Experimental Fracture Assessment Diagram by Ultimate Crack Resistance

摘要

The report is devoted to application of the two-parameter fracture criterion to experimental results for the specimens with cracks. Tension specimens were cut out from the defective rolled steel plate with stratifications in the middle of its thickness. The plate thickness is 100 mm and the length of the specimens is same. In the middle of specimens there were cracks of different shapes and sizes which were measured after specimen fracture. The maximum critical (fracture) load was recorded. For each crack configuration, at a known fracture load, there were critical stress intensity factors. Crack sizes, fracture loads and character of fracture for all specimens were different. Therefore critical stress intensity factors are also different. By the definition, these factors are called the ultimate crack resistance [Morozov, 1968]. Dependence of the ultimate crack resistance on the fracture stress is called the failure assessment diagram (two-parameter fracture criterion). Experimental points well correspond to approximating function proposed earlier. Comparison of the ultimate crack resistance approach with the failure assessment diagram given in Document R6 showed considerable conservatism of the R6 crack resistance estimation.