The FRF-based Substructure Method Based On The Displacement Control On The Interfaces And Experimental Research

The dynamic substructure methods can greatly reduce the scale of the model,save the calculation cost,facilitate the division of task between the departments,and benefit to substructure model modification.The method has been increasingly applied to large complex assembly structure.Dynamic substructure method mainly includes Component Mode Synthesis(CMS)and FRF-based substructure(FBS).CMS in the test model has many difficulties unresolved,including modal truncation error.With the improvement of measurement accuracy about frequency response function(FRF),the FBS method is more and more widely used.The method can synthesize the FRF between theoretical models,test models and mixed models.In recent years,FBS method has been widely used in automobile,marine,aerospace and other fields.But there are often some problems in application to limit the development of the method.First of all,the traditional FBS method can only deal with the cases which include each substructure's connection interface grid or measurement points consistent.But in practical engineering applications,the FRF of substructures are sometimes obtained by different departments.So they may be obtained through numerical calculation or test.The theoretical models,test models,or mixed models are inevitably faced with the case of interface grid or measurement points inconsistent.This requires the connection interface to be processed,and improve the FBS formula to ensure the consistency between FBS and overall structure.Secondly,the FRF of each substructure is generally different from that in the whole coordinate system.This requires that the FRF of each substructure must be transformed to the whole coordinate system.Furthermore,for some symmetrical structures in engineering,sometimes the FRF information of one or several substructures just need to be obtained.And the other substructures' FRF can be obtained by transforming the known substructures' FRF,which can not only greatly improve the computational efficiency,also eliminates the process of establishing each substructure model.In this paper,the dynamic substructure method is applied to the engineering practice firstly,and then the problems of the FBS method are discussed.The FBS algorithm of the interface displacement control is proposed in this paper.The method can solve the problem that the interface of substructures are inconsistent.The rotation and mirroring technology are introduced into FRF methods for further solving the problem that substructures' coordinate systems are different from whole coordinate system.It is also applicable to the symmetrical structure to improve the calculation and modeling efficiency.Finally,the experimental study on the proposed FBS algorithm is carried out,and the feasibility is verified by using proposed algorithm in the model.