No abstract available

[en] We investigated the dynamic behavior of planar mechanical systems with clearance joints. First, the contact effect in clearance joint was studied using a new nonlinear contact force model, and the rationality of this model was verified by the results of numerical simulations, which are based on a journal and bearing contact model. Then, the dynamic characteristics of a planar slider-crank mechanism with clearance were analyzed based on the new nonlinear contact force model, and the friction effect of clearance joint was also considered using modified Coulomb friction model. Finally, the numerical results of the influence of clearance size on the acceleration of slider are presented, and compared with the published experimental results. The numerical and experimental results show that the new nonlinear contact force model presented in this paper is an effective method to predict the dynamic behavior of planar mechanical system with clearance joints, and appears to be suitable for a wide range of impact situations, especially with low coefficient of restitution

[en] A type of pivot is described which acts as both a bearing and an end stop. The pivot avoids any mechanical contact between the moving and stationary parts, and operates with practically no friction and thus no wear. (orig.)

[en] Hydrodynamic-type gas journal bearings with stabilising venting slots are often operated hydrostatically during starting-up as a means of 'jacking'. A simplified mathematical treatment of the circumferential gas flows in a vented, pressure-fed journal bearing is used to predict the relationship between load capacity, bearing geometry and gas properties. (author)

[en] The use of long shaft vertical pumps is common practice in the nuclear waste processing industry. Unfortunately, when such pumps employ plain cylindrical journal bearings, they tend to suffer from rotordynamic instability problems due to the inherent lightly-loaded condition that the vertical orientation places on the bearings. This paper describes a case study in which the authors utilized rotordynamic analysis and experimental vibration analysis to diagnose such a problem and designed replacement tilting-pad bearings to solve the problem

[en] This paper investigated the eccentricity ratio, relative clearance, and length to diameter ratio under different load carrying capacities and journal rotation speeds, aiming to provide design reference of eccentricity ratio, relative clearance, and length to diameter ratio in water-lubricated bearing design process. The computer fluid dynamics was adopted to analyze eccentricity ratio, relative clearance, and length to diameter ratio of water-lubricated bearing. The cavitation effect of water was considered in the analysis. The simulation results of eccentricity ratio were verified by experiments. In different journal rotation speeds, the relative clearance had little influence on the maximum water film pressure and load carrying capacity. The numerical number of maximum water film pressure and load carrying capacity was in a small range. Designing chart of eccentricity ratio, relative clearance, and length to diameter ratio was provided. (paper)

[en] The research aims to develop new materials which could be a reasonable substitution to the metallic materials in the bearing systems. The tribological properties of epoxy composites containing 0, 0.2, 0.4, 0.6, 0.8 wt% contents of carbon nano-fibers (CNFs) have been investigated. The experimental results revealed that epoxy composites containing 0.4 wt% CNFs showed the minimum friction coefficient and reasonable wear resistance. This behavior was referred to the formation of CNFs enriched lubricating film. The lubricating film acts as a protective shield from the severe wear and provides a lower conjunction intermediate layer facilitating the slipping of the rubbing surfaces. Increasing the CNFs contents up to 0.8 wt% has an inverse effect on the friction coefficient despite the sharp increase in the wear resistance. (paper)

[en] The paper describes experimental work that demonstrates the use of repetitive control to attenuate radial vibrations of a variable speed-rotor. The experiments were performed on a rotor test rig having a 3-kg rotor supported by journal bearings. The first bending resonance of the rotor shaft (i.e. the critical speed) was approximately 50 Hz. The objective was to control the radial response at the rotor midpoint by using an actuator located outside the bearing span. A novel aspect of the controller design is that the length of the control output vector of the repetitive controller was updated as a function of the speed of rotation. The speed of rotation determined the required delay time and the repetitive filter length that approximately matches with the delay time. The results obtained were comparable to those achieved in earlier studies with feed forward compensation methods. The best results were achieved when the frequency of rotation enables an integer ratio between disturbance period and sample rate

[en] The wear resistance of Babbitt is used to improve anti-adhesion to the journal surface as bearing bushing in the industrial application. But the coarse grain and heterogeneous microstructure lead to reduce anti-wear of Babbitt at room temperature and elevated temperature. Therefore, it is important to improve wear resistance of Babbitt by refining grain. In this study, Bare Babbitt surface was conducted by laser remelting treatment (marked by the laser Babbitt). Compared with Bare Babbitt, the friction and wear performance of laser Babbitt was conducted by a ball-on-disc tester under lubricated condition at wear temperature of 25 °C–100 °C. The results showed that the microstructure of Babbitt alloy surface laser-remelted was homogeneous. Particularly, the SnSb intermetallic was refined after laser remelting treatment. The microhardness of laser Babbitt is higher than that of Bare Babbitt at different temperature. Wear resistance of laser Babbitt is higher than that of Bare Babbitt under different temperature. (paper)

[en] The paper investigated performance of air bearing system in a micro device. A parametric study is carried out. The dynamic performance of a very short journal bearing (L/D < 0.1) and thrust bearing is studied. The parameters that affect the performance of the air bearing are discussed. The optimum values of the important parameters are explored, and the stability of the thrust bearing is discussed. The prototype and test result are presented