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Title: Voltages across assembly joints due to direct-strike lightning currents

Abstract

An extensive set of direct-strike lightning tests has been carried out on a set of facsimile assembly joints of the kinds employed in the design of nuclear weapon cases. Taken as a whole, the test hardware included all the conceptual design elements that are embodied, either singly or in combination, in any specific assembly joint incorporated into any stockpiled weapon. During the present testing, the effects of all key design parameters on the voltages developed across the interior of the joints were investigated under a range of lightning stroke current parameter values. Design parameter variations included the types and number of joint fasteners, mechanical preload, surface finish tolerance and coatings, and the material from which the joint assembly was fabricated. Variations of the simulated lightning stroke current included amplitude (30-, 100-, and 200-kA peak), rise time, and decay time. The maximum voltage observed on any of the test joints that incorporated proper metal-to-metal surface contact was 65 V. Typical response values were more on the order of 20 V. In order to assess the effect of the presence of a dielectric coating (either intentional or as a result of corrosion) between the mating surfaces of a joint, a special configurationmore » was tested in which the mating parts of the test assembly were coated with a 1-mil-thick dielectric anodizing layer. First strokes to these test assemblies resulted in very narrow voltage spikes of amplitudes up to 900 V. The durations of these spikes were less than 0.1 {mu}s. However, beyond these initial spikes, the voltages typically had amplitudes of up to 400 V for durations of 3 to 5 {mu}s.« less

Authors:
 [1];  [2]
+ Show Author Affiliations
  1. Quatro Corp., Albuquerque, NM (United States)
  2. Sandia National Labs., Albuquerque, NM (United States)
Publication Date:
Research Org.:
Sandia National Labs., Albuquerque, NM (United States)
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
10190346
Report Number(s):
SAND-93-0788
ON: DE95001791; BR: GB0103012
DOE Contract Number:
AC04-94AL85000
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: Aug 1994
Country of Publication:
United States
Language:
English
Subject:
45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEFENSE; NUCLEAR WEAPONS; ELECTRICAL TESTING; LIGHTNING; JOINTS; FLANGES; ALUMINIUM; 450200; NUCLEAR EXPLOSIONS AND EXPLOSIVES

Citation Formats

Dinallo, M.S., and Fisher, R.J. Voltages across assembly joints due to direct-strike lightning currents. United States: N. p., 1994. Web. doi:10.2172/10190346.
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Dinallo, M.S., & Fisher, R.J. Voltages across assembly joints due to direct-strike lightning currents. United States. doi:10.2172/10190346.
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Dinallo, M.S., and Fisher, R.J. Mon . "Voltages across assembly joints due to direct-strike lightning currents". United States. doi:10.2172/10190346. https://www.osti.gov/servlets/purl/10190346.
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@article{osti_10190346,
title = {Voltages across assembly joints due to direct-strike lightning currents},
author = {Dinallo, M.S. and Fisher, R.J.},
abstractNote = {An extensive set of direct-strike lightning tests has been carried out on a set of facsimile assembly joints of the kinds employed in the design of nuclear weapon cases. Taken as a whole, the test hardware included all the conceptual design elements that are embodied, either singly or in combination, in any specific assembly joint incorporated into any stockpiled weapon. During the present testing, the effects of all key design parameters on the voltages developed across the interior of the joints were investigated under a range of lightning stroke current parameter values. Design parameter variations included the types and number of joint fasteners, mechanical preload, surface finish tolerance and coatings, and the material from which the joint assembly was fabricated. Variations of the simulated lightning stroke current included amplitude (30-, 100-, and 200-kA peak), rise time, and decay time. The maximum voltage observed on any of the test joints that incorporated proper metal-to-metal surface contact was 65 V. Typical response values were more on the order of 20 V. In order to assess the effect of the presence of a dielectric coating (either intentional or as a result of corrosion) between the mating surfaces of a joint, a special configuration was tested in which the mating parts of the test assembly were coated with a 1-mil-thick dielectric anodizing layer. First strokes to these test assemblies resulted in very narrow voltage spikes of amplitudes up to 900 V. The durations of these spikes were less than 0.1 {mu}s. However, beyond these initial spikes, the voltages typically had amplitudes of up to 400 V for durations of 3 to 5 {mu}s.},
doi = {10.2172/10190346},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Aug 01 00:00:00 EDT 1994},
month = {Mon Aug 01 00:00:00 EDT 1994}
}
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Technical Report:
View Technical Report (4.32 MB)
DOI:  10.2172/10190346
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  • ; ;
    A variety of cylindrical tests objects of generic interest were tested to simulated severe direct-strike lightning with the intent of bounding possible internal voltages due to joint leakage and currents through low-impedance loads due to diffusion. All the test objects would normally be considered to be high-quality Faraday shields. The highest voltage recorded was 21 V, which was developed across a flange-and-collar joint in a steel cylinder driven longitudinally by a test current of /approximately/160 kA peak. A simple circuit model of the symmetric diffusion process, valid over the frequency range of lightning, is given. 4 refs., 14 figs., 2more » tabs.« less

