Eddy Current Arrays for Structural Health Monitoring

Abstract

Conventional eddy current testing is commonly used for nondestructive testing, primarily to detect surface breaking flaws in metals by physically moving an ET sensor across a material surface. However, eddy current testing has not yet achieved broad use in structural health monitoring. The primary advantage of permanently installed eddy current sensors for structural health monitoring is the inspection of difficult-to-access locations as a replacement for conventional eddy current testing. Structural health monitoring with eddy current sensors can be implemented either with (i) sensors installed with cables only, where portable electronics is periodically attached at an accessible location to record inspection data; or (ii) sensors installed with associated electronics to enable continual data acquisition during service. The first format is the most practical replacement for conventional nondestructive testing at challenging access locations. The second approach with installed electronics offers observability throughout the part life during service loading, but has far greater implementation and acceptance challenges. This article is focused on the use of next generation eddy current arrays that are now in use for structural health monitoring. These next generation arrays enable coverage of larger areas, surface and subsurface crack detection and monitoring of other properties of interest such as temperature and stress under some conditions. Nondestructive testing uses for these sensors are provided in the references and also offer significant value for structural integrity.