CN108733861B - Creep induction period prediction method containing residual stress under plastic condition - Google Patents

Creep induction period prediction method containing residual stress under plastic condition Download PDF

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CN108733861B
CN108733861B CN201710271285.6A CN201710271285A CN108733861B CN 108733861 B CN108733861 B CN 108733861B CN 201710271285 A CN201710271285 A CN 201710271285A CN 108733861 B CN108733861 B CN 108733861B
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CN108733861A (en
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徐连勇
邬栋权
荆洪阳
韩永典
赵雷
吕小青
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Tianjin University
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    • 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
    • G06F30/23—Design optimisation, verification or simulation using finite element methods [FEM] or finite difference methods [FDM]
    • 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
    • G01N3/28—Investigating ductility, e.g. suitability of sheet metal for deep-drawing or spinning
    • 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
    • G01N2203/0014—Type of force applied
    • G01N2203/0016—Tensile or compressive
    • G01N2203/0017—Tensile
    • 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
    • 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
    • G01N2203/0071—Creep
    • 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
    • G01N2203/02—Details not specific for a particular testing method
    • G01N2203/022—Environment of the test
    • G01N2203/0222—Temperature
    • G01N2203/0226—High temperature; Heating means
    • G—PHYSICS
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    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2111/00—Details relating to CAD techniques
    • G06F2111/10—Numerical modelling

Abstract

The invention discloses a creep induction period prediction method containing residual stress under a plastic condition, and provides a creep induction period prediction model considering the residual stress on the basis of Davies work. By utilizing a reference stress method, an elastic following factor Z is introduced to calculate a creep induction period considering residual stress. Creep experiments were performed using compact tensile specimens (CT) to generate residual stress by precompression and applying a main load. The invention has the beneficial effects that: the design method can expand the original prediction model into a model containing residual stress, so that a simplified creep induction period prediction method under the plastic condition is provided, and the creep induction period under the plastic condition can be simply and effectively predicted in the structure.

Description

Creep induction period prediction method containing residual stress under plastic condition
Technical Field
The invention relates to a creep induction period engineering critical evaluation of a high-temperature structure containing residual stress under a plastic condition, namely, the creep crack initiation life of the high-temperature structure is evaluated when a surface crack exists in the structure and the structure is under the plastic stress condition.
Background
The energy structure mainly based on coal burning is one of the main causes of haze weather in China, and coal burning power generation is the most main power generation mode in China at present, and the trend exists for a long time. Therefore, besides changing the energy structure, the development of a high-efficiency clean Ultra Supercritical (USC) unit is one of the important ways of energy conservation and emission reduction. However, the service environment of the key high-temperature pipeline of the unit is very severe due to the improvement of parameters such as steam temperature, steam pressure and the like, and particularly, various defects such as cracks, incomplete penetration, welding pores, slag inclusion and the like exist in the pipeline, so that the safe operation of the unit is seriously threatened, and scientific and accurate service life evaluation needs to be carried out on the unit.
For decades, various high temperature creep life assessment criteria and methods have been developed abroad for crack-containing components at high temperatures. The creep induction period is the longest period in the creep process, and the accurate prediction of the induction period has great significance for predicting the creep life of a high-temperature structure; an incubation period prediction model provided by Davies et al based on a toughness dissipation model considers the integrity of stress change in a creep process, but the influence of structural residual stress on the incubation period is not researched; residual stresses are widely present in process-manufactured high temperature components and have a significant impact on the service life of the component. A large number of studies have been widely conducted on the residual stress (residual stress) in the case of high-temperature creep. Therefore, a creep induction period prediction model considering the residual stress is established, and the creep induction period of the composite loading structure can be more accurately and completely evaluated.
Disclosure of Invention
On the basis of Davies work, the invention provides a creep induction period prediction model considering residual stress. By utilizing a reference stress method, an elastic following factor Z is introduced to calculate a creep induction period considering residual stress. Creep experiments were performed using compact tensile specimens (CT) to generate residual stress by precompression and applying a main load.
