Papers by Author: Yan Fang

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.

Abstract: In this paper, the residual deformation induced in laser welding processing was studied by using the moiré interferometry and a novel high-temperature specimen grating technology. The experimental results indicate that the heat-affected zone of laser welding is a narrow strip. There exists great residual strain gradient in the heat-affected zone, especially great residual shear strain gradient. It implies that great residual stress and stress gradient exist near the welded seam. The relationship between the size of the heat-affected zone and the changes of the technology parameters were discussed in the experiments, which can supply some reliable experimental data for optimizing processing technology.