Progressively, the stress transfer along the crack is accompanied by a decrease of the tensile stress field around the crack tip, with final values around 250 MPa. Further propagation of the crack would require building a sufficient stress field at the tip of the crack to break the asperity on which it is now pinned. The sub-critical propagation is promoted by the initial high tensile stress surrounding the crack tip at point 1. When the loading force is maintained constant, and as long as the stress at the crack tip exceeds the fracture properties of the interface, the crack propagates by jumping from one defect to the other. It took about 2 hours to jump from point 2 to point 3.