Transients in fatigue crack growth due to a change in. delta. K or R

Journal Article · Mon Dec 01 04:00:00 EST 1986 · Scr. Metall.; (United States)

DOI:https://doi.org/10.1016/0036-9748(86)90288-7· OSTI ID:6986322

McEvily, A J; Yang, Z

The purpose of this paper is to report on transients in the fatigue crack growth rate which occur on change of either the range of the stress intensity factor, ..delta..K, or the R ratio, where R is the ratio of the minimum to the maximum stress in a loading cycle. In this study, the authors have made use of a 9Cr-2Mo ferritic alloy which when fatigue tested in vacuum at 538/sup 0/C exhibits no dependency on R. It is also noted that the crack growth characteristics of 2 1/4 Cr-1 Mo and Modified 9Cr-1Mo steels are quite similar to those of the 9Cr-2Mo steel despite differences in monotonic properties. It is further noted that under these test conditions crack closure was not detectable by a crack-mouth LVDT gauge, and that the absence of closure is consistent with lack of sensitivity to the R level. A final point of interest is that the rate of fatigue crack growth under the stated test conditions is independent of the cyclic frequency in the range of 0.3 Hz to 30 Hz, an indication that creep does not play an important role in the propagation process.

• Research Organization: Metallurgy Dept. and Institute of Materials Science, Univ. of Connecticut, Storrs, CT 06268
• OSTI ID: 6986322
• Journal Information: Scr. Metall.; (United States), Journal Name: Scr. Metall.; (United States) Vol. 20:12; ISSN SCRMB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360103* -- Metals & Alloys-- Mechanical Properties
ALLOYS
CHROMIUM ALLOYS
CHROMIUM STEELS
CHROMIUM-MOLYBDENUM STEELS
CRACK PROPAGATION
CREEP
FATIGUE
FREQUENCY RANGE
HIGH TEMPERATURE
HZ RANGE
IRON ALLOYS
IRON BASE ALLOYS
MECHANICAL PROPERTIES
SENSITIVITY
STEELS
STRESS INTENSITY FACTORS
TRANSIENTS