The model of bolt and sphere was created with C3D20R elements.Surface to surface contact discretization method was used to simulatethe contact between the bolt and sphere thread surface, tangential behaviorwas defined by Coulomb friction force and the friction coefficientwas taken as 0.15 according to literature [37,38], and the normalbehavior was set as “Hard contact”. After a mesh convergence study,the element size of the bolt and sphere was 2.5 mm and 4 mm, respectively.At the bolt threads region, however, the smaller element sizeof 1 mm was adopted to capture the stress concentration, as shown inFig. 12(b).