Research On The Non-iterative Method Of Dynamic Load Identifications

Machinery,vehicles,bridges,buildings and other engineering structures are often in the complex dynamic load excitation state.Only accurate obtaining these complex dynamic load information,we can judge the safety and reliability of the engineering structure.However,in many practical engineering structures,these dynamic loads are often difficult to be measured directly in complex environments.However,the structural response is relatively easy to obtain.Therefore,load estimation by structural response is one of the most effective ways to solve this problem.In this paper,the load identification of two-dimensional(2D)and three-dimensional(3D)structures is researched based on Galerkin finite element method(FEM)and the least square method.The main research content of this paper is summarized as follows:(1)Based on Galerkin FEM,the forward problem of structural dynamics is analyzed,which lays a foundation for the research of inverse problem.The accuracy of the calculation of the forward problem is very important for the research of the inverse problem.The FEM is used to discretize the compute domain and the Newmark method is adopted to deal with the time-domain problem.The numerical example results show that the Newmark method has high accuracy and stability in solving the forward problem of structural dynamics.(2)Based on the forward problem model established by Galerkin FEM,the relationship between the measured point response and the load at the point to be identified is found by matrix transformation.At the same time,the error function is established,and then the dynamic load is inversed directly by the least square method.The influence of the selection of the expanded basis function,the computation time,the measurement noise,the number of measurement points and the position of measurement points on the inversion results are discussed with numerical examples.The inversion results of numerical examples show that the present method has high precision and good robustness for solving 2D and 3D load identification problems.(3)The corresponding solution of system ill-condition matrix is a difficult problem in inversion process.In this paper,the method of basis function expansion is adopted to reduce the dimension of the solution matrix and improve the efficiency of the solution.For the ill-condition matrix,the singular value decomposition method is used to obtain more accurate inversion results.The load identification method proposed in this paper enriches the theoretical basis of load identification and provides guidance for the field of safety detection to a certain extent.At the same time,this work can lays a certain foundation for the rapid load identification of complex nonlinear problems in the future.