CN109374450A - It is a kind of to consider that the hard object damage of high and low all tired blade and blade basin blade back crack types determine method with the limit - Google Patents

It is a kind of to consider that the hard object damage of high and low all tired blade and blade basin blade back crack types determine method with the limit Download PDF

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CN109374450A
CN109374450A CN201811115062.1A CN201811115062A CN109374450A CN 109374450 A CN109374450 A CN 109374450A CN 201811115062 A CN201811115062 A CN 201811115062A CN 109374450 A CN109374450 A CN 109374450A
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blade
crack
stress
point
low
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CN109374450B (en
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宋迎东
贾旭
胡绪腾
吴娜
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Nanjing University of Aeronautics and Astronautics
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Nanjing University of Aeronautics and Astronautics
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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
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0001—Type of application of the stress
    • G01N2203/0005—Repeated or cyclic
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0058—Kind of property studied
    • G01N2203/006—Crack, flaws, fracture or rupture
    • G01N2203/0062—Crack or flaws
    • G01N2203/0066—Propagation of crack
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0058—Kind of property studied
    • G01N2203/0069—Fatigue, creep, strain-stress relations or elastic constants
    • G01N2203/0073—Fatigue

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Abstract

It is high that the invention discloses a kind of considerations, the hard object damage of the blade and blade basin blade back crack type of low-cycle fatigue can determine method with the limit, high cycles fatigue load and low-cycle fatigue load are extracted from high/low all combined loads that blade is born first, a series of hard object crack damage of the relevant tearing/crack type of stress ratio under high cycles fatigue load and low-cycle fatigue load is established respectively does not extend equivalent curve, then the static stress and dynamic stress on leaf basin blade back various point locations are determined by finite element method, crack size corresponding to the equivalent curve is determined in the position that crackle does not extend in equivalent curve finally by static stress and dynamic stress is compared, the available limit of the hard object damage of tearing/crack type as at the blade and blade basin blade back point.The present invention not only proposes one kind, and simply, effectively hard object damages the method that can be determined with the limit, but also is directed to the hard object of blade and blade basin blade back tearing/crack type and damages the available limit system constant current journey for foring a kind of standardization.

Description

A kind of hard object damage of blade and blade basin blade back crack type considering high and low week fatigue is available The limit determines method
Technical field
The present invention relates to a kind of hard object damages of the blade and blade basin blade back crack type for considering high and low week fatigue to be determined with the limit Method belongs to the hard object damage tolerance design of blade of aviation engine and maintenance area.
Background technique
The hard object such as metal, fragment, gravel, stone enters engine air circulation road and high-speed rotating blade along with air-flow The impact injury to be formed that collides is the one of the major reasons for aggravating blade fatigue failure.Although there has been proposed the races of such as aircraft The foreign object damages precautionary measures such as the cleaning of road foreign object, the inspection of ground crew's maintenance tool and control, but hard object damage can not always be kept away Exempt from.
For inevitable hard object damage problem, although engine designer makes blade be provided with certain hard object damage Tolerance ability, but be also required to provide the servicing manual with hard object damaged blade in the reseach of engine later period for user simultaneously, it is After user provides necessary suggestion in operation and maintenance engine blade, such as hard object damage occurs for blade, how to judge hard Whether object damaged blade is available (being excused from a college course).Currently, the key dimension for judging hard object injury severity score is lesion depths, engine The available limit after hard object damage often occurs as blade using permitted maximum lesion depths in servicing manual, and passes through It determines that reasonably the available limit is to reach under the premise of guaranteeing safety and performance, reduces blade and a degree of foreign object is occurring The number of detachable maintaining and replacement after damage improves economy and Combat readiness.
Engine Company, which does not formulate hard object damage rear blade, at present can use the normalization procedure of the limit, newly set in the past The available limit of the engine blade of meter is often based upon the operation and maintenance experience of old money engine, however as blade design skill The continuous development of art, novel vane structure (such as integral blade disk, hollow blade) allow this empirical extrapolation mode to be faced with Huge challenge.
The hard object damage of tearing/crack type is the more serious damage that blade of aviation engine leaf basin blade back is often subjected to, this It is tired to propose a kind of consideration high and low week in order to provide the available limit system constant current journey of reasonable standard to such hard object damage for invention The hard object damage of the blade and blade basin blade back crack type of labor can determine method with the limit.
