The determination of strain and as a result Young's modulus and the fracture energy of refractories at temperatures up to 1500°C is based on a noncontacting, self-marking method using the digital speckle correlation technique. This system images two laser-illuminated surface spots onto CCD-cameras with well-defined geometry and calculates the load-dependent shift of the surfaces using a special software. The application of the laserspeckle-extensometer (LSE) at high temperatures has required a special design of the testing equipment in order to combine furnace, testing machine and the measurement units as well as the use of interference-filters. The determination of Young's modulus of three kinds of shaped refractories based on a compression test and a tensile test as well as the determination of fracture energy based on a wedge splitting test at room temperature has shown good reproducibility and good agreement with literature. According to measurements at 1250°C the LSE has shown stable, reproducible results. Analyzing the results of dynamic measurements of Young's modulus and furthermore the increase of the stress-strain ratio under cyclic load it is evident that the samples have been influenced by creeping. Measurements between 1200°C and 1400°C have shown a decrease in the stress-strain ratio for every kind of refractory.<br />At 1400°C decorrelation-effects were likely to occur due to the influences of heat-radiation and convection.
|Translated title of the contribution||Application of the laserspeckle-extensometer to investigate the elastic and fracture mechanical behavior of refractories at high temperatures|
|Publication status||Published - 12 Oct 2005|