  In this work, the spallation processes in the ductile metals are
systematically discussed in theory. By employing the phase transition theory
and non-equilibrium transport theory, the spallation processes of ductile
metals under dynamic loading may be mainly determined by the diffusion and
agglomeration of generated vacancies. And through the theoretical analysis on
the dynamic spallation processes, it is found that (1)the spallation critical
behaviors exist; (2)both the damage evolution rate and the void growth velocity
in the spallation planes are monitored by the grain sizes, the tensile strain
rate and the temperature of the metal after shocking, i.e., a larger grain size
and tensile strain rate and higher temperature will cause a larger damage
evolution rate and void growth velocity; (3)there exists the characteristic
size for the voids and the characteristic stress on the void boundary, which
are dependent of vacancy excitation energy and the average volume occupied by
the metal atom; (4)both the stress and temperature close to the void are high
and may cause the melting, and they decrease quickly as the distance away from
the void increases; (5)the plastic zone surrounding the formed voids is
obtained and found to be governed by the characteristic stress; (6)the void
growth in the spallation processes may arise from the agglomeration of
vacancies rather than the emitting of dislocations. Most of the theoretical
results are novel and obtained first. And they are found to be in agreement
with the experimental results and the simulated results.
