Publications

Results 326–350 of 413

Search results

Jump to search filters

The relationship between crack-tip strain and subcritical cracking thresholds for steels in high-pressure hydrogen gas

Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science

Nibur, Kevin A.; Somerday, Brian P.; San Marchi, Chris; Foulk, James W.; Dadfarnia, Mohsen; Sofronis, Petros

Threshold stress intensity factors were measured in high-pressure hydrogen gas for a variety of low alloy ferritic steels using both constant crack opening displacement and rising crack opening displacement procedures. Thresholds for crack extension under rising displacement, K THi, for crack extension under constant displacement, KTHi*, and for crack arrest under constant displacement K THa, were identified. These values were not found to be equivalent, i.e. K THi < K THa < K THi*. The hydrogen assisted fracture mechanism was determined to be strain controlled for all of the alloys in this study, and the micromechanics of strain controlled fracture are used to explain the observed disparities between the different threshold measurements. K THa and K THi differ because the strain singularity of a stationary crack is stronger than that of a propagating crack; K THa must be larger than K THi to achieve equivalent crack tip strain at the same distance from the crack tip. Hydrogen interacts with deformation mechanisms, enhancing strain localization and consequently altering both the nucleation and growth stages of strain controlled fracture mechanisms. The timing of load application and hydrogen exposure, i.e., sequential for constant displacement tests and concurrent for rising displacement tests, leads to differences in the strain history relative to the environmental exposure history and promotes the disparity between K THi* and K THi. K THi is the only conservative measurement of fracture threshold among the methods presented here. © 2012 The Minerals, Metals & Materials Society and ASM International.

More Details
TYPE Conference YEAR 2013
ScopusOSTI

Investigation of the hydrogen release incident at the AC Transit Emeryville Facility

San Marchi, Chris

This report summarizes the investigation of the release of approximately 300kg of hydrogen at the AC Transit Facility in Emeryville, CA. The hydrogen release was avoidable in both the root cause and contributing factors. The report highlights the need for communication in all phases of project planning and implementation. Apart from the failed valve, the hydrogen system functioned as designed, venting the hydrogen gas a safe distance above surrounding structures and keeping the subsequent fire away from personnel and equipment. The Emeryville Fire Department responded appropriately given the information provided to the Incident Commander. No injuries or fatalities resulted from the incident.

More Details
TYPE SAND Report YEAR 2012
DOIOSTIDOIOSTI
Results 326–350 of 413
Results 326–350 of 413
Top