STP664

    Response of Infrared Transmitting Materials to High-Velocity Impact by Water Drops

    Published: Jan 1979


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    Abstract

    An experimental and analytical program was performed to investigate the response of zinc selenide, zinc sulfide, and gallium arsenide to water drop impact. The experiments consisted of single-drop impact (0.7, 2.0, and 2.5-mm-diameter drops and impact velocities of 222 and 341 m/s); overlapping drop impacts (2.0-mm drops at 222 m/s); and exposure at 222 m/s to the standard rainfield (1.8-mm drops, 2.54-cm/h rainfall rate). An analytical model was used to compute stresses induced in the materials by a single water drop impact.

    Within the conditions tested, each single-drop impact produced a ring fracture pattern characteristic of the material. Resistance to damage increased in the order zinc selenide, gallium arsenide, and zinc sulfide. The superior performance of zinc sulfide with respect to zinc selenide is attributed to the order-of-magnitude smaller grain size of zinc sulfide. Comparison with experimental results showed the analytical model to be a reasonable representation of the drop impact process.

    The rainfield test of zinc sulfide showed that transmittance loss at short wavelengths (0.5 to 2.1 μm) was linear with exposure time, indicating a dependence on the extent of subsurface damage. At wavelengths above 2.5 μm, there was an incubation period before loss of transmittance. The end of the incubation period and the start of transmittance loss were associated with the nucleation of surface pits.

    Keywords:

    rain erosion, infrared window materials, single-drop impact, stress waves, erosion mechanisms, multiple-drop impact, erosion


    Author Information:

    Hackworth, JV
    Principal scientist, chief, Structural Analysis, and principal scientist, Bell Aerospace Textron, Buffalo, N. Y.

    Kocher, LH
    Principal scientist, chief, Structural Analysis, and principal scientist, Bell Aerospace Textron, Buffalo, N. Y.

    Snell, IC
    Principal scientist, chief, Structural Analysis, and principal scientist, Bell Aerospace Textron, Buffalo, N. Y.


    Paper ID: STP35804S

    Committee/Subcommittee: G02.10

    DOI: 10.1520/STP35804S


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