Yield stress and working stress are concepts used in the field of materials engineering and structural mechanics. They refer to different points of stress in materials and structures and have distinct implications.
- Yield Stress: Yield stress is a material property that represents the stress at which a material begins to deform plastically, i.e., it undergoes permanent or non-reversible deformation. In simpler terms, it's the stress at which a material transitions from elastic behavior (where deformation is temporary and fully reversible) to plastic behavior (where deformation becomes permanent).
When a material is subjected to stress below its yield stress, it will return to its original shape once the load is removed. However, when the stress reaches or exceeds the yield stress, the material will start to undergo plastic deformation, leading to permanent changes in its shape.
- Working Stress: Working stress, also known as allowable stress or design stress, is the maximum stress that a material or structure is allowed to bear under normal working conditions. It is determined by applying a safety factor to the yield stress of the material. The safety factor accounts for uncertainties in material properties, loads, and other factors to ensure the structure's reliability and safety.
The working stress is used in the design of structures to ensure that they can withstand expected loads without experiencing failure. By applying a safety factor, engineers aim to prevent stress levels from reaching the yield stress, as operating a material or structure close to its yield point could lead to excessive deformation or failure.
In summary, the main difference between yield stress and working stress is as follows:
- Yield Stress: Represents the stress at which a material undergoes permanent deformation and transitions from elastic to plastic behavior.
- Working Stress: Represents the maximum allowable stress for a material or structure under normal working conditions, with a safety factor applied to the yield stress to ensure structural safety.
It's important for engineers and designers to consider both yield stress and working stress to ensure the integrity and safety of structures and materials used in various applications.