Abstract
As a novel nondestructive testing technique, capacitive imaging (CI) has been used to detect the defects within the insulation layer and metal surface in an insulated metallic structure, i.e. pipe or vessel. Due to the non-linearity of the probing field, the defects at different depths in the insulation layer are difficult to compare using the conventional CI sensor with a single pair of electrodes. In addition, the conventional CI sensor cannot provide adequate information to discriminate the defects in the insulation layer and metal surface. In order to solve the above mentioned problems, the multi-electrode capacitive sensor is introduced. The multi-electrode capacitive sensor uses multiple quasi-static fringing electric fields generated by an array of coplanar electrodes to obtain extra information about the defects in the specimen. In this work, the Measurement Sensitivity Distributions (MSDs) of the multielectrode capacitive sensor were acquired using the FEM models, and used as a tool to predict the sensor response due to defect at different depth. Experimental results show that the Dynamic Change Rates (DCRs) of the measured values in insulator layer and metal surface present different variation patterns, which can be used to discriminate these two kinds of defects. In addition, it was demonstrated that the different depths of two defects in the insulation layer can be compared by comprehensive analysis of the detection results from all the electrode pairs.
How to Cite:
Li, Z. ., Yin, X. ., Gu, Y. ., Chen, G. ., Li, W. ., Li, Z. ., Yin, X. ., Gu, Y. ., Chen, G. . & Li, W. ., (2019) “Discriminating the defects in the insulation layer and metal surface using multi-electrode capacitive sensor”, Review of Progress in Quantitative Nondestructive Evaluation .
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