MgO質焼結体の曲げ強度に及ぼす粒子径と人工欠陥寸法の影響

抄録

MgO and MgO-ZrO₂ sintered bodies with different grain sizes were prepared by pressureless sintering, and an artificial crack was introduced on the specimen surface by Vickers indentation method. Then the strength was measured by 3-point bending tests to examine the effects of grain size and artificial crack length on the bending strength of MgO sintered body.
In the case of a crack shorter than the critical length, the bending strength was constant, irrespective of the crack length and equal to the strength of the smooth-faced specimen. Above the critical crack length, the bending strength decreased with an increase in crack length, which follows the rule of the linear elastic fracture mechanics, LEFM. The equivalent critical crack length, a_c, calculated by means of LEFM, was not proportional to grain size, D, but it increased with an increase in D. The relationship between a_c and D is expressed as a_c=6.39+0.36D-2.89×10^-3D². Consequently, the bending strength, σ was apparently expressed by an equation, σ=262.2+402.3D^-1/2.