Luke Lowell Weston


Presentation: 10:45-12:00, Kennedy Union Ballroom



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This study investigates the fatigue limiting behavior in aerospace alloys, focusing on the role of Critical Resolved Shear Stress (CRSS) in determining fatigue limits. Initially targeting Ti-6Al-4V (Ti64) for four-point bending fatigue bars using Laser Powder Bed Fusion (LPBF), challenges with contaminated Ti64 powder led to a shift to martensitic 17-4PH stainless steel (17-4 stainless). The research explores the impact of CRSS on fatigue limits, emphasizing its importance over slip systems per Mlikota's findings. Surface roughness analysis of the 17-4 stainless bars revealed a consistently higher average roughness, sharpness of peaks and valleys, and most importantly depth of valleys on the as-built side compared to the cut side. xCT scanning showed a 99.02% density obtained from the “high quality” parameter set, which would be suitable for many structural applications. However, the ordered networks of pores along the hatching suggest that material from this parameter set could never be considered airworthy due to the high surface area to volume ratio/surface energy. The manufacturers "normal" parameter set yielded 99.99% dense bars as measured by xCT, which is better than most castings.This research contributes to the understanding of the importance of CRSS in aerospace structural design and the fatigue limiting behavior of aerospace-relevant alloys. The findings emphasize the need for further investigation into the relationship between CRSS, slip systems, and the design of materials with infinite fatigue lives. With a proper understanding of the influence of CRSS on fatigue limiting behavior, it may be possible to develop aerospace alloys with infinite fatigue lives, greatly lowering maintenance costs.

Publication Date


Project Designation

Graduate Research

Primary Advisor

Li Cao

Primary Advisor's Department

Chemical and Materials Engineering


Stander Symposium, School of Engineering

Institutional Learning Goals


Fatigue Limiting Behavior of LPBF Parts (AM Process Improvement)