Dynamics Modeling And Parameters Identification Of Non-linear Bolted Joint Beam Structure

Bolted joint is one of the most common connection types in mechanical system. In most cases, the joint part have significant influence on the dynamic behavior of the assembled structures due to the nonlinear characteristics. It will change the natural frequency, stiffness and damp of the structures compared with the rigid connection. So, in order to analysis the dynamic characteristics and predict the response accurately, it is necessary to develop the nonlinear dynamic model and identify the parameters of bolted joint, especially the stiffness and damp.In this paper, the bolted jointed beam structure is taken as a case to mainly study the influence of the joint part.First, seven kinds of identification methods of nonlinear system are summarized, and according to these methods, the normal identification process of nonlinear system is developed, namely, detection, characterization and parameter identification.Then, based on the identification process, detect and characterize the bolted joint beam. First, the basic theory and the corresponding test method are introduced; then, develop the vibration test system of the bolted joint beam, and finally, use three method, harmonic distortion, coherence function and frequency-response function, to detect and characterize the nonlinear of the bolted joint beam separately.After that, based on the characterization test and mechanism analysis, use the parallel Iwan model to simulate the nonlinear dynamic phenomenon of the contact surface, a SDOF nonlinear model of bolted joint cantilever beam is developed using the Duffing function. Furthermore, the force-state mapping method is chosen to analysis the response in time domain under single frequency and fixed lever force, and estimate the stiffness and damp of joint part.Finally, another two DOF model is also developed with boundary condition and compatibility requirement on the basis of vibration beam theory. After that, multiple scales method is used to solve the fourth-order partial differential equation to get the analytical solution of linear term and frequency-response equation of nonlinear term. With the experiment data, the liner parameter and nonlinear parameter of the modal is identified.