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

Nondestructive Evaluation (NDE) is a multidisciplinary field of research, which is focused on the development of analysis and measurement technologies for the quantitative characterization of materials, components and structures. It is a key process used in product evaluation, troubleshooting for the quality assurance in industry. Sonic Infrared (IR) Imaging technology is a hybrid sensing and imaging technique, in which cracks in an object are caused to become visible in the infrared imaging through frictional heating associated with the application of a short pulse of low-frequency ultrasound. The technique uses pulses of ultrasonic excitation applied to a sample for a fraction of a second. The heating at the crack is then captured by calibrated infrared cameras using real-time video/digital imaging. It's been demonstrated that this technique can detect surface and subsurface cracks, delaminations, and disbonds in metallic and composite materials successfully. As a promising NDE technique, ultrasonic Infrared Imaging technique has gain more attention from researchers and technicians in NDE community, it has been used in detecting cracks/defects in the automotive and aerospace industry for several years.

The purpose of the research work is to comprehensively study the non-linear effect of coupling materials used in the technique, where a coupling material is a thin layered material that separates transducer and sample. In this research, a series of coupling materials are investigated, and a comprehensive analysis, using different engagement force or different pulse frequency on two commonly used aluminum samples with different geometries and structures are studied. The combination of vibration waveforms and IR images/signals is used as an analysis method for the comprehensive study. Correlation analysis between the acoustic and thermal energy in the crack is discussed, as well. The finite element analysis is used to predict the thermal-mechanical behavior of the cracks in the samples under different boundary conditions by using different coupling media, different loading force and pulse frequency. FEA results are validated with the test results side by side. It is verified that coupling material can play an important role in crack detection.

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