A method for testing uniaxial creep threshold of metal materials

Abstract

The present invention relates to a method for testing the uniaxial creep threshold of a metal material, comprising: step 1, setting a nominal stress and performing a creep test on the metal material sample based on the nominal stress; step 2, if the creep strain within a preset time is greater than 1 / 10,000, reducing the nominal stress and re-performing the creep test for the preset time using a new sample; and re-performing step 2 or step 3; step 3, if the creep strain within the preset time is less than or equal to 1 / 10,000, increasing the nominal stress and continuing the creep test for the same preset time until the creep strain within the preset time is greater than 1 / 10,000, and then stopping the test; and step 4, obtaining the creep threshold of the sample. The present invention can quickly measure the uniaxial creep threshold of a metal material, saving testing costs.

Description

Technical Field

[0001] The present invention belongs to the technical field of material and parts testing, and in particular relates to a uniaxial creep threshold testing method for metal materials. Background Art

[0002] Creep is a crucial phenomenon in material mechanics. Rapid and accurate determination of a material's creep threshold is crucial for the long-term service safety and design of materials and structures. Existing uniaxial creep threshold determination methods for metallic materials are slow and costly. Therefore, a rapid and accurate method for testing material creep thresholds is urgently needed. Summary of the Invention

[0003] The present invention provides a method for testing the uniaxial creep threshold of a metal material, so as to solve the problems of slow measuring speed and high cost in the prior art for measuring the uniaxial creep threshold of a metal material.

[0004] To achieve the above objectives, the present invention relates to a method for testing the uniaxial creep threshold of a metal material, comprising:

[0005] Step 1: setting a nominal stress, wherein the nominal stress is 0.6 to 0.65 times the yield strength of the metal material, and performing a creep test on the metal material sample based on the nominal stress;

[0006] If it is determined in step 2 that the creep strain within the preset time is greater than 1 / 10000, the nominal stress is reduced and a new specimen is used to repeat the creep test for the preset time, wherein the nominal stress is reduced by 0.1 times the yield strength; and step 2 or step 3 is performed again;

[0007] If it is determined in step 3 that the creep strain within the preset time is less than or equal to 1 / 10000, the nominal stress is increased by 0.02 times the yield strength, and the creep test is continued for the same preset time until it is determined that the creep strain within the preset time is greater than 1 / 10000, and the test is stopped, wherein the preset time is not less than 10 hours;

[0008] In step 4, the nominal stress of the previous level at which the creep strain is greater than 1 / 10000 of the lowest nominal stress is used as the creep threshold of the sample.

[0009] Preferably, the test is stopped until it is determined that the creep strain within the time is greater than 1 / 10000, and the test is also stopped. If it is difficult to accurately determine whether the cumulative creep strain is greater than 1 / 10000 during the test, the test is stopped when the creep deformation changes significantly with time; or if it is difficult to accurately determine whether the creep strain is greater than 1 / 10000 during the test, the test is stopped when the test stress is 0.86 times the yield strength.

[0010] Preferably, after the test is stopped, the nominal stress of the previous level with the cumulative creep strain greater than 1 / 10000 of the lowest nominal stress can be used as the creep threshold of the sample, and the creep strain within the preset time under different nominal stresses is obtained based on the obtained creep test data.

[0011] The present invention relates to a method for testing the uniaxial creep threshold of a metal material, which has the following beneficial effects compared with the prior art:

[0012] This method can be used to test and estimate the uniaxial creep threshold of metal materials under given conditions. This invention is of great significance for rapidly understanding the creep properties of metal materials. This patented method can rapidly determine the uniaxial creep threshold of metal materials, significantly reducing testing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A schematic diagram of a method for testing the uniaxial creep threshold of a metal material in an embodiment Figure 1 .

[0014] Figure 2 The shape and size of the Ti80 titanium alloy tensile creep specimen in the embodiment (unit: mm).

[0015] Figure 3 1 is the relationship between creep strain and time within 10 h of creep at different test stress levels in the embodiment. DETAILED DESCRIPTION

[0016] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It will be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only illustrate portions relevant to the present invention, not all structures.

[0017] Example

[0018] A uniaxial creep threshold test method for metallic materials, see Figure 1 ,

[0019] like Figure 1 As shown, the present invention provides a uniaxial creep threshold test method for metal materials, which is used for uniaxial creep threshold test of metal materials and includes the following steps: S101 to S104.

[0020] S101 sets the nominal stress, which is 0.6 to 0.65 times the yield strength of the metal material. A creep test is performed on the metal material specimen based on the nominal stress.

[0021] Conducting creep tests on metal material specimens, specifically including: conducting uniaxial creep threshold tests on metal materials.

[0022] In some embodiments, the nominal stress is 0.65 times the yield strength of the metallic material.

[0023] If it is determined in S102 that the creep strain within the preset time is greater than 1 / 10000, the nominal stress is reduced and a new specimen is used to re-perform the creep test for the preset time, wherein the nominal stress is reduced by 0.1 times the yield strength; and step 2 or step 3 is performed again.

[0024] If it is determined in S103 that the creep strain within the preset time is less than or equal to 1 / 10000, the nominal stress is increased by 0.02 times the yield strength, and the creep test is continued for the same preset time until it is determined that the creep strain within the preset time is greater than 1 / 10000, and the test is stopped. The preset time is not less than 10 hours.

