In this paper, a pedestal looseness fault model of a rotor-bearing-seal system is established. Under two working conditions of the same direction eccentricity (Working Condition 1) and reverse eccentricity (Working Condition 2), rotor orbits, vibration waveforms, spectrum cascade, and Poincaré maps are used to study the dynamic characteristics of the system when the sliding bearing support is loosened. The influence of speed, the unbalance of two discs, the looseness clearance, and the mass of bearing support on system characteristics are analyzed. The study found that Working Condition 2 is more likely to cause looseness of the bearing support. Moreover, for the rotor system in this paper, the pedestal looseness fault is more likely to occur near the second-order critical speed. Through analysis of the spectrum, it is found that the spectrum of the looseness fault will show multiple frequencies or continuous spectra, and the rotor orbits will appear “cylindrical.”

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This paper analyzed the effects of boundary conditions on the stress distribution of hydraulic support with the static finite element (FE) model. Five loading conditions are considered in this study, including: 1) canopy torsional loading, 2) canopy eccentric loading, 3) base torsional loading, 4) base diagonal loading, and 5) base symmetrical loading. In order to verify the simulation results obtained from the FE model, the corresponding experiments have also been performed. Based on the comparison between simulation and experimental results, the effects of pin-joint simplified methods and boundary conditions are evaluated in terms of accuracy and efficiency. Moreover, the new elastic-support boundary is also proposed to improve the simulation accuracy under conditions 2, 3, 4, and 5. The results show that bonded contact between the pin and shaft hole has high efficiency and accuracy compared with the frictional contact. The frictional contact boundary is reasonable under condition 1. However, the elastic-support boundary is suggested to be adopted to improve calculation accuracy for the stress distribution of the constraint components (canopy or base) under conditions 2, 3, 4, and 5.

The output flow pulsation characteristics of the hydraulic pump due to the structural characteristics may cause pump source fluid pressure pulsation and even cause the equipment to vibrate, which will affect the life and working reliability of the equipment. Scholars have done a lot of theoretical and simulation analysis on the characteristics of fluid flow and pressure pulsation caused by the specific structure and structure of the plunger pump, but there are few comparisons and analyses of the simplified model of the plunger pump and the pressure pulsation characteristics with experiments. In this paper, AMESim software is utilized to establish a simplified model of one seven-plunger hydraulic pump, and simulate and analyze the pump source fluid pressure pulsation characteristics of different system load pressures at a constant speed. An experimental platform for testing pump fluid pressure pulsation was designed and built, and the actual measurement and simulation results of pump fluid pressure pulsation were compared and analyzed. The results show that the system simulation data is in good agreement with the measured data, which verifies the correctness of the simplified model of the plunger pump. At the same time, it is found that the fluid pressure pulsation of the pump source exhibits broadband and multi-harmonic characteristics. At a constant speed, as the load pressure of the hydraulic system increases, the pump source fluid pressure pulsation amplitude increases, the pressure pulsation rate decreases, and the impact on the fundamental frequency amplitude is the most significant. The research results can provide a theoretical basis for suppressing the pressure pulsation of the pump source fluid and reducing the vibration response of a hydraulic pipeline under the action of the pulsating harmonic excitation.