CN113720678A - Method and device for determining safe fracture toughness of pipeline - Google Patents
Method and device for determining safe fracture toughness of pipeline Download PDFInfo
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Abstract
The invention provides a method and a device for determining safe fracture toughness of a pipeline, a storage medium and electronic equipment, and relates to the technical field of pipeline design and integrity evaluation, wherein the method comprises the following steps: acquiring a crack tip stress intensity factor of the pipeline when the crack size of the pipeline reaches a preset size threshold; wherein the preset size threshold is determined based on a design condition of the pipeline; determining the safe fracture ratio of the pipeline when the crack size of the pipeline reaches the preset size threshold; determining a safe fracture toughness of the pipe based on the crack tip stress intensity factor and the safe fracture ratio. The technical scheme provided by the invention can simply and accurately determine the safe fracture toughness of the pipeline.
Description
Technical Field
The invention relates to the technical field of pipeline design and integrity evaluation, in particular to a method and a device for determining safe fracture toughness of a pipeline.
Background
The corrosion and the fracture are two main damage modes of the pipeline service, the wall thickness of the pipeline is reduced due to the corrosion, the bearing capacity is reduced, the corrosion part is often the part where a crack is initiated in the service process, the pipeline is suddenly fractured and fails due to the brittle expansion of the crack, and the serious economic loss and even the personal injury are caused. Therefore, in terms of pipe safety, it is important to prevent fracture failure due to crack-like defects, and to take into consideration the influence of corrosion damage on the fracture failure.
The brittle propagation of a crack is related to the stress-strain state of the crack tip, whereas the pipe wall thickness has a large influence on the stress-strain state of the crack tip. When the wall thickness is changed from thin to thick, the stress field of the crack tip is gradually changed from plane stress to a plane strain state, the crack tip is always in a three-direction tension state, the constraint on the strain is high, the plastic deformation is limited, and the material is enabled to generate 'embrittlement', so that the occurrence of brittle failure is caused. The results of the research show that when the thickness of the sample is small, the crack tip of the sample is in a plane stress state and has larger fracture toughness. As the thickness of the specimen increases, the in-plane stress state transitions to the in-plane strain state and the fracture toughness of the material will gradually decrease. After the thickness of the sample exceeds a critical thickness, the material is completely in a plane strain state, the fracture toughness of the material is not changed along with the thickness and finally tends to a constant lower limit value, and the constant is the plane strain fracture toughness K of the materialIcWhich represents the lower limit of the fracture toughness of the material.
At present, plane strain fracture toughness has been widely used in the fracture control of materials. Stress intensity factor K of crack tip when crack of pipeline reaches allowable maximum size under design working conditionIMust be less than or equal to the safe fracture toughness of the pipeDegree KsSo as to prevent the occurrence of brittle propagation of cracks, namely:
KI≤Ks，
Ks＝Φ·KIc(0＜Φ≤1)
in the above formula KIcIs the plane strain fracture toughness of the material; phi is a safety factor and is a design constant.
Therefore, determining the safe fracture toughness of a pipe must first determine the plane strain fracture toughness of the selected material. However, testing of the plane strain fracture toughness of materials requires that the specimen dimensions meet the conditions of plane strain or small strain. For the ductile metals widely used in the current pipelines, huge samples and high-tonnage testing machines are needed to meet the conditions, the cost is high, and even samples meeting the size requirement can not be prepared.
In addition, the determination method of the safe fracture toughness of the pipeline only considers the fracture failure mode, and does not consider the plastic deformation failure mode controlled by the strength factor under the influence of the corrosion condition.
In summary, in the process of implementing the present invention, the inventors found that the prior art has at least the following problems: at present, a simple, easy and accurate method for determining the safe fracture toughness of the pipeline does not exist in the field.
Disclosure of Invention
In view of the above problems in the prior art, the present application provides a method and an apparatus for determining safe fracture toughness of a pipeline, which can simply and accurately determine the safe fracture toughness of the pipeline.
In order to achieve the purpose, the technical scheme of the invention is realized as follows:
in a first aspect, an embodiment of the present invention provides a method for determining safe fracture toughness of a pipeline, where the method includes:
acquiring a crack tip stress intensity factor of the pipeline when the crack size of the pipeline reaches a preset size threshold; wherein the preset size threshold is determined based on a design condition of the pipeline;
determining the safe fracture ratio of the pipeline when the crack size of the pipeline reaches the preset size threshold;
determining a safe fracture toughness of the pipe based on the crack tip stress intensity factor and the safe fracture ratio.
