CN114065397A - Vibration-resistant fatigue design method for secondary load-bearing structure of helicopter - Google Patents

Vibration-resistant fatigue design method for secondary load-bearing structure of helicopter Download PDF

Info

Publication number
CN114065397A
CN114065397A CN202111391807.9A CN202111391807A CN114065397A CN 114065397 A CN114065397 A CN 114065397A CN 202111391807 A CN202111391807 A CN 202111391807A CN 114065397 A CN114065397 A CN 114065397A
Authority
CN
China
Prior art keywords
frequency value
frequency
helicopter
excitation
vibration
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
CN202111391807.9A
Other languages
Chinese (zh)
Inventor
陈英华
李璨
马小艳
王影
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
China Helicopter Research and Development Institute
Original Assignee
China Helicopter Research and Development Institute
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by China Helicopter Research and Development Institute filed Critical China Helicopter Research and Development Institute
Priority to CN202111391807.9A priority Critical patent/CN114065397A/en
Publication of CN114065397A publication Critical patent/CN114065397A/en
Pending legal-status Critical Current

Links

Images

Classifications

    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/10—Geometric CAD
    • G06F30/15—Vehicle, aircraft or watercraft design
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/10—Geometric CAD
    • G06F30/17—Mechanical parametric or variational design
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/20—Design optimisation, verification or simulation
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
    • G06F2119/14—Force analysis or force optimisation, e.g. static or dynamic forces
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T90/00—Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation

Abstract

The invention provides a vibration-resistant fatigue design method for a secondary load-bearing structure of a helicopter, which comprises the following steps: applying vertical unit acceleration excitation to the installed platform to obtain a stress frequency response curve of the secondary bearing structural member; determining a first main resonance peak and a first frequency value corresponding to the first main resonance peak based on the frequency response curve, and determining a dangerous part based on the first frequency value; determining a fatigue limit value of the structural material based on an S-N curve of the structural material at the dangerous part; obtaining a maximum allowable transfer function based on the fatigue limit value and the helicopter vibration environment spectrum; the invention provides a vibration fatigue resistance design process and method for a secondary load-bearing structure of a helicopter, which are used for analyzing the vibration fatigue strength of a secondary load-bearing part in a vibration environment and optimizing the structure so as to ensure that the structure meets the requirements of strength and use.

