a spalling material is typically characterized by the damage rate ($\dot{V}_\mathrm{v}$), which is a measure of the time rate of change of the specific volume of voids in the target material. For plate-impact experiments, it has been shown that the damage rate must exceed the strain rate by a factor of four or greater ($\dot{V}_\mathrm{v}>4\dot{\epsilon}/\rho_0$) in order to relieve tension in the sample and form the spall pulse on the free-surface velocity signal. [@Antoun2003] The spall strength of a liquid may therefore be affected by its physical properties, the distribution of pre-existing flaws, and the rate of loading. This section will present models which can be used to predict the spall strength and its dependence on strain rate and viscosity for both homogeneous and heterogeneous cavitation nucleation.

Homogeneous nucleation {#homogeneous}
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In a homogenous nucleation process, random molecular fluctuations allow bubbles to overcome the energy barrier created by surface tension in order to reach the critical radius and continue to grow. According to the theory of nucleation, the rate at which bubbles of a critical radius form is proportional to $\mathrm{exp}(-W_\mathrm{max}/kT)$, where $k$ is the Boltzmann constant, and $T$ is the temperature. [@Fisher1948; @Zeldovich1992; @Carlson1975] The work of formation needed 