CN117556544A - Structural vibration fatigue critical stress calculation method - Google Patents
Structural vibration fatigue critical stress calculation method Download PDFInfo
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- CN117556544A CN117556544A CN202311690203.3A CN202311690203A CN117556544A CN 117556544 A CN117556544 A CN 117556544A CN 202311690203 A CN202311690203 A CN 202311690203A CN 117556544 A CN117556544 A CN 117556544A
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- 230000003068 static effect Effects 0.000 claims abstract description 25
- 238000000034 method Methods 0.000 claims abstract description 22
- 230000004044 response Effects 0.000 claims abstract description 20
- 230000003938 response to stress Effects 0.000 claims abstract description 18
- 239000006185 dispersion Substances 0.000 claims description 7
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- 239000002184 metal Substances 0.000 description 4
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Abstract
The application provides a structural vibration fatigue critical stress calculation method, which belongs to the technical field of structural vibration fatigue analysis, and comprises the following steps: analyzing the structural vibration fatigue and determining influencing factors of the structural vibration fatigue life; given the vibration fatigue life requirement of the structure, obtaining the critical vibration stress response meeting the vibration fatigue life requirement through the influence factors in a back-pushing way, wherein the critical vibration stress response comprises the following steps: obtaining the cycle number requirement corresponding to the full life cycle according to the vibration fatigue life requirement and the vibration response peak frequency; performing Goodman correction on the vibration fatigue curve by using static stress; and obtaining the critical vibration stress response of the structure according to the cycle number requirement corresponding to the whole life cycle and the vibration fatigue curve corrected by the static stress. According to the method, the vibration fatigue critical stress of the structure under different vibration response peak frequencies and static stress can be calculated at the initial stage of structural design, so that the structural vibration fatigue design flow is greatly simplified, and the vibration fatigue analysis efficiency is improved.
Description
Technical Field
The application belongs to the technical field of structural vibration fatigue analysis, and particularly relates to a structural vibration fatigue critical stress calculation method.
Background
At present, in the vibration fatigue design process of an aircraft structure, a forward evaluation flow method is mainly adopted, as shown in fig. 1, in the forward evaluation flow, vibration fatigue analysis needs to be carried out for the aircraft structure for multiple rounds, and each round of analysis work comprises the steps of structural dynamics modeling, vibration characteristic and dynamic response analysis, vibration fatigue life calculation, structural parameter optimization and the like, so that the iteration process is complex, and the efficiency is low.
Therefore, the critical stress meeting the vibration fatigue life requirement is estimated in the early design stage to obtain a more reasonable critical stress value, and the vibration fatigue analysis work is very necessary to be simplified based on the critical stress value.
Disclosure of Invention
The purpose of the application is to provide a structural vibration fatigue critical stress calculation method, so as to solve the technical problems of complex analysis iteration process and low efficiency in structural vibration fatigue design.
The technical scheme of the application is as follows: a method of calculating a structural vibration fatigue critical stress, the method comprising:
analyzing the structural vibration fatigue and determining influencing factors of the structural vibration fatigue life;
given the vibration fatigue life requirement of the structure, obtaining the critical vibration stress response meeting the vibration fatigue life requirement through the influence factors in a back-pushing way, wherein the critical vibration stress response comprises the following steps:
obtaining the cycle number requirement corresponding to the full life cycle according to the vibration fatigue life requirement and the vibration response peak frequency;
vibration fatigue S using static stress rms -N Curve run Goodman correction;
vibration fatigue S corrected by static stress according to cycle number requirements corresponding to full life cycle rms The N curve yields the structural critical vibrational stress response.
In a preferred embodiment of the present application, the influencing factors include:
1) Structural vibration stress response;
2) The vibration response peak corresponds to the frequency;
3) Vibration fatigue S rms -an N curve;
4) Static stress at the corresponding location.
In a preferred embodiment of the present application, the cycle number requirement corresponding to the full life cycle obtained from the vibration fatigue life requirement and the vibration response peak frequency is calculated using the following formula:
N 0 ＝α·T 0 ·f 0
wherein N is 0 The cycle number requirement corresponding to the whole life cycle is met;
alpha is a dispersion coefficient;
T 0 the vibration fatigue life is required;
f 0 is the vibration response peak frequency.
