Discrete shear failure planes resulting from oblique hypervelocity impacts

Abstract

A combination of laboratory and numerical experiments examines the role of shear localization in subsurface damage following very oblique (15-30°) hypervelocity impacts. Laboratory experiments reveal subsurface damage planes ("blades") parallel to the impact trajectory for highly oblique impacts (15-30°), which are characterized by unique surface textures relative to other failure regions. Observations of growth rate and surface texture of the damage planes combined with three-dimensional CTH simulations indicate that the blades are the result of frictional processes during localized shear deformation. Laboratory experiments also reveal that impact angle and projectile failure play a role in the development of these blades: aluminum projectiles result in distinct along-trajectory blades for both 15°and 30°impacts, whereas the blades are weakly developed for Pyrex projectiles and nonexistent for planar polymethylmethacrylate projectiles. The blades form early in the cratering process and are signatures of the projectile momentum being transferred into the target. Based on the growth rate, and melting seen along the surface of these damage planes, the blades may provide an analog for the generation of pseudotachylytes during the early stages of impact crater formation.

Peak Bone Mass and Quantitative Ultrasound Bone Properties in Young Adulthood: A Study in the PEAK-25 Cohort of Women

“…The central column of damage is due to tensile failure as shock waves coalesce and concentrate at the farside of the target [Rinehart, 1960] (Figure 6, 7, and 10). The planes, however, are formed by shear stresses set up behind the shock wave ( Figures 5-8, and 10), similar to the blades observed in oblique impacts into PMMA blocks [Stickle and Schultz, 2010;Stickle and Schultz, 2011;Stickle and Schultz 2014]. Regardless of impact angle, the interior failure planes begin to form around 50 ȝsec after impact (Figure 2, 5), when shear stresses are highest near the middle of the sphere (Figure 10).…”

Ambient Noise Tomography Reveals Asymmetric Impact Damage Zone Beneath Lonar Crater, India: Implications for Oblique Impact Cratering in Heterogeneous Basalt, With Planetary Applications

“…Stickle and Schultz (2011, 2012, 2014) performed a suite of impact experiments and numerical simulations to understand the oblique impacts on subsurface failure morphologies, and the extent and geometry of damage beneath the impact craters, using planar polymethylmethacrylate (PMMA) transparent targets that allowed observations of the growth history of damage beneath the craters following the impact. The numerical simulations also reproduced the results shown by the impact experiments.…”

“…The crater shows three types of fractures; see text for more details. (b) Different types of main damage regions beneath the oblique impact crater in the PMMA target (Stickle & Schultz, 2014). The impact is from left to right (see the black arrow).…”

“…For example, beneath the 1.2 km diameter Barringer Meteorite Crater, impact damage was observed up to a depth of ∼1 km (Ackermann et al., 1975). Experimental impact craters provided excellent images of impact damage beneath them (e.g., Dahl & Schultz, 2001, 2016; Polanskey & Ahrens, 1990; Stickle & Schultz, 2011, 2012, 2014). While the vertical impacts produced symmetrical damage zones, the oblique impact events gave rise to asymmetric damage zones beneath the craters.…”