Relationship Between Fracture Toughness and Estimated Plastic Zone Size in Steel, Titanium, and Aluminum Alloys

摘要

The area of plastic deformation at a crack tip can be estimated using Irwin's plastic zone correction factor derived from linear elastic theory. The size of the plastic zone is considered to be a measure of fracture toughness, since the resistance of a metal to crack propagation is related to the deformation ahead of the crack tip. The relationship is confirmed between fracture toughness and plastic zone size calculated from elastic considerations for steel, aluminum, and titanium alloys. Within each of the metal systems, the calculated plastic enclave increases with increasing Dynamic Tear (DT) test energy for fracture. However, the plastic zone size is an unreliable indicator of the amount of energy absorbed in the formation of the zone when a comparison is made among different metal systems. For a given size plastic enclave, the energy absorbed by the metal during the deformation process is least for aluminum alloys, while significantly greater for titanium and steel alloys in that order. When brittle alloys are compared, the difference among metal systems in the quantity of energy absorbed to form the zone is considerably diminished. (Author)