1975 年 24 巻 266 号 p. 1057-1064
The effect of deep freezing on the fracture behaviors of solid polymers has been investigated experimentally as a fundamental study of industrial cryogenic crushing operation. The apparatus used is shown in Fig. 1, which consists of an universal testing machine and a cryogenic thermostat with liquid nitrogen.
As the temperature drops below the ductile-brittle fracture transition temperature Tc, the material becomes brittle and fracture takes place in the elastic range after a very small elastic deformation (Fig. 3).
At higher temperatures T>Tc, the material stretches elastically until the yield stress is reached, whereupon the nominal stress decreases quite rapidly to a lower value with the appearance of a neck. The strain produced increases with temperature (Fig. 4).
The homologous true breaking stress σB/σBc, the reciprocal homologous breaking strain εBc/εB, the homologous longitudinal elastic modulus E/Ec, the homologous crushing initiation index CII/CIIc, and the homologous crushing extension index CEI/CEIc increase with the reciprocal homologous absolute temperature Tc/T as given by Eqs. (5)∼(17) (Figs. 7∼16). The values of Tc, σBc, εBc, CIIc and CEIc at the ductile-brittle fracture transition temperature are the material-constants.
The true tensile stress-strain curves and the tensile load-elongation curves for solid polymers at several temperature levels are shown in Figs. 9 and 10.