METHOD FOR STRAIN MEASURMENT OF SHEET MATERIAL AND ITS APPARATUS

摘要

The present invention relates to a sheet-strain measuring system, and a method which detects a change in pattern after press-forming is finished using an image of the pattern to measure a strain rate of a sheet material which occurs due to press-forming. The sheet-strain measuring method comprises: a step of attaching a reference grid used as a reference to measure a strain rate of the sheet material, caused by press-forming, to a predetermined portion of the sheet material; a step of acquiring an image of the reference grid and a plurality of images of the grids which are deformed through the press-forming process by capturing images of the press-formed sheet material using a camera module; a step of calculating a diameter of the reference grid using information of the number of pixels of the reference grid attached to the sheet material which has undergone the press-forming; and a step of calculating the lengths of a long axis and a short axis of the deformed grid based on the information of the number of pixels of the deformed grid, and calculating a maximum strain rate and a minimum strain rate by comparing the diameter of the reference grid and each of the lengths of the long and short axes of the deformed grid.