It can be shown that the energy required for fracture,聽Gc, is a function of the stress,聽蟽, the crack length,聽a, and the modulus,聽E, such that:
This equation can be rearranged to give:
From this equation a stress intensity factor,聽K, can be defined:
We can therefore say that fast fracture occurs when a critical stress intensity factor,聽Kc, is reached, ie.聽K= Kc. Kc聽is referred to as the fracture toughness of the material.
滨蹿听Kc聽is known the following can be derived from the equation:
- The crack length,聽a, that will result in fast fracture for a given applied stress.
- The applied stress,聽蟽, that will result in fast fracture for a given crack length.