Dominant breakage mechanism in a hammer crusher\nThe predominant mechanism responsible for size reduction in a hammer crusher is:

Introduction / Context:
Correctly identifying the dominant breakage mechanism of a machine helps predict product shape, fines generation, and wear patterns. Hammer crushers (mills) use pivoting or fixed hammers on a rotor to deliver repeated blows to feed particles inside a chamber lined with breaker plates and screens.

Given Data / Assumptions:

• Conventional hammer crusher geometry with hammers and breaker plates.
• Hardness within typical operating range (no extreme ductility).

Concept / Approach:
The high tip speed of the hammers delivers impact energy to the particles, causing fracture by dynamic stress well above the material’s strength. Secondary mechanisms (some attrition as fragments rub and are sheared along breaker plates; limited compression between particles) do occur, but the dominant energy input is impact. This is why rotor speed and hammer design heavily influence PSD and fines generation in these machines.

Step-by-Step Solution:

Verification / Alternative check:
Manufacturer literature classifies hammer crushers under impact crushers (with cage mills and impactors), distinct from compression (jaw/roll) and attrition (disc/colloid) devices.

Why Other Options Are Wrong:

• Attrition is present but secondary.
• Compression is minimal in free-flight impact chambers.

Common Pitfalls:
Confusing hammermills with attrition mills due to presence of breaker plates; the kinetic energy transfer indicates impact dominance.

Final Answer:
Impact (high-velocity blows)