Calculation method for percentage reduction of area of round-rod-shaped metal material

Abstract

The invention relates to the technical field of material experiments, in particular to a round-bar-shaped metal material section reduction rate calculation method, which comprises the following steps: taking a tensile sample with a round-bar-shaped section to carry out a high-temperature tensile experiment, selecting one of two sections of samples broken in the high-temperature tensile experiment, and taking a straight line where the diameter of a fracture section circle is located as an x axis; the straight line where the axis of the sample is located is the y axis, a rectangular coordinate system is established, the side face of the fractured sample presents a curve in the established rectangular coordinate system, the total length and the total elongation of the two sections of samples and half of the original length of the whole sample before deformation are determined, and the percentage reduction of area is calculated; the method can quickly and accurately calculate the percentage reduction of area after the sample is snapped, does not need a specific measuring device, and lays a foundation for high-temperature tensile data analysis of materials.

Description

Technical Field

[0001] This invention relates to the field of materials experimental technology, and in particular to a method for calculating the reduction of area of ​​a cylindrical metal material. Background Technology

[0002] High-temperature tensile testing can reflect the combined effects of external force and temperature on the properties of metallic materials. In scientific experiments or accident analysis, it is necessary to know the characteristic values ​​and characteristic curves of materials at various temperatures, such as maximum stress, reduction of area, elongation, and true stress-true strain curves.

[0003] Currently, thermodynamic simulation testing machines are commonly used. Based on the continuous casting process of the billet, the sample is heated to a high-temperature zone, held at that temperature for a period of time, then cooled to a certain temperature, and finally subjected to high-temperature tensile testing at a specific tensile rate until the sample breaks. The cross-sectional area of ​​the broken sample is analyzed to obtain the reduction of area, thus studying the plasticity of the billet during continuous casting. Because materials have a certain fluidity at high temperatures, and the temperature distribution of the sample during heating in a thermodynamic simulation testing machine has a certain gradient, not the entire sample participates in deformation during tensile deformation. This is more pronounced in resistance-type thermodynamic simulation testing machines. If the deformation of the sample is assumed to be uniform when calculating the reduction of area, a large error will inevitably occur. The plasticity of the continuously cast billet is closely related to whether cracks occur after the continuous casting to bending and straightening process. Therefore, accurately calculating the reduction of area of ​​the broken sample is crucial.

[0004] Patent application number 201110081820.4, "Clamping Device for Measuring Elongation and Reduction of Area of ​​a Columnar Tensile Specimen," designs a device to center and fasten the fractured specimen together, and then uses vernier calipers for relevant measurements. This patent addresses the issue of centering and fastening the specimen for subsequent measurement. However, this measurement method is prone to introducing random errors, and the results will vary depending on the measurer. Furthermore, unavoidable systematic errors lead to inaccurate final calculations. Patents CN200620045221.1, "Rapid Measurement Device for Elongation and Reduction of Area of ​​a Circular Specimen," and CN200820020540.6, "Auxiliary Clamping Device for Measuring Specimen Elongation and Reduction of Area," also employ a reduction of area calculation method that uses optimized device design to reduce systematic errors. However, these methods may still be subject to random errors introduced by the measurer, resulting in inconsistent results. These methods for calculating the reduction of area can only be accomplished using specific measuring devices, and the accuracy of the measured reduction of area values ​​is closely related to the measurement accuracy of the device.

[0005] Therefore, to avoid the systematic errors introduced by measuring the cross-section of the specimen fracture surface using measuring devices, and to quickly and accurately calculate the reduction of area of ​​high-temperature tensile specimens, better measurement and calculation methods need to be developed. Summary of the Invention

[0006] This invention provides a method for calculating the reduction of area of ​​a cylindrical metal material, which can quickly and accurately calculate the reduction of area of ​​the sample after it breaks without the need for a specific measuring device, thus laying the foundation for the analysis of material tensile data at high temperatures.

