Topic 4_Tutorial Roughness, Hardness, and Friction

Question 1

What are the key points about roughness

Answer 1

• Many different way to measure (different ways to average e.g. Ra)
• influence wear mechanisms, rougher more wear
• Important for contact stresses (average contact stress lower, maximum higher)
• Important for lubricant (surface texture

Question 2

Why is Ra not perfect

Answer 2

Cant tell the difference between peaks on surface and wavy surface

Question 3

Hardness key points

Answer 3

• Generally hardness and wear can be related
• Secondary material property (dependent on ductility, elasticity, toughness)
• Convert from Hv to SI units (Hv *9.81)

Question 4

Friction key points

Answer 4

• Three main mechanisms (adhesion, deformation, hysterysis)
• Independent of wear (high friction higher wear and low friction higher wear)
• Bananas arent that slippy
• Bowedn and Tabor Theory

Question 5

Whats the issue with models of friction

Answer 5

None are accurate and very complicated