Method, device, equipment and medium for evaluating service life of dissimilar steel pipeline containing buried crack

Abstract

The application relates to the technical field of buried crack, in particular to a buried crack-containing dissimilar steel pipeline life evaluation method, device, equipment and medium, wherein the method comprises the following steps: calculating a service stress; calculating a load ratio and a fracture ratio of the dissimilar steel pipeline, and judging whether the buried crack is in an acceptable range; if the buried crack is in the acceptable range, predicting the residual life of a creep crack extending to a critical depth; calculating a crack extension increment under a fatigue load according to a preset fatigue cycle period and an internal pressure fluctuation range; coupling creep and fatigue extension amounts based on the crack extension increment, determining a total crack extension amount, and determining a creep-fatigue coupling life according to the total crack extension amount; and comparing the creep dominant life and the creep-fatigue coupling life to generate the final residual life of the dissimilar steel pipeline. Thus, the defects of insufficient response of a traditional single mechanism model to material mismatch characteristics are solved, and the crack morphology prediction distortion problem caused by the anisotropy of dissimilar steel materials is solved.

Description

Technical Field

[0001] This application relates to the field of buried crack technology, and in particular to a method, apparatus, equipment and medium for life assessment of dissimilar steel pipes containing buried cracks. Background Technology

[0002] Buried cracks are hidden defects that exist inside the wall thickness of pressure vessels. They are characterized by their innate, delayed, and prominent nature. Under alternating loads or intermittent operation, they may extend to the surface, causing the risk of penetrating damage. Ultrasonic testing technology is preferred for detection, and strict excavation and repair procedures must be implemented during treatment.

[0003] In related technologies, a scaling rate model based on the Paris formula has been established, and the remaining lifetime has been quantitatively assessed through safety decay path simulation.

[0004] However, the relevant technologies suffer from prominent early failure issues, limited assessment methods, and bottlenecks in engineering applications, which urgently need to be improved. Summary of the Invention

[0005] This application provides a method, apparatus, equipment, and medium for assessing the lifespan of dissimilar steel pipes with buried cracks, in order to address the problems of prominent early failure issues, limitations in assessment methods, and bottlenecks in engineering applications in related technologies.

[0006] The first aspect of this application provides a method for assessing the lifespan of a dissimilar steel pipe with buried cracks, comprising the following steps: acquiring any pipe parameter from the geometric dimensions and material mechanical properties of the dissimilar steel pipe, and collecting any crack data from the depth, length, and distance of the buried crack from the pipe surface; based on the pipe parameter and the crack data, calculating the service stresses of primary membrane stress and primary bending stress according to the pipe internal pressure, inner diameter, and wall thickness of the dissimilar steel pipe; based on the service stresses, calculating the load ratio and fracture ratio of the dissimilar steel pipe, and comparing the failure assessment curve of the buried crack with the safety boundary according to the load ratio and the fracture ratio to generate comparison data, and determining whether the buried crack is within an acceptable range according to the comparison data; if the buried crack is within an acceptable range... If the crack is within the acceptable range, the creep crack propagation rate in the depth direction is calculated using a pre-defined constitutive model. Based on this propagation rate, the remaining life of the creep crack when it reaches the critical depth is predicted to determine the creep-dominant life. The stress intensity factor amplitude of the fatigue crack is determined based on a pre-defined load difference. Based on this stress intensity factor amplitude, the crack propagation increment under the fatigue load is calculated according to a pre-defined fatigue cycle period and internal pressure fluctuation range. The creep and fatigue propagation amounts are coupled based on the crack propagation increment to determine the total crack propagation amount. The creep-fatigue coupled life is then determined based on the total crack propagation amount. The creep-fatigue coupled life is compared to generate the final remaining life of the dissimilar steel pipe.

[0007] Optionally, in one embodiment of this application, obtaining any pipe parameter among the geometric dimensions and material mechanical properties of the dissimilar steel pipe includes: obtaining any material mechanical property among the geometric dimensions of the dissimilar steel pipe and the weld metal's yield strength, tensile strength, elastic modulus and Poisson's ratio, fracture toughness parameter, stress intensity factor, creep fracture parameter, creep strain coefficient and its exponent, creep crack propagation coefficient and its exponent, and fatigue crack propagation coefficient and its exponent.

[0008] Optionally, in one embodiment of this application, the conversion formula for the stress intensity factor is:

[0009]

[0010] Among them, K IC For type I fracture toughness, J IC J represents the integral fracture toughness, E represents the material's elastic modulus, and v represents Poisson's ratio.

[0011] Optionally, in one embodiment of this application, before comparing the failure assessment curve of the buried crack with the safety boundary based on the load ratio and the fracture ratio, the method further includes: determining the strain hardening coefficient of the material based on the ratio of the elastic modulus to the yield strength of the material; determining the load ratio based on the yield strength and tensile strength; and determining the failure assessment curve of the buried crack based on the strain hardening coefficient and the load ratio.

[0012] Optionally, in one embodiment of this application, the formula for calculating the equivalent stress by the load ratio is:

[0013]

[0014] Among them, P m For the primary membrane stress, P b Let ξ be the primary bending stress, γ be the crack location factor, γ be the depth scaling factor, and σ be the crack depth scaling factor. ref Calculate the equivalent stress for the load ratio.

[0015] Optionally, in one embodiment of this application, the creep crack propagation iteration formula is:

[0016]

[0017] Among them, a i For the half-depth of the crack in step i, The creep driving force at the crack tip is D0, where D0 and φ are material creep propagation parameters, Δt is the time step, and a is the creep driving force at the crack tip. i+1 For the (i+1)th step of the crack half-depth, c i Let be the half-length of the crack at step i.

[0018] Optionally, in one embodiment of this application, comparing the creep-dominant life and the creep-fatigue coupled life to generate the final remaining life of the dissimilar steel pipe includes: determining whether the creep-dominant life is lower than a preset life threshold of the creep-fatigue coupled life; if the creep-dominant life is lower than the preset life threshold of the creep-fatigue coupled life, then determining the final remaining life of the dissimilar steel pipe as the creep-dominant life.

[0019] A second aspect of this application provides a life assessment device for dissimilar steel pipes with buried cracks, comprising: an acquisition module for acquiring any pipe parameter from the geometric dimensions and material mechanical properties of the dissimilar steel pipe, and collecting any crack data from the depth, length, and distance of the buried crack from the pipe surface; a calculation module for calculating the service stress of primary membrane stress and primary bending stress based on the pipe parameter and the crack data, according to the pipe internal pressure, inner diameter, and wall thickness of the dissimilar steel pipe; a comparison module for calculating the load ratio and fracture ratio of the dissimilar steel pipe based on the service stress, comparing the failure assessment curve of the buried crack with the safety boundary based on the load ratio and the fracture ratio, generating comparison data, and determining whether the buried crack is within an acceptable range based on the comparison data; and a prediction module for predicting the buried crack... If the creep crack is within the acceptable range, the creep crack propagation rate in the depth direction is calculated using a preset constitutive model for creep crack propagation. Based on the creep crack propagation rate in the depth direction, the remaining life of the creep crack when it propagates to the critical depth is predicted to determine the creep-dominant life. An incremental calculation module is used to determine the stress intensity factor amplitude of the fatigue crack based on a preset load difference, and to calculate the crack propagation increment under the fatigue load based on the stress intensity factor amplitude, according to a preset fatigue cycle period and internal pressure fluctuation range. A determination module is used to determine the total crack propagation based on the crack propagation increment coupled with creep and fatigue propagation, and to determine the creep-fatigue coupled life based on the total crack propagation. An evaluation module is used to compare the creep-dominant life and the creep-fatigue coupled life to generate the final remaining life of the dissimilar steel pipe.

