Lecture 4a - Surface and Tribology

Lecture 4a - Surface and Tribology - Surface Surface...

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Surface Characteristics and Tribology Lecture 4.a ISE 2204 – Introduction to Manufacturing Processes Dr. Jaime Camelio February 9 th , 2010 Surface Properties Surface Structure Surface Roughness Tribology Friction Wear Lubrication Surface Treatment ISE 2204 – Introduction to Manufacturing Processes – Spring 2010 Outline
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Although bulk material determines the overall mechanical properties, the surface affects: Friction and wear Effectiveness of lubricants Appearance Fatigue crack initiation Corrosion The manufacturing process determines many surface properties ISE 2204 – Introduction to Manufacturing Processes – Spring 2010 Surface Properties Schematic illustration of the cross-section of the surface structure of metals. The thickness of the individual layers depends on processing conditions and the environment ISE 2204 – Introduction to Manufacturing Processes – Spring 2010 conditions and the environment. Source : After E. Rabinowicz and B. Bhushan . Surface Structure
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Metal substrate Bulk material properties depend on composition and processing. Work hardened layer Deformed during processing -- may have recrystallized Beilby or amorphous layer Region that melted and then rapidly solidified -- not always present Oxide layer Can be protective or non protective -- affects friction and wear Adsorbed gas Contaminants ISE 2204 – Introduction to Manufacturing Processes – Spring 2010 Surface Structure Flaws Random irregularities such as cracks, depressions, etc. Lay Direction of the predominant surface pattern Waviness Long wavelength deviations Waviness width Waviness height Roughness Short wavelength deviations superimposed on the waviness ISE 2204 – Introduction to Manufacturing Processes – Spring 2010 Surface Texture and Roughness
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ISE 2204 – Introduction to Manufacturing Processes – Spring 2010 Surface Texture Standard terminology and symbols used to describe surface finish. The quantities are given in μ in. Common surface-lay symbols. ISE 2204 – Introduction to Manufacturing Processes – Spring 2010 Surface Texture
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AA (arithmetic average) or CLA (center line average) roughness, R a (y a are absolute values) Root mean square roughness, Rq Rq gives more weight to large deviations 1 2 2 0 1 l ydx l ISE 2204 – Introduction to Manufacturing Processes – Spring 2010 Surface Roughness Methods Example Calculate the ratio of Ra/Rq for a saw-tooth profile.
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Lecture 4a - Surface and Tribology - Surface Surface...

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