Investigations On The Fatigue Strength Of Threads Produced By Different Fabrication Techniques

The increasing importance of sustainability in engineering demands the development of long-lasting, high-performance components that reduce material and energy consumption over time. This study investigates how different thread manufacturing processes, i.e., cutting, rolling, and deep rolling, affect the fatigue strength of bolts made from 42CrMo4+QT steel. Cylindrical specimens with M12 threads were subjected to cyclic tensile loading with constant mean stress. Fatigue strength was evaluated using the staircase method, and supporting analyses included X-ray diffraction for residual stress, and full width half maximum examination and Vickers microhardness measurements. Results show that thread rolling significantly improves fatigue strength, achieving 113.8 MPa compared to 45.1 MPa for cut threads. Deep rolling also enhanced fatigue strength to 71.1 MPa, offering a practical alternative for low volume production. Residual stress and hardness distributions confirmed the mechanical benefits of both rolling methods.