유한요소 해석 기반 RK4 회전체 시스템의 이상상태 해석 및 검증

This paper represents the rotordynamic finite element (FE) analysis for a RK4 rotor kit system with abnormal conditions such as unbalance and shaft rubbing, which commonly occur in a rotating system, in comparison with experimental results. The rotordynamic FE model for the RK4 system is developed by using the commercial finite element analysis package ANSYS MAPLD. First, its modeling parameters such as material property, bearing stiffness, and the spring constant of the flexible coupling were tuned based on the step-by-step impact hammer test results on the RK4 system. For the unbalance analysis, the system is assumed to rotate with a constant rotating velocity of 3,600 RPM and be vibrated with excitation forces due to unbalance. The shaft rubbing is modeled using the node-to-node contact using the penalty method. Then, transient response analysis is performed for the initial few seconds and then the vibration signals are processed in both time and frequency domains. Results from simulation have a good agreement with those from the experiment in terms of the vibration signal, the orbit, and the FFT response. This method can be used as a substitute or complement when the test of the abnormal state for the rotating system is impossible and very limited.