Resumo em Inglês:

Abstract To study the dynamic response characteristics of the penetrating warhead under the impact load, experiments of projectile penetration into a concrete target were performed based on a 30-mm ballistic gun. Penetration resistance model of the projectile penetration into the concrete target was modified by considering the wake separation and cratering effects associated with oblique penetration. The projectile deformation process during penetration was analyzed by the modified penetration model and validated by experimental results. In particular, the deformation, stress, and strain distribution characteristics of the projectile and charge were analyzed. Results show that during oblique penetration of the target by the projectile, the nose of projectile endures substantial compressive forces due to the compression wave. This results in considerable deformation within a region spanning from 0.32 to 0.59 times the projectile’s length from the nose. Additionally, a coupling effect of compression and tension waves induces significant transverse deformation at the projectile’s tail, spanning from 0.88 to 1.0 times the projectile’s length from the tail end.

Resumo em Inglês:

Abstract This work presents stability analyzes results for a micro-launch vehicle (Micro-LV) considering the effects of sloshing. A conceptual Two-Stage to Orbit (TSTO) Micro-LV utilizing liquid propulsion with LOX and RP-1 is developed. Its mission objective is to deploy a payload of 100 kg into low Earth orbit (LEO) at an altitude of 300 km. Linearized equations of motion for rigid and flexible bodies, along with engine inertia effects and sloshing, are considered and arranged in a state-space formulation. Transfer functions relating the pitch angle ∅y and the engine gimbal angle, βEy are determined for open-loop stability analyses considering a proportional-derivative (PD) attitude controller. It is observed that at a FR of 90%, the RP-1 tank exhibits instability because its sloshing mass is situated between the center of percussion (CP) and the center of gravity (CG) of the Micro-LV, in the area referred as the danger zone. A solution for the passive mitigation of sloshing instability is implemented by introducing ring baffles with a minimum damping requirement of 0.15%, and its effect on the vehicle’s stability is analyzed.

Resumo em Inglês:

Abstract This study proposes a bio-inspired thin-walled energy-absorbing structure with self-similar configurations mimicking conch shells. Through quasi-static compression and drop hammer impact tests, the energy absorption characteristics were comparatively analyzed between the bio-inspired and conventional thin-walled tubes. The results demonstrate that under quasi-static compression, the bio-inspired tubes exhibit stable progressive buckling deformation, with a 21.39% increase in mean crush force (MCF) and a 12.95% improvement in crush force efficiency (CFE). During dynamic impact conditions, the bio-inspired structures show significantly reduced peak load while achieving enhanced specific energy absorption (SEA) and mean crush force (MCF), along with a 24.61% increase in crush force efficiency (CFE) and reduced undulation of load-carrying capacity (ULC). These findings offer novel perspectives for the development of innovative passive safety devices.