Jaw crusher mechanics: which size-reduction mechanism dominates in jaw crushers handling brittle ores and rocks?

Introduction / Context:
Crushers reduce solid size via mechanical forces. Understanding the dominant mechanism helps select equipment and predict product size distribution and wear.

Given Data / Assumptions:

• Jaw crusher with fixed and moving jaws forming a V-shaped chamber.
• Typical duty: primary crushing of brittle, hard materials.

Concept / Approach:
Jaw crushers primarily apply compressive force. The moving jaw presses the feed against the fixed jaw; the nip compresses and fractures particles along weaknesses. Secondary mechanisms like abrasion occur, but compression dominates the breakage.

Step-by-Step Solution:
Observe machine kinematics: oscillating jaw closes the gap.Resulting stress state in particles: predominantly compressive.Therefore, the primary size-reduction mechanism is compression.

Verification / Alternative check:
Manufacturer literature classifies jaw, gyratory, and roll crushers as compression machines; hammer mills and impactors are impact devices; attrition is typical in mills.

Why Other Options Are Wrong:
Attrition and cutting dominate in mills or knives, not in jaws.Impact is characteristic of hammer/impact crushers.

Common Pitfalls:
Assuming that because particles bounce or slide, attrition or impact is dominant; in jaw crushers, these are minor compared to compression.

Final Answer:
compression