Method for evaluating fatigue life of metal piece

Abstract

This application belongs to the technical field of fatigue life assessment of metal parts, specifically relating to a method for assessing the fatigue life of metal parts, including: selecting multiple sets of arrays (S) within a set fatigue life range for the metal part. eq (,N); where S eq Let S be the equivalent stress value of the metal part; N be the fatigue life of the metal part; calculate the equivalent stress value S of each stage of the metal part. eq The corresponding stress amplitude S a Based on the stress amplitude S of various levels of the metal component a and the roughness coefficient K of different metal parts s Calculate the fitted stress amplitude S a ′ ; Calculate the fitted stress amplitude S of each stage of the metal part a ′ The corresponding fitted equivalent stress value S eq ′ Construct metal parts with different roughness coefficients K s The fitted array (S) eq ′ By fitting the data (N), a set of corresponding fatigue life curves S for the metal parts was obtained. eq ′ -logN; Based on a set of fatigue life curves S fitted to metal parts eq ′ -logN and the corresponding Ks value are used to obtain the roughness coefficient K applicable to different roughness coefficients of metal parts. s The fatigue life calculation curve for metal parts is logN = f(S). eq ,K s ).

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metal fatigue life evaluation, and particularly relates to a metal fatigue life evaluation method. BACKGROUND

[0002] Currently, when the fatigue life of a part is evaluated in engineering, the S-N curve needs to be corrected under a specific roughness coefficient, which involves re-fitting of the S-N curve, and the process is complicated and inefficient.

[0003] The present application is proposed in view of the above technical defects.

[0004] It should be noted that the disclosure of the above background art is only used to assist in understanding the inventive concept and technical solutions of the present application, and it does not necessarily belong to the prior art of the present patent application. In the absence of explicit evidence that the above content has been disclosed on the filing date of the present application, the above background art should not be used to evaluate the novelty and inventiveness of the present application. SUMMARY

[0005] The purpose of the present application is to provide a metal fatigue life evaluation method to overcome or alleviate at least one aspect of the known technical defects.

[0006] The technical solution of the present application is:

[0007] A metal fatigue life evaluation method comprises:

[0008] Within the fatigue life interval of the metal, a plurality of groups of arrays (S eq , N) are selected; wherein S eq is the equivalent stress value of the metal; N is the fatigue life of the metal;

[0009] The equivalent stress value S eq of each level of the metal is calculated, corresponding to the stress amplitude S a ;

[0010] Based on the stress amplitude S a of each level of the metal and the different roughness coefficients K s of the metal, the fitted stress amplitude S a ' is calculated;

[0011] The fitted equivalent stress value S eq ' corresponding to the fitted stress amplitude S a ' of each level of the metal is calculated;

[0012] The fitted array (S eq ', N) of the metal under different roughness coefficients K s is constructed, and a corresponding group of metal fitted fatigue life curves S eqlogN;

[0013] fitting fatigue life curve S based on a set of metal pieces eq ′-logN and corresponding K s value, get metal piece fatigue life calculation curve logN=f(S s , K eq ) applicable to different roughness coefficients K s of metal pieces.

[0014] According to at least one embodiment of the present application, in the metal piece fatigue life evaluation method described above, the metal piece is set to a life interval of (1.0e 3 , 1.0e 6 ).

[0015] According to at least one embodiment of the present application, in the metal piece fatigue life evaluation method described above, the calculation of the equivalent stress value S eq of each level of the metal piece, the corresponding stress amplitude S a is specifically:

[0016] S eq =αS a (1-R) β ;

[0017] wherein,

[0018] R is the ratio of the stress valley value to the peak value of the metal piece;

[0019] α and β are the equivalent stress value calculation coefficients of the metal piece.

[0020] According to at least one embodiment of the present application, in the metal piece fatigue life evaluation method described above, the fitting stress amplitude S a ′ is calculated based on the stress amplitude S s of each level of the metal piece and the different roughness coefficients K a of the metal piece, and specifically:

[0021] S a ′=K s S a .

[0022] According to at least one embodiment of the present application, in the metal piece fatigue life evaluation method described above, the calculation of the fitting equivalent stress value S a ′ corresponding to the fitting stress amplitude S eq ′ of each level of the metal piece is specifically:

[0023] S eq ′=αS a ′(1-R) β ;

[0024] wherein,

[0025] R is the ratio of the stress valley value to the peak value of the metal piece;

[0026] α, β are the equivalent stress value calculation coefficients of the metal piece.

