12) Surface Text. Intro

Question 1

What does surface texture affect?

Answer 1

Fatigue resistance
Bearing properties
Wear resistance

Question 2

How can surface texture affect fatigue life?

Answer 2

Imperfections in a surface are often the starting point of failure due to fatigue.

Question 3

Describe the ideal surface for bearings, and why a perfect surface is not desirable.

Answer 3

For bearings - the surface should have valleys to trap lubricant.

A perfect surface would cause surface bonding and contact between the bearing surfaces - undesirable.

Question 4

What affect does surface texture have on wear/adhesion?

Answer 4

The larger the area of contact, the lower the wear rate is per unit area. If there are imperfections, the wear will be focussed on a smaller area, wearing it quicker.

Question 5

What are the 3 categories of form types?

Answer 5

Roughness (small) - irregularities in surface texture, from cutting tool.

Waviness (medium) - mainly due to machine vibration and deflections under cutting force.

Errors of form (large) - departure from geometrical shape.

Question 6

Describe the 3 GD&T symbols for surface texture.

Answer 6

Basic - plain tick, the surface under consideration

Tick with horizontal line - “A machined surface”

Tick with circle - A surface where material removal is prohibited.