CN111324985B - Method for evaluating fatigue life of continuous pipe containing groove-shaped scratch defects - Google Patents

Method for evaluating fatigue life of continuous pipe containing groove-shaped scratch defects Download PDF

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CN111324985B
CN111324985B CN202010261455.4A CN202010261455A CN111324985B CN 111324985 B CN111324985 B CN 111324985B CN 202010261455 A CN202010261455 A CN 202010261455A CN 111324985 B CN111324985 B CN 111324985B
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defect
strain
shaped scratch
groove
continuous pipe
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CN111324985A (en
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刘少胡
钟虹
周浩
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Yangtze University
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Abstract

The invention relates to an evaluation method for fatigue life of a continuous pipe containing groove-shaped scratch defects, and belongs to the field of safety evaluation of service life of pipe columns. The invention confirms through screening of the outer wall groove-shaped scratch defect and the inner wall groove-shaped scratch defect, detects the geometric parameters of the shape of the scratch defect, and calculates the fatigue life of the continuous pipe containing the outer wall groove-shaped scratch defect and the inner wall groove-shaped scratch defect; and the step of three-level evaluation is carried out on the continuous pipe containing the outer wall groove-shaped scratch defect and the inner wall groove-shaped scratch defect, so that the defect of fatigue life evaluation of the conventional continuous pipe containing the groove-shaped defect is overcome, the cost is saved, the economic benefit is increased, the use risk of the continuous pipe is reduced, and the method has great production practice significance.

Description

Method for evaluating fatigue life of continuous pipe containing groove-shaped scratch defects
Technical Field
The invention relates to an evaluation method for fatigue life of a continuous pipe containing groove-shaped scratch defects, and belongs to the field of safety evaluation of service life of pipe columns.
Background
The Continuous Tube (CT) is a jointless tube formed by welding a plurality of sections of steel belts, and is wound on a roller with a larger diameter so as to be convenient for transportation and operation. Compared with the traditional drilling and completion mode, the continuous pipe does not need to additionally stand a derrick and break out in the using process, so that the working period is greatly shortened, the labor intensity is reduced, the exploitation cost is reduced, and the cost can be saved by 25% -40%. The continuous pipe technology has become a new technology which is increasingly perfect in the field of petroleum and natural gas exploration and development, and is known as universal operation equipment due to the wide application range and convenient use of the continuous pipe operation equipment.
The coiled tubing is subjected to 6 bend-straight alternating deformations during one start and stop operation, and when the deformations far exceed the elastic limit of the material, the coiled tubing is forced to enter a plastic state, so that the fatigue of the coiled tubing belongs to the category of typical low cycle fatigue. Mechanical damage is often unavoidable during transportation and operation of the coiled tubing, in the form of groove scratches, spherical indentations, etc., which are one of the major forms of defects. At present, no perfect method is available for evaluating the residual life of the groove-shaped scratch defect, and in the field use process, if the scratch defect occurs, the whole coiled continuous tube is directly scrapped, so that the continuous tube with the groove-shaped defect cannot continuously exert the residual fatigue life, the use cost is increased, and the operation risk is increased. Therefore, an evaluation method is urgently needed to make up for the defect of the fatigue life evaluation of the continuous pipe with groove-shaped scratch defects at present, so that the continuous pipe with the defects is correctly used, and the use risk is reduced.
Disclosure of Invention
The invention aims to provide a fatigue life evaluation method for a continuous pipe with groove-shaped scratch defects, which can perform accurate fatigue life safety evaluation on the continuous pipe with groove-shaped scratch defects, thereby correctly using the continuous pipe with defects and reducing the use risk.
