Learning topic
Basic Modes of Deformation
Overview of tension, compression, shear, torsion, bending, and combined loading of structural members.
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| Classification | Type | Description |
|---|---|---|
| By recovery after unloading | Elastic | Disappears after the load is removed; within the adopted model, the body recovers its original shape and dimensions. |
| Plastic | Does not disappear completely after unloading; a permanent component of deformation remains. | |
| By loading and deformation of a structural member | Tension | Axial forces elongate the member. |
| Compression | Axial forces shorten the member. | |
| Shear | Adjacent layers tend to slide relative to one another, changing the angles between material directions. | |
| Torsion | Cross-sections rotate relative to one another about the longitudinal axis. | |
| Bending | The longitudinal axis becomes curved; in a typical beam model, cross-sections rotate and deflections develop. |
In real structures, several deformation modes may occur simultaneously. Such cases are treated as combined loading.
Simple and combined cases
Tension, compression, shear, torsion, and bending provide fundamental models for engineering analysis. In a real member, several internal force resultants may act simultaneously; this is treated as combined loading.
Why distinguish deformation modes?
Each mode has characteristic internal force resultants, stress distributions, and deformation equations. Correctly recognizing how a member works is therefore a first step in choosing an appropriate calculation model.