ABSTRACT
When an e x p l o s i v e detonates i n d i r e c t c o n tact with an ob j e c t , t h i s i s subje c t e d to a shock wave. The pr e s s u r e a t the e x p l o s i v e / m a t e r i a l i n t e r f a c e i s equal to the detonation p r e s s u r e ( i n s o l i d and l i q u i d e x p l o s i v e s up t o 40 GPa). No m a t e r i a l known a t present can stand up to such high p r e s s u r e s without undergoing yield/deformation. The e f f e c t of the shock wave induced i n the m a t e r i a l i s prolonged i f the charge i s covered by a m a t e r i a l of s u f f i c i e n t mass, e.g. sand or c l a y . The e f f e c t on a s t r u c t u r a l m a t e r i a l i s determined by the detonation p r e s s u r e of the ex p l o s i v e and the contact area of the charge. When a charge i s detonated on a s t r u c t u r e of moderate t h i c k n e s s which i s exposed to the a i r on both s i d e s , an e f f e c t , s p a l l i n g of m a t e r i a l , i s obtained on the opposite s i d e a l s o , see F i g . 3. T h i s i s due to p a r t i a l r e f l e c t i o n of the shock wave as i t passes from the medium of higher d e n s i t y to the one of lower d e n s i t y . T h i s g i v e s r i s e , i n t e r a l i a , to t e n s i l e s t r e s s e s which cause s p a l l i n g of the m a t e r i a l i f they exceed the u l t i m a t e t e n s i l e s t r e n g t h .