Preferably, the safe fracture toughness of the pipe is determined using the following expression:
Ks＝KI/Kr
wherein, KsFor the safe fracture toughness of the pipe, KIIs the crack tip stress intensity factor, KrThe safe fracture ratio is stated.
Preferably, the determining the safe fracture ratio of the pipeline when the crack size of the pipeline reaches the preset size threshold value comprises:
obtaining the yield strength and the tensile strength of the pipeline which are measured in advance;
calculating the load ratio of the pipeline when the crack size of the pipeline reaches the preset size threshold value;
determining a safe fracture ratio of the pipe when the crack size of the pipe reaches the preset size threshold based on the yield strength, the tensile strength and the load ratio.
Preferably, the calculating the load ratio of the pipeline when the crack size of the pipeline reaches the preset size threshold value comprises:
acquiring the reference stress of the pipeline when the crack size of the pipeline reaches the preset size threshold;
and calculating the load ratio of the pipeline when the crack size of the pipeline reaches the preset size threshold value based on the reference stress and the yield strength.
Preferably, the load ratio of the pipe when its crack size reaches the preset size threshold is calculated using the following expression:
Lr＝σref/σy
wherein L isrIs the load ratio, σrefFor the reference stress, σyIs the yield strength.
Preferably, the crack tip stress intensity factor is calculated based on the preset size threshold value and by adopting an existing first formula;
the reference stress is obtained by calculation by adopting an existing second formula based on the preset size threshold;
the design working condition of the pipeline comprises the following steps: the allowable wall thickness of the pipeline under a preset corrosion condition and the preset conveying pressure of the pipeline.
Preferably, said determining a safe fracture ratio of said pipe when its crack size reaches said preset size threshold based on said yield strength, said tensile strength and said load ratio comprises:
when L isr≤(σy+σu)/(2·σy) Then, the safe fracture ratio is calculated using the following expression:
Kr＝(1-0.14Lr 2)[0.3+0.7exp(-0.65Lr 6)]
when L isr>(σy+σu)/(2·σy) When, Kr＝+∞；
Wherein L isrIs the load ratio, σyAs the yield strength, σuFor said tensile strength, KrThe safe fracture ratio is stated.
In a second aspect, an embodiment of the present invention provides an apparatus for determining safe fracture toughness of a pipeline, the apparatus including:
the crack tip stress intensity factor acquiring unit is used for acquiring a crack tip stress intensity factor of the pipeline when the crack size of the pipeline reaches a preset size threshold; wherein the preset size threshold is determined based on a design condition of the pipeline;
a safe fracture ratio determination unit for determining the safe fracture ratio of the pipeline when the crack size of the pipeline reaches the preset size threshold;
a safe fracture toughness determination unit for determining a safe fracture toughness of the pipe based on the crack tip stress intensity factor and the safe fracture ratio.
In a third aspect, an embodiment of the present invention provides a storage medium, where a program code is stored, and when being executed by a processor, the method for determining the safe fracture toughness of the pipeline according to any one of the foregoing embodiments is implemented.
In a fourth aspect, an embodiment of the present invention provides an electronic device, where the electronic device includes a memory and a processor, where the memory stores program code executable on the processor, and when the program code is executed by the processor, the method for determining a safe fracture toughness of a pipeline according to any one of the foregoing embodiments is implemented.
According to the method, the device, the storage medium and the electronic equipment for determining the safe fracture toughness of the pipeline, provided by the embodiment of the invention, the safe fracture toughness of the pipeline can be determined based on the stress intensity factor at the tip of the crack and the safe fracture ratio only by acquiring the stress intensity factor at the tip of the crack of the pipeline when the size of the crack reaches the preset size threshold and determining the safe fracture ratio of the pipeline when the size of the crack reaches the preset size threshold, and the calculation process is simple and rapid. In addition, the stress intensity factor of the tip of the crack belongs to the fracture failure parameter of the pipeline, and the safe fracture ratio belongs to the plastic deformation failure parameter of the pipeline, so that the fracture failure mode of the pipeline and the plastic deformation failure mode of the corrosion factor influencing the intensity control are substantially comprehensively considered, and the calculation result is accurate and reliable. Therefore, compared with the prior art, the technical scheme of the invention can simply and accurately determine the safe fracture toughness of the pipeline.
