Reforço estrutural de um moinho vertical de rolos UBE baseado em análise moda

Abstract

Modal analysis aims to obtain natural vibrational characteristics of a structure. It uses total mass and stiffness information to identify natural frequencies and their respective vibration modes, providing essential information for safe design. Vertical cement mills are stimulated by frequencies from different equipment components or external sources and, therefore, must be carefully analyzed. Thus, a finite element simulation of the UBE vertical mill pedestal was performed to determine its natural frequencies and potential resonance risks. For this purpose, 3D CAD software and SolidWorks Simulation 2022 Premium were used, taking the first five vibrational modes. The first mode showed lateral bending with displacement concentrated in the upper part of the pedestal, and its natural frequency (19.813 Hz) was close to the motor's rotation frequency (19.83 Hz). Similarly, the second vibrational mode showed a frequency (38.46 Hz) close to the second harmonic of the reducer's input rotation (39.66 Hz), indicating a resonance risk. Based on these results, geometric and stiffness modifications to the structure were proposed. These included ribs, flange reinforcement, wall thickening, and the addition of plates around the central opening. After the modifications, the first mode exhibited a frequency of 50.62 Hz, moving away from the operational excitation ranges. Subsequent modes, with frequencies of 64.82 Hz, 67.81 Hz, 68.79 Hz, and 76.48 Hz, showed increased overall stiffness and reduced structural displacement. Therefore, the proposed modifications eliminated resonance conditions and improved the dynamic stability of the UBE vertical mill.