Direct mixed-mode I&II partitioning in beam-like geometries using Digital Image Correlation and the decomposed J-integral

Abstract

In the current work, a direct method of mode partitioning is developed, based on the application of the partitioned $J$-integral to strain fields directly measured using Digital Image Correlation. The method has first been validated using strain fields obtained from Finite Element Analysis of Double Cantilever Beam, End-Loaded Split and Fixed-Ratio Mixed-Mode test specimen geometries. Then, a Cracked Lap Shear specimen has been designed, modelled and tested. Very good agreement was achieved for all standard specimens. As for the Cracked Lap Shear geometry, there are no accepted partitioning solutions. The new direct mixed-mode partitioning method results in $\frac{G_I}{G_{II}}=0.35$. This method has also been successfully extended to asymmetric cases using the Asymmetric Fixed Ratio Mixed Mode test specimen with 5 different beam thickness ratios: $\gamma$ = 0.5, 1, 1.8, 3 & 3.94. The results are found to compare very well with both FEA and the semi-analytical cohesive analysis (SACA) partitioning method from Conroy et al. (2015).