CN109933816A - The creep incubation period prediction technique of residual stress and contained effect is coupled under the conditions of elastic transient creep - Google Patents
The creep incubation period prediction technique of residual stress and contained effect is coupled under the conditions of elastic transient creep Download PDFInfo
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Abstract
The invention discloses the creep incubation period prediction techniques that residual stress and contained effect thermal structure are coupled under the conditions of a kind of elastic transient creep, the present invention proposes the creep incubation period prediction model of coupling residual stress and contained effect on the basis of Davies works.The creep incubation period that factor Z calculates consideration residual stress is followed using elasticity with reference to that should make laws, is introduced.Residual stress is generated by precommpression using compact tensile specimen (CT), and applies main load and carries out creep test.The present invention brief introduction effectively can predict creep incubation period under the conditions of elastic transient creep in the structure.
Description
Technical field
The present invention relates to the creep of coupling residual stress and contained effect thermal structure under the conditions of elastic transient creep is pregnant
The evaluation of phase engineering critical is educated, that is, is determined when, there are face crack and when being under the conditions of transient creep, evaluating this in structure
The creeping crack initiating life of thermal structure.
Background technique
Energy resource structure based on fire coal is one of the main reason of China's haze weather, and coal fired power generation be China at present most
Main generation mode, the trend is by long-term existence.Therefore, in addition to restructuring the use of energy, develop the ultra supercritical of high effect cleaning
(USC) unit is one of important channel of energy-saving and emission-reduction.However, the raising of vapor (steam) temperature and pressure and other parameters causes unit crucial
The Service Environment very severe of high-temperature pipe, it is various scarce that there are crackle, lack of penetration, weld blowhole and slag inclusions etc. especially in pipeline
It falls into, seriously threatens the safe operation of unit, need to carry out it accurate life appraisal of science.
In decades, for cracking member under high temperature, the development abroad review approach of a variety of high-temperature creep life-spans and
Method.Creep incubation period is the elapsed-time standards longest stage in creep process, and the Accurate Prediction of incubation period is for thermal structure
Creep life prediction is of great significance；The incubation period prediction model that Davies et al. is proposed based on toughness dissipation model considers
The integrality of creep process stress variation, but the influence of the residual stress of structure and contained effect to incubation period is
To research；Residual stress, contained effect widely exist in the high-temperature component of processing and manufacturing, and to the service life of component
Cause significant impact.The research for being largely directed to residual stress and contained effect in the case of high-temerature creep is also unfolded extensively.Cause
This establishes the creep incubation period prediction model of coupling residual stress and contained effect, more accurately can completely assess compound add
Carry the creep incubation period of structure.
Summary of the invention
For the present invention on the basis of Davies works, the creep incubation period for proposing coupling residual stress and contained effect is pre-
Survey model.The creep incubation period that factor Z calculates consideration residual stress is followed using elasticity with reference to that should make laws, is introduced.Using tight
Tensile sample (CT) gather by precommpression generation residual stress, and applies main load and carries out creep test.