Description

Vibration-resistant fatigue design method for secondary load-bearing structure of helicopter
Technical Field
The invention belongs to the technical field of helicopter structure strength tests, and particularly relates to a vibration fatigue resistance design method for a secondary load-bearing structure of a helicopter.
Background
With the increasing frequency of helicopter applications in recent years, in the practical use process, fatigue failure accidents caused by vibration of structures such as a fairing, a fuel pipeline, an equipment support and the like on the helicopter frequently occur, and the problem of durability of the vibration environment of a secondary bearing structure is more and more emphasized by people.
At present, when the strength of a helicopter is designed, respective standards and specifications of static strength, fatigue and dynamics specialties are formed, but independent and disjointed, the problem of vibration fatigue of a secondary bearing structure commonly existing on the helicopter is faced, the strength and the service life of the structure are difficult to predict and check only by adopting a conventional strength design method, and the relevant specifications of the vibration fatigue design are almost blank.
Disclosure of Invention
In view of the above technical problems, in a first aspect, the present invention provides a method for designing a secondary load-bearing structure of a helicopter with vibration fatigue resistance, where the method includes:
applying vertical unit acceleration excitation to the installed platform to obtain a stress frequency response curve of the secondary bearing structural member;
determining a first main resonance peak and a first frequency value corresponding to the first main resonance peak based on the frequency response curve, and determining a dangerous part based on the first frequency value;
determining a fatigue limit value of the structural material based on an S-N curve of the structural material at the dangerous part;
and obtaining the maximum allowable transfer function based on the fatigue limit value and the vibration environment spectrum of the helicopter.
Preferably, before the vertical unit acceleration excitation is applied to the installed platform to obtain the stress frequency response curve of the secondary load-bearing structural member, the method further comprises:
establishing a dynamic model based on a secondary bearing structural member and an installed boundary condition;
and determining the direction of basic excitation based on the installed position of the secondary bearing structure.
Preferably, the kinetic model comprises a hazard site structure and connection simulation; the directions of the fundamental excitation include a vertical excitation, a lateral excitation, and a heading excitation.
Preferably, after obtaining the maximum allowable transfer function based on the fatigue limit value and the spectrum of the helicopter vibration environment, the method further comprises:
obtaining a second frequency value and a third frequency value based on the maximum allowable transfer function and the node dynamic stress frequency response curve of the dangerous part; wherein the first frequency value is between the second frequency value and the third frequency value.
Preferably, after obtaining the second frequency value and the third frequency value based on the maximum allowable transfer function and the node dynamic stress frequency response curve of the dangerous portion, the method further includes:
defining the safety coefficient of the secondary force-bearing structure based on the minimum frequency value and the fourth frequency value; wherein the minimum frequency value is the smallest of the second and third frequency values, and the fourth frequency value is the frequency value closest to the first frequency value in a periodic excitation in the spectrum of the helicopter vibratory environment.
Preferably, the determining a dangerous site based on the first frequency includes:
determining a maximum stress position based on the frequency response stress cloud map of the first frequency; wherein the maximum stress location corresponds to the hazard site.
Preferably, the method further comprises:
and applying vertical unit acceleration excitation to the installed platform to obtain the acceleration of the initial secondary bearing structural member.
Preferably, the obtaining of the maximum allowable transfer function based on the fatigue limit value and the helicopter vibration environment spectrum comprises:
determining a fourth frequency which is smaller than the first frequency value and closest to the first frequency value based on the excitation frequency value in the vibration environment spectrum of the helicopter;
assuming that the amplitude value corresponding to the fourth frequency value in the spectrum of the vibration environment of the helicopter is Ai；
Calculating a maximum allowable transfer function based on the material fatigue limit and the helicopter vibration environment spectrum by:
Figure BDA0003364821180000021
wherein, ω isiIs a first frequency value, S-1Is the material fatigue limit.
The invention has the beneficial technical effects that:
the invention provides a vibration fatigue resistance design process and method for a secondary load-bearing structure of a helicopter, which are used for analyzing the vibration fatigue strength of a secondary load-bearing part in a vibration environment and optimizing the structure so as to ensure that the structure meets the requirements of strength and use.
Drawings
FIG. 1 is a flow chart of a design method provided by an embodiment of the present invention;
FIG. 2 is an acceleration frequency response curve provided by an embodiment of the present invention;
FIG. 3 is a schematic diagram of a hazardous location identification provided by an embodiment of the present invention;
FIG. 4 is a diagram illustrating a minimum natural frequency solution provided by an embodiment of the present invention;
FIG. 5 is a modified comparative view of a seat assembly provided by an embodiment of the present invention;
wherein, 1-gasket and 2-support.
Detailed Description
Referring to fig. 1-4, the present invention provides a new design method for evaluating the durability life of a secondary helicopter load-bearing structure in a vibration fatigue environment, which can be used for checking the vibration fatigue strength of the helicopter structure and design basis.
The invention provides a method for designing vibration fatigue of a secondary load-bearing structure of a helicopter, which aims to solve the problem of design specification or standard blank of the vibration fatigue strength of the secondary load-bearing structure of the helicopter.
The technical scheme adopted by the invention is as follows: the method for designing the secondary load-bearing structure vibration fatigue of the helicopter specifically comprises the following steps:
the precondition assumption conditions are as follows:
1) the structural damping is kept unchanged when the natural frequency of the structure is changed in a small range;
2) the vibration of the structure is mainly caused by fixed-frequency excitation, but not random excitation;
designing input conditions:
1) a spectrum of the vibration environment;
2) an initial structural member;
3) installing boundary conditions;
the design method comprises the following steps:
the method comprises the following steps: kinetic modeling
Establishing a refined dynamic model based on an initial secondary bearing structural member and an installed boundary condition, wherein the model is required to comprise a possibly existing dangerous part structure and a possibly existing connecting piece simulation, and for a small connecting piece, a connecting unit simulation can be adopted, and then the problem of non-uniform grid size is avoided by a method of extracting a connecting load and additionally establishing a local detail model of the connecting piece.
Then, the direction of basic excitation is determined according to the installation position of the structure, the subsequent steps are carried out according to three directions, and the following vertical excitation is taken as an example for explanation:
step two: dynamic stress frequency response function solving
And (3) applying vertical unit acceleration excitation on the basis by adopting a large-mass method, solving the dynamic response of the secondary load-bearing structure with the boundary condition, and obtaining a frequency response curve of the acceleration or the stress of the structure, as shown in the attached figure 2.
Step three: identification of dangerous part
Searching the first main resonance peak from the frequency response curve of the previous step, and setting the corresponding frequency as omega1Looking at the first order natural frequency ω1To determine the location of maximum stress or hazard, as shown in fig. 3.
Step four: fatigue limit of material
Determining the fatigue limit value S of the material according to the S-N curve of the dangerous part bit unit material-1The limit value is used as the design basis of the infinite life of the structure.
Step five: maximum allowable transfer function
Finding out the value smaller than omega according to the excitation frequency value in the vibration environment spectrum1And the nearest frequency ωiAssuming that the amplitude of the frequency in the environmental spectrum is Ai. Limit of fatigue S of material from previous step-1And a spectrum of the vibration environment, the maximum allowable transfer function can be calculated:
Figure BDA0003364821180000041
step six: minimum natural frequency
Selecting a dangerous part or a node near the maximum stress in the third step, reading a dynamic stress frequency response curve of the node, setting the dynamic stress frequency response curve as H (x), and enabling the node to be in order
H(x)＝Hmax(ωi)
Two frequency values can be solved:
x＝ωuor ωd
Wherein the three frequency values satisfy the relationship: omegau>ω1>ωdAs shown in fig. 4. To this end, the minimum natural frequency ω required for structural design can be givend。
Step seven: definition of safety margin
A safety margin parameter for structural vibration fatigue can be defined:
Figure BDA0003364821180000051
by setting the minimum margin value, the structural rigidity can be designed, and under the general condition, a minimum safety factor of 1.2 is recommended, namely when eta is greater than 1.2, the structural strength meets the vibration fatigue design.
Step eight: durability test verification
Because the secondary bearing structure generally has a nonlinear contact boundary, the rigidity value is gradually reduced in the using process, the natural frequency is correspondingly reduced, the method can be adopted to request the actually measured natural frequency value of the installed structure for the period limitation of replacement or structure reinforcement, but the rigidity reduction speed has larger accidental factors and nonlinearity, so the process cannot pass simulation, and the durability life of the structure is finally confirmed by adopting a vibration fatigue test method.
The invention provides a vibration fatigue resistance design process and method for a secondary load-bearing structure of a helicopter, which are used for analyzing the vibration fatigue strength of a secondary load-bearing part in a vibration environment and optimizing the structure so as to ensure that the structure meets the requirements of strength and use. Meanwhile, the invention provides a dynamic safety margin defining method which can be used as a judgment basis for structural vibration fatigue durability and maintenance period based on the actual measurement modal result of the installed parts.
In the embodiment of the present application, please refer to fig. 5, which illustrates an example of a lever system support of a certain type of machine, and the above analysis method is used to analyze and structurally optimize the vibration fatigue strength of the lever system support in the vibration environment of a transmission system, where after optimization, the safety margin η is 1.3, and the optimization scheme is shown in fig. 5.

