Eddy current method can be used for non-destructive assessment of residual stress. In order to relate electrical conductivity change to the residual stresses in the welded joints, piezoresistivity of 5A06 has been investigated using samples heat treated at 2500C and 4000C. These samples represent weld zones with different thermal exposure. A directional eddy current probe with a Hall Effect sensor was used to evaluate stress coefficient of electrical conductivity due to applied uniaxial tensile load on the samples. The electromagnetic forward model was solved using FEM package and linear conductivity inversion was formulated to express probe output in terms of electrical conductivity. The piezoresistivity coefficients of samples, calculated from the derivative of stress-conductivity relation, were compared. The results indicate that coefficients vary inversely with annealing temperature.
Portable Soil Electrical Conductivity Sensor System Based on Electromagnetic Pulsed Eddy Current method