The technical solution adopted to achieve the purpose of the present invention is:
The creep incubation period of residual stress and contained effect thermal structure is coupled under the conditions of elastic transient creep of the invention
Prediction technique, comprising the following steps:
S1: the compression-loaded of predefined size is carried out to CT sample ontology first with upper round pin, lower round pin, then in release
Round pin, lower round pin can generate residual stress distribution near the notch of CT sample ontology；
S2: it is inserted into precrack in the indentation, there containing residual stress, to carry out creep test；
S3: apply main load in upper main load pin hole, lower main load pin hole using pin, carry out high-temerature creep test；
S4: necessity required for calculating the sample incubation period of CT containing residual stress can be obtained by creep finite element modelling and joined
Number.Under the conditions of elastic transient creep, as shown in figure 4, the primary stress of research point is elastic stress state, conversion time is reached
tK-RRAfter enter transient creep stress state；
Calculating incubation period mainly comprises the steps that
(1) stress intensity factor under Combined Loading is calculated first, its calculation formula is:
(I) in:
Wherein:It is the stress intensity factor contained only under residual stress that simulation calculates, unit is MPa (m1/2)；It is main loading stress intensity factor, unit is MPa (m1/2)；P is main load, unit N；B is sample thickness, and unit is
Mm, BnIt is the net thickness of sample (B in the applicationn=B), unit mm；A/W is precrack length ratio, and a is that precrack is long
Degree, using the horizontal linear distance in the upper main load pin hole center of circle to precrack rear end, unit mm；W is nominal specimen width,
Using the upper main load pin hole center of circle to the horizontal linear distance of CT sample ontology rear end, unit mm；F (a/W) is that CT sample is several
What coefficient, it is only related with a/W；V is nondimensional plasticity continuous item, is calculated as follows:
(II) V in0It is dimensionless parameter,
It is plasticity Residual stress intensity factors, unit is MPa (m1/2)；It is elastic residual stress intensity factor,
Unit is MPa (m1/2),Utilize JSIt calculates, JSIt is residual stress fracture parameter off field, unit MPam:
Wherein: E ' is effective modulus of elasticity: E'=E/ (1- ν2).E is elasticity modulus, and ν is Poisson's ratio, and the two is referring to text
It offers: (Zhao L, Jing H, Xu L, Han Y, Xiu J.Evaluation of constraint effects on creep
crack growth by experimental investigation and numerical simulation.Engng
Fract Mech 2012；96:251–66.).And JSAll extracted using finite element modelling result；
(II) in: LrIt is dimensionless parameter, describes main load amplitude:
Wherein: σyIt is yield strength, unit MPa, referring to document: (Zhao L, Jing H, Xu L, Han Y, Xiu
J.Evaluation of constraint effects on creep crack growth by experimental
investigation and numerical simulation.Engng Fract Mech 2012；96:251–66.)；
It is main load reference stress, unit MPa is calculated with following formula:
Wherein: nLFor dimensionless crackle depth-to-width ratio parameter, it is calculate by the following formula:
Constant
(II) in:
Wherein:It is the main loading stress intensity factor of elasticity, unit is MPa (m1/2),It is the main loading stress of plasticity
Intensity factor, unit are MPa (m1/2)；It is calculated using finite element modelling result:
(II) in: β describes the amplitude of residual stress, is dimensionless parameter；
It is secondary load reference stress, unit MPa utilizes finite element simulation calculation；
(II) in: Z is that nondimensional elasticity follows the factor, extracts stress-strain relation from finite element modelling result,
Take equivalent creep strain incrementWith Equivalent Elasticity strain incrementRatio:
(2) steady state creep combined stress C* integrated value off field is calculated, its calculation formula is:
Wherein: A is creep hardening coefficient, unit MPa-n·h-1, KIIt is mixed-mode stress-intensity factor, unit MPa
(m1/2)。It is initial reference stress, unit MPa；
(3) the load loop integral value for splitting that sharp parameter C (t) is reflection transient creep process, unit MPa are then calculated
mm·(h-1), it is calculated using referential stress revisal method:
(V) in: σrefIt is total Reference Stress, unit MPa is calculated using following integral formula:
Wherein:It is always with reference to strain rate, unit h-1, It is main load reference strain
Rate, unit h-1,
(V) in: εrefIt is total with reference to strain, is calculated using following formula:
ε ref=ε0 ref +A∫σn refdt
Wherein: ε0 refIt is initial reference strain, is extracted by finite element modelling.
(4) the contained parameter Q* under the conditions of transient creep is calculatedRR, its calculation formula is:
It is creep strain change rate, unit h-1, related with material at high temperature creep attribute, n is that nondimensional creep is answered
Power hardenability value, n andReferring to document: (Zhao L, Jing H, Xu L, Han Y, Xiu J.Evaluation of
constraint effects on creep crack growth by experimental investigation and
numerical simulation.Engng Fract Mech 2012；96:251-66.), InIt is dimensionless letter related with n
Number, InOccurrence can be obtained with consulting literatures: Shih, C.F..1983.Tables of Hutchinson-Rice-
Rosengren Singular Field Quantities.Brown University Technical Report,MRL E-
147.
