Applied Mechanics and Materials Vols. 271-272

Abstract: Drum is the core pressure equipment of Natural Circulation Boiler. The harsh working conditions lead drum to be prone to failure in power station boiler system. This article presents a systematic analysis of factors which may cause the failure of the drum and builds the fault tree with the drum failure as the top event. Through calculating each order of minimum cut sets and importance degree of each basic event probability to determine the major influent factors for the failure of drum, this article puts forward the corresponding solutions and brings reference value to safe operation and maintenance of boiler drum.

Abstract: The excessive tool wear always has a great influence on the machining accuracy in micro electrical discharge machining (micro EDM). According to the image processing on the image of tool electrodes, the contour information of the worn tools is obtained, and then the tool wear, especially the tool shape change in micro EDM is studied in this paper. Firstly, the Canny edge detection method is used to extract the outline image of the tool, the scatter points of outline image are curve fitted, and the mathematical description of the tool outline is presented. And then though the mathematical analysis of the fitting function, the tool shape change and tool wear law of micro EDM are analyzed. Finally, according to the curvature changes of fitting curves, the end wear, corner wear and side wear of cylindrical electrode in micro EDM drilling and micro EDM milling, respectively, are divided reasonably based on the analysis, and the amount of each kind of wear is quantitatively estimated.

Abstract: Methods to analysis the DOF(degree of freedom) and singularity of pure serial and pure parallel manipulator, which can not be used to the hybrid manipulator directly, three type of practical topological units and one type of virtual topological unit adopted, Synthesis method of topological dimensionality of the spatial mobility of each topological unit integrated together, architectures of serial-paralle mechanism discussed, also the formula and process of its topological dimensionality of spatial mobility presented, singularity analysis of hybrid mechanism can be carried out based on the forgoing results.

Abstract: Bayesian formula is used to determine diagnosis sequence when several fault trees meet requirements. Bayesian prior probability is usually determined through expert or the user's subjective judgment and historical experience. If there is lack of expert experience, the determination of priori probability is very difficult. A real-time priori probability calculation method is proposed, which needn’t any priori-knowledge and can regulate automatic on the monitoring parameters. It takes into account the multiple diagnosis impact and more flexible than fixed priori probability according application.

Abstract: The method used for measurement and calibration of machine tool errors should be general and efficient. With this method, the machine tool status can be completely identified and its accuracy can be enhanced by software error compensation. The point compensation method can be used as a means for modifying the nominal tool path and on-machine inspection where the machine tool is used as a coordinate measuring machine. The validity of the error calibration method proposed in this' paper was shown using a vertical 3-axis CNC machine with a laser interferometer and a ball bar technique.

Abstract: According to the investment decision-making needs of mining enterprises and incorporated with characteristics of mining equipment investment, fuzzy comprehensive evaluation method has been adopted to determine evaluation factors for mining equipment, analytic hierarchy process and expert evaluation method have been applied for determining relevant parameters, the evaluation model for equipment investment suitable for mining enterprise has been established. The evaluation model has been proved to be correct through verification by examples, and provides a reference for investment decisions of mining equipment selection.