The technical scheme of the invention is as follows:
a method for evaluating the fatigue life of a continuous pipe containing groove-shaped scratch defects is characterized by comprising the following steps: it comprises the following steps:
1) Firstly, screening and confirming the groove-shaped scratch defect of the outer wall and the groove-shaped scratch defect of the inner wall on a service continuous pipe;
2) Detecting geometric shape parameters of the outer wall groove-shaped scratch defect and the inner wall groove-shaped scratch defect; the defect parameters of the outer wall groove-shaped scratch defect and the inner wall groove-shaped scratch defect comprise a defect axial angle beta, a defect depth a, a defect length c, a defect width b, rounded corners R around scratches, circumferential distribution of defects and the number of the circumferential distribution of the defects, and ice utilizes defect detection equipment to measure the parameters of the outer wall groove-shaped scratch defect and the inner wall groove-shaped scratch defect;
3) Sensitive defect parameters, preferably of the outer wall groove scratch defect and the inner wall groove scratch defect; obtaining sensitivity parameters, namely the defect axial angle beta, the defect depth a, the defect length c, the defect width b, the rounded corners R of the periphery of scratches, the circumferential distribution of the defects and the number of the circumferential distribution of the defects, from the sensitivity parameters in sequence, namely the defect depth a, the defect width b, the defect axial angle beta and the defect length c based on an orthogonal test method;
4) Theoretically calculating the fatigue life of the continuous pipe containing the groove-shaped scratch defects of the outer wall and the groove-shaped scratch defects of the inner wall on the basis of considering the groove-shaped defect sensitive parameters;
5) Performing three-level evaluation on the continuous pipe containing the outer wall groove-shaped scratch defect and the inner wall groove-shaped scratch defect; namely, three-stage evaluation was performed on a continuous pipe containing a groove-shaped scratch defect. Compared with a complete continuous pipe under the same working condition, the fatigue life is reduced by 50 percent and is directly scrapped, the fatigue life is reduced by 20-50 percent and is finely evaluated, and the fatigue life is reduced by less than 20 percent and is roughly evaluated;
the method for calculating the fatigue life of the continuous tube containing the groove-shaped scratch defect of the outer wall and the groove-shaped scratch defect of the inner wall in the step 4) comprises the following steps:
when the inner surface and the outer surface of the continuous pipe are provided with an outer wall groove-shaped scratch defect and an inner wall groove-shaped scratch defect, the influence of the outer wall groove-shaped scratch defect and the inner wall groove-shaped scratch defect on the fatigue life is considered when the fatigue life model of the continuous pipe is built; radial stress of continuous pipe under internal pressure based on thick-wall cylinder theory
Figure 216931DEST_PATH_IMAGE001
Hoop stress->
Figure 134071DEST_PATH_IMAGE002
And axial stress->
Figure 569600DEST_PATH_IMAGE003
：
Figure 964810DEST_PATH_IMAGE004
Wherein:
Figure 779182DEST_PATH_IMAGE005
the outer radius of the continuous pipe is mm;/>
Figure 601644DEST_PATH_IMAGE006
is the inner radius, mm; />
Figure 399836DEST_PATH_IMAGE007
Is the internal pressure, MPa; r is any radius, mm.
Based on stress analysis andvon Misesthe critical point for yielding first is always the inner surface of the coiled tubing, as is the criterion
Figure 598736DEST_PATH_IMAGE008
；
Figure 267615DEST_PATH_IMAGE009
Total strain by bending action according to Remberg-Osgood elastoplastic stress-strain relationship
Figure 667503DEST_PATH_IMAGE010
Is elastic strain->
Figure 421833DEST_PATH_IMAGE011
