Hunan Provincial Key Laboratory of Safety Design and Reliability Technology for Engineering Vehicle

Changsha, China

Hunan Provincial Key Laboratory of Safety Design and Reliability Technology for Engineering Vehicle

Changsha, China
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Mao C.,Hunan Provincial Key Laboratory of Safety Design and Reliability Technology for Engineering Vehicle | Ren Y.,Hunan University | Gan H.,Hunan Provincial Key Laboratory of Safety Design and Reliability Technology for Engineering Vehicle | Zhang M.,Hunan Provincial Key Laboratory of Safety Design and Reliability Technology for Engineering Vehicle | And 2 more authors.
International Journal of Advanced Manufacturing Technology | Year: 2014

Composites containing ultrafine tungsten carbide/cobalt (WC-Co) cemented carbides and 30 vol% cubic boron nitride (cBN) were fabricated by spark plasma sintering technique. The effect of cBN particles on the densification behavior, microstructure, and mechanical properties of the composites were investigated. According to SEM observation of microstructure, cBN particles are uniformly distributed and have excellent bonding with the cemented carbide matrix. X-ray diffraction analysis shows that there is no indication of phase transformation from cBN to hBN. The addition of very hard dispersed cBN to the WC-Co promotes an increase of hardness, but a decrease of flexural strength. The density and the hardness of cBN-WC-Co composites increase with the increase of the sintering temperature. However, it has the highest hardness of 2,170 HV at 1,370 °C and then the hardness decreases with the further increase of the sintering temperature. © 2014, Springer-Verlag London.


Mao C.,Hunan Provincial Key Laboratory of Safety Design and Reliability Technology for Engineering Vehicle | Zou H.,Hunan Provincial Key Laboratory of Safety Design and Reliability Technology for Engineering Vehicle | Zhou X.,Hunan Provincial Key Laboratory of Safety Design and Reliability Technology for Engineering Vehicle | Huang Y.,Hunan Provincial Key Laboratory of Safety Design and Reliability Technology for Engineering Vehicle | And 2 more authors.
International Journal of Advanced Manufacturing Technology | Year: 2014

The nanofluid is usually applied in minimum quantity lubricant (MQL) grinding to decrease grinding temperature and to improve surface integrity of workpiece. However, a large challenge in the application process of nanofluid is the sedimentation of the nanoparticles due to their poor suspension stability in the base fluid. Then, the lubrication and heat conduction characteristics of nanofluid will be deteriorated, and the nanofluid cannot be atomized as expected during grinding. Therefore, the heat transfer performance of nanofluid during MQL grinding severely decreased. In this study, the force state of nanoparticle in base fluid was analyzed and the effect of dispersant on the force state of nanoparticle was researched. The suspension stability of Al2O 3 (0.5 wt.%) nanofluid was investigated under different ultrasonic vibration times, pH values, and dispersant concentrations (sodium dodecyl benzene sulfonate, SDBS). It is found that the suspension stability of nanofluid is quite poor under short-time ultrasonic vibration condition, and the nanofluid with good suspension stability can be obtained when the ultrasonic vibration time exceeds 0.5 h. A higher concentration of SDBS will lead to a better suspension stability of nanofluid when the concentration of SDBS is quite low. However, if the concentration of SDBS exceeds 0.5 wt.%, there is oversaturated adsorption on the nanoparticles surface which results in the deterioration of suspension stability of nanofluid with the increase of the SDBS concentration. As pH value is below 7, the suspension stability of nanofluid is significantly improved with the increase of pH value. The sedimentation clearly appeared in the disperse system when pH value is higher than 7. The dispersion morphology of the Al2O3 nanoparticles in disperse system is analyzed by using a scanning electron microscope. It is found that some large aggregates appeared when no dispersant was applied in the disperse system, and the Al2O3 nanoparticles are uniformly dispersed in disperse system with the application of the dispersant. © 2014 Springer-Verlag London.


Mao C.,Hunan Provincial Key Laboratory of Safety Design and Reliability Technology for Engineering Vehicle | Mao C.,University of QueenslandQLD | Sun X.,Hunan Provincial Key Laboratory of Safety Design and Reliability Technology for Engineering Vehicle | Huang H.,University of QueenslandQLD | And 3 more authors.
Journal of Materials Processing Technology | Year: 2016

Laser cutting of a cBN-WC-10Co composite material was carried out using a pulsed Nd: YAG laser. The cutting characteristics, as well as the changes in microstructure and mechanical property, were investigated. It was found that cracks were induced by laser machining on the sub-surface and the evidence of phase transformation from cBN to hBN was observed on the cut surface. Cutting parameters had significant effect on the cut surface. A higher laser power produced a smoother cut surface, but a larger heat-affected zone, in comparison to the lower laser power used. No radical cracks were found on the cross-section at the laser power of 100 W. The surface roughness and the heat-affected zone depth decreased with the increased cutting speed and the gas pressure. The material removal involved in the laser cutting of cBN-WC-Co composite was attributed to the melting or evaporation of cBN and WC-Co. The dropping of cBN particles from the cut surface was also found during the cutting at the laser power of 30 W for the loss of the supporting from the WC-Co matrix. © 2015 Elsevier B.V.


Mao C.,Changsha University of Science and Technology | Mao C.,Hunan Provincial Key Laboratory of Safety Design and Reliability Technology for Engineering Vehicle | Zhou X.,Changsha University of Science and Technology | Zhou X.,Hunan Provincial Key Laboratory of Safety Design and Reliability Technology for Engineering Vehicle | And 8 more authors.
International Journal of Advanced Manufacturing Technology | Year: 2015

Efficient application of minimum quantity lubrication (MQL) in grinding is not only related to grinding conditions and delivery parameters but also affected by spraying atomization characteristics. In this study, a double-outlet nozzle is proposed and the flow field of the MQL grinding is investigated by two-stage atomization model. The side-mixing structure of double-outlet nozzle indicates that the grinding fluid is atomized at the windward side and the flow rate of grinding fluid for a single radial hole is smaller than that for the liquid pipe. Therefore, more excellent atomization performances, in terms of liquid droplet size, uniformity, and velocity of the liquid droplets, are obtained for double-outlet nozzle in comparison with single-outlet nozzle. The liquid droplets sprayed from auxiliary outlet of double-outlet nozzle impact on the grinding wheel and change the airflow direction around the grinding wheel. Thus, the air barrier around the grinding wheel is disturbed and the liquid droplets sprayed from main outlet can be injected into the grinding zone easily. Experimental results indicate that two-stage atomization model is reliable. © 2015 Springer-Verlag London

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