Fatigue mechanisms and crack strain field measurements on bolt hole detail

The bolt hole detail's fatigue and crack growth behaviour were investigated through experimental testing and numerical approaches. Three fatigue models were used to describe the fatigue behaviour obtained from experimental tests. Fatigue mechanisms were evaluated by considering the impact of hole execution methods, protective coatings, and material type. A characteristic S-N curve was derived, showing that Castillo's model offered the most reliable fatigue life predictions across all stress range levels. Results also demonstrated that the EC3–1-9 design curve provides unsafe predictions at high-stress range levels compared to experimental data. Regarding fatigue crack growth, tests were conducted on specimens with both single and double cracks emerging from the bolt hole. The presence of multiple cracks led to a significant reduction in fatigue life. Beach and striation marks were identified in crack surfaces using optical and scanning electron microscopes. Digital Image Correlation measurements were used to capture strain fields ahead of the crack tip during the crack growth process, confirming distinct displacement patterns depending on the crack configuration. Overall, the findings highlight the critical role of fatigue mechanisms and crack growth assessments on the fatigue strength of bolt hole details. These results contribute to improving the quality of fatigue life predictions and provide valuable insights related to the fatigue crack growth on bolt hole details. • Castillo's model delivers the most accurate fatigue-life predictions across all stress ranges. • EN 1993–1-9 design curve is unsafe at high stress ranges and overly conservative at low stress ranges. • Hot-dip galvanizing reduces high-cycle fatigue life, and punched holes perform worse than precision-drilled holes. • Double-sided cracks reduce fatigue life by 30 % compared to single-sided cracks • Distinct displacement patterns were observed depending on the crack configuration.