Fraunhofer Institute for Mechanics of Materials IWM
Fraunhofer Institute for Mechanics of Materials IWM

HyLife: A physics-based tool for predicting the service life of structural materials in contact with hydrogen

Ongoing research project

The HyLife project aims to develop a physics-based service life prediction tool for materials in contact with hydrogen. Innovative test methods and materials models will be used to reliably predict the service life of components under the influence of hydrogen, thereby making a decisive contribution to the safety and efficiency of hydrogen infrastructures.

Project description

The use of hydrogen as an energy carrier of the future requires resilient and durable structural materials, especially for the storage and transport of hydrogen gas. However, many metallic materials are susceptible to hydrogen embrittlement, which can drastically reduce the integrity and service life of components. Currently, components for use under pressurized hydrogen must therefore either be designed very conservatively or undergo time-consuming and costly mechanical fatigue and fracture tests.

HyLife is a joint project of the National Institute of Standards and Technology (NIST) and Fraunhofer IWM. It aims to develop less conservative design guidelines for components operating under pressurized hydrogen. To this end, two approaches are being pursued:

1. Micro sample testing: Micro samples are used to record detailed fracture mechanics materials data from various areas around welded joints, particularly the heat-affected zone (HAZ), in steel samples. The aim is to identify a combination of micro sample experiments that can be used to reliably assess the performance of welded joints in steels under the influence of hydrogen. A central component of the project is a new measuring system that maps the previously difficult to access cohesion at grain boundaries in the microstructure in order to evaluate the condition of the materials in hydrogen.

2. Physics-based service life prediction model: A model is being developed that enables reliable service life predictions based on the microstructure of the materials and a number of physical materials parameters. This model will help to reduce the need for costly fracture mechanics tests and develop new materials with microstructures optimized for hydrogen resistance.

Based on the project results, NIST and Fraunhofer IWM will update the existing ASME B31.12 and ISO 11114-4 standards for materials in hydrogen, which is expected to result in significant cost savings for industry. In addition, a database of commercially relevant materials properties will be established to serve as an easily accessible source of fatigue data. Collaborations with industry ensure that the data and models for materials in contact with hydrogen meet real-world requirements.

Fraunhofer IWM subproject

Fraunhofer IWM's research focuses on the cross-scale determination of damage processes and the development of simulation models for predicting service life:

  • Fracture mechanics of welded joints in steels: Microstructural characterization of selected welds in steel samples (focus: heat-affected zones); fatigue crack growth rate tests and fracture toughness tests in both hydrogen pressurized gas and air on microscale, geometrically optimized, materials-typical steel samples.
  • Measurement of decohesion of mechanically stressed grain boundaries: Production of twin-crystal micro-samples with defined grain misorientation and only one grain boundary; tensile tests in both air and hydrogen gas, including optical imaging of the sample surface for digital image correlation and deformation curve representation.
  • Mapping of grain boundary separation energies and physics-based model for grain boundary decohesion: Use of AI models informed by physical mechanisms to make accurate predictions of functional grain boundary decohesion processes based on sparse micro sample data from the complex, five-dimensional bi-crystallographic space of geometric grain misorientation; parameterization of finite element models for life estimation based on the machine-learned grain boundary energy landscape; evaluation of the models based on their ability to predict real fatigue and fracture processes within welds in reference materials and steels.
  • Development of a service life prediction model: Implementation of a phenomenological model for welded joints in steel materials that predicts their service life under the influence of hydrogen.
  • Collaboration on the further development of norms and standards: Qualification of micro specimens as additional standard specimens for national (DIN) and international standards (ASME, ISO).

Transfer of project results to R&D services provided by Fraunhofer IWM

  • Service life prediction and integrity assessment: Performing tests and simulations to predict the service life and assess the integrity of materials and components in hydrogen operation.
  • Materials optimization: Support in the development and optimization of materials with regard to higher resistance to hydrogen embrittlement.
  • Support in the implementation of and compliance with norms and standards in connection with R&D projects on safe hydrogen infrastructures.