数字图像相关（DIC）方法在钢铁材料力学性能测试中的应用研究

发布时间：2018-05-08 22:27

本文选题：数字图像相关 + 塑性应变比　；参考：《钢铁研究总院》2017年硕士论文

【摘要】：数字图像相关(DIC)方法是一种通过计算变形前后物体表面图像的灰度信息相关来获取被测物体的变形情况的测试方法,通过对比表面带有散斑的材料或结构变形前后的散斑图像,对全场位移、应变进行计算。DIC方法具有三维、全场、非接触等特点,因此其应用不受试样形状限制,可针对不同形状试样进行二维、三维变形测试,并获得整个变形场的变形信息,因而在材料的力学性能测试中得到了越来越广泛的应用。本文以IF钢、321不锈钢及A508-3钢等为材料,结合拉伸实验、疲劳实验及断裂力学实验等实验,针对DIC方法在材料力学性能测试方面的应用进行了研究,主要工作归纳如下:应用DIC方法对试样的应变进行了测量,并与引伸计所测结果进行对比,验证了 DIC方法在变形数据测试方面的准确性。应用DIC方法对IF钢的n值、r值进行了测量,并对横向引伸计的测试位置对r值测试的影响进行了研究。实验结果表明,r值测试结果的准确性与横向引伸计的测试位置有关,测试位置偏离试样断裂位置所得实验结果与通过断裂位置处应变计算所得结果不同,且测量位置距试样断裂位置越远则结果差异越大。将DIC方法的分析结果与实验过程相结合,在不增加额外实验操作的情况下,通过试样的应变分布情况成功对疲劳实验有效性进行了预测,避免了无效实验所造成的实验进度缓慢及实验成本增加等问题,同时,探索了 DIC方法在实验过程中的实时应用,增强了 DIC方法在材料力学性能测试中的应用时效性。应用DIC方法作为测试手段进行了 A508-3钢的J积分及CTOD实验,解决了应用柔度法测试时存在的裂纹扩展"负增长"的问题,并实现了试样CTOD的直接测量。同时,应用DIC方法对试样在实验过程中的变形及裂纹扩展规律进行了研究,通过分析试样的位移场、应变场的变化情况确定了试样裂纹面的转动中心及裂纹扩展路径等相关信息。
[Abstract]:The digital image correlation (DIC) method is a method to obtain the deformation of the object before and after deformation by calculating the gray level information correlation of the surface image before and after the deformation, and by comparing the speckle images before and after the deformation of the material or structure with speckle on the surface. The DIC method has the characteristics of three-dimensional, full-field, non-contact and so on. Therefore, its application is not limited by the shape of the specimen, so it can be used for two-dimensional and three-dimensional deformation testing of samples with different shapes. The deformation information of the whole deformation field is obtained, so it is more and more widely used in testing the mechanical properties of materials. In this paper, the application of DIC method in testing mechanical properties of materials is studied by means of tensile test, fatigue test and fracture mechanics test, which are based on if steel Si321 stainless steel and A508-3 steel. The main work is summarized as follows: the DIC method is used to measure the strain of the specimen, and compared with the result of extensometer, the accuracy of the DIC method in the deformation data testing is verified. N value r value of if steel was measured by DIC method, and the influence of measuring position of transverse extensometer on r value test was studied. The experimental results show that the accuracy of the test results is related to the testing position of the transverse extensometer. The experimental results obtained from the test position deviating from the fracture position of the specimen are different from those obtained by the strain calculation at the fracture location. The longer the measuring position is from the fracture position of the specimen, the greater the difference of the results is. By combining the analysis results of DIC method with the experimental process, the validity of the fatigue experiment is predicted successfully by the strain distribution of the specimen without adding additional experimental operation. At the same time, the real-time application of the DIC method in the experiment process is explored, and the timeliness of the application of the DIC method in the testing of mechanical properties of materials is enhanced. The J integral and CTOD experiments of A508-3 steel were carried out by using DIC method. The problem of "negative growth" of crack growth in A508-3 steel was solved, and the direct measurement of sample CTOD was realized. At the same time, the DIC method is used to study the deformation and crack propagation of the specimen during the experiment, and the displacement field of the specimen is analyzed. The variation of the strain field determines the rotation center and crack propagation path of the crack surface of the specimen.
【学位授予单位】：钢铁研究总院
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG115.5

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