The color coated base plate is galvanized steel plate. The common mechanical properties of the material are tensile, impact and hardness. For different purposes, the items required to be tested are different. Generally, the color coated steel plate for
building envelope is only used for tensile test, and the tested items include tensile strength, yield strength and elongation.
When the stress exceeds the elastic limit, the deformation increases rapidly. At this time, in addition to the elastic deformation, some plastic deformation also occurs.
When the stress reaches the yield point, the plastic strain
increases sharply, and a small fluctuating platform appears in the curve, which is called yield. The maximum and minimum stresses in this stage are called the upper yield point (Reh) and the lower yield point (REL), respectively.
Because the value
of the lower yield point is relatively stable, it is called yield point or yield strength as the index of material resistance.
The tensile strength (RM or TS) is also called the strength limit, which refers to the maximum
stress value that the material bears before breaking.
When the substrate yield to a certain extent, due to the rearrangement of internal grains, its resistance to deformation is improved again. At this time, although the deformation develops rapidly,
it can only increase with the increase of stress until the stress reaches the maximum value.
After that, the ability of the base plate to resist deformation is obviously reduced, and a large plastic deformation occurs at the weakest place, where the cross section of the test piece is rapidly reduced, necking phenomenon appears, until the
The maximum stress value of the substrate before tensile fracture is called the strength limit or tensile strength. Its testing requirements and methods are consistent with the yield strength. In fact, the yield strength and tensile
strength are detected on the tensile curve at the same time.
Percentage of the total elongation of the substrate material to the original gauge length after tensile fracture.
The main principle of Rockwell hardness and surface Rockwell hardness test is to first press the indenter to the surface of the sample with the initial test force, and then press the indenter to the surface of the sample with the total test force.
After the specified holding time, remove the main test force, and calculate the hardness value with the measured residual indentation depth increment.
It is suitable for the measurement of Rockwell hardness and surface Rockwell hardness of cold-rolled
sheet, hot-dip galvanized sheet, electroplated tin sheet. According to the thickness of steel plate, generally speaking, the surface hardness of steel plate is measured, while the Rockwell hardness of relatively thick steel plate is measured.