Method for evaluating residual strength of pipeline with corrosion defects under blasting vibration action

Abstract

The application discloses a method for evaluating the residual strength of a pipeline with corrosion defects under blasting vibration, and belongs to the technical field of oil and gas pipeline safety evaluation. In view of the problem that the traditional method only considers the corrosion geometric thinning and ignores the material dynamic performance degradation and spatial non-uniform distribution, leading to distorted evaluation, the application reconstructs the corrosion morphology based on detection data, constructs a corrosion damage variable, calibrates the damage-strain rate-material parameter mapping relationship through a mechanical test, establishes an explicit dynamic model of a pipeline-defect-soil-blast source, realizes non-uniform assignment of material performance in the corrosion area by using the UMAT subprogram of LS-DYNA, obtains stress, strain and damage state through nonlinear dynamic analysis, and completes the residual strength evaluation. The application couples the geometric defects and material degradation effect for the first time, greatly improves the evaluation accuracy and engineering applicability, and provides support for the safety control of pipeline blasting construction.

Description

Technical Field

[0001] This invention relates to the field of oil and gas pipeline safety assessment technology, specifically to a method for accurately assessing the residual strength of buried pipelines with corrosion defects under blasting vibration loads, simultaneously considering the effects of geometric thinning defects due to corrosion and the non-uniform degradation of material dynamic properties. Background Technology

[0002] During long-term service, buried oil and gas pipelines are prone to localized corrosion defects on their outer walls due to soil corrosion, aging and damage to the anti-corrosion layer, and stray currents. When blasting vibration loads generated during engineering operations such as tunnel blasting and excavation act on adjacent pipelines, the stress concentration from corrosion defects and the superposition of dynamic loads can easily induce plastic deformation or even failure of the pipeline. Therefore, conducting residual strength assessments of pipelines under such conditions is of significant engineering importance.

[0003] Existing assessment and numerical simulation studies mostly rely on LS-DYNA to establish vibration models of corroded pipelines during bursts, analyzing the impact of corrosion degree on pipeline vibration and stress characteristics. These studies generally suffer from the same technical limitation: they merely equate corrosion to a reduction in the geometric thickness of the pipe wall, assuming that the mechanical properties of the corroded region are consistent with the parent material.

[0004] The actual corrosion process not only alters geometric dimensions but also leads to the degradation of intrinsic material properties, such as hydrogen-induced damage and the accumulation of micropore damage, directly affecting the plasticity, toughness, and dynamic load-bearing capacity of pipeline steel. Existing technologies have three significant shortcomings: first, they only consider geometric thinning, ignoring material degradation effects, resulting in unsafe assessments; second, they fail to establish a quantitative mapping relationship between corrosion morphology parameters and the dynamic mechanical properties of the material, making quantitative calculation impossible; and third, they do not utilize the UMAT subroutine to assign non-uniform field values ​​to material properties in the corrosion region, making it difficult to characterize the actual spatial distribution differences in corrosion and limiting simulation accuracy.

[0005] Therefore, there is a need for a pipeline residual strength assessment method that simultaneously couples corrosion geometric thinning and material non-uniform degradation effects within the framework of blasting vibration dynamic analysis, in order to solve the problems of inaccurate assessment and difficulty in engineering application of existing technologies. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for assessing the residual strength of pipelines with corrosion defects under blasting vibration. This method establishes a quantitative degradation mapping relationship between corrosion damage variables and material dynamic mechanical property parameters. Within the LS-DYNA explicit dynamic analysis framework, it simultaneously considers both geometric thinning and material softening effects. Furthermore, it uses the UMAT subroutine to refine the assignment of non-uniform degradation fields of material properties in the corrosion zone, significantly improving the accuracy of safety assessment for pipelines corroded under blasting vibration.

