Performance of aluminium alloys in naval maritime platforms under high-strain rate military loading
W. Reid1, V Pickerd1, L. Davidson1, G. Yiannakopoulos1,E. Frain1 and C. Flockhart1
1Defence Science and Technology Organisation, Fishermans Bend, 3027, Australia;
e:
The requirement for use of aluminium alloys in naval maritime platforms is growing due to the relative cost of material and the advantages aluminium offers in mass reduction. However, use in naval platforms does introduce design considerations which must be addressed such as structural integrity due to environmental conditions, and material and structural response to high-strain rate military loading. This paper discusses some of these considerations and the research that is currently being performed within the Defence Science & Technology Organisation on the material properties of aluminium and the effect on platform vulnerability from above and below water weapon detonations.
In both above and below water weapon attack, damage typically occurs in the form of large plastic deformations or localised high-strain to failure. The presence of non-homogeneous discontinuities such as welds and the associated heat affected zone can greatly influence the structural behaviour. Current and planned work programs in these areas will be discussed with regard to characterising the effect of the non-homogeneous structure on overall performance.
Accounting for the response of welded aluminium structures to high-strain rate loading events requires understanding of the differences in properties between the weld metal, the weld heat affected zone and the base metal. The limited availability of high-strain rate material data for aluminium alloys and for the material in a heat affected state makes this difficult. Part of this work program involves obtaining high-strain rate materials data for parent plate, heat affected plate and weld material of aluminium alloy for naval applications.
The material data obtained from experimental programs can then be used in modelling and simulation to identify and solve the high-strain rate phenomena identified in various experimental programs. Current DSTO modelling has involved small scale explosive experiments on 6061T6 aluminium and has included shock loading and bubble collapse on plates which results in fracture. This work highlights the sensitivity of material properties to the fluid-structure interaction, specifically the properties of welds and the heat affected zones.