Bolt Contact Stiffness Calculation Analysis And Experimental Study

Bolt connection is widely used in mechanical structure. The surface between two components is defined as joint surface. The research shows that in dynamic mechanical design, the availability of reasonable combination of kinetic parameters, as well as its own mechanism and the role of reasonable characterization of the dynamic character is the key to establish accurate dynamic model of the mechanical structure. Therefore, the study of the dynamic characteristics of the mechanical joints is of great significance. The research of Joint can be divided into micro research and macro research. Micro research generally gets the characteristics of the Joint through the testing and analysis of the deformation of Physical mechanism and characteristics of the Joint. Macro research generally uses springs model to. simulate Joint and establish the vibration system model.In the aspect of micro, to illustrate the mechanism of contact stiffness generated, pairs of asperity in rough surface are analyzed. Using the Hertz contact model results, the influence of external conditions to the stiffness was explained in this paper. Reference to the contact stiffness model based on fractal theory conclusions, the pattern of normal contact stiffness variation with the normal load and rough surface fractal parameters is simulated.In the aspect of macro, joint surface is simplified as a spring, the spring stiffness to be determined is the joint surface contact stiffness. The stress distribution of joint surface can be obtained by FE method, using the relationship between unit area normal contact stiffness and normal load, the normal contact stiffness in different preload force conditions can be extracted, then the equivalent bolt stiffness values can be acquired.To identify the contact stiffness parameters, the model updating method is used in this paper. Modal parameters of bolt connection structure under different preload can be obtained by experimental modal analysis. When building the finite element model to be corrected, bolt stiffness parameters are setting as design variables, and the modal parameter error function between simulated and tested is setting as objective function. Minimizing the error function, modal parameters between finite element model and the test model match well. The bolt stiffness parameter values preload in different states can be acquired, and the FE model fits the tested model well.