Learning topic

Strain Hardening and Reloading

How prior plastic deformation affects subsequent loading: strain hardening, residual strain, elastic unloading, and changes in ductility.

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This topic explains how previous plastic deformation changes subsequent material response. It covers strain hardening, strengthening, residual deformation, elastic unloading, reduced remaining ductility, and why loading history matters when evaluating the mechanical behavior of a component.

After plastic deformation, a material may have different mechanical characteristics than it had initially. Therefore, subsequent loading may depend on the material's deformation history.

Strain hardening

During cold plastic deformation, many metals exhibit strain hardening: resistance to further plastic flow increases. At the same time, the remaining ductility usually decreases.

Unloading

During unloading, the elastic part of the deformation largely disappears, while the plastic part remains. The specimen therefore does not return completely to its original dimensions.

Reloading

On reloading, the response depends on the previous plastic deformation, loading direction, material, and thermal history. In elementary models, reloading after strain hardening illustrates how the stress level required for further plastic deformation can change.

Engineering significance

Strain hardening is deliberately used in cold-working processes, but it must also be considered when ductility and the ability of a component to tolerate subsequent overloads are important.