Date of Graduation
5-2016
Document Type
Thesis
Degree Name
Bachelor of Science in Mechanical Engineering
Degree Level
Undergraduate
Department
Mechanical Engineering
Advisor/Mentor
Spearot, Douglas
Committee Member/Reader
Nair, Arun
Committee Member/Second Reader
Zou, Min
Abstract
Hydrogen embrittlement is a main factor in the premature failure of metals under stress. Using molecular dynamics (MD) simulations, two models were built in order to study how the presence of hydrogen at interstitial positions within the nickel lattice affects how it fractures. The first model was a 3D single crystal nickel sample, while the other was the same nickel model but with different concentrations and locations of hydrogen positioned at or near the crack tip. Two aspects of fracture were studied and compared between the different simulations: the crack tip velocity and dislocation nucleation from the crack tip. Analysis of the simulations shows that different concentrations of hydrogen effect both aspects of fracture in nickel, while the size of the region containing hydrogen has no influence whatsoever. The crack growth initially accelerates when there is hydrogen in the system, indicating that the hydrogen enhanced decohesion (HEDE) mechanism is acting. An increase in dislocation nucleation at the crack tip is caused by the action of the hydrogen enhanced localized plasticity (HELP) mechanism.
Citation
Sucre Melfi, A. (2016). Influence of Hydrogen Concentration and Distribution on Fracture in Nickel. Mechanical Engineering Undergraduate Honors Theses Retrieved from https://scholarworks.uark.edu/meeguht/55