Studies of Rain Erosion Mechanisms in a Range of IR Transmitting Ceramics Including Coated Samples
Abstract
This report contains recent results on zinc sulfides and other infrared transparent window systems. Section 1 describes an investigation into the stress corrosion characteristics of zinc sulfides using the double torsion geometry. The results suggest that zinc sulfides is susceptible to moisture enhanced slow crack growth but to a lesser extent than, for instance soda lime glasses. Section 2 discusses the correct experimental procedure for the Brazilian test and then uses this geometry to determine the variation of both zinc sulfides and germanium fracture stress as a function of temperature. The average fracture stress fluctuates (as does the associated error) but remain above the room temperature value within the temperature range -70 C to 600 C. Section 3 contains results from the bursting disc test performed on large (125mm diameter by 5.45mm) zinc sulfides windows rather than small (25mm or 50mm diameter) test pieces. The agreement between the results for the small and large scale samples suggests that the small samples give a good representation of the strength of a full size window and that the surface finish achieved on the small discs can be reproduced in the larger discs. Some results from the Multiple Impact Jet Apparatus (MIJA) are given in Section 4, describing the derivation of the threshold velocity for a GeC coated zinc sulfides system. The improvement in threshold velocity over that of the uncoated substrate is marginal.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 1991
- Accession Number
- ADA245299
Entities
People
- John Edwin Field
Organizations
- University of Cambridge