相变滞后对裂纹屏蔽效应的数值分析

论文针对奥氏体-马氏体双相材料,研究裂纹尖端区弥散分布的奥氏体颗粒在应变诱发时发生的相变对裂纹的屏蔽效应.鉴于实验中已发现的不同相变滞后对裂纹屏蔽效应的不同影响,研究通过在裂纹尖端区不同位置嵌入相变颗粒,考虑到裂纹尖端区应力应变场的奇异分布及其诱发的相变,将裂纹尖端区相变滞后问题转化为相变颗粒在裂纹尖端区的位置问题.计及奥氏体-马氏体相变的体积膨胀效应进行了平面应力裂纹问题数值模拟,得到了单个相变夹杂对裂纹屏蔽效应的影响规律.结果表明:裂纹尖端区相变夹杂的位置对裂纹的屏蔽效应在距裂尖2倍夹杂直径以内影响极大,且以裂尖86度方向为界.其影响规律与McMeeking和Evans理论预言的60度方向不同.

THE NUMERICAL ANALYSIS OF CRACK SHIELDING EFFECT INFLUENCED BY THE HYSTERESIS OF TRANSFORMATION

In this paper, the crack shielding effect influenced by the transformation of austenite, is studied numerically in the austenite-martensite dual material. The transformation of austenite particles embeded in the crack materialis is induced by the strain ahead of the crack tip. Considering the singular distribution of stress-strain field ahead of the crack tip and the strain induced transformation, in this study, through embedding a transformed particles in the different locations of the crack-tip area, the transformation hysteresis problem can be transferred to a problem of transformed particle location. Based on the volume expansion effect of austenite-martensite transformation, a plane stress crack problem is investigated and the influence of the location of transformed particle on the crack shielding effect is obtained. The results show that the location of transformed particles at the crack-tip area has a great influence on the crack shielding effect, the shielding effect is occurred out of the sector 86°ahead of the crack tip, which is different with the result of McMeeking and Evans based on the analysis theoretically.