3.1. Finite element model
The experimental fan blade specimen was shown in Fig.3. The fan was composed of hub, wheel and 60 blades. When the fan was driven by variable frequency motor to rotate, the blades were under the interactive fatigue load for a long time, which may lead to the blades fatigue failure under a certain number of cycles. The finite element model of the fan blade was established to simulate the working condition of the fan blade, so as to determine the dynamic stress distribution of the fan blade, the maximum stress in the stress concentration area and the possible failure position of the blade[35]. In this study, we used ANSYS software for analysis and a 3D finite element model of fan blade was established. We used Hypermesh software to mesh the fan blade model, and on account of the complexity of geometric structure, the simulation model was established by 427K 8 nodes solid hexahedron elements. The mesh size was 0.4~5mm, and 1.1 million hexahedron meshes were divided, as shown in Fig.4. Considering the influence of friction force and contact force of structural parts of fan, centrifugal force simulation of all elements in the model was carried out by using angular velocity. The stress distribution at critical point of blade components was calculated.