Advanced Materials Research Vols. 189-193

Abstract: High strength, high ductility and low thermal conductivity cause the austenitic stainless steels to be hard materials to machine so that heat concentrates at the tool cutting edge due to their properties. This study aims to optimize turning parameters of AISA 304 stainless steel. Turning tests have been performed in three different feed rates (0.2, 0.3, 0.4 mm/rev) at the cutting speeds of 120, 160 and 200 m/min. An analysis of variance (ANOVA) has been made to determine the effects of each parameter on the tool wear and the surface roughness using the Taguchi approach. It is being inferred that cutting speed has the main influence on the flank wear and as it increases to 200 m/min, the flank wear decreases. The feed rate has the most important influence on the surface roughness and as it decreases, the surface roughness decreases as well.

Abstract: When lubricants are used according to special requirements, it is possible to achieve considerable cost savings. Compared to conventional coolant cooling technology used in metal cutting, oil-air lubrication increases cooling performance, avoids environmental pollution, reduces running and maintenance costs. The cutting temperature contrast experimental research was based on close to practice 45# steel in dry cutting, wet cutting and oil-air lubrication conditions. The research work concentrated on the superiority of oil-air lubrication cooling and the influence of cutting amount on temperature. The experimental results show that oil-air lubrication is more effective in reducing the cutting temperature than wet cutting or dry cutting, this paper details the cutting temperature curves at several different tests provides a basis for industrial production, improves the level of machining process and the significance was being reported.

Abstract: In this paper, metal-bonded diamond wheels of different sized abrasive grain with different porosity were fabricated. Grinding experiments with these wheels on three kinds of materials were carried out under different grinding conditions. Experimental results revealed that wheel with high porosity (38%) had smaller grinding forces and specific energy than the one with a medium porosity (24%) on grinding G603. However, on grinding harder materials like Red granite or ceramics of Al₂O₃, the wheel with 38% porosity had bigger grinding forces and specific energy than the wheel with 24% porosity. Both wheels exhibited good self-sharpening capability during the grinding process of G603 and Red granite, but on grinding ceramics of Al₂O₃ the wheel with 38% porosity displayed in dull state during the grinding process . With the same porosity, the grinding forces of the wheel with a grain size of 230/270 US mesh were lower than the one with a grain size of W10 when grinding Red granite and ceramics of Al₂O₃. However revising results were obtained on grinding G603.

Abstract: The vibration tapping technology has been employed with success on some difficult-to-machine material such as titanium alloy, hardened steel and so on. However, there are very few studies on the application of the torsion vibration tapping in particle reinforced aluminum. The tapping performance of small size thread holes in particle reinforced aluminum matrix composites Al₂O₃p/Al and SiCp/Al during common tapping and low-frequency vibration tapping using high speed steal(HSS) machine-used taps is researched experimentally in this work. The influence of vibration parameters, e.g. cutting speed V, net forward angle of each stroke LT and times of repeat cutting Q on tapping torque, tool wear, tool life and quality of thread holes is investigated during the experimentation. The results show that the common vibration tapping with small amplitude, relatively high frequency and a lot of repeat cutting times suit to tap the Al₂O₃p/Al, whereas the step vibration tapping with large amplitude, relatively low frequency and a few repeat cutting times suit to tap the SiCp/Al due to difference performance of the two kinds of material. The influence of Q and LT on the quality of thread holes, tapping torque and tool life is sensitive on the Al₂O₃p/Al, whereas the influence of V and Q on the quality of thread holes, tool wear and tool life is sensitive on the SiCp/Al. Furthermore, the optimum vibration parameter in the Al₂O₃p/Al by dry cutting is cutting speed of 400r/min, net forward angle of each stroke of 1.5°, backward angle of each stroke of 45°. The optimum vibration parameter in SiCp/Al by dry cutting is cutting speed of 220r/min, net forward angle of each stroke of 420°, backward angle of each stroke of 430°. From the test results and micrographs, it was observed that the particle could be fractured on the surface finish on tapping processing. The proper vibration tapping parameter can void the adhesion in the tap flute, decrease the tapping torque, improve the quality of thread hole and prolong the tap life.