And plastic strain->
Figure 158845DEST_PATH_IMAGE012
And (2) sum:
Figure 213388DEST_PATH_IMAGE013
/>
wherein:Dthe diameter of the continuous pipe is mm;
Figure 643233DEST_PATH_IMAGE014
is a bending radius, mm;Eis elastic modulus, MPa; />
Figure 884858DEST_PATH_IMAGE015
Is the yield limit, MPa;
bending yieldThe generated axial force is the main cause of plastic strain, internal pressure and axial stress under bending action
Figure 159982DEST_PATH_IMAGE016
The method comprises the following steps:
Figure 462175DEST_PATH_IMAGE017
axial stress resulting from bending can be obtained from the Holomon relationship of stress to plastic strain
Figure 797341DEST_PATH_IMAGE018
Hoop strain, axial strain, and radial strain under compressive bending coupling load:
Figure 526263DEST_PATH_IMAGE019
wherein:
Figure 136235DEST_PATH_IMAGE020
is the circumferential strain; />
Figure 634213DEST_PATH_IMAGE021
Is axial strain; />
Figure 405860DEST_PATH_IMAGE022
Is radial strain; />
Figure 763023DEST_PATH_IMAGE023
Is the cyclic strain hardening coefficient, MPa; />
Figure 645528DEST_PATH_IMAGE024
Is a cyclic strain hardening index;
in the plastic deformation process of the continuous pipe, the assumption of unchanged volume is adopted, and the equivalent plastic strain under the coupling load
Figure 998012DEST_PATH_IMAGE025
The method comprises the following steps:
Figure 471719DEST_PATH_IMAGE026
the strain-life equation is as follows using a Brown-Miller fatigue life theoretical model:
Figure 909653DEST_PATH_IMAGE027
Figure 330271DEST_PATH_IMAGE028
maximum shear strain:
Figure 458632DEST_PATH_IMAGE029
positive strain of maximum shear strain plane:
Figure 572082DEST_PATH_IMAGE030
to consider the influence of other parameters besides sensitive parameters on the fatigue life of continuous pipe, a correction coefficient is introduced
Figure 497313DEST_PATH_IMAGE031
：
Figure 721621DEST_PATH_IMAGE032
Wherein:c 0 is the depth of the pit defect;N f the number of fatigue bending times of the continuous pipe;
maximum shear strain after introducing correction coefficient and positive strain of maximum shear strain plane:
Figure 314276DEST_PATH_IMAGE033
the final defect-containing continuous pipe fatigue life calculation model is as follows:
Figure 598627DEST_PATH_IMAGE034
the invention has the beneficial effects that
Compared with the prior art, the method and the device have the advantages that the shape geometric parameters of the scratch defects are detected and the fatigue life of the continuous tube containing the outer wall groove scratch defects and the inner wall groove scratch defects is calculated through screening and confirming of the outer wall groove scratch defects and the inner wall groove scratch defects; and carrying out three-level evaluation on the continuous pipe containing the outer wall groove-shaped scratch defect and the inner wall groove-shaped scratch defect; the method overcomes the defect of the fatigue life assessment of the existing continuous pipe with the groove-shaped defects, saves cost, increases economic benefit, reduces the use risk of the continuous pipe, and has great production practice significance.
Drawings
FIG. 1 is a flow chart of a method for evaluating fatigue life of a continuous pipe containing groove-shaped scratch defects;
FIG. 2 is a schematic three-dimensional semi-sectional view of a groove-shaped scratch defect;
FIG. 3 is a schematic top view of a groove-shaped scratch defect;
FIG. 4 is a schematic illustration of a coiled tubing bending deformation;
FIG. 5 is a schematic illustration of a coiled tubing cross-section force;
in the figure: 1. the continuous pipe, 2, the groove-shaped scratch defect of the outer wall, 3, the groove-shaped scratch defect of the inner wall.
The specific embodiment is as follows:
in order to better understand the aspects of the present invention, the present invention will be described in further detail with reference to the drawings and embodiments.
