A high-reliability gear fatigue limit rapid test method based on reliability conversion coefficient

Abstract

The present application relates to a kind of high reliability gear fatigue limit fast test method based on reliability conversion coefficient, specific steps include: carrying out gear fatigue strength up-down method test, obtains reliability conversion coefficient based on mathematical statistics method;Develop Locati method fatigue test, obtain fatigue test point;Based on reference fatigue S-N curve processing Locati method test result, obtain the gear fatigue limit under 50% reliability;According to the gear fatigue limit under 50% reliability, the reliability conversion coefficient is applied to evaluate the gear fatigue limit under high reliability.Solve the problem that the required test sample size is large, the cost is high, and the test cycle is long to obtain high reliability gear fatigue limit, while reducing the test amount, can maintain the high-precision evaluation result;It can be easily applied to engineering practice, and provides efficient method support for gear anti-fatigue and high power density design.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of mechanical fatigue resistance design, and relates to a high-reliability gear fatigue limit rapid test method based on a reliability conversion coefficient. BACKGROUND

[0002] As a key component in a mechanical transmission system, the fatigue performance of a gear directly affects the reliability and service life of the entire system. In engineering practice, failures such as pitting and root fracture caused by gear fatigue failure often occur, endangering man-machine safety. Therefore, accurate evaluation of the gear fatigue limit is very important for high-performance design and safe use of gear transmission.

[0003] The gear fatigue limit under high reliability can usually be obtained through the step-up method fatigue test, however, the required test sample size is large and the test cycle is long. For example, to obtain the gear contact fatigue limit under 99% reliability through the step-up method test, more than one year is needed, which seriously restricts the progress of fatigue data construction. Therefore, a test method with short time and low cost is needed to evaluate the gear fatigue limit under high reliability.

[0004] The Locati method can quickly obtain the fatigue strength limit by stepwise incremental loading on one sample, which can greatly save cost and time, but can only obtain the fatigue limit under 50% reliability, and cannot obtain the fatigue limit under high reliability. SUMMARY

[0005] Therefore, in order to solve the problems of large test sample size, high cost, long test cycle and inability to obtain the fatigue limit under high reliability in the existing evaluation of the gear fatigue limit under high reliability, the application provides a high-reliability gear fatigue limit rapid test method based on a reliability conversion coefficient. The reliability conversion coefficient is obtained by statistical analysis of the gear fatigue limit under different reliabilities obtained by the step-up method test, the Locati method fatigue test is carried out, the Locati method test results are processed based on the reference S-N curve, the gear fatigue limit under 50% reliability is obtained, and the reliability conversion coefficient is applied to evaluate the gear fatigue limit under high reliability. This method can evaluate the gear fatigue limit under high reliability with less test cost and cycle, and can be conveniently applied to engineering practice, providing an efficient method support for gear fatigue resistance and high power density design. In order to achieve the above purpose, the application provides the following technical solutions.

[0006] A high-reliability gear fatigue limit rapid test method based on a reliability conversion coefficient, comprising the following steps:

[0007] S1, obtaining a reliability conversion coefficient: carrying out a gear fatigue strength step-up method test, and obtaining a reliability conversion coefficient based on a mathematical statistical method;

[0008] S2, Locati method gear fatigue test: carry out the Locati method gear fatigue test to obtain the fatigue test points;

[0009] S3, obtain the gear fatigue limit under 50% reliability: based on the reference S-N curve processing step S2, the Locati method test results are obtained, and the gear fatigue limit under 50% reliability is obtained;

[0010] S4, evaluate the gear fatigue limit under high reliability: according to the gear fatigue limit under 50% reliability in step S3, the reliability conversion coefficient in step S1 is applied to evaluate the gear fatigue limit under high reliability.

[0011] Further, in step S1, the gear up-down method test is carried out according to the national standard GB / T 14229-2021 or GB / T 14230-2021, the gear bending fatigue limit under different reliabilities is obtained, the results under high reliability and 50% reliability are divided, and the reliability conversion coefficient is obtained.

