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1

Reverse ballistic impact studies of thin plate perforation

Forde L. C., Proud W. G., Walley S. M., Church P. D., Cornish R.

Engineering Transactions

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2011

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Vol. 59, iss. 3

161-196

EN

Full-scale ballistic experiments using tungsten rods and rolled homogeneous armour (RHA) steel plates are expensive to perform. For this reason, a study has been performed into the possibility of using less expensive, more easily available metals in small-scale laboratory experiments. The metal pairs chosen listed in order as armour/penetrator materials were: RHA steel/tungsten, dural/mild steel, and copper/aluminium. In order to be able to use as many diagnostics as possible (including high speed photography, VISAR, stress gauges) the reverse ballistic configuration was used. This configuration also allowed the determination of the high rate, low strain mechanical properties of mild steel to be determined. Finally, a comparison was made between experiment and numerical predictions made using a modified Armstrong-Zerilli constitutive model for the RHA steel/tungsten pair. The model was found to underpredict the penetration, probably because failure mechanisms were not incor- porated.

2

Recent trends in research on energetic materials at Cambridge

Proud W. G., Walley S. M., Williamson D. M., Collins A. L., Addiss J. W.

Central European Journal of Energetic Materials

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2009

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Vol. 6, nr 1

67-102

EN

Recent work in our laboratory has established a time-temperature superposition law for a PBX. This was achieved by performing uniaxial compression testing over a wide range of strain rates and temperatures along with Differential Thermal Mechanical Analysis (DMTA). The classic WLF (Williams, Landel, Ferry) transform was found not to fit the shift factor needed to align the data whereas a simple log-linear fit did. The thermal properties (diffusivity, conductivity, heat capacity) of a PBX have been measured three different ways and found to agree (within experimental error) with the classic equation relating these three parameters. This gives us confidence that, for example, hot-spot ignition mechanisms of this class of energetic materials can be accurately modelled using their measured thermal properties. A modular instrumented testing facility has been designed and built to simulate and control the conditions experienced by novel heavy-metal-free (green) primers contained within ammunition. Physical data obtained from the facility, when compared with data from live fire tests, will give a greater understanding of which characteristics are important to functionality. As explosives are granular materials, the techniques developed for studying such materials are being applied to determine the effect of particle size distribution and shape on sensitivity.

3

The Relationship between Shock Sensitivity and Morphology in Granular RDX

Czerski H., Proud W. G., Field J. E.

Central European Journal of Energetic Materials

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2006

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Vol. 3, nr 3

3-13

EN

It is known that batches of the secondary explosive RDX from different manufacturers show significant variation in their shock sensitivity. No obvious correlation between shock sensitivity and either chemical composition or morphology has previous been identified which explains this. We use a range of techniques to study the microstructure of RDX crystals and the bulk morphology of granular beds in order to assess which hotspot mechanisms tend to be dominant. Crystals were characterized using mercury porosimetry, environmental scanning electron microscopy (ESEM) and optical microscopy. This range of methods yields quantitative and qualitative data on internal void size and number and surface structure. Shock sensitivity is quantified using small-scale gap tests, and this demonstrates the clear differences in sensitivity between batches from different manufacturers. The samples used are from three manufacturers, produced by both the Woolwich and Bachmann processes, and all have an average particle size of approximately 1200 μRDXm.

4

Shock and deformation properties of geological and construction materials

Tsembelis K., Grantham S. S., Proud W. G., Field J. E.

Biuletyn Wojskowej Akademii Technicznej

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2002

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Vol. 51, nr 12

87-99

EN

Geological and construction materials present particular problems for modelling. Generally, a two or more component mixture is further complicated by a particle size distribution in at last one of the phases. Rock and concretes are widely encountered throughout the environment and are used as commercial building materials. This paper presents techniques and results from plate impact experiments and ballistic trials where such materials are subjected to shock and ballistic loading.

PL

Modelowanie materiałów geologicznych i konstrukcyjnych związane jest z pokonaniem szczególnych problemów. Ogólnie biorąc, mieszanina dwóch lub więcej składników jest jeszcze bardziej złożonym układem ze wzgledu na rozkład rozmiarów cząstek w przynajmniej jednej z faz. Skały i betony są powszechnie spotykane w środowisku i stosowane jako handlowe materiały budowlane. W niniejszym artykule są przedstawione techniki i wyniki prób balistycznych oraz uderzenia płytą, stosowanych do badania wpływu obciążenia balistycznego i udarowego na materiały tego rodzaju.