What do 4.8 and 8.8 on the bolt mean

　　What do 4.8 and 8.8 on the bolt mean?From the demand side, standoff More in line with the psychological expectations of consumers, willing to pay for the things they like. https://www.hengkefasteners.com/

　　

　　JINGUBANG

　　

　　The number on the bolt indicates the grade of the bolt. The common grades of the bolt are 4.8, 8.8, 10.9 and 12.9. These numbers are the grades of bolts, which are composed of two parts, representing the tensile strength and yield ratio of bolt materials respectively.

　　

　　Take grade 8.8 bolts as an example, 8.8 can be understood as 8 and 0.8.

　　

　　The first 8 indicates that the tensile strength of the bolt is 800MPa, and 0.8 indicates the yield ratio of the bolt.

　　

　　Yield strength of bolt = tensile strength x yield ratio value

　　

　　Then the yield strength of grade 8.8 bolts =800MPaX0.8=640Mpa.

　　

　　Draw inferences from others

　　

　　The tensile strength of grade 10.9 bolts is 1000Mpa,

　　

　　The yield strength is 1000MpaX0.9=900Mpa.

　　

　　What do yield strength and tensile strength mean?

　　

　　Professional physical explanation after the article comparison, first talk about the popular explanation:

　　

　　Yield strength is the relatively strong force that the bolt can bear when it is pulled to a slight deformation (it will recover after stopping applying force).

　　

　　Tensile strength refers to the cross-sectional area of the bolt that can withstand a relatively large force when the bolt is pulled to deform (it will not recover after stopping applying force, but will break the bolt after continuing to apply force).

　　

　　Thus, the tensile strength of the bolt is always greater than the yield strength of the bolt. The personified metaphor is that if you give in, I’ll let you go, and if you don’t, I’ll break you.

　　

　　Here are some physical terms, you can study them carefully if you are interested.

　　

　　Yield strength is the yield limit of metal materials when they yield, that is, the stress to resist small plastic deformation. For metal materials with obvious yield phenomenon, the stress value that produces 0.2% residual deformation is specified as its yield limit, which is called conditional yield limit or yield strength. Tensile strength, a physical term, is the critical value of metal’s transition from uniform plastic deformation to local concentrated plastic deformation, and it is also the relatively large bearing capacity of metal under static tension. Tensile strength is the resistance to the relatively large uniform plastic deformation of the material. Before the tensile stress, the deformation of the tensile sample is uniform, but after the tensile stress is exceeded, the metal begins to appear necking phenomenon, that is, concentrated deformation occurs; For brittle materials with no (or little) uniform plastic deformation, it reflects the fracture resistance of the material. The symbol is Rm(GB/T 228-1987 old national standard stipulates that the tensile strength symbol is σb), and the unit is MPa.