[0027] According to at least one embodiment of the present application, in the metal piece fatigue life evaluation method described above, the metal piece fatigue life curve S eq -logN is:

[0028] LogN=A+Blog(S eq +C);

[0029] wherein,

[0030] A, B, C are the calculation coefficients of the metal piece fatigue life curve;

[0031] The metal piece fatigue life curve S eq ′-logN and the corresponding Ks value are obtained based on a group of metal pieces, and a metal piece fatigue life calculation curve logN=f(S s ,K s ) suitable for different roughness coefficients K eq of the metal piece is obtained, specifically:

[0032] Based on the calculation coefficients A, B, C of the metal piece fatigue life curve S eq -logN, a group of metal piece fitting fatigue life curves S s ′-logN are fitted, and a metal piece fatigue life calculation curve logN=(S eq ,K s ,A,B,C) suitable for different roughness coefficients K eq of the metal piece is obtained.

[0033] According to at least one embodiment of the present application, in the metal piece fatigue life evaluation method described above, the calculation coefficients A, B, C of the metal piece fatigue life curve S eq -logN are used to fit a group of metal piece fitting fatigue life curves S s ′-logN, and a metal piece fatigue life calculation curve logN=(S eq ,K s ,A,B,C) suitable for different roughness coefficients K eq of the metal piece is obtained, which is completed by calling the cftool plug-in of matlab. BRIEF DESCRIPTION OF DRAWINGS

[0034] Fig. 1 is a schematic diagram of the metal piece fatigue life evaluation method provided by the embodiments of the present application.

[0035] Fig. 2 is a metal fatigue life evaluation method provided by the embodiment of the application, and the comparative diagram of the accuracy of the calculation of the fatigue life of the part when the roughness coefficient of the metal part is 0.44;

[0036] Fig. 3 is a metal fatigue life evaluation method provided by the embodiment of the application, and the comparative diagram of the accuracy of the calculation of the fatigue life of the part when the roughness coefficient of the metal part is 0.80. DETAILED DESCRIPTION

[0037] In order to make the technical solutions of the application and the advantages thereof clearer, the technical solutions of the application will be further clearly and completely described below with reference to the drawings. It should be understood that the specific embodiments described herein are only some embodiments of the application, and are only used to explain the application, but not to limit the application. It should be noted that, for the purpose of description, only parts related to the application are shown in the drawings, and other related parts can be referred to the general design. In the case of no conflict, the embodiments in the application and the technical features in the embodiments can be combined to obtain new embodiments.

[0038] In addition, unless otherwise defined, the technical terms or scientific terms used in the description of the application should be the general meanings understood by the general skilled in the art to which the application belongs. The words indicating the relative direction or position relationship, such as "upper", "lower", "left", "right", "center", "vertical", "horizontal", "inner", "outer" and the like used in the description of the application, are only used to indicate the relative direction or position relationship, and not to imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation, and the relative position relationship may also change accordingly when the absolute position of the described object changes, therefore it cannot be understood as a limitation on the application. The "first", "second", "third" and the like used in the description of the application are only for the purpose of description, and are used to distinguish different components, and cannot be understood as indicating or implying relative importance. The "one", "an" or "the" and the like used in the description of the application should not be understood as an absolute limitation on the quantity, but should be understood as the existence of at least one. The "include" or "contain" and the like used in the description of the application mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, and do not exclude other elements or objects.

[0039] In addition, it needs to be explained that, unless otherwise explicitly specified and limited, the "installation", "connection", "connection" and similar words used in the description of the application should be understood broadly, for example, the connection can be fixed connection, or detachable connection, or integral connection; can be mechanical connection, or electrical connection; can be directly connected, or indirectly connected through intermediate medium, or the internal communication of two elements, and the person skilled in the art can understand the specific meaning of the application according to the specific circumstances.

[0040] The following will be combined with the attached Figs. 1 to 3 The application is further described in detail.

[0041] A metal fatigue life evaluation method, comprising:

[0042] In the fatigue life interval of the metal, a plurality of groups of arrays (S eq ,N) are selected; wherein S eq is the equivalent stress value of the metal; N is the fatigue life of the metal;

[0043] The equivalent stress value S eq of each level of the metal is calculated; a ;

[0044] Based on the stress amplitude S a of each level of the metal and the different roughness coefficients K s of the metal, the fitting stress amplitude S a ' is calculated;

[0045] The fitting equivalent stress value S eq ' corresponding to the fitting stress amplitude S a ' of each level of the metal is calculated;

[0046] The fitting array (S eq ', N) of the metal under different roughness coefficients K s is constructed, and a corresponding fitting fatigue life curve S eq ' of the metal is obtained by fitting;

[0047] Based on a group of fitting fatigue life curves S eq ' of the metal and the corresponding K s value, the metal fatigue life calculation curve logN=f(S eq ,K s ) suitable for different roughness coefficients K s of the metal is obtained.