[0007] To achieve the above objectives, this invention provides a method for evaluating the residual strength of corrosion-damaged pipelines under blasting vibration, comprising the following steps: S1: Obtain non-destructive testing data of the corrosion area of ​​the buried pipeline to be evaluated, reconstruct the corrosion geometry based on the testing data, and extract corrosion characteristic parameters; the corrosion characteristic parameters include at least one of corrosion depth percentage, pitting density, corrosion area occupancy ratio, and corrosion depth variation coefficient. S2: Construct material corrosion damage variables to characterize the degree of material performance degradation based on corrosion type and corresponding corrosion characteristic parameters; S3: Based on dynamic mechanical experiments, calibrate the degradation mapping relationship between material corrosion damage variables, strain rate, and dynamic performance parameters, and calculate the degradation dynamic material properties corresponding to each spatial location within the corrosion area. S4: Establish an explicit dynamic finite element model that includes the pipeline, corrosion geometry, soil medium, and blast source. Using the LS-DYNA user-defined material subroutine UMAT, assign corresponding degraded dynamic material properties to the corrosion zone elements according to their spatial location. Apply blasting vibration load to carry out nonlinear transient dynamic analysis. S5: Extract the equivalent stress peak and equivalent plastic strain of key parts in the corrosion area from the kinetic analysis results. The equivalent plastic strain is the equivalent plastic deformation accumulated by the material element during dynamic loading. Based on the above results, evaluate the remaining strength safety status of the pipeline under blasting vibration.

[0008] Based on the above technical solutions, preferably, the non-destructive testing data in step S1 is obtained by any one of ultrasonic testing, laser three-dimensional scanning, or magnetic flux leakage internal testing; the corrosion geometric morphology model is obtained by reverse reconstruction of point cloud data or by geometric parameterization modeling of corrosion defects, and the modeling accuracy matches the resolution of the testing data.

[0009] Based on the above technical solutions, preferably, the corrosion damage variable in step S2 is defined differently according to the corrosion type: Uniform corrosion / localized corrosion: D=(d / t)×α, where d is the localized corrosion depth, t is the original pipe wall thickness, and α is the corrosion morphology correction coefficient, with a value of 0.8~1.2; Pitting corrosion clusters: D=f(R) wt ,m), where R wt The remaining wall thickness ratio is m, and the pitting corrosion area occupancy ratio is m. Hydrogen-induced damage corrosion: A two-parameter damage model was adopted, D total =D G +β·D H D G D is the geometric corrosion damage variable. H Let β be the hydrogen-induced damage variable, and β be the hydrogen-induced damage weighting coefficient.

[0010] Based on the above technical solutions, preferably, the material dynamic mechanical property degradation experiment in step S3 is as follows: Pipe steel samples with different degrees of corrosion damage are prepared, and dynamic tensile tests are conducted under quasi-static, high strain rate conditions to obtain dynamic yield strength, dynamic elastic modulus, and dynamic failure plastic strain; using the uncorroded parent material as a benchmark, a degradation mapping relationship is established through regression analysis, with the function form as follows:

[0011] in, , , The strain rates of the uncorroded base material are respectively The dynamic mechanical parameters are determined experimentally. The damage amplitude degradation coefficients k1 to k3 are used to characterize the nonlinear attenuation of the corrosion damage variable on the dynamic yield strength. The damage exponential sensitivity coefficients n1 to n3 are used to characterize the exponential degradation effect of the corrosion damage variable on the dynamic elastic modulus. The dynamic mechanical properties of the uncorroded base material are described by the Johnson-Cook constitutive model.

[0012] More preferably, the determination of the degradation dynamic material properties in step S3 is specifically as follows: calculate the spatially distributed corrosion damage variable D(x, y) based on the local corrosion depth at each location in the corrosion area, substitute it into the degradation mapping relationship to obtain the material properties at each location; assign values ​​to the mesh partition of the corrosion area, and assign the same degradation material properties to the cells within the same partition.

[0013] Based on the above technical solutions, preferably, the explicit dynamic finite element model established in step S4 satisfies the following: The pipeline uses 8-node solid elements, with local mesh refinement in corrosion defect areas. The element size is 1 / 4 to 1 / 8 of the pipeline wall thickness. The soil medium is modeled using either the Drucker-Prager elastoplastic constitutive model or the MAT_SOIL_AND_FOAM model, with non-reflective boundary conditions set at the model boundaries. The blast source is applied using the measured blasting vibration velocity time history curve or the theoretical blasting load function; A pipe-soil contact algorithm is set up, and a penalty function-based contact algorithm is used to simulate the contact and collision interaction between the pipe and the soil.

[0014] More preferably, the logic of the UMAT subroutine in step S4 is as follows: read the spatial coordinates of the current integration point, call the spatial distribution data of corrosion damage variables, calculate and return the degradation dynamic material parameters at that location in real time through the degradation mapping relationship, and embed the LS-DYNA solver to complete the assignment of non-uniform material values.

[0015] Based on the above technical solutions, preferably, the remaining strength safety assessment in step S5 is as follows: Extract the peak equivalent stress σ of key parts in the corroded area max ; Calculate the dynamic residual strength coefficient RSF d =σ yd / σ max , where σ yd The corresponding dynamic yield strength is the degraded value at that location. Judgment Criteria: RSF d ≥1.0 is considered safe, RSF d A value less than 1.0 indicates insufficient safety margin; considering damage evolution variables, pipeline failure is determined when a critical value is reached.

[0016] Compared with the prior art, the present invention has the following beneficial effects: (1) Coupled material non-uniform degradation effect within the framework of blasting vibration dynamic analysis. Existing studies on corrosion of pipelines under blasting vibration generally only consider geometric thinning. This invention is the first to incorporate material degradation effects such as hydrogen-induced damage and micropore damage accumulation caused by corrosion into an explicit dynamic analysis framework, filling a technological gap in this field.

[0017] (2) A quantitative degradation mapping relationship between corrosion damage and dynamic mechanical properties was established. Through dynamic mechanical property degradation experiments, this invention established a quantitative degradation mapping function between corrosion damage variable D and dynamic yield strength, dynamic elastic modulus, and dynamic failure plastic strain, transforming the originally qualitative understanding of material softening effect into a calculable mathematical model, providing a clear theoretical basis and parameter values ​​for engineering applications.

[0018] (3) The invention achieves refined assignment of spatial non-uniform degradation field of material properties in the corrosion area. The invention uses the UMAT user-defined material subroutine of LS-DYNA to achieve refined spatial assignment of degradation dynamic material properties based on the local damage variables at each location in the corrosion area, effectively characterizing the spatial non-uniform distribution of material properties at different locations in the corrosion area due to differences in corrosion degree.

[0019] (4) This invention considers both the geometric thinning effect and the material performance degradation effect caused by corrosion, and captures the real dynamic response and damage evolution process of the pipeline under the action of explosive load through explicit dynamic analysis. This avoids the problem of insufficient conservatism caused by neglecting material degradation in traditional methods. The evaluation results are closer to the actual bearing capacity of the pipeline, and the evaluation accuracy is significantly improved. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a general flowchart of the method of the present invention; Figure 2 This is a schematic diagram showing the degradation mapping relationship between corrosion damage variables and dynamic mechanical property parameters of materials. Figure 3 A schematic diagram of an explicit dynamic finite element model of LS-DYNA (including pipes, corrosion defects, soil medium, and explosion source). Figure 4 Flowchart for UMAT implementation of non-uniform degradation field of material properties in corroded regions; Figure 5 A comparison of equivalent stress time histories for key parts of a pipeline using different assessment methods. Detailed Implementation

[0022] The specific technical solutions of the present invention are described below with reference to the embodiments.

