Key Engineering Materials Vol. 499

Abstract: In this paper, the surface of non-woven polypropylene secondary battery separator was modified by Hollow Cathode Remote Plasma. The effects of treating parameters on separator’s properties were studied. The IR and SEM were used to analyze the chemical composition and the surface morphology. Using electrical chemical property measurement, the electrical chemical property was measured and analyzed. The results show that the hydrophilic group was imported on the surface of polypropylene after Hollow Cathode Remote Plasma modification, so that the wettability of the non-woven polypropylene secondary battery separator and the property of secondary battery were greatly improved.

Abstract: In order to research the Law technology and the equipment performance of Electro Jet, The institute developed an electro jet machine. Through a large number of experiments on this machine, the author concluded its process law and analysis the corrosion mechanism to the removed process. The results show that, duty cycle and frequency have a certain effect on the machine accuracy, and duty cycle is the main factor of aperture morphology. When duty cycle varies from 30%~40%, the stray corrosion is less. Frequency affects the depth seriously, based on the original experiment, voltage, duty cycle. Frequencies were not interactive within the scope of the study. The corrosion of anodic workpiece satisfies Faraday law by the study of material removal mechanism. Current efficiency is less than 1, and it’s 40%~60%.current density is 2~4.5A/mm2, that is larger than ordinary electrochemical machining.

Abstract: This paper deals with an experimental research on the wear mechanism of coated carbide tools in dry boring of the titanium alloys TC11 which are commonly used for aero-engines. The wear mechanism of coated tool inserts was investigated at various combinations of cutting speed, feed rate, and depth of cut. Analysis carried out with the SEM suggests that adhesive wear and coating delamination are the dominant wear mechanisms under low speed and feed rate and depth of cut; while chipping and breakage are the dominant wear mechanisms for the combinations of high cutting speed, feed rate, and depth of cut. There was no observation of oxygen existing based on the analysis of SEM which indicated no oxidation wear generated during the boring machining. The excellent chemical stability of TiAlN coating and oxidation resistance performance made contribution to prevent oxidation wear. Another reason was that boring temperature was lower than oxidation temperature.

Abstract: Uniform molten metal droplet stream from jet break-up provides potential technology for metal parts rapid prototype manufacturing. In this study an experimental device capable of producing uniform metal droplet stream has been developed. Monosize spherical powders of 180m in diameter can be obtained after cooling and solidification. Then the droplets were electrostatically charged and deflected during flight to deposit onto a revolving substrate to form a 3D metal part.

Abstract: Helical milling is a hole making process by milling in which the center of end mill orbits around the center of the hole while spinning on its axis and feeding in the axial direction. This paper makes a comparison between drilling and helical milling in cutting forces, hole quality and tool wear through a series of experiments. The results show that the axial cutting force of helical milling is far less than that of drilling and the holes quality is also better than traditional drilling. Cutting tools show excellent machinability in helical milling.

Abstract: Orthogonal and single factor intermittent turning experiments of hardened AISI 1045 steel were conducted with two kinds of Al2O3-(W, Ti)C ceramic tools used, aiming to reveal the effects of cutting parameters on cutting forces, the influence of mechanical and thermal loads on tool wear mechanisms at different wear evolution stages. Empirical formulas for average cutting forces and tool lives (impact number of tools under two different flank wear limits 0.1 mm and 0.3 mm) were established respectively. The worn or fractured surfaces of the tools tested at different cutting speeds were analyzed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). It is found that feed rate and depth of cut had greater influence on the average cutting forces in cutting periods than cutting speed did. The amplitude of the vibration generated in the radial direction decreased with increasing cutting speed, while that of the vibration generated in the other two directions increased. The influences of mechanical and thermal loads on tool wear changed in different ways at different stages of tool wear evolution process. There existed critical cutting speeds above which adhesive wear of the ceramic cutting tools became less serious.

Abstract: In mechanical micro-grooving, cutter V-tip shape and wear greatly influence the generation of micro-groove on workpiece surface. Hence, cutter V-tip wear and micro-groove shape were observed in micro-grooving experiments. The objective is to understand the generation mechanism of micro-grooves. First, the high-speed steel cutter was ground to be a V-tip whose tip radius is 5 m; then a turning experiment was performed to pattern the micro-grooves on steel surface using the cutter V-tip; then the cutter tip wear and the machined micro-groove shape were measured and evaluated; finally, the effect of cutter rake angle was investigated on cutter tip wear and micro-groove quality. It is shown that the machined groove tip radius is much larger than the sharpened cutter tip radius due to the rapid cutter tip wear during grooving. On increasing cutter rake angle, the cutter V-tip wear decreases, thus leading to the improvement of form accuracy and surface roughness of machined micro-grooves are both improved.

Abstract: The residual stress in the milling of 7050-T7451 aluminum alloy was measured using X-ray diffraction method in which Psi-oscillation, Phi-oscillation and peak fit were adopted. Cutting speed and feed are main variables which were considered in this study. The results show that compressive residual stresses are generated in surface for the down milling generally, which is mainly due to burnishing effect between the tools flank face and the machined surface. In feed and its orthogonal direction, the effect of cutting speed and feed speed on residual stress is similar. Therefore, required residual stress can be achieved by controlling the cutting condition such as cutting speed, feed speed etc.

Abstract: KDP crystal is a good nonlinear optical and electro-optical crystal material. However, KDP crystal is considered to be one of the most difficult machining materials due to its inherent properties. This paper presents a preliminary experimental study on surface roughness of KDP crystal processed with rotary ultrasonic face milling. The study shows that the process variables (spindle speed, feedrate, and milling depth) have significant influence on the surface roughness in processing KDP crystal. It discusses the effects of the mechanical properties of KDP crystal on the processing performance. The experimental investigation reveals that the rotary ultrasonic face milling method can obtain smoother surface, which means the method is available for processing KDP crystals with a proper machining conditions. This preliminary research affords a guiding significance for precision processing KDP crystals.

Abstract: Alumina (Al2O3) bubble particles were added into the mixture of CBN abrasive grains, Cu-Sn-Ti alloy and graphite particles to prepare the composite blocks for porous CBN abrasive wheels. The specimens were sintered at the temperature of 920°C for the dwell time of 30 min. The bending strength of the composite blocks was measured by the three-point bending tests. The fracture surface of the blocks was characterized. The results show that, the content of alumina bubble particles does not take significant effect on the mechanical strength of the composite blocks. Even the lowest strength of the composite blocks, 98 MPa, is higher than that of the vitrified CBN abra-sive wheels. Cu-Sn-Ti alloy has bonded firmly alumina particles and CBN grains by means of the chemical reaction and corresponding products. Finally, the chip space was formed through the re-moval of the ceramic wall of the alumina bubble particles within the CBN abrasive wheel during dressing.