Measurement of Evolutionary Process of Concrete Crack Tip by DSCM

The basic principles of DSCM(digital speckle correlation method)were explicated.The integer pixel search was carried out by the mountain-climb searching,and the subpixel displacement was calculated based on the gradient searching algorithm and the strain field on the least-square fitting of local displacement.The authors measured the evolutionary process of crack tip on 3-point bending concrete beam to present the load-displacement curves in specimen loading and the crack expanding process,and obtained from DSCM analytical results the displacement and strain fields of crack tip with the specimen under different loads,which provides an effective experimental method for probing into the fracture and damage of materials and structures with discontinuities.