High-velocity fragmentation of titanium alloy rings and cylinders produced using Field-Assisted Sintering Technology

Abstract

This paper explores the mechanics of high-velocity impact fragmentation in titanium alloys produced by Field-Assisted Sintering Technology. For that purpose, we have utilized the experimental setups recently developed by Nieto-Fuentes et al. (J Mech Phys Solids 174:105248, 2023a; Int J Impact Eng 180:104556, 2023b) for conducting dynamic expansion tests on rings and cylinders. The experiments involve firing a conical-nosed cylindrical projectile using a single-stage ight-gas gun against the stationary ring/cylinder at velocities ranging from \(\approx 248~\text {m}/\text {s}\) to \(\approx 390~\text {m}/\text {s}\), corresponding to estimated strain rates in the specimen varying from \(\approx 10050~\text {s}^{-1}\) to \(\approx 19125~\text {s}^{-1}\). The diameter of the cylindrical part of the projectile exceeds the inner diameter of the ring/cylinder, causing the latter to expand as the projectile moves forward, resulting in the formation of multiple necks and fragments. Two different alloys have been tested: Ti6Al4V and Ti5Al5V5Mo3Cr. These materials are widely utilized in aeronautical and aerospace industries for constructing structural elements such as compressor parts (discs and blades) and Whipple shields, which are frequently exposed to intense mechanical loading, including high-velocity impacts. However, despite the scientific and technological significance of Ti6Al4V and Ti5Al5V5Mo3Cr, and the extensive research on their mechanical and fracture behaviors, to the best of the authors’ knowledge, no systematic study has been conducted thus far on the dynamic fragmentation behavior of these alloys. Hence, this paper presents an ambitious fragmentation testing program, encompassing a total of 27 and 29 experiments on rings and cylinders, respectively. Monolithic and multimaterial samples—half specimen of Ti6Al4V and half specimen of Ti5Al5V5Mo3Cr—have been tested, taking advantage of the ability of Field-Assisted Sintering Technology to produce multimaterial parts. The fragments have been collected, weighed, sized, and analyzed using scanning electron microscopy. The experiments have shown that the number of necks, the number of fragments, and the proportion of necks developing into fragments generally increase with expansion velocity. The average distance between necks has been assessed against the predictions of a linear stability analysis (Zhou et al. in Int J Impact Eng 33:880–891 2006; Vaz-Romero et al. in Int J Solids Struct 125:232–243, 2017), revealing satisfactory agreement between theoretical predictions and experimental results. In addition, the experimental results have been compared with tests reported in the literature for various metals and alloys (Nieto-Fuentes et al. in J Mech Phys Solids 174:105248, 2023a; Zhang and Ravi-Chandar in Int J Fract 142:183–217, 2006, Zhang and Ravi-Chandar in Int J Fract 150:3–36, 2008) to examine the influence of material behavior on the statistics of fragments size and necks spacing.