Application of 3D image correlation for full-field transient plate deformation measurements during blast loading

Abstract

A high-speed stereo-vision system is employed to quantify dynamic material response during buried blast loading. Deformation measurements obtained using 3D image correlation of synchronized, patterned stereo-vision images obtained with an inter-frame time in the range 16 μs ≤ t ≤ 40 μs indicate that (a) buried blast loading initially induces highly localized material response directly under the buried blast location, with severity of the blast event a strong function of depth of explosive burial, (b) for relatively shallow (deep) depth of explosive burial, plate surface velocities and accelerations exceed 220 m s −1 (100 m s −1) and 6 × 10 6 m s −2 (1.5 × 10 6 m s −1) during the first 30 μs (80 μs) after detonation, respectively. In addition, full-field plate deformation measurements demonstrate that the specimen experienced (c) measured effective strains exceeding 8% (5%) and effective strain rates exceeding 4000 s −1 (1500 s −1) during the first 50 μs (80 μs), respectively and (d) a blast-induced, circularly symmetric, transient bending wave was induced in the plate that travels with radial velocity of Mach 2 (1.25) during blast loading. By combining the Cowper–Symonds constitutive relation with full-field strain and strain rate measurements, well-defined yield boundaries are evident on the plate surface during blast loading; the presence of spatial gradients in yield stress has the potential to affect plate failure processes during transient blast loading events.