Anti-loosening bolted joints were developed with an innovative double-thread mechanism composed of coaxial single and multiple coarse threads. The number of coarse threads of the multiple-thread was set to 3 (denoted as 3thread DTB-II), and its thread structure was fundamentally modified as follows: (i) one of the three multiple-thread grooves was removed for 3thread DTB-II specimens and one of the two remaining grooves shifted downwards by a half pitch (denoted 3-1thread DTB-IIB) and (ii) the depth of the multiple-thread grooves was reduced by up to 50% of the thread height (denoted 3-1thread DTB-IIC). FEM thread rolling simulations were performed using a dedicated die. The two kinds of modified DTB-II specimens were rolled precisely and the thread heights reached the target value at all cross sections. The forming states in the thread rolling experiments well matched the FEM simulation states. The performance evaluation tests demonstrated that the 3-1thread DTB-IIC specimens had sufficient tensile strength, and its anti-loosening performance exceeds the reference level given in DIN25201.
