Key Engineering Materials Vols. 579-580

Abstract: The CVD diamond films have a series of excellent performances, so it has a wide range of applications in the cutting tools, wearable devices, electrochemical electrodes and other fields, and it has a very substantial market prospects. In this study, The diamond films with a layer of uniform and smooth were deposited on the surface of the complex surface YG6 carbide end mill by using the hot filament CVD method, the quality of diamond films was detected by using the scanning electron microscopy and the laser Raman spectrometer. The cutting performances of diamond coated end mill were evaluated from the workpiece surface quality and tool life two aspects by cutting silicon carbide aluminum reinforced composites, and compared with the uncoated carbide tools. The experimental results show that because of the cutting tool was pretreated that make tool surface coarsening, leading the surface quality was machined by diamond coated tools is lower than the carbide cutting tools. However, the coating can protect the tools, increase the wear resistance of the coated tools and make the life of the diamond coated tools increase 3-5 times than the carbide cutting tools.

Abstract: At present, many of the problems about precision guarantee in centerless sunperfinishing have been solved due to the forming system design in the process of machining and machine tool adjustment. But the precise forming trajectory cannot guarantee the given accuracy. Because uneven movement of the blank in the process of processing owing to the comprehensive influence of motion and force, resulting in, causing changes in metal removal. Now, there has been no the geometry kinematics theory model because lack of the study of the physical reasons for the above phenomenon. So improving accuracy of centerless superfinishing depends on the analysis of the description of movement and stress parameter analysis and equipment parameters adjustment. The stress distribution of the blank in centerless superfinishing process was studied. Force balance equation of it was established. Characteristics of movement of the blank relative to the roll and oil stone was analyzed. Found the friction condition of the blank steady rotating contact with the roller. Some of machine tool equipment adjustment parameters which have great influence on the stability of motion were analyzed. A few methods improved the centerless superfinishing precision by analysis of the movement description and Mechanical processing parameters and Machine tool equipment parameters adjustment were analyzed.

Abstract: Grinding experiments were conducted using vitrified CBN wheel on particulate reinforced titanium-based matrix composites (PTMCs) and Ti-6Al-4V matrix. The issues discussed are grinding forces, surface roughness, and the formation of surface integrity. The main results are summarized as follows: (1) The grinding forces increase with the increasing workpiece speed and depth of cut during grinding PTMCs and Ti-6Al-4V materials. (2) Decreasing depth of cut properly contribute to obtaining finished surface with good surface during grinding of PTMCs using CBN wheel, but the workpiece speed has little influence on the surface roughness value of PTMCs. (3) The formation of surface integrity of PTMCs is due to the combined removal of the TiC and TiB reinforcements and the Ti-6Al-4V matrix.

Abstract: Laser cooling is one of the critical problems in the research of high power semiconductor lasers. This paper provides an overview of microchannel heat sink which is used to cool the high power semiconductor lasers. The method of polishing after cutting is the current processing method of the heat sink, which is because the ordinary cutting method cannot meet the requirements of high quality of surface and edge burrs. This paper proposes ultra-precision fly cutting method for heat sink machining to omit the polishing processing to improve the machining efficiency, and verifies by experiments that the feasibility of the processing method and the edge quality improved by workpiece superposition processing method.

Abstract: For investigating the machined surface defects in high-speed cutting of SiCp/Al composites. The simulation and experiment of high-speed cutting process is done. The simulation of high-speed cutting process using the Cowper-Symonds model is established to explore the forming mechanism of the machined surface defects. The results show that the machined surface defects include small pit, big pit, groove and the raised particle. The experiment which uses the same cutting parameters with the simulation of FEM (Finite Element Method) model is carried out to verify the results of FEM simulation. The results indicate that the forming mechanism of machined surface defects prove to be true.

Abstract: The online test system of the vertical spindle motion error of the ultra-precision fly cutting machine tool was established. And then using the online test system established to test and analyze the state of the rotary motion of the spindle under the idling condition. The axial synchronous motion error value of the spindle under 390rpm is about 61 nm, and the asynchronous error motion is about 33nm. The radial error motion value is about 91nm, and the asynchronous error is about 35nm. Through the test, we found that the axial and radial spindle error motion accuracy under idling speed can been improved with the spindle speed increases.

Abstract: Carbon/carbon composite is composite material using carbon fiber as reinforcement and carbon as matrix. However, it is the difficult-to-machine material due to some characteristics of the material. The thesis uses ultrasonic milling cutting in order to improve the surface quality. Surface quality becomes better with the improvement of milling speed; surface quality becomes poor with the increases of per tooth feed and cutting depth; S_ku increases after adding ultrasonic, and which explains that the mechanism of ultrasonic milling is different from that of ordinary milling; the increase of S_al indicates that surface defects of all kinds reduces in ultrasonic milling and the surface quality is better than that of ordinary milling.

Abstract: This paper present a Giant Magnetostrictive Actuators (GMA) which used magnetostrictive characteristics of Giant Magnetostrictive Material (GMM) and is applied on Micro displacement of precision instrument. Since GMM is influenced by temperature and the electrified coils generating magnetic field are the main sources of heat in GMA, so the temperature impacts factors on the output displacement of magnetostrictive material are analyzed firstly, and also a control method based on existing magnetostrictive actuators is redesigned, while model is established according to the relation between output displacement and voltage values. Finally a solution is proposed about heat compensation control in GMA, and also adds a water cooling system to the cavity of GMA and controls the temperature of cooling water by Single Chip Microcomputer (SCM) according to the detected temperature of magnetostrictiverod; therefore compensations for the GMAs feed displacement are allocated. Displacement closed-looped PID controls are used to tests, which can proves that the heat compensation control system of GMA can lower the impact of increasing temperature on GMMs magnetostriction coefficient and increase positioning accuracy.

Abstract: Aerostatic bearings are utilized in a variety of precision devices to eliminate viscous friction between moving parts for realizing high accurate motion and supporting load at zero speed. However, in practice external pressurized source is necessary to realize the aerostatic bearing, which sometimes leads to difficulty in some medical and aero applications within tightly sealed containers. In order to tackle this problem, an innovative principle bearing, which utilizes traveling waves, has been proposed in previous paper. In order to theoretical analyze the principle and numerical predict the performance of the gas bearing utilizing traveling waves, a numerical model based on 2-dimenssional Navier-stocks Equations with neglecting gravitational force is developed in this paper. The equations are solved discretely by dynamically meshing the isotropic 2D model and updating the boundary conditions. It reveals that the gas film force varies with a nonzero average value that can be utilized to realize a non-contact gas bearing. The effect of driving voltage and frequency, and the bearing clearance height on the average film force is clarified by simulations. The proposed bearing design is ought to eliminate drawbacks of conventional hydrostatic bearings such as supply of external pressure source, use of compressor, and tubes while still achieving comparable static and dynamic capabilities.

Abstract: Machining of metals make use of thermal mechanical FEM model. Analysis of nonlinear elastoplastic finite element simulation of milling of 45 # steel material use software of DEFORM-3D that is finite element simulation technology. DEFORM-3D software could be carried out on prediction of the milling force. Through finite element analysis, distribution of stress field, strain field and temperature field of workpiece and tool is obtained under the influence of thermal mechanical. The prediction accuracy of the model was validated experimentally and the obtained numerical and experimental results were found in good agreement.