【作者】 孟阳；

【导师】 文鹤鸣；

【作者基本信息】 中国科学技术大学 ， 工程安全与防护技术， 2009， 硕士

【摘要】 钢筋混凝土是防护工程和重要军事设施的最常用建筑材料,研究钢筋混凝土在冲击(侵彻)或爆炸载荷作用下的动态响应具有十分重要的理论和现实的意义。在本文中,我们利用有限元分析程序对钢筋混凝土板在卵形弹丸侵彻或爆炸载荷作用下的动态响应进行了数值模拟研究。论文首先通过对国内外各种混凝土模型和数值模拟方法的历史与现状进行调研,选择适用于大应变、高应变率和高压条件下的Holmqust-Johnson-Cook (HJC)混凝土本构模型进行侵彻和爆炸的数值模拟。其次,对钢筋混凝土靶板在卵形弹丸撞击下的侵彻和穿透进行了有限元(FE)数值模拟,并与用靶体响应力函数的方法所得到的结果进行了比较。经过对比我们发现,采用两种方法得到的弹道极限、残余速度以及侵彻深度一致性较好,并且均同实验结果比较吻合。但是两种方法所得到的弹体等效应力以及等效应变分布有较大的差距,而两者的差距主要在弹头部位,采用靶板FE模型得到的弹头部分的应力值和应变值都远远大于采用力函数法的结果。最后,采用LS-DYNA的流固耦合算法对炸药在钢筋混凝土靶板近场爆炸的过程进行了数值模拟,再现了炸药爆炸后,冲击波的传播过程以及混凝土的破坏情况。数值模拟得到的压力-时程曲线与典型的经验公式计算结果吻合良好,混凝土靶中的破坏特征也与实验现象具有良好的一致性。本文的研究结果表明:采用数值模拟方法能够很好的反映出混凝土在侵彻或爆炸载荷下的破坏形态,并且与现有的试验数据基本吻合。由此可见,利用数值模拟方法研究动能弹侵彻和爆炸冲击问题可以达到较好的精度,是一种切实可行的手段,本文可为进一步的深入研究和工程计算提供参考。但要使结果更加符合实际情况,还需要进一步完善混凝土材料本构模型以及相应的破坏准则。更多还原

【Abstract】 Rreinforced concrete is the most common building material which has been widely used in protective engineering and military installations/facilities, it is, therefore, valuable and significant to study the damage effect and failure characteristic of reinforced concrete targets under impact by projectiles or blast loading. In this dissertation, the impact and blast response of reinforced concrete slabs is studied numerically by using finite element program LS-DYNA.Firstly, the pevious work on the development of concrete materials models and the relevant numerical simulations are critically reviewed and the Holmquist-Johnson-Cook (HJC) model, which can describe the response of concrete subjected to large strains, high strain rates and high pressures loads, is chosen in the numerical study of the response of reinforced concrete slabs to projectile impact and blast loading.Secondly, 3D numerical simulations of reinforced concrete slabs subjectled to impact by an ogival-nosed projectile are conducted using the HJC model, and the numerical results obtained are compared with those obtained by forcing function method where a forcing function is used to represent the target’s response. It is found that the ballistic limits, penetration depths and residual velocities obtained by these two methods are comparable. It is also found that the distribution of the equivalent stress and equivalent plastic strain on the surface of the projectile obtained by these two methods are similar except for the projectile nose surface where the results obtained by FE methods are much larger than those obtained by forcing function approach.Finally, the response of reinforced concrete slabs under explosive loading is studied numerically by the fluid-solid coupled method of LS-DYNA. The numerical simulation reproduced the transient process of the shock wave and the main rupture process of the slabs. The numerically obtained pressure-time histories are found to be in reasobale agreement with those predicted by the empirical equations and the failure patterns obtained by the numerical simulation is found to be similar to those obtained experiemtally.更多还原