Date

1970

Document Type

Thesis

Degree

Master of Science

Department

Applied Mechanics

First Adviser

Paris, Paul C.

Abstract

Three possible mechanisms for non-propagating cracks were proposed with one being at least partially eliminated when a test run in dry argon on Ti-6Al-4V produced little or no change in the threshold compared to that in air. WOL type compact tension specimens of 9310 steel, 4340 steel, and Ti-6Al-4V were cyclically loaded at frequencies up to 200 cps for long periods of time to obtain extremely slow crack propagaion data down to 5 x 10-9 inches per cycle. Fracture mechanics was used to analyze the data in terms of K, the alternating stress intensity parameter, and da/dn, the fatigue crack growth rate.

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