A Forming Limit Curve Measurement of Sheet Metal Based on Digital Image Correlation

The Forming Limit Curve (FLC) is a key indicator of the sheet metal forming property. It is inconvenient to use general ways like tool microscope to obtain FLC after corroding and forming mesh on sheet metal's surface. Therefore, a fast and accurate FLC detection system is proposed in this paper. First, the image sequences are captured by the high-speed camera automatically while the sheet metal is forming during the cup drawing test. Second, by tracking the speckle images of the sheet metal's surface with Digital Image Correlation (DIC) and binocular stereo vision, 3 d (three dimensional) coordinates and the full field deformation and strain on sheet metal's surface are acquired accurately in the process of sheet metal forming. And then, combined with the space interpolation, the method based on the strain history makes data points extracted from cutting line more accurate, so that the calculated curve is closer to reality. The method provides experimental evidence for sheet metal's forming theory research and validation and material selection. Finally, this method is also applied in the measurement of magnesium alloy of auto parts.