Zhonghua Du

To study the effect of elongation ratio μ on the penetration depth of extendable long-rod projectiles (ELRPs), an ELRP was designed based on a conventional homogeneous long-rod projectile. First, finite element software LS-DYNA was employed to simulate the vertical penetration of both projectiles into armor steel targets, with simulation parameters and algorithms validated via experiments; subsequently, systematic numerical simulations analyzed the penetration performance of ELRPs (elongation ratio μ: 5.88–35.00%) under typical artillery velocities (1160–1600 m · s⁻¹) and clarified the mechanisms of penetration depth gain. Results show that under the same conditions, ELRPs outperform homogeneous rods in penetration capability, attributed to two factors: (1) the ELRP’s segmented rod-like penetration mode yields higher efficiency and cumulative damage; (2) the slender leading section of the rear core sharpens the head shape, reducing penetration resistance on the rear core’s main segment to improve performance. However, as the elongation ratio μ increases, the “target core effect” becomes more prominent, weakening the rear core’s penetration. Within the studied range, an optimal elongation ratio μ exists—at 29.00%, the maximum penetration depth gain reaches 18.00%—driven by the competition between the rear core’s penetration enhancement and the target core’s weakening effect.

Tether-nets in space applications are flexible capture systems for removing space debris. A new, low-mass, rectangular tether-net deployed by ten towing blocks is proposed in this paper for the purpose of capturing the main body of satellites. The dynamic model of a rectangular tether-net during the deployment process was established. The accuracy of the simulation model was validated by comparing it with on-ground experiments. In addition, the influence of towing block mass and launch speed on the maximum deployment area and the deployment lengths of the long side and short side of the rectangular tether-net were systematically analyzed. The results show that the tether-net configuration and launch distance of the simulations were consistent with those of the experiments, demonstrating the good accuracy of the simulation model. Moreover, with the increase in towing block mass, the maximum deployment area and deployment lengths of both sides of the rectangular tether-net showed a gradually increasing tendence, while the recoil impulse and structural weight increased. When the launch speed of the towing blocks increased, the maximum deployment area and deployment lengths increased significantly and further caused the extension of the shape-preserving distance.

This paper aims to study the penetration effect of harpoons on space debris to ensure the sustainable development of the space environment and solve the increasingly serious space debris problem. Firstly, a harpoon system was designed to capture space debris. Secondly, based on the Johnson–Cook dynamic constitutive model and fracture failure criterion, the finite element models of aluminum alloy plates were established. Then, the ballistic limit theory for the aluminum alloy target predicted the minimum launch velocity of the harpoon. Finally, the validation experiment was set up to verify the correctness of the model. The results show that the error between the simulation results of the speed for the harpoon embedded in the target and the theoretical results of the ballistic limit is 9.1%, which provides guidance for active space debris removal technology.

This paper presents the network-based modeling, validation and analysis of the nonlinear liquid spring damper model under vertical landing conditions of reusable launch vehicle. The impedance function of damper model is derived first. Then, its mechanical and hydraulic networks are newly established based on the hydro-mechanical analogy and network-based analysis. By comparing the networks between the corresponding symmetric and asymmetric structures, the meaning of each branch in the network is elucidated. After that, the validity of the network-based model for the liquid spring damper is confirmed by comparison against the experimentally verified nonlinear model in both frequency and time domain. The force and energy absorption characteristics of the damper model are further decomposed, and, specifically, the influence of the orifice area and orifice length on the attenuation performance is studied. The results show that the network-based model provides predictions consistent with those generated by the nonlinear model. The main discrepancy is attributed to the inaccuracy caused by the equivalent fluid bulk modulus. The network-based analysis indicates that the orifice area mainly influences the damping force in the network, which further affects the loads and efficiency of the damper. The orifice length mainly influences the inertia force in the network, which should be limited to a small value. The proposed novel interpretation of the damper models and responses under impact conditions constitutes a framework suitable for systematic design of typically highly nonlinear landing systems in reusable launch vehicles.

The liner is an important part of shaped charge. In this paper, the spherical cone composite structure liner composed of a spherical missing body and truncated cone (hereinafter referred to as the SCS liner) is studied. The SCS liner is made of copper. Based on this, a shaped charge structure based on the explosion pressure-coupling constraint principle is designed, filling an 8701 explosive (RDX-based explosive). Through pulse X-ray tests, numerical simulation, and static explosion tests, the significance of the detonation pressure-coupling constraint principle, as well as the forming law and penetration efficiency of the SCS liner are studied. The results show that in the pulsed X-ray test, a split jet with high velocity is formed in the SCS liner. The explosion pressure-coupling constraint principle delays the attenuation of the internal explosion pressure and improves the shape of jet. After the SCS liner is selected, the penetration depth is increased by 70.38%. The average head velocity of the explosive charge jet is 7594.81 m/s. The diameter of the hole formed by the jet of the explosive charge is 20.33 mm. The hole expands inside, and the perforation depth is 178.87 mm. The numerical simulation is in good agreement with the test.

