| 田文煜,杜伟,左宏,李群*.基于数字图像相关的金属材料低温裂尖张开位移试验测量方法[J].实验力学,2020,35(6):1014~1022 |
| 基于数字图像相关的金属材料低温裂尖张开位移试验测量方法 |
| Experimental measurement method of low temperature crack tip opening displacement of metallic materials based on digital image correlation |
| 投稿时间：2019-01-16 修订日期：2019-03-25 |
| DOI：10.7520/1001-4888-19-014 |
| 中文关键词: 低温效应 裂尖张开位移(CTOD) 裂纹 数字图像相关(DIC) |
| 英文关键词:low temperature effect Crack Tip Opening Displacement(CTOD) crack Digital Image Correlation (DIC) |
| 基金项目:国家自然科学基金面上项目(11772245)资助，陕西省杰出青年科学基金项目(2018JC-004) |
|
| 摘要点击次数: 754 |
| 全文下载次数: 208 |
| 中文摘要: |
| 随着金属材料，尤其是天然气管线钢在高寒低温环境下的广泛应用，研究金属材料的低温断裂失效规律具有重要的科学意义和工程价值。在研究断裂失效规律的指标中，裂尖张开位移(Crack Tip Opening Displacement, CTOD)是预测裂纹扩展的重要断裂参数之一，可用来表征金属材料抵抗裂纹扩展的能力。传统上，裂尖张开位移主要通过载荷-裂纹端部张开位移曲线间接获取而无法直接测量，此外测量裂纹端部张开位移所用的引伸计在低温环境下容易导致漂移，造成测量不准确。针对上述情况，本文基于数字图像相关(Digital Image Correlation, DIC)技术开发了一种金属材料低温断裂韧度CTOD试验测量方法，针对0℃、-20℃、-40℃、-60℃低温环境下，某天然气管线钢材料的裂尖张开位移，进行非接触试验直接测量。将数字图像相关系统和低温试验系统结合使用，透过真空双层玻璃视窗，利用专用摄像机采集低温下三点弯曲断裂试件表面位移数据；运用VIC-2D分析软件，将采集的图片数据与像素之间建立对应关系，在裂纹位置设置几处虚拟引伸计，提取起裂时虚拟引伸计所测量的裂纹张开位移曲线，并运用最小二乘法线性拟合，根据相似关系得到裂纹尖端张开位移临界值，即断裂韧度CTOD；在不同温度下进行试验，得到了不同温度下金属材料断裂韧度CTOD随温度的变化曲线和规律，试验结果表明,三点弯曲试样断裂韧度随着温度的降低呈现明显的下降趋势。本文工作基于DIC技术的金属材料低温CTOD测量，方法直接，准确度高，尤其适用于低温环境，可实现金属材料CTOD的非接触试验测量。本研究获取的管线钢材料CTOD临界值在不同温度下的变化规律，可为天然气输送管道的工程设计和优化提供参考。 |
| 英文摘要: |
| With the wide application of metallic materials, especially natural gas pipeline steels in extremely low temperature environment, it is of great scientific significance and engineering value to study the low temperature fracture failure law of metallic materials. Among them, Crack Tip Opening Displacement (CTOD) is one of the important fracture parameters for predicting crack propagation. It can be used to characterize the ability of metallic materials to resist crack propagation. Traditionally, the CTOD cannot be directly measured, and is obtained indirectly through the load-crack end opening displacement curve. In addition, the extensometer used to measure the crack opening at the end of the crack is prone to having drift in a low temperature environment, resulting in inaccurate measurement. The present study develops a CTOD experimental measurement method for low temperature fracture toughness of metallic materials based on the digital image correlation (DIC) technology. In this study, the CTOD of a pipeline steel material is used, and the non-contact measurement test is directly performed in the low temperature environment of 0℃, -20℃, -40℃, -60℃, respectively. By combining the DIC system and the low temperature test system, the surface displacement data of the three-point bending fracture test piece at low temperature are collected through a vacuum double-glazed window using a dedicated camera. Using VIC-2D analysis software, the corresponding relationship between the acquired image data and the pixel is established. Several virtual extensometers are set at the crack position to extract the crack opening displacement curve measured by the virtual extensometer at the time of crack initiation. We use the least squares linear fitting to obtain the critical value of the CTOD according to the similarity relationship, i.e., the fracture toughness CTOD; Finally, the curve and law of the fracture toughness CTOD of metallic materials at different temperatures are obtained. The experimental results show that the fracture toughness of the three-point bending specimen shows a significant downward trend with the decrease of temperature. This work develops the low temperature CTOD measurement method of metallic materials by using DIC technology with direct and accurate advantages, especially suitable for low temperature environment. It can realize the non-contact experimental measurement of CTOD. The variation of CTOD critical value of pipeline steel materials obtained in this study at different temperatures can provide reference for engineering design and optimization of natural gas transmission pipelines. |
| 查看全文 下载PDF阅读器 |
| 关闭 |
|
|
|
|
|
