Bearing materials — selection for heavy loads and low-to-moderate speeds Which material is most suitable for plain bearings subjected to heavy loads (typically at lower speeds), where higher compressive strength is required?

Introduction / Context:
Selecting bearing materials depends on load, speed, lubrication regime, and desired tribological properties. For heavy loads at relatively lower speeds, stronger bronzes are typically favored over very soft bearing metals.

Given Data / Assumptions:

• Plain (journal) bearings under high unit pressure, modest sliding speed.
• Good lubrication is present but boundary conditions may occur at startup.

Concept / Approach:
White metal (babbitt) offers excellent embeddability and conformability for light loads and high speeds but lacks the compressive strength required for heavy loads. Phosphor bronze (Cu–Sn–P) provides higher strength and wear resistance, tolerating heavier pressures with proper lubrication. Variants of aluminium bronze can also handle high loads, but classic exam convention emphasizes phosphor bronze for heavy-duty plain bearings.

Step-by-Step Solution:
Identify service: high load → need higher compressive strength and fatigue resistance.Compare materials: babbitt (soft) vs phosphor bronze (strong, wear-resistant).Select phosphor bronze as the most suitable among the options.

Verification / Alternative check:
Design texts list phosphor bronze for high-load bearings (e.g., rolling mill bushings), while babbitt is used as a thin lining in steel shells for lighter or high-speed conditions.

Why Other Options Are Wrong:

• Babbitt: ideal for light loads/high speeds; too soft for sustained heavy loads.
• Monel metal: corrosion-resistant Ni–Cu alloy, not a standard bearing lining for heavy pressures.
• Silicon bronze and aluminium bronze: can be strong, but phosphor bronze is the standard answer in classical curricula for heavy-load plain bearings.

Common Pitfalls:
Choosing the softest alloy for “safety”; heavy-load bearings need strength and wear resistance more than embeddability.

Final Answer:
phosphor bronze