It is the opening stress value at the crackle forward position obtained using FEM calculation, unit is Mpa, σ0It is material
Yield strength, unit is MPa, referring to document: (Zhao L, Xu L, Han Y, Jing H.Two-parameter
characterization of constraint effect induced by specimen size on creep crack
growth.Engng Fract Mech 2012；96:251-66.), L is scalar distance, takes 1mm.
(VI) in: σ22It is the opening stress value in the crackle forward position obtained using HRR stress field calculation, unit is MPa,
Wherein: r is spacing of the crackle rear portion tip to crackle forward position research point, and unit is mm, and θ is crack tip angle,It is creep strain change rate, unit h-1, related with material at high temperature creep attribute, n is that the hardening of nondimensional creep stress refers to
Number, n andReferring to document: (Zhao L, Jing H, Xu L, Han Y, Xiu J.Evaluation of constraint
effects on creep crack growth by experimental investigation and numerical
simulation.Engng Fract Mech 2012；96:251-66.), InIt is dimensionless function related with n,
It is dimensionless function related with θ and n, InWithOccurrence can be obtained with consulting literatures: Shih,
C.F..1983.Tables of Hutchinson-Rice-Rosengren Singular Field Quantities.Brown
University Technical Report,MRL E-147.
(5) transient creep equivalent stress is calculatedIts calculation formula is:
Wherein:It is dimensionless function related with θ and n, occurrence can be obtained with consulting literatures: Shih,
C.F..1983.Tables of Hutchinson-Rice-Rosengren Singular Field Quantities.Brown
University Technical Report,MRL E-147.
Calculate elastic equivalent stressIts calculation formula is:
It is dimensionless function related with crack tip angle, θ and Poisson's ratio ν, the acquisition that can table look-up (Webster,
G.A.,1994.Fracturemechanicsinthecreeprange.JournalofStrainAnalysisforEngineer
ingDesign29,215–223.)
(6) conversion time t is calculated using MATALAB softwareK-RR: meet at this moment:
Elastic stage damages aggregate-value:
MSFKFor the Multiaxial stress factor under elastic condition, calculated according to Cocks and Ashby relational expression:
Wherein: n is nondimensional creep stress hardenability value, and sinh is hyperbolic sine function, hkFor three axis of elastic stress
Degree, under elastic stress state:
Wherein: θ is crack tip angle, and ν is Poisson's ratio.
(4) transient creep stress field time lower incubation period t is then calculatedi, its calculation formula is:
(VII) in: d (mm) is that creep impairment reaches 1 distance extended before determining to split point when creep germinating occurs, i.e., compacted
Become the critical distance that germinating occurs.