The technical scheme adopted for realizing the purpose of the invention is as follows:
the method for predicting the creep induction period containing residual stress under the plastic condition comprises the following steps:
s1: establishing a model: the model comprises a CT sample body, wherein a groove is formed in the front end of the middle of the CT sample body, a notch is formed in the rear part of the groove, an upper main load pin hole and a lower main load pin hole are further formed in the CT sample body, and the upper main load pin hole and the lower main load pin hole are arranged up and down correspondingly and are respectively arranged at the upper end and the lower end of the groove;
s2, firstly, the upper round pin and the lower round pin are used for carrying out compression loading with a preset size on the upper end and the lower end of the CT sample body, and then the upper round pin and the lower round pin are released, so that residual stress distribution can be generated near the notch of the CT sample body;
s3, inserting a prefabricated crack at the notch containing the residual stress to perform a creep test;
s4, applying main loads to the upper main load pin hole and the lower main load pin hole by using the pins, and performing a high-temperature creep test;
s5: necessary parameters required for calculating the incubation period of the CT sample containing residual stress can be obtained through creep finite element simulation, and the method mainly comprises the following steps of:
(1) firstly, calculating a stress intensity factor under composite loading, wherein the calculation formula is as follows:
Figure GDA0002230278860000021
in (I):
Figure GDA0002230278860000022
Figure GDA0002230278860000023
wherein: kI SIs a stress intensity factor under the simulation calculation and only contains residual stress, and the unit is MPa (m)1/2)；KI PIs the main load stress intensity factor with the unit of MPa (m)1/2) (ii) a P is the primary load in N; b is the thickness of the specimen in mm, BnIs the net thickness of the sample, in mm; a/W is the length ratio of the prefabricated crack, a is the length of the prefabricated crack, and the horizontal straight line distance from the center of the upper main load pin hole to the rear end of the prefabricated crack is adopted, and the unit is mm; w is the nominal sample width, and the horizontal linear distance from the circle center of the upper main load pin hole to the rear end of the CT sample body is adopted, and the unit is mm; f (a/W) is the geometric coefficient of the CT sample and is only related to a/W; v is a dimensionless plastic related term calculated as follows:
Figure GDA0002230278860000024
in (II) V0Is a non-dimensional parameter, and the parameter is,
Figure GDA0002230278860000025
wherein: kJ SIs a plastic residual stress intensity factor with the unit of MPa (m)1/2)；KI SIs a stress intensity factor under the simulation calculation and only contains residual stress, and the unit is MPa (m)1/2)，KJ SUsing JSCalculation, JSIs a fracture parameter under a residual stress field, and the unit is MPa.m;
Figure GDA0002230278860000026
wherein: e' is the effective modulus of elasticity: e ═ E/(1-v)2) E is elastic modulus, ν is poisson's ratio, E, ν is described in literature: (Zhao L, king H, Xu L, Han Y, Xiu J. evaluation of knowledge effects on creattrack growth by experimental information and numerical simulation. EngngFract Mech2012；96:251–66.)，KI SAnd JSExtracting by using finite element simulation results;
in (II) LrIs a dimensionless parameter describing the main load amplitude:
Figure GDA0002230278860000027
wherein: sigmayIs yield strength, related to material properties, in MPa, see literature: (ZHao L, lacing H, XuL, Han Y, Xiu J. evaluation of contract effects on crop grow growth by yexperiment information and numerical simulation. Engng frame Mech 2012; 96: 251-66.);
Figure GDA0002230278860000028
is the main load reference stress in MPa, calculated by the following formula:
Figure GDA0002230278860000031
wherein: n isLFor dimensionless crack aspect ratio parameters, the following is calculated:
Figure GDA0002230278860000032
constant number
Figure GDA0002230278860000033
(II):
Figure GDA0002230278860000034
KI Pis the elastic main load stress intensity factor, KJ PIs a plastic main load stress intensity factor with the unit of MPa (m)1 /2)； KJ PCalculating by using a finite element simulation result:
β describes the amplitude of residual stress, which is a dimensionless parameter;
Figure GDA0002230278860000035
Figure GDA0002230278860000036
is the secondary load reference stress, utilizes finite element simulation calculation,
in the step (II), Z is a dimensionless elastic following factor, a stress-strain relation is extracted from a finite element simulation result, and an equivalent creep strain increment is taken
Figure GDA0002230278860000037
Equivalent elastic strain increment
Figure GDA0002230278860000038
The ratio of (A) to (B):
Figure GDA0002230278860000039
(2) calculating the J integral value under the plastic composite stress field, wherein the calculation formula is as follows:
Figure GDA00022302788600000310
