The Relationship Between Crack-Tip Strain and Subcritical Cracking Thresholds for Steels in High-Pressure Hydrogen Gas
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TRODUCTION
HYDROGEN reduces the fracture resistance (e.g., promotes subcritical cracking) in most structural metals, as documented over many decades, e.g.[1–9] Implementation of a fracture mechanics-based design qualification approach for hydrogen containment and transport components could greatly enhance life prediction, reducing the probability for catastrophic failures associated with subcritical crack propagation. Reliable and appropriately conservative subcritical cracking thresholds measured under quasi-static loading in high-pressure KEVIN A. NIBUR, Researcher and Owner, is with Hy-Performance Materials Testing, LLC, Bend, OR. Contact e-mail: [email protected] BRIAN P. SOMERDAY, Distinguished Member of Technical Staff, is with Hydrogen and Metallurgy Science Department, Sandia National Laboratories, P.O. Box 969, Livermore, CA 94551, and also with International Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395, Japan. CHRIS SAN MARCHI, Principal Member of Technical Staff, is with Hydrogen and Metallurgy Science Department, Sandia National Laboratories. JAMES W. FOULK, III, Principal Member of Technical Staff, is with Mechanics of Materials Department, Sandia National Laboratories. MOHSEN DADFARNIA, Research Associate, is with the Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, 1206 West Green St., Urbana, Illinois 61801, and also with International Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyusha University. PETROS SOFRONIS, Professor, is with the Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, and also, Director, with International Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyusha University. Manuscript submitted March 5, 2012. Article published online November 7, 2012 248—VOLUME 44A, JANUARY 2013
hydrogen gas are necessary inputs to effective fracture mechanics-based life prediction assessments. As the range of applications and performance requirements for high-pressure hydrogen containment structures expands beyond the current technology space, fracture mechanicsbased design approaches and methods for measuring subcritical cracking thresholds in hydrogen gas become increasingly important to enhance safety. Laboratory test methods for measuring subcritical cracking thresholds in hydrogen gas must properly simulate the in-service mechanical and environmental conditions of components, i.e., the concept of similitude must be considered for both the mechanical and environmental conditions at the crack tip.[10] Mechanical similitude may be maintained through the use of standard fracture mechanics methods designed to measure the linear-elastic stress intensity factor, K, or the elastic-plastic J-integral, J. These fracture mechanics parameters provide a relationship between the continuum crack-tip fields and the remote loading conditions, and this relationship is not a function of the environment, especially for lo
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