Engineering Commons^™

Creep Behavior Of A Ti-Based Multi-Principal Element Alloy, Benjamin Elbrecht

All Theses

Abstract

The understanding of microstructural damage mechanisms is the foundation of better understanding existing materials and future material development. There are significant challenges to measuring these damage mechanisms in-situ as continuous observation of the state of the microstructure is difficult or impossible for many experimental setups. This thesis presents a method for measuring grain boundary sliding (GBS) and local strain concentrations in-situ via a Heaviside function based algorithm. GBS is the shearing of two grains along their shared grain boundary and is a common damage mechanism in creep which presents as a discontinuity that can be measured with a Heaviside …

Off Axis Compressive Response Of Ice-Templated Ceramics, Rahul Kumar Jujjavarapu

Mechanical & Aerospace Engineering Theses & Dissertations

The off-axis compressive behavior of ice-templated ceramic was analyzed using experimental results and micro-mechanical model simulation. Ice-templated ceramics is a versatile processing technique used to manufacture anisotropic ceramic foam by exploiting the anisotropic growth characteristics and lamellar morphology. The ice-templating process results in processing-structure-property relationships determined by the microstructure. The processed alumina samples which were later manufactured by water jet machine from the freeze casting were tested under quasi-static off-axis loading conditions and were used to determine the mechanical properties of the material. Digital image correlation (DIC) was used to measure the strain response of ice-templated ceramic under off-axis loading. …

On The Feasibility Of Tailoring Copper-Nickel Functionally Graded Materials Fabricated Through Laser Metal Deposition, Sreekar Karnati, Yunlu Zhang, Frank W. Liou, Joseph William Newkirk

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In this study, pulse‐width modulation of laser power was identified as a feasible means for varying the chemical gradient in copper—nickel‐graded materials. Graded material deposits of 70 wt. %. copper‐30 wt. %. nickel on 100 wt. %. nickel and vice versa were deposited and characterized. The 70/30 copper—nickel weight ratio in the feedstock powder was achieved through blending elemental copper and 96 wt. %. Ni—Delero‐22 alloy. At the dissimilar material interface over the course of four layers, the duty cycle of power was ramped down from a high value to optimized deposition conditions. This change was theorized to influence the …

A Novel Approach To Analyzing Strain Heterogeneity In Polycrystalline Quartz Specimens Deformed At High Pressure And Temperature, Nolan Ambrose Regis

UNLV Theses, Dissertations, Professional Papers, and Capstones

Rheological studies of rocks and minerals allow researchers to study the grain-scale deformation mechanisms that govern large-scale geologic processes from mountain building to mantle mixing. Deforming rock samples with high pressure and temperature apparatuses similar to the Griggs piston cylinder apparatus allows us to simulate deformation at depth. However, many apparatuses are limited to “cook-and-look” analysis and require modeling techniques to determine the evolution of deformation patterns found in experimental samples. A previous study used two-dimensional finite element models to analyze the development of stress and strain patterns in polycrystalline rocks. The study suggested rhythmic patterns in deformed rocks develop …

Evaluation Of Strain Distortion Correction Protocol Using Scanning Electron Microscopy And Digital Image Correlation, Alexandra Mallory, Alberto Mello, Michael Sangid

The Summer Undergraduate Research Fellowship (SURF) Symposium

Scanning electron microscopy in combination with digital image correlation (SEM-DIC) is a useful technique for measuring strain in materials at the micro-scale. In particular, it can be used to identify micro-scale strain localizations that are the precursor to material failure. While SEM produces high resolution images of the microstructure, the images also contain a large amount of distortion that, during DIC, will result in distorted strain values that require correction. In this project, a nickel-based alloy underwent cyclic mechanical fatigue at three different high temperatures to a targeted maximum strain. Scanning electron microscopy imaging was done on a 200x150μm area …

Banded Microstructure In 2024-T351 And 2524-T351 Aluminum Friction Stir Welds: Part Ii. Mechanical Characterization, Michael Sutton, Bangcheng Yang, Anthony Reynolds, Junhui Yan

Anthony P. Reynolds

No abstract provided.

A Methodology For Use Of Digital Image Correlation For Hot Mix Asphalt Testing, Estefany Ramos

Open Access Theses & Dissertations

Digital Image Correlation (DIC) is a relatively new technology which aids in the measurement of material properties without the need for installation of sensors. DIC is a noncontact measuring technique that requires the specimen to be marked with a random speckled pattern and to be photographed during the test. The photographs are then post-processed based on the location of the pattern throughout the test. DIC can aid in calculating properties that would otherwise be too difficult even with other measuring instruments.

The objective of this Thesis is to discuss the methodology and validate the use of DIC in different hot …

Digital Image Correlation Of Heterogeneous Deformations In Polycrystalline Material With Electron Backscatter Diffraction, Javier Esquivel

Open Access Theses

This work establishes the ability to conduct digital image correlation (DIC) investigations at varying length scales. DIC allows for a computational method of strain field measurements using multiple images to track random speckle patterns on material surfaces. The use of a powder silicon oxide speckle allows for high optical magnification correlation using conventional load frames. Self-assembling gold nanoparticles provide sub-micron resolution speckle patterns to study microstructure influences on deformation using scanning electron microscopy. The complex microstructure in aerospace grade aluminum and nickel-based superalloys, give rise to varied deformation fields, which can be studied using electron backscatter diffraction. Specimen preparation techniques, …