MEASUREMENT OF LÜDERS BAND IN SMALL SIZE LOW CARBON STEEL SPECIMEN BY 3D DIGITAL IMAGE CORRELATION METHOD

Lüders band is phenomenon of stripped fold on material surface which is caused by the inhomogeneous deformation during the yield stage. It can reduce the quality of stamped parts' surface so that it is important to study the Lüders band in order to prevent it from appearing. To complete the observation and analysis of Lüders band in small size low carbon steel specimen, the 3D digital image correlation method under small view field (15mm×15mm) was used to realize the deformation measurement. The formation mechanism of Lüders band was studied and the change of strain and strain rate during the propagation of Lüders band was analyzed. Experimental study demonstrates that the 3D digital image correlation method is able to carry on the observation of meso-mechanical behavior like Lüders band and necking fracture. It provides an effective means for studying meso-mechanism of deformation.