CN112035958B - Method for calculating DFR rated value of through hole of aircraft fuel system - Google Patents
Method for calculating DFR rated value of through hole of aircraft fuel system Download PDFInfo
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Abstract
The application belongs to the field of airplane strength design, and particularly relates to a method for calculating a DFR (doubly salient Reflector) rated value of a through hole of an airplane fuel system. The method comprises the following steps: the method comprises the following steps: acquiring a correction coefficient curve of a DFR rated value of a through hole of an aircraft fuel system under different axis eccentricity values; step two: inquiring a design manual according to state parameters of the through hole of the aircraft fuel system, and determining a DFR reference value DFR BASE (ii) a Step three: determining the axis eccentricity value generated by the through hole of the aircraft fuel system in the drilling process, and interpolating a value from the correction coefficient curve to obtain a correction coefficient K corresponding to the rated value of the DFR p (ii) a Step four: and calculating a DFR rated value of the aircraft fuel system through hole under the corresponding axis eccentricity value according to a formula, and carrying out fatigue evaluation on the aircraft fuel system through hole. The method for calculating the DFR rated value of the through hole of the aircraft fuel system has the advantages of simple and novel scheme, simple implementation and sufficient theoretical basis, and can provide data support for fatigue strength calculation and structural design of aircraft fuel tank wall plates and other load-bearing structures.
Description
Technical Field
The application belongs to the field of airplane strength design, and particularly relates to a method for calculating a DFR (doubly salient Reflector) rated value of a through hole of an airplane fuel system.
Background
The aircraft structure Detail Fatigue Rating (DFR) is a fatigue performance characteristic value inherent to the aircraft structure detail and is a measure of the aircraft structure quality and fatigue performance. The basic concept is that under the action of a standard stress spectrum (equal-amplitude tensile-tensile, R is 0.06), when the service life is 105, and the confidence coefficient of 95% and the reliability of 95% are met, the maximum value of the stress spectrum (tensile stress, shear stress and lug net section tensile stress) is defined as the fatigue allowable rated value of the structural detail, namely the DFR value. The method is a method for rapidly evaluating the fatigue life of the airplane structure.
In the aircraft structure, oil tanks are arranged in the areas of wings, a fuselage and the like to meet the requirements of voyage during voyage, and a main load-bearing structure in the aircraft structure is provided with a fuel system through hole, and the structural form is shown in figure 1. In the process of machining the through hole of the fuel system, limited by the distance between the stringers and the tool operation space, the angle of the axis of the hole often generates certain deviation, the deviation of the angle influences the stress concentration of the hole, and the DFR value of the hole is reduced, so that the fatigue life evaluation of the fuel system structure is influenced.
Accordingly, a technical solution is desired to overcome or at least alleviate at least one of the above-mentioned drawbacks of the prior art.
Disclosure of Invention
The invention aims to provide a method for calculating a DFR rated value of a through hole of an aircraft fuel system, which aims to solve at least one problem existing in the prior art.
The technical scheme of the application is as follows:
a method for calculating a DFR rated value of a through hole of an aircraft fuel system comprises the following steps:
the method comprises the following steps: acquiring a correction coefficient curve of the DFR rated value of the aircraft fuel system through hole under different axis eccentric values;
step two: inquiring a design manual according to state parameters of the through hole of the aircraft fuel system, and determining a DFR reference value DFR BASE ；
Step three: determining the axis eccentricity value generated by the through hole of the aircraft fuel system in the drilling process, and interpolating a value from the correction coefficient curve to obtain a correction coefficient K corresponding to the rated value of the DFR p ；
Step four: according to the formula:
DFR＝DFR BASE ×K p
and calculating to obtain a DFR rated value of the aircraft fuel system through hole under the corresponding axis eccentricity value, and performing fatigue evaluation on the aircraft fuel system through hole.
