Hardness
Refers to the ability of a material to resist local deformation, especially plastic deformation, indentation or scratches. It is a measure of material softness and hardness.
According to different test methods, hardness is divided into three types.
① Scratch hardness. It is mainly used to compare the softness and hardness of different minerals. The method is to choose a rod with one end hard and one soft end, and the tested material is scratched along the rod, and the hardness of the tested material is determined according to the location of the scratch. Qualitatively speaking, hard objects have long scratches and soft objects have short scratches.
② Press-in hardness. Mainly used for metal materials. The method is to press the specified indenter into the tested material with a certain load, and compare the hardness of the tested material with the size of the local plastic deformation of the material surface. Due to the difference of indenter, load and load duration, there are many kinds of indentation hardness, mainly Brinell hardness, Rockwell hardness, Vickers hardness and micro hardness.
③ Rebound hardness. Mainly used for metal materials, the method is to make a special small hammer fall freely from a certain height to impact the sample of the material to be tested, and how much strain energy is stored (and then released) by the sample during the impact process (through the return of the small hammer) Jump height measurement) to determine the hardness of the material.
The most common Brinell hardness, Rockwell hardness and Vickers hardness of metal materials belong to the indentation hardness. The hardness value indicates the ability of the surface of the material to resist the plastic deformation caused by the intrusion of another object; the rebound method. The hardness is measured, and the hardness value represents the size of the elastic deformation function of the metal.
