X70管道钢裂纹尖端张开角的试验研究

高压富气输送管道要求发展管道钢的裂纹尖端张开角(CTOA)的测试方法。采用准静态的撕裂过程和长裂纹扩展长度试件,进行了X70管道钢的裂纹扩展试验,用摄像机跟踪拍摄裂纹扩展全过程,从获得的照片上直接测量出裂纹扩展全过程的CTOA值,分析了裂纹扩展中的断裂力学行为。试验结果表明:试件的韧带厚度越小,越容易获得稳定的扩展过程,且稳态裂纹扩展的CTOA值随试件韧带厚度的增加而增大,太厚的试件不易得到稳态扩展过程。韧带厚度为4mm、8mm试件的稳态的裂纹扩展阶段分别为7.6°、11.3°,裂纹扩展长度与韧带厚度比在4―25、4―10之间。

EXPERIMENTAL INVESTIGATION ON CRACK TIP OPENING ANGLE OF X70 PIPELINE STEEL

High pressure,rich gas transmission pipeline requires the development of measuring method of Crack Tip Opening Angle(CTOA).Using quasi-static tear propagation and specimen of long crack propagation length, the crack propagation experiment of X70 pipeline steel was conducted.The whole progress of propagating crack was recorded by camera,the CTOA were directly tracked from the photographs,the behavior of fracture mechanics of crack propagation was analysised.The test results show that the thinner the ligament thickness is, the more easily the steady-state crack propagation process of thin ligament is obtained,and the CTOA of steady-state crack propagation process increases as the ligament thickness increases.CTOA of steady-state crack propagation process of 4mm and 8mm ligament thicknesses are 7.6°and 11.3°,respectively,and the ratio of crack propagation length and the ligament thickness are 4―25 and 4―10,respectively.