Search Results (3)

Our investigation delves into the scaling law governing planetary cratering impacts. We meticulously analyze the interplay between dimensionless parameters driving crater growth and the morphological transition of craters and construct the scaling analysis between the scale model tests and the prototype tests by numerical simulation. With practical engineering applications in mind, we design scale model tests based on the experimental setups of geotechnical centrifuges, ensuring the robust validity of test designs. This meticulous approach is integral to achieving fidelity between simulations and experimental scenarios. Validation of our scale model tests is conducted through a numerical modeling framework, coupling the finite element-smoothed particle hydrodynamics adaptive method (FE-SPH). This validation procedure serves to bolster the reliability and credibility of our methodology, facilitating an accurate depiction of the cratering mechanism. Of particular interest is the investigation into the depth-to-diameter ratio of impact craters, wherein we explore its intricate relationship with projectile diameter and gravity. Through rigorous analysis, we delineate the transition diameter at which terrestrial impact craters manifest a transition from simple to complex morphologies, thereby shedding light on the underlying dynamics of crater formation. Moreover, our study meticulously scrutinizes the relationship of crater formation time between the scaling model tests and the prototype tests. Our research underscores the consistency of the crater depth–diameter ratio in the scale model tests and the prototype tests and affirms applicability in replicating prototype tests by scale model tests. Notably, our findings reveal compelling correlations between the depth-to-diameter ratio of impact craters and gravity, as well as projectile diameter, providing valuable insights into the governing dynamics of impact crater formation. These insights not only advance our fundamental understanding of planetary cratering processes but also hold implications for practical applications in planetary science and engineering. Full article

The penetration of projectiles into targets has a broad background in engineering. In this work, numerical simulations of the projectile-target penetration problem are conducted using the Finite Element Method (FEM), the Smoothed Particle Hydrodynamics (SPH) and the Finite Element–Smoothed Particle Hydrodynamics Adaptive Coupling Method (FE-SPH ACM) based on the LS-DYNA software package. First, the penetration experiments using aluminum targets and ceramic targets are simulated. The experimental and simulation results show that the FE-SPH ACM has the better accuracy in calculating the debris cloud head velocity and interface velocity, with an error of no more than 4%. Furthermore, we use the FE-SPH ACM to investigate the anti-penetration performance of aluminum/ceramic composite targets in different combinations. We find that the reasonable layout can improve the protective performance of multi-layered target, especially composite target plates with ceramic as the front layer. In addition, the ballistic limit velocities for ceramic-aluminum ratios of 3/7, 5/5 and 7/3 are approximately 1300 m/s, 1400 m/s and 1500 m/s, respectively. Obviously, increasing the proportion of ceramic materials can enhance the anti-penetration performance. Full article

An asteroid impact can potentially destroy life on this planet. Therefore, asteroids should be prevented from impacting the Earth to impede severe disasters. Nuclear explosions are currently the only option to prevent an incoming asteroid impact when the asteroid is large or the warning time is short. However, asteroids exist in an absolute vacuum, where the explosion energy propagation mechanism differs from that in an air environment. It is difficult to describe this process using standard numerical simulation methods. In this study, we used the single-material arbitrary Lagrangian–Eulerian (ALE) method and the finite element-smoothed particle hydrodynamics (FE-SPH) adaptive method to simulate the process of deflecting hazardous asteroids using penetrating explosions. The single-material ALE method can demonstrate the expansion process of explosion products and energy coupling in absolute vacuum. The FE-SPH adaptive method can transform failed elements into SPH particles during the simulation, avoiding system mass loss, energy loss, and element distortion. We analyzed the shock initiation and explosion damage process and obtained an effective simulation of the damage evolution, stress propagation, and fragment distribution of the asteroid. In addition, we decoupled the penetrating explosion into two processes: kinetic impact and static explosion at the impact crater. The corresponding asteroid damage modes, velocity changes, and fragmentation degrees were simulated and compared. Finally, the high efficiency of the nuclear explosion was confirmed by comparing the contribution rates of the kinetic impact and nuclear explosion in the penetrating explosion scheme. Full article