Flow and Fracture Properties of Aluminum Alloys Potentially Useful for Small Arms Cartridge Cases.
MATERIALS RESEARCH LAB INC GLENWOOD ILL
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The most useful laboratory measure for evaluating fracture resistance is the fracture toughness which must also be measured at the rates and temperatures that simulate service. Since cartridge case materials are very thin, fracturing occurs under a condition of plane stress rather than plane strain. Measurements of dynamic yield strength have been made by numerous investigators. Dynamic measurements of plane stress fracture toughness, on the other hand, have not been made prior to this program. Consequently, it was necessary to develop a method for measuring this property on thin sheets in a fashion such that dynamic loading would be possible. Tensile and fracture toughness tests of each material were made at rise times time required to increase the load from zero to its critical value. The critical value of load was the 0.2 percent offset yield stress for tensile testing, and the plateau or equilibrium value of the critical stress intensity factor for toughness testing. All of the alloys were tested in the longitudinal and the long transverse direction, and early in the program tests were also made for each rate and direction at test temperatures of -70, 70 and 165F.
- Metallurgy and Metallography