The mechanisms of loosening resistance components are investigated within the framework of the three-dimensional finite element method (FEM). Here, the results of the double-nut tightening method (DN), spring washers (SW), and conical spring washers (CSW) are shown. This paper focuses on the comparison among the components above based on the results that have been published separately. For details on each analysis, readers are referred to [10–12]. We have found that DN shows significant loosening resistance if the locking is properly realized in the tightening process. However, if the locking is not performed properly, its ability to resist loosening completely disappears. SW shows negative loosening resistance because the sticking area on the contact surfaces is limited to two corner edges of the SW and the rotational force around these edges thus drastically leads to loosening. In regard to CSW, in the case of high axial force, it shows no apparent effect on preventing loosening. On the other hand, in the case of low axial force, it shows two opposite effects. The negative effect is an increase in the loosening rotation angle, while the positive one is the prevention of a decrease in axial force. When complete bearing-surface slip occurs, a CSW can prevent loosening because the positive effect becomes larger than the negative one. However, when only small bearing-surface slip occurs, a CSW cannot prevent loosening because the negative effect cancels the positive one.

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