CE 5310 Lecture Notes - Lecture 1: Fracture Mechanics, Stress (Mechanics), Extrusion
Document Summary
Fracture, fatigue mechanisms and microscopic features of ductile metal. Any fracture process involves two steps crack formation and propagation in response to an imposed stress. The mode of fracture is highly dependent on the mechanism of crack propagation. Ductile fracture is characterized by extensive plastic deformation in the vicinity of an advancing crack. Furthermore, the process proceeds relatively slowly as the crack length is extended. Such a crack is often said to be stable that is, it resists any further extension unless there is an increase in the applied stress. In addition, there typically is evidence of appreciable gross deformation at the fracture surfaces (e. g. , twisting and tearing). For brittle fracture, cracks may spread extremely rapidly, with very little accompanying plastic deformation. Such cracks may be said to be unstable, and crack propagation, once started, continues spontaneously without an increase in magnitude of the applied stress.