wherein: kIIs the composite stress intensity factor, E' is the effective modulus of elasticity: e ═ E/(1-v)2) Where ν is poisson's ratio, E is elastic modulus, ν is poisson's ratio, and both E and ν are described in the literature: (ZHao L, lacing H, Xu L, Han Y, XiuJ. evaluation of contract effects on crop grow growth by experiment simulation and numerical simulation. Engng frame Mech 2012; 96: 251-66.);
(3) then calculating the incubation period time t under the plastic stress fieldi HRRThe calculation formula is as follows:
Figure GDA00022302788600000311
(III) in (III): epsiloncritIs uniaxial creep toughness, which is related to material properties and has a unit of 1,
Figure GDA00022302788600000312
is the creep strain rate of change, which is related to the high temperature creep property of the material,. epsiloncritAnd
Figure GDA00022302788600000313
see literature: (ZHao L, Jing H, Xu L, Han Y, XiuJ. evaluation of contract effects on crop grow growth by experiment simulation and numerical simulation. Engng frame Mech 2012; 96: 251-66.), σ LP0Is the normalized stress in units of MPa,. epsilonP0Is the normalized strain with the unit of 1, α is the strain hardening coefficient, N is the strain hardening index, σP0、εP0α and N are described in the literature (Zhao L, Xu L, Han Y, Jing H.two-parameter chacterization of constrained effect induced by specific specimen size on peel crack growth. EngngFract Mech 2012; 96: 251-66.). INIs a non-dimensional function related to N,
Figure GDA0002230278860000041
is a dimensionless function related to theta and N, and the specific value can be obtained by looking up the literature: (Shih, C.F. 1983.Tables of Hutchinson-Rice-Rosenggren simple Field Technical Report, MRL E-147.)
(III) in (III): d (mm) is the distance extending until creep damage reaches 1 before the crack tip when creep initiation occurs, namely the critical distance of creep initiation.
(III) in (III): MSFHRRThe multiaxial stress factor under plastic condition is calculated according to the relationship of Cocks and Ashby:
Figure GDA0002230278860000046
n is a dimensionless creep stress hardening index, sinh is a hyperbolic sine function, hHRRThree degrees of plastic stress, in the plastic stress state:
Figure GDA0002230278860000042
wherein: theta is the crack tip angle, N is the dimensionless stress hardening index,
Figure GDA0002230278860000043
and
Figure GDA0002230278860000044
is a dimensionless function related to theta and N, and the specific value can be obtained by looking up the literature: (Shih, C.F. 1983.Tables of Hutchinson-Rice-Rosenggren simple Field Technical Report, MRL E-147.).
Preferably, d is the grain size of the material under investigation.
Preferably, Bn＝B。
Preferably, the finite element simulation is a computational simulation using ABAQUS6.14,
Figure GDA0002230278860000047
KI S、JS、KJ Pand the extraction process of Z comprises the following steps:
(5) firstly, establishing a finite element model of a pre-compressed loaded CT sample, setting elastic-plastic parameters in a material property module, setting compression load in a load module, and setting a constraint condition: including symmetric conditions and fixed conditions. The contact module is internally provided with a compression round pin which is in rigid contact with the upper surface and the lower surface of the sample, and the analysis step module is internally provided with output parameters: stress value, dividing grids in the grid module;
(6) the task calculation is submitted in the operation module to obtain the calculation result of the residual stress, and the secondary load reference stress can be directly extracted from the field variables in the result file
Figure GDA0002230278860000045
(7) Establishing a sample model with the same size, carrying out a main load tensile test, setting elastic-plastic creep parameters at high temperature in a material property module, dividing grids in a grid module, setting rigid contact between a tensile pin and a pin hole in a contact module, inserting a prefabricated crack in the model, and setting output parameters in an analysis step module: stress strain value, stress intensity factor K value, rupture parameter J integral value set up tensile load in the load module to and restrain the condition: the method comprises the steps of (1) introducing the calculated residual stress into a preloading stress field under a symmetrical condition and a fixed condition;
(8) submitting task calculation in the operation module to obtain the calculation result of the creep-tensile experiment containing residual stress, and obtaining the stress intensity factor K which is only under the residual stress and is subjected to simulation calculation from historical variables at the moment that tensile load is not applied after the crack is inserted in a result fileI SAnd the residue shouldForce fracture parameter JSAt the initial moment of applying the tensile load, the stress intensity factor K of the elastic main load can be obtainedJ PObtaining the change curve of the equivalent stress along with the total strain increment from the historical variables, obtaining the equivalent creep strain increment from the curve,
Figure GDA0002230278860000051
increment of equivalent elastic strain
Figure GDA0002230278860000052
Thereby obtaining the elastic tracking factor Z.
