Applied Mechanics and Materials Vols. 190-191

Abstract: The paper considers the effect of lubricant viscosity, ν, on the contact fatigue life, N, in gearing applications. More than 40 sets of the thermal non-Newtonian EHL numerical calculations and six sets of disc fatigue tests under the conditions ranging from the mixed to full film lubrication are used. The results show that for improving gearing fatigue life it is generally useful to increase lubricant viscosity. But it is not simply the case that the higher the lubricant viscosity, the better. When lubricant viscosity, ν, is less than a critical value, νcr, a quantitative relation of is seen in the test results; When ν > νcr, however, increasing lubricant viscosity is found to reduce the fatigue life. Based on this result, the paper raises questions concerning the accuracy of the lubrication factor recommended by ISO/6336:1996.

Abstract: An axial symmetric invariable temperature phase change interface model is established to investigate numerically the effect of mass flow rate of working fluid on performance of capillary porous wick evaporator with bayonet tube for alkali metal thermal-to-electric converter (AMTEC) system. The numerical results reveal that the temperature of working fluid in the wick and liquid channel decreases with increasing the mass flow rate. The suitable structure of bayonet tube is dependent on the mass flow rate of working fluid. The bayonet tube having larger wall thermal resistance is selected for the smaller mass flow rate of working fluid, and vice versa. Also, the flow in the liquid channel is greatly affected by the mass flow rate of working fluid in comparison with the capillary porous wick evaporator without bayonet tube.

Abstract: In this paper, the effects of Sb addition on heat-treated microstructure and mechanical properties of AZ61-0.7Si magnesium alloy were investigated. The results indicate that the solution heat treatment can modify the Chinese script shaped Mg2Si phase in the AZ61-0.7Si alloy. After solutionized at 420°C, the morphology of the Mg2Si phase in the AZ61-0.7Si alloy changes from the Chinese script shape to the short pole and block shapes, and the higher modification efficiency could be obtained for the alloy with the addition of 0.4 wt.%Sb. In addition, the effect of the solution heat treatment on the morphology of the Mg2Si phase can also result in the improvement of tensile and creep properties for the AZ61-0.7Si alloy. After solutionized at 420°C for 24h and followed by aging treatment at 200°C for 12h, the AZ61-0.7Si alloy exhibits higher tensile and creep properties than that of the as-cast alloy, and the properties improvement resulted from heat treatment, is more obvious for the AZ61-0.7Si alloy with the addition of 0.4 wt.%Sb.

Abstract: During the experiment of cell poking, it is required that the point of a probe is aimed at the cell with the help of a precision motion platform, and then, controlled by this motion platform, the tip of the probe pokes into the cell. When these operations are done, the driving force of this platform will be removed. But within a certain period (for example, an hour), the platform doesn’t stop moving. This kind of movement, which should be only several microns, is termed in this paper as the mechanical drift of ultrasonic linear motors. Experiments show that the forms used for clamping the stator is one of the factors that affect the mechanical drift. It is studied through experiments the impacts of several clamping forms on mechanical drift, the drift value’s relationship with the slide rail’s damping and the motor’s step size, and how the drift direction is related to the motion direction. The mechanism of mechanical drift of ultrasonic linear motors has also been explored preliminarily. This kind of research will facilitate refinements of the design and control methods for ultrasonic linear motor as well as motion platforms.

Abstract: In order to solve the high-price and short- lifetime problem of the cutter of field straw chopper, wear-resistance coating was prepared on the substrate of 45# steel by flame spray-welding NiWC alloy. By means of orthogonal test and multiple factors variance analysis, The process that the test factors influence the wear-resistance was studied. The technology parameters of flame spray-welding NiWC alloy were optimized as follows: coating matching, 65%Ni60+35%WC; preheat temperature, 450 °C; acetylene flow, 1000 L/h; spraying distance,40 mm.

Abstract: The paper researches flow field and temperature field characteristics of one rocket charge with complicated structure by numerical method. The charge, in which there exist the conduction, convection and radiation, consists of the metal shell, seven propellant columns and air gaps. For the reasons, to solve temperature field of the charge is to solve a complex heat transfer problem in a complicated calculation region. A mathematical and physical model for the flow and heat transfer process in the charge is established and unstructured meshes are applied to disperse the complicated calculation region. The SIMPLE algorithm is used to solve the partial differential equations, and the calculation results are in good agreement with the experimental data. On basis of the numerical simulation, the flow field and temperature field characteristics of the charge are researched and subsequently some valuable conclusions are gotten.

Abstract: Based on Donnell’s thin shell theory and basic equations, the wave propagation method is discussed here in detail, which is used to investigate the vibration and sound radiation characteristics of thin finite length circular cylindrical shells and ring stiffened shells under various boundary conditions. The effects of boundary conditions, mode truncation, shell’s length, thickness and rings on the acoustic radiation are explored. It is shown that the wave propagation method is more effective for the long cylindrical shell, and the mode truncation can satisfy the calculation accuracy. The conclusion is drawn that the stiffeners have a great influence on the total mechanical impedance while have a slight influence on radiation impedance. The work will give some guidelines for noise reduction of this kind of shell.

Abstract: Empirical studies on the heat exchange characteristic of the span borderline CO2 of the parallel flow gas cooler in the hol-aluminium microchannel and the surface temperature distribution of the gas cooler during heat exchanging of the span borderline CO2. Through experiments we got the surface temperature distribution of the cooler in the wind. These studies provide evidences for the design of the hol-aluminium mirochannel parallel flow gas cooler in the carbon dioxide automobile air conditioning system.

Abstract: In the paper, with the change of the relation between the Bond numbers and 1/3, the different control equations with different dispersion item was obtained for the surface wave of film under uneven bottom. The equation under tension and bottom was reduced from the potential flow theory with the little parameter perturbation technique, and then was solved by using the numerical method. The waterfall of the surface wave was simulated with Matlab software. The results show that different surface tension and different bottom has different effect on the film surface.

Abstract: The application of natural refrigerant CO2 is of great significance to reduce the greenhouse effect and ozone depletion. Transcritical CO2 heat pump cycle is presently an important aspect of natural refrigerant alternatives research. In this paper, a vortex tube expansion transcritical CO2 heat pump cycle is established and compared to that of the transcritical CO2 refrigeration cycle with throttle valve. Thermodynamic analysis results indicate that the system performance of vortex tube expansion transcritical CO2 heat pump cycle is better than the transcritical CO2 heat pump cycle with throttle valve, and the COPh improvement is 5.8%~13.9% at given conditions. The gas-cooler outlet temperature has a great impact on the system performance, there is a higher COPh improvement when the cycle at lower evaporation temperature or higher gas-cooler outlet temperature.