The common feature of all fracture mechanical concepts is that an already existing surface defect (crack) is being assumed, having emerged either from production process e.g. as cavity, inclusion or stress crack or only within application e.g. by cyclic loading. Based on assumptions referring to the geometry and load of the surface defect, conditions are established via a viscosity measure, under which incorrect crack growth up to a break, this is exceeding fracture strength, develops. Thus, reliability of conventional strength calculation is to be improved.
Fracture mechanics by Merkle & Partner assumes existing cracks in a component and examines crack growth by means of calculated stress intensity factors from a finite element computation. This allows statements whether cracks grow, stop or an instable crack growth may develop.
Moreover, FE models allow to integrate failure criteria describing development and behaviour of a crack with complex geometries (crash, impact, containment).
Statements on crack growth in high-speed rotating components with maximum crack length, behaviour of cracks in rotor blades by contact with foreign matters, behaviour of cracks due to production failures etc.