Pressure-Dependent, Infrared-Emitting Phenomenon in Hypervelocity Impact

Mihaly, Jonathan M. and Tandy, Jonathan D. and Rosakis, A. J. and Adams, M. A. and Pullin, D. (2014) Pressure-Dependent, Infrared-Emitting Phenomenon in Hypervelocity Impact. Journal of Applied Mechanics, 82 (1). pp. 1-9. ISSN 0021-8936

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Official URL: http://dx.doi.org/10.1115/1.4028856

Abstract

A series of hypervelocity impact experiments were conducted with variable target chamber atmospheric pressure ranging from 0.9 to 21.5 Torr. Using a two-stage light-gas gun, 5.7 mg nylon 6/6 right-cylinders were accelerated to speeds ranging between 6.0 and 6.3 km/s to impact 1.5 mm thick 6061-T6 aluminum plates. Full-field images of near-IR emission (0.9 to 1.7 lm) were measured using a high-speed spectrograph system with image exposure times of 1 ls. The radial expansion of an IR-emitting impact-generated phenomenon was observed to be dependent upon the ambient target chamber atmospheric pressures. Higher chamber pressures demonstrated lower radial expansions of the subsequently measured IR-emitting region uprange of the target. Dimensional analysis, originally presented by Taylor to describe the expansion of a hemispherical blast wave, is applied to describe the observed pressure-dependence of the IR-emitting cloud expansion. Experimental results are used to empirically determine two dimensionless constants for the analysis. The maximum radial expansion of the observed IR-emitting cloud is described by the Taylor blast-wave theory, with experimental results demonstrating the characteristic nonlinear dependence on atmospheric pressure. Furthermore, the edges of the measured IR-emitting clouds are observed to expand at extreme speeds ranging from approximately 13 to 39 km/s. In each experiment, impact ejecta and debris are simultaneously observed in the visible range using an ultrahigh-speed laser shadowgraph system. For the considered experiments, ejecta and debris speeds are measured between 0.6 and 5.1 km/s. Such a disparity in observed phenomena velocities suggests the IR-emitting cloud is a distinctly different phenomenon to both the uprange ejecta and downrange debris generated during a hypervelocity impact.

Item Type: Article
Additional Information: Written permission was granted by the publisher to use the publisher's version - 21/06/2016. Copyright © 2015 by ASME
Subjects: 500 Natural Sciences and Mathemetics > 530 Physics
600 Technology > 620 Engineering & allied operations
Department: School of Human Sciences
Depositing User: Jonathan Tandy
Date Deposited: 01 Jul 2016 09:18
Last Modified: 20 Jul 2017 13:34
URI: http://repository.londonmet.ac.uk/id/eprint/1021

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