Over the last few decades, porous metals have received a large amount of interest in industry due to the rapid advancement in manufacturing techniques, design and possible applications. Their unique properties and multi-functionality allow them to be utilized in many different applications throughout different industrial sectors. This thesis manufactured porous steel using the Lost Carbonate Sintering (LCS) method and studied their mechanical and sound absorption properties. The dissolution, decomposition and re-sintering routes were studied and compared. The mechanical properties of the specimens manufactured by LCS via the dissolution and decomposition routes were measured by compression and three-point bending tests. The compression strength, elastic modulus and flexural strength of the porous steel specimens manufactured with both routes increased with increasing relative density, pore size and compaction pressure. Increasing the sintering temperature and time in the decomposition route served to increase the compression strength, elastic modulus and flexural strength. The advantages and disadvantages of the dissolution and decomposition routes were analyzed. The porous steel specimens manufactured by the decomposition route had better mechanical properties than those manufactured by the dissolution route. The acoustic absorption performance of porous steel manufactured by the LCS process via the dissolution route was assessed using the standing wave impedance tube method. The single layer specimens showed excellent sound absorption properties at high frequencies. Pore size of the porous steel had no significant effect on the sound absorption coefficient. Sound absorption at low frequencies can be improved by increasing the thickness of specimens, or by introducing an air gap behind the absorber. The sound absorption properties of the porous specimens of multi-layer assemblies with different porosities, pore sizes, thicknesses and air-gap depths were assessed. The porosity of the first layer of multi-layer-assembled specimens had a critical effect on the sound absorption coefficient and frequency of peak. Increasing this porosity increased the sound absorption coefficient at all frequencies after the peak. The effects of the porosities of the subsequent layers were smaller. When the first layer had a high porosity, increasing the porosity of the second layer increased the frequency of peak. When the first layer had a low porosity, increasing the porosity of the second layer enhanced the sound absorption coefficient of peak. The effects of pore size were not significant. Increasing the thickness of specimens and the depth of air-gap behind the specimens decreased the frequency and coefficient of the peak in the sound absorption curve.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:569586 |
| Date | January 2011 |
| Creators | Lu, Miao |
| Publisher | University of Liverpool |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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