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This paper presents the computational-based ballistic limit of laminated metal panels comprised of high strength steel and aluminium alloy Al7075-T6 plate at different thickness combinations to necessitate the weight reduction of existing armour steel plate. The numerical models of monolithic configuration, double-layered configuration and triple-layered configuration were developed using a commercial explicit finite element code and were impacted by 7.62 mm armour piercing projectile at velocity range of 900 to 950 m/s. The ballistic performance of each configuration plate in terms of ballistic limit velocity, penetration process and permanent deformation was quantified and considered. It was found that the monolithic panel of high-strength steel has the best ballistic performance among all panels, yet it has not caused any weight reduction in existing armour plate. As the weight reduction was increased from 20-30%, the double-layered configuration panels became less resistance to ballistic impact where only at 20% and 23.2% of weight reduction panel could stop the 950m/s projectile. The triple-layered configuration panels with similar areal density performed much better where all panels subjected to 20-30% weight reductions successfully stopped the 950 m/s projectile. Thus, triple-layered configurations are interesting option in designing a protective structure without sacrificing the performance in achieving weight reduction. Keywords Ballistic impact; ballistic limit; double-layered plate; numerical simulation; triple-layered plate N.A. Rahman et al. / Ballistic Limit of High-Strength Steel and Al7075-T6 Multi-Layered Plates Under 7.62-mm Armour Piercing…

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A B S T R A C T Load-controlled fatigue tests were performed at 20 and 50 • C using two relative humidity levels of 55 and 80% to characterize the influence of humidity and temperature on the fatigue behaviour of an extruded AZ61 magnesium alloy. Fatigue tests were also conducted at 150 • C. No significant variation in fatigue properties was noticed with respect to temperature over the range from 20 to 50 • C for both the humidity levels. Fatigue limits in the range 140-150 MPa were observed for relative humidity of 55%. Fatigue strength decreased significantly with increase in temperature to 150 • C. Further, a significant reduction in fatigue strength with a fatigue limit of ∼110 MPa was observed with increase in relative humidity to 80% at 20 and 50 • C. The crack initiation and propagation remained transgranular under all test conditions. The fatigue fracture at low stress amplitudes and high relative humidity of 80% results from the formation of corrosion pits at the surface and their growth to a critical size for fatigue-crack initiation and propagation. The observed reduction in fatigue strength at high humidity is ascribed to the effects associated with fatigue-environment interaction.

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