CN109592074B - Method for determining loading frequency of airplane structure fatigue test - Google Patents
Method for determining loading frequency of airplane structure fatigue test Download PDFInfo
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- CN109592074B CN109592074B CN201811311325.6A CN201811311325A CN109592074B CN 109592074 B CN109592074 B CN 109592074B CN 201811311325 A CN201811311325 A CN 201811311325A CN 109592074 B CN109592074 B CN 109592074B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64F—GROUND OR AIRCRAFT-CARRIER-DECK INSTALLATIONS SPECIALLY ADAPTED FOR USE IN CONNECTION WITH AIRCRAFT; DESIGNING, MANUFACTURING, ASSEMBLING, CLEANING, MAINTAINING OR REPAIRING AIRCRAFT, NOT OTHERWISE PROVIDED FOR; HANDLING, TRANSPORTING, TESTING OR INSPECTING AIRCRAFT COMPONENTS, NOT OTHERWISE PROVIDED FOR
- B64F5/00—Designing, manufacturing, assembling, cleaning, maintaining or repairing aircraft, not otherwise provided for; Handling, transporting, testing or inspecting aircraft components, not otherwise provided for
- B64F5/60—Testing or inspecting aircraft components or systems
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/32—Investigating strength properties of solid materials by application of mechanical stress by applying repeated or pulsating forces
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Abstract
A method for determining the loading frequency of an aircraft structure fatigue test is characterized by comprising the following steps: step one, carrying out static strain measurement under the load of each peak value and each trough value; calculating a static force measurement strain average value; step three, carrying out fatigue spectrum strain measurement; step four, calculating the relative error eta between the fatigue walking spectrum strain measurement value and the static measurement strain average valuekJudgment of etakWhether or not to satisfy
The method has the advantages of correct theoretical basis, clear and simple implementation steps and clear engineering concept. The invention solves the problem that the fatigue loading frequency is difficult to determine in the airplane structure fatigue test.
Description
Technical Field
The invention belongs to the field of aviation fatigue damage tolerance tests, and particularly relates to a method for determining loading frequency of an airplane structure fatigue test.
Background
The fatigue test of the airplane structure generally has a long test period, and the test period is related to the severity of a load spectrum, low-load truncation and test loading frequency.
The determination of the load spectrum severity and the low load cutoff is carried out by a test proposing party through a large amount of theoretical analysis and research before a test planning stage and a test, and finally the test proposing party is clear in a test task book. And the structural fatigue test loading frequency is determined according to a debugging result by combining the conditions of test deformation coordination and the like in the test debugging process.
The research on the loading frequency of the airplane structure fatigue test has less public data research at home and abroad, and a feasible method for determining the loading frequency of the structure fatigue test cannot be provided aiming at the aspects of the self characteristics, the load, the stress and the like of the airplane structure.
Disclosure of Invention
The purpose of the invention is: a method for determining the loading frequency of an airplane structure fatigue test is provided.
The technical scheme of the invention is as follows: a method for determining the loading frequency of an aircraft structure fatigue test comprises the following steps:
step one, carrying out static strain measurement under the load of each peak value and each trough value. According to the sequence in the load spectrum arrangement, sequentially and respectively according to the static strain measurement requirement, measuring the strain value epsilon of the strain gauge of the monitoring part (including the main checking part and the load monitoring part) of each peak value and each valley value under 100 percent of the loadijAnd N is the total number of peaks and troughs in the load spectrum, and M is the number of strain sheets of monitoring parts (including main checking parts and load monitoring parts) in the test piece.
And step two, calculating the strain average value of the static measurement. According to the step one, the measurement is repeated for 3 times, and the average value of each strain measurement value is calculated respectively
Wherein the content of the first and second substances,
kthe number of repeated measurements.
And step three, carrying out fatigue spectrum strain measurement. Under the loading frequency assumed initially, spectra are drawn according to the sequence of the load spectra, and strain values epsilon 'of the strain gauge are measured at each peak value and each trough value instantly'ijkAnd the loading frequency of the initial hypothesis is the corresponding hypothesis times of the loading frequency of the initial hypothesis, wherein the loading frequency of the initial hypothesis corresponds to the hypothesis times of the initial hypothesis, and the loading frequency of the initial hypothesis corresponds to the hypothesis times of the loading frequency of the initial hypothesis.
