro/macr
 o vibration energy harvesters\, where amplifying the system response is be
 neficial. Parametric amplification happens when system parameters vary wit
 h an independent variable (time). As an example\, consider a person playin
 g on a swing. To maximise their height\, the person on the swing stands up
  at two extreme positions and squats down at the lowest position which cha
 nges the mass moment of inertia periodically. In this scenario\, frequency
  of parametric change is twice of the frequency of the swing. This is the 
 phenomenon of parametric resonance of a system under time-varying parametr
 ic excitation\, which happens when the excitation frequency is equal to tw
 ice of the natural frequency of the system.\nMost parametrically excited s
 ystems introduced in literature neglect the effect of nonlinearity on para
 metric amplification. We modified the electromagnetic system introduced by
  Lord Rayleigh (1887) to investigate the effect of nonlinearity on paramet
 rically excited systems. The experimental results validated the analytical
  results obtained from the averaging method. We found that hardening\, and
  positive cubic parametric nonlinearities may be beneficial for designing 
 vibration energy harvesters with a broad frequency bandwidth. We identifie
 d that negative cubic parametric nonlinearities\, with careful selection o
 f relative phase\, reduced the response amplitude\, which improves the des
 ign of mechanical vibration absorbers.\n\nAbout the authour: Mrs. Bahareh 
 Zaghari is PhD. student within the Faculty of Engineering and the Environm
 ent at the University of Southampton. Bahareh graduated with a Bachelor's 
 degree in Electronic Engineering. She got a Master's degree in Advanced Me
 chanical Engineering at the University of Southampton in 2012. In 2013\, s
 he joined ISVR to work with Dr. Maryam Ghandchi Tehrani and Dr. Emiliano R
 ustighi on parametrically excited systems.\n
LOCATION:Cambridge University Engineering Department\, Oatley Room 1
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