Optionally, in the first step, the obtaining a correction coefficient curve of the DFR rated value of the aircraft fuel system through hole at different axis eccentricity values includes:
s101: obtaining the axis eccentricity data of a through hole of an aircraft fuel system, and manufacturing a first test piece with different axis eccentricity values and a second test piece with the same specification as the first test piece in a non-axis eccentricity state according to the axis eccentricity data of the through hole of the aircraft fuel system;
S102：
carrying out fatigue life test on the first test piece to obtain first life values of the aircraft fuel system through holes with different axis eccentricity values;
carrying out fatigue life test on the second test piece to obtain a second life value of the aircraft fuel system through hole in a corresponding non-axis eccentric state;
S103：
the first life value is processed in a statistical mode to obtain the median life N of the first life value 50 Further, the median lifetime N corresponding to the 99.9% reliability and the 90% confidence coefficient is obtained 99.9/90 Calculating a first DFR rated value of the aircraft fuel system through hole with different coaxial line eccentricity values according to a formula;
the second life value is processed in a statistical mode to obtain the median life N of the second life value 50 Further, the median lifetime N corresponding to the 99.9% reliability and the 90% confidence coefficient is obtained 99.9/90 Calculating a second DFR rated value of the aircraft fuel system through hole in the non-axis eccentric state according to a formula;
s104: and calculating a correction coefficient of the DFR rated value of the aircraft fuel system through hole according to the first DFR rated value and the second DFR rated value, and establishing a correction coefficient curve.
Alternatively, in S103, by the formula:
calculating a first DFR rating and a second DFR rating;
wherein N is 99.9/90 Median lifetime, N, for 99.9% reliability and 90% confidence 0 For crack formation life, σ max The peak stress of the test piece.
Optionally, after S104, the method further includes:
and combining least square fitting with linear interpolation to reduce the parameter change interval of the correction coefficient curve and obtain the optimized correction coefficient curve.
Optionally, in the second step, the state parameters include structural materials, roughness, hole making processes and surface treatment conditions of the aircraft fuel system through hole.
The invention has at least the following beneficial technical effects:
according to the method for calculating the DFR rated value of the through hole of the aircraft fuel system, the correction coefficient curve of the DFR rated value of the through hole of the aircraft fuel system considering the eccentric angle is obtained, the influence of the eccentricity of the through hole on the DFR rated value due to process limitation can be accurately evaluated by using the correction coefficient, the service life of the structure is further accurately evaluated, and a basis is provided for fatigue design of the aircraft structure.
Drawings
FIG. 1 is a schematic illustration of aircraft fuel system through-holes at different axis eccentricity values according to one embodiment of the present application;
FIG. 2 is a correction coefficient curve diagram of a method for calculating a DFR rating of a through hole of an aircraft fuel system according to an embodiment of the present application.
Detailed Description
In order to make the implementation objects, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be described in more detail below with reference to the drawings in the embodiments of the present application. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described are some, but not all embodiments of the disclosure. The embodiments described below with reference to the drawings are exemplary and intended to be used for explaining the present application and should not be construed as limiting the present application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application. Embodiments of the present application will be described in detail below with reference to the accompanying drawings.
In the description of the present application, it is to be understood that the terms "center", "longitudinal", "lateral", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate orientations or positional relationships based on those shown in the drawings, and are used merely for convenience in describing the present application and for simplifying the description, and do not indicate or imply that the referenced device or element must have a particular orientation, be constructed in a particular orientation, and be operated, and therefore should not be construed as limiting the scope of the present application.
The present application is described in further detail below with reference to fig. 1-2.
The application provides a method for calculating a DFR rated value of a through hole of an aircraft fuel system, which comprises the following steps:
the method comprises the following steps: acquiring a correction coefficient curve of a DFR rated value of a through hole of an aircraft fuel system under different axis eccentricity values;
step two: inquiring a design manual according to state parameters of the through hole of the aircraft fuel system, and determining a DFR reference value DFR BASE (ii) a In this embodiment, the state parameters include structural material, roughness, hole making process, and surface treatment condition of the aircraft fuel system through hole.
