Accession Number:

ADA099194

Title:

Fracture Kinetics of Hydrogen Embrittled Niobium.

Descriptive Note:

Technical rept.,

Corporate Author:

ILLINOIS UNIV AT URBANA DEPT OF METALLURGY AND MINING ENGINEERING

Personal Author(s):

Report Date:

1981-03-01

Pagination or Media Count:

176.0

Abstract:

Kinetics of crack propagation in hydrogen charged niobium were studied in the temperature range 77 to 303 K and for hydrogen concentrations between 0.068 and 3.2 at.. Crack velocities between 10 to the -8th power and .01 ms were determined as a function of the Mode I stress intensity factors using single edge notch and double torsion specimens. Validity of the double torsion technique was established using a variety of methods including photoelastic analysis of the stresses in the plane normal to the specimens crack surface. Increasing, decreasing and constant KI tests were carried out and the 1nV versus KI data exhibited various behavior depending upon the type of loading. Linking up of fracturing hydrides was shown to be responsible for a unique three region V-K behavior which occurred only at intermediate temperatures for decreasing KI tests. Analysis of the temperature dependence for Stage II during constant KI tests indicated that the cracking kinetics are controlled by hydrogen diffusion to the crack tip. Differences between crack velocities in deuterium and hydrogen charged specimens were consistent with the isotopic differences in their diffusion coefficients. Fracture surfaces of the test specimens were examined and shown to exhibit features consistent with their crack velocity behavior. Author

Subject Categories:

  • Metallurgy and Metallography
  • Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE