裂纹尖端附近区域的应力应变场分析

Analysis of Stress & Strain near the Crack Tip

主要分析了裂纹尖端附近区域应力和应变场的分布情况,着重研究了裂纹尖端附近断裂过程区内的应力和应变分布。在假定断裂过程区内应力呈线性分布的条件下,利用三个协调条件(塑性奇异性的消除、裂纹尖端在临界条件下的能量平衡及裂纹张开角)分析了断裂过程区的特性,得到了断裂过程区的精确长度。同时,假定断裂过程区中的应变也呈线性分布,确定了断裂过程区中的拉伸应变。根据确定的断裂过程区的长度,修正了J-Q理论,并根据应力和应变连续分布的特点,对裂尖附近应力、应变的弹塑性J积分解作了修正,确定了裂尖附近断裂过程区和弹塑性区中应力、应变场的分布。裂尖附近区域应力、应变场的确定,对于输油气管道裂纹的扩展机理研究,提供了技术支持。

Stress-strain distribution near the crack tip was studied in this paper,with the emphasis on the fracture process zone (FPZ). Assuming the distribution of stress within the FPZ is linear ,adopted three different consistency namely elimination of the plastic singularity at the crack tip,the balance of energy at the onset of crack motion and the crack opening angle ,the general features of FPZ was analyzed and the correct length of FPZ and normal stress distribution within FPZ were determined. Similarly, the normal strain within the FPZ was obtained assuming the distribution of strain within the FPZ is linear. The maximum normal stress and strain locates in the juncture of FPZ and plastic region near the crack tip and their value does not depend on external loading. According to the length of FPZ and the continuous distribution of stress and strain,the stress and strain near the crack tip were revised applied amendatory J-Q theory. The determination of stress & strain distribution near the crack tip is a good supportive aid for research of crack propagation mechanism of oil & gas transmission pipeline.