[0023] S1: Corrosion Data Acquisition and Geometric Reconstruction Data on pipeline corrosion areas are obtained through ultrasonic waves, laser scanning, and magnetic flux leakage internal detection. High-precision corrosion geometry is reconstructed, and characteristic parameters such as corrosion depth percentage, pitting density, and corrosion area occupancy ratio are extracted to accurately characterize corrosion geometric defects.

[0024] S2: Differentiated Construction of Corrosion Damage Variables For different types of corrosion, such as uniform corrosion, localized corrosion, pitting clusters, and hydrogen-induced corrosion, corrosion damage variables are constructed to quantitatively characterize the degree of material degradation: uniform / localized corrosion adopts a depth-to-wall-thickness ratio correction model, pitting clusters adopt a two-parameter model of remaining wall-thickness ratio-area occupancy ratio, and hydrogen-induced corrosion adopts a two-variable model of geometric damage + hydrogen-induced damage.

[0025] S3: Define the degradation mapping relationship and calculate the properties of the degraded material. Through dynamic mechanical property degradation experiments at different strain rates, the quantitative mapping relationship between material corrosion damage variables, strain rate, and dynamic parameters is calibrated. The degradation dynamic yield strength, elastic modulus, and failure plastic strain at each spatial location in the corrosion zone are calculated, forming a non-uniform degradation field of the material.

[0026] S4: Establish an explicit dynamic model and conduct nonlinear transient dynamic analysis. An integrated finite element model of pipeline-corrosion-soil-blast source was established, with local mesh refinement in the corrosion area; the non-uniform degradation field of the material in the corrosion area was automatically assigned using the UMAT subroutine of LS-DYNA; blasting vibration load was applied, and nonlinear transient dynamic analysis was carried out to simulate the actual dynamic response of the pipeline.

[0027] S5: Calculate the remaining strength coefficient from the extracted results to complete the pipeline safety status assessment. Extract the equivalent stress peak and equivalent plastic strain of key corrosion sites, calculate the dynamic residual strength coefficient, accurately assess the pipeline safety status based on the judgment criteria, and output the assessment conclusions and engineering recommendations.

[0028] Example 1 This embodiment takes the safety assessment of a natural gas long-distance pipeline under the condition of blasting construction in a nearby tunnel as an example to explain in detail the specific implementation process of the present invention.

[0029] 1. Project Background and Testing Data (Evaluation of Residual Strength After Localized Corrosion Pipeline Burst Vibration) This embodiment uses a safety assessment of blasting construction near a long-distance natural gas pipeline as an example to illustrate the specific implementation steps of the present invention.

[0030] The pipeline to be evaluated is made of X70 pipeline steel, with dimensions of Φ1016mm × 14.6mm (outer diameter × wall thickness). The original dynamic yield strength of the pipeline... The original dynamic elastic modulus E0 = 210 GPa, and the burial depth is 2.5 m. Ultrasonic testing revealed an external corrosion defect on the outer wall of the pipe. The test data are as follows: maximum defect depth 6.57 mm, corresponding to a defect depth percentage d / t = 0.45; defect length L = 180 mm; defect width W = 65 mm.

[0031] The design parameters for the blasting construction plan near the tunnel are as follows: maximum single-explosive charge Q = 12 kg, and the blast source is located at a horizontal eccentricity D from the pipeline. h At a distance of 6m, the difference (vertical distance) between the burial depth of the explosion source and the burial depth of the pipeline. v =3m. The blasting vibration load is input using the time history curve of the blasting vibration velocity measured on site.

[0032] 2. Extraction of corrosion characteristic parameters and construction of damage variables Based on the detection data, the following corrosion characteristic parameters were extracted: maximum corrosion depth percentage (d / t). max =0.45; the average depth percentage within the corrosion zone is 0.32; the corrosion area coverage ratio m=0.18.

[0033] This embodiment uses the damage variable definition method for localized corrosion: D = (d / t) × α. For elliptical corrosion profiles, the morphology correction coefficient α = 1.0 is taken. The local damage variable D(x, y) = d(x, y) / t at each location within the corrosion area is constructed to obtain the spatial distribution of the damage variable.

