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


In order for additive-manufactured parts to become widely utilized and trusted in application, their mechanical properties must be characterized. This study investigates the fatigue behavior and failure mechanisms of Ti-6Al-4V specimens fabricated using Laser Engineered Net Shaping (LENS), an additive manufacturing (AM) process. Fully-reversed strain-controlled fatigue tests were conducted on Ti-6Al-4V specimens manufactured via LENS in their as-built and heat-treated conditions. Scanning Electron Microscopy (SEM) is used to examine the fracture surfaces to qualify the failure mechanism, crack initiation sites, and defects. Due to the relatively high localized heating and cooling rates experienced during deposition, fabricated parts possess anisotropic microstructures and different mechanical properties than those of their traditionally-manufactured wrought counterparts. Porosity promotes unpredictable fatigue behavior, as evidenced by data scatter. Pore shape, size, location, and number were found to impact the fatigue behavior of additive-manufactured parts.