Investigations On Long Projectiles Penetrating Into Concrete Targets

The relationships among penetration resistance, penetration depth, projectile shapes, concrete properties and penetrating velocity are analyzed approximately by means of semi-empirical methods and cavity-expansion penetration models. By collecting and analyzing Forrestal's penetrating experiments data, a simple relation expression between concrete strength constant S and concrete strength a is obtained. Our experiments indicate that if the S obtained from the expression is substituted into the penetrating depth equation deduced from the semi-empirical method, a good agreement with experimental penetrating depth will be received.A series of scaling penetrating experiments have been conducted on gas guns, and penetrating depth curves have been fitted to experimental data. Comparing predicted depth curves from cavity-expansion models with experimental depth curves, it can be find that the two kinds of depth curve have a similar trend, but the predicted depth value is larger than the experimental depth value slightly. Using cavity-expansion models to analyze the penetration process, we find that the sharpness of a projectile head and concrete strength will affect the penetrating depth notably.The similarity between prototype and model experiments is analyzed theoretically. The analysis indicates if the size effects are neglected, prototypes and models are built up in same material, and prototypes and models are similar in geometry, the penetrating depth will accord with scaling law. But if the size effects mayn't be neglected, the tenability of scaling law will be imperfect. Because of the stress ratio effect and fracture size effect induced by size effects, the capability of anti-fracture of a prototype is lower than that of a model. This implies that when the studying goal is at the limited structural strength of a penetrator or a target, the size effects should be taken into account, and the credibility of a prototype shouldn't be deduced from model experiments directly.Three main damage effects of earth penetrating warheads, including explosion, blasting and earthquake, are analyzed respectively. These analyzing results will be useful to evaluate the destroy effects of earth penetrating weapons.A penetrating experimental system based on gas guns had been built up. This system not only has been used to conduct penetrating experiments successfully, but also will be used to conduct the advance experimental studies on penetration and protection, penetrator structure, fuse survival, charge configuration and so on.