Summary of the invention
The object of the present invention is to provide a kind of hard object damage of the blade and blade basin blade back crack type for considering high and low week fatigue is available The limit determines method, to solve to lack the available limit system constant current journey of reasonable standard for the hard object damage of tearing/crack type at present The problem of.
To achieve the above object, the technical solution adopted by the present invention are as follows:
It is a kind of to consider that the hard object damage of high and low all tired blade and blade basin blade back crack types determine method with the limit, including Following steps:
(1) the high/low all Combined Fatigue Loads born from the leaf basin of blade and blade back each point extract the height that may occur Cyclic fatigue load and low-cycle fatigue load；
(2) the crack growth threshold data according to blade material under different stress ratios, establish that stress ratio is relevant to be split Line crack threshold value model；
(3) tearing in the leaf basin and blade back of blade/crack type damage is set as I type surface half-ellipse crack, it is oval Crack depth half shaft length a is that tearing/crack type damage depth capacity d, half axial length b of elliptical crack surface are 1.5 times of a, Establish the stress intensity factor calculation method of the surface half-ellipse crack；
(4) the crackle not extended model of high cycle fatigue load under the conditions of different stress ratios, low cycle fatigue loading is established respectively, And it draws crackle under different crack depths a and does not extend equivalent curve figure；
(5) static stress and dynamic stress of blade and blade basin blade back each point are obtained by finite element method；
(6) equivalence song is determined in the position that crackle does not extend in equivalent curve by comparing static stress and dynamic stress The available limit of the hard object damage of crackle/tearing mode at crack size a corresponding to line, as blade and blade basin the blade back point.
In the step (1), blade low frequency centrifugal force is followed when high/low all combined loads of blade refer to engine work Low frequency centrifugal force cyclic loading in blade is denoted as low-cycle fatigue load, by leaf by the interaction of ring load and high-frequency vibration load Piece medium-high frequency oscillating load is denoted as high cycles fatigue load, determines that the leaf basin of blade and blade back each point may by load spectrum analysis The high cycles fatigue load and low-cycle fatigue loading of appearance.
In the step (2), crack growth threshold is indicated using stress intensity factor range Δ K, wherein working as stress When than R > 0, Δ K=Kmax-Kmin, and Kmin≠ 0, as stress ratio R≤0, Δ K=Kmax-Kmin, and Kmin=0；Crack propagation door Threshold value Δ KthIt is expressed as the function of stress ratio R.
In the step (3), the blade with I type surface half-ellipse crack is considered as limited thickness, unlimited width, unlimited The semiellipse crackle body Model of length, the load born on crack surface is using power function distributed stress expression formula, it may be assumed that
Wherein, σ (x) is the stress distribution on crack surface, and a is crack length, and x is the coordinate on direction of crack propagation, Its coordinate origin is the intersection point of single side crack and leading edge point, σiFor multinomial coefficient, i is exponent of polynomial, item number n≤7；With tear Split/the crack surface stress distribution born of the big plate with I type surface half-ellipse crack of crack type blade equivalence is uniformly distributed point Cloth, i.e. n=0, stress intensity factor calculation method use general weight-function method；
Stress intensity factor calculation expression when the above power function distributed stress is born on surface half-ellipse crack crack surface Formula are as follows:
Wherein (x is a) weight function of cracks in body to m, and stress intensity factor maximum point is past for surface half-ellipse crack Past is crack front deepest point A point or crack front surface point B point；
The general weight function of surface half-ellipse crack leading edge deepest point A point are as follows:
The general weight function of surface half-ellipse crack leading edge surface point B point are as follows:
As σ (x)=σ0When, the stress intensity factor implied expression formula of A point and B point are as follows:
Wherein, K is stress intensity factor, M1A、M2A、M3A、M1B、M2B、M3BFor general weight function coefficient, π is pi, σ0 For the uniform stress born on crack surface.
