CLS Tribology & Wear Prevention Techniques 2

Question 1

Which wear mechanism involves the transfer of material from one surface to another due to adhesion at asperity contacts?

Accepted Answer

Adhesive wear

Answer

Adhesive wear occurs when asperities from opposing surfaces weld together and material is torn from one surface and transferred to the other.

Question 2

The Archard wear equation relates wear volume to which primary factors?

Accepted Answer

Load, hardness, and sliding distance

Answer

Archard's equation states that wear volume is proportional to the applied load and sliding distance, and inversely proportional to the hardness of the softer material.

Question 3

What is the primary purpose of an extreme pressure (EP) additive in a lubricant?

Accepted Answer

Form a protective sacrificial layer at metal-to-metal contact zones

Answer

EP additives react chemically with metal surfaces under high contact pressure and temperature to form low-shear-strength films that prevent welding and severe wear.

Question 4

Fretting wear is most likely to occur under which condition?

Accepted Answer

Small-amplitude oscillatory motion between clamped surfaces

Answer

Fretting wear is caused by the micro-motion (typically 1–300 µm amplitude) between surfaces that are nominally clamped together, leading to oxidative debris and surface damage.

Question 5

Which parameter best describes the severity of contact conditions when evaluating lubrication regime selection?

Accepted Answer

Specific film thickness (Lambda ratio, Λ)

Answer

The Lambda ratio (film thickness divided by composite surface roughness) determines whether a contact operates in full-film, mixed, or boundary lubrication regimes.

(CLS) Certified Lubrication Specialist Practice Test

(CLS) Certified Lubrication Specialist Practice Test

CLS Tribology & Wear Prevention Techniques 2