ABSTRACT
Ammunition components and armours are obviously expected to function at high rates of strain. Interestingly, the elastic stiffness (Young’s modulus E) is insensitive to strain rate for metals, whereas it can vary quite considerably with strain rate for many non-metals. A low static yield strength alloy (alloy 3) will have a high dynamic yield strength, if it has a high strain rate sensitivity index. The strain rate at the tool tip during machining is very high; the railway line deforms fast under the train wheels; in vehicle crashworthiness testing the structure crumples at high speed; engine and drivetrain components work at high strain rate; the list could go on. At high strain rates the dislocations have less time to move, and so ductility is curtailed giving premature fracture. The whole field of dynamic properties and behaviour of alloys at high strain rate is an important and fascinating one, and there is much to learn yet.
