Advances in Machining & Manufacturing Technology IX

Volumes 375-376

doi: 10.4028/

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Authors: Bo Zhao, Guo Fu Gao, Yan Wu, Feng Jiao
Abstract: This work mainly studied the deterioration layer structure, crystal grain size, crystal lattice distortion of ground surface in two-dimensional ultrasonic vibration grinding nano-composite ceramics. The research indicated that under a certain grinding condition the ductile deformation layer on the ground surface of nano-composite ceramics in two-dimensional ultrasonic vibration grinding is formed by the ways of material powdering, crystal grain fragmentation, materials extrusion, the crystal grain pull-off and so on. The transition layer between the surface layer and the base body is plastic deformation layer by the primarily ways of crystal lattice distortion and the crystal boundary slipping. The removed material in brittleness fracture mode is extremely few. In this work, the structural model of deterioration layer on ground surface in two-dimensional ultrasonic grinding nano-composite ceramics is put forward. The microscopic deformation mechanism of nano materials is inner grain dislocation of inner-grain-structure strengthened phase. Its deformation coordination mechanism is the the grain-boundary sliding of matrix grain and the coordinated deformation of intercrystalline second-phase. The TEM and SEM observation discovers that the nano particles dispersed in grain boundary stops crack from expanding in nano materials, which causes the materials to appear in transcrystalline fracture behavior. And this fracture behavior gives materials favorable finished surface. The plastic deformation is the dominant removal mechanism of the nano materials in two-dimensional ultrasonic vibration grinding.
Authors: Yong Feng Guo, Ji Cheng Bai, Li Qing Li, Cheng Jun Li
Abstract: Super-capacitors are new equipments for energy storage,and they have wide application in practice. At present, blanking is used to machining the electrodes of super-capacitor; however, the disadvantages of the method are burrs, electrode collapse. A new method processing electrode of super-capacitor, wire electrical discharge machining in gas (dry WEDM), were presented in this paper, and the electrode surface morphologies were studied utilizing scan electron microscope (SEM). First, the surface morphologies comparison studies of super-capacitor electrodes processed with different method, such as shearing, blanking and dry WEDM etc., were performed, and research results show that the super-capacitor electrode surfaces machined by dry WEDM achieve flat machining surface, and electrode edges do not collapse. Further surface morphology analysis was carried out based on different pulse durations and air pressure, and analysis results indicate that better machining surface can be achieved when suitable pulse duration and gas pressure are selected. Finally, surface energy spectrum analysis of the super-capacitor electrode processed by dry WEDM is performed, and the analysis result show that alumina are formed on the middle of electrode, aluminum foil, which is favored to the performance of super-capacitor.
Authors: Zhan Qiang Liu, Peng Zhang, Peng Guo, Xing Ai
Abstract: Surface roughness in a turning operation is affected by a great number of factors. Two of the most important factors are feed rate and the size of the corner radius. Surface roughness can be roughly determined to increase with the square of the feed rate and decrease with increased size of the corner radius. However, wiper insert geometries changed this relationship with the capability to generate good surface roughness at relatively higher feeds by transferring small part of the round insert edges into the straight cutting edges of the pointed insert. The principle of how wiper inserts behave different from conventional inserts as to the effects on the surface roughness is explored in this paper. Experimental study of the surface roughness produced in the turning of hardened mild steels using coated carbide tools with both conventional and wiper inserts is conducted. The test results prove the effectiveness of the wiper inserts in providing excellent surface roughness. The results also suggest that the use of the wiper insert is an effective way that significantly increases cutting efficiency without changing the machined surface roughness in high feed turning operations.
Authors: Feng Lei Li, Wei Xia, Zhao Yao Zhou, Tian Zhang
Abstract: Burnishing, an ultra-precision superficial plastic deformation process, is used increasingly as a surface enhancement finishing treatment after machining operations not only to give a mirror-like and work-hardened surface but also to impose favorable compressive residual stress in it. To analyze the feasibility of turning-burnishing hybrid process, the Taguchi’s L27(313) orthogonal array method with the analysis of variance (ANOVA) were used to analyze the influence of the initial turning process on surface integrity of roller burnished AISI 1045 steel such as surface roughness, surface microhardness. three turning parameters, namely the cutting feed, cutting depth and cutting speed, three burnishing parameters, namely the burnishing feed, burnishing depth and burnishing speed were selected as the experimental factors in Taguchi’s design of experiments to determine which one has the dominant influence and how it works on burnishing effects, namely the surface roughness and surface microhardness, the interactions between cutting feed, burnishing feed and burnishing depth were considered. The experimental results agreed well with the theoretical analysis and the conclusion is cutting feed has dominant influence on burnished surface integrity.
