**H**ow is the yield point of the seamless square tube calculated?

**T**he metal material with yielding phenomenon, the force of the sample does not increase (maintains constant) during the stretching process, and the stress at the time of elongation can be continued, which is called the yield point. If the force drops, the upper and lower yield points should be distinguished. The unit of yield point is N/mm2 (MPa).

**Y**ield point on the square tube (σsu): the maximum stress before the sample yields and the force drops for the first time;

**Y**ield point under the square tube (σsl): The minimum stress in the yielding stage when the initial transient effect is not counted.

**T**he calculation formula for the yield point is:

**W**here: Fs--the yield force (constant) during the tensile process of the specimen, N (Newton);

**S**o--the original cross-sectional area of the sample, mm2.