Shear strength of shock‐loaded alumina as determined with longitudinal and transverse manganin gauges

The shear strength of shock‐loaded commercial alumina (AD‐85 manufactured by Coors) is determined in the 0–140‐kbar range of shock stresses. Longitudinal and transverse manganin gauges were used to determine the principal stresses in the shocked specimens. Shear strengths were determined from the difference between the longitudinal and lateral stresses. It was found that the shear strength remains essentially constant at about 27 kbar for shock stresses between 60 kbar (the Hugoniot elastic limit) and the maximum shock amplitude tested in this series (142 kbar). The source for the high shear strength is attributed to the confining pressures that strengthen the comminuted ceramic. Evidence for this interpretation is obtained by considering the release profiles as recorded by the longitudinal gauges when the free‐surface rarefactions reach gauge location.