Fracture Extension Resistance (R-Curve) Features of Nonfrangible Aluminum Alloys.
NAVAL RESEARCH LAB WASHINGTON D C
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New procedures were evolved to characterize the fracture extension resistance of nonfrangible structural aluminum alloys. Fracture extension resistance is a result of the increase in plastic work energy required to propagate a crack. The resistance parameter is defined as the R-curve slope of the metal. Characteristic R-curve features are presented for aluminum alloys ranging from frangible to high fracture toughness types. The R-curve slope determines the plastic work energy expended for fracture extension in structures, as confirmed by Explosion Tear Test results. The R curves are defined by using the Dynamic Tear test specimen in two configurations involving a short and standard fracture extension length. Indexing the R-curve slopes to the Ratio Analysis Diagram RAD for aluminum provides a definition of the capabilities of the metal for use in structures of low, intermediate, and high compliance features. This integration of structural aspects with the mechanical and metallurgical aspects of the RAD should significantly advance the generalized fracture-safe design of aluminum structures using nonfrangible alloys. Author
- Metallurgy and Metallography