Tightening and anti-loosening performance of spring washer connecting bolts

This paper investigates the tightening and anti-loosening performance of phosphated spring washers (i.e., PSW) and galvanized spring washers (i.e., GSW), considering three torques and comparing them with galvanized flat washers (i.e., GFW). Subsequently, a finite element model of the spring washer connecting bolt was established and validated, further investigating the force performance of the spring washer and the stress distribution in the thread area. Finally, a quantitative evaluation method for the anti-loosening performance of spring washers was proposed. The results show that the preload of GSW is maximum after the nut is tightened, and the loss of preload can be supplied by the flattened spring washer. At the same time, the inner ring of the spring washer is sticking, while the outer ring is sliding. Similarly, the contact pressure of the washer decreases radially. During the lateral vibration process, the decrease curve of preload consists of three stages: initial stage, stable stage, and loosening rotation stage. Specifically, GSW has the best anti-loosening performance, because the wear of the zinc layer increases friction. More importantly, the spring washer compensates for the gap between the nut contact surface during transverse vibration, ensuring uniform force distribution in the threaded area and effectively improving the anti-loosening performance. • The performance of phosphated spring washers and galvanized spring washers is compared. • The force of spring washers under the conditions of tightening and transverse vibration is analyzed deeply. • The evaluation method of spring washer's anti-loosening performance is proposed. • The anti-loosening mechanism of spring washers is revealed.