On size scaling in shock hydrodynamics and the stress-strain behavior of copper at exceedingly high strain rates

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In recent years the Hypervelocity Microparticle Impact (HMI) project at Los Alamos has utilized electrostatically accelerated iron spheres of microscopic dimensions to generate hypervelocity impact experiments to about 100 {times} 10{sup 5} cm/sec, about an order of magnitude beyond the data range for precisely controlled impact tests with ordinary macroscopic particles. But the extreme smallness of the micro impact events brings into question whether the usual shock-hydrodynamic size scaling can be assumed. It is to this question of the validity of size scaling (and its refinement) that the present study is directed. Hypervelocity impact craters are compared in which the ... continued below

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Walsh, J.M.; Stradling, G.L.; Idzorek, G.C.; Shafer, B.P. (Los Alamos National Lab., NM (United States)) & Curling, H.L. Jr. (Science Applications International Corp., Albuquerque, NM (United States)) January 1, 1991.

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In recent years the Hypervelocity Microparticle Impact (HMI) project at Los Alamos has utilized electrostatically accelerated iron spheres of microscopic dimensions to generate hypervelocity impact experiments to about 100 {times} 10{sup 5} cm/sec, about an order of magnitude beyond the data range for precisely controlled impact tests with ordinary macroscopic particles. But the extreme smallness of the micro impact events brings into question whether the usual shock-hydrodynamic size scaling can be assumed. It is to this question of the validity of size scaling (and its refinement) that the present study is directed. Hypervelocity impact craters are compared in which the two impact events are essentially identical except that the projectile masses and crater volumes differ by nearly 12 orders of magnitude -- linear dimensions and times differing by 4 orders of magnitude. Strain rates at corresponding points increase 4 orders of magnitude in the size reduction. Departures from exact scaling, by a factor of 3.7 in crater volume, are observed for copper targets -- with the micro craters being smaller than scaling would predict. This is attributed to a factor 4.7 higher effective yield stress occurring in the micro cratering flow. This, in turn, is because the strain rate there is about 10{sup 8}/sec as compared to a strain rate of only 10{sup 4}/sec in the macro impact. The measurement of impact craters for very small impact events leads to the determination of metal yield stresses as strain rates more than two orders of magnitude greater than have been obtained by other methods. The determination of material strengths at these exceedingly high strain rates is of obvious fundamental importance. 10 refs., 4 figs.

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Pages: (10 p)

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OSTI; NTIS; GPO Dep.

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  • Workshop on hypervelocity impacts in space, Canterbury (United Kingdom), 1-5 Jul 1991

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  • Other: DE92003797
  • Report No.: LA-UR-91-3495
  • Report No.: CONF-9107182--3
  • Grant Number: W-7405-ENG-36
  • Office of Scientific & Technical Information Report Number: 6359719
  • Archival Resource Key: ark:/67531/metadc1211352

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  • January 1, 1991

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  • July 5, 2018, 11:11 p.m.

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  • Aug. 7, 2018, 4:02 p.m.

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Walsh, J.M.; Stradling, G.L.; Idzorek, G.C.; Shafer, B.P. (Los Alamos National Lab., NM (United States)) & Curling, H.L. Jr. (Science Applications International Corp., Albuquerque, NM (United States)). On size scaling in shock hydrodynamics and the stress-strain behavior of copper at exceedingly high strain rates, article, January 1, 1991; United States. (digital.library.unt.edu/ark:/67531/metadc1211352/: accessed January 15, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.