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As we know that metals have elastic property, this elastic behavior reaches a limit at a level of stress called elastic limit. The term Elastic limit is more a definition than an exact indicator of the stress level that indicates the limit. The stress level of course varies for each metal, it is structure sensitive, and also depends on the rate at which the metal is strained.

Elastic Limit is the upper bound of the stress where when the stress is released the metal will return to its original dimensions. On the other side of this limit, a permanent deformation in the metal would result.

The Figure 2.1 above shows the typical stress and strain diagram. The stress σ is plotted on the Y axis and the resulting strain ϵ is plotted on the X axis.

As the metal under test is stressed, the strain on the X axis increases. To a point this increase is proportional to the increasing stress, up to this point the load is proportionally balanced by the strain, if the stress is removed at or below this point the metal will show no permanent stress - damage. Further loading deviates from the proportionality however the metal remains elastic to the point where elastic stain is reached, this means that further from this point the metal is not elastic, and it will not revert back to its original form or shape – a permanent damage has taken place. The stress below this limit allows the metal to revert back to its original shape and size if the stress is removed. This is the point where the limit of metal’s elasticity is reached.