[0020] Optionally, in one embodiment of this application, the acquisition module includes: an acquisition unit, used to acquire any one of the following material mechanical properties of the dissimilar steel pipe: geometric dimensions and weld metal: yield strength, tensile strength, elastic modulus and Poisson's ratio, fracture toughness parameter, stress intensity factor, creep fracture parameter, creep strain coefficient and its exponent, creep crack propagation coefficient and its exponent, and fatigue crack propagation coefficient and its exponent.

[0021] Optionally, in one embodiment of this application, the conversion formula for the stress intensity factor is:

[0022]

[0023] Among them, K IC For type I fracture toughness, J IC J represents the integral fracture toughness, E represents the material's elastic modulus, and v represents Poisson's ratio.

[0024] Optionally, in one embodiment of this application, it further includes: a coefficient determination module, used to determine the strain hardening coefficient of the material based on the ratio of the elastic modulus to the yield strength of the material before comparing the failure assessment curve of the buried crack with the safety boundary based on the load ratio and the fracture ratio; a load ratio determination module, used to determine the load ratio based on the yield strength and tensile strength; and a curve determination module, used to determine the failure assessment curve of the buried crack based on the strain hardening coefficient and the load ratio.

[0025] Optionally, in one embodiment of this application, the formula for calculating the equivalent stress by the load ratio is:

[0026]

[0027] Among them, P m For the primary membrane stress, P b Let ξ be the primary bending stress, γ be the crack location factor, γ be the depth scaling factor, and σ be the crack depth scaling factor. ref Calculate the equivalent stress for the load ratio.

[0028] Optionally, in one embodiment of this application, the creep crack propagation iteration formula is:

[0029]

[0030] Among them, a i For the half-depth of the crack in step i, The creep driving force at the crack tip is D0, where D0 and φ are material creep propagation parameters, Δt is the time step, and a is the creep driving force at the crack tip. i+1 For the (i+1)th step of the crack half-depth, c i Let be the half-length of the crack at step i.

[0031] Optionally, in one embodiment of this application, the evaluation module includes: a judgment unit, used to judge whether the creep-dominant life is lower than a preset life threshold of the creep-fatigue coupled life; and a life determination unit, used to determine the final remaining life of the dissimilar steel pipe as the creep-dominant life when the creep-dominant life is lower than the preset life threshold of the creep-fatigue coupled life.

[0032] A third aspect of this application provides an electronic device, including: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the life assessment method for dissimilar steel pipes with buried cracks as described in the above embodiments.

[0033] A fourth aspect of this application provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described method for assessing the lifespan of dissimilar steel pipes with buried cracks.

[0034] This application embodiment can acquire pipeline parameters and crack data, calculate service stress and creep-fatigue life coupling assessment. By establishing a life assessment model that integrates failure assessment diagram and creep-fatigue coupling, when assessing the life of dissimilar steel pipelines with buried cracks, it overcomes the shortcomings of traditional single-mechanism models in responding insufficiently to material mismatch characteristics by simultaneously considering the interaction of high-temperature creep effect and start-up and shutdown load impact, improves the accuracy of life prediction, and ensures the reliability of the safe operation cycle and maintenance strategy formulation of thermal power generating units. Based on the different mechanical properties in the depth and length directions, it adopts differentiated stress intensity factor amplitudes to solve the problem of crack morphology prediction distortion caused by the anisotropy of dissimilar steel materials, so that the pipeline remaining life assessment results are consistent with the crack evolution law under actual service conditions.

[0035] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0036] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0037] Figure 1 This is a flowchart illustrating a method for assessing the lifespan of dissimilar steel pipes with buried cracks, according to an embodiment of this application.

[0038] Figure 2 This is an overall flowchart of a life assessment method for dissimilar steel pipes with buried cracks according to an embodiment of this application;

[0039] Figure 3 This is a schematic diagram of a life assessment device for dissimilar steel pipes with buried cracks, provided according to an embodiment of this application.

[0040] Figure 4 This is a schematic diagram of the structure of an electronic device provided according to an embodiment of this application. Detailed Implementation

[0041] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0042] The following describes, with reference to the accompanying drawings, a method, apparatus, equipment, and medium for assessing the lifespan of dissimilar steel pipelines with buried cracks according to embodiments of this application. Addressing the problems mentioned in the background art, such as prominent early failure issues, limited assessment methods, and bottlenecks in engineering applications, this application provides a method for assessing the lifespan of dissimilar steel pipelines with buried cracks. This method allows for the acquisition of pipeline parameters and crack data, calculation of service stress and creep-fatigue life coupling assessment, and the establishment of a lifespan assessment model that integrates a failure assessment diagram and creep-fatigue coupling. When assessing the lifespan of dissimilar steel pipelines with buried cracks, the interaction between high-temperature creep effects and start-up / shutdown load impacts is considered simultaneously, overcoming the shortcomings of traditional single-mechanism models in responding insufficiently to material mismatch characteristics. This improves the accuracy of lifespan prediction, ensures the reliability of the safe operation cycle and maintenance strategy formulation for thermal power generating units, and uses differentiated stress intensity factor amplitudes based on different mechanical properties in the depth and length directions to solve the problem of crack morphology prediction distortion caused by the anisotropy of dissimilar steel materials. This ensures that the pipeline's remaining lifespan assessment results closely match the crack evolution law under actual service conditions.

[0043] Specifically, Figure 1 This is a flowchart illustrating a method for assessing the lifespan of dissimilar steel pipes with buried cracks, as provided in an embodiment of this application.

[0044] like Figure 1 As shown, the method for assessing the lifespan of dissimilar steel pipes with buried cracks includes the following steps:

[0045] In step S101, any pipe parameter from the geometric dimensions and material mechanical properties of the dissimilar steel pipe is obtained, and any crack data from the depth, length and distance of the buried crack from the pipe surface is collected.

[0046] It is understood that the embodiments of this application can obtain pipeline parameters and crack data: collect the geometric dimensions and material mechanical properties of dissimilar steel pipelines, and measure the depth, length and distance from the pipeline surface of buried cracks.

[0047] This application embodiment establishes a dynamic feedback system based on on-site non-destructive testing. When assessing pipeline condition, it can collect data on crack size changes and material performance degradation in real time, enabling autonomous iterative optimization of assessment model parameters. This system changes the passive situation of traditional offline testing, which has a long cycle and cannot capture early damage evolution. It constructs a new technical paradigm for online life monitoring and risk early warning of megawatt units, providing timely and reliable data support for power companies' preventive maintenance decisions.

[0048] Optionally, in one embodiment of this application, obtaining any pipe parameter among the geometric dimensions and material mechanical properties of the dissimilar steel pipe includes: obtaining any material mechanical property among the geometric dimensions of the dissimilar steel pipe and the yield strength, tensile strength, elastic modulus and Poisson's ratio, fracture toughness parameter, stress intensity factor, creep fracture parameter, creep strain coefficient and its exponent, creep crack propagation coefficient and its exponent, fatigue crack propagation coefficient and its exponent.