[0034] 3. Establishment of Degenerate Mapping Relationships Prior to the evaluation, the degradation mapping relationship of X70 pipeline steel was pre-calibrated through dynamic mechanical property degradation experiments. The experimental method is as follows: Artificial pore damage specimens with different equivalent corrosion damage degrees (D=0, 0.15, 0.25, 0.35, 0.45, 0.55) were prepared and subjected to different strain rates (10... -3 s -1 10 1 s -1 10 3 s -1 Dynamic tensile tests were conducted to obtain the dynamic yield strength and dynamic elastic modulus of each specimen. Regression analysis yielded the following degradation mapping relationship:

[0035]

[0036]

[0037] in Described using the Johnson-Cook model:

[0038] For X70 pipeline steel, A=485MPa, B=260MPa, n=0.26, C=0.022. =1s -1 .

[0039] 4. Determination of dynamic material properties in corrosion zones Based on the local damage variables at various locations within the corrosion area Substituting the above degradation mapping relationship, calculate the degradation dynamic yield strength corresponding to each position. and degraded dynamic elastic modulus .

[0040] The corrosion zone was divided into four partitions using an equidistant division method. The D values ​​were divided into four sub-partitions: 0.1–0.2, 0.2–0.3, 0.3–0.4, and 0.4–0.5. The average D value within each sub-partition was used to calculate the corresponding degradation dynamic material properties (strain rate taken as 10). 3 s -1(See the table below:)

[0041] 5. Establishment of LS-DYNA explicit dynamic finite element model An integrated model of pipeline-corrosion-soil-explosion source was established using LS-DYNA.

[0042] 5.1 Pipe Model: The pipe was discretized using 8-node solid elements, and the total pipe length was set to 10 times the pipe diameter (approximately 10m) to avoid the influence of boundary effects on the corrosion zone analysis results. Local mesh refinement was applied to the corrosion defect area, with the element size in the defect area being 3mm (approximately 1 / 5 of the wall thickness).

[0043] 5.2 Soil Medium Model: The soil medium uses the MAT_SOIL_AND_FOAM material model, with dimensions of 20m × 15m × 12m. Non-reflective boundary conditions are set around the model and at the bottom.

[0044] 5.3 Blasting Source Model: Measured blasting vibration velocity time history curves were applied at the blasting source node. These time history curves were derived from field monitoring data under similar engineering conditions, with a peak particle velocity (PPV) of 8.5 cm / s, a dominant frequency (f) of 18 Hz, and a duration of approximately 0.8 s.

[0045] 5.4 Pipe-Soil Contact: The contact between the pipe and the soil is defined using *CONTACT_AUTOMATIC_SURFACE_TO_SURFACE, and a penalty function contact algorithm is employed. This algorithm has been verified as a superior method for simulating pipe-soil interaction and characterizing the dynamic response of pipes under blast loads.

[0046] 5.5 Material Property Assignment: Non-uniform assignment of degraded material properties in the corrosion zone is achieved through a user-defined material subroutine in UMAT. The UMAT subroutine reads the spatial coordinates of the current integration point, calculates and returns the degraded dynamic yield strength and degraded dynamic elastic modulus at that location based on the degradation mapping relationship determined in step 4. The implementation flow of the UMAT subroutine is as follows: Figure 4 As shown.

[0047] 6. Nonlinear transient dynamics analysis and result extraction A nonlinear transient dynamic analysis was performed on the LS-DYNA model by applying a blasting vibration load. The analysis time was set to 0.1 s, and the output time step was 0.0001 s.

