Elastic & Plastic Deformation
Elastic & Plastic Deformation
- The important test happens after the force is removed.
- If the object returns to its original shape, the deformation was elastic. If a change remains, the deformation was plastic.
elastic
returns after unloadingplastic
remains changedUse the unloading test
| After the force is removed | Type of deformation | Result |
|---|---|---|
| Returns to the original dimensions | Elastic | No permanent deformation |
| Does not return to the original dimensions | Plastic | Permanent deformation remains |
Definition
1 markWhat is meant by elastic deformation?
Model answer: Deformation that disappears when the deforming force is removed.
Definition
1 markWhat is meant by plastic deformation?
Model answer: Deformation that remains when the deforming force is removed.
The elastic limit is the greatest force, stress or deformation for which the object still returns to its original dimensions after unloading. Beyond this limit, plastic deformation occurs.
Definition
1 markWhat is meant by the elastic limit?
Model answer: The greatest deformation for which the object returns to its original dimensions when the deforming force is removed.
The limit of proportionality concerns the shape of the graph. The elastic limit concerns whether the object returns after unloading. They are different tests and need not occur at exactly the same point.
A wire is loaded, then unloaded. It remains 0.30 mm longer than before. State the type of deformation and what this proves about the elastic limit.
Show worked answer
The deformation is plastic. The wire was taken beyond its elastic limit because it did not return to its original length.