[0048] For the metal fatigue life evaluation method disclosed in the above embodiment, the person skilled in the art can understand that the design calculates the equivalent stress value Seq The corresponding stress amplitude S a Furthermore, the roughness coefficients K of different metal parts are respectively s Next, calculate the corresponding stress amplitude S. a Fitted equivalent stress value S eq ′, thereby constructing different roughness coefficients K for metal parts. s The fitted array (S) eq By fitting the curves (S', N), a set of corresponding fatigue life curves for the metal parts is obtained. eq -logN, based on a set of fatigue life curves S fitted to metal parts eq -logN and the corresponding K s The value is used to obtain different roughness coefficients K applicable to metal parts. s The fatigue life calculation curve for metal parts is logN=f(S) eq ,K s By correcting the SN curve in this way, when calculating the fatigue life of roughness coefficients of various metal parts, the curves can be directly substituted into the solution without having to refit the SN curve. This process is simple and highly efficient.

[0049] In some optional embodiments, in the above-described method for assessing the fatigue life of metal parts, the set life range for the metal part is (1.0e...). 3 1.0e 6 ).

[0050] In some optional embodiments, in the above-described method for assessing the fatigue life of metal parts, the calculation of the equivalent stress values ​​S at each stage of the metal part is... eq The corresponding stress amplitude S a Specifically:

[0051] S eq =αS a (1-R) β ;

[0052] in,

[0053] R is the ratio of the stress valley value to the stress peak value of the metal part;

[0054] α and β are the calculation coefficients for the equivalent stress value of the metal part.

[0055] In some optional embodiments, in the above-described method for assessing the fatigue life of metal parts, the step of basing the assessment on the stress amplitude S at various levels of the metal part... a and the roughness coefficient K of different metal parts s Calculate the fitted stress amplitude S a ′, specifically:

[0056] S a ′=K sS a .

[0057] In some optional embodiments of the metal fatigue life assessment method, the calculation of the fitting stress amplitude S a ′ of each level of the metal part corresponds to the fitting equivalent stress value S eq ′, specifically:

[0058] S eq ′=αS a ′(1-R) β ;

[0059] Wherein,

[0060] R is the ratio of the stress valley value to the peak value of the metal part;

[0061] α and β are the equivalent stress value calculation coefficients of the metal part.

[0062] In some optional embodiments of the metal fatigue life assessment method, the metal fatigue life curve S eq -logN is:

[0063] LogN=A+Blog(S eq +C);

[0064] Wherein,

[0065] A, B, and C are the calculation coefficients of the metal fatigue life curve;

[0066] Based on a group of metal fitting fatigue life curves S eq ′-logN and the corresponding K s values, a metal fatigue life calculation curve logN=f(S s ,K s ) applicable to different roughness coefficients K eq of the metal part is obtained, specifically:

[0067] Based on the calculation coefficients A, B, and C of the metal fatigue life curve S eq -logN, a group of metal fitting fatigue life curves S eq ′-logN is fitted, and a metal fatigue life calculation curve logN=(S eq ,K s ,A,B,C) applicable to different roughness coefficients K s of the metal part is obtained, which has higher fitting efficiency.

[0068] In some optional embodiments of the metal fatigue life assessment method, the metal fatigue life curve S eq-logN, the fitting fatigue life curve S eq ′-logN of the metal piece is obtained s eq s ,A,B,C) is completed by calling the plug-in cftool of matlab.

[0069] In order to enable the field to better understand the technical solutions disclosed in the present application, the following will take the metal piece of 4130 steel given in MMQDS as an example for description:

[0070] According to MMQDS, the fatigue life curve S eq -logN of the metal piece of 4130 steel is: LogN = 9.65-2.85log(S eq -61.3), and S eq =2S a (1-R) 0.59 ;

[0071] A plurality of initial arrays (S eq ,N) are selected, the equivalent stress value S eq of each level of the metal piece is calculated, the corresponding stress amplitude S a is calculated, and then the stress amplitude S a ′ and the equivalent stress value S eq ′ under the roughness coefficient K s =0.44, 0.8 of the metal piece are calculated respectively, the corresponding fitting array (S eq ′,N) is constructed, and the corresponding fitting fatigue life curve S eq ′-logN of the metal piece is obtained:

[0072]

[0073]

[0074] The plug-in cftool of matlab is called, the calculation coefficients 9.65, 2.85, 61.3 of the fatigue life curve of the metal piece are based, the fitting fatigue life curve S eq ′-logN of the metal piece under the roughness coefficient K s =0.44, 0.8 of the metal piece is fitted, the metal piece fatigue life calculation curve logN = f(S eq ,K s ,9.65, 2.85, 61.3) suitable for the roughness coefficient K s of each level of the metal piece is obtained, and is as follows:

[0075] LogN = K​​s 2 (9.65-2.854log(S eq -61.3K s ));

[0076] In K s When = 0.44, with LogN = K s 2 (9.65-2.854log(S eq -61.3K s The fatigue life of the metal part was calculated and compared with... The maximum error in calculating the fatigue life of metal parts is 5%. Fig. 2 As shown;

[0077] In K s When = 0.80, with LogN = K s 2 (9.65-2.854log(S eq -61.3K s The fatigue life of the metal part was calculated and compared with... The calculated maximum error in the fatigue life of metal parts is 1%, such as... Fig. 3 As shown;

[0078] As can be seen from the above examples, the roughness coefficient K obtained by this method is applicable to various levels of roughness coefficients for metal parts. s The fatigue life calculation curve for metal parts is logN = f(S). eqs ,K s (A, B, C) exhibits good accuracy under various roughness coefficients for metal parts.

[0079] The various embodiments in the specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0080] The technical solution of this application has been described in conjunction with the preferred embodiments shown in the accompanying drawings. Those skilled in the art should understand that the protection scope of this application is obviously not limited to these specific embodiments. Without departing from the principles of this application, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the protection scope of this application.

Claims

1. A method for evaluating fatigue life of a metal piece, characterized by, Comprising: In the fatigue life interval of the metal part, a plurality of groups of arrays (S eq ,N) are selected; wherein S eq is an equivalent stress value of the metal part; and N is a fatigue life of the metal part. calculating the equivalent stress value S of each level of the metal piece eq corresponding stress amplitude S a ; Based on the stress amplitude S of each level of the metal piece a , and the roughness coefficient K of different metal pieces s , the fitting stress amplitude S is calculated a ′ ; The calculated stress amplitude S of each level of the metal piece a ′ The corresponding equivalent stress value S eq ′ ; Constructing fitting array (S s eq ′ ,N) under different roughness coefficient K of metal parts, fitting a set of corresponding metal fitting fatigue life curve S eq ′ -logN;​ Fitting of fatigue life curve S based on a set of metal pieces eq ′ -logN and the corresponding K s values, obtaining a fatigue life calculation curve logN = f(S s , K eq ) for metal pieces with different roughness coefficients K s ; Metal fatigue life curve S eq -logN is: LogN = A + Blog(S eq + C); wherein, A, B, C are the calculation coefficients of the fatigue life curve of the metal piece; The fatigue life curve S is fitted based on a set of metal pieces eq ′ -logN and the corresponding K s value, to obtain a fatigue life calculation curve logN=f(S s , K eq ) of the metal piece with different roughness coefficients K s , specifically: Based on the metal fatigue life curve S eq The calculation coefficients A, B, C of -logN, fitting a set of metal fatigue life curve S eq ′ -logN, get the metal fatigue life calculation curve logN=f(S s eq ,K s ,A,B,C) suitable for different roughness coefficients K​ The stress amplitude S of each level of the metal-based component a , and the roughness coefficient K of different metal components s , the fitting stress amplitude S is calculated a ′ Specifically, S a ′ = K s S a .

2. The metal piece fatigue life evaluation method according to claim 1, characterized in that, The metal piece sets the fatigue life interval as (1.0e 3 , 1.0e 6 ).

3. The metal piece fatigue life evaluation method according to claim 1, characterized in that, The computing metal piece each level equivalent stress value S eq The corresponding stress amplitude S a Specifically: S eq = aS a (1 - R) β ; wherein, R is the ratio of the stress valley value to the peak value of the metal piece; α, β are the equivalent stress value calculation coefficients of the metal piece.

4. The metal piece fatigue life evaluation method according to claim 1, characterized in that, The calculation of the metal piece each level fitting stress amplitude S a ′ The corresponding fitting equivalent stress value S eq ′ Specifically: S eq ′ = aS a ′ (1 - R) β ; wherein, R is the ratio of the stress valley value to the peak value of the metal piece; α, β are the equivalent stress value calculation coefficients of the metal piece.

5. The metal piece fatigue life evaluation method according to claim 4, characterized in that, The metal fatigue life curve S eq The calculation coefficients A, B, C of -logN, fitting a set of metal fatigue life curve S eq ′ -logN, get suitable for different roughness coefficient K s Metal fatigue life calculation curve logN=f(S eq ,K s ,A,B,C), is completed by calling the plug-in cftool of matlab.

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