[0049] It is understood that the material mechanical properties in the embodiments of this application include:

[0050] 1) Yield strength σ of weld metal s Tensile strength σ b Elastic modulus E and Poisson's ratio ν;

[0051] 2) Fracture toughness parameter J IC It can be converted into the stress intensity factor K by the following formula. IC ;

[0052] 3) Creep fracture parameters k and q, creep strain coefficient A and exponent n;

[0053] 4) Creep crack propagation coefficient D0 and exponent φ, fatigue crack propagation coefficient C and exponent m.

[0054] This application, through deep integration of structural integrity assessment and materials science theory, forms a multidisciplinary technical solution to address complex issues unique to dissimilar steel pipes, such as carbon migration and creep mismatch. This method not only accurately quantifies the stress redistribution effect at the material interface, but also innovatively correlates microstructure evolution with macroscopic crack propagation, filling the theoretical gap in the study of the evolution mechanism of buried cracks under high temperature and high pressure environments, and providing important technical reserves for the improvement of the safety assessment standard system for special equipment.

[0055] In one embodiment of this application, the conversion formula for the stress intensity factor is:

[0056]

[0057] Among them, K IC For type I fracture toughness, J IC J represents the integral fracture toughness, E represents the material's elastic modulus, and ν represents Poisson's ratio.

[0058] In actual implementation, the embodiments of this application can make the fracture toughness parameter J IC The stress intensity factor K is converted using the following formula. IC :

[0059]

[0060] Among them, K IC For type I fracture toughness, J IC J represents the integral fracture toughness, E is the material's elastic modulus, reflecting the material's stiffness, and v is Poisson's ratio, characterizing the material's lateral deformation capacity.

[0061] The fracture toughness conversion satisfies the following relationship: K IC Value and J IC The value, elastic modulus E, and Poisson's ratio v are related and satisfy the following conditions.

[0062] This application's embodiments innovatively introduce a directional crack propagation correction mechanism. When simulating the crack evolution process, based on the differences in mechanical properties of different regions of the pipeline, a targeted stress intensity factor amplitude calculation method is adopted. This mechanism considers the anisotropic characteristics of dissimilar steel weld regions, solves the problem of crack morphology prediction distortion caused by material property gradient changes, and makes the crack propagation law in the depth and length directions conform to the physical phenomena in the actual service environment, thereby improving the credibility of the remaining service life assessment results in engineering applications.

[0063] In step S102, based on any pipe parameter and any crack data, the service stress of primary membrane stress and primary bending stress is calculated according to the pipe internal pressure, inner diameter and wall thickness of the dissimilar steel pipe.

[0064] Specifically, the embodiments of this application can calculate the service stress based on any pipeline parameter and any crack data: determine the primary membrane stress and primary bending stress according to the pipeline internal pressure, inner diameter and wall thickness.

[0065] In step S103, based on the service stress, the load ratio and fracture ratio of the dissimilar steel pipe are calculated, and the failure assessment curve of the buried crack is compared with the safety boundary according to the load ratio and fracture ratio to generate comparison data. Based on the comparison data, it is determined whether the buried crack is within an acceptable range.

[0066] In actual implementation, based on service stress, the embodiments of this application can perform failure safety assessment: based on failure assessment diagram technology, the load ratio and fracture ratio are calculated, comparison data is generated by comparing the failure assessment curve with the safety boundary, and the crack is judged to be within an acceptable range based on the comparison data.

[0067] Among them, buried cracks must meet the following geometric constraints: the crack depth does not exceed 30% of the wall thickness; the crack length is not less than 4 times the depth; and the distance between the crack and the surface is greater than 0.5 mm and less than 80% of the wall thickness.

[0068] Optionally, in one embodiment of this application, before comparing the failure assessment curve of the buried crack with the safety boundary based on the load ratio and the fracture ratio, the method further includes: determining the strain hardening coefficient of the material based on the ratio of the material's elastic modulus to its yield strength; determining the load ratio based on the yield strength and tensile strength; and determining the failure assessment curve of the buried crack based on the strain hardening coefficient and the load ratio.

[0069] As one possible implementation, the boundary curve of the Failure Assessment Diagram (FAD) in this application embodiment is determined by the following parameters: the material strain hardening coefficient μ, which is the smaller of 0.001 times the ratio of elastic modulus to yield strength or 0.6; and the maximum load ratio Lrmax, which is the ratio of 50% of the sum of yield strength and tensile strength to yield strength.

[0070] In one embodiment of this application, the formula for calculating the equivalent stress by load ratio is as follows:

[0071]

[0072] Among them, P m For primary membrane stress, P b Let ξ be the primary bending stress, γ be the crack location factor, γ be the depth scaling factor, and σ be the crack depth scaling factor. ref Calculate the equivalent stress for the load ratio.

[0073] In step S104, if the buried crack is within an acceptable range, the creep crack propagation rate in the depth direction is calculated using a creep crack propagation preset constitutive model, and the remaining lifetime of the creep crack propagation to the critical depth is predicted based on the creep crack propagation rate in the depth direction, so as to determine the creep dominant lifetime.

[0074] In practical implementation, the embodiments of this application can perform creep life prediction: if the buried crack is within an acceptable range, a pre-defined constitutive model for creep crack propagation is used to calculate the crack propagation rate in the depth direction. Based on the crack propagation rate in the depth direction, the remaining life of the crack propagating to the critical depth is predicted through step-by-step iteration to determine the creep-dominated life. This application constructs an evaluation system that integrates multiple failure models. In the life assessment of dissimilar steel pipes with buried cracks, it fully considers the complex interaction between high-temperature creep effect and periodic start-up and shutdown loads, breaking through the technical limitations of traditional single-mechanism models in responding insufficiently to material performance mismatch. This system organically combines the safety boundary determination of the failure assessment diagram with the creep-fatigue coupled propagation mechanism, improving the accuracy of life prediction under ultra-supercritical conditions. It provides key theoretical support for formulating scientific maintenance strategies for thermal power generating units and ensures the long-term safe operation of energy infrastructure.

[0075] This application embodiment establishes a life assessment model that integrates a failure assessment map with creep-fatigue coupling. When assessing the life of dissimilar steel pipes with buried cracks, it simultaneously considers the interaction between high-temperature creep effect and start-up and shutdown load impact. This overcomes the shortcomings of traditional single-mechanism models in responding insufficiently to material mismatch characteristics, improves the accuracy of life prediction, and ensures the reliability of the safe operation cycle and maintenance strategy formulation of thermal power generating units.

[0076] In one embodiment of this application, the creep crack propagation iteration formula is:

[0077]

[0078] Among them, a i For the half-depth of the crack in step i, The creep driving force at the crack tip is D0, where D0 and φ are material creep propagation parameters, Δt is the time step, and a is the creep driving force at the crack tip. i+1 For the (i+1)th step of the crack half-depth, c i Let be the half-length of the crack at step i.

[0079] In step S105, the stress intensity factor amplitude of the fatigue crack is determined according to the preset load difference, and the crack propagation increment under fatigue load is calculated based on the stress intensity factor amplitude, according to the preset fatigue cycle period and internal pressure fluctuation range.