Step three: according to the process simulation, determining the axis eccentricity value generated by the through hole of the aircraft fuel system in the hole making process, and interpolating the value from the correction coefficient curve to obtain the correction coefficient K corresponding to the rated value of the DFR p ；
Step four: according to the formula:
DFR＝DFR BASE ×K p
and calculating to obtain a DFR rated value of the aircraft fuel system through hole under the corresponding axis eccentricity value, and performing fatigue evaluation on the aircraft fuel system through hole.
In one embodiment of the application, the first step of obtaining a correction coefficient curve of the DFR rated value of the aircraft fuel system through hole under different axis eccentricity values comprises the following steps:
s101: acquiring possible axis eccentricity data of the aircraft fuel system through hole according to the actual process condition of the aircraft structure fuel system through hole, manufacturing first test pieces with different axis eccentricity values according to the axis eccentricity data of the aircraft fuel system through hole, and manufacturing second test pieces with the same specification as the first test pieces in a non-axis eccentricity state;
S102：
carrying out fatigue life test on the first test piece to obtain first life values of the aircraft fuel system through holes with different axis eccentricity values;
carrying out fatigue life test on the second test piece to obtain a second life value of the aircraft fuel system through hole in a corresponding non-axis eccentric state;
S103：
the first life value is processed statistically to obtain the median life N of the first life value 50 Further, the median lifetime N corresponding to the 99.9% reliability and the 90% confidence coefficient is obtained 99.9/90 Calculating a first DFR rated value of the aircraft fuel system through hole with different coaxial line eccentricity values according to a formula;
the second life value is processed statistically to obtain the median life N of the second life value 50 Further, the median lifetime N corresponding to the 99.9% reliability and the 90% confidence coefficient is obtained 99.9/90 Calculating a second DFR rated value of the aircraft fuel system through hole in the non-axis eccentric state according to a formula;
s104: and calculating a correction coefficient of the DFR rated value of the aircraft fuel system through hole according to the first DFR rated value and the second DFR rated value, and establishing a correction coefficient curve.
The method for calculating the DFR rated value of the through hole of the aircraft fuel system comprises the following steps of S103:
calculating a first DFR rating and a second DFR rating;
wherein N is 99.9/90 Median lifetime, N, for 99.9% reliability and 90% confidence 0 For crack formation life, σ max The peak stress of the test piece.
In an embodiment of the present application, S104 further includes:
and combining least square fitting with linear interpolation to reduce the parameter change interval of the correction coefficient curve and obtain the optimized correction coefficient curve.
In one embodiment of the present application, it is contemplated that in aircraft design, due to process access limitations, no more than 25 ° of eccentricity of the aircraft fuel system vent axis occurs. In this embodiment, a first test piece having an axis eccentricity of 10 °, 20 °, or 30 ° and a second test piece having the same specification as the first test piece but having an axis eccentricity of 0 ° are designed, and the test pieces are subjected to a fatigue life test. And (3) acquiring the DFR rated value of the first test piece and the DFR rated value of the second test piece through data processing, and determining the correction coefficient of the DFR rated value of the through hole of the aircraft fuel system. And obtaining a DFR rated value correction coefficient curve of the aircraft fuel system through hole considering the eccentricity angle, which is shown in FIG. 2 and contains the axial deviation angle which may exist in the fuel system through hole and is common in the aircraft structural design, by fitting. After obtaining the correction coefficient curve, determining a DFR reference value for a fuel system through hole in an airplane structure according to material and structure details, considering axial deviation possibly caused by the actual situation of a hole making process, obtaining a corresponding correction coefficient, and finally determining an actual DFR rated value of the details according to the fact that the correction coefficient is multiplied by the DFR reference value.
According to the method for calculating the DFR rated value of the through hole of the aircraft fuel system, the correction coefficient curve of the DFR rated value of the through hole of the aircraft fuel system considering the eccentric angle is obtained, the limitation of the structure by a hole manufacturing space and a hole manufacturing tool in the actual production process is mainly considered, the axis of the hole has certain angle deviation, and the influence of deviation possibly caused by engineering practice on the fatigue life is obtained through the method. The scheme of the application is simple and novel, the implementation is simple, the theoretical basis is sufficient, and data support can be provided for fatigue strength calculation and structural design of aircraft fuel tank wall plates and other bearing structures.