[0007] To achieve the above objectives, the present invention employs the following technical solution: A method for calculating the reduction of area of ​​a cylindrical metal material includes the following steps: S1. A tensile specimen with a circular cross-section is subjected to a high-temperature tensile test. The radius of the circular cross-section of the specimen is... , length is ; S2. Select one of the two broken specimens from the high-temperature tensile test. Establish a rectangular coordinate system with the diameter of the fracture cross-section circle as the x-axis and the axis of the specimen as the y-axis. The side of the broken specimen will then show a curve in the established rectangular coordinate system. S3. Determination of feature length; The total length of the two sample sections is When the sample breaks under tension, the total elongation is ,but Half of it is ,Right now =2 ; One segment of the two fractured specimens is analyzed. The original length of this segment before deformation is half of the original length of the entire specimen before deformation. Let this segment be denoted as... The original length of the entire sample before deformation is 2. ; S4. Calculation of section reduction rate; ; in, The value is the cross-sectional area reduction of the sample.

[0008] Furthermore, one segment of the two fractured specimens is analyzed. The original length of this segment before deformation is half the original length of the entire specimen before deformation. Based on the curve equation of the side of the fractured specimen in the established rectangular coordinate system and the relationship between the constant volume of the tensile specimen involved in the deformation and the deformation process, The calculation formula is: ; in, The radius of the cross-sectional circle at the fracture location of one of the two fractured specimens.

[0009] Furthermore, the equation of the curve of the fractured specimen's side surface in the established rectangular coordinate system is: ; in, These are undetermined constants; The equation of the curve passes through two points with coordinates of ( , ( ) ,0), ( , + Then the undetermined constants can be solved. : ; .

[0010] Furthermore, the volume relationship of the tensile specimen involved in the deformation before and after deformation is given by the following formula: ; in, The formula for calculating the original volume of the deformed specimen is used. This is the formula for calculating the volume of this part of the sample after deformation.

[0011] Compared with the prior art, the beneficial effects of the present invention are: The method described in this invention can quickly and accurately calculate the reduction of area of ​​a sample after it breaks without the need for a specific measuring device, thus laying the foundation for the analysis of material tensile data at high temperatures. Detailed Implementation

[0012] The specific embodiments of the present invention will be further described below: This invention provides a method for calculating the reduction of area of ​​a cylindrical metal material, comprising the following steps: S1, High-temperature tensile test; Take a tensile specimen with a circular bar cross-section, the radius of which is... , length is A thermocouple is welded to the middle of the specimen, and then the specimen is installed on a thermal simulation testing machine for a high-temperature tensile test. The specimen is heated to a temperature T and held for a time t. Then, it is stretched at a tensile rate v at this temperature until the specimen breaks. The force value and the length of the specimen stretched are collected during the experiment.

[0013] S2. Establishment of a rectangular coordinate system; In step S1, the broken specimen is analyzed. One of the two broken specimen segments is selected. A rectangular coordinate system is established with the diameter of the fracture cross-section circle as the x-axis and the axis of the specimen as the y-axis. The side of the broken specimen segment will then show a curve in the established rectangular coordinate system.

[0014] S3. Determination of feature length; After step 1, the tensile specimen fractured into two segments under high temperature tensile stress, with a total length of [missing information]. When the sample breaks under tension, the total elongation is ,but Half of it is ,Right now =2 ; One segment of the two fractured specimens is analyzed. The length of the necking region along the specimen's axial direction represents the portion of the specimen that participates in deformation and is related to the specimen's elongation. The difference between this segment's length and half of the specimen's elongation is the original length of this segment before deformation. The original length of this segment before deformation is half of the original length of the entire specimen before deformation. Let's assume... The original length of the entire sample before deformation is 2. .

