The researchers of the ELKH Centre for Energy Research (ELKH CER) have won an EU H2020 project proposal to promote innovation in Hungary. The CER staff of the Neutron Spectroscopy Department received the nearly EUR 350,000 three-year project grant for the development and introduction of a new industrial testing standard for non-destructive materials. The EASI-STRESS project involves four major European research infrastructures (RIs), one university, two technology transfer companies and seven top industrial enterprises as partners. Four of the latter also have significant industry involvements in Hungary. Subsidiaries of well-known companies such as Airbus, Rolls-Royce and Siemens, EDF (a French nuclear power plant manufacturer), NEMAK (a foundry giant with an automotive supplier factory in Győr, for example), the world’s largest steel producer (Acelor-Mittal) and a 3D metal-printing company (Volum-E) are involved in the work.
One of the research infrastructures participating in the EASI-STRESS project is the Budapest Research Reactor, which operates at the ELKH-CER Csillebérc campus. On the left is the 10-megawatt nuclear reactor building complex, on the right is the reactor core-block and around it a suite of BNC’s neutron diffraction equipment.
The aim of the project is non-destructive X-ray and neutron diffraction analysis of internal residual stresses in materials/components, strengthening the dissemination of the measurement method and tools, and developing new standards in close cooperation with industry. This technique allows a better understanding of the formation of internal residual stresses during the manufacture of various devices and to predict the in-use variation of stresses, and as a result the possible life-time and reliability of the products. In this way, comparing and incorporating directly the measured data into existing industrial design and modelling tools will enable us to produce better products. With the introduction of this method at an industry level, manufacturers will be able to detect defects in the production of components such as the formation of cracks due to poor welds or bending at the wrong speed and temperature. Additionally, as a quality assurance procedure, it will also be possible to identify materials that fatigue due to environmental influences during the use of objects, and potentially increase service life as a result.
The essence of the method is the following: the parameters of the manufacturing processes greatly influence the material structure. For example, in castings, the rate of solidification affects the position of the atoms in the alloy materials, and if the ideal crystal structure is not formed, an ‘internal stress remains’ within the material. By X-ray diffraction on the surface of the components, while with neutrons in the bulk of the materials we can ‘see’ the atomic level microstructure and the internal stress value and distribution can be calculated from the diffraction patterns.
BNC staff have significant experience in neutron diffraction stress analysis – this is why they have been invited to this EU project. The image on the left shows the sample table of one of the BNC’s spectrometers, where the microstructure of a gas turbine wheel is being tested. On the right is an experimental set-up with a bending device for the sample in the neutron beam, thus enabling in-situ stress generation during the neutron diffraction measurements.
In the modern production of machine parts, heat treatment and shaping by mechanical deformation are often used simultaneously. For example, in the case of multicomponent alloys, the metallurgical or phase composition in the object, including the residual stresses, depends on the processes used. In engineering design, large software packages have been developed to model such processes, the experimental validation of which is a prerequisite for the introduction of design results into production. Diffraction stress analysis is one of the most efficient non-destructive experimental methods, which means that the standardization of such measurement procedures would allow for industry-wide application. Incorporating this knowledge tool into the design process of metallic parts will result in reduced material consumption and more reliable and longer-lasting products, which would also mean significant environment and cost savings.
In the project, the industrial companies will define and produce test samples according to their profile, and also providing real components for the experiments. Diffraction measurements are to be performed by RIs, X-ray examinations at the two largest European synchrotron sources (ESRF-Grenoble, HZG-Hamburg), neutron experiments at the world’s largest neutron research facility (ILL-Grenoble) and at the Budapest Neutron Centre (BNC) as the largest Hungarian research infrastructure, a unit of the ELKH-CER. The University of Manchester, as well as the Danish and French tech-transfer companies (DTI, CETIM), will ensure the coordination of modelling and validation, while they will also be responsible for introducing the procedure as a European standard.