Advanced Materials Research Vols. 199-200

Abstract: The principle of electromagnetic launch is introduced. The equation of electromagnetic load applied on rails is given. Based on the calculated result of electromagnetic pressure, the equation for calculating bending stress of rail on the elastic foundation is deduced using superposition principle. The stress distribution in rail with the armature in different positions is analyzed. Compared with results considering the force on the rail as uniformed load, the calculating results of stress distribution are more accuracy and useful for intensity and rigidity design of electromagnetic launch. The study may provide a theoretical basis for further analysis of systemic mechanical properties.

Abstract: Because lacking of enough data to define distributions of stress and strength of machine components,it is difficult tocalculate the reliability of the component by aid of numerical integra- tion. This paper explains that, if we knew means and standard deviations of the stress and strength, we can work out reliability coefficient (β), and illustrate the design principle of linear second order moment method by means of the screw design example.

Abstract: This paper investigated the friction and wear behaviors of nylon rubbing against steel discs with helical, parallel and multidirectional textures respectively. The results indicated that friction coefficient, friction temperature and wear rate of couple using helical texture steel disc as counterpart were higher than others. Abrasive wear was the primary mechanism of the three couples. Nylon surface roughness increased after rubbing against helical texture steel disc, but decreased after rubbing against parallel and multidirectional texture steel discs. The roughness of both helical and multidirectional texture steel discs increased slightly after test, while the roughness increase of parallel textual steel disc was significant only at regions perpendicular to the rotating direction due to adhesion of nylon transfer film.

Abstract: Fault diagnosis of roller bearings is very complex, so it is difficult to use the mathematical model to describe their faults. Whose developmental changes have dual trends of increase and fluctuation. In this study, support vector machine trained by genetic algorithm based on high frequency demodulation analysis is proposed to fault diagnosis of ball bearing. Genetic algorithm is used to determine training parameters of support vector machine in this model, which can optimize the support vector machine (SVM) an intelligent diagnostic model. The performance of the GSVM system proposed in this study is evaluated by roller bearings in the wood-wool production device. The experimental results indicate that the proposed support vector machine trained by genetic algorithm has good diagnosis results in the application.

Abstract: Auger mining machine which is used in thin coal seam gets coal by drilling. Its drilling distance always is dozens of meters. Because of the long Drilling distance, the deflection of the drilling tool was produced by deviating force . In order to improve auger mining machine’s preventing deflection character and scope of application, the research on preventing deflection mechanism of auger mining machine combining theoretical analysis and experimental research was carried out on the basis of a simplified drilling tool structure. The studies we have performed showed that: increasing the drilling assembly bending rigidity or the drill pipe weight can prevent deflection; reducing the distance between the drilling stabilizer and drill is another method to reduce amount of deflection.

Abstract: The approach to estimating the life-stress model and the model parameters for X-series hydraulic cylinders was studied, and the theories and statistical methods related to the reliability index under normal stress were reproduced precisely through the accelerated life test. With temperature and velocity as the accelerated stress, the accelerated life test for hydraulic cylinders was implemented, and data acquisition was conducted. Statistication, assessment and transformation were performed on the test data with statistical models related to the theory. The transformation results of the reliability information from the accelerated life test reproduced precisely the reliability index of hydraulic cylinders at the temperature of 308K and the velocity of 0.25m/s (normal stress), and the test period was shortened to one fifth.

Abstract: Oil droplets can break up during flight and form many secondary droplets in an aero-engine bearing chamber due to aerodynamic drag forces. The motion properties of secondary droplets have significant influence on the two-phase oil/air flow phenomena in bearing chambers. In this work, oil droplet trajectories and velocities are developed by accounting for in-flight breakup. The droplet motion is modelled using a Lagrangian tracking method, and the trajectories and velocities are calculated by numerical integration of the oil particle momentum equation with forth-order Runge-Kutta scheme. The trajectories and velocities change abruptly at the breakup location, compared with unconsidering breakup. Subsequently, the effects of operating conditions on oil droplet motions are discussed. The numerical results show that the influence of breakup on oil droplet trajectory and velocity are considered necessarily when simulating two-phase oil/air flows in bearing chambers.

Abstract: The friction and wear behavior of cutting tool materials keeps an issue. In this study, an high temperature tribometre (UMT-2) was used to investigated the tribology properties and mechanism of two kinds of typical cutting tool materials. Commonly used cemented carbide (ZU5) and ceramic (AT) were chosen. The characteristics as to wear rate, friction coefficient and worn surface were studied. From the results, we found that the ceramic had better wear resistance than the cemented carbide. The friction coefficient of cemented carbide decreased with the increase of ambient temperature while the ceramic exhibited an inverse tendency. Finally, the probable wear mechanism was discussed.

Abstract: Porous ultra high molecular weight polyethylene (UHMWPE) materials have been developed by Hot Press molding technique in this investigation. The tribological behaviors of porous UHMWPE with different initial NaCl content were studied. The worn surfaces of UHMWPE and porous UHMWPE samples were examined using a Scanning Electron Microscope (SEM). It was found that the porous structure improved the wear resistance of porous UHMWPE with the proper initial NaCl content under water lubrication condition. The minimal wear loss was about 10.6mg in the case of the UHMWPE filled by 50% initial NaCl content, 43% less than that of pure UHMWPE sample.

Abstract: A heterocyclic derivative of 3-(N-di-n-butylaminomethyl) quinazolin-4-ones was synthesized and its tribological behavior as an ashless additve without phosphorus and sulphur in liquid paraffin was evaluated using a four-ball tester. On the basis of the experimental results, the novel additive has been found to be quite effective as a potential additive in liquid paraffin. The nature of the film on the rubbed surface was investigated by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS).