Fracture mechanics is a field which recognizes that all structures are manufactured with, or will ultimately contain, flaws that govern the eventual failure of the structure. The study of the stresses caused by the flaws and the material's resistance to failure from them form the basis for the field of fracture mechanics. Fracture mechanics provided, for the first time, the capability to calculate the strength of structures containing defects that inevitably occur in fabrication or during service operation. The net result of these design principles increased the reliability of structures as the result of improved design capability and an improved predictive capability of in-service damage.

NRL's G.R. Irwin is recognized as the pioneer of modern fracture mechanics. He developed the scientific principles for understanding the relationships between applied stresses and cracks or other defects in metallic materials. Around 1947, Irwin developed the concept that fracture toughness should be measured in terms of resistance to crack propagations. Critical values of the stress intensity describing the onset of fracture, the onset of environmental cracking, and the rate of fatigue crack growth were established later.

Fracture mechanics has been applied throughout the world for the design of any structures where sudden, catastrophic failure would cause loss of life or other serious consequences. Examples include nuclear reactor pressure vessels, submarines, aircraft and missiles, and tanks for storage of toxic or flammable materials.