Materials Science Forum Vol. 723

Abstract: In this study, micro- crystalline diamond(MCD), fine grade diamond(FGD) and nano- crystalline diamond(NCD) thin films are successfully coated on WC-Co micro drills(φ=400µm) adopting hot filament chemical vapor deposition (HFCVD) technique. The microstructure and cutting performance of micro drills for applying to drill electrical discharge machining(EDM) graphite coated with MCD, FGD and NCD films are systematically investigated by means of field emission scanning electron microscope(FESEM) and Raman spectroscopy. After drilling of 1500 holes, wear behavior of these micro drills is analyzed by FESEM and NCD coated micro drills exhibit minimum flank wear compared with the other samples due to the relatively good wear resistance and friction properties of NCD films.

Abstract: In this paper, methods of micro-fabrication carried out by micro milling machine are proposed. Structure design and simulation analysis of micro milling machine are accomplished. A 3D parametric modeling software CATIA is used to complete the structure design and modeling of micro milling machine and a simulation software ANSYS is used to do the whole analysis of micro milling machine. The static and dynamic simulation analysis of motorized spindle which is the key part of micro milling machine is also completed. Through simulation and analysis to seek the rationality of the design of micro milling machine. It has important significance for the improvement and development of machine tool in the next step.

Abstract: The traditional cutting tools grinding reveals inexact tool flutes that altered the tool strength and affect the chip evacuation capabilities. Moreover, the normal rake angles are neither exact nor varying smoothly on the rake face along the cutting edge. Adopting the rake face grinding process, the wheel shape and path are optimized using GODLIKE scheme in order to grind the tool flutes with exact helical and normal rake angles while keeping close matching to the designed flutes. A tapered ball-end mill is considered in this study due to its extensive role in five-axis sculpture surfaces machining. With this approach proposed, a simple grinding wheel replaces the complex wheels commonly used, and the deviation between the designed and the generated flutes reveals less than 4 % of the tool minor radius. Beside all, a relationship between the radial and the normal rake angles are established.

Abstract: An experimental study was carried out to investigate the temperature measurement method and burn mechanism in the surface grinding of a stainless steel 1Cr11Ni2W2MoV with SG abrasive wheels. The temperature response at the wheel-workpiece interface was measured using a pair of thermocouple composed of the workpiece material and a single enameled constantan wire which was implanted in the workpiece. Changes in the ground surface morphology and metallography of the specimens in different grinding conditions were analyzed. Plastically deformed coating layers and micro-cracks were observed on ground surface by SEM (Scanning Electronic Microscopy) when grinding burn occurs. Grinding burn mechanism was unveiled from a metallographic point of view. When the average temperature exceeded phase alteration temperature of 1Cr11Ni2W2MoV, the original gray strip martensite structure was replaced by tempered sorbite structure, which caused a sharp reduction of the workpiece surface hardness. The results provided a theoretical and experimental basis for technical optimization in the grinding of high temperature stainless steel with high efficiency and high quality.

Abstract: The force of each API standard buttress casing thread teeth under axial tension is uneven, so the bearing capacity of this kind of thread is seriously restricted. On the basis of structural characteristics, mechanical model of the casing thread under axial tension is established and the loading and deforming features of thread teeth are analyzed. Based on this, to improve force distribution of casing thread, the designing method of multi-segment variable pitch thread is put forward and NC machining method of variable pitch thread with equal tooth thickness is presented.

Abstract: The mechanism and characteristic of high speed grinding and the technology and development of high speed grinding were introduced. High efficiency grinding including ultrahigh speed grinding, high efficiency deep grinding, creep deep grinding and abrasive belt grinding was analyzed. The technology about manufacturing the spindle system in super high speed grinding and the other main interrelated technology about grinding were also described.

Abstract: The whole impeller machining technology has long been an important object of study, and has been widely used in aerospace applications. In this paper, CNC machining technology for the whole open impeller is the object of study. First, the geometric characteristics of such parts and processing difficulties are analyzed, and then the key technologies for the rough and the finishing are made. The key technologies described in the paper comprise the building of the leaf ruled envelope surface and the choice of tool axis vector in plunge mill rough process, and the whole leaf processing cutting tool path planning using the parameters method in the finishing process. Finally, completed the machining simulation verification base on VERICUT software, and finished the whole process of the open impeller machining.

Abstract: The nonlocal theory was introduced to establish the nonlocal constitutive model and analyze the effect of ultrasonic on the tensile strength and fracture surface microstructure. ZTA ceramics tensile fracture experimental results show that the tensile stress obviously reduces and the fracture changes under ultrasonic vibration. The experimental results are coincided with theoretical analyses.

Abstract: Drilling procedure is widely used in orthopedic surgery to insert the steel nail to stabilize the bone. However, successful execution of bone drilling requires a high level of dexterity and experience, because the drilling resistance is large and sometimes vibrates violently to even break the slender drill. This paper introduces the study of drill force in different cutting parameters and different bone density. The density of cortical bone is higher than that of cancellous bone, so the drilling force decreases suddenly from the peak and then maintains a stable value. Drilling forces are more related with feed speeds and bone density. Drilling force increases as feed speed increases and bone density increases. Accurate drilling process can be obtained to provide effective surgery training and rehearsal.

Abstract: The working principle of the electromagnetic barrel finishing machine as well as the generating mechanism and effect of the alternating rotating magnetic field are analyzed, based on the electromagnetic theory to establish a mathematical model of the rotating magnetic field, by the ANSYS finite-element method, resolved the effect of the magnetic flux density and magnetic field strength impacted on the grinding pressure, the electromagnetic finishing machine internal magnetic flux lines distribution law is analyzed under the influence of the alternating rotating magnetic field, finally the reasonableness of the magnetic field distribution is verified by experiments and the electromagnetic finishing machine has been optimized.