High-cycle and low-cycle fatigue research test method of spring under high temperature load

Abstract

The invention discloses a high-cycle and low-cycle fatigue research test method of a spring under a high temperature load, and belongs to the technical field of physical measurement. The test method comprises the following steps: obtaining a spring typical part; initial mechanical property information of the typical spring part is obtained through measurement; carrying out a fatigue life test on the obtained typical spring part; after a fatigue life test of a certain cycle period is carried out, mechanical property information of the typical spring part is obtained through a static test; and performing data analysis according to the obtained mechanical property information of the typical part of the spring to form a database and a related chart. According to the invention, the fatigue test research of springs made of two materials of 50CrVA and 1Cr18Ni9 in a high-temperature environment is carried out for the first time, the elastic property after a certain number of times of tests is explored, credible test data is obtained by comparing measured data with theoretical values, and basic data support is provided for the design of product springs.

Description

Technical Field

[0001] The invention belongs to the technical field of physical measurement, and in particular relates to a high-cycle and low-cycle fatigue research and test method for a spring under high temperature load. Background Art

[0002] Mechanical springs play a vital role in mechanical design, not only for applying force, providing elasticity, but also for storing or absorbing energy. Springs have a wide range of applications, including but not limited to compression, extension, torsion, and providing power and constant force. The life of a spring is a key indicator of its performance, which is significantly affected by material selection, design characteristics, and working environment.

[0003] Although significant advances have been made in spring design and material science, spring failure modes remain a challenge for mechanical engineers. The most common failure modes include fracture due to fatigue and loss of load-bearing capacity due to stress relaxation. These failure modes are affected by a variety of factors, including load force, operating temperature, cycle rate (frequency), and corrosive environment. In aircraft engine fuel system accessories, the performance of springs is particularly critical. When operating under high fuel temperature loads, the elastic force of the spring may decay, which directly affects the overall performance of the product. Although some progress has been made in the study of spring fatigue life under normal temperature conditions, fatigue life testing under high temperature conditions is still a relatively underexplored area. Summary of the invention

[0004] The purpose of the present invention is to provide a high-cycle and low-cycle fatigue research test method for springs under high temperature loads, which provides data support for spring selection and life prediction.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0006] The test method for studying high-cycle and low-cycle fatigue of springs under high temperature loads includes the following steps:

[0007] S1. Collect and sort out spring specifications and obtain typical spring parts;

[0008] S2. Perform elastic force test on typical spring parts at room temperature to obtain the data of initial free length, stiffness and elastic force value of the spring and record them;

[0009] S3, conducting fatigue life test on the typical spring parts obtained in S1;

[0010] S4. Record the mechanical properties of typical spring parts that have undergone fatigue life tests;

[0011] S5. Perform data analysis based on the mechanical property information of typical spring parts obtained in S4 to form a database.

[0012] Preferably, the typical spring part in S1 is one of 1Cr18Ni9 and 50CrVA springs.

[0013] Preferably, the fatigue life test in S3 includes a low cycle fatigue test and a high cycle fatigue test.

[0014] Preferably, the process parameters of the low cycle fatigue test include: an applied temperature of 150° C. and a frequency load of 500 times / min.

[0015] Preferably, the high cycle fatigue test process parameters include: an applied temperature of 150° C. and a frequency load of 1000 times / min.

[0016] Preferably, in S4, the cycle period does not exceed 10 7 Second-rate.

[0017] Preferably, in S4, the cycle periods are 10 5 times, 2×10 5 times, 5×10 5 times, 10 6 One of the times.

[0018] Further preferably, the cycle period does not reach 10 5 If the spring breaks, record the number of vibrations when the spring breaks.

[0019] Preferably, the mechanical property information in S4 includes the current length, stiffness and elastic force value of the spring.

[0020] Compared with the prior art, the present invention has the following advantages and technical effects:

[0021] The present invention discloses a high-cycle and low-cycle fatigue research test method for springs under high-temperature loads. For the first time, fatigue test research on springs made of two materials, 50CrVA and 1Cr18Ni9, under high-temperature environments is carried out, and the elastic properties after a certain number of tests are explored. By comparing the measured data with theoretical values ​​such as material parameters in the "Spring Manual", reliable test data is obtained, providing basic data support for product spring design.

