Journal Published Online: 01 January 1991
Volume 19, Issue 1

Charpy Impact Tests Near Absolute Zero

CODEN: JTEVAB

Abstract

We review Charpy impact testing at extreme cryogenic temperatures, especially at liquid helium temperature (4 K), considering methods of testing and calibration, thermal behavior during the various stages of testing, and correlations between Charpy absorbed energy and quantitative toughness parameters. Because of the very low specific heats of metals near absolute zero, any surface condensation of gases, convective or conductive heat transfer, or plastic deformation during a test will cause the specimen temperature to rise rapidly. Consequently, valid impact tests of alloys at 4 K can not be performed according to the procedure outlined in ASTM Methods E 23-88. During Charpy tests, the temperature of austenitic steel specimens, initially at or near 4 K, may in fact rise outside the cryogenic regime. Fracture does not occur at the intended temperature, but at an uncontrolled temperature, since materials with different work hardening rates heat differently. In view of the temperature rise variability and scatter in measurements and property correlations, we conclude that it is not possible to accurately estimate the 4 K fracture toughness of ductile steels, or rank them properly, using Charpy tests.

Author Information

Tobler, RL
National Institute of Science and Technology, Materials Reliability Division, Boulder, CO
Reed, RP
National Institute of Science and Technology, Materials Reliability Division, Boulder, CO
Hwang, IS
Massachusetts Institute of Technology, Cambridge, MA
Morra, MM
Massachusetts Institute of Technology, Cambridge, MA
Ballinger, RG
Massachusetts Institute of Technology, Cambridge, MA
Nakajima, H
Superconducting Magnet Laboratory, Division of Thermonuclear Fusion Research, Naka Fusion Research Establishment, Japan Atomic Energy Research Institute, Ibaraki, Japan
Shimamoto, S
Superconducting Magnet Laboratory, Division of Thermonuclear Fusion Research, Naka Fusion Research Establishment, Japan Atomic Energy Research Institute, Ibaraki, Japan
Pages: 7
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Stock #: JTE12527J
ISSN: 0090-3973
DOI: 10.1520/JTE12527J