Claims (8)

1. A method for designing vibration and fatigue resistance of a secondary load-bearing structure of a helicopter is characterized by comprising the following steps:
applying vertical unit acceleration excitation to the installed platform to obtain a stress frequency response curve of the secondary bearing structural member;
determining a first main resonance peak and a first frequency value corresponding to the first main resonance peak based on the frequency response curve, and determining a dangerous part based on the first frequency value;
determining a fatigue limit value of the structural material based on an S-N curve of the structural material at the dangerous part;
and obtaining the maximum allowable transfer function based on the fatigue limit value and the vibration environment spectrum of the helicopter.
2. The method of claim 1, wherein before applying the vertical unit acceleration excitation to the installed platform to obtain the stress frequency response curve of the secondary load-bearing structural member, the method further comprises:
establishing a dynamic model based on a secondary bearing structural member and an installed boundary condition;
and determining the direction of basic excitation based on the installed position of the secondary bearing structure.
3. The method of claim 2, wherein the kinetic model comprises a hazard site structure and connection simulation; the directions of the fundamental excitation include a vertical excitation, a lateral excitation, and a heading excitation.
4. The method of claim 1, wherein after obtaining the maximum allowable transfer function based on the fatigue limit and the spectrum of the helicopter vibration environment, the method further comprises:
obtaining a second frequency value and a third frequency value based on the maximum allowable transfer function and the node dynamic stress frequency response curve of the dangerous part; wherein the first frequency value is between the second frequency value and the third frequency value.
5. The method of claim 4, wherein after obtaining the second frequency value and the third frequency value based on the maximum allowable transfer function and the nodal dynamic stress frequency response curve of the dangerous portion, the method further comprises:
defining the safety coefficient of the secondary force-bearing structure based on the minimum frequency value and the fourth frequency value; wherein the minimum frequency value is the smallest of the second and third frequency values, and the fourth frequency value is the frequency value closest to the first frequency value in a periodic excitation in the spectrum of the helicopter vibratory environment.
6. The method of claim 1, wherein determining a hazard based on the first frequency comprises:
determining a maximum stress position based on the frequency response stress cloud map of the first frequency; wherein the maximum stress location corresponds to the hazard site.
7. The method of claim 1, further comprising:
and applying vertical unit acceleration excitation to the installed platform to obtain the acceleration of the initial secondary bearing structural member.
8. The method of claim 1, wherein said deriving a maximum allowable transfer function based on said fatigue limit and a helicopter vibration environment spectrum comprises:
determining a fourth frequency which is smaller than the first frequency value and closest to the first frequency value based on the excitation frequency value in the vibration environment spectrum of the helicopter;
assuming that the amplitude value corresponding to the fourth frequency value in the spectrum of the vibration environment of the helicopter is Ai；
Calculating a maximum allowable transfer function based on the material fatigue limit and the helicopter vibration environment spectrum by:
Figure FDA0003364821170000021
wherein, ω isiIs a first frequency value, S-1Is the material fatigue limit.
CN202111391807.9A 2021-11-19 2021-11-19 Vibration-resistant fatigue design method for secondary load-bearing structure of helicopter Pending CN114065397A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202111391807.9A CN114065397A (en) 2021-11-19 2021-11-19 Vibration-resistant fatigue design method for secondary load-bearing structure of helicopter

