Work of crack propagation and fracture toughness of samples with a fatigue crack

Conclusions

• 1. In the presence of macroplastic deformation of a sample with a fatigue crack,a _c is not equal toa _p, and therefore equalitya _i=a _n−a _c holds true only when a straight undeformed fracture is obtained, when broadening ΔB≤0.4 mm.

• 2. A graphic method is presented for obtaining the true value of the work of crack nucleation and propagation that takes into account the contribution toa _c of the work of macroplastic deformation pertaining toa _i.

• 3. By use of this method it was shown that an increase of the sulfur concentration in low-alloy steel leads to a reduction ofa _n anda _c due to the sharp reduction ofa _i with a small change in componenta _p (for longitudinal samplesa _p increases somewhat with increasing sulfur concentrations).