It is Δ K that the crackle of high cycle fatigue load, which does not extend criterion, in the step (4), under the conditions of different stress ratiosHCF= ΔKth(RHCF), crackle does not extend equivalent curve model are as follows:
As stress ratio -1 < R < 0,
As 0≤R of stress ratio < 1,
It is Δ K that crackle under low cycle fatigue loading, which does not extend criterion,LCF=Δ Kth(RLCF), stress ratio RLCF=-1, then Crackle does not extend equivalent curve model are as follows:
Wherein, Δ KHCFFor the stress intensity factor range under HCF load cycle, Δ KLCFFor under low-cycle fatigue load Stress intensity factor range；RHCFFor the stress ratio of HCF load, RLCFFor the stress ratio of LCF load；FnFor geometric corrections coefficient； σdynFor dynamic stress, σstaFor static stress, Δ σth(RHCF) and Δ σth(RLCF) it is threshold value stress；
It is static stress ordinate is dynamic stress that crackle, which does not extend equivalent curve figure abscissa,.
In the step (5), the leaf basin of blade and the static stress and dynamic stress of blade back each point use unit Von- Mises equivalent stress indicates, represents the unit size of leaf basin blade back point as 1mm.
In the step (6), takes and wherein do not extend what equivalent curve determined by the corresponding crackle of high cycle fatigue load Crack size and by low cycle fatigue loading determine crack size minimum value as the tearing at the blade and blade basin blade back point/ The available limit of the hard object damage of crack type.
The utility model has the advantages that the present invention is tearing/crack type that blade of aviation engine use process middle period basin blade back is often subjected to The available limit that hard object damage provides a kind of reasonable standard determines method and process.The present invention considers blade and damages by hard object The typical failure mode occurred after wound: high cycle fatigue and low-cycle fatigue, using the crackle being simple and efficient, extension principle is not established The crackle of blade does not extend equivalent curve figure, and the limit can be used by proposing tearing in formulation blade and blade basin blade back/crack type damage Standard step.
Detailed description of the invention
Fig. 1 is high/low all composite fatigue schematic diagrames；
Fig. 2 is low-cycle fatigue and high cycle fatigue schematic diagram；
Fig. 3 a- Fig. 3 e is the HCF and LCF loading that blade and blade basin blade back each point is likely to occur；
Fig. 4 is the crack growth threshold data and model of blade common used material TC4 titanium alloy；
Fig. 5 is that blade and blade basin blade back tearing/crack type equivalent damage is reduced to I type surface half-ellipse crack；
Fig. 6 is that crackle does not extend equivalent curve schematic diagram under HCF load；
Fig. 7 is that crackle does not extend equivalent curve figure under TC4 titanium alloy material HCF load；
Fig. 8 is that crackle does not extend equivalent curve schematic diagram under LCF load；
Fig. 9 is that crackle does not extend equivalent curve figure under TC4 titanium alloy material HCF load；
Figure 10 is blade of aviation engine and grid dividing form；
Figure 11 is the stable state stress distribution that Von-mises stress indicates；
Figure 12 is the first-order modal vibration stress that Von-mises stress indicates；
Figure 13 is the second-order modal vibration stress that Von-mises stress indicates；
Figure 14 is not extend equivalent curve figure by crackle to determine that blade and blade basin blade back can use limit schematic diagram；
Figure 15 is the available Limit Distribution that first-order modal vibrates the hard object damage of lower blade and blade basin blade back tearing/crack type；
Figure 16 is that second-order modal vibrates the available Limit Distribution of lower blade and blade basin blade back tearing/crack type damage.
Specific embodiment
Further explanation is done to the present invention with reference to the accompanying drawings and embodiments.
Embodiment
It is a kind of to consider that the hard object damage of high and low all tired blade and blade basin blade back crack types determine method with the limit, including Following steps:
(1) the high/low all Combined Fatigue Loads born from the leaf basin of blade and blade back each point extract the height that may occur Cyclic fatigue load and low-cycle fatigue load.Wherein, high cycles fatigue load, that is, high cycle fatigue load High cycle Fatigue, abbreviation HCF, low-cycle fatigue load, that is, low cycle fatigue loading low cycle fatigue, abbreviation LCF.
Blade low frequency centrifugal force cyclic loading and high frequency vibrating when high/low all combined loads of blade refer to engine work The interaction of dynamic loading, as shown in Figure 1.Centrifugal force cyclic loading in blade is denoted as low-cycle fatigue load by the present invention, i.e., low All fatigue loads will be more than that the high-frequency vibration load of 1KHz is denoted as high cycles fatigue load, i.e. high cycle fatigue load in blade, such as Shown in Fig. 2.The HCF load and LCF loading such as Fig. 3 that blade and blade basin blade back each point is likely to occur are determined by load spectrum analysis It is shown.
