Method for highly spatially resolved determination of residual stress by using nanoindentation

Measurement of highly spatially resolved residual stresses is a crucial task for tailoring the stress state during manufacturing to improve mechanical performance of metallic objects. Especially in sheet metal forming or blanking with sheet thicknesses down to 0.1 mm, a highly resolved pattern of the stress distribution over the sheet thickness is required for optimisation. For this purpose, a method which uses an extended Hertzian theory for calculating residual stresses from the results of nanoindentation is used to measure the stress profile in metallic cylinders. For verification of the indentation results, hole drilling is utilised to determine residual stresses in the near-surface area. This method provides similar assumptions about the stress state (biaxial). The measuring principle is also based on correlations between mechanical behaviour of the material and the residual stress distribution. The results yield a good accordance of the measured values despite the different scales of measurement. Therefore, a highly spatially resolved measurement of residual stresses with nanoindentation is possible and shows comparable values to the classic hole drilling technique.