The Advanced Manufacturing Research Centre (AMRC), with Boeing, at the University of Sheffield have been using Engin-X at ISIS to study the evolution of residual stresses in AA7050 – an aluminium alloy commonly used in aerospace structures - as it is heated and then machined. This understanding will enable them to reduce non-conformance in the manufacturing process, and significantly reduce costs.
Residual stresses in components are an inevitable result of metal processing and are uncovered during machining. It can cause distortion in components meaning they are not fit for purpose, reduce component lifetime, and require costly operator skill to identify and intervene in the machining process when distortion occurs. Understanding the way in which various processes induce residual stress is key to optimising those processes, increasing conformance and reducing cost.
The AMRC with Boeing worked to develop a way of analysing residual stress using the Engin-X instrument at ISIS. The team looked at blocks of AA7050 after heat treatment and quenching then subjected to different machining strategies. Alongside their experiments at ISIS the team developed 3D Finite Element Modelling to predict the residual stress resulting from quenching and machining and measuring the distortion. The combination of modelling, measurement and experiment allowed them to gain a clear understanding of how distortion occurs in the different manufacturing processes.
The role of ISIS
Engin-X allowed the team to map residual stresses in three dimensions and build up residual stress profiles resulting from quenching and machining processes. Neutron’s unique ability to probe beneath the surface of metal components was key to establishing the links between residual stress on the atomic scale and distortion on the macroscopic scale. This capability allowed the team to see the hidden residual stresses prior to releasing them during the machining process which is unachievable by other means.
Research date: August 2014
For further information please contact Sara Fletcher