Local reinforcing method for large-diameter tee pipe fitting

Abstract

The present application relates to the technical field of pipe structure design and local reinforcement process, and discloses a kind of local reinforcement method of large-diameter tee pipe fittings, comprising: obtaining the stress concentration area boundary coordinate sequence of reference specification pipe fittings that has completed stress analysis, generate scale-independent area feature description vector;Calculate the geometric scaling factor of target specification and reference specification, generate the stress concentration candidate area boundary and position index of target specification pipe fittings;Using the predicted damage evolution rate and the current damage amount of target pipe fittings to calculate the predicted remaining life cycle number, generate area remaining life sequence;The reciprocal of remaining life is weighted and fused with deformation energy density priority score, generate comprehensive priority score, sort each stress concentration area of target pipe fittings according to comprehensive priority score, output reinforcement priority sequence.The present application strengthens priority sequence can reflect the time-varying risk degree of each area, provide dynamic basis for phased local reinforcement decision.

Description

Technical Field

[0001] This invention relates to the field of pipe fitting structural design and local reinforcement technology, and more specifically, it relates to a method for local reinforcement of large-diameter tee pipe fittings. Background Technology

[0002] In the serialized design and operation and maintenance of large-diameter tee fittings (such as nominal diameters of DN800, DN1600, DN2400, etc.), stress concentration occurs in the middle section of the intersection line and the junction area when the fitting is subjected to internal pressure. The stress concentration area is the main dangerous location leading to fatigue failure of the fitting, and it is necessary to reduce the stress concentration in these areas through local reinforcement measures.

[0003] According to embodiments of the present invention, a series of tee fittings with different nominal diameters have geometric similarities, and the relative positions of their stress concentration areas and the evolution of fatigue damage are scale-related. Small-sized fittings (such as DN800) have accumulated complete stress concentration area identification results and fatigue damage data due to their longer service time and sufficient monitoring data; while large-sized fittings (such as DN2400) have shorter service time and insufficient damage data, making it difficult to reliably predict the evolution trend of their strengthening priority.

[0004] Existing methods for stress concentration area identification and priority ranking perform a complete analysis process independently for each pipe fitting with a nominal diameter. However, because a scale correlation mechanism for the location characteristics of stress concentration areas and damage evolution laws among a series of pipe fittings has not been established, it is impossible to reliably predict the evolution trend of reinforcement priority for large-size pipe fittings in the absence of long-term damage monitoring data. Furthermore, the time consumption for batch analysis of a series of pipe fittings increases linearly with the number of specifications. Summary of the Invention

[0005] This invention provides a method for local reinforcement of large-diameter tee fittings, which solves the technical problems of existing independent analysis methods neglecting the geometric similarity of series fittings, insufficient long-term damage data for large-specification fittings due to short service time, and the inability to predict priority evolution, and existing static priority ranking methods failing to reflect the characteristics of fatigue damage evolution over time.

[0006] This invention provides a method for local reinforcement of large-diameter tee pipe fittings, including:

[0007] Obtain the boundary coordinate sequence of the stress concentration region of the benchmark specification pipe fitting that has completed stress analysis, and use the curve parameterization algorithm to convert the boundary coordinates into normalized parameter coordinates relative to the topological skeleton of the intersection line, and generate a scale-independent region feature description vector.

[0008] Obtain the historical stress amplitude sequence and material SN curve parameters of each stress concentration area of ​​the reference specification pipe fitting, calculate the current damage accumulation of each area using the Miner linear cumulative damage criterion, and generate a regional damage accumulation value sequence.

[0009] The damage evolution rate is obtained by calculating the ratio of the cumulative damage amount to the number of service cycles in each region. The damage evolution rate is then divided by the stress concentration factor of the corresponding region to generate the scale invariant of the damage evolution rate for each region.

[0010] Obtain the geometric parameters of the target specification pipe fitting, calculate the geometric scaling factor between the target specification and the reference specification, and use the geometric scaling factor to perform inverse normalization mapping on the region feature description vector to generate the stress concentration candidate region boundary and location index of the target specification pipe fitting.

[0011] The predicted damage evolution rate is obtained by multiplying the damage evolution rate scale invariant by the stress concentration coefficient of the corresponding region of the target pipe fitting. The predicted remaining life cycle number is calculated using the predicted damage evolution rate and the current damage amount of the target pipe fitting, and the remaining life sequence of the region is generated.

[0012] The reciprocal of the remaining lifespan is weighted and fused with the deformation energy density priority score to generate a comprehensive priority score. The stress concentration areas of the target pipe fitting are sorted according to the comprehensive priority score, and a reinforcement priority sequence is output.

[0013] Furthermore, the damage evolution rate scale invariant is calculated as follows: the current cumulative damage in the region is divided by the number of service cycles to obtain the damage evolution rate, and then the damage evolution rate is divided by the normalized stress concentration coefficient of the region. The damage evolution rate scale invariant represents the inherent rate of damage evolution after eliminating the difference in stress concentration.

