Wrinkling modes of sheet metal during press forming measured by optical reflection of grating

摘要

The surface deflections are measured during press forming by the following optical method. The number of the wrinkles on the sheet metal can be observed by the behaviors of the parallel straight-line gratings, which are reflected on the mirror-like surface of the sheet metal. When the surface of the sheet metal shows concave or convex, the pitches of the gratings are broadened or narrowed. Applying moire method, the wrinkling can be observed more precisely. The variations of the wrinkling during press forming are observed clearly.