Stress dependence of elastic-wave attenuation in LiF

Shock-wave propagation studies along the 〈100〉 direction in LiF single crystals are presented for three elastic impact stresses, namely, 39, 29, and 15 kbar. Present results demonstrate a stress threshold for a large increase in plastic strain rate and establish stress relaxation as a bulk property. Analysis of the data reveals a one-to-one correspondence between plastic strain rate and stress at the elastic-shock front. This is in agreement with the constitutive relation generally used for stress-relaxing solids under plate-impact loading.