N. Tralshawala, H. Sun, W. Faidi, Y. Plotnikov, GE Global Research Center, Niskayuna, NY; W. McKnight, GE Aviation, Cincinnati, OH
The measurement of variations in the materials property (MP) with depth of various surface treated metals and alloys is typically accomplished by destructive methods such as sectioning and/or hole drilling of the surface and then using x-ray diffraction to estimate MP variations as a function of depth. The relationship between the residual stress and electrical conductivity or thermoelectric properties has been investigated to develop nondestructive techniques for this task.This work describes results obtained from multi-frequency eddy current and thermo-EMF measurements of MP. Small (1.5-3 mm) flexible spiral printed coils were used for the eddy current method. Detailed electromagnetic simulations were carried out to model the coil impedance changes as a function of frequency and material conductivity. Experimentally obtained appeared eddy current conductivity profiles will be presented. Simulations were also performed to optimize parameters for the non-contact thermoelectric system, where thermoelectric currents are detected using the magnetic fields they generate. Surface profiles of the magnetic field were obtained for a given thermoelectric potential difference. Criteria for the magnetic sensor selection will be discussed. Initial data for the proof-of-concept will be shown.