[0080] It is understood that the preset load difference in the embodiments of this application can be the maximum and minimum load difference; the preset fatigue cycle can be once every six months.

[0081] In actual implementation, the fatigue crack propagation calculation in this application embodiment satisfies the following: the stress intensity factor amplitude ΔK is determined according to the difference between the maximum and minimum loads, the fatigue cycle is loaded once every six months, and the internal pressure fluctuation range is 1.3 times the design pressure.

[0082] The embodiments of this application can use differentiated stress intensity factor amplitudes according to different mechanical properties in the depth and length directions to solve the problem of crack morphology prediction distortion caused by the anisotropy of dissimilar steel materials, so that the pipeline remaining service life assessment results are consistent with the crack evolution law under actual service conditions.

[0083] It should be noted that the preset load difference and preset fatigue cycle can be set by those skilled in the art according to the actual situation, and no specific restrictions are imposed here.

[0084] In step S106, the total crack propagation amount is determined based on the crack propagation increment coupled with creep and fatigue propagation amount, and the creep-fatigue coupled life is determined based on the total crack propagation amount.

[0085] In actual implementation, the embodiments of this application can perform creep-fatigue life coupling evaluation, based on the crack propagation increment coupling creep and fatigue propagation amount to determine the total crack propagation amount, and determine the creep-fatigue coupled life based on the total crack propagation amount.

[0086] The creep-fatigue coupling adopts a linear superposition model: the total crack depth increment is equal to the sum of creep propagation and fatigue propagation, and the crack length propagation is calculated using 90% of the stress intensity factor amplitude.

[0087] In step S107, the creep-dominant life and the creep-fatigue coupled life are compared to generate the final remaining life of the dissimilar steel pipe.

[0088] In actual implementation, the embodiments of this application can perform a comprehensive determination of remaining life: compare the creep-dominant life with the creep-fatigue coupled life, and take the minimum value as the final remaining life of the pipeline.

[0089] Optionally, in one embodiment of this application, comparing the creep-dominant life and the creep-fatigue coupling life to generate the final remaining life of the dissimilar steel pipe includes: determining whether the creep-dominant life is lower than a preset life threshold of the creep-fatigue coupling life; if the creep-dominant life is lower than the preset life threshold of the creep-fatigue coupling life, then determining the final remaining life of the dissimilar steel pipe as the creep-dominant life.

[0090] Specifically, the remaining life determination criteria in this application embodiment include: determining whether the creep-dominant life is lower than the preset life threshold of the creep-fatigue coupling life; if the creep life is lower than 50% of the coupling life, the creep life shall be used as the standard; when the crack depth exceeds 40% of the wall thickness, the pipeline is directly determined to have failed.

[0091] This application's embodiments pioneer a technical approach that combines engineering practicality with academic foresight. While ensuring that the assessment process strictly adheres to international standards and specifications, it achieves efficient solutions to complex mechanical models through intelligent algorithms. This method reduces reliance on the professional experience of operators, enabling precise life assessment technology to move from laboratory research to power plant field applications. It promotes the transformation of power industry equipment safety management from "post-event handling" to "pre-event prevention." At the engineering application level, it enhances the adaptability to the variable operating conditions of ultra-supercritical units, allowing life prediction results to dynamically respond to actual operating conditions such as start-up, shutdown, peak shaving, and load fluctuations. This provides power companies with a safety margin assessment scheme that strictly matches the real service environment.

[0092] Furthermore, this application constructs a closed-loop self-optimizing dynamic evaluation system, replacing the passive response mode of traditional offline detection, and creates a life prediction self-evolutionary system based on real-time data streams. By integrating online monitoring technologies such as micro-indentation hardness testing and nonlinear ultrasonic characterization, it achieves minute-level tracking of material performance degradation and crack propagation rate. The system uses intelligent learning algorithms to extract features from monitoring data and autonomously calibrate model parameters, enabling the evaluation model to continuously approach the real physical state as the service life progresses. This technological paradigm promotes the strategic transformation of power plant safety management from "periodic maintenance" to "condition-based maintenance," extending equipment availability while ensuring system safety, and reconstructing the methodology of full life-cycle management of energy infrastructure.

[0093] It should be noted that the preset lifespan threshold can be set by those skilled in the art according to the actual situation, and no specific restrictions are imposed here.

[0094] This application includes: Example 1

[0095] A reheater tube section of a 1,000 MW ultra-supercritical unit boiler uses dissimilar welded joints of T92 ferritic steel and Super304H austenitic steel. During routine non-destructive testing, buried cracks were found near the weld fusion line. The specific process of implementing this life assessment method is as follows:

[0096] Initial detection phase

[0097] A phased array ultrasonic testing device was used to perform a full circumference scan of the pipeline weld area. An elliptical buried defect was found 3 mm from the inner surface. Measurement confirmed that the crack depth was 2.2 mm and the length was 8.5 mm. The actual inner diameter of the pipeline is 36 mm and the wall thickness is 6.8 mm. The pipeline is in operation at a steam pressure of 32.8 MPa and a high temperature environment of 602 degrees Celsius. The operation records show that the pipeline has been started and stopped an average of 2.3 times per year for the past three years, with each start and stop accompanied by pressure fluctuations from 0 to 42.6 MPa.

[0098] Safety performance assessment phase

[0099] First, the circumferential stress of the pipeline was calculated to be 103.6 MPa. By analyzing the geometric characteristics of the crack location, the key parameters affecting the stress distribution were determined: the ratio of crack depth to wall thickness was 0.32, and the ratio of crack length to pipeline circumference was 0.07. Combined with the weld metal data retrieved from the material property database: the yield strength of nickel-based alloy 625 was 356 MPa, and the fracture toughness was 194 N / mm. The load ratio was calculated to be 0.41, and the fracture ratio was 0.05. The evaluation point was plotted on the failure assessment diagram and confirmed to be within the tolerance range of 0.12 within the safety boundary. Therefore, the pipeline was deemed to be able to continue operating.

[0100] Life prediction implementation phase

[0101] A creep-dominated crack propagation model was established: iterative calculations were performed with a step size of one hour, updating the crack depth value each time. Considering the high-temperature creep characteristics of the material: creep index 11.56, propagation coefficient 9.08, the crack was predicted to propagate from the initial depth of 2.2 mm to the critical value of 2.72 mm, which is 40% of the wall thickness, requiring 16,328 hours of operation time. Creep-fatigue coupled assessment was initiated simultaneously: based on the start-stop records, a load cycle was set every six months, and the fatigue propagation amount generated by each pressure fluctuation was calculated. The full stress intensity factor amplitude was used in the depth direction, and the 90% correction value was used in the length direction. After 16 cycles, the total propagation amount reached 0.38 mm.

[0102] Dynamic monitoring and verification

[0103] After 15,800 hours of operation, online micro-indentation testing was conducted: the measured crack depth was 4.92 mm, and the surface hardness decreased from the initial value of 215 Vickers hardness to 192 Vickers hardness. Based on the material degradation data, the creep model parameters were updated, and the remaining lifespan was corrected from 315 hours to 298 hours. Finally, the machine was shut down for replacement at 16,300 hours. The tube cutting and sampling showed that the actual crack depth was 5.05 mm, and the depth-to-length ratio was 0.51. Compared with the traditional evaluation method, this solution reduced the lifespan prediction error from 21.8% to 0.9%, avoiding unplanned downtime losses of 2.3 million yuan. At the same time, it accurately captured the crack propagation morphology characteristics. The traditional model predicted a depth-to-length ratio of 0.35, with a deviation of 31%.