[0012] Further, in step S2, the test scheme is formulated according to the national standard GB / T 14229-2021 or GB / T 14230-2021, and the Locati method gear fatigue test is carried out.

[0013] Further, in step S3, the reference fatigue S-N curve is obtained according to the literature, three reference curves are obtained by up and down shifting the reference fatigue S-N curve, the Locati method test results are processed based on the three reference curves, and the gear fatigue limit under 50% reliability is obtained.

[0014] Further, the specific process of obtaining the gear fatigue limit under 50% reliability is: based on the above three reference curves, the Locati method test results are processed, and and the numerical value is calculated, the corresponding curve is drawn, and the fatigue limit value corresponding to is found, wherein is the Miner linear cumulative damage rule, indicates the fatigue limit of the gear.

[0015] The beneficial effects of the present application are:

[0016] 1. The application provides a high-reliability gear fatigue limit rapid test method based on reliability conversion coefficients, which obtains reliability conversion coefficients by statistically analyzing gear fatigue limits under different reliabilities obtained through ascending and descending method tests, carries out Locati method fatigue tests, significantly reduces the required test sample size, and further reduces the cost and period of gear fatigue tests; and based on processing the Locati method test results by using a reference fatigue S-N curve, the gear fatigue limit under 50% reliability is obtained, the gear fatigue limit under high reliability is evaluated by using the reliability conversion coefficients combined with the gear fatigue limit under 50% reliability, and the fatigue limit under high precision and high reliability can be obtained while reducing the test amount.

[0017] 2. The application provides a high-reliability gear fatigue limit rapid test method based on reliability conversion coefficients, which not only has important scientific value, but also provides an efficient and economical gear fatigue limit evaluation method for engineering practice, and has a wide application prospect.

[0018] Other advantages, objects, and features of the application will be set forth in part in the following specification taken in conjunction with the accompanying drawings, and in part will become apparent to those skilled in the art from a consideration of the following specification and drawings, or can be learned from the practice of the application. The objects and other advantages of the application can be realized and attained by means of the instrumentalities and combinations pointed out in the following specification. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to make the objects, technical solutions, and advantages of the application clearer, the preferred embodiments of the application will be described in detail below with reference to the accompanying drawings, in which:

[0020] Figure 1 A flowchart of the high-reliability gear fatigue limit rapid test method based on reliability conversion coefficients according to the application is shown in the figure;

[0021] Figure 2 The figure shows the test points and results of the 8 groups of gears in the embodiment, wherein 2a is the test points and results of A1 gear ascending and descending method, 2b is the test points and results of A2 gear ascending and descending method, 2c is the test points and results of A3 gear ascending and descending method, 2d is the test points and results of A4 gear ascending and descending method, 2e is the test points and results of A5 gear ascending and descending method, 2f is the test points and results of A6 gear ascending and descending method, 2g is the test points and results of A7 gear ascending and descending method, and 2h is the test points and results of A8 gear ascending and descending method;

[0022] Figure 3 The figure shows the reliability conversion coefficients obtained from the 8 groups of gear ascending and descending method tests in the embodiment;

[0023] Figure 4For the three gear bending fatigue Locati method test points in the examples, 4a is the Locati test point I, 4b is the Locati test point II, and 4c is the Locati test point III.

[0024] Figure 5 For the three gear bending fatigue Locati method test points in the examples, 4a is the Locati test point I, 4b is the Locati test point II, and 4c is the Locati test point III.

[0025] Figure 6 For the three gear bending fatigue Locati method test points in the examples, 4a is the Locati test point I, 4b is the Locati test point II, and 4c is the Locati test point III. DETAILED DESCRIPTION

[0026] The present application will be described in greater detail by way of specific embodiments, and as such, those skilled in the art can easily understand other advantages and purposes of the present application from the contents disclosed in the specification. The present application can also be implemented or applied in other different specific embodiments, and the details in the specification can be modified or changed in various ways based on different views and applications without departing from the spirit of the present application. It should be noted that the drawings provided in the following examples only illustrate the basic concept of the present application in a schematic manner, and the following examples and features in the examples can be combined with each other without conflict.