(2) the crack growth threshold data according to blade material under different stress ratios, establish that stress ratio is relevant to be split Line crack threshold value model.The crack growth threshold of blade material is indicated using stress intensity factor range Δ K in the present invention, Wherein as stress ratio R > 0, Δ K=Kmax-Kmin, and Kmin≠ 0, as stress ratio R≤0, Δ K=Kmax-Kmin, and Kmin=0. Crack growth threshold Δ KthIt is expressed as the function of stress ratio R.It is common using engine fan/compressor blade in the present embodiment For material TC4 titanium alloy material, crack propagation model Value Data and curve are as shown in Figure 4.The crackle of TC4 titanium alloy expands Open up threshold value model are as follows:
As 0≤R < 1:
As -1≤R < 0:
Wherein,The effective stress intensity range when for stress ratio R=0,A0= 0.00729、A1=1.0108, A2=-0.3959, A3=-0.10356 is coefficient,Stress intensity when for stress ratio R=0 Factor range,
(3) tearing in blade and blade basin blade back/crack type damage is assumed to be I type surface half-ellipse crack, elliptical crack Depth half shaft length a is that tearing/crack type damage depth capacity d, half axial length b of elliptical crack surface are 1.5 times of a, is established The stress intensity factor calculation method of the surface half-ellipse crack；Blade with I type surface half-ellipse crack is considered as limited thickness Semiellipse crackle body Model such as Fig. 5 of degree, unlimited width, indefinite length, the load born on crack surface is using power function Distributed stress expression formula, it may be assumed that
Wherein, σ (x) is the stress distribution on crack surface, and a is crack length, and x is the coordinate on direction of crack propagation, Its coordinate origin is the intersection point of single side crack and leading edge point, σiFor multinomial coefficient, i is exponent of polynomial, item number n≤7.With tear Split/the crack surface stress distribution born of the big plate with I type surface half-ellipse crack of crack type blade equivalence is uniformly distributed point Cloth, i.e. n=0, stress intensity factor calculation method use general weight-function method.
Stress intensity factor calculation expression when the above power function distributed stress is born on surface half-ellipse crack crack surface Formula are as follows:
Wherein (x is a) weight function of cracks in body to m, and stress intensity factor maximum point is past for surface half-ellipse crack Past is crack front deepest point A point or crack front surface point B point；
The general weight function of surface half-ellipse crack leading edge deepest point A point are as follows:
The general weight function of surface half-ellipse crack leading edge surface point B point are as follows:
As σ (x)=σ0When, the stress intensity factor implied expression formula of A point and B point are as follows:
Wherein, K is stress intensity factor, M1A、M2A、M3A、M1B、M2B、M3BFor general weight function coefficient, π is pi, σ0 For the uniform stress born on crack surface.
(4) the crackle not extended model of high cycle fatigue load under the conditions of different stress ratios, low cycle fatigue loading is established respectively, And it draws crackle under different crack lengths and does not extend equivalent curve figure.The crackle of high cycle fatigue load is not under the conditions of different stress ratios Extension criterion is Δ KHCF=Δ Kth(RHCF), crackle does not extend equivalent curve model are as follows:
As stress ratio -1 < R < 0,
As 0≤R of stress ratio < 1,
When stress ratio R is larger, in fact it could happen that stress intensity factor range is unlikely to extend crackle, but maximum is answered Power intensity factor KmaxReach the fracture toughness of material and causes transient state crack propagation to fracture.Crackle does not extend equivalent song at this time Line should supplement boundary condition, i.e. Kmax=KIC.Therefore, not extend equivalent curve schematic diagram as shown in Figure 6 for crackle under HCF load. It is as shown in Figure 7 not extend equivalent curve figure for crackle under TC4 titanium alloy material HCF load.
It is Δ K that crackle under low cycle fatigue loading, which does not extend criterion,LCF=Δ Kth(RLCF), stress ratio RLCF=-1, then Crackle does not extend equivalent curve model are as follows:
Wherein, Δ KHCFFor the stress intensity factor range under HCF load cycle, Δ KLCFFor under low-cycle fatigue load Stress intensity factor range；RHCFFor the stress ratio of HCF load, RLCFFor the stress ratio of LCF load；FnFor geometric corrections coefficient； σdynFor dynamic stress, σstaFor static stress, Δ σth(RHCF) and Δ σth(RLCF) it is threshold value stress.Crackle is not under LCF load Equivalent curve schematic diagram is extended as shown in figure 8, crackle does not extend equivalent curve figure such as Fig. 9 institute under TC4 titanium alloy material LCF load Show.
