Structural Topology Optimization Method Research On Pre-loaded Bolt Connection Nonlinearity

Among the engineering design methods,optimization design is the fastest growing one.It can help designers find the most perfect scheme from several design options.Because of its considerable benefits and indispensable status,it has attracted more and more attention.In the three levels of structural optimization,structural topology optimization can provide designers with the optimal conceptual configuration in the initial stage of design,and thus has more extensive recognition and practical value than size optimization and shape optimization.When carrying out topology optimization research on complex engineering structures,it is of great significance to consider the nonlinearity of the connection parts.Because the nonlinear characteristics of stiffness and damping of the connection structures have an impact on the mechanical properties of the overall structure.And the microscopic and macroscopic slip phenomena generated by the external loads on the contact interface will lead to nonlinear changes in the local stiffness of the structure.In this paper,based on the evolutionary structural optimization method(ESO method),the six-parameter Iwan model is used to describe the nonlinear mechanical properties of the connection structure,and a topological optimization algorithm of combined structures containing pre-loaded bolt connection is established and used in practical examples to verify the rationality.The main research contents are listed as follows.Use the six-parameter Iwan model to describe the nonlinear mechanical behavior of bolted joints.The arithmetical discretization method based on stiffness is selected for discretization.The identification parameter value is applied to the plate support structure with pre-loaded bolt connection.A static and a dynamic analyses are performed on the plate support structure example respectively.The best configurations under given conditions are obtained and the applicability of the six-parameter Iwan model is verified.It is proved that the six-parameter Iwan model can be used to describe the nonlinear behavior of bolt connection parts.Based on the evolutionary structural optimization method and the six-parameter Iwan model for nonlinear analysis,set the minimum structural mass as the objective function,the maximum equivalent stress of the element under the allowable stress requirement,and the slip at the connection parts smaller than the allowable value as constraint conditions.The nonlinear topological optimization mathematical model of structure containing pre-loaded bolt connection is established and the corresponding parameters are selected to form a complete optimization algorithm.Then use the APDL language in ANSYS software to compile a TXT command stream input file containing optimization steps of parameter definition,static(or dynamic)load application,analysis and solution,and post-processing.Finally,the finite element models of combined structures with pre-loaded bolts are established.Then the topological optimization of nonlinear statics and nonlinear dynamics is performed on the combined structures respectively.The optimized configuration of different material dosages and the optimal configuration satisfying the constraint conditions are obtained,which verify the applicability of the optimization algorithm of combined structures containing bolt connections.