[0027] As shown in Figure 1 A high-reliability gear fatigue limit rapid test method based on reliability conversion coefficient, comprising the following steps:

[0028] S1, obtaining a reliability conversion coefficient: carrying out a gear fatigue strength step-up method test to obtain a reliability conversion coefficient.

[0029] The step-up method test of the gear is carried out according to the national standard GB / T 14229-2021 or GB / T 14230-2021 to obtain the gear bending fatigue limit under different reliabilities, and the result under high reliability is divided by the result under 50% reliability to obtain the reliability conversion coefficient.

[0030] S2, Locati method gear fatigue test: carrying out a Locati method gear fatigue test to obtain a fatigue test point.

[0031] The test scheme is formulated according to the national standard GB / T 14229-2021 or GB / T 14230-2021, and the Locati method gear fatigue test is carried out.

[0032] S3, obtaining the gear fatigue limit under 50% reliability: based on the reference fatigue S-N curve processing step S2, the Locati method test result is obtained. The gear fatigue limit under 50% reliability is obtained.

[0033] According to the literature, a reference fatigue S-N curve is obtained, and three reference curves are obtained by shifting the reference fatigue S-N curve up and down. Based on the three reference curves, the Locati method test results are processed, and the fatigue limit of the gear is calculated and the corresponding curve is drawn, and the fatigue limit value corresponding to is found, wherein is the Miner linear cumulative damage rule, represents the fatigue limit of the gear, and the gear fatigue limit under 50% reliability is obtained.

[0034] S4, evaluating the gear fatigue limit under high reliability: according to the gear fatigue limit under 50% reliability in step S3, the reliability conversion coefficient in step S1 is applied to evaluate the gear fatigue limit under high reliability.

[0035] Embodiment:

[0036] This embodiment takes obtaining the bending fatigue limit of the gear as an example. Eight groups of gear test pieces with different materials, processes and module numbers are subjected to the step-up and step-down method test, and the bending fatigue limit of the gear under 50% and 99% reliability is obtained. The reliability conversion coefficient is obtained by dividing the results under 99% reliability by the results under 50% reliability. The 18CrNiMo7-6 carburized ground gear with a module of 5 mm is subjected to the Locati method test, the Locati method test results are processed based on the reference fatigue S-N curve, the bending fatigue limit of the gear under 50% reliability is obtained, and the reliability conversion coefficient is applied to evaluate the bending fatigue limit of the gear under 99% reliability. The specific steps are as follows:

[0037] S1, carrying out the gear fatigue strength step-up and step-down method test, obtaining the gear bending fatigue limit under different reliabilities, dividing the results under high reliability by the results under 50% reliability, and obtaining the reliability conversion coefficient.

[0038] In the step-up and step-down method test case, the materials of the test gears include 18CrNiMo7-6, 20Cr2Ni4A, 20CrMnMo and 42CrMo, covering carburizing, quenching and tempering, carburizing + shot blasting and quenching and tempering + shot blasting process states. The basic parameters of the test gears are shown in Table 1.

[0039] Table 1: Basic parameters and process states of the case gears

[0040]

[0041] The gear bending fatigue up-down method test is carried out according to "GB / T 14230-2021 Gear Bending Fatigue Strength Test Method". First, the gear tooth profile and dangerous section parameters are obtained before the test starts, and the clamping position is determined to ensure accurate loading. The initial load is determined by pre-test or experience, and the load interval is selected as 0.04~0.06 times of the material tensile strength according to the national standard GB / T 14230-2021. The failure criterion is that the test loading frequency is reduced by 5% and the visible cracks or broken teeth appear in the root, and the cycle number is 3 million cycles as the cycle base, and the test point total number is not less than 20 and meets the closure requirements (the predicted point after the last test point and the first test point stress level should be the same level).

