Results of nanoindentation test to calculate residual stress in an eyelet of undercarriage drag strut after laser treatment

In order to determine the residual stress in the laser-processed an eyelet of undercarriage drag strut, a nanoindentation test was performed before and after stress relief annealing. For this purpose, after the hardness test, the sample was subjected to stress relief annealing at 270 °C for 2 hours. Annealing was performed in a vacuum furnace. Hardness test was performed again after annealing, near the same measurement points as before annealing. Residual stresses were calculated as the difference between the penetrator load for the sample with and without stress before and after annealing respectively, at the same depth of penetrator displacement. During the hardness tests, portion of elastic work was also determined as an area under the unloading curve.