Our objective is to develop a long-life rotary machine for synchronous generators and motors. To do this, it is necessary to design a high-strength bolted joint, which is responsible for fixing a salient pole on a rotor shaft. While the rotary machine is in operation, not only centrifugal force but also moment are loaded on a bolted joint, because a point of load is eccentric to a centre of a bolt. We tried to apply the theory proposed in VDI2230-Blatt1 to evaluate the bolted joint under eccentric force, estimate limited centrifugal force, which is the cause of partial separation between the pole and the rotor shaft, and then evaluate additional tension of a bolt after the partial separation has occurred. We analyzed the bolted joint by FEM, and defined load introduction factor in that case. Additionally, we investigated the effect of the variation of bolt preload on the partial separation. We did a full scale experiment with a prototype rotor to reveal the variation of bolt preload against tightening torque. After that, we verified limited centrifugal force and the strength of the bolted joint by the VDI2230-Blatt1 theory and FEM considering the variation of bolt preload. Finally, we could design a high-strength bolted joint verified by the theoretical study and FEM analysis.
Our objective is to analyze both tensional and bending stress of bolted joints under eccentric load. Especially, our analysis is under four combined conditions as described below, (1) embedded bolted joints, (2) thinner clamped plate, (3) large eccentric load, (4) permitting partial separation. Those combined conditions include some difference between ours and previous researches. The partial separation easily occurs at structural interfaces under those combined conditions, and both stresses sharply increase due to the propagation of the separation. That is the reason why it is very important to consider the effect of partial separation. There are many analytical methods based on numerical calculations or FEM analysis, however, there is no numerical calculation method, which is justly applicable under those combined conditions. We apply Faulhaber method proposed in VDI2230 and develop our original method considering the bolt axial loads, which are composed of both bolt's deflection and deflection angle as beam. Numerical calculations on the above-mentioned and experiments and elastic FEM analysis based on three dimensional contact theory were conducted. The results about our method's correlation against experiments and FEM analysis are shown in this report.
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