THE SPALL STRENGTH OF ALUMINA CERAMICS

The response to plate impact loading of three aluminas with varying gl ass content and porosity has been investigated. Spall strengths have b een shown to be dependent on the amplitude and duration of the compres sion pulse which precedes the tensile loading, but insensitive to the rate of release. Some tensile strength is measured in impacts where th e Hugoniot elastic limit has been exceeded. The effect of the material microstructure on the dynamic tensile strength has also been studied. Low porosity aluminas with many microstructural irregularities were f ound to possess the lowest spall strengths. Experimental values compar e well with those predicted by an energy balance theory developed by G rady [J. Mech. Phys. Solids 36, 353 (1988)]. (C) 1998 American Institu te of Physics. [S0021-8979(98)06914-X]