Boundary Element Method Based Probe Design Model Validation

Abstract

INTRODUCTIONThe mspectwn of aircraft engme components usmg eddy current (EC) techmques has played a vital roJe m the nondestructive evaluatwn mdustry. The objectlve of the mspectwn iS to determme the structural integnty of the components m a nomnvasive manner. The effectiveness of an EC probe design iS often evaluated m terms of the probability of detectwn (POD) of flaws. Many factors need to be considered when estlmatmg the POD. These factors mclude scan and mdex spacmgs, operatmg frequencies, and flaw morphologies. Traditionally, the EC probe design cycle iS JteratJvely performed expenmentally until one eJther meets or exceeds the mimmum reqmred POD. Undoubtedly, this iSatime consummg and expensive process smce a new probe has to be constructed and tested every time the design iS changed. A more sensible approach iS to numencally simulate the functwnality of probes so design improvements can be done iteratively using a computer under a CAD envuonment. The numerical probe design model is developed usmg the boundary mtegral equatwn (BIE) approach. By solvmg the BIEs numencally usmg the boundary element method (BEM), electromagnetic fields produced by the EC probes can be easily obtamed through simple numencal mtegratwn.In the mitml development phase of this model, only femte matenals were allowed. However, improvements to the model have recently been made to also mclude conductive ( or ferromagneue) materials. Therefore, this paper reports the progress made m vahdatmg the new EC probe design model. BACKGROUND