Which term describes permanent deformation that occurs after overload?

• A. Elastic deformation
• B. Creep
• C. Plastic deformation
• D. Yielding deformation

Answer: (C)

When a material is loaded beyond its elastic limit, it enters the plastic region where the crystal structure yields and dislocations move, causing irreversible shape change. The deformation that remains after removing the load is plastic deformation. Elastic deformation is reversible and disappears when the load is removed. Creep is slow, time-dependent deformation under a sustained load, usually at elevated temperature, not the immediate aftermath of overload. Yielding describes the onset of plastic flow, not the permanent deformation itself. So the term that best describes permanent deformation after overload is plastic deformation.