CN110516269A - A kind of optimization for submarine pipeline engineering critical evaluation refers to strain process - Google Patents
A kind of optimization for submarine pipeline engineering critical evaluation refers to strain process Download PDFInfo
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Abstract
The present invention discloses a kind of optimization for submarine pipeline engineering critical evaluation with reference to strain process, is based on finite element analysis, introduces the f factor, has searched out fracture response J/ σ0T and apparent strain εnBetween relationship.Pass through a series of derivation in conjunction with Ramberg-Osgood material constitutive relation and with reference to Strain Method failure analysis curvilinear equation, finally obtained the analytical expression with reference to strain, to optimize with reference to Strain Method, realizes more accurate engineering critical assessment.
Description
Technical field
The invention belongs to field of engineering technology, particularly belong to pipe ring during sea-bottom oil-gas pipeline pipe crimping is laid with and is on active service
To the engineering critical assessment technology of face crack, engineering critical assessment is carried out by implementing the technology, it can be determined that pipeline circumferential weld
Whether face crack will lead to pipeline failure, to judge whether that safe military service can be continued.
Background technique
With the continuous exploitation of landing field fossil resources, the quantity of land fossil resources is fewer and fewer.Ocean fossil resources obtain
The attention of people is arrived.However due to the complexity of deep-marine-environment, deep-sea exploitation has very big technical difficulty.Pipeline is as deep
The main carriers of extra large oil gas transport, q&r are most important.Currently used pipe crimping laying method has J-type laying
Method, S type laying method and pipe crimping laying method.Wherein pipe crimping laying method efficiency highest may be implemented to weld on the bank and offshore laying.Number
Mitron section connects into thousands of meters of pipeline after welding, is then wound on large-scale winding up roller.Laying is transported to by pipe laying barge
Place, the processes such as uncoiling, alignment are laid with.During pipe crimping is laid with and is on active service, the name that pipeline will receive 1-4% is answered
Change and certain internal pressure.It is lacked due to inevitably generating the harmfulness such as incomplete fusion, lack of penetration, crackle in welding process
It falls into.Limitation of these defects due to non-destructive testing technology principle and testing staff's level, partially oriented special tiny flaw meeting
Missing inspection.It is therefore desirable to carry out engineering critical assessment to pipeline.Submarine pipeline strain control is directly utilized in conventional reference Strain Method
The engineering critical assessment to pipeline may be implemented in the natural boundary conditions of system.However since this method directly uses apparent strain generation
For reference strain, thus it may be only available for the lesser Evaluation of Cracks of depth, it is impossible to be used in the assessment of more serious crackle.Because for
More serious crackle is very big with reference to the deviation of strain and apparent strain.Directly replace carrying out with reference to strain with apparent strain
Assessment is not accurate enough.There is presently no propose containing the analytic formula that accurately reference strains under pipeline internal pressure conditions.
Summary of the invention
It is an object of the invention to overcome the deficiencies of the prior art and provide a kind of for submarine pipeline engineering critical evaluation
Optimization refers to strain process, strains formula by the reference derived, improves conventional reference Strain Method, to realize to seabed
Accurate engineering critical assessment of the oil-gas pipeline under internal pressure conditions.
Technical purpose of the invention is achieved by following technical proposals:
A kind of optimization for submarine pipeline engineering critical evaluation refers to strain process, carries out as steps described below:
Determine the fracture toughness K of materialmat, solve the stress strength factor K of structureI, thus according to formula Kr=KI/Kmat
Obtain Kr;According to formulaIt solves and refers to strain stressref, then
According to reference strain stressrefWith formula Dr=εref/ε0Determine evaluation point coordinate Dr;
Meanwhile according to formulaWith formula f
(Dr)=(2EDrε0/σref)-0.5(Dr> 1) draw failure assessment curve figure (FAC curve, i.e., the critical song for referring to Strain Method
Line);
By evaluation point (Dr,Kr) position be compared with FAC curve, if evaluation point is located above curve, structure is not
Safety;If evaluation point is located at below curve, structure safety.
