1. Tensile strength:
When the aluzinc steel coil yields to a certain extent due to the rearrangement of the internal grains, its resistance to deformation increases again. Although the deformation develops rapidly at this time, it can only increase with the increase of stress until the stress reaches the maximum value.
After that, the ability of the aluzinc steel coil to resist deformation is significantly reduced, and large plastic deformation occurs at the weakest point. Here, the section of the specimen shrinks rapidly, and the necking phenomenon occurs until the fracture is broken. The maximum stress value of the aluzinc steel coil before the tensile fracture (b point corresponding value) is called the strength limit or tensile strength.
2. Yield strength:
When the stress exceeds the elastic limit, the deformation increases rapidly. At this time, in addition to elastic deformation, partial plastic deformation also occurs. When the stress reaches point B, the plastic strain increases sharply, and the curve shows a slight plateau fluctuation called yielding.
This stage’s maximum and minimum stresses are called the upper yield point and the lower yield point, respectively. Since the value of the lower yield point is relatively stable, it is used as an indicator of the material resistance, called the yield point or yield strength.
These two strengths are obtained by tensile test, which is to continuously stretch the material with a specified constant loading rate through a tensile testing machine until it breaks or reaches a specified degree of failure, which will cause the material to eventually fail. Force is the ultimate tensile load of the material.
The ultimate tensile load is a force expression, and the unit is Newton (N). Because Newton is a small unit, in most cases, kilonewton (KN) is used more. Because of the different sizes of materials, the ultimate tensile load is difficult to judge strength of the material.
Therefore, dividing the ultimate tensile load by the cross-sectional area of the experimental material, the ultimate tensile load per unit area, the force on a unit area, is an expression of strength, and the unit is Pascal (Pa). Similarly, Pascal is a very small unit, generally expressed in megapascals (MPa).