An analysis of the conditions of brittle fracture origin

Local Criterion for Cleavage Fracture : Structural and Mechanical Approach

“…Nucleus cleavage microcrack is assumed to be sharp microcrack with the blunting equal to lattice parameter, start of which is defined by Griffith's condition. 5. If o12So (So -microcrack start stress) at the moment of sharp microcrack nucleation, this microcrack starts.…”

“…As local fracture criteria the suggested criterion for cleavage fracture (5) and ductile failure criterion [7] are used.…”

“…For equivalent stress beq and strain Eeq near the crack tip the following equation may be written according to (Dixon [16], Karzov and Margolin [17])…”

“…The distribution of stress oeeq near the tip of crack with the 6 blunting is expressed as [6] where r -the distance from the crack tip, p -Poisson's ratio. Coefficient PI is equal to 1/16.…”

“…The ozq and values in the unit cell of the size put are defined as [6] 1 -" -P r~z q (~) d~ =2(1-2p)--…”