Referring to fig. 1 to 5, the method for evaluating the fatigue life of the continuous pipe containing the groove-shaped scratch defects provided by the invention comprises the following steps:
firstly, screening and confirming an outer wall groove-shaped scratch defect 2 and an inner wall groove-shaped scratch defect 3 in a service continuous pipe 1;
secondly, detecting geometric parameters of the shapes of the outer wall groove-shaped scratch defect 2 and the inner wall groove-shaped scratch defect 3;
thirdly, preference is given to sensitive defect parameters of the outer wall groove-shaped scratch defect 2 and the inner wall groove-shaped scratch defect 3;
fourthly, theoretically calculating the fatigue life of the continuous tube 1 containing the outer wall groove-shaped scratch defect 2 and the inner wall groove-shaped scratch defect 3;
fifthly, carrying out three-level evaluation on the continuous tube 1 containing the outer wall groove-shaped scratch defect 2 and the inner wall groove-shaped scratch defect 3;
in the second step, the defect parameters of the outer wall groove-shaped scratch defect 2 and the inner wall groove-shaped scratch defect 3 comprise a defect axial angle beta, a defect depth a, a defect length c, a defect width b, rounded corners R around scratches, circumferential distribution of defects and the number of the circumferential distribution of the defects, and the defect detection equipment is used for measuring the parameters of the outer wall groove-shaped scratch defect 2 and the inner wall groove-shaped scratch defect 3;
in the third step, based on an orthogonal test method, sensitive parameters in the defect axial angle beta, the defect depth a, the defect length c, the defect width b, the rounded corners R around scratches, the circumferential distribution of defects and the number of the circumferential distribution of the defects are obtained, wherein the sensitive parameters are sequentially the defect depth a, the defect width b, the defect axial angle beta and the defect length c;
in the fourth step, the fatigue life method of the continuous pipe 1 containing the groove defect is calculated on the basis of considering the groove defect sensitivity parameter as follows:
when the inner and outer surfaces of the continuous tube 1 are provided with the outer wall groove-shaped scratch defect 2 and the inner wall groove-shaped scratch defect 3, the influence of the outer wall groove-shaped scratch defect 2 and the inner wall groove-shaped scratch defect 3 on the fatigue life is considered when the fatigue life model of the continuous tube 1 is established. Radial stress of continuous tube 1 under internal pressure based on thick-wall cylinder theory
Figure 11154DEST_PATH_IMAGE035
Hoop stress->
Figure 39152DEST_PATH_IMAGE036
And axial stress->
Figure 627260DEST_PATH_IMAGE037
：
Figure 816933DEST_PATH_IMAGE038
Wherein:
Figure 716755DEST_PATH_IMAGE039
the outer radius of the continuous pipe 1 is mm; />
Figure 814024DEST_PATH_IMAGE040
Is the inner radius, mm; />
Figure 115693DEST_PATH_IMAGE041
Is the internal pressure, MPa; r is any radius, mm.
The critical point at which yield is first generated is always the inner surface of the continuous tube 1, according to stress analysis and von Mises criteria
Figure 476267DEST_PATH_IMAGE042
；
Figure 863386DEST_PATH_IMAGE043
Total strain by bending action according to Remberg-Osgood elastoplastic stress-strain relationship
Figure 888980DEST_PATH_IMAGE044
Is elastically strained
Figure 779575DEST_PATH_IMAGE045
And plastic strain->
Figure 576630DEST_PATH_IMAGE046
And (2) sum: />
Figure 185466DEST_PATH_IMAGE047
Wherein:Dthe outer diameter of the continuous pipe 1 is mm;
Figure 890117DEST_PATH_IMAGE048
is a bending radius, mm;Eis elastic modulus, MPa; />
Figure 900798DEST_PATH_IMAGE049
Is the yield limit, MPa.
The axial force generated by bending is the main cause of plastic strain, internal pressure and axial stress under bending
Figure 868754DEST_PATH_IMAGE050
The method comprises the following steps:
Figure 964886DEST_PATH_IMAGE051
axial stress resulting from bending can be obtained from the Holomon relationship of stress to plastic strain
Figure 83015DEST_PATH_IMAGE052
Hoop strain, axial strain, and radial strain under compressive bending coupling load:
Figure 948203DEST_PATH_IMAGE053
wherein:
Figure 87060DEST_PATH_IMAGE054
is the circumferential strain; />
Figure 201646DEST_PATH_IMAGE055
Is axial strain; />
Figure 451362DEST_PATH_IMAGE056
Is radial strain; />
Figure 436636DEST_PATH_IMAGE057
Is the cyclic strain hardening coefficient, MPa; />
Figure 746394DEST_PATH_IMAGE058
Is a cyclic strain hardening index.
