Release Time:2019-03-12  Hits:

Indexed by: Conference Paper

Date of Publication: 2006-11-22

Included Journals: CPCI-S、EI

Volume: 353-358

Issue: PART 1

Page Number: 138-141

Key Words: room temperature creep; fatigue crack growth; single wave overload; the X70 steel; crack closure

Abstract: Fatigue crack growth (FCG) tests have been performed in an X70 steel with various microstructures (respectively in the as-received and the normalized condition). The effect of room temperature creep (RTC) on FCG behavior has been investigated by comparing with single wave overloads (SWOL). The as-received X70 pipeline steel has high FCG rate at the near-threshold region. While at the Paris region, FCG rate seems insensitive to the microstructure. In both conditions, time-dependent deformation is observed at crack tips (i.e., RTC), which increases with increasing stress-intensity-factor. And this deformation has a high value in the normalized state, under identical testing conditions. Both RTC and SWOL can bring subsequent fatigue crack growth a very short initial acceleration before deceleration, whereas the former induces more serious deceleration and retardation, which attributes to more significant crack closures.