Effect of Clamping Force of Double Nuts on Fatigue Strength of Bolted Connection

Abstract

It is study, effect of the clamping force of double nuts on fatigue strength of bolted connection was investigated under the conditions of clamping in elastic and plastic regions and also in the case of applying pre-load torque to bolt. The results are as follows : From a standpoint of fatigue strength, it is by the optimum clamping method of double nuts that both lower and upper nuts can be clamped with the same clamping torque. Upper nut (lock out) of double nuts not only prevents a relaxation of bolted connection buy also gives an effect on the clamping force and fatigue strength of it. When a bolt is clamped in plastic region, fatigue strength of bolted connection is improves. Fatigue strength of bolted connection depends on the total clamping force of double nuts.