[0042] Figure 2 The bending fatigue up-down method test points and results of 8 groups of case gears (A1 gear, A2 gear, A3 gear, A4 gear, A5 gear, A6 gear, A7 gear and A8 gear) are shown, according to the data processing method in GB / T 14230-2021, the "failure" is taken as the "analysis event" to analyze the up-down method test results, and the gear bending fatigue limit under 50% and 99% reliability is obtained, and the result under 99% reliability is divided by the result under 50% reliability to obtain the reliability conversion coefficient of each group of test gears, Figure 3 The reliability conversion coefficient obtained by the case gear up-down method test is shown, and the average value of the reliability conversion coefficient of the 8 groups of cases is 0.924. The obtained average value of 0.924 is used for subsequent evaluation of the gear fatigue limit under 99% reliability.

[0043] S2, carry out Locati method gear fatigue test and obtain fatigue test points.

[0044] The test gear material of the Locati method test case is 18CrNiMo7-6, the processing technology is carburizing grinding, and the geometric parameters of the test gear are shown in Table 2.

[0045] Table 2: Geometric parameters of the case gear

[0046]

[0047] For 18CrNiMo7-6 carburized gears, the reference S-N curve and the estimated bending fatigue limit can be obtained from the reference “Chen D, Zhu J, Liu H, et al. Experimental investigation of the relation between the surface integrity and bending fatigue strength of carburized gears[J]. Science China Technological Sciences, 2022, 66(1): 33-46”, and the slope is -0.1144 and the intercept is 3.4402, as shown in equation (1).

[0048]

[0049] As shown in Figure 2 , the Locati method gear bending fatigue test is carried out according to the national standard “GB / T 14230-2021 Gear Bending Fatigue Strength Test Method”. The case gears are subjected to stepwise incremental loading, and the cycle number of each load level is set to 30000. The stepwise loading is carried out until the gear bending failure occurs. Figure 4 The Locati method test points obtained in the case are shown in the figure, a total of 3 Locati method test points are obtained, which are: Locati test point I, Locati test point II and Locati test point III, and the total cycle numbers of the three test points are 144998, 172047 and 176118 respectively.

[0050] S3, processing the Locati method test results in step S2 to obtain the gear fatigue limit under 50% reliability.

[0051] As shown in Figure 5 , three reference curves are obtained by shifting the reference fatigue S-N curve up and down. According to the national standard “GB / T 14230-2021 Gear Bending Fatigue Strength Test Method”, the Locati method test results are processed, and the stress level σ i of each test point is brought into the equation of the three reference curves respectively, and the corresponding life value N ij is solved. According to the cycle number n i of each stress level, the damage value n i / N ij of the corresponding stress level is calculated, and the total damage value ∑n i / N ij of each reference curve is calculated according to equation (3). The ∑n / N-σ limCurve equation, solve σ when ∑n / N = 1 lim The value is the fatigue limit value under 50% reliability. As shown in Figure 6 Fig. 4, for the implementation case, the fatigue limit values under 50% reliability of the 3 groups of Locati method test points are 604.95 MPa, 649.42 MPa, and 654.24 MPa, respectively, and the average value is 636.20 MPa, which can be considered as the bending fatigue limit of the final test gear under 50% reliability.

[0052]

[0053]

[0054] In the formula, σ i is the stress level of the test point, MPa; i is the serial number of the stress level; N ij is the corresponding life value of each stress level on each reference curve; j is the number of reference curves, in this implementation case, j is 3.

[0055] S4, according to the gear fatigue limit under 50% reliability in step S3, the gear fatigue limit under high reliability is evaluated by using the reliability conversion coefficient in step S1.