[0025] S104 takes the nominal stress of the previous level with a creep strain greater than 1 / 10000 of the lowest nominal stress as the creep threshold of the specimen.

[0026] In this embodiment, the test is stopped until it is determined that the creep strain within the time period is greater than 1 / 10000. The method further includes: if it is difficult to accurately determine whether the cumulative creep strain is greater than 1 / 10000 during the test, the test is stopped when the creep deformation changes significantly with time; or if it is difficult to accurately determine whether the cumulative creep strain is greater than 1 / 10000 during the test, the test is stopped when the test stress reaches 0.86 times the yield strength. Stopping the test when the creep deformation changes significantly with time as observed by the experimenter facilitates experimental operation and reduces the amount of calculation required to determine the creep strain.

[0027] In this embodiment, S101 sets the nominal stress to be between 0.6 and 0.65 times the yield strength of the metal material, and further includes: S105 obtaining the yield strength of the metal material through a uniaxial test.

[0028] In this embodiment, after the test is stopped at S103, S104 uses the nominal stress of the previous level with a creep strain greater than 1 / 10000 of the lowest nominal stress as the creep threshold of the sample, and also includes S106 obtaining the creep strain within the preset creep time under different nominal stresses based on the obtained creep test data.

[0029] In order to better illustrate the solution of the present invention, the following is an example of the uniaxial tensile creep threshold test of a Ti80 titanium alloy sample at room temperature. Figure 2 As shown, the following steps are included:

[0030] First, the tensile yield strength (σs) of Ti80 titanium alloy was obtained by uniaxial tensile testing to be 811.66±16.8 MPa. The nominal stress was selected as 0.65 times the tensile yield strength, the creep time was selected as 10 h, and the nominal stress increase was selected as 0.02 times the yield strength.

[0031] Then, the uniaxial tensile creep threshold test of Ti80 titanium alloy specimens was carried out at room temperature. The creep test was carried out using an electronic tensile testing machine RDL-100. Figure 2 As shown in the figure. During the test, an extensometer was used to record the creep deformation and observe the degree of change in creep deformation over time at different test stresses. When the nominal stress was 0.83σs, the creep deformation increased significantly over time and the test was stopped. The obtained test data was processed to obtain the relationship between creep strain and time within 10 hours of creep at different test stress levels, as shown in the figure. Figure 3 shown.

[0032] from Figure 3 It can be seen that when the nominal stress is between 0.65σs and 0.73σs, the creep strain within 10 hours of creep is less than 1 / 10000. When the nominal stress is 0.75σs, the creep strain within 10 hours of creep is greater than 1 / 10000. Therefore, the creep threshold of this specimen is 0.73σs, or 592.5 MPa.

[0033] It should be noted that, in this document, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or apparatus comprising the element.

[0034] The above are only preferred embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for testing the uniaxial creep threshold of a metal material, characterized in that: include: Step 1: Setting a nominal stress, where the nominal stress is 0.6 to 0.65 times the yield strength of the metal material, performing a creep test on the metal material based on the nominal stress, determining whether the creep strain within a preset time is greater than 1 / 10000, and selecting whether to proceed to step 2 or step 3; Step 2: If the creep strain within the preset time is greater than 1 / 10000, the nominal stress is reduced and a new specimen is used to repeat the creep test for the preset time, wherein the nominal stress is reduced by 0.1 times the yield strength. The creep strain within the preset time is again determined to be greater than 1 / 10000, and step 2 or step 3 is selected. Step 3: If it is determined that the creep strain within the preset time is less than or equal to 1 / 10000, the nominal stress is increased by 0.02 times the yield strength, and the creep test is continued for the same preset time. It is again determined whether the creep strain within the preset time is greater than 1 / 10000. If not, the process is repeated: the nominal stress is increased by 0.02 times the yield strength, and the creep test is continued for the preset time. If so, the test is stopped, wherein the preset time is not less than 10 hours. In step 4, the creep strain within the preset time is greater than the nominal stress of the previous level of the lowest nominal stress of 1 / 10000 as the creep threshold of the metal material.

2. A metal material uniaxial creep threshold test method according to claim 1, characterized in that: The step of re-determining whether the creep strain within the preset time is greater than 1 / 10000, and if so, stopping the test, further includes: if it is difficult to accurately determine whether the creep strain is greater than 1 / 10000 during the test, stopping the test when the creep deformation changes significantly with time; or if it is difficult to accurately determine whether the creep strain is greater than 1 / 10000 during the test, stopping the test when the test stress is 0.86 times the yield strength.

3. A metal material uniaxial creep threshold test method according to claim 2, characterized in that: Before setting the nominal stress to 0.6 to 0.65 times the yield strength of the metal material, the method further includes: The yield strength of the metal material is obtained by a uniaxial test.

4. The method for testing the uniaxial creep threshold of a metal material according to claim 1, characterized in that: After the test is stopped, the nominal stress of the previous level where the creep strain is greater than 1 / 10000 of the lowest nominal stress can be used as the creep threshold of the metal material, and the method also includes obtaining the creep strain within the preset time under different nominal stresses based on the obtained creep test data.

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