On the Failure and Dynamic Performance of Materials

Abstract

Waves induced by impact initiate deformation mechanisms within a material that precede later flow. An impulse excites a cascade of deformation mechanisms starting with ultrafast and concluding with slower ones. In metals, brittle glasses and polycrystalline ceramics there are a combination of mechanisms with differing relaxation times that condition a loaded target. In the case of ballistic impact, once failure has occurred, long rod penetration can occur and the depth achieved within each target can be scaled with the deformation strengths recorded during the initial high pressure impulse. A review of material shock response and target preconditioning shows a correlation with the ballistic penetration of the target after loading. This indicates that the effect of an initial loading impulse upon material behaviour is a strong feature of the effects observed in many dynamic phenomena.

A pulse-shaping technique to investigate the behaviour of brittle materials subjected to plate-impact tests

“…On the other hand, piezoresistive gauges, which are based on the change of electrical resistivity with pressure in piezoresistor materials such as manganin coils (cf. [17]), are used to record the stress level in the sample material [18]. This technique has been used to measure the change of longitudinal stress σ x and lateral stress σ y as functions of time.…”