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202111391807.9A CN114065397A (en) 2021-11-19 2021-11-19 Vibration-resistant fatigue design method for secondary load-bearing structure of helicopter

Publications (1)

Publication Number Publication Date
CN114065397A true CN114065397A (en) 2022-02-18

Family

ID=80279657

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202111391807.9A Pending CN114065397A (en) 2021-11-19 2021-11-19 Vibration-resistant fatigue design method for secondary load-bearing structure of helicopter

Country Status (1)

Country Link
CN (1) CN114065397A (en)

Similar Documents

Publication Publication Date Title
CN107145663B (en) Multi-objective optimization design method for wheels
Jonkman et al. Offshore code comparison collaboration (OC3) for IEA Wind Task 23 offshore wind technology and deployment
CN107742045B (en) Finite element calculation method for strength of hoisting tool of wind generating set
Mashayekhi et al. Three‐dimensional multiscale finite element models for in‐service performance assessment of bridges
Lee et al. Optimization of resonance‐type fatigue testing for a full‐scale wind turbine blade
Ferreira et al. A comparative study of automotive system fatigue models processed in the time and frequency domain
CN116306179A (en) Load screening method and system for impact damage evaluation of airborne store lifting
CN113158318B (en) Method for designing bearing capacity reinforcement for normal section of shear wall with special-shaped end columns
CN114065397A (en) Vibration-resistant fatigue design method for secondary load-bearing structure of helicopter
Morgan Shock & vibration using ANSYS mechanical
Balabanov et al. Influence of Natural Vibration Frequencies in the Analysis on Vibration Resistance of Steel Supporting Parts of a Car
CN109388907B (en) Design method of shafting with preset longitudinal vibration dynamic flexibility
CN107766621B (en) Nuclear power station overhead HDPE (high-density polyethylene) pipeline functionality verification method and system
Shen et al. Rapid evaluation of structural soundness of steel frames using a coupling coefficient (CC)‐based method
Davalos et al. Reduction of Stresses and Mass of an Engine Rubber Mount Subject to Mechanical Vibrations.
Hsu et al. Prediction of fatigue failures of aluminum disc wheels using the failure probability contour based on historical test data
Kolios et al. Reliability based design of novel offshore structures
Patil et al. Thermo-mechanical analysis of crankcase
Cervenka et al. Safety assessment in fracture analysis of concrete structures
Hosch et al. Operational Post Deformation of Cantilever Sign Support Structures from Truck-Induced Wind Gusts
Tian et al. Reproduction of the wind and earthquake coupled effect on a wind turbine tower in a shaking-table substructure test
Pototzky Roll damping derivatives from generalized lifting-surface theory and wind tunnel forced-oscillation tests
CN109630590A (en) A kind of tower vibrationproof viscous damper
CN114386201B (en) Vibration characteristic analysis method of bearing
Belver et al. Performance of a TMD to Mitigate Wind-Induced Interference Effects between Two Industrial Chimneys. Actuators 2021, 10, 12

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination