Papers by Keyword: Water Quench Test

Abstract: In this work, the geometry effect on the thermal shock behaviour of a nine layered Al2O3- 5%tZrO2/Al2O3-30%mZrO2 ceramic fabricated by slip casting has been studied. A finite element model has been used to estimate the magnitude and location of the maximum thermal stresses in the layered material as well as the influence of the variation of this layered architectural design in the thermal shock crack initiation and extend throughout the specimens of study. Experimental tests on various samples have been carried out to validate the model. The residual stress distribution profile in the laminate, due to the elastic mismatch of the different layers along with the zirconia phase transformation on the Al2O3-30%mZrO2 layers, conditions the thermal shock response of the material. It is demonstrated how the variation of the outer most layer thickness in the laminates modifies the stress state in the surface, affecting the thermal shock crack initiation.

Abstract: Most important properties which are usually measured for refractories are work temperature and thermal stability. Thermal stability of the alumina based samples was measured using a standard laboratory procedure, the water quench test ( JUS.B.D.8.319.). ImagePro Plus Program was used for image analysis of microphotographs of the samples before, during and after water quench test. Changes at the surface before, and after cycling were given. Mechanical characteristics were considered such as compressive strength, and dynamic modulus of elasticity. It was measured by resonance frequency measurements, as well as ultrasonic velocity. In this work the correlation between microstructure, ulatrasonic velosity and strength on thermal stability of the sample were investigated. The obtained results were used for validation of the model to predict the thermal stability of the refractory specimen.

Abstract: In this work, the thermal shock behavior of an Al2O3-5%tZrO2/Al2O3-30%mZrO2 multilayer ceramic is studied. On these materials, a tetragonal to monoclinic phase transformation within the Al2O3-30%mZrO2 layers takes place when cooling down from sintering. The latter induces an increase in volume and therefore compressive residual stresses arise in these layers. The residual stress distribution profile in the laminate influences the thermal shock response of the material. A finite element model has been developed to estimate both the thermal strain effects during the sintering process as well as the temperature distribution and stress profile within the laminate during thermal shock testing. Experimental tests on the monoliths and laminates were carried out and compared to the model. It is observed that the presence of the compressive layers within the laminate inhibits the penetration of thermal shock cracks into the body at even more severe conditions than in the monolithic material.