Modified reflective Digital Gradient Sensing applied to hypervelocity impact applications

Abstract

Obtaining full-field measurements on materials under hypervelocity impacts is challenging because of the high-speeds involved, and in the case of brittle materials because of small deflections before fracture. Here we present an implementation of a modified Digital Gradient Sensing (DGS) experimental technique that can achieve both high-sensitivity and full-field deformation measurement capability at the same time during a hypervelocity impact. The modified-Reflective Digital Gradient Sensing (mR-DGS) method is used to capture rear surface displacements (with a sensitivity $<0.1\mu m$) of plates of an engineering alloy and an advanced ceramic during high-velocity impact by a spherical impactor. The early time material response of the target material is captured, together with the corresponding surface transients. The approach allows us to capture complex spatial phenomena during the impact event and provides a rich in situ and real time dataset to help develop and validate material models. This approach provides a significant advancement to the study of hypervelocity impacts on materials, and has some advantages over both photon doppler velocimetry and traditional digital image correlation. The resulting full-field measurements can be used to calibrate, discriminate between, and validate material models.