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The fatigue properties of Al-Si alloy cold sprayed Al and Al-SiC composite coatings have been studied. The specimens coated with composites reinforced with a large volume (25%) of fine SiC particles exhibited improved adhesion strength at the interface due to crater formation, and cyclic fatigue lives at room temperature more than three times those of uncoated specimens. In high temperature low cycle fatigue tests at 250uC, the pure Al coatings showed longer fatigue lives than the Al-SiC composite coatings, which is attributed to an increment in ductility at the surface retarding fatigue crack initiation.

In this work, we present a dispersive finite-difference time domain (FDTD) algorithm using a 4-pole complex rational function (CRF). For the sake of a better curve fitting of the 4pole CRF dispersion model, we use a particle swarm optimization technique. We also discuss an efficient memory storage strategy by using a state-space approach. The numerical aspects of 4pole CRF-FDTD -the numerical accuracy and the numerical stability -are investigated in detail. Numerical examples are used to validate 4-pole CRF-FDTD and numerical stability issues are discussed in detail. We also discuss the computational accuracy and the computational efficiency of an arbitrary N -pole CRF-FDTD. Index Terms-Dispersive media, FDTD methods, Numerical stability.0018-926X (c)

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This article presents an accurate finite-difference time domain (FDTD) dispersive modelling suitable for complex dispersive media. A quadratic complex rational function (QCRF) is used to characterise their dispersive relations. To obtain accurate coefficients of QCRF, in this work, we use an analytical approach and a particle swarm optimisation (PSO) simultaneously. In specific, an analytical approach is used to obtain the QCRF matrix-solving equation and PSO is applied to adjust a weighting function of this equation. Numerical examples are used to illustrate the validity of the proposed FDTD dispersion model.