DEVELOPMENT OF AN EDDY-CURRENT SENSOR AND ALGORITHM FOR THREE-DIMENSIONAL QUANTITATIVE NONDESTRUCTIVE EVALUATION

THE PROPOSED RESEARCH PROBLEM IS TO DEVELOP A SENSOR, TOGETHER WITH A MATHEMATICAL ALGORITHM, THAT WILL ALLOW THE THREE-DIMENSIONAL QUANTITATIVE EDDY-CURRENT NONDESTRUCTIVE EVALUATION OF MATERIALS AND STRUCTURES. THE APPROACH THAT WE PROPOSE IS BASED ON, AND EXTENDS, WORK ON TWO-DIMENSIONAL EDDY-CURRENT NDE THAT HAS ALREADY BEEN PERFORMED BY ANALYTICS, INC. THAT WORK IS BRIEFLY REVIEWED.THE TECHNICAL OBJECTIVES OF THE PROPOSED RESEARCH ARE: (1) DETERMINE SUITABILITY OF HALL-EFFECT PROBES FOR SENSING EDDY-CURRENTS, (2) DETEMINE OPTIMUM ARRAY OF HALL-EFFECT PROBES FOR THE SENSOR, (3) DETERMINE SUITABILITY OF DISTRIBUTED WINDINGS AND/OR "PHASED-ARRAYS" FOR SENSING, OR INDUCING, EDDY-CURRENTS, AND (4) EXTEND THE ALGORITHM FOR RECONSTRUCTING FLAWS IN TWO-DIMENSIONS TO THREE DIMENSIONS. THESE OBJECTIVES ARE MET BY ANALYZING A MODEL SENSOR, WHICH IS DESCRIBED. THE ANALYSIS IS BASED ON CERTAIN INTEGRAL RELATIONS FOR EDDY-CURRENTS. THESE INTEGRALS ARE DERIVED FROM FUNDAMENTAL ELECTROMAGNETIC THEORY, AND ARE THE FOUNDATION FOR OUR INVERSION TECHNIQUE.