Issue 38

M. Sokovikov et alii, Frattura ed Integrità Strutturale, 38 (2016) 296-304; DOI: 10.3221/IGF-ESIS.38.40 299 Figure 4 : Specimen between the input and output Split Hopkinson (Kolsky) bars. The area indicated by an arrow is in a predominant shear state. Tested specimen. Temperature distribution by coordinate normally to the shear area and infrared image during deformation. Figure 5 : 3D image of the surface of a deformed specimen. A ballistic set-up was used to realize dynamic penetration test for A6061 alloy samples. In the event of high-speed projectile-target interaction, the failure is realized as plug formation and ejection. The study of the process of target perforation with aid of a high-speed infra-red camera in a real-time mode indicates that the values of temperature in the areas of plastic strain localization are equal to ~100°C at most. Fig.6 shows the infrared images of the plugged hole and the flying pug. The velocity, at which the projectile strikes the target, is 120m/s. The maximum temperature at the hole periphery is 62°C, [7]. Fig.7 represents an infrared picture illustrating the back surface of the target in the process of plug formation. The process of plug formation and ejection was studied using a laser Doppler velocimeter VISAR. As a result, we obtained the time dependence of the free surface velocity in the area of plug formation and ejection, Fig.8. After the completion of the test, the microstructure of the deformed specimens was analyzed with the aid of an optical interferometer-profiler profiler New-View 5010 and a scanning electron microscope, [8]. It has been found that the distribution of strain is relatively uniform in the initial penetration region with a smooth mirror- like fracture surface, whereas in the plug formation and ejection regions it becomes essentially non-uniform over the radius of the specimen. The localization of plastic strain occurs in a thin region on the plug generation.