[0015] S4. Calculation of section reduction rate; The diameter of the cross-sectional circle at the selected fracture location of the sample in step S2 is measured, and then the radius of the cross-sectional circle is calculated and denoted as . According to step S2, the equation corresponding to the curve of this fractured specimen side surface in the established rectangular coordinate system can be expressed by the following formula: (1) in, These are undetermined constants; The equation of the curve passes through two points with coordinates of ( , ( ) ,0), ( , + Substituting these two data points into formula (1) yields the following formula: (2) (3) By combining equations (2) and (3), the undetermined constants can be solved. : (4) (5) From formulas (4) and (5), we can see that the undetermined constants are... With elongation Original sample length 2 and the radius of the cross-section circle at the fracture end of the specimen. Closely related; Based on the principles of calculus, and considering the invariant volume of the tensile specimen before and after deformation in the deformed portion, the following formula applies: (6) The left side of formula (6) is the original volume calculation formula for the part of the specimen that participates in deformation, and the right side is the volume calculation formula for the part of the specimen after deformation. Combining formulas (4), (5), and (6), we get: (7) As can be seen from formula (7), the original length of the part of the specimen involved in deformation and the total elongation of the specimen during high-temperature tensile process are determined by the original radius of the specimen and the radius of the fracture cross-section after the specimen breaks. Transform formula (7) into a formula for calculating the reduction of area: (8) The following embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiments. Unless otherwise specified, the methods used in the following embodiments are conventional methods.

[0016] Example 1 A method for calculating the reduction of area of ​​a cylindrical metal material includes the following steps: S1, High-temperature tensile test; Low-carbon microalloyed steel billets were selected and machined into circular bar-shaped tensile specimens with dimensions of Φ10×125mm. A thermocouple was welded to the center of the specimen. The specimen was then mounted on a thermal simulation testing machine for a high-temperature tensile test. The specimen was heated to 900℃ and held for 180s. Then, at this temperature, a 2×10⁻⁶ ohmmeter was applied. -3 s -1 The sample was stretched at a certain stretching rate until it broke. During the experiment, the force value and the length of the stretching of the sample were collected.

[0017] S2. Establishment of a rectangular coordinate system; Analyze the broken specimen in step 1. Select one of the two broken specimen segments and establish a rectangular coordinate system with the diameter of the fracture cross-section circle as the x-axis and the axis of the specimen as the y-axis. The side of this broken specimen segment will then show a curve in the established rectangular coordinate system.

[0018] S3. Determination of feature length; After step 1, the tensile specimen fractured into two segments under high temperature tensile stress, with a total length of [missing information]. =130mm, when the specimen breaks under tension, the total elongation is =5mm, half of it =2.5mm; One segment of the two fractured specimens is analyzed. The length of the necking region along the specimen's axial direction represents the portion of the specimen that participated in the deformation and is related to the specimen's elongation. The difference between this segment's length and half of the specimen's elongation is the original length of this segment before deformation. The original length of this segment before deformation is half of the original length of the entire specimen before deformation. =6.8mm, then the original length of the entire sample before deformation is 2 =13.6mm.

[0019] S4. Calculation of section reduction rate; The diameter of the cross-sectional circle at the selected fracture location of the sample in step S2 is measured, and then the radius of the cross-sectional circle is calculated, denoted as . According to step S2, the equation corresponding to the curve of this fractured specimen side surface in the established rectangular coordinate system can be expressed by formula (1): The equation of the curve passes through two points with coordinates of ( , ( ) If (0), (5, 9.3), then substituting these two data points into formula (1) yields the following formula: (9) (10) By combining equations (9) and (10), the undetermined constants can be solved. : (11) (12) From formulas (11) and (12), it can be seen that the undetermined constants Radius of the fracture surface of the specimen Related; Based on the principles of calculus, and considering the volume invariance of the tensile specimen before and after deformation in the deformed part, we can... Substituting into formula (6), we get: (13) The reduction of area is then calculated using formula (8). .

[0020] Example 2 A method for calculating the reduction of area of ​​a cylindrical metal material includes the following steps: S1, High-temperature tensile test Low-carbon microalloyed steel billets were selected and machined into circular bar-shaped tensile specimens with dimensions of Φ10×125mm. A thermocouple was welded to the center of the specimen. The specimen was then mounted on a thermal simulation testing machine for a high-temperature tensile test. The specimen was heated to 1000℃ and held for 180s. Then, at this temperature, a 2×10⁻⁶ ohmmeter was applied. -3 s -1 The sample was stretched at a certain stretching rate until it broke. During the experiment, the force value and the length of the stretching of the sample were collected.