[0104] This embodiment achieves life control of cracks in dissimilar steel pipelines by integrating multi-mechanism failure models and dynamic parameter correction, providing technical support for the safe operation of ultra-supercritical units.

[0105] Example 2

[0106] During a major overhaul of a supercritical thermal power plant, non-destructive testing of the boiler reheater system revealed an abnormal signal in a section of T92 / Super304H dissimilar steel welded pipe. The engineering team immediately initiated this life assessment process.

[0107] First, the basic parameters of the pipeline were collected. The inner diameter was measured to be 35 mm and the wall thickness to be 6.5 mm. The crack was located in the weld fusion zone, 3 mm from the inner surface, and was distributed in an elliptical shape with a depth of 2 mm and a length of 8 mm. The operation log confirmed that the pipeline had been in service for a long time in a high-temperature environment of 605 degrees Celsius, with the steam pressure stable at 33 MPa. On average, it was started and stopped twice a year for the past five years.

[0108] Based on measured data, the service stress of the pipeline was calculated, and the circumferential principal stress was determined to be 105 MPa. Subsequently, a failure safety assessment was carried out. Through dual calculations of load ratio and fracture ratio, it was confirmed that the assessment point was located at 0.1 within the safety boundary of the failure assessment diagram, and the pipeline was determined to be able to continue operating. The pipeline then entered the creep life prediction stage. The parameters of the nickel-based alloy weld material database were called to establish a crack depth propagation model. Through step-by-step iterative calculations, it was found that under the pure creep mechanism, the crack propagation to the critical depth would take 16,567 hours.

[0109] A simultaneous creep-fatigue coupled assessment was initiated, treating start-up and shutdown operations as sources of fatigue load. The expansion increment caused by each pressure fluctuation was calculated. The coupled model showed that after sixteen start-up and shutdown cycles, the crack depth would increase from the initial two millimeters to five .2 millimeters. The prediction results of the two mechanisms were compared, and the minimum value was taken as the final remaining life. The pipeline was shut down for verification after 16,300 hours of actual operation. The crack depth was measured at five .1 millimeters after pipe cutting and sampling, with a deviation of only two percent from the predicted value. Based on the assessment results, the power plant scheduled maintenance two weeks in advance, avoiding unplanned downtime losses of more than two million yuan. This case verified the accuracy and engineering applicability of the method in predicting the crack life of dissimilar steel pipelines.

[0110] Example 3

[0111] During a routine inspection of an ultra-supercritical unit at a thermal power plant, an abnormal signal was discovered in a section of a welded pipe between ferritic and austenitic dissimilar steels in the boiler reheater system. The engineering team immediately implemented this life assessment method:

[0112] First, a phased array detection device was used to scan the weld area of ​​the pipeline. The inner diameter of the pipeline was measured to be 36 mm and the wall thickness to be 6.8 mm. The crack was located near the fusion line, and was an elliptical buried defect with a depth of 2.2 mm, a length of 8.5 mm, and a distance of 3 mm from the inner surface. The operation records confirmed that the pipeline had been in operation for a long time in a high-temperature environment above 600 degrees Celsius, with the steam pressure maintained at 33 MPa. In recent years, it has undergone an average of two start-up and shutdown operations per year.

[0113] Based on the measured parameters, the circumferential principal stress of the pipeline was calculated, and the stress level was found to be about 104 MPa. Subsequently, a safety performance assessment was carried out. Through dual calculation of load ratio and fracture ratio, it was confirmed that the assessment point was within the safety boundary range of the failure assessment diagram, and the pipeline was determined to be able to continue operating. The pipeline then entered the life prediction stage. The creep performance parameters in the nickel-based alloy weld material database were called to establish a crack depth propagation model. After step-by-step iterative calculation, it was found that under the pure creep mechanism, it would take more than 16,000 hours for the crack to propagate to the critical depth.

[0114] A simultaneous creep fatigue coupled assessment was initiated, treating unit start-up and shutdown operations as sources of fatigue load. The expansion increment caused by each pressure fluctuation was calculated. The coupled model showed that after sixteen load cycles, the crack depth would increase from the initial value to more than five millimeters. The prediction results of the two mechanisms were compared, and the smaller value was taken as the final remaining life. The pipeline was shut down for verification when it reached 98% of the predicted life. The actual crack size measured by cutting the pipe and taking samples deviated from the predicted value by less than 3%. Based on the assessment results, the power plant arranged maintenance plans in advance, successfully avoiding unplanned shutdown accidents and saving more than two million yuan in maintenance costs. This case verified the engineering applicability and prediction accuracy of this method in the assessment of hidden defects in dissimilar steel pipelines.

[0115] Example 4

[0116] 1. Pipeline safety assessment based on failure assessment diagram:

[0117] The failure assessment diagram uses Lr and Kr as parameters to represent the structural state under normal temperature conditions. The horizontal axis parameter Lr indicates the degree to which the load is close to the plastic yield limit load; the vertical axis parameter Kr indicates the degree to which the fracture driving force of the defective structure is close to linear elastic fracture.

[0118] Calculate the L of the pipeline containing defects based on the defect size, stress level, and pipeline specifications. r ′ and K r The defect is marked as '' and drawn on the FAD failure assessment diagram. If it is inside the boundary line, it means that the defect is acceptable for the pipeline and can continue to operate; if it falls outside the boundary, it means that the defect is unacceptable and must be dealt with.

[0119] The boundary line formula is:

[0120]

[0121] The cutoff line is

[0122]

[0123] Where Lr is the load ratio, σ s The material's yield strength is represented by μ, the strain hardening coefficient is μ, and the hardening exponent is N′. For the maximum load ratio, σ b E represents the tensile strength, and E represents the elastic modulus of the material.

[0124] 2. Fracture assessment of dissimilar steel pipes with buried cracks

[0125] Buried cracks in defective dissimilar steel pipes can be regularized into elliptical buried cracks, where 2a represents the defect depth, a represents the defect half-depth, 2c represents the defect length, c represents the defect half-length, p represents the distance of the defect from the surface, and B represents the pipe thickness.

[0126] The calculations for the plastic instability factor and fracture factor of a pipeline subjected to internal pressure are as follows:

[0127] The formula for calculating the load ratio Lr is as follows:

[0128]

[0129] in:

[0130]

[0131] Where, σ s P represents the yield strength of the material. b P represents the primary bending stress. m P1 represents the primary stress, P1 is the distance from the nearest point of the defect to the surface, B represents the pipe thickness, a represents the defect half-depth, c represents the defect half-length, ξ is the crack location factor, γ is the depth scaling factor, and σ represents the primary stress. ref Calculate the equivalent stress for the load ratio.

[0132] The formula for calculating the fracture ratio Kr is as follows:

[0133]

[0134] Where G is the elastoplastic interference effect coefficient between two adjacent defects, and its value is taken as 1.0. The stress intensity factor caused by primary stress. ρ is the stress intensity factor caused by secondary stress, and ρ is the plasticity correction factor.

[0135] Kp is used to evaluate the fracture toughness of a material, which is the fracture toughness KIC value divided by a specified safety factor.