(VII) in: MSFRRFor the Multiaxial stress factor under the condition of palsticity, calculated according to Cocks and Ashby relational expression:
Sinh is hyperbolic sine function, hRRFor three axis degree of transient creep stress, under plastic stress state:
Wherein mean stressUnit is MPa, its calculation formula is:
Wherein: σ11And σ33It is the stress value in the crackle forward position obtained using RRss stress field calculation, unit is MPa,
Wherein:It is dimensionless function related with θ and n, occurrence can be obtained with consulting literatures:
Shih,C.F..1983.Tables of Hutchinson-Rice-Rosengren Singular Field
Quantities.Brown University Technical Report,MRL E-147.。
Preferably, the finite element modelling carries out calculating simulation, σ using ABAQUS6.1422 FEM、JS、
ε0 refExtraction process the following steps are included:
(5) finite element model of the CT sample of precommpression load is initially set up, specific size can be found in Fig. 1, in material category
Property module in resilient plastic parameter is set, compressive load and contained condition are set in payload module: including symmetric condition and
Rigid condition.In the rigid contact for contacting setting compression round pin and sample upper and lower surface in module, set in analysis step module
Set output parameter: stress value, in mesh module grid division；
(6) task computation is submitted in operation module, obtains the calculated result of residual stress, in destination file, from field variable
In can directly extract secondary load reference stress
(7) sample model of identical size is established, main tensile load test is carried out, reference can be made to Fig. 1, in material properties module
In resilient plastic creep parameters under high temperature are set, in mesh module grid division, contact setting in module stretch pin and
The rigid contact of pin hole, and it is inserted into precrack in a model, output parameter is set in analysis step module: ess-strain
Value, stress strength factor K value, fracture parameter J integrated value, are arranged tensile load and contained condition in payload module: including
Symmetric condition and rigid condition import in preloading stress field and walk good residual stress；
(8) task computation is submitted in operation module, obtains the creep stretching experiment calculated result containing residual stress, as a result
In file, the tensile load moment is not applied also after being inserted into crackle, the available initial reference strain from field variable
σ22 FEM、The available elastic residual stress intensity factor from historical variableAnd residual stress fracture parameter JS,
Apply the initial time of tensile load, the available main density of load factor of plasticityIt is available equivalent from historical variable
Stress obtains equivalent creep strain increment with the change curve of overall strain increment from curve,Equivalent Elasticity strain incrementAnd then it obtains elasticity and follows factor Z calculation method.
Compared with prior art, the beneficial effects of the present invention are:
The invention proposes creep incubation periods under the conditions of the elastic transient creep of coupling residual stress and contained effect to predict
Model, compared with existing model, the design method can expand to original prediction model in the model containing residual stress, from
And propose creep incubation period prediction technique under the conditions of a kind of transient creep of simplification, therefore can be succinct effective pre- in the structure
Measure creep incubation period under the conditions of elastic transient creep.
Detailed description of the invention
Fig. 1 show the creep incubation period that residual stress and contained effect thermal structure are coupled under elastic condition of the invention
The structural schematic diagram of prediction model.
Wherein: the upper round pin of 1-, 2-CT sample ontology, the upper main load pin hole of 3-, 4- slot, 5- notch, 6- precrack, under 7-
Main load pin hole, round pin under 8-.
Fig. 2 is creeping crack germinating critical condition schematic diagram.
Fig. 3 is that elasticity follows factor Z calculation method.
Fig. 4 is stress transmission schematic diagram.
Specific embodiment
The present invention is described in further detail below in conjunction with the drawings and specific embodiments.It should be appreciated that described herein
Specific embodiment be only used to explain the present invention, be not intended to limit the present invention.
The creep incubation period of residual stress and contained effect thermal structure is coupled under the conditions of elastic transient creep of the invention
Prediction model, including CT sample ontology 1, the upper and lower ends of the CT sample ontology are respectively equipped with round pin 1, lower round pin 2, CT examination
The middle part front end of sample body is equipped with slot 4, and the rear portion of slot 4 is equipped with notch 5, and the rear portion of notch 5 is equipped with precrack 6, slot 4, notch
5, precrack 6 in the same plane, is additionally provided with main load pin hole 3, lower main load pin hole 7, upper main load on CT sample ontology 1
Lotus pin hole 3, the setting symmetrical above and below of lower main load pin hole 7, are separately positioned on the upper and lower ends of slot 4.
P92 high-temperature refractory steel is chosen, with B=20mm, the CT sample of W=40mm, a/W=0.5 are as research object, with pre-
12000N and main load p=12000N are loaded as research load.Its main material attribute see the table below:
The creep incubation period prediction technique of residual stress and contained effect thermal structure is coupled under elastic condition of the invention,
The following steps are included:
S1: the compression-loaded of predefined size is carried out to CT sample ontology first with upper round pin, lower round pin, then in release
Round pin, lower round pin can generate residual stress distribution near the notch of CT sample ontology；
S2: it is inserted into precrack in the indentation, there containing residual stress, to carry out creep test；
S3: apply main load in upper main load pin hole, lower main load pin hole using pin, carry out high-temerature creep test；
S4: necessity required for calculating the sample incubation period of CT containing residual stress can be obtained by creep finite element modelling and joined
Number.Under the conditions of elastic transient creep, as shown in figure 4, the primary stress of research point is elastic stress state, conversion time is reached
tK-RRAfter enter transient creep stress state.Calculating incubation period mainly comprises the steps that
Technical solution of the present invention is further illustrated below with reference to specific example.
