Friction on Crack Surfaces During Compression of Explosives - A Source of Hot Spots and Probable Ignition Sites

摘要

The mechanical properties of composite plastic bonded explosives were investigated as a function of confining pressure. The results indicate different failure processes in two pressure ranges, a low pressure range between about 0.1 to 7.0 MPa, which is considered in this paper and a higher pressure range. In the low pressure range, crack processes are important in failure. The pressure dependence of the compressive strength in the low pressure range is attributed to coulomb friction between surfaces of closed shear cracks and from the observed linear increase of the strength with pressure and the angle of the fracture plane a friction coefficient is obtained. A friction coefficient can also be obtained from the ratio of the compressive to tensile strength and directly form the above angle. The friction coefficient obtained from these three separate observations is in agreement and this is taken as strong evidence for the importance of this friction in determining strength and mechanical failure. Frictional heating during deformation can then cause hot spots leading to ignition.