Brittle Fracture

Recent experimental work on brittle cleavage fractures in iron and steel has shown that these failures originate with cleavage microcracks. Microcracks with lengths of one grain diameter and longer have been observed in tensile specimens that have been unloaded just below the fracture stress. It has also been shown that local plastic flow of the order of the yield strain occurs prior to the formation of these microcracks even though the subsequent failure involves very little overall deformation. Some of the current dislocation theories predict the formation of microcracks of this type, and the correlation between theory and experiment is encouraging.