DESIGN PROCEDURES FOR SHOCK ISOLATION SYSTEMS OF UNDERGROUND PROTECTIVE STRUCTURES. VOLUME 2. STRUCTURE INTERIOR MOTIONS DUE TO DIRECTLY TRANSMITTED GROUND SHOCK

This paper investigates the use of finite 1:1 dimer chains to mitigate the transmission of shock disturbances. Dimer chains consist of alternating light and heavy masses with interconnecting compliance. Changing the mass ratio has provided interesting results in previous research. In particular, in the case of Hertzian contacts with zero-preload, certain mass ratios have revealed minimal levels of transmitted force. This paper examines this phenomenon from the perspective of utilizing it in practical isolation systems. The zero-preload Hertzian contact case is contrasted with chains connected by linear or cubic springs. Through numerical simulations, tradeoffs are examined between displacement and transmitted force. Parametric studies are conducted to examine how isolation performance changes with mass ratio, stiffness, and different chain lengths.

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Optimization of Linear, Nonlinear and Active Multidegree-of-Freedom Shock Isolation Systems Klein, G. H. Univ. Calif., 271 pp (1971): Refer to Abstract No. 71-1671

The Shock and Vibration Digest ◽

10.1177/058310247200400416 ◽

1972 ◽

Vol 4 (4) ◽

pp. 82-82

Author(s):

C.A. Mercer

Keyword(s):

Shock Isolation ◽

Isolation Systems

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Analytical and Experimental Investigation of Buckled Beams as Negative Stiffness Elements for Passive Vibration and Shock Isolation Systems

Journal of Vibration and Acoustics ◽

10.1115/1.4026888 ◽

2014 ◽

Vol 136 (3) ◽

Cited By ~ 87

Author(s):

Benjamin A. Fulcher ◽

David W. Shahan ◽

Michael R. Haberman ◽

Carolyn Conner Seepersad ◽

Preston S. Wilson

Keyword(s):

Resonance Frequency ◽

Vibration Isolation ◽

Negative Stiffness ◽

Peak Acceleration ◽

Single Beam ◽

Buckled Beams ◽

Buckled Beam ◽

Double Beam ◽

Shock Isolation ◽

Isolation Systems

The behavior of a buckled beam mechanism, which exhibits both bistability and negative stiffness, is investigated for the purposes of passive shock and vibration isolation. The vibration and shock isolation systems investigated in this research include linear, positive stiffness springs in parallel with the transverse motion of buckled beams, resulting in quasizero stiffness behavior. For vibration isolation systems, quasizero stiffness lowers the resonance frequency of the system, thereby reducing its transmissibility at frequencies greater than resonance. For shock isolation systems, quasizero stiffness provides constant-force shock isolation at tailored force levels, thereby enabling increased capacity for absorbing shock energy relative to a comparable positive stiffness system. Single- and double-beam configurations that exhibit first-mode buckling are utilized for vibration isolation, and a single beam that exhibits first- and third-mode buckling is used for shock isolation. For all cases, the static and dynamic behavior of each configuration is modeled analytically. The models are then used to design prototype vibration and shock isolation systems that are fabricated using selective laser sintering (SLS). The dynamic behavior of the systems in response to base excitations is determined experimentally, and the results are compared to model-based predictions. The vibration isolation prototypes display isolation levels that are tunable by varying the axial compression of the beams. Double-beam systems are shown to provide greater reductions in resonance frequency than single-beam systems for comparable levels of axial compression. However, low-frequency isolation capabilities are sensitive to the high levels of precision required to obtain low levels of system stiffness. The shock isolation prototype provides isolation at prespecified threshold levels of force or acceleration. In the prototype system, an input shock with a peak acceleration of approximately 7 g is reduced to a peak acceleration of the isolated mass of approximately 1 g. High levels of negative acceleration are observed in models and prototype systems when the buckled beam snaps back to its original position; however, models indicate that large negative accelerations can be mitigated using one-way dampers.

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Shock Isolation in Finite-Length Dimer Chains With Linear, Cubic and Hertzian Spring Interactions

Volume 8: 22nd Reliability, Stress Analysis, and Failure Prevention Conference; 25th Conference on Mechanical Vibration and Noise ◽

10.1115/detc2013-13229 ◽

2013 ◽

Author(s):

Eric Smith ◽

Al Ferri

Keyword(s):

Numerical Simulations ◽

Numerical Investigation ◽

Finite Length ◽

Hertzian Contact ◽

Mass Ratio ◽

Transmitted Force ◽

Mass Ratios ◽

Shock Isolation ◽

Isolation Systems

A numerical investigation to mitigate the effects of shock in finite 1:1 dimer chains is performed. Dimer chains consist of alternating light and heavy masses. Changing the mass ratio has provided interesting results in previous research. In particular, in the case of Hertzian contacts with zero-preload, certain mass ratios have revealed minimal levels of transmitted force. This paper examines this phenomena from the perspective of utilizing it in practical isolation systems. The zero-preload Hertzian contact case is contrasted with chains connected by linear or cubic springs. Through numerical simulations, tradeoffs are examined between displacement and transmitted force.

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