数字图像相关法确定X80管道钢三点弯曲 试样旋转中心

Determination of rotation center of X80 pipeline steel three-point bending specimen by digital image correlation method

旋转因子对于材料断裂韧性的估算是一个非常重要的参数,目前旋转因子的计算没有统一的方法。为了对比不同方法计算旋转因子的准确性,文章基于数字图像相关(DIC)技术,分别采用应变云图法、虚拟双引伸计法和趋势线延长法,研究了X80管道钢三点弯曲试样旋转因子及利用旋转因子确定CTOD的可行性。结果表明:3种方法获得的旋转因子随着裂纹长度的增加,呈逐渐减小的趋势;3种方法旋转因子确定的CTOD与直接测量值基本吻合,其中应变云图法旋转因子的CTOD计算值与直接测量值最为吻合,获得的旋转因子最为可靠,其他两种方法的CTOD计算值整体偏大,可通过更改引伸计位置和趋势线角度来获得准确的旋转因子值。

Rotation factor is a very important parameter for the estimation of fracture toughness of materials.There is no unified method for the calculation of rotation factor at present.In order to compare the accuracy of different methods to calculate the rotation factor,based on digital image correlation(DIC),strain nephogram method,virtual double extensometer method and trend line extension method were used to study the rotation factor of X80 pipe-line steel three-point bending specimen and the feasibility of using rotation factor to determine the crack tip opening displacement(CTOD).The results show that the rotation factor obtained by the three methods decreases with the increase of crack length.The CTOD values determined by the three methods are basically consistent with the direct measurement values.The CTOD values calculated by the strain nephogram method are the most consistent with the direct measurement values,and the obtained rotation factors are the most reliable.The CTOD values of the other two methods are larger,and the accurate rotation factor values can be obtained by changing the extensometer position and trend line angle.