ABSTRACT
A laboratory specimen and a flawed structure experience identical crack tip conditions at failure when the single-parameter assumption is valid, and it is not necessary to delve into the details of microscopic failure to characterize global fracture. A fracture toughness test on a small-scale laboratory specimen is no longer a reliable indicator of how a large structure will behave. The fracture toughness of the structure and test specimen are likely to be different, and the two configurations may even fail by different mechanisms. This chapter focuses on ferritic steel, because it is the most technologically important material that is subject to cleavage fracture. Cleavage fracture can be defined as rapid propagation of a crack along a particular crystallographic plane. Two nominally identical specimens made from the same material may display vastly different toughness values because the location of the critical fracture-triggering particle is random.