[0136]

[0137] The value of Ψ1 can be determined according to Determine that Lr is the load ratio, Ψ I This is the plasticity correction factor, based on L. r The value is calculated in segments.

[0138]

[0139] Among them, P m P represents primary stress. b Q represents the primary bending stress. m For secondary membrane stress, Q b For secondary bending stress, e is the distance from the crack centerline to the middle surface of the pipe, a represents the half-depth of the defect, c represents the half-length of the defect, and B represents the thickness of the pipe.

[0140] In this assessment, the defect dimensions are: crack depth 2a = 2 mm, crack width 2c = 8 mm, and defect distance from the surface p = 3 mm. The reliability assessment, based on stress calculations using the internal steam pressure of the dissimilar steel joint pipe, yields a load ratio Lr = 0.39 and a fracture ratio Kr = 0.04, calculated using the above formula.

[0141] 3. Evaluation of creep crack propagation in defective dissimilar steel joints

[0142] Evaluation criteria for creep crack propagation in defective dissimilar steel joints:

[0143] Since the pipeline primarily considers long-term service loads, calculations are performed based on 1.3 times the steam pressure to ensure safety. The presence of defects increases local stress concentration in the defective structure, affecting its creep rupture life. Therefore, it is necessary to evaluate the variation in creep rupture life caused by local stress concentration. The creep rupture life is shown in the following formula:

[0144]

[0145] Where σ is the applied stress, t r denoted as creep rupture time, where k and q are creep rupture parameters.

[0146] Meanwhile, the creep strain of a defective structure will gradually accumulate and increase during long-term service. The Norton power-law constitutive model is used to reflect the accumulation law of creep strain under different stresses, as shown in the following formula:

[0147]

[0148] Where k and q are parameters that determine creep failure time (life), and the unit is MPa hq; Let σ be the minimum creep strain rate, σ be the applied stress, A be the creep strain coefficient in MPa-nh-1, and n be the creep strain exponent. The creep properties of the material at the evaluation temperature are obtained by using the minimum creep rupture time specified in ASME BPVC and the mean isochronous stress-strain curve, and fitting the curve using the least squares method.

[0149] The constitutive model for creep crack propagation rate used in creep crack propagation assessment is shown in the following formula:

[0150] da / dt=D0(C * ) φ

[0151] Where C* is the high-temperature fracture constant, φ is the creep crack propagation index, D0 is the material creep propagation parameter, da is the crack depth, and dt is the time.

[0152] Assessment results of creep crack propagation in defective dissimilar steel joints:

[0153] Based on the above data, the remaining life of creep crack propagation in a pipeline structure with defective dissimilar steel joints is calculated. To prevent pipeline leakage, the calculation program is interrupted when the defect depth a / B equals 0.8. The time required to reach this propagation amount is the remaining life of creep crack propagation.

[0154] The creep crack propagation calculation is performed using the following formula, and the specific method is as follows:

[0155]

[0156] Where D0 and φ are both material creep propagation parameters, a i For the half-depth of the crack in step i, a i+1 For the (i+1)th step of the crack half-depth, c i Let be the half-length of the crack at step i, and t be the minimum time interval for calculating creep crack propagation, which is set to 1 hour in this evaluation. The high-temperature fracture constant C* can be calculated using the following formula:

[0157]

[0158] Among them, K o,P (a i ,c i K represents the stress intensity factor at the crack surface caused by primary stress. d,P (a i ,c i The stress intensity factor at the deepest point of the crack caused by primary stress, a i For the half-depth of the crack in step i, c i Let σ be the half-length of the crack at step i. ref Calculate the equivalent stress for the load ratio.

[0159] According to calculations, when the crack reaches half its depth 'a' of 2.6 mm, i.e. 2a / B = 0.8, the required time is 16567 hours. At this time, the crack size is crack depth 2a = 5.2 mm and crack length 2c = 9.34 mm.

[0160] 4. Creep-fatigue crack propagation assessment of defective dissimilar steel joints

[0161] Evaluation results of creep-fatigue crack propagation in defective dissimilar steel joints:

[0162] Based on the above data, the remaining life of creep-fatigue crack propagation in the pipeline structure with defective dissimilar steel joints is calculated. To prevent pipeline leakage, the calculation program is interrupted when the defect depth a / B equals 0.8. The time required to reach this propagation amount is the remaining life of creep-fatigue crack propagation.

[0163] In the creep-fatigue crack propagation process, the crack propagation amount includes two parts: creep crack propagation and fatigue crack propagation. Creep crack propagation can be calculated using the methods employed. Fatigue crack propagation can be calculated using the following methods:

[0164] a i+1 =a i +C[(ΔK a ) i ] m i = 0, 1, ..., n;

[0165] c i+1 =c i +C[(0.9ΔK c ) i ] m i = 0, 1, ..., n;

[0166]

[0167] in, These are the stress intensity factors at the crack surface under the maximum and minimum cyclic loading conditions, respectively. These are the stress intensity factors at the deepest point of the crack under maximum and minimum cyclic loading conditions, respectively, calculated according to GB / T 19624. i For the half-depth of the crack in step i, a i+1 For the (i+1)th step of the crack half-depth, c i+1 Let n be the crack half-length at step i+1, n be the creep strain exponent, and c be the crack half-length at step i+1. i Let be the half-length of the crack at step i.

[0168] The total crack propagation can be calculated using the following formula:

[0169] a = a c +a f

[0170] c = c c +c f

[0171] Among them, a c a represents the creep portion of the crack's propagation in the depth direction. f c represents the fatigue portion of the crack propagation in the depth direction. c c represents the creep portion of the crack length extension. f This refers to the fatigue portion of the crack propagation along its length.

[0172] The evaluation assumes a fatigue cycle every six months. Based on the above parameters, the time required to reach a crack depth 2a of 5.2 mm is 16526 hours, or 8 fatigue cycles. At this point, the crack depth 2a = 5.2 mm and the crack length 2c = 9.34 mm.

[0173] Specifically, it can be combined with Figure 2 As shown, the working principle of the life assessment method for dissimilar steel pipes with buried cracks in this application is explained in detail with a specific embodiment.

[0174] like Figure 2 As shown, embodiments of this application may include the following steps:

[0175] Step S201: Obtain pipeline parameters and crack data.

[0176] Step S202: Calculate service stress.

[0177] Step S203: Failure safety assessment.

[0178] Step S204: Determine if it is safe? If yes, proceed to step S205; if no, proceed to step S206.

[0179] Step S205: Predict creep life.

[0180] Step S206: End / Repair.

[0181] Step S207: Coupled creep-fatigue.

[0182] Step S208: Comprehensive determination of lifespan.

[0183] Step S209: Output report.

[0184] The life assessment method for dissimilar steel pipelines with buried cracks proposed in this application can obtain pipeline parameters and crack data, calculate service stress and creep-fatigue life coupling assessment, and establish a life assessment model that integrates failure assessment diagram and creep-fatigue coupling. When assessing the life of dissimilar steel pipelines with buried cracks, the interaction between high-temperature creep effect and start-up and shutdown load impact is considered simultaneously, overcoming the shortcomings of traditional single-mechanism models in responding insufficiently to material mismatch characteristics, improving the accuracy of life prediction, and ensuring the reliability of the safe operation cycle and maintenance strategy formulation of thermal power generating units. Differentiated stress intensity factor amplitudes are adopted according to different mechanical properties in the depth and length directions to solve the problem of crack morphology prediction distortion caused by the anisotropy of dissimilar steel materials, so that the pipeline remaining life assessment results are consistent with the crack evolution law under actual service conditions.

