The effect of electric discharge machined notches on the fracture toughness of several structural alloys

Technical Report · Wed Sep 01 04:00:00 EDT 1993

DOI:https://doi.org/10.2172/10187626· OSTI ID:10187626

Joyce, J A ^[1]; Link, R E ^[2]

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1. Naval Academy, Annapolis, MD (United States)
2. Naval Surface Warfare Center, Annapolis, MD (United States)

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 (J{sub Ic} and J resistance (J-R) curve, and CTOD) for several structure 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. It is found furthermore that tougher materials do not seem to be less dependent on the type of notch tip present. Some materials are shown to be much more dependent on the type of notch tip used, but no simple pattern is found that relates this observed dependence to the material strength toughness, or strain hardening rate.

• Research Organization: Nuclear Regulatory Commission, Washington, DC (United States). Div. of Engineering; Naval Academy, Annapolis, MD (United States); Naval Surface Warfare Center, Annapolis, MD (United States)
• Sponsoring Organization: Nuclear Regulatory Commission, Washington, DC (United States)
• OSTI ID: 10187626
• Report Number(s): NUREG/CR--5981; CDNSWC/SSM--61-93/01; ON: TI94000617
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360103
ALUMINIUM ALLOYS
ELASTICITY
ELECTRIC DISCHARGES
EXPERIMENTAL DATA
FATIGUE
FRACTURE MECHANICS
FRACTURE PROPERTIES
MAGNESIUM ALLOYS
MATERIALS TESTING
MECHANICAL PROPERTIES
MOLYBDENUM ALLOYS
NOTCHES
PLASTICITY
SAMPLE PREPARATION
STAINLESS STEEL-302
STEEL-ASTM-A302
STEEL-ASTM-A533-B
STEELS
STRAINS
STRESSES