Dynamic fracture toughness evaluation by measurement of CTOD

Technical Report · Mon Feb 01 04:00:00 EST 1988

OSTI ID:6911123

Sharpe, Jr, W N; Douglas, A S; Shapiro, J M

Quantification of the dynamic fracture toughness of structural materials is essential to a wide range of problems-from nuclear accidents to ordnance applications. However, the difficulties associated with accurate measurements of crack under dynamic loading are considerable. Thus there are no standardized procedures and few reliable results. A systematic study of the dynamic fracture toughness of SAE-01 tool steel, 4340 and HY100 steels, and a tungsten are described using the Interferometric Strain/Displacement Gage (ISDG) system which has very high frequency resolution. The ISDG system is used to measure the crack tip opening displacement (CTOD) 100 microns behind a fatigue crack tip in a three-point bend specimen. Static measurements on similar specimens serve to calibrate the method and ensure consistency with the accepted procedures for static fracture toughness testing. Finite element analyses are used to obtain full field information at the point of initiation and to assess the material characteristics which lead to changes in toughness with loading rate. The major advantage of the method is that information is obtained very close to the crack tip, so that stress wave loading effects are accounted for. Results show that 4340 steel, which is strain-rate insensitive, has no significant change in toughness with loading rate. Measurable toughness dependence on loading rate is found for HY-100 and tungsten, which are approximately 15 percent tougher under dynamic conditions. The SAE-01 tool steel shows a significant increase (50 percent) in fracture toughness for dynamic over static loading.

• Research Organization: Johns Hopkins Univ., Baltimore, MD (USA)
• OSTI ID: 6911123
• Report Number(s): WNS/ASD-88-02
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360103* -- Metals & Alloys-- Mechanical Properties
440300 -- Miscellaneous Instruments-- (-1989)
47 OTHER INSTRUMENTATION
ALLOYS
CRACK PROPAGATION
DATA
ELEMENTS
EXPERIMENTAL DATA
FINITE ELEMENT METHOD
FRACTURE PROPERTIES
INFORMATION
IRON ALLOYS
IRON BASE ALLOYS
MATHEMATICAL MODELS
MEASURING INSTRUMENTS
MEASURING METHODS
MECHANICAL PROPERTIES
METALS
NUMERICAL DATA
NUMERICAL SOLUTION
STEELS
STRAIN GAGES
TRANSITION ELEMENTS
TUNGSTEN