![image](freesurfacevelocities.pdf){width="1.6\columnwidth"}

The measured spall strength for the plate-impact experiments is plotted as a function of strain rate ($\dot{\epsilon}$) in Fig. \[fig:spallvsstrainrate\] for the three types of PDMS oils. Also included in Fig. \[fig:spallvsstrainrate\] are curves based on homogeneous and heterogeneous nucleation models described in Section \[theory\]. The experimental data does not show a strain rate dependency for either of the three silicone oils. The measured spall strength is also plotted as a function of the shock pressure ($P_\mathrm{h}$) in Fig. \[fig:spallvspressure\]. As can be seen, the measured spall strength is unaffected by the wide variation in shock pressure. In Fig. \[fig:spallvsviscosity\], the measured spall strength is plotted as a function of the zero-shear-rate viscosity for the three PDMS oils. Curves based on homogeneous and heterogeneous cavitation models described in Section \[theory\] are also shown, as well as the data and correlations between critical tension and viscosity obtained from bullet-piston experiments of Bull [@Bull1956] and Couzens and Trevena. [@Couzens1974] A second set of power-law correlations based on the results of Bull [@Bull1956] and Couzens and Trevena [@Couzens1974] ($P_\mathrm{s}\sim \eta^{0.2}$ and $P_\mathrm{s}\sim \eta^{0.06}$, respectively) are also plotted such that they intercept the average spall strength value of at , which corresponds to 