Effect of gage length on failure strain

Failure prediction in crash analyses of ships has traditionally made use of an equation that relates the failure strain to the gage length and material thickness. The equation is derived based on the idea that a neck ( a localization of strain) is a fixed size relative to the thickness and that it can be homogenized over a larger gage section. The fact that DIC allows for the gage length to be retroactively changed after the test (so long as all of the gage section has a random pattern and falls within the view of the camera) allows these hypotheses to be tested. Tests of two different scales have been performed and analyzed with DIC. The results confirm this fundamental assumption that has been at the core of failure modelling in crash analyses.