Autowave Model of the Transition from Stable Plastic Flow to Ductile Failure in Solids
Lev Zuev (Institute of Strength Physics )
Plasticity at Different Length Scales
Mon 4:20 - 5:40
CIT 219
A new approach is proposed to explain localized plastic flow acting in deforming solids. The plastic flow investigations were carried on using speckle interferometry technique. The plastic flow is found to localize at the micro-, meso- and macro-scale levels. The macrolocalization patterns of plastic deformation are generated spontaneously and are essentially wave-like in character. The analysis and interpretation of the experimental evidence led us to conclude that solids’ response to mechanical loading is a specific autowave process, which has wavelength ~10-2 m and propagation rate 10-5…10-4 m/s. A one-to-one correspondence has been established between the autowave types on the one hand and the well-known work hardening stages on the other hand. An invariant of elastic-plastic deformation is introduced using lattice constant, elastic wave rate and plastic flow wavelength and propagation rate. In the framework of this approach the plastic deformation is considered as evolution of the wave process of localized plastic flow. An analysis of the kinetics of localized plasticity nuclei with growing total deformation level reveals that the nuclei arrive practically simultaneously at the place where viscous crack is being initiated to merge together at one and the same point. It is, therefore, concluded that the life span of the specimen and the location of fracture are determined by the processes that had occurred at the earlier stages of plastic flow. At the end of the parabolic stage where all the flow nuclei are stationary ones there forms a high-amplitude localized deformation maximum whose location pinpoints the place of future necking. Its formation marks off the beginning of the final flow stage, which is distinguished by a concerted motion of hitherto stationary localization fronts, the farther away is the nucleus from the neck location, the greater is its motion rate.