Fracture resistance, characterized by the strength of the plastic stress singularity, was determined at failure load and crack length using three-dimensional elastic-plastic finite-element analysis of 29 A36 steel fracture specimens that had been tested at −50°F. This measure of fracture resistance was insensitive to specimen size, geometry, parent plate, and heat, provided that the specimens were either of full plate thickness or were taken from the mid-thickness of parent plates. On the other hand, the fracture resistance of full-thickness plates was not reliably estimated from fracture specimens taken from the thickness 1/4 point or near the surface of the parent plates. The computed variation in crack-front through-thickness response at 10% of maximum load was confirmed by comparison with elastic results. Elastic-plastic response at maximum load, including the tendency to more extensive yielding in smaller specimens, was similar to that indicated by other authors. Several parameter studies demonstrated the insensitivity of the results to the finite-element mesh design.

Fracture resistance of a structural steel as characterized by the strength of the plastic stress singularity

Fracture prediction based on plastic stress singularity strength

A three-dimensional, elastic-plastic fracture strength correlation for A36 and HSLA structural steel connections containing discontinuities was determined. The fracture specimens comprised beam-column connections in whichone column flange contained a mid-thickness plane of discontinuity. Beam loading or direct tension applied normal to the column face imposed tensile load transfer around the boundaries of the discontinuity. Fracture extension was mixed mode (crack opening and edge sliding), and inclined toward the free surface on the web side of the column flange containing the discontinuity. Successful correlation for these specimens was accomplished with a plastic stress singularity strength model, if the discontinuity was sufficiently large. The average singularity strengths at ultimate load were 64.6 MNm - 3 / 2 (58.7 ksi in. 1 / 2 ) for HSLA steels, and 53.7 MNm - 3 / 2 (48.8 ksi in. 1 / 2 ) for A36 steel. The percent coefficient of variation was 6.4 percent for HSLA steels and 8.4 percent for A36 steel.

BD Macdonald

Papers

Correlation of Structural Steel Fractures Involving Massive Plasticity