SUBJECT: Ph.D. Proposal Presentation
BY: Eric Smith
TIME: Wednesday, March 25, 2015, 11:00 a.m.
PLACE: MARC Building, 201
TITLE: Shock and Vibration Isolation Concepts Through Use of Dynamic, Multi-Degree-of-Freedom Mechanical Systems
COMMITTEE: Dr. Aldo Ferri, Chair (ME)
Dr. Alper Erturk (ME)
Dr. Michael Leamy (ME)
Dr. Wayne Whiteman (ME)
Dr. Julian Rimoli (AE)


Shock and vibration isolation continues to be an area of great interest to structural designers and to mount manufacturers. When the input disturbance is single-frequency or narrow-band, several techniques are available to limit vibration; e.g., vibration absorbers, use of active or passive damping or structural redesign. However, when the input disturbance is transient in nature or broadband, these solution strategies are of limited effectiveness. In addition to shock/vibration isolation, mounts must fulfill a number of other equally important objectives: serve as a connection between parts, be as lightweight as possible, low cost, robust, and suitable to environmental conditions.

Isolation systems are often modeled as single-degree-of-freedom (SDOF) systems, from which a qualitative picture of the design principles and tradeoffs can be viewed. Such analyses reveal that linear, lightly damped mounts are ideal in reducing high frequency transmissibility. However, this solution is unrealistic for several reasons. If the disturbance is not high frequency, but is either low-frequency or broad band, the presence of the lightly damped resonance destroys the isolation performance. Passive damping can help to control the resonant response, but this benefit comes at the expense of high-frequency isolation. Highly compliant mounts are also undesirable from a relative motion (stroke) standpoint for both static and dynamic cases. It is well known that the stroke and the isolation are inversely related- the stroke of the mount is constrained by geometry, size/weight, and functionality.

The design space of isolation systems can be greatly expanded if one considers dynamic isolation systems. Passive, dynamic mounts can be thought of as multi-degree-of-freedom (MDOF) collections of springs, masses, and dampers. Such systems can be thought of as mechanical filters that attenuate and modify the shock disturbances before the disturbance reaches the isolated component. This thesis explores several different MDOF concepts for shock and vibration isolation; some of these MDOF systems are purely translational, while others contain translational and rotational motion. It is shown that these MDOF mount designs can be very effective in accomplishing simultaneous shock and vibration isolation objectives with relatively simple, practical designs. The performance is demonstrated using both numerical simulation as well as planned experimental validation studies.