EFFECT OF SURFACE ROUGHNESS ON THE FORMATION OF SHEAR BAND IN Ti-6Al-4V ALLOY CYLINDRICAL SHELL

Shear band is one of the special deformations and damage forms of materials under high strain rate loading. The research on the sensitive factors and mechanism of shear band formation in metal materials has always been one of the key issues in scientific research and engineering design. In the process of high-speed collapse of cylindrical shell, the shear band nucleates preferentially in the inner surface, and its nucleation and propagation behavior are significantly affected by the mesoscopic state of the inner surface. In the presented study, the detonation loading of Ti-6AL-4V alloy cylindrical shell was carried out by thick walled cylinder collapse experiment. Combined with surface treatment technology, microstructure characterization technology and shear banding analysis model, the effect of inner surface roughness on the law of mesodynamics of shear band formation in Ti-6AL-4V alloy cylindrical shell was studied through the shear band pattern in samples. The experimental results show that the inner surface roughness has a significant effect on the formation of adiabatic shear bands in Ti-6AL-4V alloy cylindrical shells under high strain rate. The number, length and nucleation rate of adiabatic shear bands in the specimen increase with the increase of the inner surface roughness under the same deformation condition. The results indicate that, the larger surface roughness leads to a stronger shielding effect for the shear bands. Furthermore, the propagating velocity and length of partial adiabatic shear bands in the specimen increase with the increase of the inner surface roughness. The experimental results of shear band spacing are in good agreement with the prediction of W-O model and M model, but the spacing values are influenced by the inner surface roughness of the specimen. With the increase of the inner surface roughness, the experimental results are gradually smaller than the prediction of models.