Contents
① Tensile Strength
It is the maximum stress that the sheet metal material is subjected to before pulling out.
The unit is: N/mm2 or MPa, symbol is σb.
It is one of the index of metal strength.
② Bending Strength
It is the maximum stress that the cross section is subjected to when the load is applied between the two points of the specimen.
The unit is: N/mm2 or MPa, symbol is σbb.
It is one of the index of metal strength.
③ Compressive Strength
It is the maximum stress that the sheet metal material can withstand under pressure without breaking.
The units are: N/mm2 or MPa, symbol is σbc.
④ Yield Strength
It refers to the stress of the metal sample during the stretching process, when the load no longer increases and the sample continues to deform.
The unit is: N/mm2 or MPa symbol is σs.
The yield strength is the pressure value of the yield point.
For the material that is not obvious yield, the stress value that produces 0.2% permanent deformation is often referred to as the yield strength.
⑤ Shear Strength
It refers to the maximum load of the original cross sectional area of the shear area before the sample shears.
The unit is: N/mm2 or MPa and symbol is στ.
⑥ Elastic Limit
It refers to the maximum stress of the specimen under the condition that the test piece deform after the external force disappears and can recover the original condition.
The unit is: N/mm2 or MPa and symbol is σe.
⑦ Fracture Surface Shrinking Percentage
It is the percentage of the original cross-sectional area that is shrunk after tensile load. The symbol is ψ and it is one of the plastic index of materials.
⑧ Elongation Ratio
Refers to the percentage of the elongation of the sample material and the original length after the sample material is breaking. Elongation is also one of the plastic pointers of materials and symbol is δ.
⑨ Hardness
It refers to the ability of the material to resist hard pressing into its surface.
There are three types of hardness: brinell hardness, rockwell hardness and vickers hardness.
Generally the hardness of steel increases with the increase of carbon content in steel.
⑩ Brinell Hardness（HB）
One of the representation method of hardness and its measurement method is:
press the steel ball after quenching into the material surface and keep a period of time under specified load, then calculate the ratio of pressure load and area of indentation.
The ratio is the brinell hardness.
⑪ Rockwell Hardness （HR）
One of the representation method of hardness and its measurement method is:
Press the diamond cone or steel ball after quenching into the sample material surface, then measure the material’s hardness according to the depth of the indentation.
The Rockwell Hardness can be divided into HRA, HRB, HRC based on different test items and pressure.
HRA：
The hardness was obtained by applying 1470N pressure at a diamond head with a cone angle of 120 degrees on the test samples. Suitable for measuring surface quenching layer, carburizing layer and hard alloy material.
HRB：
It is the hardness value obtained by applying 980N pressure to the steel ball with a diameter of 1.59mm. It is suitable for measuring soft metals such as nonferrous metals, annealing, and normalizing steel.
HRC：
The hardness was obtained by applying 588N pressure at the diamond cone with 120° vertex angle for testing samples.
It is suitable for measuring hard metal such as tempered steel and hardened steel.
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