the viscosity of the 10 St oil. As can be seen, the measured spall strength in this work showed no clear correlation with the viscosity of the oils. The average spall strength was 22.7 MPa for the 0.5 St silicone oil, 22.6 MPa for the 10 St oil, and 22.8 MPa for the 300 St oil.

![Spall strength as a function of strain rate for the plate-impact experiments. Also shown is the expected sensitivity of spall strength to strain rate based on homogeneous and heterogeneous cavitation models.[]{data-label="fig:spallvsstrainrate"}](spallvsstrainrate.pdf){width="0.9\columnwidth"}

![Spall strength as a function of shock pressure for the plate-impact experiments.[]{data-label="fig:spallvspressure"}](spallvspressure.pdf){width="0.9\columnwidth"}

![Measured spall strength from the plate-impact experiments as a function of the zero-shear-rate viscosity ($\eta_0$) of the PDMS oils. Also shown is the expected sensitivity of spall strength to viscosity based on homogeneous and heterogeneous cavitation models, and previously published data and viscosity correlations from Bull [@Bull1956] and Couzens and Trevena. [@Couzens1974][]{data-label="fig:spallvsviscosity"}](spallvsviscosity.pdf){width="0.9\columnwidth"}

CAVITATION MODELS {#theory}
=================

The spall strength obtained from plate-impact experiments on liquid targets is a measure of the critical tension required to induce cavitation bubble growth. A liquid in tension is in a metastable state, where bubble nucleation and growth, the mechanism by which tension is relieved, is 