ISO 6892-4

Description / Abstract: This part of ISO 6892 s pecifies t he m ethod o f t ensile t esting o f m etallic m aterials i n l iquid h elium (the boiling point is –269 °C or 4,2 K, designated as 4 K) and defines the mechanical properties that can be determined.

This part of ISO 6892 may apply also to tensile testing at cryogenic temperatures (less than –196 °C or 77 K), which requires special apparatus, smaller test pieces, and concern for serrated yielding, adiabatic heating, and strain-rate effects.

To conduct a tensile test according to this part of ISO 6892 at 4 K, the test piece installed in a cryostat is fully submerged in liquid helium (He) and tested using displacement control at a nominal strain rate of 10−³ s−1 or less.

NOTE The boiling point of the rare 3He isotope is 3,2 K. Usually, the tests are performed in 4He or a mixture of 3He and ⁴He with a high concentration of 4He. Therefore, the temperature is, as designated before, 4 K.