Mechanical behavior

Mechanical properties refer to the properties exhibited by metallic materials under external forces.

1. Strength: The ability of a material to resist deformation and fracture under external force (load). The unit area of ​​the material is stressed by the load.

2, yield point (бs (: called yield strength, refers to the material in the process of pulling, when the stress of the material reaches a certain critical value, the load no longer increases the deformation but continues to increase or generate 0.2% L stress value, the unit uses Newton/mm 2 (N/mm2 (represented.

3, tensile strength (бb (also called the strength limit refers to the material to withstand the maximum stress value before breaking). Units used Newton / mm 2 (N / mm2 (represented.

4. Elongation (δ(: the percentage of the total elongation to the length of the original gauge length after the tensile fracture of the material).

5, the reduction rate of the section (Ψ (after the tensile fracture of the material, the maximum reduction area of ​​the section and the percentage of the original area).

6. Hardness: refers to the ability of the material to resist the surface of other harder pressures. The commonly used hardness is measured by the range of hardness (HBS, HBW (and Rockwell hardness (HKA, HKB, HRC (.

7, impact toughness (Ak (: material resistance to impact load, the unit is Joule / cm 2 (J / cm2 (.

Tensile stress and stage

1. Elasticity: εe=σe/E, index σe, E

2. Rigidity: △L=P·l/E·F Ability to resist elastic deformation

3, strength: σs---yield strength, σb---tensile strength

4, toughness: impact absorption work Ak

5, fatigue strength: alternating load σ-1 < σs

6, hardness HR, HV, HB

a, I stage: the linear elastic phase, the initial stress, the stress-strain curve is a straight line, and the maximum stress at this stage is called the proportional limit σe of the material.

b, II stage: in the yield stage, when the stress increases to a certain value, the stress-strain curve appears horizontal line segment (with slight fluctuations (in this stage, the stress is almost constant, but the deformation increases sharply, and the material loses resistance to deformation) Ability, this phenomenon is called yield, the corresponding stress is called yield stress or yield limit, and is expressed by σs.

Stages c and III: In the strengthening stage, after yielding, the material enhances the ability to resist deformation. The stress corresponding to the highest point of the strengthening phase is called the strength limit of the material. Expressed by σb, the strength limit is the maximum stress that the material can withstand.

d, IV stage: for the necking stage, when the stress increases to the maximum value σb, a certain part of the test piece shrinks significantly, and finally breaks at the neck.

The low carbon steel σs and σb are the main indicators to measure their strength. Rigidity: △L=P·l/E·F, the ability to resist elastic deformation. P---tension, l---material original length, E---elastic modulus, F---section area.