Issue 49

M. Bannikov et alii, Frattura ed Integrità Strutturale, 49 (2019) 383-395; DOI: 10.3221/IGF-ESIS.49.38 391 0 0 0 0 4 0 0 4 4 4 4 4 4 4 0 0 4 0 0 4 0 0 1 1 exp( ) exp( ) 1 n U n n n n U p U kT kT U p U U p U U p p kT kT                           . Then the kinetic coefficients will have the following form: 0 i n i U i ε G     , 1...3 i  , 0 4 4 n U p G      . We introduce the notation: 1 1 0 n ε      , 2 2 0 n p ε      , 3 3 0 n p ε     , 4 0 n p       , 1 2 n n n    , 2 3 p n n n   . The final determining equation is the fracture criterion. In the framework of the proposed model, we can enter a criterion based on the structural scaling parameter: 0 δ  (22) The meaning of this criterion is that the percentage ratio of the volume of material occupied by defects tends to 100%, which can be achieved by tending to zero the distance between defects or tending to infinity of the size of defects. The second option is impossible, and the first has a clear physical meaning. In the calculation, the condition (22) is not realizable due to the instability, as it is, therefore, we can replace it with a softer one: f δ δ  (23) where 0.4 f δ  is the critical value [22], after which the avalanche-like growth of defects begins and the material is considered destroyed. This value is universal for all plastic materials for the proposed model. Critical value f δ δ  corresponds to critical value c p . Model Parameter Identification The identification of the parameters of the constructed model (15)-(19) was carried out in the uniaxial case: 2 ( ) p σ λ G p             (24) 0 ( ) n p p F ε σ p             (25) 0 ( ) p n p p F p ε σ p          (26) 0 n F δ p δ          (27) 2 2 2 1 2 3 4 ln( ) 2 2 2 m p p σp F c p c c c p p F δ G        (28)