In the plastic deformation process of the continuous pipe 1, the assumption of unchanged volume is adopted, and the equivalent plastic strain under the coupling load
Figure 472911DEST_PATH_IMAGE059
The method comprises the following steps:
Figure 526317DEST_PATH_IMAGE060
the strain-life equation is as follows using a Brown-Miller fatigue life theoretical model:
Figure 366097DEST_PATH_IMAGE061
Figure 846757DEST_PATH_IMAGE062
Figure 670357DEST_PATH_IMAGE063
/>
Figure 527454DEST_PATH_IMAGE064
to consider the influence of other parameters besides sensitive parameters on the fatigue life of continuous pipe, a correction coefficient is introduced
Figure 221741DEST_PATH_IMAGE065
：
Figure 873302DEST_PATH_IMAGE066
Wherein:
Figure 325143DEST_PATH_IMAGE067
is the depth of the pit defect; />
Figure 720352DEST_PATH_IMAGE068
Is the number of fatigue bending times of the continuous tube.
Maximum shear strain after introducing correction coefficient and positive strain of maximum shear strain plane:
Figure 269145DEST_PATH_IMAGE069
Figure 888346DEST_PATH_IMAGE071
in the fifth step, the continuous tube 1 containing the groove-shaped scratch defect was subjected to three-stage evaluation. Compared with the complete continuous pipe 1 under the same working condition, the fatigue life is reduced by 50 percent and is directly scrapped, the fatigue life is reduced by 20-50 percent and is finely evaluated, and the fatigue life is reduced by less than 20 percent and is roughly evaluated.
The following is a specific example of the life safety evaluation of a continuous pipe containing groove-shaped scratch defects:
a 50.8mm coiled tubing was tested in gas field service (open well operation). The coiled continuous pipe has the strength of QT900 and the wall thickness of 3.96mm, is subjected to multiple drilling and plugging operations before, and has the existing length of 5210.86m and the detection length of 4633.25 m. Two groove-shaped scratch defects are detected on the outer wall surface of the continuous pipe, and the depth of the larger groove-shaped scratch defect is 1mm.
The effect of 6 defect parameters on the fatigue life of the continuous tube was evaluated by finite element calculation, and as shown in table 1, among the 6 defect parameters, the defect depth, defect width, defect angle and defect length were found to have a relatively significant effect on the fatigue life of the continuous tube, and among the 4 parameters, the defect depth was most reduced, and the reduction width was 92%. The decrease amplitude of the circumferential distribution and the axial distribution is less than 30%, so that 2 defect parameters of the circumferential distribution and the axial distribution are not considered in the calculation and the evaluation later;
Figure 155379DEST_PATH_IMAGE073
as shown in table 2 and fig. 2-3, four parameters of groove-shaped defect along the depth a of the outer circular surface, the axial angle beta of the pit along the axial direction, the pit length c and the pit width b are selected by adopting the principle of an orthogonal test method, and each parameter takes four levels. L is carried out on the four levels of the four parameters 16 （4 4 ) Orthogonal test designs resulted in 16 total tests. Under different parameters in the tableK i Represented as being at a particular leveliThe sum of the results of the calculations below,
Figure 354279DEST_PATH_IMAGE074
to be at a specific leveliThe average value is->
Figure 757579DEST_PATH_IMAGE075
The method comprises the steps of carrying out a first treatment on the surface of the Extremely bad in the tableRIs the difference between the maximum average value and the minimum average value in a specific parameter, i.e. +.>
Figure 669384DEST_PATH_IMAGE076
。
Extreme differences of four defect parametersRAs shown in table 2, the primary and secondary relationships of the four defect parameters to the continuous tube fatigue life are: pit depth>Pit width>Pit angle>Pit length. The extreme difference of the defect depth is 120.25, and the extreme difference of the other three defect parameters is less than 50, namely the defect depth is the main control parameter affecting the fatigue life of the continuous pipe.
TABLE 2 orthogonal test chart
Figure 423714DEST_PATH_IMAGE078
Based on the previous finite element calculation result, the mechanical analysis and fatigue life prediction of the defect-containing continuous pipe are performed based on a conservative algorithmWhen in use, the pit defect angle is 90 degrees. Fig. 4 is a schematic diagram showing the deformation of a small section of coiled tubing containing pit defects, and fig. 5 is a schematic diagram showing the section thereof.MTo be subjected to bending moment by the continuous pipe, cross sectionP 1 For the external pressure to which the continuous tube is subjected,P 2 for the internal pressure to which the coiled tubing is subjected,r 1 in order to achieve a radius of the inside of the coiled tubing,r 2 in order to provide a continuous tube outer radius,c i andc 0 for the thickness of the inner and outer defects of the continuous tube,θthe central angle corresponding to the pit defect on the cross section of the continuous pipe.
