Rolling, peening, rippling, and which process are all examples of plastic flow?

• A. Elastic Rebound
• B. Plastic Flow
• C. Brittle Fracture
• D. Creep

Answer: (B)

Plastic flow is permanent deformation that remains after the applied stress is removed, caused by dislocations moving in the metal when the yield strength is exceeded. Rolling, peening, and rippling all produce this kind of lasting shape change.

In rolling, the workpiece is forced between rollers, causing the material to yield and flow plastically as its thickness and dimensions change. In peening, many small impacts plastically deform the surface layer, leaving permanent changes and often introducing beneficial residual compressive stresses. Rippling results from plastic flow in the surface layers that creates lasting wave-like patterns.

Elastic rebound would mean the material springs back when the load is removed, which isn’t the case here. Brittle fracture involves cracking with little to no plastic deformation, so it isn’t about plastic flow. Creep is also a form of plastic deformation, but it is time-dependent and typically occurs under sustained load at elevated temperatures, whereas these processes are rapid, forming or altering geometry through immediate plastic flow.