Compared with the prior art, the invention has the beneficial effects that:
compared with the existing model, the design method can expand the original prediction model into the model containing residual stress, so that the simplified prediction method of the creep induction period under the plastic condition is provided, and the creep induction period under the plastic condition can be simply and effectively predicted in the structure.
Drawings
FIG. 1 is a schematic illustration of a compact tensile specimen (CT) precompression;
FIG. 2 is a schematic representation of critical conditions for creep crack initiation;
FIG. 3 is a stress strain relationship.
Detailed Description
The invention is described in further detail below with reference to the figures and specific examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
In this example, a CT sample of P92 high temperature heat resistant steel, B20 mm, W40 mm, and a/W0.5, was selected as a study object, and a preload of 12000N and a main load P12000N were selected as study loads. The main material properties are given in the following table:
Figure GDA0002230278860000053
wherein: e-16 is the power of-16 of 10.
The method for predicting the creep induction period containing residual stress under the plastic condition comprises the following steps:
s1: a model as shown in fig. 1 was established: the model comprises a CT sample body 2, wherein a groove 4 is formed in the front end of the middle of the CT sample body 2, a notch 5 is formed in the rear portion of the groove 4, an upper main load pin hole 3 and a lower main load pin hole 7 are further formed in the CT sample body 1, and the upper main load pin hole 3 and the lower main load pin hole 7 are arranged in a vertically corresponding mode and are respectively arranged at the upper end and the lower end of the groove 4;
s2, firstly, the upper round pin 1 and the lower round pin 8 are used for carrying out compression loading on the CT sample body 2 with a preset size, and then the upper round pin 1 and the lower round pin 8 are released, so that a certain residual stress distribution is generated near the gap 5 of the CT sample body 2;
s3, inserting the prefabricated crack 6 at the notch containing the residual stress, wherein the groove 4, the notch 5 and the prefabricated crack 6 are on the same plane to perform a creep test;
s4, applying main loads to the upper main load pin hole 3 and the lower main load pin hole 7 by using the pins, and performing a high-temperature creep test;
s5: necessary parameters required for calculating the incubation period of the CT sample body 2 containing residual stress can be obtained through creep finite element simulation. Under plastic conditions, the calculation of the induction period mainly comprises the following steps:
(1) first, each parameter is calculated:
(a) elastic main load strength factor:
Figure GDA0002230278860000061
Figure GDA0002230278860000062
the following data were extracted from the finite element results:
i) first, a finite element model of a pre-compressed loaded CT specimen is built by size. And setting elastic-plastic parameters in the material property module. Set up compression load in the load module to and restrain the condition, restrain the condition and include symmetry condition and fixed condition, set up the rigid contact of compression round pin and sample upper and lower surface in the contact module, set up output parameter in the analysis step module: stress value, dividing grids in the grid module;
and ii) submitting task calculation in the operation module to obtain a calculation result of the residual stress. In the result file, the secondary load reference stress can be directly extracted from the field variables
Figure GDA0002230278860000063
iii) model the same size specimen for the main load tensile test, see FIG. 1. Elastic-plastic creep parameters under high temperature are set in the material property module, grids are divided in the grid module, rigid contact between a stretching pin and a pin hole is set in the contact module, a prefabricated crack is inserted into the model, and output parameters are set in the analysis step module: stress value, stress intensity factor K value, rupture parameter J integral value set up tensile load in the load module to and the constraint condition: the method comprises the steps of (1) introducing the calculated residual stress into a preloading stress field under a symmetrical condition and a fixed condition;
iv) submitting task calculation in the operation module to obtain a calculation result of a creep and tension experiment containing residual stress, wherein in a result file, when no tensile load is applied after the crack is inserted, an elastic residual stress strength factor K can be obtained from historical variablesI S＝31.96809MPa·(m1/2) And residual stress rupture parameter JSThe plastic residual stress intensity factor can be calculated as 0.013MPa · m:
Figure GDA0002230278860000064
at the initial moment of applying the tensile load, the plastic main load strength factor can be obtained
Figure GDA0002230278860000065
Obtaining the change curve of the equivalent stress along with the total strain increment from the historical variables, and obtaining the equivalent creep strain increment from the curve as shown in FIG. 3
Figure GDA0002230278860000066
Increment of equivalent elastic strain
Figure GDA0002230278860000067
And further obtaining an elastic following factor Z calculation method.