[0014] Furthermore, the geometric scaling factor includes a nominal diameter scaling factor, a wall thickness scaling factor, and a main pipe length scaling factor, which are determined based on the ratio of the nominal diameter of the target specification to the nominal diameter of the reference specification, the ratio of the wall thickness, and the ratio of the main pipe length, respectively.

[0015] Furthermore, the calculation method for the predicted remaining lifetime cycles is as follows: divide the remaining damage capacity by the predicted damage evolution rate, where the remaining damage capacity is the difference between the critical damage value and the current damage amount.

[0016] Furthermore, the deformation energy density priority score is obtained by integrating the deformation energy density of each stress concentration region by volume to obtain the total deformation energy value of the region, and then normalizing the total deformation energy value to generate the deformation energy density priority score.

[0017] Furthermore, after generating the candidate boundary of the stress concentration region for the target specification pipe fitting, the process also includes: obtaining the finite element stress analysis results of the target specification pipe fitting, fine-tuning the boundary using a local gradient search algorithm in the neighborhood of the candidate region boundary, and generating an accurate stress concentration region boundary coordinate sequence.

[0018] Furthermore, it also includes: calculating the ratio of the mean offset before and after boundary fine-tuning to the maximum allowable offset threshold, using this ratio to calculate the confidence index, and outputting the confidence index along with the enhanced priority sequence.

[0019] Furthermore, the intersection line topological skeleton is the central skeleton of the spatial curve formed by the intersection of the main pipe and the branch pipe of the tee fitting, and the normalized parameter coordinates represent the boundary point position as a dimensionless parameter relative to the intersection line skeleton.

[0020] Furthermore, in the weighted fusion of the comprehensive priority scores, the sum of the weight coefficient of the reciprocal of the remaining lifetime and the weight coefficient of the deformation energy density priority score is 1.

[0021] This invention provides a local reinforcement system for large-diameter tee pipe fittings, comprising:

[0022] The regional feature normalization module is used to obtain the boundary coordinate sequence of the stress concentration area of ​​the reference specification pipe fitting, and to generate a scale-independent regional feature description vector using the curve parameterization algorithm.

[0023] The damage accumulation calculation module is used to obtain historical stress amplitude sequences and material parameters, and to calculate the regional damage accumulation value sequence using the Miner linear cumulative damage criterion.

[0024] The scale invariant generation module is used to calculate the damage evolution rate and divide it by the stress concentration factor to generate the damage evolution rate scale invariant.

[0025] The scale transformation mapping module is used to perform inverse normalization mapping on the region feature description vector according to the geometric scaling factor to generate the candidate boundary of the stress concentration region of the target pipe fitting.

[0026] The remaining life prediction module is used to calculate the predicted number of remaining life cycles based on the damage evolution rate scale invariant and the stress concentration factor of the target pipe fitting.

[0027] The priority fusion output module is used to perform weighted fusion and sorting of the reciprocal of the remaining lifetime and the priority score of the deformation energy density, and output an enhanced priority sequence.

[0028] The beneficial effects of this invention are as follows:

[0029] According to an embodiment of the present invention, this scheme uses normalized parameter coordinate representation and scale transformation to convert the boundary coordinates of the stress concentration region into a dimensionless parameter representation relative to the topological skeleton of the intersection line. This allows the regional location features to be mapped between series of pipe fittings with different nominal diameters through a geometric scaling factor matrix, overcoming the problem that existing independent analysis methods ignore the geometric similarity of series of pipe fittings, thereby improving the efficiency of batch analysis of series of pipe fittings.

[0030] Furthermore, by adopting scale invariant modeling of damage evolution rate and cross-specification conversion, and by eliminating the influence of scale differences by dividing the damage evolution rate by the stress concentration factor, a damage evolution rate characterization that can be directly transferred between series of pipe fittings was established. This overcomes the factor that large-specification pipe fittings cannot predict priority evolution due to insufficient long-term damage data caused by short service time. Thus, the damage monitoring experience of small-specification pipe fittings can be used to deduce the reinforcement priority of large-specification pipe fittings.

[0031] By employing Miner cumulative damage quantification and remaining lifetime weighting, and integrating the reciprocal of the remaining lifetime with the deformation energy density score to generate a comprehensive priority, this method overcomes the limitation of existing static priority ranking methods in failing to reflect the characteristics of fatigue damage evolution over time. This enables the strengthening priority ranking to reflect the time-varying risk level of each region, providing a dynamic basis for phased local strengthening decisions. Attached Figure Description

[0032] Figure 1 This is a flowchart of a method for local reinforcement of a large-diameter tee fitting according to the present invention;

[0033] Figure 2 This is a curve showing the evolution of the cumulative damage amount of the present invention over the service life;

[0034] Figure 3 This is a bar chart comparing the stress concentration factors of pipe fittings of different specifications according to the present invention;

[0035] Figure 4 This invention provides a comprehensive priority assessment multidimensional heat map.

