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For example, the ultimate tensile strength (UTS) of AISI 1018 Steel is 440 MPa. In Imperial units, the unit of stress is given as lbf/in 2 or pounds-force per square inch. This unit is often abbreviated as psi. One thousand psi is abbreviated ksi. A factor of safety is a design criteria that an engineered component or structure must achieve.
The ultimate tensile strength of a material is an intensive property; therefore its value does not depend on the size of the test specimen.However, depending on the material, it may be dependent on other factors, such as the preparation of the specimen, the presence or otherwise of surface defects, and the temperature of the test environment and material.
A statistical analysis of the strength of many samples of a material is performed to calculate the particular material strength of that material. The analysis allows for a rational method of defining the material strength and results in a value less than, for example, 99.99% of the values from samples tested.
[3] 0.2% proof and ultimate tensile strength of the Fe–55Mn–3Al–3Si wt% TWIP steel as a function of the test temperature; strain rate ε=10 −4.s −1. [ 3 ] Austenitic steels are used widely in many applications because of their excellent strength and ductility combined with good wear and corrosion resistance.
As for the tensile strength point, it is the maximal point in engineering stress–strain curve but is not a special point in true stress–strain curve. Because engineering stress is proportional to the force applied along the sample, the criterion for necking formation can be set as δ F = 0. {\displaystyle \delta F=0.}
For example, in 100 countries the ASME BPVCcode stipulates the requirements for design and testing of pressure vessels. [ 4 ] The formula is also common in the pipeline industry to verify that pipe used for gathering, transmission, and distribution lines can safely withstand operating pressures.
Tensile testing, also known as tension testing, [1] is a fundamental materials science and engineering test in which a sample is subjected to a controlled tension until failure. Properties that are directly measured via a tensile test are ultimate tensile strength , breaking strength , maximum elongation and reduction in area. [ 2 ]
According to the classical theories of elastic or plastic structures made from a material with non-random strength (f t), the nominal strength (σ N) of a structure is independent of the structure size (D) when geometrically similar structures are considered. [1] Any deviation from this property is called the size effect.