In a preferred embodiment of the present application, the dispersion coefficient is 1.5 to 2.
In the preferred embodiment of the present application, static stress is used to counter vibration fatigue S rms The Goodman correction procedure for the N curve is:
wherein S is rms The structural vibration stress root mean square, N is the corresponding cycle number, sigma m Is static stress, sigma UTS For the strength limit of the material, a and b are based on the original vibration fatigue S rms -N curve parameter, b 1 Is the corrected parameter.
In the preferred embodiment of the present application, the number of cycles is based on the full life cycleVibration fatigue S requiring static stress correction rms The structural critical vibration stress response obtained by the N curve is calculated by adopting the following formula:
in sigma 0 Is the critical vibration stress response of the structure.
According to the method, the vibration fatigue critical stress of the structure under different vibration response peak frequencies and static stress can be obtained through calculation at the initial stage of structural design, the step from stress to service life is omitted, the structural vibration fatigue design flow is greatly simplified, and the vibration fatigue analysis efficiency is improved.
Drawings
In order to more clearly illustrate the technical solutions provided by the present application, the following description will briefly refer to the accompanying drawings. It will be apparent that the figures described below are only some embodiments of the present application.
Fig. 1 is a schematic diagram of a prior art method for evaluating structural vibration fatigue in a forward direction.
Fig. 2 is a schematic diagram of a method for calculating a structural vibration fatigue critical stress according to the present application.
Fig. 3 is a schematic structural view of a metal reinforced wall panel according to an embodiment of the present application.
FIG. 4 is a graph showing the root mean square calculation result of the critical vibration stress in an embodiment of the present application.
Detailed Description
In order to make the purposes, technical solutions and advantages of the implementation of the present application more clear, the technical solutions in the embodiments of the present application will be described in more detail below with reference to the accompanying drawings in the embodiments of the present application.
As shown in fig. 2, the method for calculating the structural vibration fatigue critical stress provided by the application comprises the following steps:
step S100, analyzing structural vibration fatigue, and determining influencing factors of the structural vibration fatigue life, wherein the factors comprise:
1) Structural vibration stress response;
2) The vibration response peak corresponds to the frequency;
3) Vibration fatigue S rms -an N curve;
4) Static stress at the corresponding location (for Goodman correction).
Step S200, obtaining critical vibration stress response meeting the vibration fatigue life requirement of a given structure by reversely pushing the influencing factors 2-4 in the step I, wherein the specific process comprises the following steps:
step S201, according to the vibration fatigue life requirement T 0 And a vibration response peak frequency f 0 Taking the dispersion coefficient into consideration to obtain the cycle number requirement N corresponding to the whole life cycle 0 ：
N 0 ＝α·T 0 ·f 0 (1)
Wherein, alpha is a dispersion coefficient, which can be 1.5 to 2, but is generally 2;
step S202, using static stress to fatigue vibration S rms Goodman correction of the N curve:
wherein S is rms The structural vibration stress root mean square, N is the corresponding cycle number, sigma m Is static stress, sigma UTS For the strength limit of the material, a and b are based on the original vibration fatigue S rms Parameters of the-N curve, b 1 Is the corrected parameter;
step S203, according to the cycle number requirement N corresponding to the full life cycle 0 And static stress corrected vibration fatigue S rms -N curve, obtaining critical vibration stress response sigma of structure 0 ：
With the example of calculation of the metal reinforced wallboard structure provided in the present application shown in fig. 3, the vibration fatigue life requirement of the metal reinforced wallboard structure is 50h.
