The importance of residual stresses on the performance of metallic components
Metallic structures are the backbone in a wide range of industrial sectors e.g. energy, space, aerospace and automotive. Metals are, however, not utilised optimally since over dimensioning by conservative safety factors are used to mitigate the effect of detrimental residual stresses known to cause failure by e.g. fatigue fracture. Knowing the actual stress levels and incorporating these into modelling tools will lead to three competitive advantages for companies:
- Increased lifetime and reduced risk of failure
- Reduced material usage due to reduced safety factors
- Reduced time-to-market of new products, materials, and processing technologies
Bulk non-destructive characterization of the full 3D stress tensor using synchrotron x-ray and neutron diffraction
Residual stresses are typically measured using (semi)destructive techniques, such as hole-drilling or contour mapping, where some material is removed from the component causing the residual stresses to redistribute. The subsequent deformation is measured from which the stress levels of the removed material can be calculated. Alternatively, laboratory x-ray diffraction setups can be used to measure the residual stresses at the surface of components. These techniques are all limited in the depth and residual stress directions that can be probed.
The EASI-STRESS project will help European industry to finally understand and handle challenges related to residual stress. Stresses are the ‘known unknown’ factor when designing metallic components: everybody knows they are there but have been lacking tools to address them
- Nikolaj Zangenberg, Project Coordinator
Using synchrotron x-ray and neutron diffraction-based techniques, the full 3D stress tensor can be measured within the bulk of a component in a non-destructive manner which is not possible with any other technique. Depending on the exact technique the spatial resolution can additionally be significantly higher than for the destructive methods.
Barriers for performing residual stress characterization at large scale facilities
Despite the unique capabilities of these techniques, and the fact that they have been used for decades in academia, they have not yet gained foothold in industry because of a lack of validation, standards and procedures. This is the rigor-relevance gap that EASI-STRESS is in the process of bridging.
Breaking down the barriers through targeted actions
Within the framework of the EASI-STRESS project, the consortium, consisting of large industrial partners and experts from the large facilities and universities bound together by RTOs and a standardisation body, break down the main barriers for industrial use of these strong techniques by
- Validating the techniques and their accuracy against more widespread (semi)destructive measurement techniques and numerical modelling tools.
- Developing and implementing protocols and procedures aimed at standardisation for the measurements, in close collaboration with both standardisation bodies and industrial partners to ensure their industrial acceptance.
- Defining (meta)data formats and software that ensure reproducibility and traceability of the data and enable their incorporation into modelling tools to secure the link between data and reliable end-product.
- Setting up and validating an industrial test bed service for residual stress characterisation to ensure that all European industries can get a head start on the technology, part of which is based at DTI in Denmark.
This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 953219
Budget: EUR 4.5 million
Timeframe: January 1st 2021 – June 30th 2024