Degree

Doctor of Philosophy (PhD)

Department

Mechanical Engineering

Document Type

Dissertation

Abstract

A detailed evaluation of fatigue crack growth (FCG) in a silicon-modified Inconel 939 alloy, fabricated via laser powder bed fusion additive manufacturing (L-PBF AM), was performed using cyclic bending tests on pre-notched microscale cantilevers with a cross-sectional dimension of 25 µm × 25 µm. To our knowledge, this study is the first to demonstrate that such microscale cantilever tests can effectively capture both the threshold and Paris-law regimes of FCG, despite the limited specimen size. The precise fabrication of these small-scale specimens allows for controlled fatigue crack propagation relative to the microstructure while minimizing the presence of volumetric defects. Notably, significant variations in FCG behavior were observed when the crack propagation direction was changed from parallel to perpendicular to the AM build direction. This study highlights the effectiveness of microscale specimens for FCG assessment, offering valuable insights into the relationship between microstructural characteristics and crack growth behavior.

Date

12-13-2025

Committee Chair

Wen Jin Meng

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