It is static stress ordinate is dynamic stress that crackle, which does not extend equivalent curve figure abscissa,.
(5) static stress and dynamic stress of blade and blade basin blade back each point are obtained by finite element method.Leaf The static stress and dynamic stress of piece leaf basin blade back each point are indicated using unit Von-mises equivalent stress, represent leaf basin blade back The unit size of point is 1mm.In the present embodiment, certain type blade of aviation engine and its grid dividing form are as shown in Figure 10.Hair Motivation blade static stress in practical work process determines by working speed, therefore can be quick by finite element method Accurately obtain.However, the calculating process of actual vibration stress is not only sufficiently complex in blade and computational accuracy is difficult to ensure.Institute With the calculation process in order to illustrate the method for the present invention, using blade 1 rank, 2 occur respectively for the oscillating load of blade in the present embodiment Von-mises effective stress when rank modal vibration and blade tip vibration displacement are 5mm indicates.The static state of blade is answered in the present embodiment Power distribution is as shown in figure 11.The blade first-order modal vibration stress distribution such as Figure 12 indicated using Von-mises stress, is used The blade second-order modal stress distribution that Von-mises stress indicates is as shown in figure 13.
(6) equivalence song is determined in the position that crackle does not extend in equivalent curve by comparing static stress and dynamic stress Crack size corresponding to line takes and does not wherein extend the crackle ruler that equivalent curve determines by the corresponding crackle of high cycle fatigue load Very little and minimum value by the determining crack size of low cycle fatigue loading is as crackle/tearing mode at the blade and blade basin blade back point The available limit of hard object damage.Wherein, equivalent curve figure is not extended by crackle under HCF load and determines that blade and blade basin blade back is available Limit process is as shown in figure 14.
First-order modal in the present embodiment can be obtained by above 6 steps and vibrate lower blade and blade basin blade back tearing/crack type Available Limit Distribution such as Figure 15 of hard object damage, second-order modal vibrates the hard object damage of lower blade and blade basin blade back tearing/crack type can It is as shown in figure 16 with Limit Distribution.
Though the present invention disclosed as above with preferred embodiment, the example be not it is for the purpose of limiting the invention, it is any to be familiar with this Those skilled in the art can also make several improvements and modifications without departing from the spirit and scope of the invention, these improvements and modifications It should be regarded as protection scope of the present invention.

Claims (7)

1. a kind of hard object damage of blade and blade basin blade back crack type for considering high and low week fatigue can determine method, feature with the limit It is: includes the following steps:
(1) the high/low all Combined Fatigue Loads born from the leaf basin of blade and blade back each point extract the high circulation that may occur Fatigue load and low-cycle fatigue load；
(2) the crack growth threshold data according to blade material under different stress ratios are established the relevant crackle of stress ratio and are expanded Open up threshold value model；
(3) tearing in the leaf basin and blade back of blade/crack type damage is set as I type surface half-ellipse crack, elliptical crack Depth half shaft length a is that tearing/crack type damage depth capacity d, half axial length b of elliptical crack surface are 1.5 times of a, is established The stress intensity factor calculation method of the surface half-ellipse crack；
(4) the crackle not extended model of high cycle fatigue load under the conditions of different stress ratios, low cycle fatigue loading is established respectively, and is drawn Crackle does not extend equivalent curve figure under different crack depths a processed；
(5) static stress and dynamic stress of blade and blade basin blade back each point are obtained by finite element method；
(6) the equivalent curve institute is determined in the position that crackle does not extend in equivalent curve by comparing static stress and dynamic stress The available limit of the hard object damage of crackle/tearing mode at corresponding crack size a, as blade and blade basin the blade back point.
2. the blade and blade basin blade back crack type hard object damage according to claim 1 for considering high and low week fatigue can use the limit Determine method, it is characterised in that: in the step (1), blade when high/low all combined loads of blade refer to engine work It is tired to be denoted as low circulation by the interaction of low frequency centrifugal force cyclic loading and high-frequency vibration load for low frequency centrifugal force cyclic loading in blade Blade medium-high frequency oscillating load is denoted as high cycles fatigue load by labor load, by load spectrum analysis determine blade leaf basin and The high cycles fatigue load and low-cycle fatigue loading that blade back each point is likely to occur.
