Published on July 29th, 2013 | By: Martin Grolms0
New way to determine thermal shock behavior of ceramicsPublished on July 29th, 2013 | By: Martin Grolms
(Editor’s note: This article was originally published in Wiley Materials Views on July 17.)
Until the 1950s, the most important ceramic materials were pottery, bricks and tiles, cements and glass. Because of the remarkable physical and mechanical properties, ceramics are found in a broad range of applications today: as insulator, in ballistic protection, biomedical implants, coatings of jet engine turbine blades, ceramic disk brake, bearings and many more. Thermal shock behavior of ceramic materials plays a decisive role in their industrial use. Rapid heating and cooling of ceramics in industrial applications result in thermal stresses that can lead to damage or catastrophic failure.
Experimental methods have been developed and used to investigate the thermal shock behavior of ceramics. To determine it, the quenching technique is a typical method. After heating in a furnace the samples are quenched in air, water or oil.
Subsequently the residual mechanical properties are measured to characterize the thermal shock resistance. However, the quenching parameters and experimental results do not agree well with the real application conditions and theory, respectively. Even a novel method bases on rapid heating provides only insufficient data affecting thermal shock resistance.
In order to overcome these problems a group of researchers from the Brandenburg University of Technology in Cottbus, Germany, combined experimental testing and numerical simulation methods. Dr. Wei Zhang and co-workers heated alumina ceramic disks rapidly in the center using a plasma beam resulting in temperature and thermal stress gradients, which led to the failure of the samples. A finite element model has been developed and approved by means of comparison with experiments. The researchers also studied the effect of the sample thickness and the parameter of thermal shock tests such as plasma arc power on the experimental and simulation results.
Compared with the experimental results the simulated results show excellent agreement. Dr. Zhang and co-workers conclude that it is an appropriate way to determine the thermal shock behavior of ceramic materials by the combination of experimental testing and numerical simulation. The German researchers propose that in future work the method can be used to investigate the thermal shock behavior of refractory materials and components.
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