[0185] Next, referring to the accompanying drawings, a life assessment device for dissimilar steel pipes with buried cracks according to an embodiment of this application is described.

[0186] Figure 3 This is a schematic diagram of the life assessment device for dissimilar steel pipes with buried cracks, according to an embodiment of this application.

[0187] like Figure 3 As shown, the life assessment device 10 for dissimilar steel pipes with buried cracks includes: an acquisition module 100, a calculation module 200, a comparison module 300, a prediction module 400, an incremental calculation module 500, a determination module 600, and an assessment module 700.

[0188] Specifically, the acquisition module 100 is used to acquire any pipe parameter from the geometric dimensions and material mechanical properties of dissimilar steel pipes, and to collect any crack data from the depth, length and distance of the buried crack from the pipe surface.

[0189] The calculation module 200 is used to calculate the service stress of primary membrane stress and primary bending stress based on any pipe parameter and any crack data, according to the pipe internal pressure, inner diameter and wall thickness of dissimilar steel pipes.

[0190] The comparison module 300 is used to calculate the load ratio and fracture ratio of dissimilar steel pipes based on service stress, and to compare the failure assessment curve of buried cracks with the safety boundary based on the load ratio and fracture ratio, generate comparison data, and determine whether the buried cracks are within an acceptable range based on the comparison data.

[0191] The prediction module 400 is used to calculate the propagation rate of the creep crack in the depth direction using a pre-defined constitutive model of creep crack propagation when the buried crack is within an acceptable range, and to predict the remaining lifetime of the creep crack propagation to the critical depth based on the propagation rate in the depth direction, so as to determine the creep-dominant lifetime.

[0192] The incremental calculation module 500 is used to determine the stress intensity factor amplitude of the fatigue crack based on the preset load difference, and to calculate the crack propagation increment under fatigue load based on the stress intensity factor amplitude, according to the preset fatigue cycle period and internal pressure fluctuation range.

[0193] The determination module 600 is used to determine the total crack propagation based on the crack propagation increment coupled with creep and fatigue propagation, and to determine the creep-fatigue coupled life based on the total crack propagation.

[0194] Evaluation module 700 is used to compare creep-dominated life and creep-fatigue coupled life to generate the final remaining life of dissimilar steel pipes.

[0195] Optionally, in one embodiment of this application, the acquisition module 100 includes: an acquisition unit.

[0196] The acquisition unit is used to acquire any one of the following material mechanical properties of dissimilar steel pipes: geometric dimensions and weld metal: yield strength, tensile strength, elastic modulus and Poisson's ratio, fracture toughness parameters, stress intensity factor, creep fracture parameters, creep strain coefficient and its exponent, creep crack propagation coefficient and its exponent, and fatigue crack propagation coefficient and its exponent.

[0197] Optionally, in one embodiment of this application, the conversion formula for the stress intensity factor is:

[0198]

[0199] Among them, K IC For type I fracture toughness, J IC J represents the integral fracture toughness, E represents the material's elastic modulus, and v represents Poisson's ratio.

[0200] Optionally, in one embodiment of this application, the life assessment device 10 for dissimilar steel pipes with buried cracks further includes: a coefficient determination module, a load ratio determination module, and a curve determination module.

[0201] The coefficient determination module is used to determine the strain hardening coefficient of the material based on the ratio of the material's elastic modulus to its yield strength before comparing the failure assessment curve of the buried crack with the safety boundary based on the load ratio and fracture ratio.

[0202] The load ratio determination module is used to determine the load ratio based on the yield strength and tensile strength.

[0203] The curve determination module is used to determine the failure assessment curve for buried cracks based on the strain hardening coefficient and load ratio.

[0204] Optionally, in one embodiment of this application, the formula for calculating the equivalent stress by load ratio is:

[0205]

[0206] Among them, P m For primary membrane stress, P b Let ξ be the primary bending stress, γ be the crack location factor, γ be the depth scaling factor, and σ be the crack depth scaling factor. ref Calculate the equivalent stress for the load ratio.

[0207] Optionally, in one embodiment of this application, the creep crack propagation iteration formula is:

[0208]

[0209] Among them, a i For the half-depth of the crack in step i, The creep driving force at the crack tip is D0, where D0 and φ are material creep propagation parameters, Δt is the time step, and a is the creep driving force at the crack tip. i+1 For the (i+1)th step of the crack half-depth, c i Let be the half-length of the crack at step i.

[0210] Optionally, in one embodiment of this application, the evaluation module 700 includes a judgment unit and a lifetime determination unit.

[0211] The judgment unit is used to determine whether the creep-dominant lifetime is lower than the preset lifetime threshold of the creep-fatigue coupled lifetime.

[0212] The life determination unit is used to determine the final remaining life of dissimilar steel pipes as the creep-dominant life when the creep-dominant life is lower than the preset life threshold of the creep-fatigue coupled life.

[0213] It should be noted that the explanation of the above-mentioned embodiment of the life assessment method for dissimilar steel pipes with buried cracks also applies to the life assessment device for dissimilar steel pipes with buried cracks in this embodiment, and will not be repeated here.

[0214] The life assessment device for dissimilar steel pipelines with buried cracks proposed in this application can acquire pipeline parameters and crack data, calculate service stress and creep-fatigue life coupling assessment, and establish a life assessment model that integrates failure assessment diagram and creep-fatigue coupling. When assessing the life of dissimilar steel pipelines with buried cracks, it simultaneously considers the interaction between high-temperature creep effect and start-up and shutdown load impact, overcoming the shortcomings of traditional single-mechanism models in responding insufficiently to material mismatch characteristics, improving the accuracy of life prediction, and ensuring the reliability of the safe operation cycle and maintenance strategy formulation of thermal power generating units. Based on the different mechanical properties in the depth and length directions, it adopts differentiated stress intensity factor amplitudes to solve the problem of crack morphology prediction distortion caused by the anisotropy of dissimilar steel materials, so that the pipeline remaining life assessment results are consistent with the crack evolution law under actual service conditions.

[0215] Figure 4 A schematic diagram of the structure of an electronic device provided in an embodiment of this application. The electronic device may include:

[0216] The memory 401, the processor 402, and the computer program stored on the memory 401 and capable of running on the processor 402.

[0217] When the processor 402 executes the program, it implements the life assessment method for dissimilar steel pipes with buried cracks provided in the above embodiments.

[0218] Furthermore, electronic devices also include:

[0219] Communication interface 403 is used for communication between memory 401 and processor 402.

[0220] The memory 401 is used to store computer programs that can run on the processor 402.

[0221] The memory 401 may include high-speed RAM memory, and may also include non-volatile memory, such as at least one disk storage device.

[0222] If the memory 401, processor 402, and communication interface 403 are implemented independently, then the communication interface 403, memory 401, and processor 402 can be interconnected via a bus to complete communication between them. The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus, etc. Buses can be divided into address buses, data buses, control buses, etc. For ease of representation, Figure 4 The bus is represented by a single thick line, but this does not mean that there is only one bus or one type of bus.

