Abstract
Digital image correlation (DIC) is a technique in experimental mechanics to acquire full-field measurement data of displacements and deformations from the surface of specimens or components. Especially for the investigations of cracks it provides additional benefits. The actually present deformation field in the vicinity of the crack tip can be obtained which directly reflects for example crack closure effects or plasticity. Against this background the paper summarizes a procedure to compute the J integral and the stress intensity factors KI and KII based on DIC data. For this purpose the J and interaction integral are computed as line and domain integrals. Through experiments it is shown that the domain integral is less affected by scatter of the DIC data. Furthermore, the specific domain, facet sizes and facet distances slightly influence the results.
Highlights
Fracture mechanical experiments are usually conducted and analyzed by the same well-established procedure
A n algorithm for the analysis of mode I and II stress intensity factors and J integral based on interaction and line integral is presented in detail in the first part of the paper
These integrals were implemented as a line and an equivalent domain integral
Summary
Fracture mechanical experiments are usually conducted and analyzed by the same well-established procedure. A formula for the estimated stress intensity factor for the specimen or structural part is needed. For standard specimens these formulae are found in handbooks [1]. The experiment is conducted and it is assumed that the actual stress intensity factors (SIFs) are in good agreement with the theoretical solutions. With the stereoscopic configuration of two cameras 3d information of local displacements can be derived [8] For this purpose, the DIC software subdivides the recorded images into smaller facets which are arranged like a (self-overlapping) checker pattern. The 3d coordinates of each facet can be computed based on the pairwise cross correlation of corresponding facets in both stereoscopic photographs Comparing these 3d coordinates over time yields the actual displacement
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