The Effect of Electric Discharge Machined Notches on the Fracture Toughness of Several Structural Alloys
Abstract
Recent computational studies of the stress and strain fields at the tip of very sharp notches have shown that the stress and strain fields are very weakly dependent on the initial geometry of the notch once the notch has been blunted to a radius that is 6 to 10 times the initial root radius. It follows that if the fracture toughness of a material is sufficiently high so that fracture initiation does not occur in a specimen until the crack-tip opening displacement (CTOD) reaches a value from 6 to 10 times the size of the initial notch tip diameter, then the fracture toughness Will be independent of whether a fatigue crack or a machined notch served as the initial crack. In this experimental program the fracture toughness (JIc and J resistance (J-R) curve, and CTOD) for several structural alloys was measured using specimens with conventional fatigue cracks and with EDM machined notches. The results of this program have shown, in fact, that most structural materials do not achieve initiation CTOD values on the order of 6 to 10 times the radius of even the smallest EDM notch tip presently achievable.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 1993
- Accession Number
- ADA268605
Entities
People
- J. A. Joyce
- R. E. Link
Organizations
- Naval Surface Warfare Center Carderock Division