[0223] Optionally, in a specific implementation, if the memory 401, processor 402, and communication interface 403 are integrated on a single chip, then the memory 401, processor 402, and communication interface 403 can communicate with each other through an internal interface.

[0224] Processor 402 may be a central processing unit (CPU), an application specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of this application.

[0225] This embodiment also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described method for assessing the lifespan of dissimilar steel pipes with buried cracks.

[0226] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0227] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "N" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0228] Any process or method described in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or N executable instructions for implementing custom logic functions or processes, and the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as should be understood by those skilled in the art to which embodiments of this application pertain.

[0229] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0230] It should be understood that the various parts of this application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, the N steps or methods can be implemented using software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0231] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

[0232] Furthermore, the functional units in the various embodiments of this application can be integrated into a processing module, or each unit can exist physically separately, or two or more units can be integrated into a module. The integrated module can be implemented in hardware or as a software functional module. If the integrated module is implemented as a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium.

[0233] The storage medium mentioned above can be a read-only memory, a disk, or an optical disk, etc. Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of this application.

Claims

1. A method for assessing the lifespan of dissimilar steel pipes containing buried cracks, characterized in that, Includes the following steps: Obtain any pipe parameter from the geometric dimensions and material mechanical properties of dissimilar steel pipes, and collect any crack data from the depth, length, and distance of the buried crack from the pipe surface; Based on any of the pipe parameters and any of the crack data, the service stresses of the primary membrane stress and primary bending stress are calculated according to the pipe internal pressure, inner diameter and wall thickness of the dissimilar steel pipe. Based on the service stress, the load ratio and fracture ratio of the dissimilar steel pipe are calculated, and the failure assessment curve of the buried crack is compared with the safety boundary according to the load ratio and the fracture ratio to generate comparison data. Based on the comparison data, it is determined whether the buried crack is within an acceptable range. If the buried crack is within the acceptable range, the creep crack propagation rate in the depth direction is calculated using a creep crack propagation preset constitutive model, and based on the creep crack propagation rate in the depth direction, the remaining lifetime of the creep crack propagating to the critical depth is predicted to determine the creep-dominant lifetime. The stress intensity factor amplitude of the fatigue crack is determined based on the preset load difference, and the crack propagation increment under the fatigue load is calculated based on the stress intensity factor amplitude, according to the preset fatigue cycle period and internal pressure fluctuation range. Based on the crack propagation increment coupled with creep and fatigue propagation, the total crack propagation is determined, and the creep-fatigue coupled life is determined based on the total crack propagation. The creep-dominant lifetime and the creep-fatigue coupled lifetime are compared to generate the final remaining lifetime of the dissimilar steel pipe.

2. The method for assessing the lifespan of dissimilar steel pipes with buried cracks according to claim 1, characterized in that, The acquisition of any pipe parameter from the geometric dimensions and material mechanical properties of dissimilar steel pipes includes: Obtain any one of the following material mechanical properties of the dissimilar steel pipe: geometric dimensions and weld metal: yield strength, tensile strength, elastic modulus and Poisson's ratio, fracture toughness parameter, stress intensity factor, creep fracture parameter, creep strain coefficient and its exponent, creep crack propagation coefficient and its exponent, and fatigue crack propagation coefficient and its exponent.

3. The method for assessing the lifespan of dissimilar steel pipes with buried cracks according to claim 2, characterized in that, The conversion formula for the stress intensity factor is: Among them, K IC For type I fracture toughness, J IC J represents the integral fracture toughness, E represents the material's elastic modulus, and v represents Poisson's ratio.

4. The method for assessing the lifespan of dissimilar steel pipes with buried cracks according to claim 1, characterized in that, Before comparing the failure assessment curve of the buried crack with the safety boundary based on the load ratio and the fracture ratio, the method further includes: The strain hardening coefficient of the material is determined based on the ratio of its elastic modulus to its yield strength. The load ratio is determined based on the yield strength and tensile strength. The failure assessment curve of the buried crack is determined based on the strain hardening coefficient and the load ratio.

5. The method for assessing the lifespan of dissimilar steel pipes with buried cracks according to claim 1, characterized in that, The formula for calculating equivalent stress based on the load ratio is as follows: Among them, P m For the primary membrane stress, P b Let ξ be the primary bending stress, γ be the crack location factor, γ be the depth scaling factor, and σ be the crack depth scaling factor. ref Calculate the equivalent stress for the load ratio.

6. The method for assessing the lifespan of dissimilar steel pipes with buried cracks according to claim 1, characterized in that, The propagation iteration formula for the creep crack is: Among them, a i For the half-depth of the crack in step i, The creep driving force at the crack tip is D0, where D0 and φ are material creep propagation parameters, Δt is the time step, and a is the creep driving force at the crack tip. i+1 For the (i+1)th step of the crack half-depth, c i Let be the half-length of the crack at step i.

7. The method for assessing the lifespan of dissimilar steel pipes with buried cracks according to claim 1, characterized in that, The comparison of the creep-dominant life and the creep-fatigue coupled life to generate the final remaining life of the dissimilar steel pipe includes: Determine whether the creep-dominant lifetime is lower than a preset lifetime threshold for the creep-fatigue coupled lifetime; If the creep-dominant life is lower than the preset life threshold of the creep-fatigue coupled life, then the final remaining life of the dissimilar steel pipe is determined to be the creep-dominant life.

8. A life assessment device for dissimilar steel pipes with buried cracks, characterized in that, include: The acquisition module is used to acquire any pipe parameter from the geometric dimensions and material mechanical properties of dissimilar steel pipes, and to collect any crack data from the depth, length and distance of the buried crack from the pipe surface. The calculation module is used to calculate the service stress of primary membrane stress and primary bending stress based on any of the pipe parameters and any of the crack data, according to the pipe internal pressure, inner diameter and wall thickness of the dissimilar steel pipe. The comparison module is used to calculate the load ratio and fracture ratio of the dissimilar steel pipe based on the service stress, and compare the failure assessment curve of the buried crack with the safety boundary according to the load ratio and the fracture ratio to generate comparison data, and determine whether the buried crack is within an acceptable range based on the comparison data. The prediction module is used to calculate the propagation rate of the creep crack in the depth direction using a preset constitutive model of creep crack propagation when the buried crack is within the acceptable range, and to predict the remaining lifetime of the creep crack to the critical depth based on the propagation rate in the depth direction, so as to determine the creep-dominant lifetime. The incremental calculation module is used to determine the stress intensity factor amplitude of the fatigue crack based on the preset load difference, and to calculate the crack propagation increment under the fatigue load based on the stress intensity factor amplitude, according to the preset fatigue cycle period and internal pressure fluctuation range. The determination module is used to determine the total crack propagation amount based on the crack propagation increment coupled with creep and fatigue propagation amount, and to determine the creep-fatigue coupled life based on the total crack propagation amount. An evaluation module is used to compare the creep-dominant life and the creep-fatigue coupled life to generate the final remaining life of the dissimilar steel pipe.

9. An electronic device, characterized in that, include: The memory, the processor, and the computer program stored in the memory and executable on the processor, the processor executing the program to implement the life assessment method for dissimilar steel pipes with buried cracks as described in any one of claims 1-7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, The program is executed by the processor to implement the life assessment method for dissimilar steel pipes with buried cracks as described in any one of claims 1-7.

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