(1) each parameter is calculated first:
(a) the main density of load factor of elasticity:
Following data are extracted by finite element result:
(1) first, in accordance with size, the finite element model of the CT sample of precommpression load is established.It is set in material properties module
Set resilient plastic parameter.Compressive load and contained condition are set in payload module, and the contained condition includes symmetric condition
And rigid condition, in the rigid contact for contacting setting compression round pin and sample upper and lower surface in module, in analysis step module
Set output parameter: stress value, in mesh module grid division；
(2) task computation is submitted in operation module, obtains the calculated result of residual stress.In destination file, from field variable
In can directly extract secondary load reference stress
(3) sample model of identical size is established, main tensile load test is carried out, reference can be made to Fig. 1.In material properties module
In resilient plastic creep parameters under high temperature are set, in mesh module grid division, contact setting in module stretch pin and
The rigid contact of pin hole, and it is inserted into precrack in a model, set output parameter in analysis step module: stress value is answered
Tensile load and contained condition is arranged: including symmetrical in power intensity factor K value, fracture parameter J integrated value in payload module
Condition and rigid condition import in preloading stress field and walk good residual stress；
(4) task computation is submitted in operation module, obtains the creep stretching experiment calculated result containing residual stress, as a result
In file, do not apply the tensile load moment also after being inserted into crackle, does not apply the tensile load moment also after being inserted into crackle, from field
Available initial reference strain in variableFrom historical variable available elastic residual stress intensity because
SonAnd residual stress fracture parameter JS=0.013MPam, can calculate plasticity is residual
Residue stress intensity factor:In the initial time for applying tensile load, available plasticity master
The density of load factor
(b) main load reference stress:
(c) main load amplitude:
(d) residual stress Reference Stress:
The amplitude of residual stress:
(e) elasticity follows the factor: through the step (4) in above-mentioned abaqus finite element modelling step, from historical variable
Available equivalent creep strain increment, obtains Fig. 3,Equivalent Elasticity strain incrementIt can by Fig. 3
It reads
(f) plasticity continuous item:
(2) so, the stress intensity factor under Combined Loading
Initial reference stress:
Steady state creep combined stress C* integrated value off field are as follows:
(3) then in the available stress value of field variable
(a) it tables look-up:InThe material parameter ε of=4.99, P92 steelcrit=0.2；N=5.23 is being counted
Calculate creep stress and it is contained when, we take the distance r=d=0.05mm before splitting point.
(b) it tables look-up:Elastic equivalent stress
(4) it tables look-up:
Transient creep equivalent stress
Conversion time tK-RR: it utilizesAnd MATALAB is calculated: tK-RR=0h
Elastic stage damages aggregate-value:
(5) germinating occurred under transient creep stress field is then calculated:
It tables look-up:
Mean stress:
Three axis degree of stress:
The Multiaxial stress factor:
D (mm) is that creep impairment reaches 1 distance extended, i.e. creep germinating hair before determining to split point when creep germinating occurs
Raw critical distance generally takes the crystallite dimension of research material, as shown in Figure 2.
Incubation period under the conditions of transient creep:
It is integrated using MATALAB solution: ti K-RR=1755h.
The above is only a preferred embodiment of the present invention, it is noted that for the common skill of the art
For art personnel, various improvements and modifications may be made without departing from the principle of the present invention, these improvements and modifications
Also it should be regarded as protection scope of the present invention.
