Definition - What does Yield Strength mean?
Yield strength refers to an indication of maximum stress that can be developed in a material without causing plastic deformation. It is the stress at which a material exhibits a specified permanent deformation and is a practical approximation of the elastic limit.
In engineering structural design, yield strength is very important. For example, when designing a component, it must support the force incurred during use, and the component must not deform plastically. Therefore, a material with sufficient yield strength should be selected.
In design applications, the yield strength is often used as an upper limit for the allowable stress that can be applied. It is especially important in material applications that require precise dimensional tolerances to be maintained in the presence of high stresses and loads. By altering dislocation density, impurity levels and grain size (in crystalline materials), the yield strength of the material can be fine tuned. For materials without a clear distinct yield point, yield strength is usually stated as the stress at which a permanent deformation of 0.2% of the original dimension will result, known as the 0.2% yield stress.
Corrosionpedia explains Yield Strength
Yield strength can be explained, in engineering and materials science, as the stress at which a material begins to plastically deform. Prior to the yield point, the material will deform elastically and will return to its original shape when the applied stress is removed. Once the yield point is passed, some fraction of the deformation will be permanent and non-reversible.
Knowledge of the yield strength is very important when designing components, since it usually represents the upper limit of the load that can be applied. Yield strength is very important for controlling many materials' production techniques, such as forging, rolling or pressing.
The value of yield strength is important in the construction of structures, such that the structures are able to perform in the elastic region under normal servicing conditions. However, when faced with unexpected impact loads such as explosions, fires or natural disasters such as earthquakes, etc., the plastic region of the material becomes crucial, as a large portion of the energy being absorbed by the materials under such circumstances is mainly contributed by the plastic region. As such, having a higher toughness implies that the materials are able to withstand such unforeseen loading for a longer period of time so as to allow more time for safety measures to be carried out.
In general, the yield strength increases with strain rate and decreases with temperature. When the latter is not the case, the material is said to exhibit yield strength anomaly, which is typical for super-alloys and leads to their use in applications requiring high strength at high temperatures. The yield strength anomaly is also referred to as the "yield stress anomaly."