Drawings
The scope of the present disclosure will be better understood from the following detailed description of exemplary embodiments, which is to be read in connection with the accompanying drawings. Wherein the included drawings are:
FIG. 1 is a first flowchart of a method according to an embodiment of the present invention;
FIG. 2 is a flowchart of a second method of an embodiment of the present invention;
FIG. 3 is a diagram illustrating an apparatus according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the following will describe in detail an implementation method of the present invention with reference to the accompanying drawings and embodiments, so that how to apply technical means to solve the technical problems and achieve the technical effects can be fully understood and implemented.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, the present invention may be practiced in other ways than those specifically described herein, and therefore the scope of the present invention is not limited by the specific embodiments disclosed below.
Example one
According to an embodiment of the present invention, there is provided a method for determining safe fracture toughness of a pipeline, as shown in fig. 1, the method according to this embodiment includes:
step S101, acquiring a stress intensity factor of a crack tip of the pipeline when the crack size of the pipeline reaches a preset size threshold; wherein the preset size threshold is determined based on a design condition of the pipeline;
in this embodiment, the design condition of the pipeline includes: the allowable wall thickness of the pipeline under the preset corrosion condition, the preset delivery pressure of the pipeline and the like, and the preset size threshold value may be determined based on design parameters such as the allowable wall thickness of the pipeline under the preset corrosion condition, the preset delivery pressure of the pipeline and the like.
In this embodiment, the crack tip stress intensity factor of the pipeline when the crack size reaches the preset size threshold may be calculated by using an existing first formula based on the preset size threshold. Specifically, the first formula may be obtained with reference to the industry standard API 579-1-2007 query in the art:
wherein, KIIs the crack tip stress intensity factor.
Step S102, determining the safe fracture ratio of the pipeline when the crack size of the pipeline reaches the preset size threshold;
specifically, determining the safe fracture ratio of the pipeline when the crack size of the pipeline reaches the preset size threshold value comprises the following steps: obtaining the yield strength and the tensile strength of the pipeline which are measured in advance; calculating the load ratio of the pipeline when the crack size of the pipeline reaches the preset size threshold value; determining a safe fracture ratio of the pipe when the crack size of the pipe reaches the preset size threshold based on the yield strength, the tensile strength and the load ratio.
In this embodiment, the yield strength and tensile strength of the pipe can be measured by subjecting the prepared pipe sample to uniaxial tensile test by a material tensile testing machine.
In this embodiment, calculating the load ratio of the pipeline when the crack size of the pipeline reaches the preset size threshold includes: acquiring the reference stress of the pipeline when the crack size of the pipeline reaches the preset size threshold; and calculating the load ratio of the pipeline when the crack size of the pipeline reaches the preset size threshold value based on the reference stress and the yield strength.
Wherein the reference stress of the pipeline when the crack size reaches the preset size threshold value can be calculated by adopting an existing second formula based on the preset size threshold value. Specifically, this second formula may be obtained with reference to the industry standard API 579-1-2007 query in the art:
wherein σrefIs the reference stress of the pipe when the crack size of the pipe reaches a preset size threshold.
Specifically, the load ratio of the pipe when the crack size thereof reaches the preset size threshold is calculated using the following expression:
Lr＝σref/σy
wherein L isrIs the load ratio, σrefFor the reference stress, σyIs the yield strength.
In this embodiment, determining the safe fracture ratio of the pipe when the crack size of the pipe reaches the preset size threshold based on the yield strength, the tensile strength and the load ratio includes:
when L isr≤(σy+σu)/(2·σy) Then, the safe fracture ratio is calculated using the following expression:
Kr＝(1-0.14Lr 2)[0.3+0.7exp(-0.65Lr 6)]
when L isr>(σy+σu)/(2·σy) When, Kr＝+∞；
Wherein L isrIs the load ratio, σyAs the yield strength, σuFor said tensile strength, KrThe safe fracture ratio is stated.
And S103, determining the safe fracture toughness of the pipeline based on the crack tip stress intensity factor and the safe fracture ratio.
Specifically, the safe fracture toughness of the pipe is determined using the following expression:
Ks＝KI/Kr
wherein, KsFor the safe fracture toughness of the pipe, KIIs the crack tip stress intensity factor, KrThe safe fracture ratio is stated.
