Reversibility defines elastic vs. plastic deformation

Steps:

• Define elastic deformation as reversible shape change under stress, per Hooke's law.
• Define plastic deformation as permanent shape change exceeding yield point.
• Compare options to these definitions for accuracy.
• Identify D as matching the core distinction.

Why D is correct:

• Elastic deformation reverses upon stress removal (Hooke's law: σ = Eε, recoverable strain), while plastic deformation involves irreversible dislocation motion, leaving permanent strain.

Why the others are wrong:

• A: Only elastic deformation is proportional to force (Hooke's law); plastic follows nonlinear stress-strain curve.
• B: Plastic deformation can cause volume changes via void formation or phase shifts, unlike mostly isochoric elastic.
• C: Plastic deformation generates more heat from dislocation interactions; elastic causes minimal heating.

Final answer: D