Benchmark measurement of residual stresses in a 7449 aluminium alloy using deep-hole and incremental centre-hole drilling methods

Residual stress measurements using non-destructive techniques including neutron diffraction and X-ray diffraction are dependent on assumptions made in the analysis. For example, the different stress free reference sample and the presence of precipitates in a material can influence the measured results. Previous residual stress measurement using neutron diffraction technique in a quenched aluminium block revealed that the result can be influenced by the choice of the stress free reference sample. A benchmark method is therefore essential to validate the different measurement techniques. In this paper, the deep-hole drilling technique was used first as a benchmark technique to validate (1) the measured residual stresses in a water quenched 7449 aluminium alloy block using the neutron diffraction technique, and (2) residual stresses measured using the layer removal technique in a 7449 aluminium plate which was water quenched followed by stretching. Second, the incremental centre-hole drilling technique was used to validate the near surface residual stresses in an aluminium strip measured using the X-ray diffraction technique. The excellent correlations with the benchmark measurement methods validated the different results.