The above description is only for the specific embodiments of the present application, but the scope of the present application is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present application should be covered within 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 (3)
1. A method for calculating a DFR rated value of a through hole of an aircraft fuel system is characterized by comprising the following steps:
the method comprises the following steps: the method for obtaining the correction coefficient curve of the DFR rated value of the aircraft fuel system through hole under different axis eccentricity values comprises the following steps:
s101: obtaining the axis eccentricity data of a through hole of an aircraft fuel system, and manufacturing a first test piece with different axis eccentricity values and a second test piece with the same specification as the first test piece in a non-axis eccentricity state according to the axis eccentricity data of the through hole of the aircraft fuel system;
S102：
carrying out fatigue life test on the first test piece to obtain first life values of the aircraft fuel system through holes with different axis eccentricity values;
carrying out fatigue life test on the second test piece to obtain a second life value of the aircraft fuel system through hole in a corresponding non-axis eccentric state;
S103：
the first life value is processed in a statistical mode to obtain the median life N of the first life value 50 Further, the median lifetime N corresponding to the 99.9% reliability and the 90% confidence coefficient is obtained 99.9/90 Calculating a first DFR rated value of the aircraft fuel system through hole with different coaxial line eccentricity values according to a formula;
the second life value is processed statistically to obtain the median life N of the second life value 50 Further, the median lifetime N corresponding to the 99.9% reliability and the 90% confidence coefficient is obtained 99.9/90 Calculating a second DFR rated value of the aircraft fuel system through hole in the non-axis eccentric state according to a formula;
in S103, by the formula:
calculating a first DFR rating and a second DFR rating;
wherein N is 99.9/90 Median lifetime, N, for 99.9% reliability and 90% confidence 0 For crack formation life, σ max Is the peak stress of the test piece;
s104: calculating a correction coefficient of the DFR rated value of the aircraft fuel system through hole according to the first DFR rated value and the second DFR rated value, and establishing a correction coefficient curve;
step two: inquiring a design manual according to state parameters of the through hole of the aircraft fuel system, and determining a DFR reference value DFR BASE ；
Step three: determining the axis eccentricity value generated by the through hole of the aircraft fuel system in the drilling process, and interpolating a value from the correction coefficient curve to obtain a correction coefficient K corresponding to the rated value of the DFR p ；
Step four: according to the formula:
DFR＝DFR BASE ×K p
and calculating to obtain a DFR rated value of the aircraft fuel system through hole under the corresponding axis eccentricity value, and performing fatigue evaluation on the aircraft fuel system through hole.
2. The method for calculating the DFR rating of the through hole of the aircraft fuel system as claimed in claim 1, wherein the step S104 is followed by further comprising:
and combining least square fitting with linear interpolation to reduce the parameter change interval of the correction coefficient curve and obtain the optimized correction coefficient curve.
3. The method for calculating the DFR rated value of the aircraft fuel system through hole according to claim 1, wherein in the second step, the state parameters comprise structural materials, roughness, hole making process and surface treatment condition of the aircraft fuel system through hole.
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103942418A (en) * | 2014-04-03 | 2014-07-23 | 北京工业大学 | Method for determining specific fatigue strength rated value under multi-axial loading condition |
| CN104809321A (en) * | 2013-12-31 | 2015-07-29 | 中国航空工业集团公司沈阳飞机设计研究所 | Method for analyzing service life of high maneuverability aircraft base on detail fatigue rating |
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Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104809321A (en) * | 2013-12-31 | 2015-07-29 | 中国航空工业集团公司沈阳飞机设计研究所 | Method for analyzing service life of high maneuverability aircraft base on detail fatigue rating |
| CN103942418A (en) * | 2014-04-03 | 2014-07-23 | 北京工业大学 | Method for determining specific fatigue strength rated value under multi-axial loading condition |
Non-Patent Citations (1)
| Title |
|---|
| 基于不同寿命分布的DFR值换算关系;董彦民等;《北京航空航天大学学报》;20111114(第12期);全文 * |
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