Comparison of J(sub Ic) and J-R Curves for Short Crack and Tensilely Loaded Specimen Geometries of a High Strength Structural Steel

摘要

The paper describes an experimental program which had the objective of developing a series of J-R curve data from laboratory specimens of varied constraint. Constraint was varied by testing specimens with different thicknesses, crack lengths, and mode of loading. All specimens were relatively small and were kept simple in geometry and loading to allow estimation of the applied J integral. All tests were conducted on high strength structural steel, at ambient temperature, on the ductile upper shelf for the alloy. Results of these tests have shown that different constraint condition can dramatically affect the J(IC) and the J-R curve for the full range of crack lengths and loading modes studied here. The results are compared in terms of the 'T Stress' (T omega) parameter and the Q constraint parameter, but the trends in the data do not seem to correlate well with either parameter. Although both the T omega and Q parameters predict that the single edge notched tensile bar (SE(T)) would have relatively high constraint, the geometry demonstrated the highest J(IC) properties. The double edge notched bars were predicted by the T omega or Q parameters to be a low constraint geometry, however the geometry resulted in J(IC) results lower than those measured on standard deeply crack bend bars.