Papers by Author: Yu Hou Wu

Abstract: The zirconia parts are limited by machined surface quality. The grinding force is one of the most important parameters of grinding and has effects on surface quality. The MK2710 grinder and resin bond diamond wheels were used in zirconia grinding. The grinding force was obtained by Kistler dynamometer. The paper focused on wheel speed and grain size on grinding force, and examined the surface by SEM. The research results indicated that decreasing the grain size, the grinding force increased and the surface quality improved, and increasing wheel speed could decrease grinding force to improve grinding surface quality. The results can improve zirconia ceramic parts surface quality and promote application.

Abstract: The column of heavy double turret five-axis horizontal milling complex machining center is taken as the object of study. Solidworks is used to establish three-dimensional model of milling machining center column, the established modal is be imported into ANSYS Workbench for static and dynamic characteristics analysis. First, by comparing the column deformation, the stress and strain under no-load and load conditions, which is concluded that column design is too conservative and be optimized. Secondly, the modal analysis was carried out on the column, which provides a theoretical basis for the optimization of the column by getting the first six natural frequencies and mode shapes of cloud.

Abstract: To meet the urgent demand of maintenance and lifting equipment for wind turbine, combined with designation demand, two kinds of primary structure of the maintenance and lifting equipment has been proposed, analyzed and compared. By means of the Solid Works software the initial design on the two kind of the machine, the self-climbing crane and the trailed hoisting platform, have been conducted, the static analysis has been performed based on the mechanics model, and the advantages and disadvantages of these methods have been pointed out and compared in the paper. Compared with the self-climbing crane, the mechanical structure of the trailed hoisting platform is simpler, the control system presented more reliable, simple, easier realized etc, and the cost is lower. The self-climbing crane is high-automatic, but the design of crane high in the free degree and high in difficulty, and the climbing force focused on the wind turbine tower is too large. Conclusion The trailed hoisting platform is determined as the main design method to design the maintenance and lifting equipment for wind turbine.

Abstract: In this paper, we have presented a method to generate efficient NC tool paths based on the surface subdivision. The main objective is to achieve high efficiency in the machining of sculptured surface. The NC machining efficiency can be improved by segmenting the whole surface into distinct areas according to the characters of sculptured surface and by using different size mills and different tool path planning methods to machine the areas. The iso-parametric method and large mills are used in the curvature changing little areas. While the iso-scallop method and small mills are used in curvatures changing large areas. This can make full use of tool path generation methods and mills, which improve the machining efficiency of sculpture effectively.

Abstract: The purpose of the essay is to know the rock fragmentation mechanism of TBM and improve the efficiency of disc cutter. The method of simulation is applied. The cutter ring and cutter axis surface stress distribution are studied under different rocks and the change of them is analyzed under different penetrations. Under different rocks conditions, the cutter ring surface stress is affected due to the change of rock load; the same rock condition, it is changed along with the change of penetrations. But the cutter axis surface stress changes little. In different rocks conditions, the change of stress on the cutter ring surface is proportional to rock ultimate stress; the same rock condition, it is proportional to the penetration of the cutter ring. The results are significant in improving the working efficiency of disc cutter.

Abstract: Under the background that modern machine tools have higher requirements to the spindle system, the accuracy, stiffness, critical speed and dynamic stability of the spindle bearing also put forward higher requirements. Traditional steel spindle has been difficult to meet the needs, because of its inherent characteristics. Advanced ceramics have excellent performance, such as low density, low thermal expansion coefficient, high stiffness, wear resistance and good chemical and thermal stability, which can meet the requirements of modern machine tool spindle to the performance of bearing material. The longest fatigue life is the objective function, the calculation method of the ceramic bearing optimal design is the external point method of penalty function, and the all-ceramic bearings without inner rings are successfully manufactured by the advanced manufacturing technology. Finally, the high-speed ceramic motorized spindle prototype was assembled with high precision successfully, and its performance test and analysis were finished, the results show that using the all-ceramic bearing can effectively improve the rotation accuracy and rotational stiffness of the spindle-bearing system.

Abstract: Abstract. Because of the extraordinary physical properties of engineering ceramics such as high hardness, low thermal expansion, light weight and abrasion resistant, it accommodates very well with the high-speed and precision requirements of spindle-bearing unit. In order to prove the superior dynamic characteristic of the all-ceramic spindle-bearing unit bacause of the application of engineering ceramics in shaft and bearing of spindle system, the natural frequency and modes of the all-ceramic spindle-bearing unit were analyzed. In this study, spindle-bearing model was built and analyzed by the Finite Element Method(FEM) and Hertz theory, comprehensively considering both of the stiffness of bearing and the effect of preload, which was different from the tranditional spindle analysis model. The research results show that all-ceramic spindle-bearing unit has higher natural frequency and better dynamic characteristics compare of traditional steel spindle-bearing unit.

Abstract: The article has analyzed the changes of temperature of different materials of the spindle, and considered 170SD30 Ceramic Motorized Spindle and the same model Metal Motorized Spindle as the research objects, analyzed the inside heat source and heat transfer mechanism of the high-speed motorized spindle; used finite element software to set up the model of the motorized spindle, and did simulation and analysis. Verified by simulation, heat transfer rate of ceramic materials is slower than the metallic materials, in actual operation of the process, due to different materials have different heat transfer rate, so the temperature distribution of the different materials of motorized spindle are different. This conclusion provides the basis to solve motorized spindle temperature field distribution.

Abstract: Rock tunnel boring machine is one of the main machineries and equipments for underground engineering, and the failure of tool systems is its main failure form. Rock hob test-bed is the only testing equipment for tool failure and wear. In this paper, the breaking rock by the double disc cutter is simulated and four kinds of rocks are selected to test the influece of rock characteristics and spacing between two disc cutters on the rock breaking by the double disc cutter test-bed. The results show that there is different optimal spacing between two disc cutters for different rock; the optimal spacing is inversely proportional to the hardness of the rocks; the maximum stress appears the boundary between the disc cutter and rock.

Abstract: The increase of loss causes the temperature rise in motor, reducing the using life of spindle, which can seriously affect the performance of motor. Thus, accurate calculating of loss is meaningful to optimal design of electric spindle. In this paper, the losses both with load and without load were analyzed by time-step finite element method. As the result of simulation analysis, the spindle losses with load are higher than those without load. Comparison analysis indicates that losses are various with different load. And the load impacts on core loss mostly in ceramic spindle. In addition, in asynchronous ceramic spindle with 4N•m rated load, the core loss, solid loss and stranded loss are least when the load change from 1.8 N•m to 3.8N•m. Accordingly, the best operation condition under the influence of load in electric spindle is gained.