[0048] Extract the equivalent stress time history of the key part (defect center) of the corrosion area to obtain the peak equivalent stress σ. max =392MPa. The effective strain rate was extracted simultaneously during the analysis. The degraded dynamic yield strength at this location under the effective strain rate is calculated based on the degradation mapping relationship:

[0049] Calculate the dynamic residual strength coefficient:

[0050] RSF d A value <1.0 indicates that the pipeline has insufficient safety margin under the current blasting conditions. It is recommended to reduce the maximum charge per blast to below 10 kg or to take pipeline protection measures.

[0051] 7. Comparison and verification of different methods To verify the accuracy and necessity of the method of the present invention, the same pipeline was evaluated using the following three methods:

[0052] The comparison results show that the traditional method, by ignoring material property degradation, significantly overestimates the load-bearing capacity (RSF) of the pipeline. d =1.43), resulting in a misjudgment of "safe". The non-uniform degradation method of this invention considers the refined non-uniform degradation of material properties in the corroded area, capturing a larger stress concentration effect, and the assessment conclusion is "unsafe", which is more consistent with the actual safety state of corroded pipelines in practical engineering. This conclusion is consistent with the findings of existing research: corrosion reduces the vibration resistance of pipelines, and the peak effective stress of the pipeline increases with increasing corrosion depth.

[0053] Example 2 (Evaluation of Remaining Strength of Pipeline Corrosion by Piping Clusters) This embodiment illustrates the application of the present invention in the evaluation of pitting cluster defects in pipelines.

[0054] 1. Extraction of feature parameters of pitting corrosion clusters The pipeline to be evaluated is made of X70 pipeline steel. Inspection revealed a pitting corrosion cluster on the pipeline surface. The characteristic parameters of the pitting corrosion cluster are as follows: Remaining wall thickness ratio R... wt =0.75, pitting area coverage ratio m=0.32, pitting density ρ=8 pits / cm².

[0055] 2. Construction of pitting cluster damage variables and determination of degradation dynamic material properties For pitting clusters, a two-parameter damage variable is defined as: D = f(R) wt Through a pre-established pitting damage calibration experiment, the empirical formula for the pitting damage variable of X70 pipeline steel is obtained as follows: D=(1 R wt )×(1+0.5·m) Substituting the parameters: D = (1 - 0.75) × (1 + 0.5 × 0.32) = 0.25 × 1.16 = 0.29.

[0056] Based on the degradation mapping relationship, calculate the degradation dynamic yield strength of the pitting cluster region: σ yd (D=0.29, =103)=520×1.11×(1 0.65×0.291.30)=577.2×0.832=480.2MPa 3. LS-DYNA Modeling and Analysis In the LS-DYNA finite element model, the pitting corrosion cluster region is geometrically modeled according to the actual pitting corrosion morphology (represented by geometric thinning of multiple pits), and degraded dynamic material properties are assigned through the UMAT subroutine. The same blasting load conditions as in Example 1 are used for analysis.

[0057] Analysis results show that the peak equivalent stress σ at key parts of the pipeline max =412MPa, dynamic residual strength coefficient RSF d =480.2 / 412=1.17, the pipeline has a safety margin under the current blasting conditions, but the margin is small.

[0058] If the traditional method (geometric modeling only, material properties not degraded) is used to analyze the same working condition, σ max =398MPa, RSF d =577.2 / 398=1.45, which overestimates the safety margin by about 24%, further verifying the necessity and accuracy of the method of the present invention.

[0059] Example 3 (Evaluation of Remaining Strength of Pipelines Including Hydrogen-Induced Damage Corrosion) This embodiment illustrates the application of the two-parameter coupled damage model of the present invention in hydrogen-containing corrosion-induced pipelines.

[0060] 1. Determination of hydrogen-induced damage parameters The pipeline under evaluation is made of X65 pipeline steel and operates in an acidic environment containing hydrogen sulfide. In addition to geometric corrosion, it also suffers from hydrogen-induced damage. Based on the corrosion environment parameters (pH=5.2, H2S partial pressure=0.08MPa) and corrosion product analysis, the hydrogen-induced damage index D is determined. H =0.18.

