Stress relaxation and precursor decay in laser shock-loaded iron

Iron samples of different thicknesses have been submitted to laser shocks of short duration. Transmitted wave measurements have been performed by means of polymeric piezoelectric transducers. The records indicate a decrease of the elastic precursor amplitude with increasing propagation distance, as well as a stress relaxation behind the elastic wave front. These features were already observed in shock-loaded iron, but this paper extends the experimental data to a previously unexplored range of thin targets and high strain rates. Postshock examinations of the recovered specimens reveal significant twin formation. Computer simulations of the experiments have been made using a constitutive model from the literature, including a theoretical description of rate-dependent twinning. The ability of that model to predict the experimental results has been tested. A correct overall agreement has been obtained, except for some discrepancies which have been discussed.