Tuesday  |  Frick  |  09:40 AM–10:00 AM

#13853, Macro Residual Stress Analyses on Textured Multi-Phase Stainless Steel Sheets after Deep Rolling - Incremental Hole Drilling vs. X-Ray Diffraction

The determination of local residual stress depth distributions on sheet metal components poses a variety of challenges to all known experimental analysis methods. The incremental hole drilling method, for example, as the most widespread representative of the mechanical methods, requires a minimum component thickness for the use of the standardized evaluation method. In case the component thickness is below this minimum, elaborate case-specific calibration data must be applied instead of the generalized calibration data. Furthermore, it should be noted that if the material has a pronounced crystallographic texture, which is often the case for rolled sheet metals, this must also be taken into account in the data evaluation. Mechanical surface treatments often induce high residual stresses close to the yield point. When applying the incremental hole drilling method, it should be noted that the evaluated residual stresses can be significantly overestimated due to the occurring plasticity effect.
In contrast, the determination of macro residual stresses by means of diffraction methods requires the phase-specific residual stress analysis of all existing phases. Furthermore, the determination of residual stress depth distribution requires successive layer removal in combination with reapplication of the method. Considering thin sheet metals, stress redistributions due to the layer removal must be taken into account. For textured materials, the well-known sin²psi-method might no longer be suitable and special methods must be applied for stress evaluation, such as the crystallite group method or the application of stress factors.
In the work presented here, it is to be investigated for textured duplex stainless steel sheets that have been mechanically surface-treated by deep rolling, to what extent the incremental hole drilling method is an alternative method to determine reliable macro residual stress depth distributions with significantly less measurement and evaluation effort in contrast to X-ray diffraction analyses.
In this systematic study, the residual stress depth gradient of 1.5 mm thick cold-rolled sheet samples of duplex stainless steel X2CrNiN23-4 is investigated after deep rolling using two different process parameter sets (variation in deep rolling pressure) and the results are discussed in comparison with equally treated single-phase (X6Cr17) stainless steel samples.

Nicola Simon   Karlsruhe Institute of Technology
Monja Wolf   Karlsruhe Institute of Technology
Jens Gibmeier   Karlsruhe Institute of Technology