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12-04 :: April/May 2012
nanotimes News in Brief
43
Ceramics // Researchers are Able to Reshape the Surfaces of Malformed
Ceramic Components by Bombarding them with Tiny Pellets © Based on Material by Fraunhofer IWM
R
esearchers at the Fraunhofer Institutes for Mechanics of Materials IWM in Freiburg and
for Production Systems and Design Technology IPK in Berlin, both in Germany, have now found a way to straighten out distorted ceramics using shot peening, a process by which small pellets, known as shot, are fired at the surface of a component with a blasting gun. The shot strikes the surface and alters the shape of the thin, outermost layer of material. By moving the gun over the ceramic part along a preci- sely calculated path, scientists are able to counteract any undesired warping or create lightly curved mirro- rs out of thin, even ceramic plates.
“Shot peening is common practice for working metals,” says Dr. Wulf Pfeiffer, who manages this business unit at the IWM, “but the technique has never been used on ceramics because they are so brittle – they could shatter, like a china plate being hit with a hammer. This meant that we had to adapt the method to the material with great precision.”
The researchers began by analyzing which size of shot would be suitable for use on ceramics, as the surface could be destroyed by pellets that were too big. Pellet speed is another critical factor: hitting the material too fast causes damage; too slow and the
shape of the surface is not altered enough. They also discovered that it is important not to bombard the same spot too often with too much shot. Before pro- ducing a new component, the scientists first conduct experimental analysis to determine what can be ex- pected of the particular ceramic involved. They fire a beam of shot at it and then measure the resultant stresses to see what sort of deformation is possible and how the beam should be directed.
The experts have already produced various proto- types, including a ceramic leaf spring and a concave mirror. For manufacturing simple components, the technique is now advanced enough to be used in series production. The IWM scientists have recently gone one step further and are developing a computer simulation that will allow components to be worked in multiple axes. Meanwhile their colleagues at the IPK are working on automating the process using a robot.