Nonlinear vibrational characteristic of bolt-joints

Bolt-joints are widely used in many structures,they reveal some nonlinearity subjected to different envi-ronment excitations generally.In order to study their nonlinear characteristic,a bolt-joint system was designed,and sin-sweep vibration tests were done on the system subjected to different base exciting.The resonant frequencies and the rela-tive damping coefficients of the bolt-joint system were obtained by analyzing the test data,they showed obvious nonlinear characteristic with the vibration level changing.In theoretic study,the system was simplified as a single degree of freedom mass-spring-damper model with a nonlinear sp ring and a nonlinear damper.The coefficients of the nonlinear dynamic e-quation were identified using the test data.Last,the main resonant frequencies and the relative damping coefficients of the system were obtained by using the nonlinear equation.The theoretic results were coincident with the test results better,it indicated that the nonlinear dynamic eauation dedueed here can describe vibration characteristics of a bolt-ioint system.