Stress wave emission and plastic work of notched specimens

The stress wave energy released from notched specimens of structural steel was measured in order to compare it with the recently proposedJ-integral which takes account of the effect of large plastic deformation around the crack tip in ductile materials. Very close agreement was observed between theJ-integral and the differential stress wave energy released. This suggests that the increment of the stress wave energy released is proportional to the decrement of the work done on the specimen during tensile testing under the plane stress condition. This result, combined with information obtained from linear elastic fracture mechanics, leads to a relationship between the differential stress wave energy released and the stress intensity factorK, Δ(SWER)/Δa] ∝K ². It was also found that in the region before general yielding, the stress wave energy release was proportional to the development of plastic zone size. A larger portion of the accumulated stress wave energy released was generated after general yielding due to void formation and coalescence. The accumulated stress wave energy released at the catastrophic crack growth point reached virtually the same value for each specimen, independent of the initial crack length. This implies that void formation and coalescence are not influenced by the initial crack length, but by the geometry of the crack tip.