Influence of viscous environments on fatique crack propagation in a lower strength steel
The effect of dehumidified silicone and paraffin oils with viscosities from 5 to 60,000 centistokes (cS) on fatigue crack propagation in a lower strength 2 1/4Cr-1Mo pressure vessel steel (ASTM A542 Class 3) was studied at both near-threshold (less than or equal to 10/sup -6/ mm/cycle) and higher (approx. 10/sup -6/ to 10/sup -3/ mm/cycle) growth rates. It is found that, at low load ratios, crack growth rates in oils are lower than in moist air and dry hydrogen and increase in increasing oil viscosity in higher growth rate region. However, at near-threshold levels, crack growth rates in oils are considerably higher than in moist air and are not affected by the viscosity of oil. At high load ratios, although crack propagation in oils is slower in higher growth rate region and unchanged at near-threshold levels when compared to that in moist air, no effect of oil viscosity can be observed. Such observations are discussed and quantitatively analyzed in terms of three mutually competitive mechanisms specific to dry viscous environments, namely suppression of moisture-induced hydrogen embrittlement and/or metal dissolution, minimization of oxide-induced crack closure and hydrodynamic wedging effects of the viscous fluid within the crack.
- Research Organization:
- Lawrence Berkeley Lab., CA (USA)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 5219415
- Report Number(s):
- LBL-16262; ON: DE84008247
- Resource Relation:
- Other Information: Portions are illegible in microfiche products. Thesis
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CHROMIUM-MOLYBDENUM STEELS
FATIGUE
CRACK PROPAGATION
HYDROGEN EMBRITTLEMENT
OILS
SILICONES
ALLOYS
CHROMIUM ALLOYS
CHROMIUM STEELS
EMBRITTLEMENT
IRON ALLOYS
IRON BASE ALLOYS
MECHANICAL PROPERTIES
ORGANIC COMPOUNDS
OTHER ORGANIC COMPOUNDS
POLYMERS
SILOXANES
STEELS
360103* - Metals & Alloys- Mechanical Properties