SIMULASI NUMERIK PEMODELAN KARAKTERISTIK GETARAN SISTEM POROS BERPUTAR PADA KONDISI KETIDAKSEJAJARAN POROS

Misalignment of rotating shafts is crucial for developing a condition monitoring system. This study aims to simulate the vibration characteristics of rotating shaft systems under misalignment conditions using a numerical approach based on GNU Octave and analyze the vibration response in the time domain, Fast Fourier Transform (FFT), and Power Spectral Density (PSD). The simulation was performed at a rotational speed of 1200 RPM (20 Hz) with a sampling frequency of 1000 Hz for 10 seconds, resulting in 10,000 vibration data samples. The misalignment model was constructed by adding harmonic components at 2× and 3× the rotational frequency to the fundamental component. The simulation results show that the misalignment condition produced a more complex time-domain waveform with vibration amplitude reaching approximately ±1.2, compared with the relatively stable waveform under normal conditions. FFT analysis quantitatively identified the dominant spectral peak at 20 Hz (1× RPM) with an amplitude of 1.000, accompanied by a significant 2× RPM harmonic (40 Hz) at 0.550, and a 3× RPM harmonic (60 Hz) at 0.180. Furthermore, PSD analysis confirmed a clear energy redistribution toward higher harmonics, yielding peak spectral energy values of -4.467 dB/Hz at 1× RPM, -9.668 dB/Hz at 2× RPM, and -19.383 dB/Hz at 3× RPM. These quantitative frequency-domain characteristics demonstrate that the emergence of the 2× RPM and 3× RPM harmonics provides a clear indicator for identifying rotating shaft misalignment. The integrated use of time-domain analysis, FFT, PSD, and rotating shaft animation provides a comprehensive representation of the vibration characteristics associated with shaft misalignment.