2.1, according to formula 1, the cycle number requirements corresponding to the full life cycle under the corresponding different vibration response peak frequencies can be obtained, for example, when the vibration response peak frequency is taken to be 100Hz, the dispersion coefficient is taken to be 2, and the cycle number requirements corresponding to the full life cycle are as follows:
N 0 =2×50×3600×100=3.6e+7 (times)
2.2 vibration fatigue S after static stress correction can be obtained according to 2 rms N curves, e.g. primary vibration fatigue S rms -N curve is:
S rms ＝10 3 ×N -0.2
when the static stress is 100MPa, assuming that the strength limit of the material is 500MPa, the vibration fatigue S after Goodman correction rms -N curve is:
S rms correction ＝(1-100/500)10 3 ×N -0.2 ＝10 2.903 ×N -0.2
2.3, the critical vibration stress root mean square response of the metal reinforced wallboard structure can be obtained according to 3:
σ 0 ＝10 -0.2×lg(3.6E+7)+2.903 ＝24.65(MPa)
the root mean square of the critical vibration stress corresponding to different vibration response peak frequencies and static stress values can be calculated according to the steps, and is shown in tables 1 and 4.
TABLE 1 root mean square calculation results of critical vibration stress (unit: MPa)
According to the method, the vibration fatigue critical stress of the structure under different vibration response peak frequencies and static stress can be calculated in the initial stage of structural design. In the practical application process, as the vibration response peak frequencies and the static stresses of different parts of the structure are different, the vibration fatigue critical stress can be valued according to the specific conditions of different parts by referring to fig. 4, and the structural parameter optimization is carried out by taking the critical stress as a target, so that the analysis steps from stress to service life are omitted, the structural vibration fatigue design flow is greatly simplified, and the vibration fatigue analysis efficiency is improved.
The foregoing is merely specific embodiments of the present application, but the scope of the present application is not limited thereto, and any changes or substitutions easily conceivable by those skilled in the art within the technical scope of the present application should be covered in the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.
Claims (6)
1. A method for calculating structural vibration fatigue critical stress, the method comprising:
analyzing the structural vibration fatigue and determining influencing factors of the structural vibration fatigue life;
given the vibration fatigue life requirement of the structure, obtaining the critical vibration stress response meeting the vibration fatigue life requirement through the influence factors in a back-pushing way, wherein the critical vibration stress response comprises the following steps:
obtaining the cycle number requirement corresponding to the full life cycle according to the vibration fatigue life requirement and the vibration response peak frequency;
vibration fatigue S using static stress rms -Goodman correction of the N curve;
vibration fatigue S corrected by static stress according to cycle number requirements corresponding to full life cycle rms The N curve yields the structural critical vibrational stress response.
2. The method for calculating the critical stress for structural vibration fatigue according to claim 1, wherein the influencing factors include:
1) Structural vibration stress response;
2) The vibration response peak corresponds to the frequency;
3) Vibration fatigue S rms -an N curve;
4) Static stress at the corresponding location.
3. The method for calculating the critical stress of the vibration fatigue of the structure according to claim 2, wherein the cycle number requirement corresponding to the full life cycle obtained from the vibration fatigue life requirement and the vibration response peak frequency is calculated by adopting the following formula:
N 0 ＝α·T 0 ·f 0
wherein N is 0 The cycle number requirement corresponding to the whole life cycle is met;
alpha is a dispersion coefficient;
T 0 the vibration fatigue life is required;
f 0 is the vibration response peak frequency.
4. A method of calculating a structural vibration fatigue critical stress according to claim 3, wherein the dispersion coefficient is 1.5 to 2.
5. A method of calculating the critical stress for vibration fatigue of a structure according to claim 3, wherein the static stress is used for the vibration fatigue S rms The Goodman correction procedure for the N curve is:
wherein S is rms The structural vibration stress root mean square, N is the corresponding cycle number, sigma m Is static stress, sigma UTS For the strength limit of the material, a and b are based on the original vibration fatigue S rms -N curve parameter, b 1 Is the corrected parameter.
6. The method for calculating the critical stress of structural vibration fatigue according to claim 5, wherein the vibration fatigue S is corrected by static stress according to the cycle number requirement corresponding to the whole life cycle rms The structural critical vibration stress response obtained by the N curve is calculated by adopting the following formula:
in sigma 0 Is the critical vibration stress response of the structure.
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