The use of a swept frequency alternating current potential difference method for identifying local geometric features within prismatic conductors

Abstract

Potential difference methods are widely accepted as means to detect and monitor cracks in safety critical components. This paper investigates the capability of the potential difference method that uses a swept frequency alternating current excitation (i.e. skin effect with varying current penetration depths) in identifying conductor shapes and features through experiments and finite element analysis. The study focused on samples with the size of 55 mm × 100 mm2 and surface features with opening widths vary from 11% to 42% to the sample size. The method has been investigated by finite element analysis with the capability to distinguish cross-sectional shapes of non-magnetic conductors due to prominent current crowding on surfaces, in which the potential differences measured from a SS316 conductor of triangular cross-sectional shape are higher to those of a circular shape by 77% at 300 kHz. The detection capability of the method has also be confirmed, which is attributed to the impact of feature openings on skin effect. At 50 kHz, potential differences measured across features with the same cross-sectional area of 9 mm2 on EN1A samples rise by 130% as the opening width increase from 11% to 42% to the sample size.