[0056] The bending fatigue limit of the 5 mm modulus carburized ground 18CrNiMo7-6 gear under 50% reliability obtained by the Locati method test is 636.20 MPa, and multiplying it by the reliability conversion coefficient 0.924, the bending fatigue limit under 99% reliability is 587.85 MPa. Compared with the bending fatigue limit under 99% reliability 607.52 MPa obtained by the step-up and step-down method test, the error is 3.24%, which proves the accuracy of applying the reliability conversion coefficient to evaluate the gear fatigue limit under high reliability. The total number of test points is reduced by 85% compared with 20 of the step-up and step-down method. The total number of cycles of the Locati method test is 493163, which is reduced by 98% compared with the total number of cycles 32511828 of the step-up and step-down method.

[0057] The present embodiment carries out the up-down method test taking carburized gears and quenched and tempered gears with different modulus and process states as examples, obtains the reliability conversion coefficient based on the mathematical statistics method, carries out the Locati method test and processes the Locati method test results according to the reference S-N curve, obtains the gear bending fatigue limit under 50% reliability, and evaluates the gear bending fatigue limit under 99% reliability by using the reliability conversion coefficient. The bending fatigue limit under 99% reliability is 587.85 MPa, and the error is 3.24% compared with 607.52 MPa obtained by the up-down method test. The number of test points is reduced by 85% compared with 20 of the up-down method by using the high-reliability gear fatigue limit rapid test method based on the reliability conversion coefficient proposed in the present embodiment; the total cycle number of the Locati method is 493163, which is reduced by 98% compared with 32511828 of the up-down method. It can be seen that the present application can significantly reduce the sample size and cost of gear fatigue test, and provide an efficient method support for gear fatigue resistance and high-power density design.

[0058] Finally, it should be pointed out that the above embodiments are only used to illustrate the technical solutions of the present application and not to limit it. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced equivalently without departing from the purpose and scope of the present technical solutions, which should be covered in the scope of the claims of the present application.

Claims

1. A high-reliability gear fatigue limit rapid test method based on reliability conversion coefficient, characterized in that, Comprise the following steps: S1, obtaining reliability conversion coefficient: carrying out gear fatigue strength lifting method test, obtaining reliability conversion coefficient based on mathematical statistics method; in the step S1, reference national standard GB / T 14229-2021 or GB / T 14230-2021 carries out gear fatigue lifting method test, obtains the gear bending fatigue limit under different reliability, divides the result under high reliability and 50% reliability, obtains reliability conversion coefficient; S2, Locati method gear fatigue test: carrying out Locati method gear fatigue test, obtaining fatigue test point; S3, obtaining the gear fatigue limit under 50% reliability: based on the reference S-N curve processing the test result in the step S2, obtaining the gear fatigue limit under 50% reliability; S4, evaluating the gear fatigue limit under high reliability: according to the gear fatigue limit under 50% reliability in the step S3, applying the reliability conversion coefficient in the step S1 to evaluate the gear fatigue limit under high reliability.

2. The high reliability gear fatigue limit rapid test method based on reliability conversion coefficient according to claim 1, characterized in that, In the step S2, according to national standard GB / T 14229-2021 or GB / T 14230-2021, the test scheme is formulated, and the Locati method gear fatigue test is carried out.

3. The high reliability gear fatigue limit quick test method based on reliability conversion coefficient according to claim 1, characterized in that, In the step S3, according to the literature, the reference fatigue S-N curve is obtained, the obtained reference fatigue S-N curve is translated up and down to obtain three reference curves, the Locati method test result is processed based on the three reference curves, and the gear fatigue limit under 50% reliability is obtained.

4. The high reliability gear fatigue limit quick test method based on reliability conversion coefficient according to claim 3, characterized in that, The specific process for obtaining the gear fatigue limit under 50% reliability is as follows: Based on the three reference curves, process the Locati method test results and calculate... n i / N i and σ′ Flim Numerical values, and make corresponding adjustments. n i / N i - σ′ Flim Curve, find the corresponding n i / N i = 1, where n i / N i For Miner's linear cumulative damage rule, σ′ Flim This indicates the fatigue limit of the gear.

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