Fracture Toughness Measuring Of Ceramics By SEVNB Method

As an important parameter of the mechanical properties, fracture toughness ofceramic materials is widely used for indicating the property of ceramic. The test resultshows much difference under different methods which causes more researches oftesting methods. SENB is a common testing method of fracture toughness of ceramicmaterials. However, due to the size effect of the notch crack, the test results are notaccurate as other methods. This objective of study is to sharp the notch crack withlapping paste of small particle to make the root diameter less than25μm to get exactfracture toughness with SEVNB. Through this study, the fracture toughness ofAlumina, Zirconia, Silicon Nitride, Boron carbide and other common ceramicmaterials are tested by SEVNB, SENB and IS. The result shows the KICtest data ofZirconia, HP Silicon Nitride and Boron carbide are smaller as the radius of root notchdecreases. When the notch radius turns to25μm, the fracture toughness is similar tothe result of IS test. The fracture toughness of zirconia is about5.3MPa^*m^1/2with thethe root diameter of13μm, the fracture toughness of HP Silicon Nitride is about5.1MPa^*m^1/2with the the root diameter of9μm, the fracture toughness of Boroncarbide is about2.8MPa^*m^1/2with the the root diameter of7μm. And96%aluminafracture toughness decreases a little with the root diameter, The KICis4.3MPa^*m^1/2with the root diameter of30μm.for non-press Silicon Nitride,thefracture toughness is stable on5.5MPa^*m^1/2.In the research,we also test the fractuewtoughness of Zirconia sintered at different temoture via1350℃、1450℃、1550℃、1650℃,the result shows,the size of grain inceases with higher sintering temperatureand turn to less sensitive to the root diameter.