From the previous finite element calculations and orthogonal experiments, it is known that the depth of groove defects is the most sensitive parameter affecting the fatigue life of the coiled tubing. When the inner surface and the outer surface of the continuous pipe are provided with groove-shaped defects, the influence of the groove-shaped defects on the fatigue life is considered when the fatigue life model of the continuous pipe is established. Radial stress of continuous pipe under internal pressure based on thick-wall cylinder theory
Figure 160725DEST_PATH_IMAGE079
Hoop stress->
Figure 684111DEST_PATH_IMAGE080
And axial stress->
Figure 645113DEST_PATH_IMAGE081
：
Figure 621160DEST_PATH_IMAGE082
Wherein:
Figure 161862DEST_PATH_IMAGE083
the outer radius of the continuous pipe is mm; />
Figure 805333DEST_PATH_IMAGE084
Is the inner radius, mm; />
Figure 547024DEST_PATH_IMAGE085
Is internal pressure, MPa; r is any radius, mm.
The critical point at which yield is first generated is always the inner surface of the coiled tubing, based on stress analysis and von Mises criteria
Figure 275946DEST_PATH_IMAGE086
；
Figure 354760DEST_PATH_IMAGE087
Total strain by bending action according to Remberg-Osgood elastoplastic stress-strain relationship
Figure 383896DEST_PATH_IMAGE088
Is elastic strain->
Figure 889964DEST_PATH_IMAGE089
And plastic strain->
Figure 106182DEST_PATH_IMAGE090
And (2) sum:
Figure 988687DEST_PATH_IMAGE091
wherein:Dthe diameter of the continuous pipe is mm;
Figure 996963DEST_PATH_IMAGE092
is a bending radius, mm;Eis elastic modulus, MPa; />
Figure 939511DEST_PATH_IMAGE093
Is the yield limit, MPa.
The axial force generated by bending is the main cause of plastic strain, internal pressure and axial stress under bending
Figure 377446DEST_PATH_IMAGE094
The method comprises the following steps: />
Figure 798063DEST_PATH_IMAGE095
Axial stress resulting from bending can be obtained from the Holomon relationship of stress to plastic strain
Figure 801791DEST_PATH_IMAGE096
Hoop strain, axial strain, and radial strain under compressive bending coupling load:
Figure 649661DEST_PATH_IMAGE097
wherein:
Figure 574892DEST_PATH_IMAGE098
is the circumferential strain; />
Figure 799200DEST_PATH_IMAGE099
Is axial strain; />
Figure 532801DEST_PATH_IMAGE100
Is radial strain; />
Figure 817152DEST_PATH_IMAGE101
Is the cyclic strain hardening coefficient, MPa; />
Figure 229678DEST_PATH_IMAGE102
Is a cyclic strain hardening index.
In the plastic deformation process of the continuous pipe, the assumption of unchanged volume is adopted, and the equivalent plastic strain under the coupling load
Figure 523257DEST_PATH_IMAGE103
The method comprises the following steps:
Figure 704839DEST_PATH_IMAGE104
the strain-life equation is as follows using a Brown-Miller fatigue life theoretical model:
Figure 160091DEST_PATH_IMAGE105
Figure 59914DEST_PATH_IMAGE106
maximum shear strain:
Figure 281817DEST_PATH_IMAGE107
positive strain of maximum shear strain plane:
Figure 317906DEST_PATH_IMAGE108
on the one hand, during theoretical calculation, only the fatigue life of the continuous pipe groove defect is calculated based on a conservation algorithm, and on the other hand, the lowest yield strength (the yield strength of the continuous pipe in engineering practice is higher than the minimum value) is selected during calculation, so that the predicted value of the fatigue life of the continuous pipe groove defect is smaller than an experimental value, the calculated result of a theoretical model is more accurate, and a correction coefficient is obtained according to the comparison regression of the experimental value and the theoretical calculated result
Figure 944059DEST_PATH_IMAGE109
。/>
Figure 331178DEST_PATH_IMAGE110
Wherein:c 0 is the depth of the pit defect;N f is the number of fatigue bending times of the continuous tube.
