The Analysis Of Dynamic Characteristics Based On The Structural Model Of Fine Boring Machine

Shenyang Machine Tool Group and Equipment Diagnosis Engineering Center of NEU jointly develop multi-position and high-precision coordinate borer. Based on this research background, this paper attempts to make predictions for the dynamic characteristics of fine boring machine, which is still in design stage, through the analysis of dynamic characteristics of the structural model of fine boring machine.This paper firstly summarized the status quo and achievements of domestic and international present research in dynamic characteristics of machine tools and then derived the law of similitude to natural frequency and principal mode of prototype and model on the basis of dimensional analysis. According to the law of similitude, this paper designed and made the structural model of fine boring machine. Thereafter, based on the theory of modal analysis, this paper systematically applied the finite element method to building the finite element model of the model system and the similarity of dynamic characteristics of the big model and the small one was analyzed.The relative motion exists between straight bar and sliding bearing in the structural model. It has always been difficult in structural finite element analysis that how to simulate the relative motion of combining site accurately. In this paper, the author separately adopted the method of coupling degree of freedom and the method of fixed interface component mode synthesis to calculate the dynamic characteristics of the structural model. The study found that both methods have high calculation accuracy to natural frequency and vibration mode of the model system, but to high order mode, the calculation accuracy of fixed-interface modal synthesis is higher than that of coupling degree of freedom.The analysis of structural dynamic characteristics requires an accurate mathematical description of structural system. At present, the finite element technology is mainly used to build numerical calculation model of theoretical model. Because of the hypothesis on the physical properties and geometric characteristics of the structure, the simplification of structural constraint, connection ststus and so on, the theoretical model exist errors in three main aspects:model structure, model order and model parameters. That whether the accuracy of the calculating results is reliable or not must be verified by experiment. According to modal analysis theory, modal testing system is built in this paper and modal parameters of the structural model are recognized with the procedures of modal parameters identification in frequency domain.On the basis of modal correlation principle, the modal correlation analysis is done between the theoretical results and expemental results of the structural model in this paper. The consistency of the correlation analysis results prove the correctness of the theoretical modeling method of the structural model, which laies a foundation on the dynamic response calculation and the dynamic stiffness analysis of fine boring machine. Simultaneously, the reasons of low modal correlation of the composite structures are analyzed in this paper; several main factors that affect the modal correlation are also discussed.