(b) Main load reference stress:
Figure GDA0002230278860000071
Figure GDA0002230278860000072
(c) amplitude of main load:
Figure GDA0002230278860000073
Figure GDA0002230278860000074
(d) residual stress reference stress:
Figure GDA0002230278860000075
magnitude of residual stress:
Figure GDA0002230278860000076
(e) elastic following factor:
Figure GDA0002230278860000077
Figure GDA0002230278860000078
Figure GDA0002230278860000079
(f) plastic related terms:
Figure GDA00022302788600000710
Figure GDA00022302788600000711
(2) therefore, the stress intensity factor under composite loading
Figure GDA00022302788600000712
J integral value under composite loading:
Figure GDA00022302788600000713
(3) the germination that occurred under the plastic stress field was then calculated:
(a) and (6) looking up a table to obtain:
Figure GDA00022302788600000714
IN4.49, P92 steel has a material parameter n of 5.23, ∈crit＝0.2； N＝11,
Stress triaxial degree:
Figure GDA00022302788600000715
multiaxial stress factor:
Figure GDA0002230278860000081
d (mm) is the distance extending to 1 from the creep damage before the crack tip when creep initiation occurs, i.e. the critical distance for creep initiation, and the grain size of the material under study is generally taken, as shown in fig. 2.
Incubation period under plastic conditions:
Figure GDA0002230278860000082
the foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims (4)

1. The method for predicting the creep induction period containing residual stress under the plastic condition comprises the following steps:
s1: establishing a model: the model comprises a CT sample body, wherein a groove is formed in the front end of the middle of the CT sample body, a notch is formed in the rear part of the groove, an upper main load pin hole and a lower main load pin hole are further formed in the CT sample body, and the upper main load pin hole and the lower main load pin hole are arranged up and down correspondingly and are respectively arranged at the upper end and the lower end of the groove;
s2, firstly, the upper round pin and the lower round pin are used for carrying out compression loading with a preset size on the upper end and the lower end of the CT sample body, and then the upper round pin and the lower round pin are released, so that residual stress distribution can be generated near the notch of the CT sample body;
s3, inserting a prefabricated crack at the notch containing the residual stress to perform a creep test;
s4, applying main loads to the upper main load pin hole and the lower main load pin hole by using the pins, and performing a high-temperature creep test;
s5: necessary parameters required for calculating the incubation period of the CT sample containing residual stress can be obtained through creep finite element simulation, and the method mainly comprises the following steps of:
(1) firstly, calculating a stress intensity factor under composite loading, wherein the calculation formula is as follows:
Figure FDA0002230278850000011
in (I):
Figure FDA0002230278850000012
Figure FDA0002230278850000013
wherein:
Figure FDA00022302788500000110
is a stress intensity factor under the simulation calculation and only contains residual stress, and the unit is MPa (m)1/2)；
Figure FDA0002230278850000014
Is the main load stress intensity factor with the unit of MPa (m)1/2) (ii) a P is the primary load in N; b is the thickness of the specimen in mm, BnIs the net thickness of the sample, in mm; a/W is the length ratio of the prefabricated crack, a is the length of the prefabricated crack, and the horizontal straight line distance from the center of the upper main load pin hole to the rear end of the prefabricated crack is adopted, and the unit is mm; w is the nominal sample width, and the horizontal linear distance from the circle center of the upper main load pin hole to the rear end of the CT sample body is adopted, and the unit is mm; f (a/W) is the geometric coefficient of the CT sample and is only related to a/W; v is a dimensionless plastic related term calculated as follows:
Figure FDA0002230278850000015
in (II) V0Is a non-dimensional parameter, and the parameter is,
Figure FDA0002230278850000016
wherein:
Figure FDA0002230278850000017
is a plastic residual stress intensity factor with the unit of MPa (m)1/2)；
Figure FDA0002230278850000018
Is a stress intensity factor under the simulation calculation and only contains residual stress, and the unit is MPa (m)1/2)，
Figure FDA00022302788500000111
Using JSComputing，JSIs a fracture parameter under a residual stress field, and the unit is MPa.m;
Figure FDA0002230278850000019
wherein: e' is the effective modulus of elasticity: e ═ E/(1-v)2) E is the modulus of elasticity, v is the Poisson's ratio,
Figure FDA0002230278850000021
and JSExtracting by using finite element simulation results;
in (II) LrIs a dimensionless parameter describing the main load amplitude:
Figure FDA0002230278850000022
wherein: sigmayIs yield strength, related to material properties, in MPa,
Figure FDA0002230278850000023
is the main load reference stress in MPa, calculated by the following formula:
Figure FDA0002230278850000024
wherein: n isLFor dimensionless crack aspect ratio parameters, the following is calculated:
Figure FDA0002230278850000025
constant number
Figure FDA0002230278850000026
(II):
Figure FDA0002230278850000027
Figure FDA0002230278850000028
is the stress intensity factor of the elastic main load,
Figure FDA0002230278850000029
