Mechanism of Strain Rate Effect Based on Dislocation Theory

Based on dislocation theory, we investigate the mechanism of strain rate effect. Strain rate effect and dislocation motion are bridged by Orowan＇s relationship, and the stress dependence of dislocation velocity is considered as the dynamics relationship of dislocation motion. The mechanism of strain rate effect is then investigated qualitatively by using these two relationships although the kinematics relationship of dislocation motion is absent due to complicated styles of dislocation motion. The process of strain rate effect is interpreted and some details of strain rate effect are adequately discussed. The present analyses agree with the existing experimental results. Based on the analyses, we propose that strain rate criteria rather than stress criteria should be satisfied when a metal is fully yielded at a given strain rate.     

空洞探测的最优解法

本文论述在探测过程中 ,对山体、坝体、隧洞等某些内部空洞定位问题 .问题简化后 ,通过对平面进行区域 (我们把它叫做像元 )划分 ,对波宽带化后 ,波经过某空洞像元 ,此像元必对波在时间上有贡献 ,因而在每个空气洞像元必减慢一个时间单位数 (波通过单位空洞所需时间 ) ,进而建立线性方程组模型 .从而解决空洞定位问题     

Strain Rate Sensitivities of Face-Centred-Cubic Metals Using Molecular Dynamics Simulation

We use dislocation theory and molecular dynamics （MD） simulations to investigate the effect of atom properties on the macroscopic strain rate sensitivity of f cc metals. A method to analyse such effect is proposed. The stress dependence of dislocation velocity is identified as the key of such study and is obtained via 2-D MD simulations on the motion of an individual dislocation in an fcc metal. Combining the simulation results with Orowan＇s relationship, it is concluded that strain rate sensitivities of fcc metals are mainly dependent on their atomic mass rather than the interatomic potential. The order of strain rate sensitivities of five fcc metals obtained by analysing is consistent with the experimental results available.     

一种基于微孔洞聚合模型的韧性材料失效判据

通过对阵列微孔洞附近应力场的三维有限元数值模拟计算,分析了韧性材料动态失效强度与材料应变率和材料中微孔洞相对间距的数值关系.基于微孔洞聚合模型,通过对微孔洞相对间距与微孔洞附近局部静水拉应力之间数值关系的分析,认为微孔洞之间韧带上静水拉应力对微孔洞相对间距很敏感,从而建立了以微孔洞相对间距和静水拉应力为参数的韧性材料动态失效判据.基于此失效判据,通过数值模拟得到韧性材料在不同应变率下的材料失效强度,并且可以合理解释韧性材料的动态失效.     

平潭跨海大桥防船撞拦阻系统阻拦效能实验研究

本文介绍了一种新型的桥梁防船撞拦阻系统,以及该系统应用于平潭跨海大桥时所进行的实船拦阻实验。该防船撞拦阻系统由浮体、限载式拦索及锚链等组成,可以在船舶驶入时自动翻转并通过拖曳损耗船体动能最终保护桥梁安全。针对实船实验较为恶劣的环境,利用单目视觉测量技术,通过高速影像记录、数字图像处理及力学模型分析得到了实验船在受阻拦条件下的运动及受力,进而评估船舶进入阻拦区后阻拦系统的工作过程及工作效能。实验结果表明该技术能有效地对桥梁进行撞击防护。