弹丸侵彻无钢筋混凝土的数值模拟

采用二维梁-颗粒模型BPM^2D（beam-particle model in two dimensions）模拟了刚性弹丸侵彻无钢筋混凝土的过程.离散元法（DEM）和有限元法（FEM）等数值计算方法各有其优势,同时也都存在不足之处：离散元法适于处理由连续介质向非连续介质转化的破坏问题,但对于连续体计算结果精度不高;有限元法适于预测材料破坏的区域,但难以直接用于计算脆性材料破坏过程,因此将两种方法结合可以形成一种较好的混合模型.梁-颗粒模型BPM^2D是基于离散元法,结合有限元法开发的二维数值计算模型,采用3种类型梁单元形成混凝土数值试样,每种类型梁单元的力学性质均按韦伯（Weibull）分布随机赋值,以模拟混凝土细观结构的非均匀性,同时梁单元的强度随应变率不同而变化.利用此模型分析了弹丸侵彻下混凝土的破坏过程,并给出侵彻过程弹丸减速度-时间历程曲线.比较计算结果与试验数据表明梁-颗粒模型可有效应用于计算和模拟脆性材料动态破坏问题.

Numerical simulation of projectile penetrating into plain concrete

The process of the projectile penetrating into plain concrete is numerically simulated with the BPM2D(beam-particle model in two dimensions).The discrete element method(DEM) and the finite element method(FEM) have their own advantages and weaknesses.Basically,the DEM was developed for predicting the failure problems accompanying with the transition from continuum to non-continuum media.However,it is not accurate to calculate the problem of continuum media.The FEM may forecast the failure area of the material reasonably,while it is hard to calculate the failure process in brittle media.Therefore it becomes a good choice to combine the two methods to construct a hybrid model.The BPM2D is presented on the basis of the DEM and the FEM.Three types of beam in the BPM2D have been used to form numerical model of concrete.The mechanical properties of every type beam vary with their strain-rate and are randomly allocated according to Weibull distribution to reflect the initial heterogeneity of concrete at the mesoscale level.The failure process of the projectile penetrating into concrete is discussed.It was displayed that the deceleration history of projectile in penetrating.The comparison of the simulation results with the experimental data shows that the BPM2D is applicable to simulate the dynamic failure problems of brittle material.