Papers by Author: Xin Liu

Abstract: The applicability of diamond cutting is greatly restricted due to the serious chemical wear for the machining of ferrous materials. The processes of diamond natural graphitization and graphitization in diamond/Fe interface were analysed by molecular dynamics (MD). Simulation proved that the graphitization temperature decreased from 5215 K of natural graphitization process to 1300 K at diamond/Fe interface, and diamond which near the Fe atoms was graphitized firstly. Diamond tool wear behavior during ordinary cutting and ultrasonic elliptical vibration cutting (UEVC) of NAK80, S136 was analysed. Results showed that the diamond tool wear decreased greatly in UEVC. MD Simulation and cutting experiments both demonstrated that lowering the temperature of the interface could effectively reduce the wear of diamond tool.

Abstract: Superhydrophobic surfaces on metal substrates are often prepared via roughing the surfaces and lowering their surface energy. The superhydrophobic aluminum surface with a water contact angle of 162.5° and rolling angle less than 6° was fabricated via electrochemical etching and re-deposition using the alkalic Na3PO4 electrolyte and then fluorination treating. The surface morphology and chemical composition were characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The results show that the surface consists of the micrometer-scale lumps and protrusions, and many nanometer-scale mastoids are filled in these protrusions. These hierarchical micro/nanometer-scale binary structures, which are similar to the micro-structures of lotus leaf surfaces, play an important role in achieving superhydrophobicity. The main components of the binary geometric structures are Al2O3, AlPO4, and H2O. The effects of the processing time and processing voltage on the macro-morphology were also investigated. The macro-rough structures appeared on the edge of the aluminum surface firstly, and then spread gradually to the entire surface.

Abstract: Electric hot machining (EHM) can improve the cutting performance by heating resistance, consisting of metal resistance and constriction resistance, which softens the material in the deformation zone. In this paper, we present the 3D model for heating resistance and analyze its variance with experimental verification. The results show that 3D model for heating resistance can describe heating resistance well in EHM under this experiments condition.

Abstract: Dry electrostatic cooling (DESC) assisted machining is one of the green machining technologies that uses ionized air flow as lubricating and cooling medium in the machining process. The influence of discharge parameters on the efficiency of ion transport and ozone concentration in the DESC is experimentally researched. The results show that the efficiency of ion transport increases with the rising of the discharge current and air pressure, but decreases with the rising of the distance from the nozzle and the nozzle diameter. The tungsten electrode is used to obtain high ozone concentration with the nozzle diameter of 2-4mm, air pressure of 0.2-0.4MPa, and the distance from the nozzle within 0.5mm. Experimental research on the DESC assisted machining for hardened steel GCr15 shows that cutting force decreases by 7%-28%, tool wear reduces by 30-50%, and tool life is 1.5-3.3 times more than dry cutting. Better results are achieved when increasing the cutting speed.