Vibration isolation from irregularity in a nearly periodic structure: Theory and measurements

1983 ◽  
Vol 74 (3) ◽  
pp. 894-905 ◽  
Author(s):  
C. H. Hodges ◽  
J. Woodhouse
Keyword(s):  
Periodic Structure ◽  
Vibration Isolation ◽  
Structure Theory

Broadband Vibration Isolation for Rods and Beams Using Periodic Structure Theory

2018 ◽  
Vol 86 (2) ◽  
Author(s):  
Rajan Prasad ◽  
Abhijit Sarkar
Keyword(s):  
Periodic Structure ◽  
Vibration Isolation ◽  
Periodic Structures ◽  
Stop Band ◽  
Extreme Case ◽  
Unit Cell ◽  
Structure Theory ◽  
Seismic Excitations ◽  
Stiffness Properties ◽  
Selection Of

The alternating stop-band characteristics of periodic structures have been widely used for narrow band vibration control applications. The objective of this work is to extend this idea for broadband excitations. Toward this end, we seek to synthesize a longitudinal and a flexural periodic structure having the largest fraction of the frequencies falling in the attenuation bands of the structure. Such a periodic structure when subjected to broadband excitation has minimal transmission of the response away from the source of excitation. The unit cell of such a periodic structure is constituted of two distinct regions having different inertial and stiffness properties. We derive guidelines for suitable selection of inertial and stiffness properties of the two regions in the unit cell such that the maximal frequency region corresponds to attenuation bands of the periodic structure. It is found that maximal dissimilarity between the neighboring regions of the unit cell leads to maximal attenuating frequencies. In the extreme case, it is found that more than 98% of the frequencies are blocked. For seismic excitations, it is shown that large, finite periodic structures corresponding to the optimal unit cell derived using the infinite periodic structure theory has significant vibration isolation benefits in comparison to a homogeneous structure or an arbitrarily chosen periodic structure.

Development of a general SEA subsystem formulation using FE periodic structure theory

2008 ◽  
Vol 123 (5) ◽  
pp. 3058-3058
Author(s):  
Vincent Cotoni ◽  
Phil S. Shorter ◽  
Robin S. Langley
Keyword(s):  
Periodic Structure ◽  
Structure Theory

scholarly journals Dynamic response of a curved railway track subjected to harmonic loads based on the periodic structure theory

2018 ◽  
Vol 232 (7) ◽  
pp. 1932-1950 ◽  
Author(s):  
Weifeng Liu ◽  
Linlin Du ◽  
Weining Liu ◽  
David J Thompson
Keyword(s):  
Dynamic Response ◽  
Decay Rate ◽  
Periodic Structure ◽  
Vertical Direction ◽  
Railway Track ◽  
Structure Theory ◽  
Radius Of Curvature ◽  
Large Radius ◽  
Moving Loads ◽  
Lateral Direction

In this study, the authors have analysed the dynamic response of a curved railway track that is subjected to moving and non-moving harmonic loads. The track is considered as a curved Timoshenko beam supported by periodically spaced discrete fasteners. The displacement and rotation of the curved rail are expressed as the superposition of track modes in the frequency domain. Periodic structure theory is applied to the equations of motion of the curved track, allowing the dynamic response of the track to be calculated efficiently in a reference cell. The effect of the stiffness and damping of the fasteners, the fastener spacing and the radius of curvature on the mobility and decay rate of the track are analysed for non-moving loads on the rail head. The vibration of the rail due to moving loads is also discussed. It is found that the dynamic response of a curved rail with a large radius has the same characteristics as that of a straight track. However, the dynamic response of the track is significantly affected when the radius of curvature becomes small. The radius affects the mobility; it also has an effect on the track decay rate below 2000 Hz and the velocity of the rail in the vertical direction when the radius is smaller than about 15 m and for the lateral direction when it is less than about 30 m. Moreover, the curvature has a significant influence on the vertical/lateral cross mobility, the magnitude of which increases as the radius is reduced. When the radius is larger than 10 m, the amplitude of the lateral vibration under a moving vertical load and the vertical response to a moving lateral load are inversely proportional to the radius.

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