Determining the fracture toughness of ceramic filter materials using the miniaturized chevron-notched beam method at high temperature

Abstract

The aim of the application of open cell ceramic foam filters during casting of metals is the reduction of non-metallic inclusions and turbulences in the melt flow. Hence, an improvement of the quality of the cast products is achieved. The integrity of the filter at mechanical loading under elevated temperatures requires a mechanical characterization of the bulk material of the filter. In particular, fracture toughnesses have to be determined for a new generation of filter materials. The presented work describes an experimental method to measure fracture toughnesses of the filter materials.The mechanical testing is performed with the help of 4-point-bending tests using miniaturized chevron-notched specimens at different temperatures. Additionally, the geometry function of the test set-up is calculated and compared with an empirical formula by Munz [1]. At the end, the fracture toughness is determined at room temperature and 800°C. Further results characterize the influence of different geometrical parameters of the test set-ups on the maximum tensile stresses in the specimen and the load-displacement curves.