Abstract

A current critical necessity for all industries which utilize various equipment that operates in high temperature and extreme environments, is the ability to collect and analyze data via non destructive testing (NDT) methods. Operational conditions and material health must be constantly monitored if components are to be implemented precisely to increase the overall performance and efficiency of the process. Currently in both aerospace and power generation systems there are many methods that are being employed to gather several necessary properties and parameters of a given system. This work will focus primarly on two of these NDT methods, with the ultimate goal of contributing to not only the method itself, but also the role of numerical computation to increase the resolution of a given technique. Numerical computation can attribute knowledge onto the governing mechanics of these NDT methods, many of which are currently being utilized in industry. An increase in the accuracy of the data gathered from NDT methods will ultimately lead to an increase in operational efficiency of a given system. The first method to be analyzed is a non destructive emmision technique widely referred to as accoustic ultrasonic thermography. This work will investigate the mechanism of heat generation in acoustic thermography using a combination of numerical computational analysis and physical experimentation. Many of the challenges typical of this type of system are addressed in this work. The principal challenges among them are crack detection threshold, signature quality and the effect of defect interactions. Experiments and finite element based numerical simulations are employed, in order to evaluate the proposed method, as well as draw conclusions on the viability for future extension and integration with other digital technologies for health monitoring. A method to determine the magnitude of the different sources of heat generation during an acoustic excitation is also achieved in this work. Defects formed through industrial operation as well as defects formed through artificial manufacturing methods were analyzed and compared. The second method is a photoluminescence piezospectroscopic (PLPS) for composite materials. The composite studied in this work has one host material which does not illuminate or have photoluminescence properties, the second material provides the luminescence properties, as well as additional overall strength to the composite material. Understanding load transfer between the reinforcements and matrix materials that constitute these composites hold the key to elucidating their mechanical properties and consequent behavior in operation. Finite element simulations of loading effects on representative embedded alumina particles in a matrix were investigated and compared with experimental results. The alumina particles were doped with chromium in order to achieve luminscence capability, and therefore take advantage of the piezospectrscopic measurement technique. Mechanical loading effects on alumina nanoparticle composites can be captured with Photo stimulated luminescent spectroscopy, where spectral shifts from the particles are monitored with load. The resulting piezospectroscopic (PS) coefficients are then used to calculate load transfer between the matrix and particle. The results from the simulation and experiments are shown to be in general agreement of increase in load transferred with increasing particle volume fraction due to contact stresses that are dominant at these higher volume fractions. Results from this work present a combination of analytical and experimental insight into the effect of particle volume fraction on load transfer in ceramic composites that can serve to determine properties and eventually optimize various parameters such as particle shape, size and dispersion that govern the design of these composites prior to manufacture and testing.

Graduation Date

2018

Semester

Summer

Advisor

Ghosh, Ranajay

Degree

Master of Science in Mechanical Engineering (M.S.M.E.)

College

College of Engineering and Computer Science

Department

Mechanical and Aerospace Engineering

Degree Program

Mechanical Engineering; Mechanical Systems

Format

application/pdf

Identifier

CFE0007272

URL

http://purl.fcla.edu/fcla/etd/CFE0007262

Language

English

Release Date

August 2018

Length of Campus-only Access

None

Access Status

Masters Thesis (Open Access)

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