3. the blade and blade basin blade back crack type hard object damage according to claim 1 for considering high and low week fatigue can use the limit Determine method, it is characterised in that: in the step (2), crack growth threshold uses stress intensity factor range Δ K table Show, wherein as stress ratio R > 0, Δ K=Kmax-Kmin, and Kmin≠ 0, as stress ratio R≤0, Δ K=Kmax-Kmin, and Kmin =0；Crack growth threshold Δ KthIt is expressed as the function of stress ratio R.
4. the blade and blade basin blade back crack type hard object damage according to claim 1 for considering high and low week fatigue can use the limit Determine method, it is characterised in that: in the step (3), with I type surface half-ellipse crack blade be considered as limited thickness, The semiellipse crackle body Model of unlimited width, indefinite length, the load born on crack surface is using power function distributed stress Expression formula, it may be assumed that
Wherein, σ (x) is the stress distribution on crack surface, and a is crack length, and x is the coordinate on direction of crack propagation, is sat Mark the intersection point that origin is single side crack and leading edge point, σiFor multinomial coefficient, i is exponent of polynomial, item number n≤7；With tearing/ The crack surface stress distribution that the big plate with I type surface half-ellipse crack of crack type blade equivalence is born is uniformly distributed distribution, That is n=0, stress intensity factor calculation method use general weight-function method；
Stress intensity factor calculation expression when the above power function distributed stress is born on surface half-ellipse crack crack surface are as follows:
Wherein (x is a) weight function of cracks in body to m, and stress intensity factor maximum point is often for surface half-ellipse crack Crack front deepest point A point or crack front surface point B point；
The general weight function of surface half-ellipse crack leading edge deepest point A point are as follows:
The general weight function of surface half-ellipse crack leading edge surface point B point are as follows:
As σ (x)=σ0When, the stress intensity factor implied expression formula of A point and B point are as follows:
Wherein, K is stress intensity factor, M1A、M2A、M3A、M1B、M2B、M3BFor general weight function coefficient, π is pi, σ0To split The uniform stress born on line face.
5. the blade and blade basin blade back crack type hard object damage according to claim 1 for considering high and low week fatigue can use the limit Determine method, it is characterised in that: in the step (4), the crackle of high cycle fatigue load does not extend under the conditions of different stress ratios Criterion is Δ KHCF=Δ Kth(RHCF), crackle does not extend equivalent curve model are as follows:
As stress ratio -1 < R < 0,
As 0≤R of stress ratio < 1,
It is Δ K that crackle under low cycle fatigue loading, which does not extend criterion,LCF=Δ Kth(RLCF), stress ratio RLCF=-1, then crackle Equivalent curve model is not extended are as follows:
Wherein, Δ KHCFFor the stress intensity factor range under HCF load cycle, Δ KLCFFor the stress under low-cycle fatigue load Intensity factor range；RHCFFor the stress ratio of HCF load, RLCFFor the stress ratio of LCF load；FnFor geometric corrections coefficient；σdynFor Dynamic stress, σstaFor static stress, Δ σth(RHCF) and Δ σth(RLCF) it is threshold value stress；
It is static stress ordinate is dynamic stress that crackle, which does not extend equivalent curve figure abscissa,.
6. the blade and blade basin blade back crack type hard object damage according to claim 1 for considering high and low week fatigue can use the limit Determine method, it is characterised in that: in the step (5), the leaf basin of blade and the static stress and dynamic stress of blade back each point It is indicated using unit Von-mises equivalent stress, represents the unit size of leaf basin blade back point as 1mm.
7. the blade and blade basin blade back crack type hard object damage according to claim 1 for considering high and low week fatigue can use the limit Determine method, it is characterised in that: in the step (6), take and do not extend by the corresponding crackle of high cycle fatigue load wherein It is worth the minimum value of the determining crack size of curve and the crack size determined by low cycle fatigue loading as blade and blade basin blade back The available limit of the hard object damage of tearing/crack type at the point.
CN201811115062.1A 2018-09-25 2018-09-25 Method for determining usable limit of blade leaf basin leaf back crack type hard object damage considering high and low cycle fatigue Active CN109374450B (en)

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CN112733398A (en) * 2020-12-29 2021-04-30 南京航空航天大学 Method for determining repair-free limit of impact damage of pit-type hard object

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