According to the method, the device, the storage medium and the electronic equipment for determining the safe fracture toughness of the pipeline, provided by the embodiment of the invention, the safe fracture toughness of the pipeline can be determined based on the stress intensity factor at the tip of the crack and the safe fracture ratio only by acquiring the stress intensity factor at the tip of the crack of the pipeline when the size of the crack reaches the preset size threshold and determining the safe fracture ratio of the pipeline when the size of the crack reaches the preset size threshold, and the calculation process is simple and rapid. In addition, the stress intensity factor of the tip of the crack belongs to the fracture failure parameter of the pipeline, and the safe fracture ratio belongs to the plastic deformation failure parameter of the pipeline, so that the fracture failure mode of the pipeline and the plastic deformation failure mode of the corrosion factor influencing the intensity control are substantially comprehensively considered, and the calculation result is accurate and reliable. Therefore, compared with the prior art, the technical scheme of the invention can simply and accurately determine the safe fracture toughness of the pipeline.
Example two
In this embodiment, a method for determining the safe fracture toughness of a pipeline engineering in a design stage is described in detail by taking an X80 natural gas pipeline engineering with a certain specification of phi 1219 × 21.4mm and a design pressure of 12MPa as an example. As shown in fig. 2, the method includes:
step S201, acquiring design working conditions of a pipeline;
specifically, the corrosion condition of the pipeline is comprehensively analyzed, the corrosion of the treated natural gas is low, and the allowable wall thickness under the corrosion condition of the pipeline is 18.4mm according to the annual average corrosion rate of 0.1mm and the service life of the pipeline for 30 years. And meanwhile, the set conveying pressure of the pipeline is obtained.
Step S202, obtaining the yield strength and the tensile strength of the pipeline which are measured in advance;
specifically, a transverse tensile sample of the pipe is prepared according to the relevant standard, and the yield strength sigma of the transverse direction of the pipe sample is measured by performing a uniaxial tensile test by using a material tensile testing machiney555MPa, tensile strength sigmau＝625MPa。
Step S203, determining a preset size threshold of the pipeline crack, and calculating a reference stress of the pipeline when the crack size reaches the preset size threshold;
in this embodiment, the preset size threshold of the pipeline crack is the maximum size of the semi-elliptical axial outer surface crack allowed by design, and the maximum size of the crack includes: maximum crack depth and maximum crack length. Wherein, the maximum value a of the crack depth is calculated by adopting the following formula:
a＝t/4＝4.6mm
wherein t is the above allowable wall thickness.
The maximum crack length was 20 a-92 mm.
Inquiring to obtain reference stress sigma of the semi-elliptical axial outer surface crack of the steel pipe according to reference standard API 579-1-2007refThe calculation formula of (2) is as follows:
substituting the related parameters in the reference standard API 579-1-2007 query or computational formula together with the maximum size parameter of the crack into the above formula to obtain sigmaref＝454MPa。
Step S204, calculating the load ratio of the pipeline when the crack size of the pipeline reaches a preset size threshold;
specifically, σ obtained by the test in step S202y555Mpa and sigma calculated in step S203refSubstituting 454Mpa into the following formula:
Lr＝σref/σy
calculating to obtain Lr＝0.818。
Step S205, determining the safe fracture ratio of the pipeline when the crack size of the pipeline reaches a preset size threshold value based on the yield strength, the tensile strength and the load ratio;
specifically, L calculated in step S204r0.818 due to Lr＜(σy+σu)/(2·σy) 1.063, so will LrSubstituting 0.818 into the following equation:
Kr＝(1-0.14Lr 2)[0.3+0.7exp(-0.65Lr 6)]
calculating to obtain Kr＝0.793。
Step S206, acquiring a stress intensity factor of a crack tip of the pipeline when the crack size of the pipeline reaches a preset size threshold;
specifically, the stress intensity factor K of the crack tip of the semielliptical axial outer surface crack of the steel pipe is obtained by referring to the query of standard API 579-1-2007IThe calculation formula of (2) is as follows:
reference standard API 579-1-2007 queries orCalculating the related parameters in the formula, and substituting the related parameters together with the maximum size parameter of the crack into the formula to obtain KI＝60.3MPam0.5。
And step S207, determining the safe fracture toughness of the pipeline based on the crack tip stress intensity factor and the safe fracture ratio.
