Structural Analysis And Multi-objective Optimization For 25MN Hydraulic Press Frame Structural Frame

The main frame of hydraulic press is the basic support component,its weight accounts for the whole weight from 40%to 60%.A well-designed frame does have a dominant effect on the whole equipment weight lighting,the rigidity improving for better shape products and the costs of manufacture and transportation reducing.The current developments tendency of hydraulic press frame are toward to the one with better strength,higher stiffness and geometric accuracy,more excellent load stability and fatigue resistance,and less weight.A hydraulic press frame was studied in this work.A finite element assemble model was established for probing the dynamic responses of the frame and the mechanisms of keeping all its components connected firmly when suffering to the pre-tighten loads combined with pressing load.The structure topology optimizations of up-beam and base-beam were also performed.After that,a parametric finite element modeling and multi-objective optimization based strategy was put f-orward for the mainframe lightweight design.An existing 25MN firebrick press frame was taken as a studying object in this work.By using the finite element modeling method,an analysis model of pre-tightened assemble frame had been established in which the frictional interaction relations between the parts were considered and simulated.The numerical analysis results were verified by the experimental tests.Those results combined with the actual service situations of the press frame are all indicated that the original designed frame has a good overall performance and can fit the demands in strength and stiffness.It was also shown that the up-beam and base-beam have a large room to be optimized and lighten.These two parts will be the dominances in the following lightweight design process.It is recommended in modern design methodology method that the structural topology optimization should be performed in the conceptual design phase in order to form a good initial design scheme.Thus the finite element models of up-beam and base-beam were setup for the structure topology optimization where the manufacturing and assembly constraints were considered to form the initial design space.The sub-modeling technology was used to determine the boundary conditions of load in the beams.According to the outcomes of topology optimization,new structure design schemes of the beam parts were proposed.Based on these structure schemes,parametric modeling and multi-objective optimization research for the frame would be carried on later.Considering the components of the frame are connected as a unitary structure for bearing the load,thus the optimization of the mainframe structure should not be confined to some certain independent components.It should be a comprehensive and integral structure optimization.Python scripting language is used to implement the parametric finite element model for topology changing in case of machine assembly and to extract the numerical results from the database.A plug-in program with interactive graphical user interface was developed,with which the processing of the combination of the parameter optimization and topology optimization can be realized automatically and conveniently.For large models,design optimization quickly becomes infeasible due to the computational costs of-the repeated analysis of the FEM model.For alleviating the pain of this shackle,a surrogate model based on the DOE(design of experiments)and approximate modeling was constructed for gaining the relationship between the mechanical responses of the frame structure and design variable parameters.A multi-objective optimization model of the mainframe was established,which takes light weight and high stiffness as object of optimization and defines the variables bound of the key dimensions and the demanded properties as the constraints.Solving the model by appropriate optimization algorithm,optimized design schemes for the mainframe of hydraulic press was obtained.The Pareto optimized design schemes for light weight and high stiffness provides multi feasible solutions for the mainframe of the hydraulic press.The design result of optimization was validated by its full finite element model.The numerical results were compared with those of the original design scheme,which were showed that the optimized design schemes can meet the requirements of strength and stiffness in frame design standards.The total mass of the frame is decreased by 15%.Compared to the original design,the maximums of stress in the hazardous regions are reduced sharply;meanwhile the design constraint conditions are all met.In conclusion,this research has succeeded in the integration of the topology optimization,parametric modeling and multi-object optimization in the framework of design optimization,which provides a new method for other large-scale complex manufacturing equipment structural optimization.