Application of DSCM in prediction of potential fatigue crack path on concrete surface

Prediction of potential fatigue crack paths on the surfaces of concrete structures was a difficult task in the past. To complete this task a Finite Element Method simulation by computers is usually employed, but bearing in mind that the numerical results are not always consistent with the experimental ones because of the effects of various environmental factors and construction quality on concrete structures. In order to inspect the damage process during the service life of structures and to confirm their detailed plan of repair and reinforcement, a new non-destructive technology is used for on-line health inspection of many important concrete structures in the world. Fortunately, along with the development of Digital Speckle Correlation Method (DSCM) in the last two decades, this new non-destructive technique has presented many advantages. To testify the feasibility and accuracy of this system, two series of concrete specimens were tested under flexural fatigue loading and a software UU(C) matched to DSCM was employed in this work. DSCM can get full-field and local displacements by comparing two speckle images on target surfaces before and after deformation. Then the full-field and local strain fields on these regions can be deduced from the longitudinal and transversal displacements. By analysis of these strain fields, the starts of potential fatigue crack paths can be predicted precisely. It is testified that DSCM system is accurate and effective in on-line prediction of potential fatigue crack path of specimens made of heterogeneous materials under flexural cyclic loading. The fractural mechanisms of the two concrete series under flexural cyclic loading were discussed. Note that the fatigue testing conditions should be kept still and clean in order to produce precise results of DSCM system. (C) 2007 Elsevier Ltd. All rights reserved.