[0036] Figure 5 This is a biaxial comparison chart of the remaining lifetime and damage evolution rate of the present invention;

[0037] Figure 6 This is a scatter plot for verifying the cross-scale mapping boundary accuracy of the present invention. Detailed Implementation

[0038] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and implement the subject matter described herein, and changes may be made to the function and arrangement of the elements discussed without departing from the scope of this specification. Various processes or components may be omitted, substituted, or added as needed in the examples. Furthermore, some features described in the examples may be combined in other examples.

[0039] At least one embodiment of the present invention discloses a method for local reinforcement of large-diameter tee fittings, such as... Figure 1 As shown, it includes the following steps:

[0040] Step 1: Obtain the boundary coordinate sequence of the stress concentration area of ​​the reference specification pipe fitting, and perform normalization transformation using the curve parameterization algorithm to generate a scale-independent region feature description vector.

[0041] Obtain the boundary coordinate sequence of the stress concentration region for a standard pipe fitting (e.g., DN800) that has undergone finite element stress analysis. It should be understood that the boundary coordinate sequence of the stress concentration region is a set of discrete point coordinates in three-dimensional space, describing the distribution boundary of the stress concentration region on the pipe fitting surface. Use a curve parameterization algorithm to convert the boundary coordinates into normalized parametric coordinates relative to the intersection line topological skeleton, generating a scale-independent region feature description vector.

[0042] It should be noted that the aforementioned intersection line topological skeleton refers to the central skeleton of the spatial curve formed by the intersection of the main pipe and branch pipe of the tee fitting. The normalized parametric coordinates represent the boundary point positions as dimensionless parameters relative to the intersection line skeleton, making the normalized parametric coordinates independent of the actual dimensions of the fitting.

[0043] Furthermore, the specific implementation of the curve parameterization algorithm is as follows: First, extract the discrete skeleton point sequence of the intersection line from the geometric model of the tee fitting; then, parameterize the arc length of the skeleton point sequence and calculate the cumulative arc length of each skeleton point. Divide by the total arc length Obtain the normalized arc length parameter ,in Indicates the index of the skeleton point. For the first The cumulative arc length of each skeleton point For the first The normalized arc length parameter corresponds to each skeleton point; then for each coordinate point on the boundary of the stress concentration region... Calculate the shortest distance to the skeleton point sequence and determine the normalized arc length parameter corresponding to the nearest skeleton point. and radial offset distance ,in Indicates the index of the boundary point. For the first A boundary point, For the first The normalized arc length parameter corresponding to each boundary point For the first The radial offset distance of each boundary point represents the boundary point of the stress concentration region as follows: The normalized parameter coordinates are in the form of a vector; finally, the sequence of normalized parameter coordinates of all boundary points is organized into a region feature description vector.

[0044] In the pipeline system of a petrochemical enterprise, a DN800 reference pipe fitting has been in service for 720 days. Finite element stress analysis identified three main stress concentration areas: region A in the middle section of the intersection line, region B at the junction, and region C at the root of the branch pipe. The geometric parameters of the reference pipe fitting are: nominal diameter 800mm, wall thickness 12mm, main pipe length 2400mm, and total arc length of the intersection line. After extracting the boundary coordinate sequences of each region, representative boundary points are selected for curve parameterization in region A, where the three-dimensional coordinates of a certain boundary point are... The cumulative arc length of the skeleton point corresponding to the shortest distance from this point to the skeleton is calculated to be... The radial offset distance is Converted to normalized parametric coordinates After completing the parameterization transformation of all region boundary points, a scale-independent region feature description vector is generated.

[0045] Table 1. Normalized parameter characteristics of stress concentration region for DN800 reference pipe fittings:

[0046]

[0047] Step 2: Obtain the historical stress amplitude sequence and material parameters of each stress concentration area of ​​the reference specification pipe fitting, and use the Miner linear cumulative damage criterion to calculate and generate the regional damage accumulation sequence.

[0048] Obtain the historical stress amplitude sequence and material SN curve parameters for each stress concentration region of the reference specification pipe fitting. Calculate the current cumulative damage in each region using the Miner linear cumulative damage criterion. :

[0049]

[0050] in, An index representing the stress amplitude level. Indicates the first The actual number of cycles under the stress amplitude. Indicates the first Fatigue life of materials under stress amplitude of level 1 Indicates the stress amplitude level. When Reaching the critical value of 1 indicates fatigue failure.

[0051] Furthermore, the method for obtaining the material SN curve parameters is as follows: Based on the pipe fitting material grade, query the material standard database or test report to obtain the material SN curve equation parameters. A common form is... ,in The fatigue life is the number of cycles. The stress amplitude, and Let be a material constant; for a given , Level stress amplitude Substituting this into the SN curve equation, the corresponding fatigue life can be calculated. .

