On size scaling in shock hydrodynamics and the stress-strain behavior of copper at exceedingly high strain rates
- Los Alamos National Lab., NM (United States)
- Science Applications International Corp., Albuquerque, NM (United States)
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.
- Research Organization:
- Los Alamos National Lab., NM (United States)
- Sponsoring Organization:
- USDOE; USDOE, Washington, DC (United States)
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 6359719
- Report Number(s):
- LA-UR-91-3495; CONF-9107182-3; ON: DE92003797
- Resource Relation:
- Conference: Workshop on hypervelocity impacts in space, Canterbury (United Kingdom), 1-5 Jul 1991
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
42 ENGINEERING
COPPER
YIELD STRENGTH
IMPACT TESTS
STRAIN RATE
ALUMINIUM
HYDRODYNAMICS
IRON
SPHERES
ELEMENTS
FLUID MECHANICS
MATERIALS TESTING
MECHANICAL PROPERTIES
MECHANICAL TESTS
MECHANICS
METALS
TESTING
TRANSITION ELEMENTS
360103* - Metals & Alloys- Mechanical Properties
420500 - Engineering- Materials Testing