Introduction
When a specimen of material is loaded in such a way that it extends it is said to be in tension. On the other hand if the material compresses and shortens it is said to be in compression.
On an atomic level, the molecules or atoms are forced apart when in tension whereas in compression they are forced together. Since atoms in solids always try to find an equilibrium position, and distance between other atoms, forces arise throughout the entire material which oppose both tension or compression.
The phenomena prevailing on an atomic level are therefore similar. On a macroscopic scale, these aspects are also reflected in the fact that the properties of most common materials in tension and compression are quite similar.
The major difference between the two types of loading is the strain which would have opposite signs for tension (positive—it gets longer) and compression (negative—it gets shorter).
Another major difference is tension tends to pull small sideways deflections back into alignment, while compression tends to amplify such deflection into buckling.
Read more about this topic: Compressive Strength
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