Date of Graduation

5-2012

Document Type

Thesis

Degree Name

Bachelor of Science in Mechanical Engineering

Degree Level

Undergraduate

Department

Mechanical Engineering

Advisor/Mentor

Zou, Min

Committee Member/Reader

Stewart, John

Committee Member/Third Reader

Stewart, Gay

Abstract

Friction is one of the most common and influential mechanical interactions of two structures on both the macroscopic scale and especially the microscopic scale. On the microscopic scale, friction becomes the prime component of mechanical forces exerted on devices. Frictional anisotropy is an interesting characteristic of certain materials and can be used to control frictional properties in various applications. In this study, we measured the anisotropic frictional behavior of two silver (Ag) thin films: a continuous film and a thin film consisting of tilted nanorods angled at an average angle of 70o to the surface normal. Scratches, eight microns in length, were performed on the films with normal loads ranging from 50 µN to 8,000 µN using a conical tip with a 100 micron tip radius. The coefficient of friction (COF) of the tilted nanorods was measured for scratches performed along, against, and perpendicular to the tilt direction. In addition, the deformation of the individual scratches was visually characterized with a scanning electron microscope (SEM). The tilted nanorods demonstrated significant frictional anisotropy with the COF of scratches performed against the tilt direction being over 30 percent lower than those performed along the tilt direction. Furthermore, for normal loads up to 2000 µN, the tilted nanorod sample displayed a lower COF than the thin film for scratches performed against the tilt direction. Visual deformation analysis showed a large increase in damage as the normal load was systematically raised from 50 µN to 8000 µN. In addition, the deformations of the nanorods are shown to be dependent on the direction of the scratch.

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