Estimation of fatigue evolution of aluminum alloy plated with electroless NI–CO–P by using electromagnetic impedance method

• Plating aluminum alloy with Ni–Co–P film increases its fatigue strength by 13−16%.
• The tensile direction is the stress induced “hard axis” of the Ni–Co–P plating.
• In-plane permeability determines the coil impedance for out-of-plane excitation.
• This method can measure fatigue up to saturation of the substrate's residual strain.

We have developed a method for detecting fatigue in aluminum alloys that is based on a applying a ferromagnetic electroless Ni–Co–P plating and then using an electromagnetic impedance (EMI) method to determine its permeability properties by measuring the high-frequency AC impedance of a coil sensor in the presence of a static magnetic field. The results obtained confirmed that this method can estimate the fatigue evolution of a specimen until the point at which the cumulative strain becomes saturated by using measurements obtained by the EMI method under tensile deformation and FEM analysis results.