Access Type

Open Access Dissertation

Date of Award

January 2014

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Electrical and Computer Engineering

First Advisor

Xiaoyan Han

Abstract

Sonic Infrared (IR) Imaging Nondestructive Evaluation (NDE) technology has shown inherent advantages, such as fast detection for all direction and all dimension flaws, for both metal and composite materials. The purpose of this dissertation is to study and investigate the physical process of two most important methods, frequency sweep excitation and chaotic excitation, to improve the defect detection ability of Sonic IR technology.

The tool used in our study is known as finite element analysis (FEA). According to test process of Sonic IR technology, some special technologies were developed in FEA simulation, such as creating cracks with flat contact surfaces in turbine blade models, two-step simulation method to apply static force and then driving the transducer, and defining frequency sweep exciting curves. The results of simulation indicate that frequency sweep excitation has the ability to compare the thermal power produced from a crack with different exciting frequency in one shot and locate the exciting frequency producing the maximum thermal power. The foundation process of chaotic vibration was demonstrated in FEA simulation and the requirements of producing a stable chaotic vibration were put forward. The simulation results also explained the evenly distributing property of chaotic frequencies and related it to the natural frequencies.

The significance of this dissertation is to present following students what is Sonic IR technology, how it works, how to study this technologies with experiments and FEA simulation. The most important one is how to use some basic physical concepts to guide the FEA simulation.

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