This paper introduces a three-dimensional (3D) simulation to model the elasto-plastic deformation of ductile materials by discrete element method (DEM) using cohesive plastic beam approach. The Euler–Bernoulli beam theory is applied to calculate force and torque reactions of the cohesive beam bond that can account for plastic strain. In order to simulate the elasto-plastic behavior of materials, a coupled model of plasticity and damage is proposed for the cohesive beam bond. The von Mises yield criterion, a modified perfectly plastic law and an exponential damage law are implemented to simulate behaviors of ductile materials such as steel and aluminum in tensile tests. It is then further applied to investigate the ductile fracture modes such as localized shear fracture and necking phenomenon with cup-and-cone shape. Finally, the proposed DEM model using cohesive plastic beam is applied to visualize the compression test of cylindrical steel sample and wrinkle deformation of steel tube under bucking due to axial compression. This paper is the first attempt to model ductile materials by DEM with cohesive beam bond in tension, compression and buckling. All of the numerical benchmarks demonstrate the power of DEM using cohesive beam bond to model ductile materials with fracture, large deformation and elasto-plastic behavior.

本文介绍了三维（3D）仿真，以内聚塑性梁方法通过离散元方法（DEM）对延性材料的弹塑性变形进行建模。欧拉-伯努利梁理论用于计算可解释塑性应变的内聚梁键的力和扭矩反应。为了模拟材料的弹塑性行为，针对内聚梁键，提出了可塑性与损伤的耦合模型。冯·米塞斯屈服准则，修正的完美塑性定律和指数损伤定律被用来模拟拉伸试验中易延展材料（例如钢和铝）的行为。然后将其进一步应用于研究延性断裂模式，例如局部剪切断裂和圆锥形的颈缩现象。最后，提出了一种利用内聚塑性梁的DEM模型来可视化圆柱钢样品的压缩试验以及由于轴向压缩而在屈曲下钢管的皱纹变形。本文是首次尝试通过DEM在拉伸，压缩和屈曲中使用内聚梁键对延性材料进行建模。所有的数值基准都证明了使用内聚束键对具有延展性，大变形和弹塑性行为的延性材料进行建模的DEM的功能。