Modal Coupling Vibration Analysis of Bolted Casing System Based on Surface Contact Mechanics

The casing system is the skeleton of the aero-engine, and its vibration directly reflects the vibration level of the whole aero-engine. Different from the previous modeling of the casing system as a cylindrical shell, this paper creatively establishes the lumped mass modal coupling vibration model of the bolted connection casing system from the perspective of micro contact mechanics. The bolted connection characteristics and Hertz contact characteristics of micro topography of discontinuous casing are considered, which rarely appear in previous studies on casing system modeling. The paper first completes the interface contact mechanics modeling of bolted connection, and then the establish interface contact mechanics model is effectively verified (by comparing with classical model and finite element model). Based on the established contact mechanics model of the connection interface, a modal coupling model of the casing system is established. The effects of interface stiffness ratio, interface fractal parameters, the number of connection bolts and friction coefficient on the stability of the system are analyzed. This study establishes a bridge between micro contact and macro system vibration analysis, which can be used to establish the dynamic model of similar bolted connection system in engineering.