数字图像相关中基于位移场局部最小二乘拟合的全场应变测量

Full-Field Strain Measurement Based on Least-Square Fitting of Local Displacement for Digital Image Correlation Method

为了从含噪声的位移场中计算得到可靠的应变场,提出一种基于位移场局部最小二乘拟合的全场应变求解方法。介绍了数字图像相关方法的原理,阐述了基于位移场局部最小二乘拟合的全场应变求解方法,并讨论了计算区域边界、孔洞及裂纹附近区域等情况下的应变计算。对均匀变形和中心带圆孔的薄铝板拉伸实验的计算结果表明,该方法能有效地从原始位移场数据中提取全场应变信息。在均匀变形情况下应选择大的应变计算窗口,计算结果更逼近真值;在非均匀变形情况下,如果位移场中包含较强的噪声,则应选择较大的应变计算窗口,而位移场精度很高时可选择更小的应变计算窗口。

In order to obtain reliable strain field , full-field strain measurement based on least-square fitting of local displacement for digital image correlation method is proposed. The principle of digital image correlation （DIC） method is introduced, and full-field strain measurement based on local least-square fitting is expatiated, strain calculation near the border, hole and crack are also discussed. The results from homogeneous deformation test and the tensile test of the aluminum specimen with a hole in the center obviously demonstrated the validity of this technique. Large strain calculating window is recommended to use in case of homogeneous deformation,so calculation results approach true value. For inhomogeneous deformation, large calculating window should be selected to according to the noise level of the local displacement field, but when displacement field has high accuracy, smaller calculating window is selected.