Step four, calculating the relative error eta between the fatigue walking spectrum strain measurement value and the static measurement strain average valuekJudgment of etakWhether or not to satisfy
If the frequency is satisfied, the initially assumed loading frequency can be used as the loading spectrum-moving frequency of the formal fatigue test of the structure. If not, returning to the third step, readjusting the loading spectrum frequency, and continuing to measure and judge until the requirements are met.
The invention has the advantages that:
the invention provides a method for determining the loading frequency of an airplane structure fatigue test, which is provided from the debugging angle of the airplane structure fatigue test aiming at the problem of determining the loading frequency of the fatigue load in the airplane structure fatigue test. Based on the characteristics of long test period, multiple loading points, high loading coordination difficulty, difficulty in determining the loading frequency of the fatigue load and the like in the fatigue test of the airplane structure, the invention provides the method for determining the proper loading frequency by firstly carrying out static strain measurement under various working conditions, then carrying out fatigue strain measurement on complete spectrum blocks under different frequencies, and finally calculating and judging the relative error between the fatigue strain measurement value and the static strain measurement value. The method has the advantages of correct theoretical basis, clear and simple implementation steps and clear engineering concept. The invention solves the problem that the fatigue loading frequency is difficult to determine in the airplane structure fatigue test.
Drawings
FIG. 1 is a schematic view of a fatigue load peak valley;
FIG. 2 is a schematic view of a wave block of fatigue loading;
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings, referring to fig. 1 to 2.
As shown in FIG. 1, a schematic diagram of the fatigue load peaks and troughs is shown, wherein a schematic diagram of 4 wave blocks in a fatigue test is given according to the sequence of the peaks and the troughs. The device consists of 4 wave crests, 4 wave troughs, a time shaft and a load value.
As shown in fig. 2, a diagram of a wave block for fatigue loading.
A method for determining the loading frequency of an aircraft structure fatigue test comprises the following steps:
step one, carrying out static strain measurement under the load of each peak value and each trough value. According to the sequence in the load spectrum arrangement, sequentially and respectively according to the static strain measurement requirement, measuring the strain value epsilon of the strain gauge of the monitoring part (including the main checking part and the load monitoring part) of each peak value and each valley value under 100 percent of the loadijN is the total number of peaks and troughs in the load spectrum, and M is the monitor in the test pieceThe number of strain gauges of the control part (including the main checking part and the load monitoring part).
And step two, calculating the strain average value of the static measurement. According to the step one, the measurement is repeated for 3 times, and the average value of each strain measurement value is calculated respectively
Wherein the content of the first and second substances,
k is the number of repeated measurements.
And step three, carrying out fatigue spectrum strain measurement. Under the loading frequency assumed initially, spectra are drawn according to the sequence of the load spectra, and strain values epsilon 'of the strain gauge are measured at each peak value and each trough value instantly'ijkAnd the input frequency is the initial assumed load frequency, and the input frequency is the initial assumed load frequency.
Step four, calculating the relative error eta between the fatigue walking spectrum strain measurement value and the static measurement strain average valuekJudgment of etakWhether or not to satisfy
If the frequency is satisfied, the initially assumed loading frequency can be used as the loading spectrum-moving frequency of the formal fatigue test of the structure. If not, returning to the third step, readjusting the loading frequency, and continuing to measure and judge until the requirements are met.
Examples
The present invention will be described in further detail with reference to a specific example.
A method for determining the loading frequency of an aircraft structure fatigue test comprises the following steps:
it is known that:
the total number N of peaks and troughs in the load spectrum is 4 (each load value is 0N, 1200N, -800N, 1500N, -500N, 0N in sequence), and the number M of strain gauges at monitoring parts (including main checking parts and load monitoring parts) in the test piece is 3.
