试件和内压管道裂纹端约束效应的相关性分析

CORRELATION STUDY OF THE CRACK-TIP CONSTRAINT EFFECT FOR TEST SPECIMENS AND INTERNAL-PRESSURE PIPELINES

为使实验得到的结果更好地应用于估测内压管道的断裂,选取X80钢试件的一些几何体和载荷配置,在J—A2方法的基础上,用平面应变及非线性分析,对不同形式和尺寸的断裂试件裂纹端的约束效应进行数值计算,得到各种试件的J—A2曲线。结果表明,单边缺口拉伸试件的约束参数A2对载荷水平J不是很敏感。而单边缺口弯曲和紧凑拉伸试件由于弯曲应力的影响,A2值随J有一定的变化。具有相同裂纹深度的单边缺口拉伸试件与内压管道的J—A2和a/W—A2曲线相关性较好。最后,应用单边缺口拉伸试件的实验曲线和管道的有限元数值结果,对有裂纹管道进行断裂预测。

In order to apply the experimental results to estimate the fracture of internal-pressure pipelines, some geometry test specimens and load configuration for X80 steel were studied. Based on the J-A2 method,the constraint effect on the crack tip fields for standard fracture specimens with various type and size were quantified by using plane strain analysis and nonlinear numerical calculation. The J-A2 curves of different specimens were obtained. It is shown that the constraint parameter A2 of single edge notched tension specimens are not sensitive to load level J. However, the A2 values of single edge notched bend and compact tension specimens have certain fluctuation with J which shows that global bending stress exerts a influence on the constraint parameter A2. For single edge notched tension specimens and cracked pipelines which have the same crack-depth, not only the tendency of their J-A2 and α/W-A2 curves is in good agreement but the A2 values are close. Their have a good relevance. According to the experimental curves of single edge notched tension specimens and the numerical calculations, the fracture initiation pressures of some flawed pipelines were predicted.