Where does fracture collide?

The separation of a solid body into pieces under stress, treated as the growth of a crack once the elastic strain energy released by extending it exceeds the energy needed to create the new surfaces. Griffith's 1921 The phenomena of rupture and flow in solids set out this energy criterion for brittle failure, and later fracture mechanics expressed a material's resistance as its fracture toughness, the critical stress intensity factor K_IC at which a crack runs unstably. Ritchie's 2011 review contrasted brittle and ductile fracture and the trade-off between strength and toughness. The referent is the mechanical failure of an engineered or natural solid, quantified in energy and stress-intensity terms, not a break in a living bone or a discontinuity mapped in the crust.[1][2]

Unit

A material's resistance to crack growth, as fracture toughness K_IC

Recovery means

Not applicable, since fracture in a brittle solid is an irreversible loss of continuity

Measured by

Assessed by fracture toughness tests that load a pre-cracked specimen to find the critical stress intensity factor or the critical strain energy release rate

A break in the continuity of a bone, produced when the load applied exceeds what the bone can bear, and classified by the pattern of the break, such as transverse, oblique, spiral, comminuted, or greenstick, and by its site and mechanism. Court-Brown and Caesar's 2006 Epidemiology of adult fractures described how such breaks distribute across the skeleton, the age and sex patterns of who sustains them, and the injuries that cause them. The referent is a clinical injury to a living skeleton, diagnosed on imaging and mended by biological repair, and it is not an energy criterion for a cracking specimen or a joint set logged in rock.[3]

Unit

A break in bone continuity, classified by pattern, site, and mechanism

Recovery means

Bone heals by forming a callus and remodelling, so a fracture can reunite and restore load-bearing over weeks to months

Measured by

Diagnosed and classified on radiographs and CT using pattern-based schemes, and followed clinically until bony union

A surface or narrow zone in a rock mass across which the rock has lost cohesion, spanning joints, along which there has been no appreciable shear, and faults, along which the two sides have slipped past each other. Bonnet and colleagues' 2001 Scaling of fracture systems in geological media treated fractures as networks whose lengths, spacings, and connectivity often follow scaling laws and largely govern how fluids move through otherwise low-permeability rock. The referent is a permanent structural discontinuity in the crust, mapped and characterised in the field and the subsurface, and it has nothing to do with a laboratory toughness value or a broken bone.[4]

Unit

A cohesion-losing surface in rock, described by orientation, length, and connectivity

Recovery means

Not applicable on human timescales, though open fractures may later be sealed by mineral cementation over geological time

Measured by

Characterised by mapping orientation, length, spacing, and aperture, and by tracking the fluid flow that the fracture network conducts