Claims (3)
1. coupling the creep incubation period prediction technique of residual stress and contained effect, feature under the conditions of a kind of elasticity transient creep
It is, S1: carries out the compression-loaded of predefined size to CT sample ontology first with upper round pin, lower round pin, then circle in release
Pin, lower round pin can generate residual stress distribution near the notch of CT sample ontology；
S2: it is inserted into precrack in the indentation, there containing residual stress, to carry out creep test；
S3: apply main load in upper main load pin hole, lower main load pin hole using pin, carry out high-temerature creep test；
S4: can obtain call parameter required for calculating the sample incubation period of CT containing residual stress by creep finite element modelling,
Under the conditions of elastic transient creep, the primary stress studied a little is elastic stress state, reaches conversion time tK-RRAfter enter
Transient creep stress state；
Calculating incubation period mainly comprises the steps that
(1) stress intensity factor under Combined Loading is calculated first, its calculation formula is:
(I) in:
Wherein:It is the stress intensity factor contained only under residual stress that simulation calculates, unit is MPa (m1/2)；It is
Main loading stress intensity factor, unit are MPa (m1/2)；P is main load, unit N；B is sample thickness, unit mm, Bn
It is the net thickness of sample, unit mm；A/W is precrack length ratio, and a is precrack length, using upper main load pin hole
Horizontal linear distance of the center of circle to precrack rear end, unit mm；W is nominal specimen width, using upper main load pin hole circle
Horizontal linear distance of the heart to CT sample ontology rear end, unit mm；F (a/W) is CT sample geometrical factor, only related with a/W；
V is nondimensional plasticity continuous item, is calculated as follows:
(II) in: V0It is dimensionless parameter,
It is plasticity Residual stress intensity factors, unit is MPa (m1/2)；It is elastic residual stress intensity factor, unit
For MPa (m1/2),Utilize JSIt calculates, JSIt is residual stress fracture parameter off field, unit MPam:
Wherein: E ' is effective modulus of elasticity: E'=E/ (1- ν2), E is elasticity modulus, and ν is Poisson's ratio,And JSAll using limited
First analog result is extracted；
(II) in: LrIt is dimensionless parameter, describes main load amplitude:
Wherein: σyIt is yield strength, unit MPa；It is main load reference stress, unit MPa is calculated with following formula:
Wherein: nLFor dimensionless crackle depth-to-width ratio parameter, it is calculate by the following formula:
Constant
(II) in:
Wherein:It is the main loading stress intensity factor of elasticity, unit is MPa (m1/2),It is the main loading stress intensity of plasticity
The factor, unit are MPa (m1/2)；It is calculated using finite element modelling result:
(II) in: β describes the amplitude of residual stress, is dimensionless parameter；
It is secondary load reference stress, unit MPa utilizes finite element simulation calculation；
(II) in: Z is that nondimensional elasticity follows the factor, extracts stress-strain relation from finite element modelling result, takes
Imitate creep strain incrementWith Equivalent Elasticity strain incrementRatio:
(2) steady state creep combined stress C* integrated value off field is calculated, its calculation formula is:
Wherein: A is creep hardening coefficient, unit MPa-n·h-1, KIIt is mixed-mode stress-intensity factor, unit is MPa (m1 /2),It is initial reference stress, unit MPa；
(3) the load loop integral value for splitting that sharp parameter C (t) is reflection transient creep process, unit MPamm are then calculated
(h-1), it is calculated using referential stress revisal method:
(V) in: σrefIt is total Reference Stress, unit MPa is calculated using following integral formula:
Wherein:It is always with reference to strain rate, unit h-1, It is main load reference strain rate,
Unit is h-1,
(V) in: εrefIt is total with reference to strain, is calculated using following formula:
εref=ε0 ref+A∫σn refdt
Wherein: ε0 refIt is initial reference strain, is extracted by finite element modelling,
(4) the contained parameter Q* under the conditions of transient creep is calculatedRR, its calculation formula is:
It is creep strain change rate, unit h-1, related with material at high temperature creep attribute, n is that nondimensional creep stress is hard
Change index, InIt is dimensionless function related with n,
It is the opening stress value at the crackle forward position obtained using FEM calculation, unit is Mpa, σ0It is the surrender of material
Intensity, unit are MPa, and L is scalar distance, take 1mm；
(VI) in: σ22It is the opening stress value in the crackle forward position obtained using HRR stress field calculation, unit is MPa,
