Accession Number:

AD0700174

Title:

A SYSTEMATIC STUDY OF FATIGUE MECHANISMS IN IRON.

Descriptive Note:

Interim technical rept.,

Corporate Author:

COLUMBIA UNIV NEW YORK HENRY KRUMB SCHOOL OF MINES

Personal Author(s):

• Dalal,Hormazdyar Minocher

Report Date:

1969-05-01

Pagination or Media Count:

74.0

Abstract:

Monocrystals and polycrystals of Ferrovac E iron were subjected to pull-release fatigue cycles of constant load amplitudes. Luders band velocity was measured under cyclic stress conditions. Cyclic creep measurements were done at low temperatures. At low stress amplitudes, the cyclic creep rate could be made to vanish by stress cycling. At this stage the applied stress amplitude equals the internal stress, so the effective stress could be determined. It has been shown that the mobile dislocation density remains constant throughout the fatigue life of a specimen. On the basis of dislocation dynamics, a cyclic strain rate equation has been derived and experimentally verified. The characteristic rapid and saturation hardening stages have been shown to be a result of the dislocation multiplication rate obeying a first order kinetics in multiplication and a second order kinetics in dynamic recovery. Author

Descriptors:

• (*IRON
• *FATIGUE(MECHANICS))
• DISLOCATIONS
• CREEP
• STRESSES
• THESES

Subject Categories:

• Metallurgy and Metallography
• Solid State Physics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE