Experimental Evaluation of Fatigue Life in Elastically Bended Double-Lap Bolted Joint

Double-lap bolted joints have been widely applied for connecting parts in various Industries owing to their structural stability and ease of manufacturing. When double-lap bolted joints are under loading, the section that sustains the load by friction between the surfaces of the components fastened by the bolt is called the frictional mode, which is before the load is transmitted to the bearing surface of the bolt. The clamping force decreases owing to cyclic loads even in the frictional mode, therefore, it is necessary to understand the fatigue characteristics in this section. We performed fatigue tests according to the initial clamping force and magnitude of cyclic load in the frictional mode for a special type of joint called an elastically bended double-lap bolted joint. The compressive strain generated in the clamped part between the double-laps was measured during the fatigue test to obtain the continuous behavior of the clamping force. Basically, the clamping force decreased as the cycles of the load increased, however, the rate of the decrease varied according to the test phase. The test phase was divided into four stages by analyzing the behavior of clamping force, and an appropriate method for calculating the fatigue life was established.