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Tensile test of cold drawn seamless tubing

Tensile Test Definition

Tensile test can determine a series of strength and plasticity indexes of cold drawn seamless tubing. Strength usually refers to the ability of cold drawn seamless tubing to resist elastic deformation, plastic deformation and fracture under the action of external force. When the cold drawn seamless tubing is subjected to tensile load, the phenomenon that the obvious plastic deformation continues to occur when the load does not increase is called yielding; the stress when yielding is called the yield point or the physical yield strength, and is expressed by σS (Pa). In many cases, the cold drawn seamless tubing does not have an obvious yield point. Usually, the stress value when the residual plastic deformation of the cold drawn seamless tubing is 0.2% is used as the yield strength, which is called the conditional yield limit or the conditional yield strength, which is expressed by σ0.2 ; The maximum stress value of the cold drawn seamless tubing before fracture is called tensile strength or strength limit, expressed by σb (Pa).

Plasticity refers to the ability of cold drawn seamless tubing to plastically deform under load without damage. The commonly used plasticity indicators are elongation and section shrinkage. Elongation, also known as elongation, refers to the percentage of the ratio of total elongation to the original length after the cold drawn seamless tubing sample is broken by tensile load, expressed by δ; section shrinkage refers to the coldd rawn seamless tubing sample. After being broken by tensile load, the percentage of the ratio of the area reduced by the section to the original section area is expressed by ψ.

Experiment method

Tensile tests are carried out on a material testing machine. There are mechanical, hydraulic, electro-hydraulic or electronic servo-type testing machines. The sample type can be the full section of the cold drawn seamless tubing, or it can be processed into a round or rectangular standard sample. Some physical samples such as steel bars and wires generally do not need to be processed and keep their full cross-sections for testing. During the preparation of the sample, the structure of the cold drawn seamless tubing should be avoided from being affected by cold and hot processing, and a certain smoothness should be guaranteed.

During the test, the testing machine uniformly stretches the sample at a specified rate, and the testing machine can automatically draw a tensile curve. For materials with good plasticity such as low carbon steel, when the sample is stretched to the yield point, the force measuring pointer has obvious jitter, and the upper and lower yield points (and) can be separated. When calculating, the δ and δ of the material are often taken. ψ can be calculated by splicing the specimens after test fracture, measuring their elongation and section reduction.

Tensile test parameters

1) Maximum test force: 50N, 100N to 20KN
2) Accuracy level: 0.5 level/1 level
3) Test force measurement range: 0.2% to 100% F.S/0.4 to 100% F.S
4) Test force indication accuracy: ±0.5%/±1%
5) Test force resolution: ±250000 yards
6) Deformation measurement range: 1%—100% F.S
7) Deformation indication accuracy: ±0.5%
8) Deformation resolution: ±250000 yards
9) Large deformation measurement range: 0 to 800mm
10) Accuracy of large deformation indication: ±0.5%
11) Large deformation resolution: 0.003mm
12) Displacement indication accuracy: ±0.3%
13) Displacement resolution: 0.00004mm
14) Force rate control adjustment range: 0.005-10%F.S/S
15) Force rate control accuracy: the force control rate is less than 0.05%, and it is ±1% when F.S/S; the force control rate is greater than 0.05%, and it is ±0.3% when F.S/S;
16) Elongation rate control adjustment range: 0.005-10%F.S/S
17) Elongation rate control accuracy: the deformation control rate is less than 0.05%, and it is ±0.5% when F.S/S; the deformation control rate is greater than 0.05%, and it is ±0.2% when F.S/S;
18) Adjustment range of displacement rate control: 0.001-1000mm/min
19) Displacement rate control accuracy: ±0.2%/±0.5%
20) Constant force, constant deformation, constant displacement control range: 0.3%—100% F.S
21) Control accuracy of constant force, constant deformation and constant displacement: when the setting value is less than 10%, it is ±0.5% when F.S;
22) Effective stretching space: 900mm

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