2018 年 91 巻 8 号 p. 316-323
Following the previous first half where the fundamental concept named the elastic-viscous transition phenomenon with velocity jump was introduced, here the authors propose a new physical aspect for the mechanism of the elastic-viscous transition and the velocity jump in comparison with the phase transition of water. The vibrational energy of the stick-slip motion converted from the additional external strain energy works as a driving force to promote the velocity jump keeping a fixed strain energy release rate Gtip. It is quite similar the situation when the latent heat supplied by an external heating source causes a volume jump by keeping the temperature constant in the phase transition of water from liquid to vapor.
The greatly increased vibrational energy as the crack growth rate increases might be consumed to propagate ductile fractures of the newly induced fraction of the glassy state in the glass transition process from the rubbery to glassy state, resulting in the velocity jump in the transition zone. In this process, the vibration of much higher frequency (a few KHz) generated coupled always with the stick-slip motion may expand the crack tip and initiate cavitation, and hence accelerate the tear fracture drastically ahead of the crack tip in soft visco-elastic rubbers.
