The National Institute for Materials Science (NIMS) has begun operating a testing system and specialized experimental facilities that serve as the foundation for comprehensively evaluating the mechanical properties of structural materials in low-temperature hydrogen environments, including liquefied hydrogen. The objective of this study is to evaluate the mechanical properties of various materials, particularly metallic materials, and to establish a materials database. This will strengthen international competitiveness by expanding the scope of equipment development and reducing manufacturing costs, while ensuring the safety of equipment and materials involved in the production, transportation, storage, and utilization of liquefied hydrogen. This paper provides an overview of the testing system, dedicated experimental facilities, and database established under the Green Innovation Fund Project.

The National Institute for Materials Science (NIMS) has published Structural Materials Data Sheets since 1966. Some data sheets are also available through the online database application “Kinzoku,” which was updated in 2023 with a new unified data model. The Kinzoku data model was constructed by analyzing the implicit structure of long-accumulated data sheets, and by defining entities such as material, piece, properties, and test conditions, as well as their relationships and attributes. Three data formats were implemented based on this model: TSV for daily editing, PostgreSQL for ensuring data integrity and querying, and XML for semantic interoperability. This data model was applied in several scenarios, including an extension of the framework to support liquid hydrogen–related materials data, which is crucial for the development of hydrogen energy infrastructure.

We developed a specialized experimental facility for conducting material-property evaluation tests in liquefied hydrogen-containing cryogenic hydrogen gas. We conducted preliminary surveys of domestic facilities using liquefied hydrogen and those performing material evaluations in cryogenic environments, examining the essential elements and technologies required for a liquefied hydrogen supply facility specialized for mechanical testing. The building houses six explosion-proof laboratories equipped with multiple safety devices. All rooms can supply liquefied hydrogen, hydrogen gas, helium gas, and nitrogen gas. We have also researched and developed dedicated exhaust equipment capable of safely venting hydrogen gas, a combustible gas. Material property evaluations were performed at the specialized facility using liquefied hydrogen stably supplied to the testing equipment, confirming the ability to safely vent hydrogen gas after testing.

In this study, a two-stage pulse tube refrigerator was modeled and numerically analyzed using Sage (Gedeon Associates). In addition, a new measurement system was developed to simultaneously measure the pressure, temperature, and mass flow rate of the working gas under reciprocating flow and extremely low-temperature conditions below 4 K, which had previously been considered technically difficult. This system provides deeper insight into the thermodynamic behavior within the refrigerator. This paper presents a comparison between the experimental results obtained using the developed measurement system and the numerical results calculated with Sage, and reports the evaluated applicability and valid operating range of the pulse tube refrigerator simulation model.