[0052] Furthermore, for common pipe fitting materials, the material constant... and The typical value range is as follows: for carbon steel and low alloy steel materials (such as 16Mn, Q345B), the parameter... The range of values ​​is to (unit: ), slope parameter The value range is 3 to 5; for stainless steel materials (such as 304, 316L), the parameter... The range of values ​​is to (unit: ), slope parameter The value ranges from 3.5 to 6; the specific value needs to be determined based on material standards or fatigue test data.

[0053] Generate a sequence of cumulative damage amounts for each region.

[0054] The DN800 pipe fitting is made of Q345B low-alloy steel. The SN curve parameters were obtained by consulting a material database. (unit: ), The pipe fittings are subjected to daily cyclic pressure fluctuations, with a single load cycle of 24 hours, and a service life corresponding to 720 days of operation. Historical stress amplitude sequences for each stress concentration area were obtained through an online monitoring system, and the stress amplitudes were divided into four levels. For area A, the first level stress amplitude... Loop count Next, substitute the values ​​into the SN curve equation to calculate fatigue life. This level of damage contribution was obtained. The damage contribution of all stress amplitude levels is calculated using this method, and the cumulative damage in region A is obtained by summing them up. .

[0055] Table 2 Calculation of cumulative damage in each stress concentration area of ​​DN800 standard pipe fitting:

[0056]

[0057] Figure 2 This demonstrates the evolution of damage accumulation over the service life of three stress concentration areas (intersection section A, junction B, and branch root C) of a DN800 reference pipe fitting.

[0058] Step 3: Calculate the ratio of cumulative damage to the number of service cycles in each region, normalize it using the stress concentration factor, and generate the scale invariant of damage evolution rate for each region.

[0059] Calculate the cumulative damage and service cycle number for each region. The ratio of the two values ​​yields the damage evolution rate. Dividing the damage evolution rate by the normalized stress concentration factor of the corresponding region gives the damage evolution rate. Generate scale invariants of damage evolution rate for each region. :

[0060]

[0061] in, This represents the current cumulative damage in the area. This refers to the number of service cycles. This represents the stress concentration factor in this region. It should be understood that the damage evolution rate is a scale invariant. It characterizes the intrinsic rate of damage evolution after eliminating differences in stress concentration. The scale invariant of the damage evolution rate is scale independent and can be directly transferred between series of pipe fittings with different nominal diameters.

[0062] Furthermore, the number of service cycles The definition method is as follows: determine the periodic characteristics of the load cycle based on the actual working conditions of the pipe fitting, and calculate the cumulative operating time of the pipe fitting from the start of its use. (Unit: hours or days) Divide by the duration of a single load cycle. (Unit: hours or days) to obtain the number of service cycles. For example, for pipe fittings subjected to daily cyclic pressure fluctuations, with a single load cycle of 24 hours, if the pipe fitting has been in operation for 720 days, then the service life is... For pipe fittings subjected to start-stop cycles, a single load cycle period is the start-stop interval time, and the service cycle number is the cumulative number of start-stop cycles.

[0063] Furthermore, the stress concentration factor The maximum principal stress peak value of each stress concentration region is obtained by extracting it from the finite element stress analysis results generated in step 1. Simultaneously extract the nominal stress of the main pipe far from the stress concentration area. The stress concentration factor is obtained by calculating the ratio of the two. .

[0064] Extract the nominal stress of the main pipe of the DN800 reference pipe fitting from the finite element analysis results. The peak values ​​of the maximum principal stresses in each stress concentration region are as follows: Region A Region B Region C The calculated stress concentration factors are as follows: , , Combined with the number of service cycles Based on the damage accumulation sequence, calculate the scale invariant of damage evolution rate for each region. For region A: For region B: For region C: .

[0065] Table 3 Calculation of scale invariants for damage evolution rate of DN800 reference pipe fittings:

[0066]

[0067] Step 4: Obtain the geometric parameters of the target specification pipe fitting, perform inverse normalization mapping using the scale transformation algorithm, and generate the initial boundary and corresponding position index of the stress concentration candidate region of the target specification pipe fitting.

[0068] Obtain the geometric parameters of the target specification pipe fitting (e.g., DN2400), including nominal diameter, wall thickness, and main pipe length. Calculate the geometric scaling factor matrix between the target specification and the reference specification. :

[0069]

[0070] in, This is the nominal diameter scaling factor. This is the wall thickness scaling factor. This is the scaling factor for the supervisor's length.

[0071] Furthermore, the geometric scaling factor is calculated as follows: nominal diameter scaling factor ,in The nominal diameter of the target pipe fitting, The nominal diameter of the reference pipe fitting; wall thickness scaling factor. ,in The wall thickness of the target pipe fitting, The wall thickness of the reference fitting; scaling factor for the main pipe length. ,in The main pipe length of the target fitting, The main pipe length is the reference pipe fitting.

