Hydrogen embrittlement bend tests

Fig. 8.102 Constant-rate bend test for determining hydrogen embrittlement of wires. A, drive unit B, pulley C, semicircular base D, travelling arm E, axial pin F, fixed arm C, wire specimen (after Zapffe and Haslem )...

A field cold bend may be made to a shorter minimum radius than permitted in (a)(2) above, provided the completed bend meets all other requirements of this section and the wall thickness after bending is not less than the minimum permitted by para. PL-3.7.1(a). This may be demonstrated through appropriate testing. Note that cold bending may make line pipe more susceptible to the effects of hydrogen embrittlement. 

FIG. 19—Comparison of single-edge-notched bend cantilever beam and wedge-opening load test results for hydrogen embrittlement threshold of ironHiickel-cobalt steels [28],... 

After test exposure, sample evaluation for hydrogen may include tensile, notched tensile, bend, ductility (for example, drawn cup), and/or impact Charpy tests, hydrogen analysis, or cross-sectional microstructural examination, or a combination thereof. Uniaxial, smooth-specimen tension testing is generally of litde value in diagnosing the subde embrittling effects of hydrogen. Titanium alloys tend to... 

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