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The Pre-Blast Concept for use on Armour Materials
Defence Science and Technology Group Fishermans Bend Victoria Australia
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It can sometimes be difficult to determine whether vehicles damaged by blast loading are repairable in theatre or so significantly damaged that the hulls must be scrapped. The primary purpose of this investigation is to provide basic metallurgical data to assist in determining the criteria of failure. On top of this, it may be possible that blast loading may actually improve the performance of vehicles by work hardening of the hull and it might be possible to use controlled blasting as a technique to improve blast resistance Repeated blast test results up to 7 times of candidate armour materials showed that the greatest deformation occurred during the first blast and subsequent blasts showed less evidence of deformation. This demonstrates that the steel experienced a significant increase of work hardening after the first blast, at which stage the steels reached a saturated level. Despite repeated blasting, there was little evidence of cracking in the armour steels. Crack-starter explosion bulge testing of the armour steels at -18 degrees celsius demonstrated that the steels have adequate toughness in the as-welded condition. This suggests that blasting is not detrimental to the subsequent blastperformance of armour.The work also suggests that appropriate blasting may have a work hardening effect that may be used to increase blast resistance of steels. To test this, the pre-blast concept test program includes hardening of materials by sheet charge blast loading and subsequent testing of steels by multiple explosion bulge testing. Steels investigated include TWIP steels, a wear plate and armour steels with hardness 450 HV or higher up to 650 HV. In general, the improvement in deformation resistance is associated with increases in hardness combined with reductions in microstructural grain size. In practical terms, this work demonstrates that vehicles subjected to blast damage in theatre should not be condemned on the sole
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