The yield point is defined as the transition from elastic to ...

• A. The switch from elastic to plastic deformation
• B. The point of fracture
• C. The onset of creep
• D. The maximum stress

Answer: (B)

The yield point marks the boundary where deformation changes from elastic to plastic. Up to this point, applying stress causes reversible, recoverable shape change; once you exceed yield, dislocations move and permanent, irreversible plastic deformation begins. The idea is to identify when the material stops springing back after removing the load.

Why the other ideas don’t fit: fracture is the failure of the material after extensive deformation, not the onset of permanent deformation. creep is time-dependent deformation under a constant load, usually at elevated temperatures, not the immediate elastic-to-plastic transition. maximum stress refers to the ultimate tensile strength, the highest stress the material can withstand before failure, which occurs after yielding and necking, not at the start of plastic deformation.