Date of Award

6-30-2016

Document Type

Open Access Thesis

Department

Mechanical Engineering

Sub-Department

Aerospace Engineering

First Advisor

Addis Kidane

Abstract

Determining the mechanical response of materials at elevated temperatures is a subject of great interest in metal forming, aerospace and aero-engine industries. For example, measurement of the deformation response under tensile loading at high temperatures is crucial for establishing thermomechanical and thermo-physical properties of materials, consequently, determining the reliability of a component or structure exposed to elevated temperatures. In order to predict the behavior of materials at ultra-high temperatures, a novel experimental approach based on Digital Image Correlation (DIC) is proposed and successfully applied to different materials at temperatures ranging from room temperature to 1100˚C. In these studies, a portable induction heating device equipped with custom made water-cooled copper coils is used to heat the specimens. Two different illumination sources along with optical band-pass notch filters, and a stereo-camera configuration system is used to perform 3D-DIC to analyze stereo-images at a specific temperature.

The effectiveness of the system is demonstrated by successfully performing two different types of experiments; 1) to obtain the coefficient of thermal expansion (CTE) for two different materials, 309 stainless steel and titanium grade II, as a function of temperature, from room temperature to 1100 ˚C, 2) to study tensile response of a 304 stainless steel specimen subjected to quasi-static tensile loading at temperatures between 300oC and 900oC. Numbers of experiments are conducted to study the sensitivity, spatial resolution and repeatability of the DIC measurements. The effect of heat haze on the measurement accuracy is also investigated for this method. Finally, using the temperature and load histories along with the full-field strain data, a Virtual Fields Method (VFM) based approach is implemented to identify the constitutive parameters governing the plastic deformation of the material at high temperatures.

Results from these experiments confirm that the proposed method can be used to measure the full field deformation of materials at ultra-high temperatures subjected to thermo-mechanical loading. Detailed experiment method, analysis and discussion will be presented.

Rights

© 2016, Guillemo A Valeri Paoli

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