1. Tensile strength (σb): The maximum force (Fb) that the sample bears when it breaks during the tensile process, divided by the original cross-sectional area (So) of the sample, and the stress (σ) is called Tensile strength (σb), the unit is N/mm2 (MPa). It represents the maximum ability of metal materials to resist damage under tensile force. In the formula: Fb-the maximum force that the sample bears when it is broken, N (Newton); So-the original cross-sectional area of the sample, mm2.
2. Yield point (σs): For a metal material with a yield phenomenon, the stress at which the specimen can continue to elong without increasing the force during the stretching process is called the yield point. If the force drops, the upper and lower yield points should be distinguished. The unit of yield point is N/mm2 (MPa). Upper yield point (σsu): the maximum stress before the specimen yields and the force drops for the first time; Lower yield point (σsl): the minimum stress in the yield stage when the initial transient effect is not taken into account. Where: Fs--yield force (constant) during the tensile process of the sample, N (Newton) So--the original cross-sectional area of the sample, mm2.
3. Elongation after breaking: (σ) In the tensile test, the percentage of the length of the gauge length increased by the sample after breaking to the original gauge length is called the elongation. Expressed by σ, the unit is %. In the formula: L1-the gauge length of the sample after breaking, mm; L0-the original gauge length of the sample, mm.
4. Reduction of area: (ψ) In a tensile test, the percentage of the maximum reduction of the cross-sectional area at the reduced diameter of the sample after it is broken to the original cross-sectional area is called the reduction of area. Expressed in ψ, the unit is %. In the formula: S0-the original cross-sectional area of the sample, mm2; S1-the minimum cross-sectional area at the reduced diameter after the sample is broken, mm2.
5. Hardness index: The ability of metal materials to resist the indentation of hard objects is called hardness. According to different test methods and scope of application, hardness can be divided into Brinell hardness, Rockwell hardness, Vickers hardness, Shore hardness, micro hardness and high temperature hardness. There are three commonly used pipes: Brinell, Rockwell and Vickers hardness.
Brinell hardness (HB): Use a steel ball or cemented carbide ball with a certain diameter to press it into the surface of the sample with the specified test force (F), remove the test force after the specified holding time, and measure the indentation diameter (L). The Brinell hardness value is the quotient obtained by dividing the test force by the indentation spherical surface area. Expressed in HBS (steel ball), the unit is N/mm2 (MPa).
