The classical theory of centralized dynamic characteristics with eight coefficients is adopted for traditional journal bearings. However, under cantilevered load, distributed dynamic characteristics along the axial direction will be generated for the journal bearing with a large aspect ratio (L/D). A double-section loading method simulating shaft bending and excitation was developed, a dynamic characteristic test-rig of a large-aspect-ratio bearing was set-up, the novel four-time vertical excitation method and eight-time cross excitation method were put forward, and the equations of 16 dynamic characteristic coefficients of the bearing were deduced. The dynamic characteristic test was carried out. The results showed that the four-time vertical excitation method had a small response amplitude in the horizontal direction, and was vulnerable to interference by the vibration of the test-rig. The eight-time cross excitation method had a higher SNR with more accurate identification results. When the cantilevered load was not applied, the dynamic characteristic coefficients were evenly distributed along the axial direction, the stiffness coefficients fluctuated slightly as the rotation rate increased, while the main damping coefficients decreased significantly. Shaft bending resulted in a significant increase in local dynamic characteristic coefficients, in which the relative increase in the stiffness coefficients was greater than that of the damping coefficients. Increasing the rotational speed can weaken the effect of shaft bending, and key factors that cause the axially nonuniform distribution of dynamic characteristic coefficients of the bearing are shaft bending and large aspect ratio under low speed and cantilevered load.

Under low speed and heavy load operating conditions, the marine water-lubricated bearing (WLB) is often in a mixed lubrication state. This leads to abnormal friction-induced vibrations and noise in underwater vehicles. An empirical mode decomposition (EMD) based method for identifying friction-induced vibration characteristics of WLB was proposed, and friction-induced vibration experiments of WLB were carried out. The results showed that the specific pressure and lubricant temperature significantly affected friction-induced vibrations while the cooling water flow hardly had an effect. Studying the monotonicity of the eigenvalues of IMF energy, time-domain standard deviation, bias angle, and center of gravity frequency can visualize the trend of the bearing friction-induced vibration signals. Among them, the critical point of friction-induced vibrations could be analyzed by the inflection point of IMF energy, standard deviation, bias angle, and the sudden increase of the center of gravity frequency. The study results were valuable for revealing the friction-induced vibration mechanism of WLB and providing an important reference for design optimization.