[0061] Meanwhile, the geometric corrosion damage variable D G =0.35.

[0062] 2. Application of the two-parameter degradation model A two-parameter degenerate mapping model is adopted: D total=D G +β·D H , where β is the weighting coefficient for hydrogen-induced damage, and β=1.2 is determined by dynamic mechanical property degradation experiments.

[0063] Calculate the effective damage variable: D total =0.35+1.2×0.18=0.566.

[0064] Based on the two-parameter degradation mapping relationship (pre-calibrated) for X65 pipeline steel:

[0065] Substitute D total =0.566, the degraded dynamic yield strength is obtained at the reference strain rate:

[0066] 3. LS-DYNA Analysis and Results The aforementioned degraded dynamic material properties were assigned to the LS-DYNA model using the UMAT subroutine, and nonlinear transient dynamic analysis was performed by applying blasting vibration loads. The peak equivalent stress σ at key locations was obtained. max =268MPa, dynamic residual strength coefficient RSF d =294 / 268=1.10.

[0067] If only geometric corrosion damage (D) is considered G =0.35 (not considering hydrogen-induced damage), σ yd =382MPa, RSF d =382 / 261=1.46. The difference between the two is 32.7%, indicating that the impact of hydrogen-induced damage on the safety status of pipeline burst vibration cannot be ignored. The two-parameter model of this invention can more realistically reflect the degradation law of pipeline mechanical properties under acidic environment. This result is consistent with the conclusion of the study on hydrogen damage prediction of pipeline steel under hydrogen environment: hydrogen damage causes significant changes in the mechanical properties of materials and must be fully considered in pipeline safety assessment.

[0068] The above description is merely a preferred embodiment of the present invention and does not limit the scope of patent protection of the present invention. Any equivalent structural or procedural modifications made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. A method for assessing the residual strength of a pipeline with corrosion defects under blasting vibration, characterized in that, Includes the following steps: S1: Obtain non-destructive testing data of the corrosion area of ​​the buried pipeline to be evaluated, reconstruct the corrosion geometry based on the testing data, and extract corrosion characteristic parameters; the corrosion characteristic parameters include at least one of corrosion depth percentage, pitting density, corrosion area occupancy ratio, and corrosion depth variation coefficient. S2: Construct material corrosion damage variables to characterize the degree of material performance degradation based on corrosion type and corresponding corrosion characteristic parameters; S3: Based on dynamic mechanical experiments, calibrate the degradation mapping relationship between material corrosion damage variables, strain rate, and dynamic performance parameters, and calculate the degradation dynamic material properties corresponding to each spatial location within the corrosion area. S4: Establish an explicit dynamic finite element model that includes the pipeline, corrosion geometry, soil medium, and blast source. Using the LS-DYNA user-defined material subroutine UMAT, assign corresponding degraded dynamic material properties to the corrosion zone elements according to their spatial location. Apply blasting vibration load to carry out nonlinear transient dynamic analysis. S5: Extract the equivalent stress peak and equivalent plastic strain of key parts in the corrosion area from the kinetic analysis results. The equivalent plastic strain is the equivalent plastic deformation accumulated by the material element during dynamic loading. Based on the above results, evaluate the remaining strength safety status of the pipeline under blasting vibration.

2. The method for evaluating the residual strength of a pipeline with corrosion defects under blasting vibration as described in claim 1, characterized in that, The non-destructive testing data mentioned in step S1 is obtained by any one of ultrasonic testing, laser three-dimensional scanning, or magnetic flux leakage internal testing; the corrosion geometry model is obtained by reverse reconstruction of point cloud data or by geometric parameterization modeling of corrosion defects, and the modeling accuracy matches the resolution of the testing data.