Wherein: r is spacing of the crackle rear portion tip to crackle forward position research point, and unit is mm, and θ is crack tip angle,It is compacted
Allergic effect becomes change rate, unit h-1, related with material at high temperature creep attribute, n is nondimensional creep stress hardenability value, InIt is
Dimensionless function related with n,It is dimensionless function related with θ and n,
(5) transient creep equivalent stress is calculatedIts calculation formula is:
Wherein:It is dimensionless function related with θ and n,
Calculate elastic equivalent stressIts calculation formula is:
It is dimensionless function related with crack tip angle, θ and Poisson's ratio ν,
(6) conversion time t is calculated using MATALAB softwareK-RR: meet at this moment:
Elastic stage damages aggregate-value:
MSFKFor the Multiaxial stress factor under elastic condition, calculated according to Cocks and Ashby relational expression:
Wherein: n is nondimensional creep stress hardenability value, and sinh is hyperbolic sine function, hkFor three axis degree of elastic stress,
Under elastic stress state:
Wherein: θ is crack tip angle, and ν is Poisson's ratio,
(4) transient creep stress field time lower incubation period t is then calculatedi, its calculation formula is:
(VII) in: d (mm) is that creep impairment reaches 1 distance extended before determining to split point when creep germinating occurs, i.e. creep is sprouted
The raw critical distance of hair tonic,
(VII) in: MSFRRFor the Multiaxial stress factor under the condition of palsticity, calculated according to Cocks and Ashby relational expression:
Sinh is hyperbolic sine function, hRRFor three axis degree of transient creep stress, under plastic stress state:
Wherein mean stressUnit is MPa, its calculation formula is:
Wherein: σ11And σ33It is the stress value in the crackle forward position obtained using RRss stress field calculation, unit is MPa,
Wherein:It is dimensionless function related with θ and n.
2. coupling residual stress under the conditions of elasticity transient creep as described in claim 1 and the creep incubation period of contained effect being pre-
Survey method, which is characterized in that the finite element modelling carries out calculating simulation, σ using ABAQUS6.1422 FEM、JS、ε0 refExtraction process the following steps are included:
(1) finite element model for initially setting up the CT sample of precommpression load is arranged resilient plastic in material properties module and joins
Number, compressive load and contained condition are arranged in payload module: including symmetric condition and rigid condition, contacting in module
The rigid contact of compression round pin and sample upper and lower surface is set, sets output parameter in analysis step module: stress value,
Mesh module grid division；
(2) task computation is submitted in operation module, obtains the calculated result of residual stress, it, can from field variable in destination file
Directly to extract secondary load reference stress
(3) sample model of identical size is established, main tensile load test is carried out, is arranged under high temperature in material properties module
The rigid contact for stretching pin and pin hole is arranged contacting in mesh module grid division in resilient plastic creep parameters in module,
And it is inserted into precrack in a model, output parameter is set in analysis step module: ess-strain value, stress strength factor K
Value, fracture parameter J integrated value, are arranged tensile load and contained condition: including symmetric condition and fixed strip in payload module
Part imports in preloading stress field and walks good residual stress；
(4) task computation is submitted in operation module, obtains the creep stretching experiment calculated result containing residual stress, destination file
In, do not apply the tensile load moment also after being inserted into crackle, the available initial reference strain from field variableσ22 FEM、The available elastic residual stress intensity factor from historical variableAnd residual stress fracture parameter JS, applying
The initial time of tensile load, the available main density of load factor of plasticityThe available equivalent stress from historical variable
With the change curve of overall strain increment, equivalent creep strain increment is obtained from curve,Equivalent Elasticity strain increment
And then it obtains elasticity and follows factor Z calculation method.
3. coupling residual stress under the conditions of elasticity transient creep as described in claim 1 and the creep incubation period of contained effect being pre-
Survey method, which is characterized in that Bn=B.
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