The classical potential drop technique [
] is used to measure a growing crack in a conductive material and has been a standard methodology for measuring “open” cracks, i.e. those propagating in predominantly mode I (tension). In tension the electrical modeling is rather straightforward since a known electrical current passes through the body of the tensile specimen and the developed voltage due to the constantly changing resistance as the crack propagates is measured at two electrodes fixed at both sides of the developing crack. In mode II (in-plane shear) however there is little data available in the existing literature as the issue of generating a pure and uniform in-plane shear stress field on a specimen (i.e. without the existence of bending or any other normal stresses) is still open and under discussion.