Project Director

Mahtabi Oghani, Mohammad Javad, 1982-

Department Examiner

Hamdy Ibrahim

Department

Dept. of Mechanical Engineering

Publisher

University of Tennessee at Chattanooga

Place of Publication

Chattanooga (Tenn.)

Abstract

Thanks to its high strength-to-weight ratio and corrosion resistance, Ti-6Al-4V has gained a lot of attention in additive manufacturing (AM) of complex parts with aerospace and medical applications. The realistic loading condition in these applications is mostly cyclic. However, the main challenge with AM of this alloy - and in general AM of metallic parts - is fatigue resistance and durability of the part, which has been reported to be much lower than the conventional materials. In this study, fatigue life performance of three additive manufacturing methods was compared using the Multistage Fatigue model (MSF). MSF model predicts the fatigue life of a material by incorporating microstructural features and defects such as grain size, pore size and pores nearest neighbors. The studied AM methods include Laser Engineered Net Shaping (LENS), Electron Beam Melting (EBM), and Selective Laser Melting (SLM). Each of these processes uses a different method in constructing the three-dimensional object yielding different microstructure. For this work, microstructural data were collected from previous experimental studies. Scanned Electron Microscopy (SEM) images were used to examine the fracture surfaces of the AM specimens and the defects responsible for fatigue failure. MSF divides fatigue life into three stages of crack incubation, microstructurally small crack and long crack stages. With an emphasis on the microstructurally small crack growth and long crack growth, a comparison was performed after calibrating the parameters for each of the AM processes. The results showed the predicted fatigue life is consistent with experimental results. In addition, fatigue resistance governing parameters which were process dependent, were identified for all AM methods.

Degree

B. S.; An honors thesis submitted to the faculty of the University of Tennessee at Chattanooga in partial fulfillment of the requirements of the degree of Bachelor of Science.

Date

5-2022

Subject

Additive manufacturing; Titanium alloys--Fatigue

Keyword

Multistage fatigue, MSF, Additive Manufacturing, Ti-6Al-4V, EBM, LENS, SLM

Discipline

Manufacturing

Document Type

Theses

Extent

8 unnumbered leaves

DCMI Type

Text

Language

English

Rights

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

License

http://creativecommons.org/licenses/by/4.0/

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Manufacturing Commons

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