Quasiductile fracture

As it is known, the work of fracture U, characterizing expenditure of energy on material deformation up to failure, is one of the most important plasticity characteristics. In paper [5] it was shown, that the fracture character of solids is determined by the fractal dimension df of their structure at 4-2. 50 brittle fracture is realized, at 4 2.50-2.67 - quasibrittle (quasiductile) fracture and at 4 2.70 - ductile fracture. This classification allows to suppose plasticity increase characterized by value U at raising df. Actually, the dependence U dj) shown in Fig. 3 confirms this assumption. This dependence is linear, the increase U is observed at raising df and zero value U is reached at 4=2.50, i.e., at brittle fracture. Since limiting (maximal) value df for real solid is equal to 2.95 then this allows to estimate... 

The fiacture surface fractal dimension at quasibrittle fracture is determined according to the Eq. (4.50) and at quasiductile fracture - according to the Eq. (4.51). And at lastthe value for fractal Griffith crack d can be estimated according to the Eq. (5.17) at the condition tn = 2. 

As it has been noted in chapter five, the local plasticity zone type defines the fracture type if a craze forms at critical defect tip, then polymer failed quasibrittle and if deformation zone (ZD) or local shear yielding zone ( shear lips ) - then quasiductile [13]. The inelastic deformation mechanism change is considered as brittle-ductile transition [14]. The treatment of the indicated tiarrsition will be considered below within the frameworks of both cluster model and solid body synergetics. 

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