The Optimum Tightening of a Bolted Slip Resistant Lap Joint

Bolted joints of the metal constructions of cranes, bridges, housings of ships or aircraft are subjected to shearing forces. In general, the process of joint formation involves compressing metal sheets, drilling and finishing openings, inserting bolts, installing washers, tightening and fastening nuts. Openings in the construction members can be larger or smaller than the bolt diameter, i.e. the bolts are fitted with clearance or interference. The tightening of the bolt in an interference fit joint is rarely taken into account. However, the tightening can either increase or reduce the strength of the joint. Using the analysis of stresses in the effective cross-section of the bolt, the optimal tightening force is determined, which reduces the equivalent stress to the minimum. The optimal value of tightening is determined depending on the coefficient of friction between the joint members, and the shearing force. The range of tightening forces where the stress in the bolts does not exceed the stress of an untightened joint is calculated. The optimal tightening leads to the reduction in weight, size and cost of the joint. Labor intensity of the manufacturing and installation process is also reduced.

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