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Gears: factor governing surface endurance (pitting) strength. Identify the material property that most directly influences the surface endurance limit in contact (Hertzian) stress for gears. Choose the correct option.

Difficulty: Easy

Elastic strength
Yield strength
Brinell hardness number (BHN)
Toughness

Correct Answer: Brinell hardness number (BHN)

Explanation:

Concept
Surface endurance (pitting resistance) under Hertzian contact correlates strongly with surface hardness. Brinell hardness number (or similar hardness scales) is used in gear contact stress formulas (e.g., via allowable contact stress).

Why BHN
Higher hardness generally raises the allowable contact stress and delay pitting compared to yield/toughness alone.

Final Answer
Brinell hardness number (BHN)

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