[0022] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the structure of the test tooling of the present invention, wherein: Figure 1 a in the figure is a schematic diagram of spring installation. Figure 1 b in it is the spring test fixture;

[0024] Figure 2It is the elastic force attenuation result of the 1Cr18Ni9 spring of the present invention;

[0025] Figure 3 It is the stress relaxation result of the 1Cr18Ni9 spring of the present invention;

[0026] Figure 4 It is the elastic force attenuation result of the 50CrVA spring of the present invention;

[0027] Figure 5 It is the stress relaxation result of the 50CrVA spring of the present invention;

[0028] Figure 6 The free length variation result of the spring of the 1Cr18Ni9 spring of the present invention;

[0029] Figure 7 The spring free length variation result of the 50CrVA spring of the present invention;

[0030] Figure 8 The stress relaxation curves of 50CrVA and 60Si2CrA springs after 72 hours in the Spring Handbook;

[0031] Fig. 9 This is the stress relaxation curve of 1Cr18Ni9 and 3Cr13 springs after 168h in the Spring Handbook;

[0032] Fig.10 This is the stress relaxation curve of 1Cr18Ni9168h in the Spring Handbook;

[0033] Fig.11 This is the stress relaxation curve of 50CrVA oil quenched and tempered steel wire and 0Cr17Ni7A steel wire spring after 168h in the Spring Handbook;

[0034] Fig.12 This is the simulation result of 1Cr18Ni9 spring force;

[0035] Fig.13 This is the stress simulation result of 1Cr18Ni9 spring;

[0036] Fig.14 This is the local stress cloud diagram of 1Cr18Ni9 spring;

[0037] Fig.15 This is the simulation result of 50CrVA spring force;

[0038] Fig.16 This is the stress simulation result of 50CrVA spring;

[0039] Fig.17 This is the local stress cloud diagram of 50CrVA spring.

[0040] Description of Reference Numerals

[0041] 1. Spring; 2. Guide rod; 3. Tooling base plate; 4. Tooling mounting hole; 5. Spring guide rod. DETAILED DESCRIPTION

[0042] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0043] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0044] In the present invention, unless otherwise specified, other test materials and instruments and equipment are conventional test materials in the art and can be purchased through commercial channels.

[0045] 1. Material selection:

[0046] Commonly used materials and common specifications of springs for the accessories of engine fuel control systems that are produced in stable batches are selected. The spring code, quantity, material, specification, etc. are shown in Table 1.

[0047] Table 1 Spring specifications

[0048]

[0049] One type of 1Cr18Ni9 and 50CrVA spring materials are selected to form two groups A and B. The test samples in group A are used for low-cycle fatigue test of springs, and the test samples in group B are used for high-cycle fatigue test of springs. The test frequency, amplitude and preload height are shown in Table 2.

[0050] Table 2 Test frequency, amplitude, preload height

[0051]

[0052] 2. Test fixture: According to the inner diameter of the spring in Table 2, the fixture guide rod is designed to be Φ12mm, with 4 guide rods and the structure is as follows: Figure 1 .

[0053] Example 1

[0054] S1. Collect and sort out spring specifications, and obtain the typical spring part 2163.067-03F1 with code 01#;

[0055] S2. Perform elastic force test on the typical spring part 2163.067-03F1 code 01# obtained in step S1. Test one point every time the free length of the spring is compressed by 0.5mm. There are 10 static force test points for each spring. Record the initial free length, stiffness and elastic force value data of the spring and perform data analysis.

[0056] S3, subjecting the typical spring part 1Cr18Ni9 obtained in step S1 to a low cycle fatigue test with an amplitude of A=50%(H-H0), an applied temperature of 150°C and a frequency load of 500 times / min;

[0057] S4, with a cycle period of 10 5 After the low-cycle fatigue test, the spring length, stiffness and elastic force values ​​of the typical spring parts are obtained through static testing and recorded.

[0058] Example 2

[0059] The test scheme is the same as in Example 1, except that the spring typical part 2163.067-03F1 is coded as 02# and the cycle period is 2×10 5 Second-rate.

[0060] Example 3

[0061] The test scheme is the same as in Example 1, except that the spring typical part 2163.067-03F1 is coded as 03# and the cycle period is 5×10 5 Second-rate.

[0062] Example 4

[0063] The test plan is the same as in Example 1, except that the spring typical part 2163.067-03F1 is coded 04# and the cycle period is 10 6 Second-rate.

[0064] Example 5

[0065] The test scheme is the same as that of Example 1, except that the typical spring is RT49-2000-04, code 01#.

[0066] Example 6

[0067] The test scheme is the same as in Example 1, except that the typical spring is RT49-2000-04, code 02#, and the cycle period is 2×10 5 Second-rate.

[0068] Example 7

[0069] The test scheme is the same as in Example 1, except that the typical spring is RT49-2000-04, code 03#, and the cycle period is 5×10 5 Second-rate.

