Dynamic FEM and DEM simulations are carried out to investigate dynamic penetration of a projectile into a target of granular medium. Spatial distribution and time dependence of ejecta are clarified together with their trajectories in medium. Highly densified region is generated just ahead of the projectile and propagates leaving rarefied regions. Force on the projectile is fully discussed in connection with dynamic behavior of granular target.
Abstract. In the present study, the three-dimensional elastic discrete element method (DEM) and the elastic finite element method (FEM) analysis were, respectively, applied to the randomly distributed identical spheres as a granular target and to the cylindrical projectiles in order to clarify dynamic response during penetration. In the target, it was found that highly densified region was formed just ahead of the projectile and began to propagate spherically at much higher velocity than that of projectile leaving relatively rarefied region. It was also found that the peak resistance during penetration was closely related to the initial formation of densified region and was expressed in terms of momentum change of target particles accelerated by the projectile. Stress wave propagation in the projectiles with various body lengths was investigated during penetration and was discussed in connection with dynamic response of target particles ahead of the projectile. Effect of mechanical properties of projectile on the peak resistance was also investigated and was understood in connection with dynamic behavior of target particles.
We created a visualization tool called Irregular Trend Finder (ITF) for the VAST Challenge 2012 Mini Challenge 1. ITF is an interactive tool designed for analyzing large amounts of data with timestamp and hierarchy structure in mind, so that a user can see the overview first, and then obtain more detailed information. We discovered the answers for the Challenge, and confirmed that overview first and then looking in detail is an efficient method to seek particular information in case of large amounts of data.
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