Advanced Materials Research Vols. 291-294

Abstract: According to the optimization problem of the cooling channels a conventional journal bearing, the thermohydrodynamic(THD) mathematical model of the journal bearing was set up and the numerical solution was done combined with ANSYS. Considering the effects of the internal cooling channels in the pad on controlling the working temperature effectively by convection, the narrow space in the pad was made full use to form network type internal cooling channels in the pad. The calculation model set up in this paper was then applied to the THD analysis of the original and the improved journal bearing models. The obtained results show that the working temperature of the pad is obviously improved by the internal cooling channels. And then the working temperature of the pad under different convective heat transfer coefficients were studied. It was found that the overall working temperature on the inside surface of the pad decline significantly with an average decline 2 ~ 3°C, as the convective heat transfer coefficient of the internal cooling channels is strengthened from 200W/m²·K to 500W/m²·K.

Abstract: Ducted propeller is a normal thrust used widely in ship field, and the traditional design method could be improved by advanced computer technology of integrated design. Surface panel method predicting hydrodynamic performance of propeller and CFD were both used here, to ensure the results from surface panel method were believable. Surface panel program of ducted propeller was integrated in iSIGHT optimization platform, where the pitches in different radius were optimized and studied to find the best scheme. Design of experiment was selected as optimal method. Design variables were auto-chosen in the design space and optimal process was auto-executed. Besides, the effect of parameters to objective was gained. The final result showed that this method which can improve the efficiency of ducted propeller and realize the motivation provided a new idea for propeller design.

Abstract: Power electronic modules including insulated gate bipolar transistor (IGBT) are widely used in the field of power converter application. The temperature distribution inside these modules becomes more important for electrical characteristics, reliability and lifetime of integrated power electronic modules. In this paper, a seven-layer compact RC thermal component network model based on the physical structure is presented. A dynamic electro-thermal model, which is composed of electrical model, compact RC thermal component network model and electro-thermal interface is developed for the IGBT. These models interact with each other to calculate the temperature of each layer of module and parameters of each model. The thermal model determines the evolution of the temperature distribution within the thermal network and thus determines the instantaneous junction temperature used by the electrical model. Such built dynamic electro-thermal simulation methodology is implemented in the Saber circuit simulator, and the simulation result is validated by the experimental study, which adopted with infrared thermal imaging camera. The built dynamic electro-thermal model could be helpful for the research on operation performance and heat sink design for such power electronic devices.

Abstract: In the die manufacturing process of ceramic extrusion die, the residual stress was produced resulted from the thermal expansion coefficient mismatch between ceramic die and die core of graphite. As a result, the longitudinal cracks were formed in the ceramic extrusion die. The thermal residual stress formed in the cooling process was analyzed by finite element simulation method. The result indicated that the thermal expansion coefficient was the primary factor which could affect the tensile stress of ceramic extrusion die. Then, the thermal expansion coefficient, elastic modulus and poisson's ratio of ceramic extrusion die material were selected as design variables, and the largest tensile stress that less than allowable stress of ceramic die material was determined as the objective function, the material component were optimized according to the finite element simulation. The longitudinal cracks were eventually avoided.

Abstract: The body heat transfer coefficient of a railway vehicle is an essential parameter for designing vehicle. The proposed method in this paper could be used to simulate the test conditions of body heat transfer coefficient of a railway vehicle. The simulated object was a middle of high speed train and the numerical simulation was two-dimensional due to the limitation of RAM capacity of PC computers. Simulation results with five different meshing showed body heat transfer coefficient was affected greatly by the amount of grids. Existence of thermal bridge would increase body heat transfer coefficient significantly, which was concluded by the simulation of two models. Three typical cross sections of a middle were used for simulation of the body heat transfer coefficient and the weighted mean value was 1.30 W/m2•K. The difference was only 7% compared with the actual test value of 1.215 W/m2•K, which indicated the advantage of this method.

Abstract: Although particle reinforced metal matrix composites possess excellent physical properties, its machining performance is rather bad because of its specific structure. It is difficult to obtain good cutting effect by traditional machining method. So machining has become the bottleneck which strictly restricts its industry application. This paper mainly focuses on both wear characteristics of different tool materials and material removal mechanism in ultrasonic milling high volume fraction particle reinforced metal matrix composites SiCp/Al. An acoustic device for ultrasonic vibration milling was developed to introduce the ultrasonic vibration into the traditional machining process. Through the contrast experiment of traditional milling and ultrasonic vibration milling SiCp/Al, the mechanism of tool wear and characteristics of surface topography were analyzed. The experimental results showed that the surface integrity and tool life in the ultrasonic vibration milling SiCp/Al were improved. This template explains and demonstrates how to prepare your camera-ready paper for Trans Tech Publications. The best is to read these instructions and follow the outline of this text.

Abstract: Nanoscratch tests showing clear ploughing behavior and stable chip formation was conducted to investigate the influence of friction coefficient on the minimum thickness of cut. A theoretical model accounting for the minimum thickness of cut is used to analyze the effects of the friction coefficient and force ratio. Results show that the minimum thickness of cut is strongly dependent on both friction coefficient and force ratio. Theoretical minimum thickness of cut can be obtained when adhesion friction plays a dominant role in the cutting process. Appropriate adjustments of processing parameters are hereby suggested to result in stable micro-machining process without ploughing, not only forming fine-thin continuous chip, but also achieving high surface quality. The role of friction coefficient on the minimum thickness of cut with δ (cutting depth/edge radius) is also discussed.

Abstract: The optical surface defects have a significant impact on functions and reliability of the whole optical system. In recent years, with the great attention on research of large-scale high-power solid-state laser device at home and abroad, the detection of optical surface defect has also been highly valued. Through continuous exploration, defect detection technology has made some achievements, but there are still some urgent technical problems to be solved. In this paper, the technology situation of optical surface defect will be summarized in two aspects: the surface cleanliness and surface flaws. Moreover, the technical difficulties and the problems which are currently facing will be analysis.

Abstract: Miniaturization of all kinds of industrial product is a direction of development. Micro processing is the foundation of making the product miniaturization. This paper introduces the basic concept, technology level and main using ways of micro processing.

Abstract: Rare earth metals are an important strategic resource. Due to scarce reserves, and large consumer demand, it is facing the crisis of resource depletion. Marine are the largest deposits sites in the world. In the long growth history, marine autogenic sedimentary mineral, such as polymetallic nodules, crusts with large quantities, not only contain the enrichment of Mn, Fe, Co, Cu, Ni and other valuable metals, but also contain extremely rare earth elements (REE) in the crust. Thus, in the process of developing marine mineral resources, Mn, Fe, Co, Cu, Ni and other metals are used, while it is possible for the development and utilization of the associated rare earth mineral. Marine may become a new field of rare earth resources development.