Yield Stress of a Material – Simple Explanation
Yield of a material is explained as the stress at which a material begins to deform irreversibly. Preceding the yield point, the material will deform elastically, meaning that it will return to its original shape when the applied stress is removed (i.e. no permanent, visible change in the shape of the material).
Once the yield point is passed, however, some of the deformation will be permanent and non-reversible. Knowledge of the yield point is important when designing a component since it normally signifies an upper limit to the load that can be applied.
Not all materials have a well-defined yield region. In the absence of a distinct yield point, a .2% offset is used to obtain an approximate yield point. All deformation before the yield point is uniform throughout the narrow region of the material.