Ⅰ-Ⅱ混合型裂纹相变增韧分析

Toughening Analysis of Mixed-Mode Ⅰ-Ⅱ Cracks in Transformation Toughened Ceramics

采用压力敏感准则和权函数法对相变增韧陶瓷Ⅰ Ⅱ混合型裂纹的增韧效应进行了理论预测 ,分别给出了静止裂纹和定常扩展裂纹相变塑性屏蔽的理论表达式。结果表明 :相变对静止裂纹有负屏蔽效应 ,并随KⅡ KⅠ 的比值增大而增大 ;对定常扩展裂纹的增韧结果除与材料弹性模量、相变尾区高度和相变体积分数有关外 ,还随KⅡ KⅠ 的比值增大而减小。

By use of the pressure sensit ive stress criterion and the method of weight function, the fracture toughness e nhancement induced by mixed mode Ⅰ Ⅱ cracks in phase trans formation toughened ceramics is predicted theoretically. The theoretical express ions for the toughening effects of both the stationary and the steady state gro wing cracks are given respectively. Results show that there is a negative effect from the stationary cracks and it increases with the increase of K Ⅰ/ K Ⅱ, and that the toughening effect of the steady state gro wing cracks i s not only associated with the modulus of elasticity, the width of transformatio n area and the transformation volume fraction, but also decreases with the incre ase of K Ⅰ/ K Ⅱ.