受离面刚体位移的影响,普通二维数字图像相关(DIC)方法测得的应变结果往往精度较差。基于双45°双反射镜成像技术,提出了一种改进的二维DIC方法来提高应变测量精度。利用双反射镜成像,将试样正反面散斑图案记录到同一张图像中,对左右图像中对应点的应变取平均值,可自动消除试样离面刚体位移的影响,获得准确的全场应变。开展了两组拉伸实验来验证该方法的可行性。实验结果表明:对于均匀变形,由改进的二维DIC方法得到的双向应变与电测法的结果相吻合;对于非均匀变形,得到的结果与有限元法结果相一致。因此,本文提出的二维DIC方法具有较高的应变测量精度,是一种便捷、有效、高精度的应变测量方法。

Strain results obtained using common two-dimensional digital image correlation (2D-DIC) method usually have rather poor measurement accuracy owing to rigid out-of-plane displacement. This study proposes a modified 2D-DIC method based on 45° dual-reflector imaging technique to improve the strain measurement accuracy. The speckle patterns of the front and rear surfaces can be recorded in a single image using dual-reflector imaging. The effect of rigid out-of-plane displacement is automatically eliminated by taking the average strain of corresponding points from the left and right images. Two groups of tensile tests are conducted to verify the feasibility of the proposed 2D-DIC method. Experimental results show that: for uniform deformation, the biaxial results obtained using the proposed 2D-DIC method are in good agreement with those obtained using strain gauges; from the viewpoint of the nonuniform deformation, the strain fields of the proposed 2D-DIC method are in agreement with those of the finite element method. Therefore, the proposed 2D-DIC method has excellent strain measurement accuracy, and it is a convenient, effective, and highly accurate strain measurement method.