Tensile Strength of Ceramic Components, and Critical Crack Size

Tensile Strength of Ceramic Components, and Critical Crack Size 

The tensile strength of a component can be determined by inserting Eq. (3) into Eq. (6), and solving for the stress (at the moment of fracture)  

The strength scales with the fracture toughness, and is inversely proportional to the square-root of the critical crack size a. This corresponds to the former results of the Griffith analysis. 

Strength test results on ceramic specimens show, in general, a large scatter. This follows from the fact, that in each individual specimen, the size of the critical crack is a little different. Rearranging Eq. (8) provides a relationship for the critical crack size (Griffith crack size) in a specimen  

For many ceramic materials, the ratio JQ/oy is of the order 1/100 /Tn. If a fracture starts in the interior of the component, the geometric correction factor for a pennyshaped crack (7 = 2/jt) can be used to calculate the corresponding Griffith crack size, giving a typical 80 pm. The size of critical flaws reflects the state of the art in 

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