Influence of Roughness of Inner Surface of Simple Mechanical Testing Method to Evaluate Influence of High Pressure Hydrogen Gas

In order to standardize the simple testing method to evaluate mechanical properties using hollow-type specimen in the high pressure hydrogen gas, influences of the hole and inner surface roughness on the relative reduction of area (RRA) and other properties in slow strain rate tensile (SSRT) tests were investigated on different surface finished specimens at 105 MPa hydrogen gas for SUS316L and JIS SNCM439 steels. There is no influence of the hole and the inner pressure for the yield strength and the tensile strength. The RRA slightly increased in less roughness specimens. So, the axially polished finish for the hollow specimen will be proposed to the standard testing procedures of the SSRT test with this method to evaluate mechanical properties in the high pressure hydrogen gas.