[0021] S2. Establishment of a rectangular coordinate system; Analyze the broken specimen in step 1. Select one of the two broken specimen segments and establish a rectangular coordinate system with the diameter of the fracture cross-section circle as the x-axis and the axis of the specimen as the y-axis. The side of this broken specimen segment will then show a curve in the established rectangular coordinate system.

[0022] S3. Determination of feature length; After step 1, the tensile specimen fractured into two segments under high temperature tensile stress, with a total length of [missing information]. =132mm, the total elongation at tensile fracture of the specimen is =7mm, half of it =3.5mm; One segment of the two fractured specimens is analyzed. The length of the necking region along the specimen's axial direction represents the portion of the specimen that participates in deformation and is related to the specimen's elongation. The difference between this segment's length and half of the specimen's elongation is the original length of this segment before deformation. The original length of this segment before deformation is half of the original length of the entire specimen before deformation. Let's assume... =6.09mm, then the original length of the entire sample before deformation is 2. =12.18mm.

[0023] S4. Calculation of section reduction rate; The diameter of the cross-sectional circle at the selected fracture location of the sample in step S2 is measured, and then the radius of the cross-sectional circle is calculated, denoted as . According to step S2, the equation corresponding to the curve of the side of the fractured specimen in the established rectangular coordinate system can be expressed by formula (1). The equation of the curve passes through two points with coordinates of ( , ( ) If , 0)\(5, 9.59), then substituting these two data points into formula (1) yields the following formula: (14) (15) By combining equations (14) and (15), the undetermined constants can be solved. : (16) (17) From formulas (16) and (17), it can be seen that the undetermined constants Radius of the fracture surface of the specimen Related; Based on the principles of calculus, and considering the volume invariance of the tensile specimen before and after deformation in the deformed part, we can... Substituting into formula (6), we get: (18) The reduction of area is then calculated using formula (8). .

Claims

1. A method for calculating the reduction of area of ​​a cylindrical metal material, characterized in that, Includes the following steps: S1. A tensile specimen with a circular cross-section is subjected to a high-temperature tensile test. The radius of the circular cross-section of the specimen is... , length is ; S2. Select one of the two broken specimens from the high-temperature tensile test. Establish a rectangular coordinate system with the diameter of the fracture cross-section circle as the x-axis and the axis of the specimen as the y-axis. The side of the broken specimen will then show a curve in the established rectangular coordinate system. S3. Determination of feature length; The total length of the two sample sections is When the sample breaks under tension, the total elongation is ,but Half of it is ,Right now =2 ; One segment of the two fractured specimens is analyzed. The original length of this segment before deformation is half of the original length of the entire specimen before deformation. Let this segment be denoted as... The original length of the entire sample before deformation is 2. ; S4. Calculation of section reduction rate; ； in, The value is the cross-sectional area reduction of the sample.

2. The method for calculating the reduction of area of ​​a cylindrical metal material according to claim 1, characterized in that, The analysis focuses on one segment of the two fractured specimens. The original length of this segment before deformation is half the original length of the entire specimen before deformation. Based on the curve equation of the side of the fractured specimen in the established rectangular coordinate system and the relationship between the constant volume of the tensile specimen involved in the deformation and the deformation process, the analysis proceeds accordingly. The calculation formula is: ； in, The radius of the cross-sectional circle at the fracture location of one of the two fractured specimens.

3. The method for calculating the reduction of area of ​​a cylindrical metal material according to claim 2, characterized in that, The equation of the curve of the side surface of the fractured specimen in the established rectangular coordinate system is: ； in, These are undetermined constants; The equation of the curve passes through two points with coordinates of ( , ( ) ,0), ( , + Then the undetermined constants can be solved. : ； 。 4. The method for calculating the reduction of area of ​​a cylindrical metal material according to claim 3, characterized in that, The volume relationship of the tensile specimen involved in deformation before and after deformation is given by the following formula: ； in, The formula for calculating the original volume of the deformed specimen is used. This is the formula for calculating the volume of this part of the sample after deformation.

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