ISSUE 1/2009

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Hartmut Polzin, Claudia Dommaschk and Klaus Eigenfeld, Freiberg, Germany, Ronny Reuther, Waren, Germany, Reinhard Schulze and Erik Paape, Potsdam, Germany, Michael Teichgräber, Meißen, Germany
Damping behaviour of composite aluminium bronze castings with ceramic preforms

The aim of the project funded by the German Federal Ministry of Education and Research (BMBF) was to apply bionic knowledge to the manufacture of castings for ship drives. One of the topics of this project was the application of ceramic preforms used as inlets in aluminium bronze ship propellers. The aim was to avoid the formation of thermal centres in those areas of bionic ship propellers with long solidification times, and a reduction of the propeller mass through the use of ceramic components.
The damping behaviour of the aluminium bronze alloys is crucial to avoid the “singing phenomenon” of ship propellers. Especially for propellers with an extremely low noise level, such as propellers used in marine ships, submarines or research ships, special alloys with high damping levels are used.
A range of different materials was used to produce the ceramic performs: Porous compact calcium aluminate ceramic, piled-up ceramic wires based on Al2O3 (“spaghetti structure”), and open-celled foamed ceramic based on SiC. The objective was to create different internal contact surfaces with a damping effect between the ceramic material, metal and air

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