The critical tensile stress criterion for cleavage

Abstract

An elastic-plastic analysis was used to accuratel~¢ measure the microscopic cleavage strength o~of notched bars of high nitrogen steel in bending. It was found that o~f increases as the root radius of the notch/9 decreases. For/9 > 0.010", the variation of o~f with p, and the difference between 0~f and the cleavage fracture strength of a plane tensile specimen, of, may result from a statistical effect, due to differences in the volume of highly stressed material in the plastic zone• For/9 < .010", the primary reason for the apparent increase in o~f with decreasing p, is the steep stress gradient at the notch tip, which forces the critical plastic zone size to extend further to insure that unstable microcrack propagation can occur. Both the statistical and stress gradient effects have been quantitatively evaluated and found to be in good agreement with the experimental data.

Some effects of yield strength on the stress corrosion cracking behaviour of low alloy steels in aqueous environments at ambient temperatures

“…Furthermore, they advocated that a necessary condition for fracture was that the local flow stress within the crack tip enclave must exceed some critical value before secondary cracks can be initiated. Basically, this model implies some critical distance concept, called L Ã , which is similar to that employed by other reseasrchers [24,25] and this is illustrated schematically in Fig. 8.…”

Refined Dugdale plastic zones of an external circular crack

“…In two-dimensional (2D) analyses, Hill (1949) derived an upper-bound solution for the notched ideal plastic-rigid material. Hill's main conclusion shows that the limit load increases with the decreasing flank angle of the notch (Tetelman et al, 1968), and attains its maximum value when the notch angle turns to 01 (a sharp edge-crack). Considering the notches are deep enough that the plasticity is confined in the ligament, Rice et al (1973) developed the J-integral formula for the double-edge-notched plate in tension.…”

Effects of loading rate, notch geometry and loading mode on the local cleavage fracture stress of a C–Mn steel

“…4.3 Effect of notch geometry on the local cleavage fracture stress Tetelman et al (1968) investigated the effect of notch root radius on the local cleavage fracture stress σ f by means of slip-line field analysis. They suggested that when the root radius was larger than 0.254 mm, σ f may vary with root radius, because of differences in stressed volumes.…”

“…It is well known that the cleavage fracture of ferrite steels is controlled by a critical local tensile stress criterion (σ yy ≥ σ f ) (Knott 1966;Tetelman et al 1968;Ritchie et al 1973; Thompson and Knott 1993). A salient feature of cleavage fracture is the variability of experimental results.…”