Fig. 3 Probability - loading level - damage state Fig. 4 Samples of load - crack propagation
THE EFFECT OF INITIAL CRACK DEPTH ON THE BEND SPECIMEN CRACK GROWTH RESISTANCE CURVE FOR A CONCRETE-TYPE MATERIAL
E. SMITH Materials Science Centre, University of Manchester/UMIST
Grosvenor Street, Manchester Ml 7HS, UK
Concrete-type materials have the characteristic that when a crack grows, a partially fractured ligament zone forms behind the crack tip, and the restraining stresses provided by the crack bridging elements within this zone are responsible for the crack tip stress intensity factor increasing during crack growth, thus leading to an effective toughening of die material. The edge crack-finite width bend specimen is frequently used to determine the stress intensity (K) - crack growth (R) curve, and this paper examines the effect of the initial crack depth on the shape of the K-R curve. A theoretical analysis shows that for a given specimen width, and as crack extension proceeds, the general level of the K-R curve is higher the greater is the initial crack depth.