Lateral stress measurements in a shock loaded alumina: Shear strength and delayed failure

Manganin gauges have been embedded in AD975 alumina in such orientation tha t renders them sensitive to the lateral component of stress during shock lo ading. A secondary increase in lateral stress, which indicates a decrease i n overall shear strength has been observed. It has generally been assumed t hat such features are damage fronts. Gauges placed at increasing distances from the impact face show that the damage front penetrates less than 5 mm. It is believed that interactions with grain boundaries impede the fronts pr ogress. With increasing impact stress, results show that the velocity of th e damage front increases until failure occurs in the main shock itself. Suc h behaviour has been observed in other brittle materials such as silicon ca rbide and glasses. (C) 2001 Kluwer Academic Publishers.