Applied Mechanics and Materials Vols. 130-134

Abstract: Aiming at researching friction process on the influence of train rolling contact properties between the wheel and rail,using the basic principle of Molecular Dynamics Simulation and Embedded Atomic Method theory,study the areas of adhesion within the contact patch area will gradually increase along with the occurrence of the friction process,research the increase process about the areas of adhesion within the contact patch area by means of Molecular Dynamics simulation model and simulation algorithm.For the study of friction on the surface about changes and micro-dynamic behavior,understanding the influence of the friction process on the train rolling contact characteristics,provides a numerical simulation based on microscopic approaches and methods.The results show that the method is easy to achieve a large time scale,a large number of atoms of the dynamic simulation.

Abstract: Indentation and sliding friction of the as-cast, the relaxed and the crystallized Cu₄₄Zr₄₃Al₁₀Nb₃ bulk metallic glass (BMG) are investigated on nanoscale by nanoindentation. The depth, the width and the morphology of the scratches formed by the tip of the nanoindentor are different, which reflect the differences in structure, not only between the glassy and the crystallized states but also between the two glassy states, the as-cast and the relaxed. The coefficient of sliding friction of Cu₄₄Zr₄₃Al₁₀Nb₃ BMG is increased with increasing the load, and it is maximal for annealed at 683K. Improved plastic deformability is found for the relaxed one.

Abstract: The friction and wear properties of the DLC coatings were evaluated while being lubricated with pure PAG, PAG containing PN and ZDDP using reciprocating ball-on-disk sliding UMT tester, respectively. The morphologies of the worn surfaces of the DLC coatings were observed using a scanning electron microscope (SEM). The results indicated that the DLC coatings exhibited better tribological properties under the lubrication of PAG containing PN or ZDDP than that of pure PAG. In addition, PN and ZDDP as additives show different tribological properties. The former offers better anti-wear ability, the latter offers better friction-reducing properties.

Abstract: Experiments were carried out to learn about the frictional resistance of gas-liquid two-phase flow in vertical helically coiled pipe. The expression of friction factor is established and the formula used to calculate the frictional resistance of gas-liquid two-phase flow in vertical helically coiled pipe is defined based on partial data got from different experiment conditions. The calculating formula was verified by the experimental data and the result indicates that the formula is accurate enough to calculate the frictional resistance of gas-liquid two-phase flow in similar operating conditions.

Abstract: The abrasive wear of 45 steel and HT200 iron which are usually used on agriculture machine was tested by alfalfa powder on a grinding abrasion testing machine. The chemical composition on both wear metal surface and original surface were analysed with energy dispersive spectroscopy (EDS). The results indicated that metal element contents on the metal wear surface were decreased, while the nonmetallic element contents were increased.

Abstract: In order to study the change of the tire surface temperature during tire running, tire surface temperature experiments were made with the automobile rotary drum, the thermovision infrared equipment etc. Through the tests we got the temperature distribution of the tire surface during the tire rolling and after the tire stopped. Then the temperature distribution is analyzed.

Abstract: Based on chaotic oscillator system and wavelet transform system, this paper proposes a novel method on high frequency weak signal detection. Chaotic system is a typical non-linear system which is sensitive to certain signals and immune to noise at the same time. Its properties demonstrate the potential application on weak signal detection. Due to the good localization in both time domain and frequency domain, the wavelet transform method can automatically adjust to different frequency components and increase the Signal-to-Noise Ratio. Starting from the analysis of advantages and disadvantages of two signal detection methods, we put forward a combined method that takes advantage of each method to detect weak signals with high frequency. The simulation results show that the novel method can detect weak signals with frequency in an order of magnitude of 10⁷Hz, and the input Signal-to-Noise Ratio threshold could be-42.5dB.

Abstract: A new method-mixed boundary grid method (FBGM) is proposed to analyze the free vibration of cantilever plates with variable thickness. The fundamental differential equations of the plate are established for the bending problem. By transforming these equations into integral equations in a small area and using the trapezoidal rule of the approximate numerical integration, the solution of these equations is obtained and chosen as Green function to obtain the characteristic equation of the free vibration. The accuracy of the numerical results for the natural frequency parameter calculated by the proposed method is investigated.

Abstract: With the structure of permanent magnet (PM) spring, composed of one fixed end magnet and one moving magnet, a nonlinear resonant electromagnetic generator is designed for harvesting energy from human wrist by vertical shaking, which can be used as an emergency power source for portable electronic products, such as cell phone. The magnetic field distribution is analyzed by finite element method (FEM). Generator model is built under no-load condition and the parasitic damping factor is evaluated indirectly. The model is amended through reasonable hypothesis of collision and validated by the measured results, which can be used for further with-load analysis and generator optimization.

Abstract: Aimed at the longitudinal vibration of rope hoisting system with time-varying length, the governing equations are developed employing the Hamilton’s principle considering mutual influence of the rigid motion and deformation of rope. The Galerkin’s method is used to discretize the governing equations. In the mean time, The motions of elevator hoisting system were illustrated to evaluate the proposed mathematical models. The results of simulation show that the modeling methods can represent the longitudinal vibration of rope hoisting system with time-varying length in the paper. The governing equations derived can provide guidelines for further study on flexible hoisting system.