Yield stress, polymorphic transformation, and spall fracture of shock-loaded iron in various structural states and at various temperatures Academic Article uri icon

abstract

  • The response of polycrystalline 99.5% pure iron was studied in a series of planar impact experiments, with samples of different thickness having an initial temperature that ranged between 300 and 1233 K. The free surface velocity histories of the shocked samples were recorded in the course of the experiments. Almost all recorded histories are characterized by a three-wave structure containing an elastic precursor Pel and two plastic, P1 and P2, waves. It was found that at 300, 900, and 1039 K (some 5 K away from iron's Curie point), the decay of the Pel wave with propagation distance is characterized by two different regimes; a fast one that corresponds to plastic strain rates above ∼105 s−1 and a slower one at lower strain rates. Since the shear stress at which the change-over takes place is very close to the Peierls stress of iron, we assume that above this stress the decay is governed by the phonon-damped over-barrier dislocation motion, while below it, the thermally activated generation and motion of ...

publication date

  • January 1, 2015