Stable crack growth estimates based on effective crack length and crack-opening displacements
A method was developed for estimating the amount of stable crack growth that has occurred in a fracture toughness specimen that were loaded into the plastic range and for which only a monotonically increasing load-displacement curve was measured. The method was applied to data from several pressure vessel steels. The resulting J vs ..delta..a values compare favorably with a resistance curve obtained by the multiple specimen heat-tinting technique for A533, Grade B, Class 1 steel. The method for estimating stable crack growth uses several existing concepts heretofore mainly used separately. These concepts include an approximate expression for J for the compact specimen proposed by Andrews, the effective crack length concept of McCabe and Landes, the UK representation of the crack profile as a pair of straight lines intersecting at a hinge point, and Well's expression, J = m sigma/sub y/delta, for relating the crack-opening displacement to the value of J. The value of the constraint factor, m, at the advancing crack tip is estimated by means of a relation between ductility and fracture toughness. When calculated with respect to the COD at the original fatigue crack tip, the constraint factor, m/sub o/, is found to have a value consistently close to 2.0 for compact and precracked Charpy specimens. The method of estimation requires no auxiliary load-deflection measurements or calculations, and so permits single specimen estimates of stable crack growth to be made without the necessity of making high precision unloading compliance measurements.
- Research Organization:
- Oak Ridge National Lab., TN (USA); Auburn Univ., AL (USA)
- DOE Contract Number:
- W-7405-ENG-26
- OSTI ID:
- 5880573
- Report Number(s):
- CONF-790963-1
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
220200 -- Nuclear Reactor Technology-- Components & Accessories
36 MATERIALS SCIENCE
360103* -- Metals & Alloys-- Mechanical Properties
ALLOYS
CARBON STEELS
CHARPY TEST
CONTAINERS
CRACKS
DUCTILITY
EQUATIONS
FATIGUE
FRACTURE PROPERTIES
IRON ALLOYS
IRON BASE ALLOYS
JOINTS
MATHEMATICAL MODELS
MECHANICAL PROPERTIES
MIGRATION LENGTH
PRESSURE VESSELS
STEEL-ASTM-A508
STEEL-ASTM-A533-B
STEELS
TENSILE PROPERTIES
WELDED JOINTS