Key Engineering Materials Vols. 579-580

Abstract: Ti6Al4V has great affinity with tool material in machining process, which easily leads to tool diffusion wear. Turning experiments were carried out to study cutting temperature and pressure at tool-chip/workpiece. Based on the analysis, a scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectrometer (EDS) was used to analyze tool wear morphology. The affinity of tool and workpiece material using the Ti-W, Ti-Co diagram was also studied to elaborate the diffusion mechanism in this present study. The results shows that the cutting temperature is very high and the temperature increases with the increase of cutting speeds in machining Ti6Al4V. At the contact area, the highest temperature is located in tool rake face near to tool tip. The resilience of workpiece results in serious attrition between tool flank face and the machined surface. The highest pressure is located in tool flank face near to tool tip and the pressure in tool-workpiece interface is much higher than that in tool-chip interface. Under the high cutting temperature and high pressure at tool-chip/workpiece interface, diffusion occurred both at tool rake an flank face in machining Ti6Al4V. Because of the higher temperature at tool rake face diffusion at tool rake face ia more sever than that at tool flank face.

Abstract: In this paper, the author performed orthogonal tests of ultrasonic vibration grinding on ferrite in the DMG machining center, and established a prediction model of ferrite surface roughness in ultrasonic vibration grinding with multiple linear regression analysis method based on the test results, and carried out significance tests on regression equation and regression coefficient, showing that the prediction model had high credibility, the effect of spindle speed and amplitude of ultrasonic vibration on surface roughness was significant, but of grinding depth and feed rate was not obvious.

Abstract: The main characteristic of hard turning process is easy to produce serrated chip. The chip deformation will impact greatly turning process. It is very important to analysis the chip formation and morphology during precision turning process of hardened steel. The deformation mechanism of serrated chip formation process and its chip morphology of chips produced during precision turning process of the hardened steel GCr15 is studied in hard cutting experiment by the methods such as numerical simulation of two-dimensional finite element analysis of turning, chip cross-sectional microscopic analysis and other methods .High speed precision turning of hardened steel GCr15 produces morphology of continuous chip and serrated chip; Serrated chip has the typical characteristics of the adiabatic shear slip after section such as apical surface of the serrated chip is composed of multilayer rolling dentate shear plane, a single surface of one tooth is not smooth, but no crack. Extrusion grooves is produced from tooth root to tip; Intensive slip line on serrated chip cross-section can be saw by microscopic observation; Fracture surface of the serrated chip presents small tumor tissues. The results show that the reason of hardened GCr15 steel forming serrated chip is periodic adiabatic shear fracture, and the research provides a theoretical reference application of hard turning technology.

Abstract: For the technology of diamond cutting of optical glass, the machinability of glass is poor, which hindering the practical application of this technology. In order to investigate and ameliorate the machinability of glass, and achieve optical parts with the satisfied surface quality and dimensional accuracy, this paper first conducted SF6 indentation experiment by Vickers microhardness instrument, and then the scratching tests with increasing depths of cut were conducted on glass SF6 to evaluate the influence of the cutting fluid properties on the machinability of glass. Based on this, turning tests were carried out, and the surface quality of SF6 was assessed based on the detections of the machined surfaces roughness. Experimental results indicated that compared with the process of dry cutting, the machinability of glass SF6 can be improved by using the cutting fluid.

Abstract: Deposit uniformity control is the key in laminated template electroforming and has direct influence on the parts shaping quality and processing cost. Accordingly, this research proposes a Assisted-Grinding pulse electro-deposition technology and designs the device and technology based on the principal. According to experimental method, a number of hard particles (ceramic beads) fill between the electrodes and are propelled by mandrels rotating movement to allow continuous impinging and grinding to the cathode surface, as an effort to instantaneously eliminate boundary effect that is caused by uneven current distribution. In comparison of the finish surface morphology and deposit thickness among the samples obtained respectively by traditional and new ways, the experimental results show that assistant friction could effectively remove the excess sediment and tumor along surface and provide a relatively flat layer with Ra 0.253μm. It shows particles-assisted-grinding has satisfactory practical values and is a novel exploration resolving the technical obstacle in electrodepositing.

Abstract: Hydrostatic bearing is wildly utilized in many precision applications and positioning stages due to their ability to support designed load at zero relative speed between bearing and guide surfaces. However, in practice external pressurized source is necessary for realizing the hydrostatic bearing, which sometimes leads to difficulty in some medical and aero applications within tightly sealed container. In order to tackle this problem, an innovative principle bearing, which utilizes traveling waves, has been proposed by authors in previous researches. The proposed principle is ought to eliminate drawbacks of conventional hydrostatic bearing such as external pressure source, use of compressor, external pump and tubing system, while still achieving comparable static and dynamic capabilities. Based on the proposed principle, a prototype device of liquid bearing utilizing traveling waves was developed and analyzed by experiments in this present paper. Its floating and smooth motion is confirmed by experiments here.

Abstract: Electric heating cutting technology is that material is heated by the thermal effect of the current so that the cutting zone material is softened, meanwhile this reduces the shear resistance of the material, thereby the cutting process gets smooth. In order to make the electric heating technology apply to the small hole drilling successfully, this paper designs a set of compact and simple electric heating drilling device to small hole, this device adopts the electrode structure to avoid spark, and by the device we drill small hole to hard-to-cut materials stainless steel under various parameter conditions, test process and results show that the electric heating drilling device is effective and practical.

Abstract: In this paper, cold-rolled T2 copper foils with the thickness of 50 were chosen. The foils were annealed at different temperatures, namely, 250°C, 350°C, 450°C, 550°C, respectively. Micro deep drawing experiments on cold-rolled foils and annealed foils by laser driven flyer were achieved in order to investigate annealing effects on the formability of T2 copper foil. The forming depth and material flow uniformity of the workpiece at different conditions were compared and analyzed. The test results showed that: (1) The workpiece of cold rolled foil indicates poor neutral, non-uniform material flow, smaller forming depth, it is due to that the microstructures of cold-rolled foil are fiber organizations, which leads to poor plastic deformation capacity.(2)Annealing can significantly improve the formability of the foil. In the first stage : 250-350°C, recovery and recrystallization occurred in succession in the organization of the raw material, fibrous tissue transformed into equiaxed grains, the residual stress is greatly reduced, thus, the plastic deformation capacity is recovered. The forming depth is also significantly improved, increasing by about twice. In the second stage: 350-450°C, the enhanced formability is relative to the surface layer effect, which is also a reflection of micro-scale effect. This study provided a theoretical and experimental guidance for the practical application of micro deep drawing process by laser driven flyer.

Abstract: Along with the thorough research of lithium ion battery, the lithium iron phosphate with the peridot structure becomes a new higher energy power battery anode material. But the charge and discharge mechanism of the modified lithium iron phosphate positive material did not get the unity understanding. In this paper, the carbon coating modification, metal ion doping, particle surfaces coated iron-phosphorus phase network and the nanoparticles of lithium iron phosphate were analyzed from the modified microstructure of the lithium ion phosphate batteries, so as to get the charge and discharge mechanism is the results of the active atoms and lithium ion embedded in the grid work and emergence in the layer structure, leading to the energy changes in lithium iron phosphate microstructure.