金属材料层裂破坏的内聚力模型

本文把内聚力单元嵌入到连续介质有限元单元之间，构建了一个层裂破坏的内聚力模型，以计及层裂破坏过程中能量耗散行为。采用该模型对平板撞击条件下的20号钢层裂实验进行了数值模拟研究，重点讨论了内聚力模型特征参数对计算结果的影响规律。研究结果表明采用指数型损伤演化行为的内聚力模型可以较好地描述弹塑性材料层裂破坏过程中的非线性能量耗散行为。利用一发实测自由面速度波剖面对计算结果进行对比校准，可确定内聚力模型特征参数。该特征参数可同样成功地预示不同撞击速度下的层裂实验，获得的模拟曲线与实验曲线之间符合程度很好，特别是自由面速度“回跳”后波形振荡周期和幅值与实验结果非常接近。这表明了内聚力模型在描述层裂过程中能量耗散行为方面具有较好适用性，并且不难由简单实验标定相关的特征参数。

COHESIVE ZONE MODELING OF SPALLATION IN DUCTILE METALS

In this work, a cohesive zone model (CZM) is developed by means of embedding cohesive elements into FEM continuum elements, so that the energy dissipated in the separation of the fracture surfaces during spalling can be taken into account. The proposed numerical model is used to predict the rear free surface velocity profiles in flyer plate impact tests for steel samples under different impact velocities. The influences of the characteristic parameters of CZM on the computed free surface velocity profiles are discussed in detail. The simulation results indicate that the exponential damage evolution of cohesive elements is satisfied to describe the energy dissipated behavior during spalling. Once the characteristic parameters are calibrated by a reference test, the same parameters of CZM can be used to successfully predicte other free surface velocity profiles under different impact velocities. A satisfied agreement between the predictions and the experimental data , especially the oscillation frequency and decay of the free surface velocity profiles in the later phases of spalling. The results thus demonstrate that the proposed cohesive law is appropriated to characterize the energy dissipated behavior during spallation.