Stress relaxation in vanadium under shock and shockless dynamic compression

Abstract

Evolutions of elastic-plastic waves have been recorded in three series of plate impact experiments with annealed vanadium samples under conditions of shockless and combined ramp and shock dynamic compression. The shaping of incident wave profiles was realized using intermediate base plates made of different silicate glasses through which the compression waves were entered into the samples. Measurements of the free surface velocity histories revealed an apparent growth of the Hugoniot elastic limit with decreasing average rate of compression. The growth was explained by “freezing” of the elastic precursor decay in the area of interaction of the incident and reflected waves. A set of obtained data show that the current value of the Hugoniot elastic limit and plastic strain rate is rather associated with the rate of the elastic precursor decay than with the local rate of compression. The study has revealed the contributions of dislocation multiplications in elastic waves. It has been shown that independently of the compression history the material arrives at the minimum point between the elastic and plastic waves with the same density of mobile dislocations.

Phase transition of iron-based single crystals under ramp compressions with extreme strain rates

“…It is generally recognized that the phase transition begins with homogeneous nucleation and exhibits a supersonic growth speed at the early stage of the nucleation. Despite of some similarities shared between the uniaxial uniform compressions and uniaxial shock compressions, there are still some distinctive features for the phase transition under dynamic loadings due to the dynamic nature, characterized by wave propagations, for example, variant selections of the transition product (Kalantar et al, 2005;Kanel et al, 2015;Wang et al, 2014;Wang et al, 2015).…”