Authors: Tong Wang, Xin Fu Zhang, Xue Fang Zhao
Abstract: This paper studies the surface quality of tool steel with high-speed wire electrical discharge machining (WEDM) method, which is conducted in gas to improve the accuracy of finish cut, and compares the surface quality in atmosphere and in emulsion dielectric. Experiment results showed that WEDM in atmosphere offers advantages such as better straightness and higher material removal rate. With the growth of wire winding speed, the removal rate and straightness error will increase significantly either in atmosphere or in liquid. Along with the feed increasing, the discharge gap lengthes decrease successively under the both media conditions, and the straightness is obviously improved in atmosphere. Regardless of the use of atmosphere or emulsion, an optimum feed will exist, which makes the roughness the lowest and the removal rate the highest.
Authors: Lian Jie Ma
Abstract: The characteristic of tools wear is analyzed through turning fluorophlogopite glass-ceramics. And the process of tools wear can be divided into three periods. Through single factor test, the influence of tools wear was discussed such as tool material, cooling conditions, cutting depth and feed speed. The study indicates, the tools material and cooling condition are major factors to affect tools wear. The high-speed steel tool is not suitable for turning fluorophlogopite. Because sustaining time of cutting is short and efficiency is low in machining, the tungsten-cobalt carbide tool is not perfect tool. And ceramics tool is better than the both. The tools wear rate can be decreased under cooling conditions. Influential curve of tools wear rate versus cutting depth is a part of parabola curve.
Authors: Qing Shun Bai, Chun Li Yang, Ying Chun Liang, Li Dong Tong, Yan Zhao
Abstract: The minimization of mechanical parts is one of important research direction in micro machine or MEMS area. Milling experiments of micro part were conducted on micro machine by using TiAlN-coating micro-diameter cutter. Three kinds of typical workpiece materials (LY12, stainless steel and high-elastic alloy 3J21) were adopted and the wear properties of micro-diameter cutter were investigated carefully. The main reasons for tool wear and breakage were analyzed. It is shown that the common wear characteristics of TiAlN-coating micro-diameter cutter are falling off of coating, breakage of tool nose, diffusion and adhesion wear while machining the three materials. Adhesion and diffusion effects are much obvious in machining 3J21 alloy and stainless steel, leading to coarse wear region of tool.
Authors: Yi Yi Tao, Xiao Lan Ge, Xiao Jing Xu, Zuo Jiang
Abstract: The SiCp/Al composites reinforced by SiC particles with various sizes and contents were prepared by cold compacting and subsequent hot extruding. The mechanical and wear properties of the compositions were investigated and the relevant mechanisms were discussed. It has been shown that the tensile strength and wear resistance increases with increasing SiCp content. SiC particles have a remarkable reinforcing effect on matrix Al. The composite with larger SiCp size (14μm) possesses better wear resistance than that with smaller SiCp size (130nm).
Authors: Song Zhang, Jian Feng Li, Feng Shi Liu, Feng Jiang
Abstract: Titanium alloys are widely used in the aerospace industry for applications requiring high strength at elevated temperature and high mechanical resistance. However, titanium alloys are classified as extremely difficult-to-cut materials owing to their physical, chemical, and mechanical properties, which result in the low material removal rate and the short tool life. This paper presents an experimental research of the tool wear patterns and relevant wear mechanisms during high-speed milling of Ti-6Al-4V with cemented carbide inserts. SEM-EDX analysis showed that nose wear and edge wear were the main tool failure modes during high-speed milling process, which were different from the wear patterns under traditional cutting conditions. Adhesion, attrition and diffusion wear mechanisms, as well as the cracks were responsible for the tool wear.
Authors: Li Li Liu, Jian Xin Deng
Abstract: Idea of functionally gradient material (FGM) theory was used to the design of ceramic nozzle. The purpose was to increase the erosion wear resistance at the entrance of the nozzle in dry sand blasting processes. The SiC/(W,Ti)C gradient ceramic nozzles fabricated by conventional hot pressing. The erosion behavior of the SiC/(W,Ti)C gradient ceramic nozzles were investigated in comparison with the common homologous ceramic nozzles. The experimental results have shown that the ceramic nozzles with a gradient structure have superior erosion wear resistance to that of the common homologous ceramic nozzles under the same test conditions. It was shown that the mechanical properties of the gradient ceramic nozzle materials were greatly improved in comparison with that of the common homologous nozzles. The surface Vickers hardness and indentation fracture toughness of gradient ceramic nozzle were greatly improved compared with that of the common homologous nozzles. Therefore, it is indicated that gradient structures in ceramic nozzles is an effective way to improve the erosion wear resistance of the common homologous nozzles.

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