Key Engineering Materials Vol. 693

Abstract: The meshing efficiency of helical gear transmission is calculated by using the method of double integral. The external involute helical gear meshing is taken and the model of helical gears is simplified by the idea of differential. The instantaneous efficiency equation of a meshing point is derived, and further more the rectangular coordinate system of meshing zone of helical gears is established. The average meshing efficiency of helical gears is achieved by using double integral method. Then, the influence of design parameters is studied and the efficiency formula is verified by comparing the theoretical results with relevant experimental data, which can provide a theoretical basis for decide the design parameters.

Abstract: The paper deals with a noise prediction method for circular saw blades by introduction of FEM and BEM. The mathematical model of noise radiation field of circular saw blade is built firstly. Through the model, the vibration characteristic of circular saw blades within a certain frequency range can be calculated and analyzed based on harmonic response. The distributions of surface vibration velocity at a particular frequency are obtained. The above result files are input into the BEM model, acoustic pressure and radiation efficiency on every node are calculated, the distributions of noise was obtained in the acoustic field. Simultaneously, the effect of sandwich structure on noise is evaluated based on the above co-simulation method. Finally, an experiment is used to test the vibration and radiation noise of common and sandwich circular saw blade. Comparison analysis shows that the simulation results are in good agreement with the data of experiment tests.

Abstract: The dynamic characteristic is one of the important indicators which determine the performance of a machine tool, in this paper, the finite element model of a plane grinder is established with consideration of the behavior of joint, the static dynamic characteristics of machine tools are analyzed to reveal the vibration weak link, the column structure is topology optimized and redesigned based on the variable density degradation method. Static and dynamic characteristics of the original and new column are compared, and the dynamic characteristics of the machine tool before and after modification are discussed. The results indicate that the static and dynamic characteristics of the plane grinder are all improved after optimization.

Abstract: Weathering performance of PV modules is an important indicator of the solar cell module reliability. By conducting hydrothermal aging test for a group of double-glazed modules according to IEC612165 standard (terrestrial solar modules environmental test method) in this paper, the leakage test data and power test data of modules can be drawn after hydrothermal test. Results of the test show that: modules occurs partial delamination after hydrothermal aging test, but did not appear serious appearance defects specified in IEC61215 and power loss is within the allowable range, and all of these have certain value for reference to mass production of modules.

Abstract: Duck wave energy converter has the advantages of high conversion efficiency, simple construction, low cost relative to other wave power device. In the paper, the numerical simulation of the response of the converter was calculated by the AQWA software which based on the three dimensional potential flow theories. The results show that the pitch angle appear the peak when the incident wave frequency is 1rad/s and the maximum of the pitch angle come out as the linear wave normally incident the duck body, which means duck wave energy converter can absorb more wave energy in this angular frequency. The above research can provide reference for the design of the duck wave energy converter.

Abstract: The goal of this research is to investigate cratered hole geometries on film cooling performance. Five kinds of cratered holes, namely, the concentric crater, the circular crater, the downstream offset crater, the upstream offset crater, and the direct crater are being studied along with the conventional flush hole. All craters has the same depth of 0.5 hole diameter. Through numerical simulation with CFX at a single blowing ratio of 0.5 and Reynold number of 11000, we analyze and compare the performance and behavior of five kinds of cratered holes with the conventional cylindrical hole. The simulation employs k-ε turbulent model and wall function. Film cooling effectiveness is achieved for all cases. Among all cases, concentric cratered hole perform the best which increases averaged film cooling effectiveness by 64% at X/D=5.35. All cratered holes appear some performance improvement compared to the baseline case. For cratered holes, film lateral convergence and stream-wise attaching performance was both enhanced owing to the expansional configuration of the crater and the consequent backflow region.

Abstract: In order to study color offset of the high-power white light and blue light LED in the whole life, a series of high-power white light and blue light emitting diodes are lighted continuously under a constant current. In the light of different period of time, measured the light emitting diode emission spectrum, color coordinate, color temperature of the light emitting diodes are measured at different periods; light luminous flux, color coordinate and color temperature changes are also measured under different currents. The experimental results show that the color of LED is different at different period under the same current, and is also different under a variable current. The article studied the influence of different factors on the color offset, and pointed out that the high-power LED color offset is caused by not only phosphors aging but also more major changes of the material itself. Furthermore, the results will provide a reference to the application of white LED and for the further study.

Abstract: s The longitudinal impact between rigid body and variable cross-section elastic rod with fixed boundary condition was studied, the velocity and stress distribution law during 1st impact wave period was derived for the variable cross-section rod, the influence of cross-section change rate on rod response was discussed. Some examples calculations were carried on, It is shown that the cross-section change rate is a significant influencing factor for the velocity and stress distribution in the rod during impact.

Abstract: A certain type of special computer was studied as the institute in this paper. Through researching on the structure of the special computer box, use the Pro/E software to create the simplified model of the case, including computer cabinet, PCB, power and fan etc. Model analysis is conducted in the FEA environment ANSYS, attains ten order natural frequency and vibration mode. Dynamic load in the model is applied with half sine impact acceleration, and the resistance performance of the PCB which is the important components of the model is researched by the acceleration, speed and displacement response results obtained. Verify the installation method of vibration isolator can effectively improve the shock resistance of special computer.

Abstract: Due to obtain good mechanical properties and cost savings etc. composite roll is widely used in rolling steel industry. It is important significance for composite roll interference fit to study because assembly interference fit between roller sleeve and mandrel affect directly the performance of composite roll. In paper the calculation format of interference fit is obtained by deriving theoretically the interference fit process of composite rollers roller sleeve and mandrel. At the same time, the numerical calculation of the maximum amount of interference between roller sleeve and mandrel is done by finite element method, the results show that the theoretical calculation and finite element calculation are basically consistent, thus provide a theoretical and design for composite roll designer and has important practical value.