Evaluating J‐integral from Displacement Fields Measured by Digital Image Correlation

Abstract

Path integral, domain integral and least squares methods for evaluating J-integral from measured displacement fields for a power-law hardening material are described in this paper. The values of the J-integral are evaluated by applying the path and domain integral methods to the displacement fields obtained by elastoplastic finite element analysis and the displacement fields obtained through the measurement using digital image correlation. Results show that the values obtained by the domain integral method are slightly better than those by the path integral method, because the domain integral method efficiently uses the full-field measurement data. The values of the J-integral are also evaluated by the least squares method with the Hutchinson, Rice, and, Rosengren displacement fields. Results show that the J-integral can be obtained by the least squares method simply and easily without any calculation of the integration. The J-integral values obtained by the least squares method agree well with the values obtained using other methods. Because J-integral can be evaluated easily by any method described in this paper, it is expected that these methods are applicable to various fracture problems during experimental evaluation of structural components.

Procedure for accurate calculation of the J‐integral from digital volume correlation displacement data

“…The application of digital image correlation (DIC) and digital volume correlation (DVC) techniques to obtain displacement data fields from images has become ubiquitous in experimental fracture mechanics. Many examples now exist that demonstrate the successful extraction of fracture parameters, such as stress‐intensity factors obtained by McNeill et al, Lim et al, and Roux et al; mixed‐mode problems addressed by Rethore and Gravouil, Yoneyama et al, and Sistaninia et al; and energy approaches such as the J ‐integral by Yoneyama et al8 and the authors of this work, to name but a few.…”

J-integral evaluation for an interface crack under thermal load using digital image correlation

“…In previous study, the stress components are often calculated by modeling the stress-strain relationship. 7,8,11,15 However, the constitutive model does not always approximate the stress-strain relationship of target material correctly. Therefore, in this study, the stress components are calculated from the strain components without modeling the stress-strain relationship.…”

“…On the other hand, Yoneyama and coworkers 11 have evaluated J-integral from the measured displacement fields obtained by DIC using the method of the path-integral and the domain-integral. From that result, the method of the domain-integral can be reduced the effect of the measurement error comparing the method of the path-integral.…”

Measurement of discontinuous displacement/strain using mesh-based digital image correlation

“…An example of a region such as this would be the one where a crack is included within a subset. Although there have been studies [3][4][5][6] that apply DIC to the displacement measurement around a crack, there exists a case where these studies do not employ the displacement there. Similarly, there is the problem of the measurement accuracy decreasing when the subset includes background around a free edge.…”