Which bolt-related term is defined as the maximum load a bolt can withstand without acquiring a permanent set?

• A. Joints
• B. Yield Strength
• C. Proof Load
• D. Shear Strength

Answer: (C)

In bolt practice, the key idea is the limit at which a fastener remains elastic and doesn’t deform permanently. The term for that maximum load is the proof load. It represents the highest load a bolt can carry and still return to its original length after unloading, satisfying a standard test requirement. Yield strength, by contrast, is the material’s property that marks when permanent deformation begins, but it’s a property, not a specified test limit for a given bolt. Shear strength concerns resistance to shear failure, not the axial elastic limit, and joints describe the assembled system rather than a load limit. So the concept described—maximum load before permanent set—maps to proof load.