Step one, the process is carried out under the loads of all wave crests and wave troughsAnd (4) measuring static force strain. Strain values epsilon of strain gauges of monitoring parts under the loads of 1200N, -800N, 1500N and-500N are measured according to the sequence in the load spectrum arrangement and the static strain measurement requirements respectively in sequenceij,(i＝1,2,3......,N；j＝1,2,3,......,M)。
And step two, calculating the strain average value of the static measurement. Repeating the step one for 3 times, and respectively calculating the average value of each strain measurement value
Wherein the content of the first and second substances,
k is the number of repeated measurements. Calculated, the average value of the static measurement strain is respectively
And step three, carrying out instantaneous fatigue strain measurement on each peak value and each valley value when the load spectrum (0N, 1200N, -800N, 1500N, -500N, 0N) and the initially assumed loading frequency (Z is 5 wave blocks per minute) are subjected to spectrum walking. According to the sequence of the complete load spectrum and the loading frequency, the strain values of the strain gauges of the monitoring parts (including the main checking part and the load monitoring part) at the moment of each wave crest value and each wave trough value are measured sequentially and respectively and are respectively epsilon'115＝2429με，ε’125＝-728με，ε’135＝1735με，ε’215＝-1202με，ε’225＝2195με，ε’235＝-1098με，ε’315＝3152με，ε’325＝-767με，ε’335＝2275με，ε’415＝-1045με，ε’425＝1288με，ε’435＝-724με。
Step four, calculating the fatigue spectrum strain measurement value andrelative error eta between strain averages of static measurementskAnd then, after the calculation, the data are sent to the computer,
and if the requirements are met, the loading frequency of the formal fatigue test of the structure can be tested according to 5 wave blocks per minute.
The invention provides a method for determining the loading frequency of an airplane structure fatigue test, which is provided from the debugging angle of the airplane structure fatigue test aiming at the problem of determining the loading frequency of the fatigue load in the airplane structure fatigue test. Based on the characteristics of long test period, multiple loading points, high loading coordination difficulty, difficulty in determining the loading frequency of the fatigue load and the like in the fatigue test of the airplane structure, the invention provides the method for determining the proper loading frequency by firstly carrying out static strain measurement under various working conditions, then carrying out fatigue strain measurement on complete spectrum blocks under different frequencies, and finally calculating and judging the relative error between the fatigue strain measurement value and the static strain measurement value. The method has the advantages of correct theoretical basis, clear and simple implementation steps and clear engineering concept. The invention solves the problem that the fatigue loading frequency is difficult to determine in the airplane structure fatigue test.
Claims (2)
1. A method for determining the loading frequency of an aircraft structure fatigue test is characterized by comprising the following steps: step one, according to the sequence in the load spectrum arrangement, sequentially and respectively according to the static strain measurement requirement, measuring the strain value epsilon of each strain gage of the monitoring part of each wave crest and each wave trough under the 100% loadij1,2,3.. cndot.n; j is 1,2,3, the. Step two, repeating the measurement for 3 times according to the step one, and respectively calculating the average value of each strain measurement value
Wherein the content of the first and second substances,
t is the number of repeated measurements; step three, carrying out fatigue spectrum strain measurement; under the initially assumed loading spectrum-walking frequency, spectrum walking is carried out according to the sequence of the load spectrum, and strain values epsilon 'of the strain gauge are measured at each peak value and each trough value instantly'ijk1,2,3.. cndot.n; j 1,2,3.. said., M; 1,2,3.. said., Z; z is the assumed times corresponding to the loading spectrum-moving frequency of the initial assumption; step four, calculating the relative error eta between the fatigue walking spectrum strain measurement value and the static measurement strain average valuekJudgment of etakWhether or not to satisfy
If so, taking the initially assumed loading frequency as the loading frequency of the formal fatigue test of the structure; if not, returning to the third step, readjusting the loading frequency, and continuing to measure and judge until the requirements are met.
2. The method of claim 1, wherein the monitoring portion comprises a check portion and a load monitoring portion.
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| CN110704951B (en) * | 2019-09-29 | 2021-10-15 | 中国直升机设计研究所 | Helicopter tail section fatigue test load spectrum compilation method |
| CN112498737A (en) * | 2020-12-09 | 2021-03-16 | 中国航空工业集团公司沈阳飞机设计研究所 | Fatigue test method for light airplane |
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