Ultimate Strength

Definition - What does Ultimate Strength mean?

Ultimate Strength is the maximum stress that a material can withstand while being stretched or pulled. The ultimate strength of a material is calculated by dividing the cross-section area of the material tested by the stress placed on the material, which is generally expressed in pounds or tons per square inch of material. It is the final amount of stress sustained in a tensile test at the exact moment an object ruptures. Tensile strength is an important measure of a material’s ability to perform in an application, and the measurement is widely used when describing the properties of metals and alloys. Ultimate strength is also known as tensile strength, ultimate tensile strength or the ultimate.

Petropedia explains Ultimate Strength

Ultimate strength is equivalent to the maximum load that can be carried by one square inch of cross-sectional area when the load is applied as simple tension.

The ultimate strength is the maximum engineering stress in a uniaxial stress-strain test. It can differ, depending on the type of material:

  • For non-deformable materials, it is the nominal stress at which a round bar of the material, loaded in tension separates.
  • For deformable materials, it occurs at the onset of necking at strains preceding breakage (separation).
  • For brittle solids such as ceramics, glasses, and brittle polymers, it is the same as the failure strength in tension.
  • For metals and most composites, it is larger than the yield strength by a factor of between 1.1 and 5 because of work hardening or, in the case of composites, load transfer to the reinforcement.

The ultimate strength is not used in the design of ductile static materials because design practices dictate the use of the yield stress. It is, however, used for quality control, because of the ease of testing. It is a common engineering parameter when designing brittle materials, because there is no yield point.

The ultimate strength is usually found by performing a tensile test and recording the engineering stress versus strain curve. The highest point of the stress-strain curve is the UTS. It is an intensive property; therefore its value does not depend on the size of the test specimen. However, it is dependent on other factors, such as:

  • Preparation of the specimen
  • Presence of surface defects
  • Temperature of the test environment and the material

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