钛合金(Ti—17)的动态力学性能和损伤特性

DYNAMIC MECHANICAL PROPERTIES AND DAMAGE CHARACTERISTICS OF TITANIUM ALLOY(Ti-17)

利用分离式Ｈｏｐｋｉｎｓｏｎ压杆冲击加载装置，采用圆柱和锥台两种试样，在高应变速率加载条件下研究Ｔｉ－１７合金的应力应变响应和动态损伤特征实验结果表明，动态屈服应力和断裂应力比静态相应值高宏观损伤对应变速率敏感，而对应力不敏感，出现宏观损伤的临界应变速率．试样微观解剖显示绝热剪切带是材料宏观损伤的先兆，试样主要沿剪切带发生破坏、在垂直加载轴的横截面上，绝热剪切带呈圆弧形，平行加载轴剖面上绝热剪切带沿最大剪切应力方向．

Dynamic mechanical properties and damage characteristics of Ti-17 alloy have beeninvestigated using Split-Hopkinson Pressure Bar (SHPB) at high strain rate of 103 s-1 for cylinder andfrustum samples. The experimental results show that the dynamic yield stress(yd) and the fracture stress(bd) are higher than those in the static, and the macro-damage is sensitive to strain rate, but insensitiveto the applied stress. The critical macro-damage strain rate, e., is 2000 s-1. The examination of thedeformed samples using metallgraphy and SEM reveals that the damage frequently occurs along shearband, i.e. shear band is a kind of micro-damage, and the fracture is always in cutting form. Thesemi-cyclic shape shear band and the fracture surface appear to be of shear dimples. The shear bandis one of micro-damages, and its appearance on the cross-section plane is cyclic, and straight along themaximum shear stress direction on the section plane which is parallel the sample axis. On the sectionplane, the shear bands develop at the place where the shear stress is maximum, and propagate along themaximum shear direction. The shear strain distribution along the shear band within the frustum sampleis inhomogenous, which decreases gradually along the shear band propagation direction.