STP733

    Localized Deformation and Fracture of Magnesium Oxide

    Published: Jan 1981


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    Abstract

    Particulate erosion of brittle materials is a complex process of fracture nucleation, growth, and interaction which leads to removal of material from the exposed surface. The temporal and spatial development of the localized pressure loading imparted to a material surface by a water-drop or soft-body collision is not clearly defined. For the impact conditions investigated, the duration of the applied pressure pulse is generally less than 100 ns. Correspondingly, the exact form of the transient stress states generated within the impacted body is not easily determined. However, insights into the nature of the damage produced by these relatively short stress cycles are being obtained from microscope examinations of the residual deformation and fracture patterns in transparent materials. The response of single crystals of magnesium oxide to water-drop collisions is described. It was found that for the high strain rates imposed slip and fracture occur in the same systems and planes as are associated with quasi-static deformations. However, water-drop impacts produce slip only on the four {110}45-deg slip systems, whereas rounded solid particles produce dominant slip on two {110} 90-deg slip systems, as well as on the {110} 45-deg slip systems. The fractures associated with each condition are also distinctly different. It was also found that fracture initiation could be suppressed with the introduction of numerous active slip sources on the impact face of the crystal.

    Keywords:

    impact, water-drop collisions, fractography, stress waves, deformation, fracture, crystalline materials, magnesium oxide, lithium fluoride, materials, materials science


    Author Information:

    Adler, WF
    Associate manager, Materials Group, and member of the technical staff, Effects Technology, Inc., Santa Barbara, Calif.

    James, TW
    Associate manager, Materials Group, and member of the technical staff, Effects Technology, Inc., Santa Barbara, Calif.


    Paper ID: STP33436S

    Committee/Subcommittee: E08.08

    DOI: 10.1520/STP33436S


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