Through thickness non-destructive residual stress-mapping on 6 mm thick Al-plates with neutron diffraction

Speaker:
Pirling, Thilo; Institut Laue-Langevin; France

Authors:
Pirling, T.; Institut Laue-Langevin; France
Cabeza, S.; Institut Laue-Langevin; France
Müller, A.; OHB system; Germany
Windisch, M.; MT aerospace; Germany
Boudou, C.; Institut Laue-Langevin; France

ID: ECNDT-0469-2018
Download: PDF
Session: Aerospace 3
Room: G1
Date: 2018-06-12
Time: 15:40 - 16:00

While x-ray diffraction is widely used to non-destructively screen residual stresses at the surface, deeper investigations are often carried out in a destructive manner. The most popular techniques are the contour method and deep hole drilling. Neutron diffraction offers the unique possibility to map the whole stress tensor in the bulk and near the surface of a given component. Penetration depth reaches for instance: 300 mm in aluminium, 60 mm in steel, 70 mm in titanium and 40mm in nickel at the SALSA instrument of the Laue-Langevin Institute. Thanks to the particular set up of the SALSA instrument, a precise gauge volume is defined. Thus, near-surface measurement is possible at about 40 µm from the surface into the bulk.
Friction stir welding (FSW) is of particular interest for joining of space and aircraft components made from high strength aluminium alloys because it provides high-quality joints with low distortion. We present here an initial work started with OHB-System company regarding friction-stir welds on Al plates. OHB System Company is one of the leading space companies in Europe, delivering satellites and high-tech components for the space sector.
Surface to bulk residual stresses from friction stir welded Al plates of 6 mm thick were investigated. Measurement points were taken starting from about 200 µm below the surface to 3 mm in depth with a 150 µm step (gauge volume of 0.6×0.6×2 mm3). We will show profiles and mapping of residual stress across the weld line and through the plate thickness. High tensile longitudinal stresses at the weld seams were identified. These results will be compared with a study carried out by NASA where use was made of a destructive technique for through thickness measurements (Hatamleh, 2007).