軸直角振動によるねじのゆるみに関する研究

ゆるみ機構の解明

抄録

This paper presents a solution for self-loosening mechanism of bolt-nut joints under transverse vibration. At the first stage of relative transverse displacement between fastened plates, a bolt-thread inclines in a mating nut-thread with slip on the screw-surface of the nut-thread, producing elastic torsion of the bolt-shank. At the next stage of the transverse displacement, the washer face of the nut slips on the surface of the vibrating plate, accompanying loosening rotation of the nut caused by spring back of the elastic torsion of the bolt-shank. Repetition of these behaviours in each cycle of the vibration, advances the self-loosening of the bolt-nut joint. Above mentioned self-loosening mechanism is analyzed theoretically, considering loci of slip on the screw surface and washer face. The theory is compared with the experiment, resulting that they show fairly good agreement, except small difference which is seemed to be caused by the fluctuation of the frictional coefficients on the screw surface and the washer face.