Above-mentioned calculating is applicable in following condition with reference to the formula of strain: it be 0.1-0.4, D/t is 10-that a/t, which is 0.1-0.4, a/c,
30, n be 10-20, nrFor 0-0.8, εn> ε0。
Above-mentioned calculating is with reference to f in strain formula, by formula J/ σ0T=f εnIt is calculated, to be based on finite element business software
Abaqus calculates analysis, introduces the f factor in the solution formula of reference strain, has searched out fracture response J/ σ0T and name
Strain stressnBetween linear relationship: J/ σ0T=f εn.Wherein J integral can be calculated by business software Abaqus and be solved, apparent strain
εnFor the strain born in pipeline pipe crimping process of deployment, σ0For yield strength, unit MPa;T is pipeline wall thickness, unit mm.
Above-mentioned calculating is checked in reference to f in strain formula by table 1- table 3 in embodiment, and 3 data of table 1- table can also be passed through
Linear interpolation, which calculates, to be obtained.
It calculates and analyzes the present invention is based on finite element business software Abaqus, introduce f in the solution formula of reference strain
The factor has searched out fracture response J/ σ0T and apparent strain εnBetween linear relationship: J/ σ0T=f εn.Wherein J integral is by quotient
It is calculated and is solved with software Abaqus.Apparent strain εnFor the strain born in pipeline pipe crimping process of deployment.In conjunction with Ramberg-
A series of derivation is passed through in Osgood material constitutive relation and reference Strain Method failure analysis curvilinear equation (i.e. formula 1-2), most
The analytical expression with reference to strain has been obtained eventually, to optimize with reference to Strain Method, realizes more accurate engineering critical assessment.
Detailed description of the invention
Fig. 1 is the Failure Assessment figure (FAD) that Strain Method is referred to used in the present invention.
Fig. 2 is face crack schematic diagram in the present invention.
Fig. 3 is to assess schematic diagram with reference to Strain Method in the present invention.
Fig. 4 is in the present invention with reference to strain and apparent strain value contrast schematic diagram.
Fig. 5 is the verifying schematic diagram (1) that improvement of the invention refers to Strain Method.
Fig. 6 is the verifying schematic diagram (2) that improvement of the invention refers to Strain Method.
Specific embodiment
Technical solution of the present invention is further illustrated combined with specific embodiments below.
It as shown in Fig. 1, mainly include failure assessment curve (FAC), K with reference to the Failure Assessment figure (FAC) of Strain Methodr
And Dr, FAC curvilinear equation, (according to R6 standard), respectively corresponds stretch section and plasticity section, K as shown in formula 1 and formula 2rAnd Dr's
Calculation is respectively as shown in formula 3 and formula 4.
Wherein KrIt is immeasurable rigid for breaking factor;DrFor the plastic instability factor, dimensionless;σrefFor Reference Stress, unit is
MPa;σ0For yield strength, unit MPa.
(2)f(Dr)=(2EDrε0/σref)-0.5(Dr> 1) formula 2
Wherein E is elasticity modulus, unit MPa, ε0For yield strain, dimensionless.
(3)Kr=KI/KmatFormula 3
Wherein KIFor stress intensity factor, unit isKmatFor material fracture toughness, unit is
(4)Dr=εref/ε0Formula 4
Wherein εrefFor with reference to strain, dimensionless.
(i.e. conventional reference Strain Method) is by ε in the prior artrefDirectly use apparent strain εnInstead of being incited somebody to action that is, in formula 4
εrefDirectly use apparent strain εnIt is not accurate enough for the assessment result obtained compared with deep torn grain instead of carrying out the calculating of Dr.The present invention
It is middle to propose to carry out using formula 5 that obtained reference is strained substitution formula 4 and is calculated, such as formula 5 is used with reference to strain calculation
Shown in reference to strain formula carry out assessing available more accurate assessment result.
Wherein α is material parameter, α=1;σ0For yield strength, unit MPa;ε0For yield strain, dimensionless;εnIt runs after fame
Justice strain, dimensionless;T is pipeline wall thickness, unit mm;F is a parameter introducing in formulation process, dimensionless,
Value is as shown in table 1-3;N is strain hardening exponent, dimensionless;J integral representation crack driving force for propagation, JeFor the elasticity of J integral
Component can be acquired by formula 8, can also be by (J integral is calculated by business software Abaqus to be solved), J is calculatedeWith J unit
It is Mpamm.
