A micro-scale strain rosette for residual stress measurement by SEM Moire method

In this paper, a new method combining focused ion beam (FIB) and scanning electron microscope (SEM) Moir, technique for the measurement of residual stress at micro scale is proposed. The FIB is employed to introduce stress relief like the macro ring-core method and fabricate gratings with a frequency of 5000 lines/mm on the measured area of the sample surface. Three groups of gratings in different radial directions are manufactured in order to form a micro-scale strain rosette. After milling ring-core by FIB, the deformation incurred by relief of the stress will be recorded with the strain rosette. The displacement/strain field can be measured using SEM scanning Moir, with random phase-shifting algorithm. In this study, the Nickel alloy GH4169 sample (which was processed by laser shock peening) is selected as a study object to determine its residual stress. The results showed that the components of the in-plane principal stresses were -359 MPa and -207 MPa, respectively, which show good agreement with the results obtained from the available literature.