Year

2026

Season

Spring

Paper Type

Master's Thesis

College

College of Computing, Engineering & Construction

Degree Name

Master of Science in Mechanical Engineering (MSME)

Department

Engineering

NACO controlled Corporate Body

University of North Florida. School of Engineering

Committee Chairperson

Dr.Jutima Simsiriwong

Second Advisor

Dr. Alexandra Schönning

Rights Statement

http://rightsstatements.org/vocab/InC/1.0/

Third Advisor

Dr. Vamsi Kalasapudi

Abstract

Aluminum 6061-T6 is commonly used in structural and transportation applications due to its strength-to-weight ratio, corrosion resistance, and ease of manufacturing. In many practical situations, components made from this alloy experience cyclic loading while exposed to environmental conditions such as humidity, temperature changes, and ultraviolet radiation. These factors can affect surface integrity and fatigue performance, especially in the very high-cycle fatigue (VHCF) regime.

This study aims to explore how accelerated weathering impacts the ultrasonic fatigue behavior of Aluminum 6061-T6. First, assess the material through tensile testing to determine its mechanical properties. Then conducted microstructural analysis using optical microscopy, scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD) to evaluate the grain structure and surface condition.

Performed accelerated environmental exposure using an ASTM G154 UV/condensation weathering chamber to mimic moisture-driven surface degradation. Two groups of specimens were exposed for different lengths of time to evaluate the effects of weathering severity. After exposure, ultrasonic fatigue testing was performed at controlled stress amplitudes, and fracture surfaces were examined with SEM to identify mechanisms of crack initiation and propagation. The results show that environmental exposure changes surface characteristics and leads to surface-initiated fatigue cracking. Weathered specimens had a significant reduction in fatigue life when compared to unexposed specimens. This study offers insights into the relationship between environmental degradation and fatigue behavior in Al 6061-T6, enhancing our understanding of durability in structural applications.

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