[0072] The region feature description vector generated in step 1 is inversely normalized and mapped using the scaling transformation parameters to generate the initial boundary and corresponding position index of the stress concentration candidate region for the target specification pipe fitting.

[0073] Furthermore, the specific operation of the inverse normalization mapping is as follows: first, extract the sequence of intersection line skeleton points of the target pipe fitting and calculate the total arc length. Then, for each normalized parameter coordinate in the feature description vector of the reference fitting area... Calculate its corresponding position on the target pipe frame, specifically: based on the normalized arc length parameter. Calculate the actual arc length position on the target skeleton Locate the skeleton point corresponding to the arc length position and its local coordinate system in the skeleton point sequence, and offset the radial distance. Multiply by the nominal diameter scaling factor Obtain the scaled radial offset distance Offset along the normal direction of the skeleton point Obtain the three-dimensional boundary coordinates of the target pipe fitting. Finally, all the mapped boundary coordinate point sequences are organized into the initial boundary of the candidate stress concentration region for the target pipe fitting.

[0074] For the target pipe fitting of DN2400, its geometric parameters are: nominal diameter 2400mm, wall thickness 35mm, main pipe length 7200mm, and total arc length of the intersection line. Calculate the geometric scaling factor matrix: nominal diameter scaling factor. Wall thickness scaling factor Supervisor length scaling factor The regional feature description vector of the reference pipe fitting is inversely normalized using a scaling transformation algorithm. For region A, its normalized arc length parameter... Calculate the actual arc length position on the target skeleton. Average radial offset distance of the reference pipe fitting Radial offset distance after scaling Candidate regions for stress concentration in the target pipe fitting are obtained by offsetting along the normal direction of the skeleton. The initial boundaries. Perform the same mapping process on regions B and C.

[0075] Table 4. Mapping results of candidate stress concentration regions for DN2400 target pipe fittings:

[0076]

[0077] Step 5: Multiply the damage evolution rate scale invariant by the stress concentration factor of the corresponding region of the target pipe fitting to convert it into the predicted damage evolution rate of each region of the target pipe fitting. Combine the current damage amount of the target pipe fitting to calculate the predicted remaining life cycle number and generate the regional remaining life sequence.

[0078] The damage evolution rate scale invariant generated in step 3 Multiply by the stress concentration factor of the corresponding area of ​​the target pipe fitting This is converted into the predicted damage evolution rate of each region of the target pipe fitting. :

[0079]

[0080] Obtain the current damage amount of each area of ​​the target pipe fitting. The predicted remaining lifespan is calculated using the predicted damage evolution rate. :

[0081]

[0082] Among them, molecules Indicates the remaining damage capacity.

[0083] Furthermore, the current damage amount in each region of the target pipe fitting. The damage is obtained as follows: If historical stress amplitude data of the target pipe fitting is available, the current damage amount is calculated from the actual monitoring data using the Miner linear cumulative damage criterion in step 2. If the target pipe fitting has not yet been put into service or monitoring data is insufficient, the current damage level will be... At this point, the remaining lifespan is predicted to be [number of lifespan cycles]. It equals the predicted total lifespan cycles.

[0084] Generate the remaining lifetime sequence for each region.

[0085] The DN2400 target pipe fitting has been in service for 180 days. Preliminary monitoring has yielded the stress concentration factors for each candidate area. [The text then abruptly shifts to a different topic:] For the candidate areas... Finite element analysis was performed to verify the results and extract the peak value of the maximum principal stress. nominal stress Calculate the stress concentration factor The damage evolution rate of the reference pipe fitting region A is scaled invariant. Multiply by the stress concentration factor of the target pipe fitting to obtain the predicted damage evolution rate. Short-term monitoring data for the target pipe fitting is available; the current damage level is calculated using the Miner criterion. Calculate the predicted remaining lifespan number of cycles. One cycle (approximately 4.9 years). For candidate regions and Perform the same calculation process.

[0086] Table 5. Calculation of predicted remaining life for each candidate area of ​​the DN2400 target pipe fitting:

[0087]

[0088] Figure 3 Compare the stress concentration factors in the corresponding areas of the DN800 reference pipe fitting and the DN2400 target pipe fitting.

[0089] Figure 5 The design employs a dual Y-axis approach. The left Y-axis (bar chart) represents the predicted remaining life cycles for each candidate region of the DN2400 target pipe fitting, while the right Y-axis (line chart) represents the predicted damage evolution rate.

[0090] Step 6: Based on historical damage data, use an extrapolation algorithm to predict the rate of damage increment in future cycles, and weight and fuse the reciprocal of the remaining lifetime with the deformation energy density priority score to generate a comprehensive priority score for the accumulated fused damage.

[0091] Based on historical damage growth data, a linear extrapolation algorithm is used to predict the rate of damage increment in each region within future cycles.

