Fracture mechanics testing, hydrogen

Conventional fracture mechanics testing specimens, such as the compact, cantilever beam, modified bolt-load compact previously referred to as wedge-opening load (WOL), and contoured double-cantilever beam specimens, have been adapted for testing in both aqueous environments and in a high-pressure gaseous hydrogen environment. 

FIG. 14—Fracture mechanics, fatigue precracked specimen geometries for hydrogen embrittiement testing. (Courtesy of Navai Research Laboratory, Washington, DC and LRA Labs, Newport Beach, CA.)... 

In this test, a thin disk of the metallic material is pleiced as a membrane in a test cell and subjected to helium pressure until it bursts. Because helium is inert, the fracture is caused by mechanical overload no secondary physiced or chemical action is involved. An identical disk is placed in the same test cell and subjected to hydrogen pressure until it bursts. MetaUic materials that are susceptible to gaseous hydrogen embrittlement will fracture at a pressure that is lower than the helium burst pressure materials that are not susceptible will fracture at the same pressure for both hydrogen and helium. 

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