Papers by Author: Wen Ji Xu

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: To study the friction and wear properties of S136/WC-Co friction pair, friction and wear tests in air jet, nitrogen jet and nitrogen cold plasma jet atmospheres are carried out. The morphology and composition of friction surface are analyzed by camera, scanning electron microscope and energy-dispersive X-ray spectroscope. The wear behaviors and mechanism of anti-wear of the three jets to S136 are also discussed. The experiment results prove that the reactive species in the nitrogen plasma jet contribute to the generation of oxidation film on the friction surface quickly to reduce the wear of S136/WC-Co friction pair in real-time.

Abstract: Plasma arc bending of laminated clad metal sheets (LCMS) is a newly developed technique that produces deformation in the LCMS by thermal stress instead of external mechanical force. Since the temperature field leads to the thermal stress, a FEM mode was developed to study the temperature variations in the plasma arc bending of the LCMS which was validated robustness by the experiments. The results show that the temperature variations of the LCMS include the preheating, temperature dramatically changing and cooling stages. The lowest temperature is in the inlet whereas the highest temperature is in the outlet along the heating line. It needs to regulate the energy input of the plasma arc to avoid the possible partial melting of the LCMS.

Abstract: In this paper, a FEM mode was developed to study the feasibility of the plasma arc bending of the laminated clad metal sheets (LCMS) containing defects. The three layer LCMS of stainless steel/mild steel/stainless steel was selected as the sample. The influences of the defects on the temperature field and deformation field were investigated. Besides, the bending experiments were performed to examine the feasibility. The results show that there is a sharp rise of temperature around the defect due to the lower thermal conductivity which causes the possible partial melting of the formed parts. The existence of the defect exacerbates the unevenness of the thickness along the heating line. But the delamination of the interface does not occur because of the instantaneous variations of the stress under the high temperature, which is consistent with the experiments.

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: In this paper the characteristics of pulse electrochemical deburring (PECD) is analyzed through a developed mathematical model and main influencing factors such as applied voltage, pulse duty factor, deburring time, initial burr height and initial interelectrode gap on burr height have been analyzed. The paper also highlights the scheme of the developed PECD system designed to operate within the parametric limits. The calculated results obtained from the mathematical model are found to be approximately consistent with the experimental results. The results show that initial burr height h₀=0.057mm is removed, and the fillet radius R=0.248mm is obtained. The present paper through various parametric studies will act as a guideline for the operation of a PECD system.