Various civil structures are susceptible to failures due to penetration problems. This is due to the lack of fast and effective techniques to simulate the penetration problems during structural design phases. This has recently attracted significant attention of researchers and scientists.
Presently, experimental, theoretical and numerical methods are used in the analysis of the penetration problems. On the other hand, several empirical models have been developed to perform penetration tests in different construction materials such as concrete. Unfortunately, these models are difficult to use, expensive and unsuitable for two-dimensional and three-dimensional oblique penetration tests. To this end, alternatives methods favorable for complex penetration problems are highly needed and the numerical investigation has been identified as a promising solution with the potential to overcome the drawbacks of scaled tests and theoretical methods.
Recently, Dr. Xuguang Chen, Dr. Fangyun Lu and Dr. Duo Zhang at the National University of Defense Technology investigated the three-dimensional penetration problem. They aimed at overcoming the initially experienced challenges in accurately and effectively predicting the three-dimensional trajectories. Their research work is currently published in the research journal, International Journal of Impact Engineering.
Briefly, the authors commenced their experimental works by performing different scaled penetration experiments with ogive-nosed method in which steel projectiles penetrating into the concrete cylindrical targets were utilized. All the projectiles were launched at a certain angle and a suitable velocity in the range of 800m to 900m/s. Furthermore, a fast camera system was used to measure and record the three-dimensional flight attitudes of the projectiles. Eventually, LSDYNA3D software in conjunction with a PENE3D simulation code were used to simulate the penetration tests and validate the model functionality.
From the experimental results, the authors observed that fragments were easily ejected from the material thus resulting in the formation of the crater at the surface of the concrete target. This was attributed to the sparse waves emanating from the front and back surfaces of the target. On the other hand, it was noted that large oblique angles and yaw negatively affected the penetration but was ideal for protecting the target. This was as a result of the formation of the embedment and ricochet due to the loaded joints. Furthermore, deformations were observed in all the projectiles during penetrations in the scaled tests. This was highly contributed by the ductility property of the projectiles. Therefore, the projectiles underwent mass loss with a ratio ranging from 3.4 to 6.7%. Besides, the mass loss linearly related to the striking velocity.
According to the authors, LS-DYNA was not efficient for three-dimensional deep penetration simulations. However, PENE3D was suitable for predicting the deep/oblique/multi-layer penetration trajectories. The simulation time for each simulation case is as short as several seconds for a common personal computer. Besides, it is less costly and consumes less time thus preferred for use in various industries such as military and weapon development. Thus, the study allows effective simulation of complex penetration problems which will prevent various material failures thus advance their application in numerous industries. It also forms a reference for future research aimed at improving the simulation processes.
Chen, X., Lu, F., & Zhang, D. (2018). Penetration trajectory of concrete targets by ogived steel projectiles–Experiments and simulations. International Journal of Impact Engineering, 120, 202-213.Go To International Journal of Impact Engineering