Study on local slippage accumulation between thread contact surfaces and novel anti-loosening thread designs under transversal vibration

The accumulation of local slippage between thread contact surfaces has recently emerged as a key reason for the self-loosening of threaded fasteners subjected to transversal vibration. However, the mechanism of local slippage accumulation is still elusive despite intense research. The authors recently proposed modified Iwan models to theoretically analyze local slippage accumulation and identified the principle of anti-loosening, upon which some novel anti-loosening structures were designed. However, simulation validation of the modified Iwan models and deep performance analysis of novel thread structures are lacking. Hence, we developed novel algorithms to simulate the modified Iwan models for the cumulative process of local slippage. These algorithms confirmed that the previous theoretical analytical results are reliable. Additionally, the mechanism of local slippage accumulation was revealed and the critical local slippage accumulation was studied. We also compared systematically the tightening and anti-loosening performances of proposed novel thread structures with other existing anti-loosening products by finite-element analyses and experiments. The novel thread structures exhibited superior anti-loosening performance and were convenient to install and remove.