Damage-Monitoring Smart Washer Based on Rosette Eddy Current Sensor.

To meet the need of monitoring the crack damage located at bolt hole of metallic bolted-joint structure, a kind of damage monitoring smart washer with rosette eddy current sensor was proposed. The influences of washer electromagnetic properties on monitoring capability were analyzed based on constructed semi-analytic model, and experiment of 2A12-T4 aluminum alloy under constant loading spectrum was carried out to validate analysis results. Semi-analytic model results show that amplitude ratio variation of smart washer increases with washer relative permeability, while decreases with washer conductivity. The result of fatigue crack monitoring experiment of 2A12-T4 aluminum alloy under constant loading spectrum verifies the damage monitoring capability of smart washer with aluminum alloy and stainless steel materials. However, monitoring curve of smart washer with stainless steel material is smoother than that with aluminum alloy material, which indicates that the smart washer with steel stainless material has a better monitoring capability. The first channel of smart washer is capable of monitoring on accumulated damage and the other three channels are capable of quantitative monitoring on fatigue crack, with monitoring precision of 1 mm. [ABSTRACT FROM AUTHOR]