[0070] Example 8

[0071] The test plan is the same as in Example 1, except that the typical spring is RT49-2000-04, code 04#, and the cycle period is 10 6 Second-rate.

[0072] Example 9

[0073] S1. Collect and sort out spring specifications, and obtain the typical spring part 2163.067-03F1 with code 01#;

[0074] S2. Perform elastic force test on the typical spring part 2163.067-03F1 with code number 01# obtained in step S1. Test one point for every 1mm compression of the spring free length. There are 10 static force test points for each spring. Record the initial spring free length, stiffness, and elastic force value data of the spring and perform data analysis.

[0075] S3, subjecting the typical spring part 1Cr18Ni9 obtained in step S1 to a high cycle fatigue test with an amplitude of A=50%(H-H0), an applied temperature of 150°C and a frequency load of 1000 times / min;

[0076] S4, with a cycle period of 10 5 After the high cycle fatigue test, the spring length, stiffness and elastic force values ​​of the typical spring parts are obtained through static testing and recorded.

[0077] Example 10

[0078] The test plan is the same as in Example 9, except that the spring typical part 2163.067-03F1 is coded 02# and the cycle period is 2×10 5 Second-rate.

[0079] Embodiment 11

[0080] The test plan is the same as in Example 9, except that the spring typical part 2163.067-03F1 is coded 03# and the cycle period is 5×10 5 Second-rate.

[0081] Example 12

[0082] The test plan is the same as Example 9, except that the spring typical part 2163.067-03F1 is coded 04# and the cycle period is 10 6 Second-rate.

[0083] Example 13

[0084] The test scheme is the same as that of Example 9, except that the typical spring is RT49-2000-04, code 01#.

[0085] Embodiment 14

[0086] The test scheme is the same as that of Example 9, except that the typical spring is RT49-2000-04, code 02#, and the cycle period is 2×10 5Second-rate.

[0087] Embodiment 15

[0088] The test scheme is the same as that of Example 9, except that the typical spring is RT49-2000-04, code 03#, and the cycle period is 5×10 5 Second-rate.

[0089] Example 16

[0090] The test plan is the same as in Example 9, except that the typical spring is RT49-2000-04, code 04#, and the cycle is 10 6 Second-rate.

[0091] Comparative Example 1

[0092] At room temperature, elastic force tests were performed on typical spring parts 2163.067-03F1 coded as 01#, 02#, 03#, and 04#. One point was tested every 0.5mm compression of the spring free length. There were 10 static test points for each spring, and the initial free length, stiffness, and elastic force values ​​of the spring were recorded.

[0093] Then, with the amplitude of A = 50% (H-H0) (double amplitude), a low-cycle fatigue test with a vibration frequency of 500 times / min and a high-cycle fatigue test with a vibration frequency of 1000 times / min were carried out respectively, and the test temperature was 150°C; the vibration was recorded for 10 5 times, 2×10 5 times, 5×10 5 times, 10 6 The spring length, stiffness and elastic force after 10 5 If the spring breaks, record the number of vibrations when the spring breaks.

[0094] Comparative Example 2

[0095] The test scheme is the same as that of comparative example 1, except that the typical spring parts are RT49-2000-04 coded 01#, 02#, 03#, and 04#. The mechanical property information of the typical spring parts obtained in the above embodiment is subjected to data analysis to form a database.

[0096] Spring related test data

[0097] 1. Table 3 Spring initial test data

[0098]

[0099] 2. Take a measuring point near the middle of the spring. The elastic force value near this point is usually relatively stable. That is, analyze the elastic force value of measuring point 6 in the original data to obtain the elastic force attenuation and spring stress relaxation from 0h to 133h.

[0100] The results of 1Cr18Ni9 spring force attenuation and spring stress relaxation are shown in Figure 2 and Figure 3 ; The results of 50CrVA elastic force attenuation and spring stress relaxation are shown in Figure 4 and Figure 5 .

[0101] Depend on Figure 2 and Figure 3 It can be seen that the relaxation rate of 04# spring is greater than 10% after 16.67 hours (500,000 cycles), while the relaxation rates of 01#, 02#, and 03# are between 3% and 5%, indicating that 04# spring is an exception and its data cannot be used as a basis for evaluating the failure of this batch of springs. The relaxation rates of 01#, 02#, and 03# are still less than 10% after 133h (4 million cycles).

[0102] Depend on Figure 4 and Figure 5 It can be seen that the relaxation rate of 04# spring is 4.41% after 33.33h, while the relaxation rates of 01#, 02# and 03# are between 3% and 2.3%. Overall, the stress drop is not obvious.

