Nonlinear dynamic behavior of a water-lubricated hybrid bearing-rotor system
In this study, the stability analysis is carried out on a water-lubricated hybrid bearings used as the support of a high-speed motorized spindle. A two-dimension finite element method considering turbulence effect has been developed to solve the nonlinear oil film force. This paper mainly studies the influence of the water supply pressure, rotating speed, and unbalance mass on the axis orbit of the rotor-bearing system. The results of the axis orbit indicate that the effect of nonlinear for the hybrid bearing studied in this paper is not obvious, and the bearing-rotor system can run safely and stably at the rotating speed not more than 30000 rpm.
Experimental analysis on friction-induced vibration of water-lubricated bearings in a submarine propulsion system
Abstract Abnormal vibration and noise, originated from friction and wear, are often found in water-lubricated stern-tube bearings, which seriously threatens the safety and concealment of underwater vehicles. In order to better understand the friction-induced vibration in water-lubricated stern-tube bearings, friction pairs of rubber specimens matched with ZQSn10-2 brass were tested on the water-lubricated bearing test rig SBB-100. A high-speed camera was used to track the micro images that focused on of the rubber layer vibration motion, while a machine vision technique also was employed to extract the friction-induced vibration of the test bearings. The experimental analysis results demonstrate that the bearing vibration was mainly induced by stick-slip. Furthermore, the orthogonal experiment method was used to distinguish the key factors that induce the bearing vibration among rotating speed, contact pressure, rubber layer hardness and thickness, and lubrication condition. The analysis results indicate that the importance of factors is sorted in the order of lubrication condition, contact pressure, hardness and thickness of rubber layers. In normal lubrication condition, the intensity of friction-induced vibration of the rubber bearings can be reduced by increasing the hardness of the rubber layer, decreasing the contact pressure, and the thickness of the rubber layer.
Cooperative Collection Development
The author discusses cooperative collection development from an historical perspective and examines some of the projects conceived and implemented during the past forty years. In many cases the projects failed even after years of concentrated effort. However, more important than these failures are new efforts that are being made. The major focus of this article is on both current regional projects and the more broadly based ARL-sponsored North American Collections Inventory Project. The author discusses these efforts and offers some specific judgments regarding the possibility that these projects will lead to a truly successful coordinated collection development project on a national basis.