[0092] Furthermore, the specific implementation of the linear extrapolation algorithm is as follows: obtain the historical damage evolution rate sequence of each stress concentration region. ,in They represent the 1st, 2nd, ..., The damage evolution rate at each monitoring time point is used to obtain the damage growth rate trend line by performing linear regression fitting on the historical damage evolution rate sequence. ,in and For regression coefficients; the current time... Substituting into the trend line equation, the predicted rate of damage increment in future cycles is calculated. The predicted damage increment rate is used to correct the predicted damage evolution rate calculated in step 5, thereby improving the accuracy of remaining lifetime prediction.

[0093] Furthermore, the linear regression coefficients and The calculation method is as follows: using the least squares method on historical data points Perform fitting and calculate regression coefficients and ,in Index indicating the monitoring time. The number of historical data points. For the first The number of service cycles corresponding to each monitoring moment. For the first Damage evolution rate at each monitoring time point.

[0094] Get the reciprocal of the remaining lifespan for each region The reciprocal lifetime series for all regions are normalized to mean based on range to eliminate the influence of dimensions and generate normalized lifetime risk scores. .

[0095] Furthermore, the normalized remaining lifetime risk score The calculation formula is: for the th For each stress concentration region, calculate the reciprocal of its remaining life. Calculate the maximum value of the reciprocal of the remaining lifespan for all regions. and minimum value ,in Index indicating stress concentration region These represent the reciprocals of the remaining lifetime of the 1st, 2nd, ..., Mth stress concentration regions, respectively. The total number of stress concentration areas is then used to calculate the normalized remaining life risk score. The normalized remaining life risk score ranges as follows: A higher value indicates a shorter remaining lifespan and higher risk in that area.

[0096] Normalized remaining life risk score Priority score of deformation energy density A weighted fusion is performed to generate a comprehensive priority score. :

[0097]

[0098] in, and Let be the weighting coefficient, satisfying Regions with shorter remaining lifespans receive higher priority scores.

[0099] It should be noted that the above deformation energy density priority scores It is a score obtained by normalizing the volume integral of the deformation energy density in each stress concentration region, reflecting the potential destructive energy accumulated in the region.

[0100] Furthermore, the weighting coefficients and Determine based on the actual application scenario: When the focus is on preventing the risk of near-term fatigue failure, set... To increase the weight of the remaining life factor; when focusing on determining reinforcement locations based on static stress distribution, set... To increase the weight of the deformation energy density factor; when considering the dynamic damage evolution and static stress distribution in a balanced manner, set... .

[0101] Furthermore, the deformation energy density priority score The calculation method is as follows: extract the strain energy density value of each element in each stress concentration region from the finite element analysis results. With unit volume Calculate the total deformation energy of the region ,in Indicates the index of the cell. For the first The deformation energy density value of each unit. For the first Volume of each unit The total number of elements within the region is used as the unit, and then the total strain energy sequence of all regions is normalized to generate strain energy density priority scores. .

[0102] The DN2400 target pipe fitting has a relatively short service life (180 days), and the number of historical monitoring data points is limited, insufficient to support reliable extrapolation analysis. Therefore, the remaining life sequence generated in step 5 is used directly for subsequent calculations. The reciprocal of the remaining life is calculated for each candidate region: , , Statistical maximum value and minimum value For candidate regions Calculate the normalized remaining life risk score Similarly, the calculation yields... , Extracting the total deformation energy of each candidate region from the finite element analysis results: candidate region of Candidate regions of Candidate regions of The total deformation energy sequence is normalized, and the normalization coefficients are calculated. For candidate regions Calculate the priority score for deformation energy density Similarly, the calculation yields... , This application scenario focuses on preventing the risk of near-term fatigue failure, and sets weighting coefficients accordingly. , For candidate regions Calculate the overall priority score For candidate regions calculate For candidate regions calculate .

[0103] Table 6. Calculation of the comprehensive priority score for each candidate area of ​​the DN2400 target pipe fitting:

[0104]

[0105] Figure 4 The score distribution of the three candidate areas of the DN2400 target pipe fitting on different evaluation dimensions is shown in the form of a heat map.

[0106] Step 7: Sort the stress concentration areas of the target pipe fitting in descending order according to the comprehensive priority score, calculate the statistical value of the boundary fine-tuning offset and the scale transformation prediction deviation as the confidence index, and output the cross-scale extrapolation strengthening priority sequence and confidence assessment.

[0107] Based on overall priority score The stress concentration regions of the target pipe fitting are sorted in descending order. The statistical value of the offset between the predicted boundary and the actual boundary after scale transformation is used as a confidence index. :

[0108]

[0109] in, The mean of the boundary offsets. This represents the maximum allowed offset threshold. Confidence level. The closer the value is to 1, the higher the reliability of the cross-scale extrapolation results.

[0110] Furthermore, the maximum allowed offset threshold Determined based on the characteristic dimensions of the stress concentration region: the average characteristic length of the stress concentration region is taken. to As the maximum offset threshold Where the feature length is the maximum side length of the region boundary envelope box; when the confidence level When the cross-scale extrapolation results are deemed reliable, the output enhancement priority sequence can be directly adopted; when the confidence level is... When doing so, it is recommended to verify the results by combining the complete finite element analysis of the target pipe fitting.

