Experimental and numerical investigation of the effect of clamping force on the fatigue behaviour of bolted plates

In this research, both experimental and numerical methods were used to investigate the fatigue behaviour of bolted plates. In the experimental part of the research, a holed plate was clamped using a bolt and a nut, and then tested under axial cyclic load in a fatigue testing machine. In order to obtain S–N curves and investigate the direct effect of the isolated clamping force on the fatigue behaviour of the bolted plates, three batches of specimens each subjected to different clamping forces were fatigue tested. The clamping forces were obtained experimentally from the compressive axial strain of a steel bush which was placed between the nut and the plate. In the numerical method, to determine the stress and strain distributions due to combined clamping force and axial load in plate, 3D finite element models were generated using a numerical package. Numerical simulation and experimental results showed that the fatigue life of bolted plates improve because of the compressive stresses created around the plate hole due to clamping force. The life improvement was greatest at the high cycle fatigue life region of the S–N curves.