Abstract
In the previous report (report1)1), it became clear that introduction of the concept of dissipated fracture surface energy (Gc) during each crack propagation step is needed for good correspondence between numerical crack propagation analysis (3D-FEM dynamic analysis using local stress criterion2)) and experiment of small CCA (Compact Crack Arrest) specimen. In this paper, Gc concept is applied to ultra wide tensile problem which is representative for much major structure. Hypothetical Gc are arranged as the calculated crack propagation rate shows experimentally obtained range in three stress level conditions. As a result, Stress field around the running crack tip is increased as crack propagates and saturated at the point of Knom/σY･√ t=4. This saturation tendency is good correspondence with famous Keff concept3) Next, in order to understand the intrinsic meaning of Gc and the change of Gc subjected to driving force, brittle fracture appearance were observed by small specimens fractures under various stress field. It is revealed that under high driving force condition roughness of fracture surface tends to increase and many sub-cracks are observed. These observations are qualitatively supporting the appropriateness of hypothesis of Gc.