[0111] Output the enhanced priority sequence and confidence assessment for cross-scale extrapolation.

[0112] The candidate areas for the DN2400 target pipe fitting are sorted in descending order according to their comprehensive priority scores, resulting in the following priority sequence: Candidate Areas (Intersection), Candidate Area (Middle section of the intersection line), candidate area (Branch root). The accuracy of the scale transformation prediction boundary is evaluated. After fine-tuning the initial boundary of the candidate region using a local gradient search algorithm, the offset of the boundary points before and after fine-tuning is calculated: Candidate region average offset Candidate region average offset Candidate region average offset Mean of boundary offset of the three regions The average feature length of the candidate region is 920 mm. As the maximum offset threshold Calculate the confidence index Confidence level The reliability of the cross-scale extrapolation results was determined.

[0113] Table 7. Priority sequence and confidence assessment for cross-scale simulation of DN2400 target pipe fittings:

[0114]

[0115] Figure 6 The results of the boundary prediction accuracy verification for cross-scale mapping of DN2400 target pipe fittings are presented.

[0116] In this embodiment, to further improve the accuracy of the stress concentration region boundary, the following steps are added based on step 4: obtaining the finite element stress analysis results of the target specification pipe fitting, and using a local gradient search algorithm to fine-tune the boundary within the neighborhood of the initial boundary of the candidate region, generating a precise stress concentration region boundary coordinate sequence. This boundary fine-tuning step improves the accuracy of boundary positioning by analyzing the stress gradient distribution within the neighborhood of the candidate region and locally correcting the initial boundary obtained by scale transformation.

[0117] Furthermore, the specific implementation of the local gradient search algorithm is as follows: for each coordinate point on the initial boundary of the candidate region... Within its neighborhood (the neighborhood radius is taken as the initial boundary feature size), to Extract the stress values ​​of the finite element mesh nodes and calculate the stress gradient vector field in that neighborhood. Search along the stress gradient direction to find the stress gradient magnitude. The location where a local maximum is reached is taken as the precise boundary point, and the search step size is set to the average size of the mesh cells; when the rate of change of the stress gradient magnitude is lower than a set threshold (e.g., the rate of change is less than 1 / 3 for three consecutive steps), the search is initiated. The search terminates when the current position is determined as the fine-tuned boundary point. After fine-tuning all initial boundary points, the fine-tuned boundary point sequence is organized into a precise stress concentration region boundary coordinate sequence.

[0118] According to the embodiments of this implementation, the scheme uses normalized parameter coordinate representation and scale transformation to convert the boundary coordinates of the stress concentration region into a dimensionless parameter representation relative to the topological skeleton of the intersection line. This allows the regional location features to be mapped between series of pipe fittings with different nominal diameters through a geometric scaling factor matrix, overcoming the problem that existing independent analysis methods ignore the geometric similarity of series of pipe fittings, thereby improving the efficiency of batch analysis of series of pipe fittings.

[0119] Furthermore, by adopting scale invariant modeling of damage evolution rate and cross-specification conversion, and by eliminating the influence of scale differences by dividing the damage evolution rate by the stress concentration factor, a damage evolution rate characterization that can be directly transferred between series of pipe fittings was established. This overcomes the factor that large-specification pipe fittings cannot predict priority evolution due to insufficient long-term damage data caused by short service time. Thus, the damage monitoring experience of small-specification pipe fittings can be used to deduce the reinforcement priority of large-specification pipe fittings.

[0120] By employing Miner cumulative damage quantification and remaining lifetime weighting, and integrating the reciprocal of the remaining lifetime with the deformation energy density score to generate a comprehensive priority, this method overcomes the limitation of existing static priority ranking methods in failing to reflect the characteristics of fatigue damage evolution over time. This enables the strengthening priority ranking to reflect the time-varying risk level of each region, providing a dynamic basis for phased local strengthening decisions.

[0121] The embodiments of the present invention have been described above. However, the embodiments are not limited to the specific implementation methods described above. The specific implementation methods described above are merely illustrative and not restrictive. Those skilled in the art can make more equivalent embodiments under the guidance of the present embodiments, and all of them are within the protection scope of the present embodiments.