3. The method for evaluating the residual strength of a pipeline with corrosion defects under blasting vibration as described in claim 1, characterized in that, The corrosion damage variable mentioned in step S2 is defined differently according to the corrosion type: Uniform corrosion / localized corrosion: D=(d / t)×α, where d is the localized corrosion depth, t is the original pipe wall thickness, and α is the corrosion morphology correction coefficient, with a value of 0.8 to 1.2; Pitting corrosion clusters: D=f(R) wt ,m), where R wt The remaining wall thickness ratio is m, and the pitting corrosion area occupancy ratio is m. Hydrogen-induced damage corrosion: A two-parameter damage model was adopted, D total =D G +β·D H D G D is the geometric corrosion damage variable. H Let β be the hydrogen-induced damage variable, and β be the hydrogen-induced damage weighting coefficient.

4. The method for evaluating the residual strength of a pipeline with corrosion defects under blasting vibration as described in claim 1, characterized in that, The dynamic mechanical property degradation experiment of the material described in step S3 is as follows: Pipe steel samples with different degrees of corrosion damage are prepared, and dynamic tensile tests are conducted under quasi-static, high strain rate conditions to obtain dynamic yield strength, dynamic elastic modulus, and dynamic failure plastic strain; using the uncorroded parent material as a benchmark, a degradation mapping relationship is established through regression analysis, with the function form as follows: in, , , The strain rates of the uncorroded base material are respectively The dynamic mechanical parameters are determined experimentally. The damage amplitude degradation coefficients k1 to k3 are used to characterize the nonlinear attenuation of the corrosion damage variable on the dynamic yield strength. The damage exponential sensitivity coefficients n1 to n3 are used to characterize the exponential degradation effect of the corrosion damage variable on the dynamic elastic modulus. The dynamic mechanical properties of the uncorroded base material are described by the Johnson-Cook constitutive model.

5. The method for evaluating the residual strength of a pipeline with corrosion defects under blasting vibration as described in claim 4, characterized in that, In step S3, determining the degraded dynamic material properties specifically involves: calculating the spatially distributed corrosion damage variable D(x, y) based on the local corrosion depth at each location in the corrosion region, substituting it into the degradation mapping relationship to obtain the material properties at each location; assigning values ​​to the mesh partitions of the corrosion region, with the same degraded material properties assigned to the cells within the same partition.

6. The method for evaluating the residual strength of a pipeline with corrosion defects under blasting vibration as described in claim 1, characterized in that, In step S4, the explicit dynamic finite element model is established to satisfy the following: The pipeline uses 8-node solid elements, with local mesh refinement in corrosion defect areas. The element size is 1 / 4 to 1 / 8 of the pipeline wall thickness. The soil medium is modeled using either the Drucker-Prager elastoplastic constitutive model or the MAT_SOIL_AND_FOAM model, with non-reflective boundary conditions set at the model boundaries. The blast source is loaded using the measured blasting vibration velocity time history curve or the theoretical blasting load function. A pipe-soil contact algorithm is set up, and a penalty function-based contact algorithm is used to simulate the contact and collision interaction between the pipe and the soil.

7. The method for evaluating the residual strength of a pipeline with corrosion defects under blasting vibration as described in claim 6, characterized in that, The logic of the UMAT subroutine in step S4 is as follows: read the spatial coordinates of the current integration point, call the spatial distribution data of corrosion damage variables, calculate and return the degradation dynamic material parameters at this location in real time through the degradation mapping relationship, and embed the LS-DYNA solver to complete the assignment of non-uniform material values.

8. The method for evaluating the residual strength of a pipeline with corrosion defects under blasting vibration as described in claim 1, characterized in that, The remaining strength safety assessment in step S5 specifically involves: Extract the peak equivalent stress σ of key parts in the corroded area max ; Calculate the dynamic residual strength coefficient RSF d =σ yd / σ max , where σ yd The corresponding dynamic yield strength is the degraded value at that location. Judgment Criteria: RSF d ≥1.0 is considered safe, RSF d A value less than 1.0 indicates insufficient safety margin; considering damage evolution variables, pipeline failure is determined when a critical value is reached.

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