Hypervelocity Impact Response of Ti-6Al-4V and Commercially Pure Titanium

Titanium alloy, Ti-6Al-4V, and commercially pure (CP) Titanium will be used to protect the Solar Probe Plus (SPP) spacecraft against hypervelocity impacts by solar dust particles. The results of six hypervelocity impact (HVI) tests performed on Ti-6Al-4V and CP monolithic samples (3 each) arc evaluated in terms of cratering and spall damage, and compared with crater depth and spall initiation predictions using the Ballistic Limit Equation (BLE) for Titanium shields developed at NASA Johnson Space Center and hydrocode computations. In the tests, 2017-T4 aluminum spheres with a diameter of 2.35 mm were used to impact the shields at an impact velocity of about 7 km/s. In general, the measured and predicted values of crater depth are found to be in good agreement with each other, regardless of the type of Titanium alloy. In terms of spall damage, two of the three Ti-6Al-4V samples exhibit a noticeable incipient spall and one sample shows a very faint incipient spall, whereas only one of the CP samples shows a faint incipient spall. Polished cross sections of the samples also indicate sub-crater damage modes such as microcracking, shear localization and large scale grain deformation, and possibly recrystallization. Differences observed in the macroscopic and microscopic damage phenomenologies exhibited by the two types of Titanium alloys are presented and discussed in terms of their implications on the BLE for shielding design calculations. (C) 2013 The Authors. Published by Elsevier Ltd.
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