Theses and Dissertations

Issuing Body

Mississippi State University


Shamsaei, Nima

Committee Member

Thompson, Scott M.

Committee Member

Daniewicz, Steven R.

Date of Degree


Original embargo terms

MSU Only Indefinitely

Document Type

Graduate Thesis - Campus Access Only


Mechanical Engineering

Degree Name

Master of Science


James Worth Bagley College of Engineering


Department of Mechanical Engineering


The trustworthiness of AM metallic materials is not well characterized. Therefore, fatigue models that consider the unique microstructure and porosity inherent to AM parts are needed. Herein, a microstructure-based fatigue model is calibrated for use in predicting fatigue life of additively manufactured (AM) Ti-6Al-4V. Various Ti-6Al-4V samples, with variations in porosity, were fabricated using Laser Engineered Net Shaping (LENS), a Direct Laser Deposition method. LENS samples in the as-built and heat treated conditions, together with wrought Ti-6Al-4V samples, underwent fatigue testing, as well as microstructure and fractographic inspection. The collected microstructure/defect statistics were used for calibrating a microstructure-sensitive fatigue model. LENS Ti-6Al-4V sample fatigue lives were found to be consistently less than those of the wrought Ti-6Al-4V samples, due to the presence of pores/defects within the LENS material. Results further indicate that fatigue life predictions from the employed model were in close agreement with experimental results.