Fatigue analysis of cold rolled high strength fasteners considering the work hardened layer and residual stresses from the manufacturing process

Cold-rolled high-strength fasteners are widely used in safety–critical joints subjected to severe cyclic loading. Despite their relevance, the effect of manufacturing-induced residual stresses and work-hardened layers on fatigue performance is often neglected. This study presents a combined experimental–numerical framework for fatigue life assessment of M30 high-strength bolts explicitly accounting for the residual stresses and strain-hardened layer generated during cold rolling. The material behaviour of quenched and tempered 32CrB4 steel was characterized under a wide range of strain rates and temperatures to calibrate a Hensel–Spittel constitutive model using torsion and hammer tests. The thread rolling process was simulated using Forge®, and the resulting residual stresses were transferred into an ANSYS fatigue model through a dedicated mapping procedure. Validation was achieved by microhardness and X-ray diffraction measurements, as well as full-scale fatigue tests performed in accordance with ISO 3800 in a 1.5MN machine. The comparison between numerical and experimental results demonstrates that incorporating residual stresses markedly improves life prediction accuracy, highlighting their beneficial compressive effect in delaying crack initiation. The developed methodology provides a robust foundation for integrating manufacturing effects into fatigue design of high-strength fasteners used in heavy-duty applications.