Quick
Ultimate strength is the maximum allowable stress before failure. May also be referred to as ultimate stress. The ultimate stress is dependent upon the type of material. In machine design, ultimate stress is abbreviated by Su. There are also different types of ultimate stress, such as ultimate compressive strength (Suc), ultimate tensile strength (Sut). The ultimate compressive strength or the ultimate tensile strength may be referred to simply as the ultimate strength.
Equation
The ultimate strength, also called ultimate normal stress, is the ultimate load divided by the cross sectional area of the material sample:
Details
An element important to the designer is how a selected material will behave under a certain application of load. This can be examined by conducting a tensile test on material samples.
For brittle materials, the force which breaks the load is equal to the ultimate load, and can be denoted PU.
For a long time engineers used the term ultimate strength. However, in material science and metallurgy the term tensile strength is commonly used.