Abstract
The design of armored vehicles requires reliable constitutive models that are valid over a wide range of strain rates and temperatures. A comprehensive experimental program is executed to characterize the stress-strain response of high strength aluminum 7020-T6 at temperatures ranging from 20°C to 320°C. It includes tensile experiments on uniaxial, notched, central hole and shear specimens. Aside from low and intermediate strain rate experiments, high strain rate experiments are performed on a Split Hopkinson Pressure Bar (SHPB) system equipped with a load inversion device. Furthermore, hemispherical punch and V-bending experiments are performed to achieve equi-biaxial tension and transverse plane strain conditions. It is found that a Yld2000–3d plasticity model with isotropic strain hardening and thermal softening is suitable to describe the large deformation response, while a rate- and temperature-independent Hosford-Coulomb model is used to predict fracture. Impact experiments are performed on 4 mm thick targets with blunt, hemispherical and conical steel projectiles of 8 mm diameter and a mass of 13.8 g. The impact velocity is varied such that the full spectrum from the ballistic limit to complete penetration can be characterized. In addition, perpendicular and oblique configurations are considered. Numerical simulations are performed for all experiments confirming the validity of the identified constitutive model and providing unmatched insight into the dynamic penetration failure mechanism.
Highlights
Aluminum alloys are often applied in aircraft, aeronautical and automotive components because of their high specific strength
Aside from low and intermediate strain rate experiments, high strain rate experiments are performed on a Split Hopkinson Pressure Bar (SHPB) system equipped with a load inversion device
The effect of the strain rate is considered as a second-order effect within the range of temperatures of interest here
Summary
Aluminum alloys are often applied in aircraft, aeronautical and automotive components because of their high specific strength. Gupta et al (2007) analyzed the impact response of 1100-H12 aluminum alloy plates at a thickness less than 3 mm for three types of rigid strikers at velocities below 200 m/s They observed that the blunt nosed projectiles shear out a circular plug of diameter equal to that of the projectile. Gürgen (2019) used a numerical model to simulate oblique impacts on 1.5 mm thick 7075-T6 aluminum plates and 20 mm thick AA5083H116 plates with an ogive-nose steel projectile. They observe that with increasing angle of the plates, the deformation mode changes to tearing as preloading conditions cause an initiation of cracks around the perforation hole. After demonstrating the validity of the corresponding finite element simulations for all impact loading scenarios, the penetration and perforation mechanisms are analyzed in detail
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