Steady-state flow experiments to visualise the stress field and potential crack trajectories in 2D elastic-brittle cracked media in uniaxial compression

An experimental method to visualise crack-induced perturbations of the stre ss field in two-dimensional elastic cracked media is presented. The method is based on the formal equivalence between the steady-state velocity field of an incompressible Newtonian fluid and the displacement field in an incom pressible elastic solid in equilibrium. Two-dimensional steady-state flow e xperiments of an incompressible Newtonian fluid were conducted in a Hele Sh aw cell. Thin rubber inclusions were inserted in the cell to model pre-exis ting cracks. The streamlines around the obstacles were visualised by inject ion of methylen blue dye into the flow. Several experiments were conducted in which different configurations of cracks were modeled: (1) one single crack inclined to the flow direction; (2) left-stepping en echelon cracks with different step-overs; and (3) randomly distributed cracks. The results compare well with the available experimental data on crack grow th in elastic plates under uniaxial compression and demonstrate the ability of the method to accurately account both for cracks induced perturbations and potential crack trajectories in elastic media. Different mechanisms of crack interaction such as screening or enhancing effects are illustrated by the experiments.