Abstract-This paper brings forward a simple local approximation finite-difference time-domain (FDTD) method for the analysis of short apertures with a finite thickness. By applying the equivalence principle together with a simple local approximation, the varying field distribution is accurately derived. The updating equations for the slot field can be derived by casting the field distributions into the contour paths containing the apertures. The method has been applied to two problems and the results are compared with the high-resolution standard FDTD simulation results and the measurement results. The accuracy of the proposed method is verified from the comparison of both the field distribution and the time-domain and frequency-domain slot coupling results. It is demonstrated that the local approximation is highly efficient and timesaving, and the present method is stable, numerically and computationally efficient.
The cobalt-based Stellite 6 coating with a thickness of 0.5 mm was deposited onto 45 carbon steel by electro-spark deposition technology. Microstructure, chemical composition, phase composition, microhardness distribution and wear resistance of the coating were researched by a series of experiments. The results indicate that, the coating with refined and compact microstructure is mainly composed of Co, Cr 7 C 3 , Co 6 W 6 C and CrCo. The coating makes metallurgical bonding interface with the substrate. Microhardness of the coating is improved significantly with an average value of 827.9 HV 0.5 , which is about 3.6 times that of the substrate. Under the same experimental condition, mass loss of the substrate is about 4.2-4.5 times that of the coating, so the coating shows excellent wear resistance. Main wear mechanism of the coating is abrasive wear at low speed or low load stage, and fatigue wear at high speed or heavy load condition.
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