Tensile machine, tensile testing machine, universal material testing machine yield strength refers to the material tensile stress-strain curve
Is the critical stress value of the material yield.
(1) For materials with obvious yield phenomenon, the yield strength is the stress at the yield point (yield value);(2) For materials whose yield phenomenon is not obvious, the stress when the limit deviation of the stress-strain linear relationship reaches a specified value (usually 0.2% permanent deformation).It is usually used as the evaluation index of mechanical properties of solid materials, which is the limit of actual use of materials.Because the material yield produced necking, strain increase, so that the material lost its original function.
When the stress exceeds the elastic limit, the deformation increases rapidly, and in addition to the elastic deformation, some plastic deformation also occurs.When the stress reaches point B, the plastic strain increases sharply and a small fluctuating plateau appears on the curve. This phenomenon is called yield.The maximum and minimum stresses at this stage are called upper yield point and lower yield point respectively.Because the value of the lower yield point is stable, it is used as an indicator of material resistance and is called yield point or yield strength (s or 0.2).
Some steels (such as high carbon steels) have no obvious yield phenomenon and usually take the stress at the time of slight plastic deformation (0.2%) as the yield strength of the steel, which is called conditional yield strength.
First, explain how the material deforms under force.The deformation of material can be divided into elastic deformation (the original shape can be restored when the external force is removed) and plastic deformation (the original shape cannot be restored when the external force is removed, and the shape changes).
At present, the more common method of measuring yield strength in China is to use the Tensile machine of Shanghai Farui instrument, tensile testing machine, universal material testing machine, etc., to measure the yield strength of materials!
Yield strength calculation formula: sigma = F/S, the sigma as the yield strength, the unit is “, “F materials for plastic material yield by force of the smallest, when unit is” cow “, for example, in the case of brittle material F materials for 0.2% of the original plastic deformation quantity of force, the unit is: “cow”, S to force the cross-sectional area of material, the unit is “square”.
1. When the stress exceeds the elastic limit, the deformation increases rapidly. In this case, in addition to the elastic deformation, local plastic deformation also occurs.When the stress reaches point B, the plasticity should increase sharply and the curve presents a small shaking platform. This phenomenon is called yield.The maximum and minimum stresses at this stage are called upper yield point and lower yield point respectively.Because the value of the lower yield point is relatively stable, it is taken as the index of data resistance and is called yield point or yield strength.
2, when the steel to a certain level, due to the internal grain rearrangement, its resistance to deformation can be improved again, the deformation is very fast, but only with the progress of the stress and progress, until the maximum stress.Then, the steel to resist deformation significantly reduced, and in the thinness of the occurrence of a large plastic deformation, where the specimen section speed reduced, the phenomenon of necking, until the fracture failure.The maximum stress value of steel before tensile fracture is called strength limit or tensile strength.
Simply put, the yield strength corresponds to the yield point, the point at which the metal has plastic deformation, and the corresponding strength is called the yield strength.Tensile strength refers to the ability of a material to resist external forces.
The yield strength reflects the resistance to deformation, while the tensile strength reflects the resistance to tensile failure.
What is tensile strength?
The tensile strength
Tensile strength tensile machine, tensile testing machine, universal material testing machine is the stress causing maximum uniform plastic deformation of a material.At present, the more common method to measure the tensile strength in China is to use the tensile machine of Shanghai Fa Rui instrument, universal material testing machine, etc., to measure the tensile strength of materials!
(1) In the tensile test, the maximum tensile stress suffered by the sample until its fracture is the tensile strength, and the result is expressed as MPa.Some are incorrectly called tensile strength, tensile strength, etc.
(2) When testing the tensile strength of samples with instruments, data such as tensile fracture stress, tensile yield stress and elongation at break can be obtained simultaneously.
(3) Calculation of tensile strength:
T = P/(b×d)
Where, t is tensile strength (MPa);P is the maximum load (N);B is sample width (mm);D is sample thickness (mm).
Note: The area used in the calculation is the original sectional area of the sample at the fault, not the post-fracture port sectional area.