基于一阶及二阶DIC方法的常应变剪切带的测量误差分析

Analyses of Measurement Errors of Shear Bands with Constant Strains Based on the One-and Two-order DIC Methods

制作了水平和倾斜的常应变剪切带,使用数字图像相关方法(DIC)对剪切带内、外的位移场和应变场进行了测量,分析了形函数、子区尺寸及测点间距对测量结果的影响。结果表明:在剪切带边界附近,一阶或二阶DIC方法的位移误差限均较大,这是因为这些区域的子区覆盖了一部分剪切带;子区尺寸越大,或测点距离剪切带边界越近,位移误差限越大;一般对于剪切带边界附近测点,二阶DIC方法比一阶DIC方法的位移误差限小;随着测点间距的增加,一阶或二阶DIC方法的剪切带的法向剪应变坐标曲线由陡峭变得平缓,剪切带宽度逐渐增加。

The horizontal and oblique shear band with constant strains are produced, using the digital image correlation （DIC） method, the displacement field and strain field of the inside and outside the shear band were measured, the influences of the shape function, subset size and spacing of points on displacement were analyzed. The results showed that the displacement error limits of the one-or two-order DIC methods are high nearby the boundary of a shear band, because a subset covers a part of a shear band. The larger the subset size is or the shorter the distance from the subset center to the boundary of a shear band is, the higher the displacement error limit is. Usually, the displacement error limits of the two-order DIC method are much lower than those of the one-order DIC method nearby the boundary of a shear band. With the increase of the spacing of points, the shear strain-coordinate curves of the shear band in the normal direction of one- or two-order DIC methods change from steep to gentle, and widths of shear bands increase.