Specifically, K determined in step S205rK calculated in step S206 and 0.793I＝60.3MPam0.5Substituting the following equation:
Ks＝KI/Kr
calculating to obtain Ks＝76.0MPam0.5。
According to the seven steps, the pipeline conveying pressure and the allowable wall thickness in the embodiment are changed, the preset size threshold value of the pipeline crack is further changed, and the determined safe fracture toughness results are shown in table 1. From Table 1, it can be seen that the load ratio L in the two examples 6 and 12 isr>(σy+σu)/(2·σy) 1.063, safe fracture ratio KrCalculated safe fracture toughness K ∞sWhen equal to 0, the pipeline KI≤KsThe design conditions of (a) cannot be met, at the moment, the pipeline failure is controlled by strength, excessive plastic deformation failure can occur, and the load must be reduced, the wall thickness must be increased or the material strength must be improved. Therefore, the technical scheme of the invention is based on double criteria of fracture and strength theory, comprehensively considers a fracture failure mode and a plastic deformation failure mode under a corrosion condition, ensures accurate and reliable pipeline safety fracture toughness result, and can prevent fracture failure and excessive plastic deformation failure under the corrosion condition.
TABLE 1
In conclusion, the yield strength σ of the material only needs to be tested by using a common uniaxial tensile testyAnd tensile strength σuFormula calculation suitable for selection is selected by referring to relevant standards, handbooks or literatures in the fieldStress intensity factor K of crack tip when crack of pipeline reaches allowable maximum size under design working conditionIAnd a reference stress sigmarefThe safe fracture toughness K of the pipeline can be calculated according to the formula provided by the embodimentsAnd the calculation process is simple and quick. Meanwhile, the calculation process shows that the calculation method comprehensively considers the fracture failure mode of the pipeline and the plastic deformation failure mode of the corrosion factor influencing the strength control, and the calculation result is accurate and reliable.
The technical scheme provided by the embodiment of the invention has the following beneficial effects:
1. the invention firstly and definitely provides a method for determining the safe fracture toughness index of the pipeline, the technical scheme is convenient and easy to implement, the calculation process is simple and quick, and the engineering application is facilitated.
2. The method avoids the plane strain fracture toughness of the tested material in the process of determining the safe fracture toughness of the pipeline, and saves the test expenditure and the design period.
3. The technical scheme of the invention is based on double criteria of fracture and strength theory, comprehensively considers a fracture failure mode and a plastic deformation failure mode, determines the safe fracture toughness of the pipeline with accurate and reliable results, and reduces the failure probability of the pipeline.
EXAMPLE III
In correspondence with the above method embodiment, the present invention also provides a device for determining safe fracture toughness, as shown in fig. 3, the device comprising:
a crack tip stress intensity factor obtaining unit 301, configured to obtain a crack tip stress intensity factor of the pipeline when a crack size of the pipeline reaches a preset size threshold; wherein the preset size threshold is determined based on a design condition of the pipeline;
a safe fracture ratio determination unit 302 for determining a safe fracture ratio of the pipeline when the crack size of the pipeline reaches the preset size threshold;
a safe fracture toughness determination unit 303 for determining a safe fracture toughness of the pipe based on the crack tip stress intensity factor and the safe fracture ratio.
The working principle, the working process and the like of the device relate to specific embodiments, which can be referred to in the specific embodiments of the method for determining the safe fracture toughness provided by the present invention, and the same technical contents will not be described in detail herein.
Example four
There is also provided, in accordance with an embodiment of the present invention, a storage medium having program code stored thereon, which when executed by a processor, implements the method for determining safe fracture toughness as described in any of the above embodiments.
EXAMPLE five
There is also provided, according to an embodiment of the present invention, an electronic device including a memory and a processor, the memory storing thereon program code executable on the processor, the program code implementing the method for determining safe fracture toughness according to any one of the above embodiments when executed by the processor.
According to the method, the device, the storage medium and the electronic equipment for determining the safe fracture toughness of the pipeline, provided by the embodiment of the invention, the safe fracture toughness of the pipeline can be determined based on the stress intensity factor at the tip of the crack and the safe fracture ratio only by acquiring the stress intensity factor at the tip of the crack of the pipeline when the size of the crack reaches the preset size threshold and determining the safe fracture ratio of the pipeline when the size of the crack reaches the preset size threshold, and the calculation process is simple and rapid. In addition, the stress intensity factor of the tip of the crack belongs to the fracture failure parameter of the pipeline, and the safe fracture ratio belongs to the plastic deformation failure parameter of the pipeline, so that the fracture failure mode of the pipeline and the plastic deformation failure mode of the corrosion factor influencing the intensity control are substantially comprehensively considered, and the calculation result is accurate and reliable. Therefore, compared with the prior art, the technical scheme of the invention can simply and accurately determine the safe fracture toughness of the pipeline.
In the several embodiments provided in the present application, it should be understood that the disclosed apparatus and method may be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative, and for example, a division of a unit is merely a logical division, and an actual implementation may have another division, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed.
Units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment of the present invention.
In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.
