Advanced Materials Research Vols. 189-193

Abstract: Vibration drilling with internal spray-cooling method was proposed for the poor thermal conductivity characteristics of superalloys. Cutting temperature and tool wear in vibration drilling, conventional drilling and step drilling were compared by experimental study. The results show that: the cutting temperature in vibration drilling does not change significantly with the hole depth and slowly increased with the increase in the number of drilling; the tool wear rate is reduce, tool life is extened and the processing efficiency is improved.

Abstract: A model of stress and temperature field is established on nickel-based alloy cutting by finite element modeling and dynamic numerical simulating, and then combining high-speed machining test and orthogonality analysis method, the influence law of cutting parameters on the cutting force and tool wear has been researched, and the tool life and cutting force prediction model based on cutting parameters has been obtained. Finally, by genetic algorithm method cutting parameters are selected reasonably and optimized. The result shows that the bonding wear is main tool wear, and the influence of cutting speed on cutting force is smaller than feed per tooth and axial depth of cut.

Abstract: In the shearing process, these were many problems in shearing, the regularity of metal deformation of shearing was analyzed combined with theory of ductile damage and fracture mechanism of high-speed, the rules of factors which could be affected the shearing was analyzed on the velocity and shearing stress state. These theories would improve the shearing section.

Abstract: In this paper, the EDM performance of water-in-oil (W/O) emulsions dielectric with different surfactant concentration is investigated by correlated to its physical properties, such as viscosity and droplets size, which is predominantly determined by the surfactant concentration. Experimental results show that the stability of the W/O emulsions increases with increasing surfactant concentration, whereas the EDM performance deteriorates with increasing surfactant concentration. So, taking a comprehensively consideration of the emulsion stability and EDM performance, the concentration of surfactant must be appropriately selected.

Abstract: In this paper, taking the cavity in oxygen-free copper as the object, a set of special honing head suitable for processing the cavity structure of oxygen-free copper are designed and manufactured based on the characters and grindability of materials. The experiment of honing under different grinding parameters has been done for the new honing head. Through the theoretical analysis and test, reasonable honing parameters and optimal abrasive are identified for the honing head. The results shows that the machining-process of honing the cavity of oxygen-free copper by the designed a set of special honing head is conducted smoothly and achieved the good machining effect.

Abstract: High Frequency Short Pulses current power and assisted magnetic field are adopted in the processing experiments of Electrochemical Machining(ECM), which can achieve small gap stable machining about thin-wall surface(10000mm2) of workpiece of aluminum alloy. The experiments show that shaped-surface dimensional deviation of finished workpiece is less than 0.05mm, dimension deviation in thickness ranges between 0.02 and 0.05mm, and surface roughness changes from 0.1 to 0.2μm on the condition that frequency is 1 kHz, duty ratio is 0.45 while voltage is 11V with the magnetic circuit embedded inside clamping fixture. The apparent improvement in machining gap flow field and the advancement in precision as well as surface quality of workpiece are attributed to the intermittence from pulses current, agitation from the pressure wave along with magnetic Lorenz force.

Abstract: The working tooth of traditional cathode can’t change angle with the helix angle changing while processing mixed rifle, so the rifle would be widen and sunken. An assembled cathode comprising a cathode body and ten turntables with teeth was designed, which can do relative motion to body. The step between adjacent turntable teeth being a cause to induce cave and eddy, three schemes were adopted to optimize teeth shape and the gap flow field was simulated by COMSOL. The results show that the gap flow velocity bear on the shape of tooth, while the left side of which was chamfered (R0.24mm) and the right side screw out 0.15mm, the shape of tooth is considered appropriate. The simulation results are consistent with to the experiments.

Abstract: Temperature plays a vital role in the machining industry today. NiCr/NiSi thin-film thermocouples have been deposited on the rake face of polycrystalline cubic boron nitride (PCBN) tools by magnetron sputtering. The typical deposition conditions are summarized. Static and dynamic calibrations of the NiCr/NiSi thin-film thermocouples are presented. The Seebeck coefficient of the TFTC is 37.3 μV/°C. The response time is about 3.9 ms. The testing results indicate that the developed NiCr/NiSi thin-film thermocouple sensors perform excellently when machining A3 steel in situ.

Abstract: WEDM is used to cut quenched and tempered 45 steel samples with up-down abnormity holes by conventional and improved machining process, and time-consuming by various processes is taken to be compared and analyzed. The results show: when cutting a up-down abnormity hole, one time of wire feeding and taking out is lessened and non-working time are effectively reduced by improved process than conventional process; machining processⅡ of two can effectively decrease working time, heat treatment stress releases before cutting straight hole so the final machining size and shape don’t change; the best machining effect can be obtained in cutting up-down abnormity hole by improved machining processⅡ.

Abstract: Electrochemical micro-machining (EMM) has a high removal rate, leaves no residual stress on the surfaces of machined products, and generates a low level of roughness on the surface of machined products. In this work, a novel pulsed power generator is used to support tens of nanosecond duration to drilling. The influences of working parameters, such as pulsed duration, applied voltage, electrolyte concentration, pulse frequency, tool feed rates, and hole depth, on the hole over-cut and conicity in electrochemical micro-drilling are investigated. A high-quality micro hole with a 13.75 μm overcut is drilled into a nickel plate 300 μm thick.