Dynamic Analysis Of Local Nonlinear "Product-Packaging-Vehicle" Coupled Structure

The product transport packaging system can be regarded as a “product-packaging-vehicle” coupled structure in logistics transportation.The inverse sub-structuring method can predict the dynamic characteristics of product in the “product-packaging-vehicle” coupled structure,so it has developed rapidly in the field of transport packaging.In the past,the inverse sub-structuring method regarded the transport packaging system as a linear system.In fact,due to the nonlinearity of packaging materials,the transport packaging system is a nonlinear system.Using a linear system instead of a nonlinear system may bring unacceptable errors.In this paper,the local nonlinear “product-packaging-vehicle” coupled structure is taken as the research object,and a nonlinear inverse sub-structuring method is proposed to predict the dynamic characteristics of the substructure in the nonlinear system.The main research contents are as follows:(1)A decoupling strategy for nonlinear systems based on the inverse sub-structuring method is proposed,which is called the nonlinear inverse sub-structuring method.The analysis process can be divided into three steps: firstly,the nonlinear system is linearized by using the describing function method;secondly,the inverse sub-structuring method is used to decoupling the quasilinear system;and finally,the modal parameters identified by the modal parameter identification technique are used to calculate the frequency response function(FRF)of the substructure.(2)Based on the nonlinear inverse sub-structuring method,the theoretical formula of nonlinear inverse sub-structuring method for the two-substructure flexible coupled nonlinear system is derived,which is used to predict the FRF of the substructure in the nonlinear system.Firstly,a two-substructure single-coordinate flexible coupled system is studied,and the corresponding lumped parameter model and FEA model are established to verify the proposed method.After that,the proposed method was extended to two-substructure multi-coordinate flexible coupled nonlinear system.(3)Based on the nonlinear inverse sub-structuring method,the theoretical formula of nonlinear inverse sub-structuring method for the two-substructure flexible coupled nonlinear system is derived.The two-substructure single-coordinate rigid coupled nonlinear system and two-substructure multi-coordinate rigid coupled nonlinear system are studied respectively.The corresponding lumped parameter models are established to verify the proposed method.(4)The evaluation index of the nonlinear system dynamic transfer characteristics is proposed,and the influence of the nonlinear element response amplitude on the nonlinear system dynamic transfer characteristics is discussed.The threshold method is proposed to improve the analysis accuracy of the random vibration level of the vehicle,which laid the foundation for the dynamic characteristics analysis of the nonlinear system under random excitation.