Fracture Extension Resistance (R-Curve) Concepts for Fracture-Safe Design with Nonfrangible Titanium Alloys.

摘要

New procedures were evolved to characterize the fracture extension resistance of nonfrangible structural titanium alloys. Fracture extension resistance is defined by the increase in plastic work energy required to propagate a crack. The resistance parameter is the R-curve slope of the metal. Characteristic R-curve features are presented for titanium 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 the use of the Dynamic Tear test specimen. Indexing the R-curve slopes to the Ratio Analysis Diagram (RAD) for titanium provides definition of the metal capabilities 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 provide for significant advances in generalized fracture-safe design of titanium structures rising nonfrangible alloys. (Author)