Claims

1. A method for local reinforcement of large-diameter tee pipe fittings, characterized in that, Includes the following steps: Obtain the boundary coordinate sequence of the stress concentration region of the benchmark specification pipe fitting that has completed stress analysis, and use the curve parameterization algorithm to convert the boundary coordinates into normalized parameter coordinates relative to the topological skeleton of the intersection line, and generate a scale-independent region feature description vector. Obtain the historical stress amplitude sequence and material SN curve parameters of each stress concentration area of ​​the reference specification pipe fitting, calculate the current damage accumulation of each area using the Miner linear cumulative damage criterion, and generate a regional damage accumulation value sequence. The damage evolution rate is obtained by calculating the ratio of the cumulative damage amount to the number of service cycles in each region. The damage evolution rate is then divided by the stress concentration factor of the corresponding region to generate the scale invariant of the damage evolution rate for each region. Obtain the geometric parameters of the target specification pipe fitting, calculate the geometric scaling factor between the target specification and the reference specification, and use the geometric scaling factor to perform inverse normalization mapping on the region feature description vector to generate the stress concentration candidate region boundary and location index of the target specification pipe fitting. The predicted damage evolution rate is obtained by multiplying the damage evolution rate scale invariant by the stress concentration coefficient of the corresponding region of the target pipe fitting. The predicted remaining life cycle number is calculated using the predicted damage evolution rate and the current damage amount of the target pipe fitting, and the remaining life sequence of the region is generated. The reciprocal of the remaining lifespan is weighted and fused with the deformation energy density priority score to generate a comprehensive priority score. The stress concentration areas of the target pipe fitting are sorted according to the comprehensive priority score, and a reinforcement priority sequence is output.

2. The method for local reinforcement of large-diameter tee fittings according to claim 1, characterized in that, The damage evolution rate scale invariant is calculated as follows: the current cumulative damage in the region is divided by the number of service cycles to obtain the damage evolution rate, and then the damage evolution rate is divided by the normalized stress concentration coefficient of the region. The damage evolution rate scale invariant represents the inherent rate of damage evolution after eliminating the difference in stress concentration.

3. The method for local reinforcement of large-diameter tee fittings according to claim 1, characterized in that, The geometric scaling factors include nominal diameter scaling factor, wall thickness scaling factor, and main pipe length scaling factor, which are determined based on the ratio of nominal diameter to target specification, wall thickness to reference specification, and main pipe length to reference specification, respectively.

4. The method for local reinforcement of large-diameter tee fittings according to claim 1, characterized in that, The method for calculating the predicted remaining lifetime cycles is as follows: divide the remaining damage capacity by the predicted damage evolution rate, where the remaining damage capacity is the difference between the critical damage value and the current damage amount.

5. The method for local reinforcement of large-diameter tee fittings according to claim 1, characterized in that, The deformation energy density priority score is obtained by integrating the deformation energy density of each stress concentration region by volume to obtain the total deformation energy value of the region, and then normalizing the total deformation energy value to generate the deformation energy density priority score.

6. The method for local reinforcement of large-diameter tee fittings according to claim 1, characterized in that, After generating the candidate boundary of the stress concentration region for the target specification pipe fitting, the process also includes: obtaining the finite element stress analysis results of the target specification pipe fitting, fine-tuning the boundary using a local gradient search algorithm in the neighborhood of the candidate region boundary, and generating an accurate stress concentration region boundary coordinate sequence.

7. The method for local reinforcement of large-diameter tee fittings according to claim 6, characterized in that, Also includes: Calculate the ratio of the mean offset before and after boundary fine-tuning to the maximum allowable offset threshold, use this ratio to calculate the confidence index, and output the confidence index along with the reinforcement priority sequence.

8. The method for local reinforcement of large-diameter tee fittings according to claim 1, characterized in that, The intersection line topology skeleton is the central skeleton of the spatial curve formed by the intersection of the main pipe and the branch pipe of the tee fitting. The normalized parameter coordinates represent the boundary point position as a dimensionless parameter relative to the intersection line skeleton.

9. The method for local reinforcement of large-diameter tee fittings according to claim 1, characterized in that, In the weighted fusion of the comprehensive priority scores, the sum of the weight coefficient of the reciprocal of the remaining lifetime and the weight coefficient of the deformation energy density priority score is 1.

10. A local reinforcement system for large-diameter tee fittings, used to perform the local reinforcement method for large-diameter tee fittings as described in any one of claims 1-9, characterized in that, include: The regional feature normalization module is used to obtain the boundary coordinate sequence of the stress concentration area of ​​the reference specification pipe fitting, and to generate a scale-independent regional feature description vector using the curve parameterization algorithm. The damage accumulation calculation module is used to obtain historical stress amplitude sequences and material parameters, and to calculate the regional damage accumulation value sequence using the Miner linear cumulative damage criterion. The scale invariant generation module is used to calculate the damage evolution rate and divide it by the stress concentration factor to generate the damage evolution rate scale invariant. The scale transformation mapping module is used to perform inverse normalization mapping on the region feature description vector according to the geometric scaling factor to generate the candidate boundary of the stress concentration region of the target pipe fitting. The remaining life prediction module is used to calculate the predicted number of remaining life cycles based on the damage evolution rate scale invariant and the stress concentration factor of the target pipe fitting. The priority fusion output module is used to perform weighted fusion and sorting of the reciprocal of the remaining lifetime and the priority score of the deformation energy density, and output an enhanced priority sequence.

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