Materials Science Forum Vols. 800-801

Abstract: Surface roughness plays an important role in product quality, especially for that used in the domain of dental restoration. This paper presents a study on the surface roughness prediction and experimental analysis in grinding the material of zirconia used for dental restoration. For this purpose, the experiment using the orthogonal method is employed. The orthogonal array and range analysis were applied to study the effect of the process parameter had on the surface roughness. A high accuracy machining center, a new dental bur used only for dentistry, and a surface roughness measuring instrument which have excellent properties, are been employed to conducted the experiment. The experimental results demonstrated that the amount of feed, be the major parameter on surface roughness, followed by the width of cut. At the last part of this paper, a model for predict the surface roughness in grinding zirconia is developed based on the experiment by means of linear regression analysis, which can be used to estimate the values of surface roughness given certain grinding parameters.

Abstract: Micro cutting offers good potentialities in order to manufacture small and medium lot sizes of micro-parts with arbitrary geometry at an economically reasonable expense. This technology has been widely used in many fields, especially in aerospace field and biological medicine. The slit grating which is used for X-ray telescope is difficult to machine because of the small critical dimensions, large material removal rates and the high requirement of machining quality. In this paper, two methods are describes to manufacture the slit grating which include micro-milling and flying-cutting. The focus is on the design of micro tool, optimization of machining parameters, the comparison of machining efficiency and precision of slit grating by micro-milling and flying-cutting.

Abstract: Tool wear condition monitoring has been an effective method in improving the production efficiency and process automation. In this paper, to analysis the cutting force features in tool wear condition monitoring of difficult to cut materials, we first remove the direct current components and apply a fast Fourier transformation to the cutting force to observe the features in different frequency bands. A wavelet packet transformation is then adopted to the cutting force to observe the relationship of energy ratio and tool wear states.

Abstract: In titanium alloy machining, under different cooling lubrication conditions, the variation of tool wear and chip morphology have a certain effect on the surface roughness. Under different cooling lubrication conditions, in order to analyze the variation of tool wear, chip morphology and surface roughness, the surface roughness values are measured ​​and the variation in tool wear and chip morphology are observed, and then the interaction relationship between the tool wear and the chip morphology is analyzed. The results show that the tool wear and chip morphology influence on the surface roughness. Under different cooling lubrication, the rake face wear do not change significantly, but wet cooling and MQL play a protective role for the flank face wear.

Abstract: Monocrystal sapphire ground surfaces obtained by ductile mode and brittle mode are analyzed in this paper. A two dimension (2D) fractal properties of different ground surfaces are calculated and analyzed by a box-counting fractal method. The results show that the fractal dimension (FD) in parallel grinding direction can imply the material removal mode, especially for the surfaces with a similar roughness Ra obtained in different material removal modes. The ground surface obtained in ductile mode has much higher FD in the parallel direction than that in brittle mode. For the surface with high FD in parallel direction, its profile is more exquisite and surface quality is better. For the surface with a small FD in the parallel direction, a deeper crack and more pronounced defects occur. On the other hand, the profile FD distributions can reflect the anisotropic features of monocrystal sapphire ground surfaces. Therefore, the fractal analysis method has the potential to reveal precisely and comprehensively the ground surface characteristics of monocrystal sapphire.

Abstract: The nickel-based superalloy GH4033 is one of the difficult-to-cut materials. In order to investigate the machinability of GH4033, the tool cutting performance, tool failure modes, tool life and the relationships between surface roughness and tool flank wear were studied by using different coated cemented carbide cutting tools under dry cutting. Aiming at the amount of metal removal combining with the tool life and surface quality, the better cutting tool coating type and optimal cutting parameters were obtained through the orthogonal experiments. The results showed that the cutting performance of TiCN coated tool (GC4235) was better than that of TiAlN coated tool (JC450V). With these two kinds of tools, the machined surface roughness decreased to a minimum value and then increased with the increase of flank wear. When cutting GH4033, the main wear mechanism for both of the two types of tools included adhesive wear, diffusive wear, abrasive wear, edge wear and coating peeling.

Abstract: Large cylindrical shells are widely used in many areas of aerospace, petroleum chemical industry and nuclear power, etc. The main material of large cylindrical shells is 2.25Cr-1Mo-0.25V. In the process of heavy-duty cutting cylindrical shell material, the removal rate is high, and machine condition is rough, because the viscosity of big cylindrical shell material, the large chips not easy to be broken, and the tool and workpiece often entangled affect the machining efficiency. Researh and development to apply heavy cutting under the condition of high performance cutting tool has great practical significance, because of at the same time for heavy cutting tool is less in china. This paper uses the cutting performance experiment aiming to cylindrical shell material used in different three-dimensional groove blades and studies the range of different blades broken chips and the influence of three-dimensional groove on breaking effect. The chips form of cutting cylindrical shell material is summarized. And chip-breaking groove of the best performance is optimized. The paper designs of the new heavy-duty vehicles blade well and vertfies the good effect of the new heavy-duty cutting the breaker by the results of 3 d finite element simulation. The paper provides basis for designing heavy-duty cutting.

Abstract: This article mainly aims at the problem of silicon carbide ceramic mechanical turning difficult processing,by adopting the method of the numerical control turning processing.Design a special fixtures and a NC machining process to accomplish the manufacture of silicon carbide plate.And through the single factor analysis method to process parameters were analyzed.

Abstract: Turning process properties of difficult-to-cut materials used in aeronautics are often associated with the machining accuracy and surface quality of aerospace structural parts. This study presents the influence of cutting velocity, feed rate and back cutting depth on cutting force and cutting temperature during dry turning of ultra-high strength 300M steel, where the linear regression models of cutting forces and cutting temperature are constructed by using least square method, and the regression coefficients of these models are verified by significance tests. Meanwhile, the temperature distribution and chip in turning machining are also achieved by finite element analysis.

Abstract: Silicon nitride cutting tool, which is widely applied to machine cast irons, is not suitable for steel cutting because of the massive chemical wear between silicon nitride and ferrous materials. Covering protective coating (s) on tool surface is an effective way to isolate the chemical contact between cutting tool and workpiece. The aim of this paper is to investigate the cutting performance and cutting mechanism of coated silicon nitride cutting tools on steel machining. The cutting performances of uncoated and CVD-Al₂O₃/TiN coated silicon nitride cutting tool when cutting high hardness alloy steel AISI 4340 under dry condition were investigated. Studies include tool flank wear, tribological behavior of the tool-chip interface and wear mechanisms for both uncoated and coated silicon nitride cutting tools. The results showed that the tool life of silicon nitride cutting tools can be improved to a great extent with the cover of CVD-Al₂O₃/TiN coating by avoiding crater failure and reducing friction during steel cutting.