  • ;
    One mechanism for the penetration of lightning energy into the interior of a weapon is by current diffusion through the exterior metal case. Tests were conducted in which simulated lightning currents were driven over the exteriors of similar aluminum and ferrous steel cylinders of 0.125-in wall thickness. Under conditions in which the test currents were driven asymmetrically over the exteriors of the cylinders, voltages were measured between various test points in the interior as functions of the amplitude and duration of the applied current. The maximum recorded open-circuit voltage, which occurred in the steel cylinder, was 1.7 V. On separatemore » shots, currents flowing on a low impedance shorting conductor between the same set of test points were also measured, yielding a maximum current of 630 A, again occurring across the interior of the steel cylinder. Under symmetrical exterior drive current conditions, a maximum end-to-end internal voltage of 4.1 V was obtained, also in the steel cylinder, with a corresponding current of 480 A measured on a coaxial conductor connected between the two end plates of the cylinder. Data were acquired over a range of input current amplitudes between about 40 and 100 kA. These data provide the experimental basis for validating models that can subsequently be applied to real weapons and other objects of interest.« less

  • The University of Florida has surveyed all relevant publications reporting lightning damage to metals, metals which could be used as components of storage containers for nuclear waste materials. We show that even the most severe lightning could not penetrate the stainless steel thicknesses proposed for nuclear waste storage casks.

  • ; ; ; ...
    Simple formulas are given for the interior voltages appearing across bolted joints from exterior lightning currents. External slot and bolt inductances as well as internal slot and bolt diffusion effects are included. Both linear and ferromagnetic wall materials are considered. A useful simplification of the slot current distribution into linear stripline and cylindrical parts (near the bolts) allows the nonlinear voltages to be estimated in closed form.

  • ; ; ; ...
    The University of Florida has surveyed all relevant publications reporting lightning characteristics and presents here an up-to-date version of the direct-strike lightning environment specifications for nuclear weapons published in 1989 by R. J. Fisher and M. A. Uman. Further, we present functional expressions for current vs. time, current derivative vs. time, second current derivative vs. time, charge transfer vs. time, and action integral (specific energy) vs. time for first return strokes, for subsequent return strokes, and for continuing currents; and we give sets of constants for these expressions so that they yield approximately the median and extreme negative lightning parametersmore » presented in this report. Expressions for the median negative lightning waveforms are plotted. Finally, we provide information on direct-strike lightning damage to metals such as stainless steel, which could be used as components of storage containers for nuclear waste materials; and we describe UF's new experimental research program to add to the sparse data base on the properties of positive lightning. Our literature survey, referred to above, is included in four Appendices. The following four sections (II, III, IV, and V) of this final report deal with related aspects of the research: Section II. Recommended Direct-Strike Median and Extreme Parameters; Section III. Time-Domain Waveforms for First Strokes, Subsequent Strokes, and Continuing Currents; Section IV. Damage to Metal Surfaces by Lightning Currents; and Section V. Measurement of the Characteristics of Positive Lightning. Results of the literature search used to derive the material in Section II and Section IV are found in the Appendices: Appendix 1. Return Stroke Current, Appendix 2. Continuing Current, Appendix 3. Positive Lightning, and Appendix 4. Lightning Damage to Metal Surfaces.« less