基于缺口圆棒试样的管道环焊缝本构关系测试方法

Test method for constitutive relationship of pipeline girth welds based on notched round bar specimens

为准确获得高强度管线钢环焊缝各材料区域真实本构关系,分别在X80钢环焊缝的母材区、焊缝区设置缺口,获得两种缺口圆棒试样,并对其进行拉伸测试。拉伸过程中采用高速相机获得试件缺口位置的实时图片,基于拍摄图片缺口边缘灰度值的变化规律,提出了一种实时测量缺口区域最小截面直径的自动测量方法——最小直径追踪法。采用最小直径追踪法和修正公式可得到母材及焊缝材料真实本构关系,应用幂律硬化模型对所获曲线进行拟合,得到对应材料的本构关系参数,再利用有限元方法对测试结果进行验证,结果表明该测试方法及结果可靠有效。所提出的测试方法及测试流程对于获取管道母材及焊缝区的本构关系、实现管道环焊缝力学性能的准确测试具有较强的实际意义。

To accurately obtain the true constitutive relationship of each material area in the girth welds of high-strength pipeline steel.Definitely,two kinds of notched round bar specimens were obtained by setting notches on the base metal and in the weld area of X80 steel respectively,and the tensile tests were carried out on the specimens,with the real-time images of specimen notches captured by the high-speed cameras during the tensile process.Then,based on the change law of gray value at the notch edge,an automatic measurement method,i.e.the minimum diameter tracing method,was proposed to measure the minimum sectional diameter of the notch area in real time.In addition,the true constitutive relationship between the base metal and the weld material can be obtained based on the minimum diameter tracing method and the modifier formula,and by fitting the curve obtained with the power law hardening model,the constitutive relationship parameters of corresponding materials can be gained.Finally,the test results were verified with the finite element method.The results show that both of the test method and the results are reliable and effective.The studied test method and the process are of great practical significance for obtaining the constitutive relationship between the base metal and the weld area and realizing the accurate test of the mechanical performance of the pipeline girth welds.