A windlass driven heavy duty multifunctional billet tong was designed for large-scale forging and casting to reduce the number of auxiliary material handling devices in manufacturing workshops. To improve its mechanical performance and safety, a novel multi-objective topology optimization method for its curved arm is proposed in this paper. Firstly, the influence of different open angles and working frequencies for the curved arm was simplified to a multi-objective optimization problem. A comprehensive evaluation function was constructed using the compromise programming method, and a mathematical model of multi-objective topology optimization was established. Meanwhile, a radar chart was employed to portray the comparative measures of working conditions, the weight coefficient for each working condition was determined based on the corresponding enclosed areas, combining the stress indices, the displacement indices and the frequency indices of all working conditions. The optimization results showed that the stiffness and strength of the curved arm can be improved while its weight can be reduced by 10.77%, which shows that it is feasible and promising to achieve a lightweight design of the curved arm of a billet tong. The proposed method can be extended to other equipment with complex working conditions.

The existing bionic design methods are based on the similarity theory, but it is difficult to find a bionic prototype with high similarity for the control arm. In this paper, a design method combining load path analysis and biological characteristics is proposed to realize the lightweight of control arm. The load path is used to visualize the load-transferred law in structure and identify the load-bearing performance. Then, the structural improvement suggestions are given and a new control arm with the coupling load of bending moment and pressure is established. Then, the cross-section of wheat-stalk is selected as the cross-section of control arm from four kinds of plants including Bamboo, Wheat-stalk, Juncus, Brazilian Horsetail because of its good bending-resistance and torsion-resistance. The bionic model is designed and the mechanical performance is analyzed and verified by Finite Element Analysis. The results show that the stiffness and strength of the control arm are improved by 65.6% and 22.5% respectively, and its weight is reduced by 32.7%, which show the feasibility and efficiency of the proposed method.

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As the main load-bearing structure of heavy machine tools, cranes, and other high-end equipment, the large-scale box structures usually bear moving loads, and the results of direct topology optimization usually have some problems: the load transfer skeleton is difficult to identify and all working conditions are difficult to consider comprehensively. In this paper, a layout design method of stiffened plates for the large-scale box structures under moving loads based on multiworking-condition topology optimization is proposed. Based on the equivalent principle of force, the box structures are simplified into the main bending functional section, main torsional functional section, and auxiliary functional section by the magnitude of loads and moments, which can reduce the structural dimension and complexity in topology optimization. Then, the moving loads are simplified to some multiple position loads, and the comprehensive evaluation function is constructed by the compromise programming method. The mathematical model of multiworking-condition topology optimization is established to optimize the functional sections. Taking a crossbeam of superheavy turning and milling machining center as an example, optimization results show that the stiffness and strength of the crossbeam are increased by 17.39% and 19.9%, respectively, while the weight is reduced by 12.57%. It shows that the method proposed in this paper has better practicability and effectiveness for large-scale box structures.