Structural Safety Analysis of Main Shaft for Wind Power Generators Considering Mass Effect

摘要

The main shaft for wind power generators, the largest part in the nacelle, is manufactured by casting or forging. The weight of the main shaft, depending on the design, is generally 10 to 20 tons, and thus is significantly affected by the mass effect in cooling. In the present study, a cooling test was performed with a large specimen of 42CrMo4, which is often used as the material for the main shaft, to empirically obtain the hardenability from the surface. Since the hardenability is dependent on the size of the main shaft, for standardization, DEFORM and JMatPro software programs were used to predict the hardness on the cooling curve at different positions and the predicted results were compared with the experimental hardenability results. When the mass effect was considered, the strength was higher at a position closer to the surface and lower at a position closer to the core. These experimental results were expressed as a function of mechanical strength depending on the depth. An ANSYS structural analysis was performed to calculate the equivalent stress. The safety factor was compared between the case where the mass effect was considered and the case where the yield strength was constant over the entire specimen for a more accurate evaluation of the structural safety.