טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentStarosvetsky Yuli
SubjectStudy and Optimization of Strongly Nonlinear Vibration
Absorber
DepartmentDepartment of Mechanical Engineering
Supervisor Professor Oleg Gendelman


Abstract

One of the serious problems facing engineering design is undesired vibrations which cause severe and often unpredictable damage and failures in various applications. Many investigations of past and present centuries are devoted to vibration isolation. The objective of a vibration isolation design is to prevent unwanted vibrations generated in a system from being transferred to other neighboring connected systems. Few structural examples are isolation of aero-structures, vibrating machinery, or buildings, vehicle suspensions.

Active controllers for vibration isolation are not feasible in many applications, for reasons including cost, added weight or required independent energy supply. The most well known solution of the problem is a linear vibration absorber, where an additional linear degree of freedom is added to the existing linear or weakly nonlinear main system. The linear absorber has a major drawback since it is only effective in the neighborhood of a single frequency. However, this narrowband effectiveness of the linear vibration absorber poses problems when the excitation frequency is not fixed. In this case an alternative tool for more effective vibration attenuation is a previously documented nonlinear absorber.

Current research develops the idea of the nonlinear vibration absorbers, concentrating on the case of strong nonlinearity. System under exploration in this thesis is two degrees of freedom system comprised of the main mass mounted on linear spring with a strongly nonlinear, damped attachment. The main system is excited harmonically. The main goal of the research is an analytic investigation of various system regimes (steady-state, quasi-periodic). Using the gained knowledge of various system regimes, an optimization procedure for the best vibration suppression is developed. The best tuned nonlinear absorber is compared to the linear one. Conditions under which nonlinear absorber is preferable to the linear one are revealed.