Corrected maximum shear strain and positive strain of the plane of maximum shear strain:
Figure 966559DEST_PATH_IMAGE111
the fatigue life model after correction is:
Figure 122734DEST_PATH_IMAGE112
the model calculations at different defect depths are shown in table 3:
TABLE 3 model calculation results at different defect depths
Figure 919789DEST_PATH_IMAGE113
In the fifth step, the continuous tube 1 containing the groove-shaped scratch defect was subjected to three-stage evaluation. Compared with the complete continuous pipe 1 under the same working condition, the fatigue life is reduced by 50 percent and is directly scrapped, the fatigue life is reduced by 20-50 percent and is finely evaluated, and the fatigue life is reduced by less than 20 percent and is roughly evaluated.
Table 4 evaluation rating at different defect depths
Figure 528625DEST_PATH_IMAGE115
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.

Claims (1)

1. The method for evaluating the fatigue life of the continuous pipe containing the groove-shaped scratch defects is characterized by comprising the following steps of:
1), screening and confirming an outer wall groove-shaped scratch defect (2) and an inner wall groove-shaped scratch defect (3) in the service continuous pipe (1);
2) Detecting geometric parameters of the shape of the outer wall groove-shaped scratch defect (2) and the shape of the inner wall groove-shaped scratch defect (3); the defect parameters of the outer wall groove-shaped scratch defect (2) and the inner wall groove-shaped scratch defect (3) are as follows: the axial angle beta of the defect, the depth a of the defect, the length c of the defect, the width b of the defect, the rounded corners R of the periphery of the scratch, the circumferential distribution of the defect and the number of the circumferential distribution of the defect are measured by using defect detection equipment, and the parameters of the groove-shaped scratch defect (2) on the outer wall and the groove-shaped scratch defect (3) on the inner wall are measured;
3) Sensitive defect parameters of the outer wall groove-shaped scratch defect (2) and the inner wall groove-shaped scratch defect (3) are preferred; obtaining sensitivity parameters, namely the defect axial angle beta, the defect depth a, the defect length c, the defect width b, the rounded corners R of the periphery of scratches, the circumferential distribution of the defects and the number of the circumferential distribution of the defects, from the sensitivity parameters in sequence, namely the defect depth a, the defect width b, the defect axial angle beta and the defect length c based on an orthogonal test method;
4) Theoretically calculating the fatigue life of the continuous tube (1) containing the outer wall groove scratch defect (2) and the inner wall groove scratch defect (3) on the basis of the groove defect sensitivity parameter;
5) Performing three-level evaluation on the continuous tube (1) containing the outer wall groove-shaped scratch defect (2) and the inner wall groove-shaped scratch defect (3); namely, carrying out three-level evaluation on the continuous pipe containing the groove-shaped scratch defects; compared with a complete continuous pipe under the same working condition, the fatigue life is reduced by 50 percent and is directly scrapped, the fatigue life is reduced by 20 to 50 percent and is finely evaluated, and the fatigue life is reduced by less than 20 percent and is roughly evaluated; the fatigue life calculation method of the continuous tube (1) containing the outer wall groove-shaped scratch defect (2) and the inner wall groove-shaped scratch defect (3) in the step 4) comprises the following steps:
when the inner surface and the outer surface of the continuous pipe (1) are provided with the outer wall groove-shaped scratch defect (2) and the inner wall groove-shaped scratch defect (3), the influence of the outer wall groove-shaped scratch defect (2) and the inner wall groove-shaped scratch defect (3) on the fatigue life is considered when the fatigue life model of the continuous pipe (1) is built, and the radial stress sigma of the continuous pipe (1) under the internal pressure is obtained based on the thick-wall cylinder theory r Hoop stress sigma t And axial stress sigma z ：
