A computer simulation technique has been developed to investigate the performance of established and novel laser multilateration schemes. The models focus on analysing the impact of variations in system configuration, optimizing the system self-calibration process and evaluating the volumetric measurement error propagation. Careful optimization of the system configuration and self-calibration planning significantly reduces the uncertainty of system self-calibration and measurement. Comparing the simulated performances of multilateration systems with different number of measurement stations, e.g. four, five and six stations, quantifies the performance improvement obtained by increasing the number of stations. Specific recommendations for optimization of multilateration set-ups and measurement plans and for minimizing measurement uncertainty are set out in the paper. A novel, sequential multilateration set-up for high-precision calibration of small artefacts has been defined, and measurements have been made to support the analysis presented here.
Micro-arc oxidation (MAO) coating was prepared on the surface of TC4 titanium alloy and sealed with (polytetrafluoroethylene [PTFE] + graphite) emulsion to obtain MAO/(PTFE + graphite) composite coating. The surface morphology and phase composition of the MAO coating were studied by scanning electron microscope (SEM) and X-ray diffractometer (XRD). The corrosion resistance of the coating was studied by the potentiodynamic polarization curve and the scanning Kelvin probe (SKP) micro-area voltage. The results show that the TiO 2 ceramic oxide coating formed on the surface of the titanium alloy substrate has the characteristics of porous structure, which will become a channel for corrosive media to enter the coating and accelerate the corrosion of the MAO coating. However, the MAO/(PTFE + graphite) composite coating can prevent corrosive media from entering the coating and improve the corrosion resistance of the composite coating. The corrosion potential increased from 0.146 V to 0.241 V, the corrosion current density decreased from 4.31 × 10 -7 A/cm 2 to 7.92 × 10 -8 A/cm 2 , and the self-corrosion current dropped to one fifth of the MAO coating. In addition, the charge transfer resistance has also increased from 5.305 × 10 4 Ω⋅cm 2 to 2.493 × 10 5 Ω⋅cm 2 .
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