A test for determining a series of properties of a material under tensile load, also known as a tensile test. It is one of the basic methods for testing the mechanical properties of materials. It is mainly used to test whether the materials meet the specified standards and the properties of the research materials.
Performance Index Tensile test measures a range of strength and plasticity indicators of a material. Strength generally refers to the ability of a material to resist elastic deformation, plastic deformation, and fracture under external forces. When the material is subjected to tensile load, the phenomenon that the plastic deformation continues to increase when the load does not increase is called yielding. The stress at yield, called the yield point or physical yield strength, is expressed as σS (Pascal). There are many materials in the project that have no obvious yield point. Usually, the residual plastic deformation of the material is 0.2% of the stress value as the yield strength.
The conditional yield limit or conditional yield strength is expressed as σ0.2. The maximum stress value achieved by the material before fracture, called the tensile strength or strength limit, is expressed as σb (Pascal).
Plasticity refers to the ability of metal materials to undergo plastic deformation under load without damage. Commonly used plasticity indexes are elongation and reduction of area. Elongation, also called elongation, refers to the percentage of the ratio of total elongation to the original length after the material sample is broken by the tensile load, expressed as δ. The section shrinkage is the percentage of the ratio of the area of ​​the section of the material to the area of ​​the original section after being pulled by the tensile load.
Said.
The conditional yield limit σ0.2, the strength limit σb, the elongation δ, and the section shrinkage ψ are four performance indexes that are often measured in tensile tests. Further, the elastic modulus E, the proportional limit σp, the elastic limit σe, and the like of the material can be measured.
Test Methods Tensile tests were carried out on a material testing machine. The test machine is of mechanical, hydraulic, electro-hydraulic or electronic servo type. The sample type can be full-section of the material or can be processed into a circular or rectangular standard sample. Some physical samples such as steel bars and wires generally do not need to be processed to maintain their full cross section for testing. When preparing the sample, the material structure should be protected from cold and hot processing, and a certain degree of smoothness should be guaranteed.
During the test, the test machine uniformly stretches the sample at a specified rate, and the test machine can automatically draw a tensile curve. For materials with good plasticity such as low-carbon steel, when the specimen is stretched to the yield point, the force-measuring pointer has obvious jitter, and the upper and lower yield points (and) can be separated, which is often taken during calculation. The δ and ψ of the material can be calculated by splicing the samples after the test fracture, measuring the elongation and the reduction of the section.
Stretching curve The tensile curve drawn by the testing machine is actually the load-elongation curve. If the load coordinate value and the elongation coordinate value are respectively divided by the original cross-sectional area of ​​the sample and the gauge length of the sample, the stress can be obtained. - strain curve. In the picture
The op part is in a straight line. At this time, the stress should be proportional to the ratio, the ratio is the elastic modulus, Pp is the maximum load when it is proportional, and the p point stress is the proportional limit σp. When the loading continues, the curve deviates from op until the point e, when the load is removed.
The sample can still be restored to its original state, and if it passes the e-point sample, it cannot be restored to its original state. E-point stress is the elastic limit σ
e. In engineering, it is difficult to measure the true σe, and the stress at which the residual elongation of the sample reaches 0.01% of the original gauge distance is often the elastic limit.
0.01 means. Continue to load, the sample is deformed along the es curve to reach the point s, which is the conditional yield strength σ0.2 of the yield point σS or the residual elongation of 0.2%. After the s point continues to increase the load to the maximum load b point before the break, the load at this time divided by the original cross-sectional area is the strength limit σb. After point b, the sample continues to elongate, while the cross-sectional area decreases, and the load-bearing capacity begins to decrease until the k-point breaks. The ratio of the load at the moment of the break to the cross section at the break is called the fracture strength.
Performance Index Tensile test measures a range of strength and plasticity indicators of a material. Strength generally refers to the ability of a material to resist elastic deformation, plastic deformation, and fracture under external forces. When the material is subjected to tensile load, the phenomenon that the plastic deformation continues to increase when the load does not increase is called yielding. The stress at yield, called the yield point or physical yield strength, is expressed as σS (Pascal). There are many materials in the project that have no obvious yield point. Usually, the residual plastic deformation of the material is 0.2% of the stress value as the yield strength.
The conditional yield limit or conditional yield strength is expressed as σ0.2. The maximum stress value achieved by the material before fracture, called the tensile strength or strength limit, is expressed as σb (Pascal).
Plasticity refers to the ability of metal materials to undergo plastic deformation under load without damage. Commonly used plasticity indexes are elongation and reduction of area. Elongation, also called elongation, refers to the percentage of the ratio of total elongation to the original length after the material sample is broken by the tensile load, expressed as δ. The section shrinkage is the percentage of the ratio of the area of ​​the section of the material to the area of ​​the original section after being pulled by the tensile load.
Said.
The conditional yield limit σ0.2, the strength limit σb, the elongation δ, and the section shrinkage ψ are four performance indexes that are often measured in tensile tests. Further, the elastic modulus E, the proportional limit σp, the elastic limit σe, and the like of the material can be measured.
Test Methods Tensile tests were carried out on a material testing machine. The test machine is of mechanical, hydraulic, electro-hydraulic or electronic servo type. The sample type can be full-section of the material or can be processed into a circular or rectangular standard sample. Some physical samples such as steel bars and wires generally do not need to be processed to maintain their full cross section for testing. When preparing the sample, the material structure should be protected from cold and hot processing, and a certain degree of smoothness should be guaranteed.
During the test, the test machine uniformly stretches the sample at a specified rate, and the test machine can automatically draw a tensile curve. For materials with good plasticity such as low-carbon steel, when the specimen is stretched to the yield point, the force-measuring pointer has obvious jitter, and the upper and lower yield points (and) can be separated, which is often taken during calculation. The δ and ψ of the material can be calculated by splicing the samples after the test fracture, measuring the elongation and the reduction of the section.
Stretching curve The tensile curve drawn by the testing machine is actually the load-elongation curve. If the load coordinate value and the elongation coordinate value are respectively divided by the original cross-sectional area of ​​the sample and the gauge length of the sample, the stress can be obtained. - strain curve. In the picture
The op part is in a straight line. At this time, the stress should be proportional to the ratio, the ratio is the elastic modulus, Pp is the maximum load when it is proportional, and the p point stress is the proportional limit σp. When the loading continues, the curve deviates from op until the point e, when the load is removed.
The sample can still be restored to its original state, and if it passes the e-point sample, it cannot be restored to its original state. E-point stress is the elastic limit σ
e. In engineering, it is difficult to measure the true σe, and the stress at which the residual elongation of the sample reaches 0.01% of the original gauge distance is often the elastic limit.
0.01 means. Continue to load, the sample is deformed along the es curve to reach the point s, which is the conditional yield strength σ0.2 of the yield point σS or the residual elongation of 0.2%. After the s point continues to increase the load to the maximum load b point before the break, the load at this time divided by the original cross-sectional area is the strength limit σb. After point b, the sample continues to elongate, while the cross-sectional area decreases, and the load-bearing capacity begins to decrease until the k-point breaks. The ratio of the load at the moment of the break to the cross section at the break is called the fracture strength.
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