Accession Number:

ADA045220

Title:

Impact Damage in Single Crystals.

Descriptive Note:

Technical rept. 24 Mar 76-31 Jul 77,

Corporate Author:

EFFECTS TECHNOLOGY INC SANTA BARBARA CALIF

Personal Author(s):

Report Date:

1977-07-31

Pagination or Media Count:

119.0

Abstract:

Single crystals of calcium fluoride, silicon, and magnesium oxide were subjected to quasistatic bead indentations from very low to moderately high load levels as reference for the dynamic loading conditions. 1 mm diameter beads were used in all of the tests reported here. Sapphire beads were propelled at velocities up to 100 ms using a modified air gun arrangement which allows accurate placement of the particle on the surface, measurement of the impact velocity, and eliminates any rotational motions which would normally be imparted to the particle. Nylon beads were propelled at velocities up to 1000 ms using an exploding wire impact facility. Single water drop impacts can now be obtained on these crystals at velocities up to 500 ms, and multiple water drop experiments are carried out in a rotating arm erosion facility at velocities up to 260 ms. Preliminary observations of the damage produced by water drop impacts on CaF2, Si, and MgO are described for impact velocities below the coherent fracture threshold, but the effects of solid particle collisions on these crystals are considered in greater depth. Significantly different damage modes and sequences are observed for CaF2 and MgO subjected to quasistatic sapphire bead indentations, sapphire bead impacts, and nylon bead impacts.

Subject Categories:

  • Crystallography

Distribution Statement:

APPROVED FOR PUBLIC RELEASE