Volume 17, Issue 1 (January 1989)
Effects of Small Surface Cracks on Ductility Loss in Low Cycle Fatigue of 70/30 Brass
The loss of fracture ductility after strain cycling in low cycle fatigue tests is not due to so-called weakening or losing of the strength quality caused by irreversible slips in crystals but rather is attributable to the existence of small surface cracks. The degree of loss of fracture ductility depends on the crack length ℓ. If ℓ is larger than the critical length ℓc, the fatigue crack causes macroscopic shear fracture in the tensile test after strain cycling. On the other hand, if ℓ < ℓc the fracture surface becomes the so-called cup-and-cone type. For 70/30 brass, ℓc ≅ 400 µm.