טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentShiroky Itzhak
SubjectEssentially Nonlinear Vibration Absorber in Parametrically
Excited Systems
DepartmentDepartment of Mechanical Engineering
Supervisor Professor Oleg Gendelman
Full Thesis textFull thesis text - English Version


Abstract

Parametric excitation is a dynamic phenomenon that may cause disastrous failure in various mechanical structures. Unlike external excitation, parametric excitation is an instability phenomenon. Therefore, unbounded solutions exist for particular values of amplitude and frequency of excitation, making it much tougher to fight.

Few methods exist to suppress undesired vibrations. The active absorber is rather effective for wide band of frequencies. However, its high cost, additional weight and a required energy source make it not feasible in many applications. The linear passive absorber is significantly cheaper and doesn't require any energy supply. Practically, this is an additional degree of freedom attached to the main structure. The main drawback of the linear passive absorber is its narrowband effectiveness. An alternative solution for the problem is the nonlinear passive absorber that was proved to be rather effective for a wider range of frequencies. The latest research has shown that a relatively small but strongly nonlinear attachment causes an irreversible transfer of energy from the main structure in an externally forced system.

The current work examines the performance of the strongly nonlinear attachment in a parametrically excited system. Dynamic behavior of the system is analyzed and the conditions for the various regimes of oscillation are found. The effect of the attachment on the system's region of stability is investigated. Restrictions on span of the initial conditions bring about essential improvement of the absorber performance. Regimes and conditions, optimal for the vibration absorption, are revealed.