Abstract: Cutting process of manual self-propagating high-temperature synthesis (SHS) cutting technology was studied based on industrial Q235 steel specimen and cut material of cutting pen. Through research of kerf and analysis of manual SHS cutting process, three zones of base metal is formed under the cutting pen process: molten zone heated directly by cutting pen, the common active zone of cutting pen , metal flow and slag flow, metal flow and slag flow heating zone. Its cutting process can be divided into four inter-related stages as follows: the formation stage of the molten pool, the increasing stage of the pool penetration, the stage of slag blowing off and kerf formation and then the formation stage of a new pool. The way to improve efficiency of manual SHS cutting technology is proposed at the end.

Abstract: Drilling is a semi-enclosed cutting process. Drilling of difficult-to-machine materials generates thermal/frictional damage at the cutting edges of drill bit and decreases the life. In this paper, a new cooling and lubricating technique in drilling difficult-to-machine materials is developed to improve the life of drill bit. For this study, a water vapor generator and feeding system is developed. Comparative experiments are performed for various difficult-to-machine materials under the conditions of oil water emulsion, water vapor as coolant and lubricant and dry drilling, respectively. The effectiveness of water vapor on the basis of drill bit wear is studied. Experimental results show that with water vapor as coolant and lubricant the flank wear is reduced by 45-80% and 10-15% in comparison with dry drilling and oil water emulsion, respectively.

Abstract: Nanopores etched in the solid-state membranes have become the hotpot of nanotechnology research. Various methods for fabricating solid-state nanopores have been developed and reported, but the fabrication of nanopore is also a difficult challenge. In this paper, we milled nanopores of different sizes in the free-stand and low-stress solid-state membranes. And then the area around nanopores were scanned with the diffused ion beam, we found that the sediment around will melt and the shape of the nanopore becomes circular.

Abstract: In connection with the process of glaze ice, prediction models about height and thickness of ice coating under uniform and non-uniform ice accretion of wire are presented by taking into account local collision efficiency, freeze coefficient and collection coefficient based on the existing model at home and abroad. The time-dependent ice models on the conditions of different median volume diameter of super-cooled droplets, wind speed and wire diameter are analyzed. Compared with the existing model, the proposed ice accretion model performed well in predicting ice’s weight and thickness. At the same time, it can give some lights on ice disaster and anti-icing design for power transmission lines.

Abstract: The effects of fluxes with different activators (sebacic acid and diethylamine hydrochlcoride) on the wetting behavior of Sn-Zn lead-free solders were investigated. The wettability tests showed that fluxes with the addition of single sebacic acid or diethylamine hydrochlcoride significantly improved wettability of Sn-Zn solder on Cu substrate. However, fluxes with combined additions of above activators promoted wetting performance of the solder further. Thermal analysis (thermal-gravimetry analyzer and differential scanning calorimeter) results demonstrated that the effective temperature range of diethylamine hydrochlcoride is higher than that of sebacic acid. So diethylamine hydrochlcoride could react with oxides on the solder and substrate surfaces at a wider temperature range which resulted in an enhanced spreading of solders. Scanning electron microscopy (SEM) image showed that two kinds of diffusion layers were formed between Sn-Zn solder and Cu substrate, indicating fluxes with binary activators markedly improved welding quality of Sn-Zn solder.

Abstract: The cause of ice accretion of transmission line and ice accretion mechanism are both summarized systematically. The mechanism of ice coating of wire caused by thermodynamics, fluid mechanics and the current electric field coupling is pointed out. In connection with the process of glaze ice, the existing models at home and abroad for the prediction of height and thickness of ice coating are summarized and analyzed, it can give some advises on further study of ice accretion prediction and some lights on ice disaster and anti-icing design for power transmission lines.