1 f value of table is based on n=10, a/t=0.1-0.4, a/c=0.1-0.4, D/t=10-30, nr=0-0.8
Such as f=0.649, corresponding n=10, a/t=0.1, a/c=0.1, D/t=10, nr=0;F=0.435, corresponding n
=10, a/t=0.1, a/c=0.4, D/t=30, nr=0.2.
2 f value of table is based on n=15, a/t=0.1-0.4, a/c=0.1-0.4, D/t=10-30and nr=0-0.8
Such as f=11.497, corresponding n=15, a/t=0.4, a/c=0.1, D/t=10, nr=0;F=0.704, it is corresponding
N=15, a/t=0.1, a/c=0.4, D/t=10, nr=0.4.
3 f value of table is based on n=20, a/t=0.1-0.4, a/c=0.1-0.4, D/t=10-30and nr=0-0.8
Such as f=1.727, corresponding n=20, a/t=0.2, a/c=0.1, D/t=10, nr=0;F=4.599, corresponding n
=20, a/t=0.4, a/c=0.4, D/t=20, nr=0.2.
Wherein a is pipe surface crack depth, unit mm;C is half length of face crack, unit mm;D is outside pipeline
Diameter, unit mm;T is pipeline wall thickness, unit mm;nrFor the amount for characterizing pipeline internal pressure, dimensionless is determined by formula 6-7.
nr=σh/σ0Formula 6
Wherein σhFor the circumferential stress that pipeline is born, unit MPa, σ0For yield strength, unit MPa is true by formula 7
It is fixed
σh=P (D-2t)/2t formula 7
Wherein P is that pipeline bears internal pressure size, unit MPa.
Wherein ν is Poisson's ratio, dimensionless, KIFor stress intensity factor, unit isE is elasticity modulus,
MPa。
It is calculated and is analyzed based on finite element business software Abaqus, introduced the f factor in the solution formula of reference strain, seek
Have found fracture response J/ σ0T and apparent strain εnBetween linear relationship: J/ σ0T=f εn.Wherein J integral can be by commercial soft
Part Abaqus, which is calculated, to be solved, apparent strain εnFor the strain born in pipeline pipe crimping process of deployment, in conjunction with Ramberg-
Osgood material constitutive relation and reference Strain Method failure analysis curvilinear equation (i.e. formula 1-2), have finally obtained with reference to strain
Analytical expression realize more accurate engineering critical assessment to optimize with reference to Strain Method.
When being evaluated, the fracture toughness K of material is determinedmat, solve the stress strength factor K of structureI, thus according to
Formula Kr=/KIObtain Kr;According to formulaSolve ginseng
Examine strain stressref, further according to reference strain stressrefWith formula Dr=εref/ε0Determine evaluation point coordinate Dr;
Meanwhile according to formulaWith formula f
(Dr)=(2EDrε0/σref)-0.5(Dr> 1) draw failure assessment curve figure (FAC curve, i.e., the critical song for referring to Strain Method
Line);
By evaluation point (Dr,Kr) position be compared with FAC curve, if evaluation point is located above curve, structure is not
Safety;If evaluation point is located at below curve, structure safety, as shown in Fig. 3.
As shown in Fig. 4, for different pipeline configuration and crack size, the reference of proposition is strained into formula and name is answered
Variate compares, with reference to only special case situation equal with apparent strain is strained, for higher a/t and lower D/t value
(being equivalent to severe crack) is greater than apparent strain with reference to strain, and conventional reference Strain Method can obtain non-conservative assessment at this time;It is right
In lower a/t and higher D/t (being equivalent to crackle), it is less than apparent strain with reference to strain, at this time conventional reference Strain Method
It can obtain overly conservative assessment.
As depicted in figures 5 and 6, the embodiment verifying that the formula 5 proposed according to the present invention obtains, assumes fracture in figure
Toughness JICIt is equal with crack driving force for propagation J, therefore obtained evaluation point result should be fallen on curve.Conventional method is in pipe
Road Crack Parameters a/t=0.1, a/c=0.1, D/t=30, εnWhen=0-4% (Fig. 5), evaluation point is substantially all in FAC curve
Top, and work as a/t=0.4, a/c=0.1, D/t=10, εnWhen=0-4% (Fig. 6), obtained evaluation point all exists substantially
The lower section of FAC curve.In comparison, the evaluation point obtained according to the formula of proposition 5 all on curve, can prove this substantially
Formula substantially increases the accuracy of engineering critical assessment.