[0103] 3. Change of spring free length: Change of 1Cr18Ni9 spring free length, the results are shown in Figure 6 ; The results of the free length change of 50CrVA spring are shown in Figure 7 .

[0104] Depend on Figure 6 It can be seen that with the increase of fatigue test time, the free length of the four test springs gradually decreases, the 0-16.67h (0-500,000 times) segment decreases faster, and the 16.67h-133h (500,000 times-4 million times) segment decreases slower, and the curve is smooth.

[0105] Depend on Figure 7 It can be seen that with the increase of fatigue test time, the free length of the four test springs gradually decreases, and the entire curve of 0-33.33h (0-1 million times) is relatively smooth.

[0106] Comparative analysis of spring related test data

[0107] The relaxation rates of 1Cr18Ni9 and 50CrVA materials at different temperatures given in the Spring Handbook compiled by Zhang Yinghui et al. are used as reference. Figure 8-Figure 11 .

[0108] Depend on Figure 8-Figure 11It can be seen that the stress relaxation range of 50CrVA at 150℃ and 72h is 0-9%; the stress relaxation range after 168h is 0-12%. The stress relaxation range of 1Cr18Ni9 at 150℃ and 168h is 0-6%; at the same time, the same stress level and the same temperature, the elastic force of 1Cr18Ni9 is less likely to relax than 50CrVA.

[0109] from Figure 3 It can be seen that after 66.7h, the spring stress relaxation of 50CrVA is about 4%-6%, which is consistent with Figure 8 The stress relaxation range of 50CrVA after 72h is basically the same.

[0110] 4. Simulation test: The material parameters of typical spring parts are shown in Table 5.

[0111] Table 5 Material parameters of typical spring parts

[0112]

[0113] The structural strength simulation of typical 1Cr18Ni9 and 50CrVA spring parts is carried out, and the results are as follows: Figure 12-Figure 17 .

[0114] Table 61Simulation results of typical parts of Cr18Ni9 spring

[0115] Time[s] FForceReaction(Z[N 1 3.435 2 6.9124 3 10.369 4 17.267 5 24.157 6 31.03 7 3789 8 44.734 9 51.565 10 58.385 11 65.192 12 71.988

[0116] Table 7 Simulation results of typical parts of 50CrVA spring

[0117] Time[s] WForceReaction(Q[N 1 3.8681 2 7.7482 3 11.627 4 19.342 5 27.055 6 34.733 7 42.383 8 50.007 9 57.607 10 65.185 11 72.74 12 80275

[0118] Depend on Figure 12-Figure 17 It can be seen that the maximum stress of the spring appears on the inside of the spring, which is consistent with the force analysis of the spring.

[0119] The maximum stress of a typical 1Cr18Ni9 spring is 1315.3MPa, which exceeds the conditional yield strength of the material. The average stress exceeds the fatigue limit strength, posing a risk of fracture.

[0120] The maximum stress level of a typical 50CrVA spring is 1043.8MPa. Below the conditional yield strength of the material, the average stress is greater than the fatigue strength of the material, and there is still a risk of fatigue fracture, which cannot be regarded as an infinite life design requirement. From the test data, after 4 million times, the stress relaxation is close to 10%, and there is a risk of fatigue fracture. The simulation results are consistent with the measured data, and the two have been mutually verified.

[0121] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A test method for studying high-cycle and low-cycle fatigue of springs under high temperature load, characterized in that: The steps include: S1. Collect and sort out spring specifications and obtain typical spring parts; S2. Perform elastic force test on typical spring parts at room temperature to obtain the data of initial free length, stiffness and elastic force value of the spring and record them; S3, conducting fatigue life test on the typical spring parts obtained in S1; S4. Record the mechanical properties of typical spring parts that have undergone fatigue life tests; S5. Perform data analysis based on the mechanical property information of typical spring parts obtained in S4 to form a database.

2. The test method according to claim 1, characterized in that The typical spring parts in S1 are one of 1Cr18Ni9 and 50CrVA springs.

3. The test method according to claim 1, characterized in that: The fatigue life test described in S3 includes a low cycle fatigue test and a high cycle fatigue test.

4. The test method according to claim 3, characterized in that: The process parameters of the low cycle fatigue test include: an applied temperature of 150° C. and a frequency load of 500 times / min.

5. The test method according to claim 3, characterized in that: The high cycle fatigue test process parameters include: an applied temperature of 150° C. and a frequency load of 1000 times / min.

6. The test method according to claim 1, characterized in that: In S4, the fatigue life test cycle shall not exceed 10 7 Second-rate.

7. The test method according to claim 1, characterized in that: The mechanical property information in S4 includes the current length, stiffness and elastic force value of the spring.

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