Aiming at the parachute recovery of fixed-wing unmanned aerial vehicles, a method of parachute deployment by tractor rocket is proposed. First, the tensile tests were carried out on high-strength polyethylene and brocade silk-weaved composite materials. The dynamic property parameters of the materials were obtained, which was the input for the dynamic model of the parachute deployment phase. Second, the model was verified by the experiment results. Finally, parachute weight and rocket launch temperature during the deployment phase were studied. The results showed that the dynamic model has good accuracy; as the parachute weight increases, the maximum snatch force of the extraction line and the sling decreases as the force on the suspension lines increases and the deployment effect worsens. With the temperature rise, the maximum snatch force on the extraction line, sling, and suspension lines increases and the deployment length changes slightly.

In order to study the dynamic response associated with the impact of a kinetic projectile on the internal structure of an artificial satellite, we propose a kinetic projectile configuration with non-metallic material wrapping and multiple damage elements. The artificial satellite is simplified as a honeycomb sandwich panel and multi-layer plates. We carried out a ground damage test and finite element dynamic simulation, and we determined the lateral effect and penetration performance of the projectile. Then, we studied the dynamic behavior of the projectile penetrating the honeycomb sandwich panel using a theoretical model. We found that its ballistic limit velocity was 150 m/s, and the deformation of the opening had little relationship with the projectile velocity. Finally, we studied the dynamic response of the kinetic projectile impacting the multi-layer plates under various launch parameters. We found that the launch velocity required to meet the damage requirements was within 325 ± 25 m/s. Projectiles with a higher initial velocity had a stronger ability to penetrate the plates, but initial velocities higher than 325 m/s led to a reduced damage area. The kinetic projectile could adapt to incident angles less than 5° when damaging the plates. With the increasing incident angle, the penetration ability was reduced, and the damage area increased.

A tungsten fiber/Zr-based bulk metallic glass matrix composite (Wf/Zr-MG) is a potential penetrator material. To compare and analyze the penetration behavior of Wf/Zr-MG and a tungsten heavy alloy (WHA), a penetration experiment into the 30CrMnMo homogeneous armor target plate (RHA) is conducted in the present paper, by using a 37 mm smooth bore artillery with an impact velocity of 1550 ± 40 m/s. Unlike the penetrator made of WHA, the self-sharpening phenomenon was observed in the nose of the Wf/Zr-MG rod. The experimental results indicate that the penetration ability of Wf/Zr-MG rod is approximately 10% higher than that of the WHA rod when the impact velocity is 1550 ± 40 m/s. The combined findings on the microscopic morphology, composition, hardness distribution around the crater, and the macroscopic structure of the penetrator residual show that under this impact velocity, the Wf/Zr-MG material shows amorphous gasification. The Wfs outside the rod shows bending and backflow, resulting in the maintenance of the self-sharpening nose of the penetrator during the penetration process. Moreover, the hardness peak around the crater formed by the Wf/Zr-MG rod is lower, and the penetration crater is straighter, indicating that the Wf/Zr-MG rod has a stronger slag removal ability, lower penetration resistance, and higher penetration efficiency. It is an ideal penetrator material.

According to the dynamic characteristics of the adhesion desorption process between gecko-like polyurethane setae and the contact surface, the microcontact principle of an elastic sphere and plane is established based on the Johnson–Kendall–Robert model. On this basis, combined with the cantilever beam model, microscale adhesive contact models in the case of a single and an array of setae are obtained. The contact process is numerically simulated and verified by the adhesion desorption test. After that, the effects of external preload, the elastic modulus of setae material, the surface energy, and the surface roughness on the contact force and depth during the dynamic contact process of setae are studied. The results show that the error between the simulation and test is 15.9%, and the simulation model could reflect the real contact procedure. With the increase in preload, the push-off force of the setae array would grow and remain basically constant after reaching saturation. Increasing the elastic modulus of setae material would reduce the contact depth, but have little effect on the maximum push-off force; with the increase in the surface energy of the contact object, both the push-off force between the objects and the contact depth during desorption would increase. With the increase in wall roughness, the push-off force curve of the setae array becomes smoother, but the maximum push-off force would decrease. By exploring the dynamic mechanical characteristics of the micro angle of setae, the corresponding theoretical basis is provided for the numerical simulation of the adsorption force of macro materials.