Cryogenic Characterisation of Structural Materials for Liquid Hydrogen Conveyancing Systems

The reliable design and operation of liquid hydrogen (LH2) fuel pumps requires in-depth understanding of the thermomechanical behavior of materials under cryogenic conditions. In particular, within the magnetic rotor assembly, where soft magnetic composites (SMCs) such as Somaloy require full isolation from the cryogenic fluid through a protective structural canning layer. The selection of such functional materials directly influences mechanical loading, thermally induced stresses, and compatibility in an LH2 environment. However, the coefficient of thermal expansion (CTE) data for Somaloy, along with validated CTE data for candidate canning materials remain largely unknown below 100 K. In this work, a CTE measurement approach that incorporates digital image correlation (DIC) with precise temperature control in a custom-built cryostat is developed and validated. The evolution of thermal strain in Somaloy and 316 stainless steel is measured across a wide thermal range, cooling from ambient to