is a plastic main load stress intensity factor with the unit of MPa (m)1/2)；
Figure FDA00022302788500000210
Calculating by using a finite element simulation result:
β describes the amplitude of residual stress, which is a dimensionless parameter;
Figure FDA00022302788500000211
Figure FDA00022302788500000212
is the secondary load reference stress, utilizes finite element simulation calculation,
in the step (II), Z is a dimensionless elastic following factor, a stress-strain relation is extracted from a finite element simulation result, and an equivalent creep strain increment is taken
Figure FDA00022302788500000213
Equivalent elastic strain increment
Figure FDA00022302788500000214
The ratio of (A) to (B):
Figure FDA00022302788500000215
(2) calculating the J integral value under the plastic composite stress field, wherein the calculation formula is as follows:
Figure FDA00022302788500000216
wherein: kIIs the composite stress intensity factor, E' is the effective modulus of elasticity: e ═ E/(1-v)2)；
(3) Then calculating the incubation period time t under the plastic stress fieldi HRRThe calculation formula is as follows:
Figure FDA0002230278850000031
(III) in (III): epsiloncritIs uniaxial creep toughness, which is related to material properties and has a unit of 1,
Figure FDA0002230278850000032
is the creep strain rate of change in h-1Related to the high temperature creep properties of the material, σP0Is the normalized stress in units of MPa,. epsilonP0Is the normalized strain with the unit of 1, α is the strain hardening coefficient, N is the strain hardening index, INIs a non-dimensional function related to N,
Figure FDA0002230278850000033
is a dimensionless function related to θ and N;
(III) in (III): d is the extended distance of the creep damage before the crack tip reaches 1 when the creep initiation occurs, namely the critical distance of the creep initiation, and the unit is mm;
(III) in (III): MSFHRRThe multiaxial stress factor under plastic condition is calculated according to the relationship of Cocks and Ashby:
Figure FDA0002230278850000034
n is a dimensionless creep stress hardening index, sinh is a hyperbolic sine function, hHRRThree degrees of plastic stress, in the plastic stress state:
Figure FDA0002230278850000035
wherein: theta is the crack tip angle, N is the dimensionless stress hardening index,
Figure FDA0002230278850000036
and
Figure FDA0002230278850000037
is a dimensionless function related to theta and N.
2. The method of predicting creep induction period with residual stress under plastic conditions as set forth in claim 1, wherein: d takes the grain size of the material under study.
3. The method of predicting creep induction period with residual stress under plastic conditions as set forth in claim 1, wherein: b isn＝B。
4. The method of predicting creep induction period with residual stress under plastic conditions as set forth in claim 1, wherein: the finite element simulation was computationally simulated using ABAQUS6.14,
Figure FDA0002230278850000038
JS、
Figure FDA0002230278850000039
the extraction process of Z comprises the following steps:
(1) firstly, establishing a finite element model of a pre-compressed loaded CT sample, setting elastic-plastic parameters in a material property module, setting compression load in a load module, and setting a constraint condition: including symmetry condition and fixed condition, set up the rigid contact of compression round pin and sample upper and lower surface in the contact module, set up output parameter in the analysis step module: stress value, dividing grids in the grid module;
(2) the task calculation is submitted in the operation module to obtain the calculation result of the residual stress, and in the result file, two variables can be directly extracted from the field variablesReference stress of secondary load
Figure FDA0002230278850000041
(3) Establishing a sample model with the same size, carrying out a main load tensile test, setting elastic-plastic creep parameters at high temperature in a material property module, dividing grids in a grid module, setting rigid contact between a tensile pin and a pin hole in a contact module, inserting a prefabricated crack in the model, and setting output parameters in an analysis step module: stress strain value, stress intensity factor K value, rupture parameter J integral value set up tensile load in the load module to and restrain the condition: the method comprises the steps of (1) introducing the calculated residual stress into a preloading stress field under a symmetrical condition and a fixed condition;
(4) submitting task calculation in the operation module to obtain the calculation result of the creep-tensile experiment containing residual stress, and acquiring the stress intensity factor which is only under the residual stress and is subjected to simulation calculation from historical variables when tensile load is not applied after the crack is inserted in a result file
Figure FDA0002230278850000042
And residual stress rupture parameter JSAt the initial moment of applying the tensile load, the stress intensity factor of the elastic main load can be obtained
Figure FDA0002230278850000043
Obtaining the change curve of the equivalent stress along with the total strain increment from the historical variables, and obtaining the equivalent creep strain increment from the curve
Figure FDA0002230278850000044
Increment of equivalent elastic strain
Figure FDA0002230278850000045
Thereby obtaining the elastic tracking factor Z.