The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present invention essentially or partially contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product, which is stored in a storage medium and includes instructions for causing an electronic device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.
Although the embodiments of the present invention have been described above, the above description is only for the convenience of understanding the present invention, and is not intended to limit the present invention. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. A method for determining the safe fracture toughness of a pipeline, said method comprising:
acquiring a crack tip stress intensity factor of the pipeline when the crack size of the pipeline reaches a preset size threshold; wherein the preset size threshold is determined based on a design condition of the pipeline;
determining the safe fracture ratio of the pipeline when the crack size of the pipeline reaches the preset size threshold;
determining a safe fracture toughness of the pipe based on the crack tip stress intensity factor and the safe fracture ratio.
2. The method of determining the safe fracture toughness of a pipe as claimed in claim 1, wherein the safe fracture toughness of said pipe is determined using the following expression:
Ks＝KI/Kr
wherein, KsFor the safe fracture toughness of the pipe, KIIs the crack tip stress intensity factor, KrThe safe fracture ratio is stated.
3. The method of determining the safe fracture toughness of a pipe as recited in claim 1, wherein said determining the safe fracture ratio of said pipe when the crack size of said pipe reaches said predetermined size threshold comprises:
obtaining the yield strength and the tensile strength of the pipeline which are measured in advance;
calculating the load ratio of the pipeline when the crack size of the pipeline reaches the preset size threshold value;
determining a safe fracture ratio of the pipe when the crack size of the pipe reaches the preset size threshold based on the yield strength, the tensile strength and the load ratio.
4. The method of determining the safe fracture toughness of a pipe as set forth in claim 3, wherein said calculating a load ratio of said pipe at the time of its crack size reaching said preset size threshold value comprises:
acquiring the reference stress of the pipeline when the crack size of the pipeline reaches the preset size threshold;
and calculating the load ratio of the pipeline when the crack size of the pipeline reaches the preset size threshold value based on the reference stress and the yield strength.
5. The method of determining the safe fracture toughness of a pipe as claimed in claim 4, wherein the load ratio of the pipe at the time when the crack size of the pipe reaches the preset size threshold is calculated using the following expression:
Lr＝σref/σy
wherein L isrIs the load ratio, σrefFor the reference stress, σyIs the yield strength.
6. The method of determining pipe safe fracture toughness of claim 4,
the stress intensity factor of the crack tip is calculated and obtained by adopting an existing first formula on the basis of the preset size threshold;
the reference stress is obtained by calculation by adopting an existing second formula based on the preset size threshold;
the design working condition of the pipeline comprises the following steps: the allowable wall thickness of the pipeline under a preset corrosion condition and the preset conveying pressure of the pipeline.
7. The method of determining the safe fracture toughness of the pipe as recited in claim 3, wherein said determining the safe fracture ratio of the pipe when the crack size of the pipe reaches the preset size threshold based on the yield strength, the tensile strength and the load ratio comprises:
when L isr≤(σy+σu)/(2·σy) Then, the safe fracture ratio is calculated using the following expression:
Kr＝(1-0.14Lr 2)[0.3+0.7exp(-0.65Lr 6)]
when L isr>(σy+σu)/(2·σy) When, Kr＝+∞；
Wherein L isrIs the load ratio, σyAs the yield strength, σuFor said tensile strength, KrThe safe fracture ratio is stated.
8. An apparatus for determining the safe fracture toughness of a pipeline, said apparatus comprising:
the crack tip stress intensity factor acquiring unit is used for acquiring a crack tip stress intensity factor of the pipeline when the crack size of the pipeline reaches a preset size threshold; wherein the preset size threshold is determined based on a design condition of the pipeline;
a safe fracture ratio determination unit for determining the safe fracture ratio of the pipeline when the crack size of the pipeline reaches the preset size threshold;
a safe fracture toughness determination unit for determining a safe fracture toughness of the pipe based on the crack tip stress intensity factor and the safe fracture ratio.
9. A storage medium having stored thereon program code, wherein the program code, when executed by a processor, implements the method of determining pipe safe fracture toughness of any of claims 1 to 7.
10. An electronic device comprising a memory, a processor, and program code stored on the memory and executable on the processor, wherein the program code when executed by the processor implements the method for determining pipe safe fracture toughness of any of claims 1 to 7.
Priority Applications (1)
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| 叶永青: "基于断裂力学的导管架平台疲劳裂纹评估研究", 《中国优秀硕士学位论文全文数据库 工程科技Ⅱ辑(月刊)》, pages 2 * |
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