The prediction of sound and vibration transmission in built-up structures is important for human comfort, health and safety. For structural reasons, engineering structures often incorporate periodic ribbed plates to increase stiffness and stability whilst reducing the weight. However, vibration propagation on periodic ribbed plates is complex due to the existence of stop/pass bands. This thesis is concerned with predicting vibration transmission between isotropic, homogeneous plates and periodic ribbed plates. The objectives are to investigate the use of Statistical Energy Analysis (SEA) and develop and validate advanced SEA (ASEA) using ray tracing to incorporate tunnelling mechanisms. Two approaches were considered for modelling the periodic ribbed plate: either representing it as a single subsystem or representing each bay as a single subsystem in the high-frequency range (above the fundamental local mode of the bay). In the low-frequency range (below the fundamental local mode of the bay) Finite Element Methods (FEM) and laboratory experiments show that the periodic ribbed plate can be adequately modelled in SEA using wave approaches from periodic structure and orthotropic plate theories. In the high-frequency range a significant decrease in energy along successive bays was identified using FEM leading to the conclusion that it is not appropriate to model a periodic plate as a single subsystem. SEA models were therefore investigated that treated each bay as an individual subsystem using wave theory. For different L-junctions formed from an isotropic, homogeneous plate and a periodic ribbed plate, SEA significantly underestimated the response in the bays. Experimental SEA (ESEA) was used to investigate these discrepancies which confirmed the existence of tunnelling mechanisms between physically unconnected subsystems. In contrast to SEA which gave errors up to 60 dB for the furthest bay from the junction, ASEA gave errors less than 6 dB when the mode count for the bay was greater than five. A range of two- and three- plate structures with different periodic ribbed plates or periodic folded plate have been modelled with ASEA. The results all lead to the conclusion that ASEA can successfully incorporate tunnelling mechanisms and provide a significantly more accurate approach to predicting high-frequency vibration transmission across periodic ribbed plates than SEA.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:566286 |
| Date | January 2012 |
| Creators | Yin, Jianfei |
| Contributors | Hopkins, Carl |
| Publisher | University of Liverpool |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://livrepository.liverpool.ac.uk/8193/ |
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