The endurance limit of bolted high strength steel assemblies is extremely sensitive to the surface condition and the residual stress state. In this work package, the influence of the hole making process (drilling, punching, cutting, …) on the fatigue performance of high strength steels is investigated. For selected samples, the surface roughness will be analysed with a profilometer. Metallographic cross-sections and chemical etching will be performed to reveal the microstructure, and EBSD measurements are planned to study deformation of the grain shape and orientation. Hardness maps will be obtained to quantify the hardening due to plastic deformation induced by the hole making process.
- Performing fatigue tests on punched samples with different clearances, and investigating the effect of reaming after punching.
- Performing fatigue tests on drilled samples with different drill bit quality, and investigating the effect of hole expansion after drilling.
- Performing fatigue tests on cut samples, to compare laser cutting, plasma cutting and waterjet cutting.