Date of Award

5-2015

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Mechanical Engineering

Advisor

Dr. Huijuan Zhao

Committee Member

Dr. Fei Peng

Committee Member

Dr. Gang Li

Abstract

Non-destructive testing and evaluation (NDT&E) is a set of techniques commonly used to evaluate a material for the presence of any flaws without actually degrading the material itself. The Alternating Current Potential Drop (ACPD) test method is one of the NDT surface methods used to determine the electrically insulating defects beneath the surface by injection of currents in the structure and measurement of the resulting voltage difference between two or more points on the surface. The presence of defects generally increases the resistance of the structure and hence causes the drop of measured voltage. The inversion of this data can give information about the size and shape of the defects. In the petrochemical and power generation industries, ceramic coatings have been used to be applied to pipe lines in order to increase the strength and high temperature resistance, as well as prevent the pipe lines from corrosion and oxidation. However, traditional ceramic coating materials are electrically insulating. The ACPD testing method cannot be adopted for the NDT purpose. In order to overcome this disadvantage, we proposed a concept of a multi-functional ceramic coating material, in which the metal nanoparticles (such as Nickel) can be uniformly embedded into the ceramic matrix (mullite). This multi-functional ceramic matrix nanocomposite can conduct current via tunneling when the percolation threshold of the filler phase is reached. Therefore, the ACPD test method can still be adopted to predict the defect and crack beneath the surface.

In this research, we adopt the commercial finite element package, COMSOL Multiphysics, to first understand the mechanism of the ACPD method (electromagnetic coupling, skin effect and proximity effect) by the two parallel conductor's model; then investigate the ACPD co-planar conductor model and understand the effect of the ceramic coating material on the sensing signal with various coating conductivities, permeability's and frequencies. Finally, we draw conclusions and make proposals for future research.

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