Athermic fracture stress

It was also found [6], that in this case experimentally determined values of athermic fracture stress turn out to be essentially (2 3 times) smaller than theoretically calculated ones. A small values k 0.2 1.0) is one more important feature of nonoriented polymers fracture in impact tests. This means, that the stress on breaking bonds is essentially lower than nominal fracture stress of bulk sample. And at last, it was found out [7], that the value k reduces at testing temperature growth and the transition from brittle fiactuie to ductile (plastic) one. These effects explanation was proposed in Refs. [4-7], but development of fractal analysis ideas in respect to polymers lately and particularly, Alexander and Orbach woik [8] appearance, which introduced the fraction notion, allows to offer the major treatment of polymer fracture process [9, 10], including the dilaton concept [1-3] as a constituent part. 

Thus, at the athermal limit of spontaneous fracture the above free energy must be equal to the product v <7f, which, for <7f = 1.67 GPa obtained from Fig. 12.21, gives V = 1.88 x 10 m. Using these values, a consistency check with the time-dependent fracture behavior of Nylon under stress was performed by Zhurkov et al. (1969), the result of which is of interest. Namely, from the specific case reported by them it must be concluded that, if fracture can occur 10 s after... 

In equation (3.146) the first term reflects the contribution of from thermo-fluctuational stage of fracture and the second one represents the contribution of the athermal factor. The theory introduces the notions of limit stress, o, for the crack generation, and critic stress, which were practically confirmed [847, 848],... 

---