Strain energy release (Irwin's modification for plane stress)
A fracture is the separation of an object or material into two, or more, pieces under the action of stress.There are three ways of applying a force to enable a crack to propagate:
Mode I fracture – Opening mode (a tensile stress normal to the plane of the crack),
Mode II fracture – Sliding mode (a shear stress acting parallel to the plane of the crack and perpendicular to the crack front), and
Mode III fracture – Tearing mode (a shear stress acting parallel to the plane of the crack and parallel to the crack front).
Irwin showed that for a mode I crack (opening mode) the strain energy release rate and the stress intensity factor are related.
|G1||Strain energy release rate (J/m2) (dimensionless)|
|K1||Stress intensity factor in mode I (Pa*m1/2) (dimensionless)|
|E||Modulus of elasticity ( Young's modulus) (Pa) (dimensionless)|