Displacement Smoothing and Strain Estimation Using Savitaky-Golay Filters in Digital Image Correlation

Abstract

Recently, many research works were concentrated on how to improve the accuracy of displacement fields in digital image correlation (DIC). However, the original displacement fields calculated at discrete locations using DIC are unavoidably contaminated by noises. If the strain fields are directly computed by differentiating the original displacement fields, the noises will be amplified even at a higher level and the resulting strain fields are untrustworthy. To acquire reliably estimation of strain fields, in this paper, Savitaky-Golay (SG) filters are introduced to obtain smoothed displacement fields and reasonable strain estimation. The principle of two-dimensional SG filters is described in detail first. Then images of uniaxial tensile and three-point bending experiments were used to verify the proposed approach. The resulting smoothed displacement fields and strain fields clearly show that the proposed method is simple and effective.