Figure FDA0004130185970000011
Wherein: r is (r) 1 Is the outer radius of the continuous pipe (1), mm; r is (r) 2 Is the inner radius, mm; p (P) 2 Is the internal pressure, MPa; r is any radius, mm; c i And c 0 Thickness of the inner defect and the outer defect of the continuous tube;
the critical point at which yield is first generated is always the inner surface of the continuous tube (1) according to stress analysis and von Mises criteria, when
r＝r 1 +c i ；
Figure FDA0004130185970000021
According to the relation of Remberg-osgood elastoplastic stress-strain, the total strain epsilon generated by bending is elastic strain epsilon e And plastic strain ε p And (2) sum:
Figure FDA0004130185970000022
Figure FDA0004130185970000023
wherein: d is the outer diameter of the continuous pipe (1), and the diameter is mm; r' is the bending radius, mm; e is elastic modulus, MPa; sigma (sigma) s Is the yield limit, MPa;
the axial force generated by bending is the main cause of plastic strain, internal pressure and axial stress sigma under bending a The method comprises the following steps:
σ a ＝σ z +σ p
the axial stress sigma generated by bending can be obtained by the Holomon relation of stress and plastic strain p Hoop strain, axial strain, and radial strain under compressive bending coupling load:
σ p ＝K′(ε p ) n′
Figure FDA0004130185970000031
wherein: epsilon t Is the circumferential strain; epsilon a Is axial strain; epsilon r Is radial strain; k' is the cyclic strain hardening coefficient, MPa; n' is a cyclic strain hardening exponent;
in the plastic deformation process of the continuous pipe (1), the assumption of unchanged volume is adopted, and the equivalent plastic strain epsilon under the coupling load 0 The method comprises the following steps:
Figure FDA0004130185970000032
the strain-life equation is as follows using a Brown-Miller fatigue life theoretical model:
Figure FDA0004130185970000033
ε a ＞ε r ＞ε t maximum shear strain:
Δγ max ＝ε a -ε t
positive strain of maximum shear strain plane:
Δε n ＝(ε t +ε a )/2
to consider the influence of other parameters besides sensitive parameters on the fatigue life of continuous pipe, a correction coefficient is introduced
Figure FDA0004130185970000034
Figure FDA0004130185970000041
Wherein: c 0 Is the depth of the pit defect; n (N) f The number of fatigue bending times of the continuous pipe;
maximum shear strain after introducing correction coefficient and positive strain of maximum shear strain plane:
Figure FDA0004130185970000042
Figure FDA0004130185970000043
the final fatigue life calculation model of the defect-containing continuous pipe (1) is as follows:
Figure FDA0004130185970000044
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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103616179A (en) * 2013-12-05 2014-03-05 广西大学 Transmission gear fatigue life assessment method based on defect modeling
WO2015187923A1 (en) * 2014-06-04 2015-12-10 Schlumberger Canada Limited Pipe defect assessment system and method
CN110826285A (en) * 2019-11-22 2020-02-21 华东理工大学 Fatigue life prediction method for geometric discontinuous structure

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20120271566A1 (en) * 2011-04-21 2012-10-25 Vinayak Deshmukh Method for the prediction of fatigue life for structures

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103616179A (en) * 2013-12-05 2014-03-05 广西大学 Transmission gear fatigue life assessment method based on defect modeling
WO2015187923A1 (en) * 2014-06-04 2015-12-10 Schlumberger Canada Limited Pipe defect assessment system and method
CN110826285A (en) * 2019-11-22 2020-02-21 华东理工大学 Fatigue life prediction method for geometric discontinuous structure

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
Liu Shaohu et al..Theoretical and experimental research of bearing capacity and fatigue life for coiled tubing under internal pressure.Engineering Failure Analysis.2019,第104卷第1133-1142页. *
赵乐等.体积型缺陷几何参数对连续油管疲劳寿命影响.石油矿场机械.2016,第45卷(第7期),第1-5页. *
郑华林 ; 肖晖 ; 刘少胡 ; .缺陷敏感参数对连续管塑性极限承载能力的影响.塑性工程学报.2016,第23卷(第04期),第149-153页. *

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