51314-4329-Rapid Fracture Phenomenon of Metals in High Temperature Water

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Product Number: 51314-4329-SG

ISBN: 4329 2014 CP

Author: Xiaoyuan Lou

Publication Date: 2014

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Rapid fracture (or sudden fracture) of various wrought and weld metals in the environment have been observed during compact tension (CT) test in different laboratories. Hydrogen distribution throughout the metal and plastic instability during testing have been proposed as two possible mechanisms that could explain such a sudden or very rapid crack advance. However no data was available to verify these mechanisms. This paper summarizes the findings of the recent EPRI program that was specifically designed to understand this phenomenon in cold-worked stainless steel and alloy 82/182 weld metal. An accelerated testing method for rapid fracture was designed to simulate the inadvertent rapid fracture events observed in the lab. The effects of dissolved H2 and/or O2 concentration stress intensity factor (K) and the change in K on the occurrence of rapid fracture were investigated using CT specimens in high temperature water. Various formulations for limit load analyses were identified and applied to determine if plastic instability was consistent with those experimental observations. The results in this program suggest that plastic instability plays a very important role on the occurrence of rapid fracture. The role of dissolved hydrogen at least under the condition that has been tested in this program is not a big contributor to the phenomenon.