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Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101379381A (en) * 2006-02-01 2009-03-04 新日本制铁株式会社 Breaking prediction method
CN103217346A (en) * 2013-04-01 2013-07-24 北京航空航天大学 Method for measuring high-temperature creep crack growth threshold value of material
CN103323343A (en) * 2013-06-17 2013-09-25 四川大学 Judgment method and prediction method for creep failure life of polymer material
WO2014155558A1 (en) * 2013-03-27 2014-10-02 中国電力株式会社 Method for predicting remaining creep life of heat- and pressure-degraded product, and standard curve preparation method using this prediction method
JP5851197B2 (en) * 2011-10-25 2016-02-03 日立Ｇｅニュークリア・エナジー株式会社 Stress corrosion cracking life evaluation method for metal materials and inspection plan formulation system for structures used in corrosive water environment
CN105806715A (en) * 2016-03-10 2016-07-27 大连理工大学 High-temperature creep deformation prediction method
CN105842087A (en) * 2016-03-03 2016-08-10 安阳工学院 Designing and prediction method for converting high-temperature stress relaxation data into creep data
CN106529017A (en) * 2016-11-08 2017-03-22 华南理工大学 High-temperature creep deformation prediction and creep damage analysis method for high-chrome steel component
CN106557630A (en) * 2016-11-21 2017-04-05 中国石油大学(华东) A kind of creep impairment life-span prediction method of material under multi-axis stress state
CN106568655A (en) * 2016-10-28 2017-04-19 沈阳工业大学 Method used for predicting creep life of heat-resisting alloy

Patent Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101379381A (en) * 2006-02-01 2009-03-04 新日本制铁株式会社 Breaking prediction method
JP5851197B2 (en) * 2011-10-25 2016-02-03 日立Ｇｅニュークリア・エナジー株式会社 Stress corrosion cracking life evaluation method for metal materials and inspection plan formulation system for structures used in corrosive water environment
WO2014155558A1 (en) * 2013-03-27 2014-10-02 中国電力株式会社 Method for predicting remaining creep life of heat- and pressure-degraded product, and standard curve preparation method using this prediction method
CN103217346A (en) * 2013-04-01 2013-07-24 北京航空航天大学 Method for measuring high-temperature creep crack growth threshold value of material
CN103323343A (en) * 2013-06-17 2013-09-25 四川大学 Judgment method and prediction method for creep failure life of polymer material
CN105842087A (en) * 2016-03-03 2016-08-10 安阳工学院 Designing and prediction method for converting high-temperature stress relaxation data into creep data
CN105806715A (en) * 2016-03-10 2016-07-27 大连理工大学 High-temperature creep deformation prediction method
CN106568655A (en) * 2016-10-28 2017-04-19 沈阳工业大学 Method used for predicting creep life of heat-resisting alloy
CN106529017A (en) * 2016-11-08 2017-03-22 华南理工大学 High-temperature creep deformation prediction and creep damage analysis method for high-chrome steel component
CN106557630A (en) * 2016-11-21 2017-04-05 中国石油大学(华东) A kind of creep impairment life-span prediction method of material under multi-axis stress state

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
《Evaluation of constraint effects on creep crack growth by experimental investigation and numerical simulation》;Zhao L;《Engineering Fracture Mechanics》;20121231;全文 *
《焊后热处理对P92钢管道焊接残余应力场的影响》;徐连勇;《焊接学报》;20100331;第31卷(第3期);全文 *

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