Deformation and fracture of aluminum-lithium alloy V-1461 under quasistatic and local dynamic loading

Third generation of low-density aluminium-lithium alloys includes 1424 (2.54 g/sm3) and V-1461 (2.63 g/sm3) alloys. Their fracture toughness and crack growth resistance are higher than for the previously developed alloys 1420 and 1460. Despite of the good prospects of using of these materials in aeronautical and space applications there are no any data about their behaviour under dynamic loading. In this work, mechanical behaviour of specimens made of rolled V-1461 aluminium-lithium alloy plates with thickness 1.9 mm under static, dynamic and impact loading conditions was studied. Static strength tests were performed to obtain mechanical properties and stress-strain curves at low strain rates. It is found that tensile strength and yield stress in rolling direction are higher by 8-10 % than the properties in the perpendicular direction. Dynamic tensile tests were carried out with a CEAST 9350 Drop Tower system and special build-in-home equipment. The results of dynamic tests show that scaling static stress curve with sufficient accuracy describes the material behaviour under dynamic loading. When the strain rate of 200 s-1 material strength properties increased by ~ 20%. Through-thickness material anisotropy that lead to spall formation on backside of the plate was observed during ballistic tests. Finite element model based on bilinear kinematic hardening approximation of scaling stress-strain curve was developed. Results of numerical modeling are in a good agreement with experiments (ballistic limit and full ballistic curve) in case of normal impact. This confirmed the limited strengthening ability of V-1461 alloy at high strain rates.