Stiffness as a criterion of dynamic load carrying capacity of tension-loaded bolted joints

Abstract

The influence of the bolt size and the width of the joint members/bolt diameter ratio (relative clamped length) on the stiffness coefficient of the bolt and joint members, as well as on the ratio of these stiffness coefficients are discussed in this paper. The individual stiffness coefficients of the bolt and the joint members decrease with the increase of the relative clamped length and the decrease of the bolt size. However, the stiffness ratio of the joint members and the bolt increases with the increase of the relative clamped length. Of the considered bolts M6 ... M24, the bolted joint with the M6 bolt has the highest stiffness ratio of the joint members and the bolt, and the bolted joint with the M12 bolt has the lowest stiffness ratio. When a bolted joint is loaded with a variable working load, then the dynamic safety factor (DSF) is used for evaluating the joint load capacity. The DSF increases with a decrease in the stiffness of the bolted joint, i.e. by increasing the relative clamped length of the bolted joint. For the same conditions analyzed, the bolted joint with M6 bolt has the largest DSF, and the bolted joint with M12 bolt has the smallest DSF. The obtained result can be used by engineers to evaluate the load-carrying capacity of dynamically tension-loaded bolted joints.