In this study, optimal design of a stuffed Whipple shield is proposed by using numerical simulations and new penetration criterion. The target model was selected based on the shield model used in the Columbus module of the international space station. Because experimental results can be obtained only in the low velocity region below 7 km/s, it is required to derive the Ballistic limit curve (BLC) in the high velocity region above 7 km/s by numerical simulation. AUTODYN-2D, the commercial hydro-code package, was used to simulate the nonlinear transient analysis for the hypervelocity impact. The Smoothed particle hydrodynamics (SPH) method was applied to projectile and bumper modeling to represent the debris cloud generated after the impact. Numerical simulation model and selected material properties were validated through a quantitative comparison between numerical and experimental results. A new criterion to determine whether the penetration occurs or not is proposed from kinetic energy analysis by numerical simulation in the velocity region over 7 km/s. The parameter optimization process was performed to improve the protection ability at a specific condition through the Design of experiment (DOE) method and the Response surface methodology (RSM). The performance of the proposed optimal design was numerically verified.
A unified shock physics code, ExLO, in which Lagrangian, ALE and Eulerian solvers are incorporated into a single framework, has recently been developed in Korea. It is based on the three-dimensional explicit finite element method and written in C++. ExLO is mainly designed for the calculation of structural responses to highly transient loading conditions, such as high-speed impacts, high-speed machining and explosions. In this paper the numerical schemes are described. Some improvements of the material interface and advection scheme are included. Details and issues of the momentum advection scheme are provided. Numerical predictions are in good agreement with the existing experimental data. Specific applications of the code are discussed in a separate paper in this journal. Eventually, ExLO will provide an optimum simulation environment to engineering problems including the fluid-structure interaction problems, since it allows regions of a problem to be modeled with Lagrangian, ALE or Eulerian schemes in a single framework.
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