Cast iron crack tip′s evolvement measured by DSCM

The principle of digital speckle correlation method(DSCM) was introduced,and the sub-pixel searching algorithm based on gradient was used to compute displacement.The strain fields were computed by least-square fitting of local displacement.The crack tip's evolvement of cast iron three-point bending beam with pre-crack was measured.The load-displacement curve and the process of crack growth were given during the specimen damage.The displacement field and stain field near crack tip at different load were given by DSCM.This study provides experimental basis for researching brittle materials' damage and fracture process,and also provides an effective experimental way for studying damage and fracture process of structures with crack.