Advanced Materials Research Vols. 291-294

Abstract: In order to investigate the effects of grease lubrication on fretting wear of ball bearings, a series of fretting wear tests were performed under the dry condition and grease lubrication by a self-made fretting wear rig. And tests were completed at different angles, load and number of cycles. The results showed that the grease lubrication can effectively reduce fretting wear; reduction effects increase as the oscillation amplitude increases and load decreases; oxidation in fretting wear decreases as number of cycles increases under grease lubrication; and wear mechanism is diffrent at under different lubrication conditions.

Abstract: (n-octylic acid)-N-quinazolin-4-one methylester was synthesized as potential lubricating oil additive. The friction and wear behaviors of the synthesized compound as an additive in liquid paraffin on 12.7mm diameter steel ball bearing specimen were evaluated with a four-ball machine. The worn surfaces of the steel balls were observed using a scanning electron microscopy and X-ray photoelectron spectroscopy. It was found that the novel compound as an additive in liquid paraffin was effective in improving the tribological performance.

Abstract: A two-disk test rig researching surface damage and ultimate performance of rolling-sliding tribo-parts in extreme conditions is designed. Variable speed (rolling speed up to 83.6m/s, sliding speed up to 16.4m/s) of the rolling/sliding contact are input by motor spindle and regulated with gear. Variable load (Hertzian contact up to 4GPa) is applied with hydraulic cylinder. High temperature (~+300°C) and cryogenic environment(liquid nitrogen) is implemented by changing the lubricant condition. Thermal-stress analysis with ANSYS shows that the temperature and stress of the tester body is reasonable. As the signals judging failure, such parameters as temperature and vibration of the supporting bearing, power consumption of the main spindle, temperature of the tribo-parts surface are monitored in real time. Kingview, PLC, VB and MATLAB software are employed in the online monitoring system to collect data automatically. Types of tribo-parts were tested in the test rig, getting their ultimate performance and the effect of each parameter on surface damage.

Abstract: In his "Contact Mechanics" book, Professor K. L. Johnson described an analytical lower bound shakedown approach to predict the shakedown load limit under repeated Hertz moving surface loads. Based on Bleich-Melan shakedown theorem, this problem will be revisited in this paper using finite element techniques and mathematical programming.

Abstract: Fretting fatigue usually occurs in the structure of aeronautics and astronautics, and accelerates expansion of cracks about the surface of structures. Because of the complexity of the surrounding of aircrafts, the corrosion of aluminum alloy structures is great serious, so the research about the influence of corrosion to fretting fatigue is very important, also the study of multi-site fretting is very significant.

Abstract: For high speed hybrid journal bearing with deep/shallow pockets, film thickness and film Reynolds number vary considerably in different position. Laminar flow and turbulent flow exist simultaneously in the bearing film. This paper establishes the laminar and turbulent mixed film control equations and the pressure boundary conditions together with the restrictor flow equation for a deep/shallow pockets journal hybrid bearing compensated by interior restrictor. The static characteristics such as attitude angle, load carrying capacity, friction power loss and flow volume rate are given by solving the equations with Finite Element Method. By comparing the laminar, turbulent and mixed flow results, it can be seen that the coefficients are proximity under journal speed 5000 rpm (only part of deep pockets is turbulent flow). But the characteristics coefficients of three flow models contrast evidently under journal speed 50000 rpm (deep and shallow pockets are turbulent flow, part of bearing land is laminar flow). Laminar and turbulence mixed flow lubrication theory is more accurate to high speed hybrid bearing with deep/shallow pockets.

Abstract: The influence of DC steady magnetic field on dry-sliding Friction and wear characteristics of friction pair of high-speed steel (HSS) ring and 2Cr13 pin is studied by use of improved MPV-1500 type Friction and wear tester under normal temperature. Experiments show that, The wear loss of both HSS ring and 2Cr13 pin decreases gradually, along with the enhancement of the magnetic field intensity, under the load of 250N and the friction velocity of 0.6m/s; The phenomenon of negative wear loss appears to the HSS ring. The wear loss of the sample HSS ring keeps low comparing with that of the sample 2Cr13 stainless steel pin; The trend of friction coefficients decreases quickly and then slowly; Magnetic field can accelerate oxidization.

Abstract: FeS solid lubrication duplex layer was prepared on the surface of 45 steel by ion nitrocarburizing-ion sulphurizing process. The sulphide grains and holes all in micron and nano scale and distributing equably in the sulphide surface layer with 10 μm thickness of the duplex layer. The duplex layer is composed of FeS, FeS₂ and Fe₃N. Under liquid paraffin oil with 0.1wt% n-Al₂O₃ lubrication, the synergistic effect between n-Al₂O₃ and the duplex layer is produced, and the chemical reaction films including sulphide, sulphate and nitride is formed, which makes the friction factor of the duplex layer keep being the lowest and about 0.07, and the volume loss is reduced by 97% than that of the plain surface(rubbing for 10 min), and reduced by 92% and 21% than that of the sulphurized surface and the nitrocarburized surface, respectively.

Abstract: The variable section influence on the vibration of a simple supported beam under the action of a moving constant concentrated force is investigated in this work. The technique is based on analytical approach with the assumed model method and the numerical approach of Newmark method. Comparisons with the results between vary-section beam and constant-section one indicate that it is a wise approach to economizing materials and lightening the load of gravity by applying vary-section beam on the condition that the maximum stress cannot change dramatically.

Abstract: A new methodology for understanding the construction of dodecahedral links has been developed on the basis of dodecahedron structure and DNA circles. Knots are interlaced cyclic structures while links are at least two cyclic structures mutually interlaced. A new series of DNA dodecahedral links have been given. By assigning an orientation to the links we analyze the knot invariant of these dodecahedral links. This study provides further insight into the molecular design, as well as theoretical characterization of the DNA catenanes.