Ryder Bolin

Date of Graduation

2018

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Mechanical and Aerospace Engineering

Committee Chair

Stefanos Papanikolaou

Committee Co-Chair

Kostas Sierros

Committee Member

Akkerman Vyacheslav

Abstract

The present thesis showcases the investigation of nanoindentation at ultra-low depths (<500nm), for the study of the origin and initiation of crystal plasticity in a number of Face Centered Cubic (FCC) metals: Nickel (Ni), Copper (Cu), and Aluminum (Al) in single crystalline or polycrystalline form. Nanoindentation was carried out using a Berkovich tip, and indentations were carried out in the nano-regime of polycrystalline FCC metals and single crystalline Cu and Al. Two custom-built four-point bending apparatuses were used to apply in-plane tension on all samples during indentation. Samples were indented using both displacement and load controls, in order to both carefully estimate the hardness and plasticity noise as a function of depth and applied in-plane tension. The noisy character of crystal plasticity manifests itself through nanoindentation pop-in events, which are abrupt and stochastic plastic displacements during the initial stage of plasticity. I discuss and demonstrate indentation size effects induced and/or promoted by the in-plane stress in FCC materials. The hardness analysis shows a statistically inverse dependence on in-plane stress for small depth indentation and I discuss the consistency of the effects in both the hardness and pop-in events among the various FCC crystals studied. Finally, I discuss a novel approach to detect the onset of pop-in noise in a realistic sample without special treatment and demonstrate its consistency for Cu single crystalline samples.

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