Measuring residual stresses in automotive components with complex geometries using neutron diffraction

Important results from the project

The goal of the project was to demonstrate through two relevant case studies how neutron diffraction can be used to measure residual stresses in vehicle components with complex geometry. The case studies consisted of a welded aluminum structure and a crankshaft with internal lubrication channels. The residual stresses in critical points in these structures were not possible to measure with conventional methods, but through the project the stress gradients in all sought points could be obtained.

Expected long term effects

The data obtained will be used by Volvo Trucks Technology in further internal development work. The project has clearly demonstrated that large-scale infrastructure has potential to address otherwise impossible technical challenges with direct relevance to ongoing industrial development work, and thus constitutes a complementary tool for Volvo in case of any future needs.

Approach and implementation

Diffraction measurements were done at the SALSA instrument at ILL in Grenoble, which allows the definition of a cubic measurement volume of the order of 1 mm3. Three orientations were measured, to enable the calculation of all three principal stresses. In order to obtain near-surface stress gradients with spatial resolution smaller than the measurement volume, correction of "pseudo-stresses", which arise when the measurement volume is not completely inside the sample, was necessary.