Lightweight treatment of large vibrating screen using equivalent static loads

A vibrating screen has been widely used in agriculture, coal mining, and woodworking industry. High efficiency of vibrating screens has been required for large-scale production in recent years. However, the structure can inevitably bear the large dynamic load, leading to fatigue damage, such as some cracks after working for a period of time. The reason is that the large dynamic inertia force can be generated by the body mass of a large vibrating screen. In this study, the overall structural strength of the newly developed BF14260 large vibrating screen was analyzed to determine the position of the maximum equivalent stress and the main stress distribution area using the combined test and finite element simulation. The main frame model of the vibrating screen box was constructed to combine the equivalent static load and sub-model method. The structural displacement fields under the equivalent static load and dynamic load at a certain time were transformed from the dynamic response optimization into structural static optimization. Moreover, the calculation scale was reduced to greatly improve the optimization and calculation efficiency. Then, the equivalent static sub model was topologically optimized with the variable density, in order to identify the material distribution for the best structural performance. As such, the optimal conceptual model was obtained to reconstruct the practical model. The three-dimensional and dynamic partial stress relationship of the maximum or greater stress nodes in each structure after topology optimization was compared to further improve the structural strength of the vibrating screen. The vibrating screen structure was then strengthened to add some stiffeners. The research results show that the most beams bore small stress, and the mass of the main frame of the vibrating screen accounted for about two-thirds of the mass of the components of the vibrating box, except that the vertical beam connected with the outrigger and the beam on the H1 plane were the main load-bearing beams, in terms of the dynamic stress cloud diagram of the original structure for one week, and the dynamic stress cloud diagram of the time point of the maximum equivalent stress. The structure after topology optimization effectively reduced the stress and the fluctuation frequency of dynamic stress, while the mass was reduced by 28.5% than before, indicating the stability of stress fluctuation for the better fatigue life of the beam. The local strengthening treatment significantly reduced the maximum equivalent stress of each supporting main beam in the vibrating screen, even if the stress carried by the whole beam member was reduced, indicating the uniform stress distribution after topology optimization. The final optimization was that the maximum stress decreased from 79.4 to 49.3 MPa, indicating a decrease of 37.9 % than before. The weight was reduced by 1 080 kg and 25.6%. Consequently, the combination of equivalent static load and sub model method can be widely expected to transform the dynamic into static optimization. Among them, the main research objects were separated by the cutting boundary position interpolation method. Correspondingly, dynamic optimization can effectively deal with complex structures for the high optimization efficiency in the structure design of vibrating screens during large-scale production. © 2022 Chinese Society of Agricultural Engineering. All rights reserved.