Physics scale used herein, as follows:
Illustrative description has been done to the present invention above, it should explanation, the case where not departing from core of the invention
Under, any simple deformation, modification or other skilled in the art can not spend the equivalent replacement of creative work equal
Fall into protection scope of the present invention.
Claims (3)
1. a kind of optimization for submarine pipeline engineering critical evaluation refers to strain process, which is characterized in that as steps described below
It carries out:
Determine the fracture toughness K of materialmat, solve the stress strength factor K of structureI, thus according to formula Kr=KI/KmatIt obtains
Kr;According to formulaIt solves and refers to strain stressref, then root
According to reference strain stressrefWith formula Dr=εref/ε0Determine evaluation point coordinate Dr;
Meanwhile according to formulaWith formula f (Dr)=
(2EDrε0/σref)-0.5(Dr> 1) draw the failure assessment curve figure (FAC curve, i.e. critical curve) for referring to Strain Method;
By evaluation point (Dr,Kr) position be compared with FAC curve, if evaluation point is located above curve, structure is uneasy
Entirely;If evaluation point is located at below curve, structure safety;Wherein KrIt is immeasurable rigid for breaking factor;DrFor the plastic instability factor,
Dimensionless;σrefFor Reference Stress, unit MPa;σ0For yield strength, unit MPa;E is elasticity modulus, unit MPa, ε0
For yield strain, dimensionless;KIFor stress intensity factor, unit isKmatFor material fracture toughness, unit isεrefFor with reference to strain, dimensionless;α is material parameter, α=1;σ0For yield strength, unit MPa;ε0It is in the wrong
Clothes strain, dimensionless;εnFor apparent strain, dimensionless;T is pipeline wall thickness, unit mm;N is strain hardening exponent, immeasurable
Guiding principle;J integral representation crack driving force for propagation, JeFor the component of elasticity of J integral, JeIt is Mpamm with J unit;F is by formula J/
σ0T=f εnIt is calculated, dimensionless, is obtained with calculating analysis based on finite element business software Abaqus.
2. a kind of optimization for submarine pipeline engineering critical evaluation according to claim 1 refers to strain process, special
Sign is, calculates the formula with reference to strain and is applicable in following condition: it be 0.1-0.4, D/t is 10-30, n that a/t, which is 0.1-0.4, a/c,
For 10-20, nrFor 0-0.8, εn> ε0, a is face crack depth, unit mm;T is pipeline wall thickness, unit mm;C is that crackle half is long
Degree, unit mm;D is outer diameter tube, unit mm;N is strain hardening exponent, dimensionless;nrFor circumferential stress ratio, dimensionless;εnFor
Apparent strain, dimensionless;ε0For yield strain, dimensionless.
3. a kind of optimization for submarine pipeline engineering critical evaluation according to claim 1 refers to strain process, special
Sign is that f is checked in by following table 1-table 3, is obtained by the linear interpolation calculation of 3 data of table 1- table.
1 f value of table is based on n=10, a/t=0.1-0.4, a/c=0.1-0.4, D/t=10-30, nr=0-0.8
2 f value of table is based on n=15, a/t=0.1-0.4, a/c=0.1-0.4, D/t=10-30and nr=0-0.8
3 f value of table is based on n=20, a/t=0.1-0.4, a/c=0.1-0.4, D/t=10-30and nr=0-0.8
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CN111717604A (en) * | 2020-05-19 | 2020-09-29 | 中交第四航务工程局有限公司 | Method for setting water inlet section of land outbound track of large-diameter ultra-long HDPE pipeline |
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Cited By (3)
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CN111539142A (en) * | 2020-04-20 | 2020-08-14 | 中车青岛四方机车车辆股份有限公司 | Method and system for calculating crack propagation driving force of pipeline |
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CN111717604A (en) * | 2020-05-19 | 2020-09-29 | 中交第四航务工程局有限公司 | Method for setting water inlet section of land outbound track of large-diameter ultra-long HDPE pipeline |
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