Thesis Defense Announcement

The Herff College of Engineering announces the Final Thesis Defense of

Jingzhe Zhang

for the Degree of Master of Science

on December 3, 2018 at 9:00 AM in Engineering Science Building

Advisor: Ali Fatimi

Surface Roughness Effect on Multiaxial Fatigue Behavior of Additive Manufactured Metals and Its Modeling

ABSTRACT: Additive manufacturing (AM) has become a very popular topic recently due to its many advantages including short build cycles, convenience of customization, and most importantly the ability to build components with complex geometry. However, the surface condition of additive manufactured components is not always satisfactory, particularly with respect to fatigue perfor-mance. This is because the as-built surface tends to be rough and post surface treatments or pro-cesses such as machining and polishing may not be applicable to all AM parts. On the other hand, since many components are under cyclic loading consisting of normal and shear stresses, multiax-ial fatigue behavior is one of the most important aspects to evaluate. This paper evaluates the sur-face roughness effect on fatigue behaviors of Ti-6Al-4V alloy samples additively manufactured by laser based powder bed fusion method (L-PBF). Fully reversed axial, torsional, and combined axial-torsion fatigue tests were conducted on specimens with different surface conditions and with different post heat treatments (annealed and HIP). Fatigue life predictions were made using linear elastic fracture mechanic with satisfactory results, as compared to experimental results.