Q_Goest said:Hi araan.
Allowable stress is a term used to indicate the maximum amount of stress a material may be subjected to given a predetermined factor of safety. In mechanical engineering, we use allowable stress in piping and pressure vessel analysis. I believe civil engineering uses this concept for other purposes as well, including reinforced concrete structures.
Regardless of its use, the calculation of stress can be done using any method suitable, such as conventional hand calculations, using Roark, ASME code calculations, FEA, etc... The stress obtained from those calculations must then be compared to the maximum stress the material is allowed to be exposed to (ie: the allowable stress). For piping codes for example, the stress determined by calculation may not exceed 2/3 of yield strength or about 1/4 of ultimate tensile strength, depending on the code.
The allowable stress is the maximum amount of stress that a material can withstand without causing permanent deformation or failure. It is typically expressed in units of force per unit area (e.g. pounds per square inch or megapascals).
Allowable stress is calculated by dividing the maximum load or force that a material can withstand by its cross-sectional area. This calculation takes into account factors such as the material's strength, its shape, and the conditions under which it will be used.
Calculating allowable stress is important because it helps determine the safety and reliability of a structure or component. By ensuring that the stress on a material does not exceed its allowable limit, the risk of failure or collapse can be minimized.
Some factors that can affect allowable stress include the type and quality of the material, the shape and size of the component, the temperature and environmental conditions, and the loading conditions (e.g. tension, compression, bending).
Allowable stress is the maximum stress that a material can withstand without permanent deformation or failure, while ultimate stress is the maximum stress that a material can withstand before breaking. Yield stress is the stress at which a material begins to deform plastically. These values are typically different and are used for different purposes in engineering calculations.