Explicit finite element modeling method and the impact energy propagating characteristics of the rotor with blade off

The explicit finite element (FE) simulation method of the flexible rotor with fan blade off (FBO) is developed using LS-DYNA. Three important aspects of the model processing have been discussed, including the setting of blade off and rotational speed, simulation method of bearings, and solution time reduction technologies. An inner cross method is developed to simulate the elastic bearings, which can effectively avoid the problems of the existing simulation methods. Based on the established explicit FE model, the dynamic response, stress distribution characteristics, and impact energy propagation of the shaft are studied after the FBO fault occurs. The numerical results show that the impact energy of the missing blade does not propagate as a wave in the rotating shaft, which is different from the non-rotating beam. The gyroscopic effect can inhibit the typical wave propagation characteristics of impact energy. The bending moment of the rotating shaft is determined by both the gyroscopic moment and the unbalanced load, while the unbalanced load is the dominant factor. Finally, it is analyzed that key factors such as rotational speed, unbalance, and the constraints of fusing structure and fan casing have different effects on the dynamic response of the rotor. The energy concentration phenomenon and the amplification effect of reaction force appear in the rotor with blade off.