Remaining life assessment system and method

Abstract

To provide a life evaluation system and a method for evaluating a life that can provide a rapid maintenance plan by evaluating the soundness of a defect detected in an examination in a short time.SOLUTION: The method for evaluating the life of a structure includes: an advance preparation step of creating an analysis model for the sound state and the design state of an evaluation target part of a structure in advance; a site measuring step of performing an examination and measuring the shape of the evaluation target part; a reflection step of reflecting the result of measuring the size of the evaluation target part on the analysis model; and an evaluation step of evaluating the life of a fatigue crack.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a system and method for assessing the remaining life of pipes used in, for example, a power plant, particularly those parts where aging deterioration or fatigue damage is expected. [Background technology]

[0002] In power plants, for example, where aging is progressing, improving the accuracy of health assessment techniques for aging equipment is important for improving safety and extending the plant life.

[0003] In conventional integrity assessment technology, as shown in Non-Patent Document 1, if a defect is detected by non-destructive testing during a regular inspection, a crack propagation assessment is performed taking into account the aging deterioration phenomena expected from the operating conditions of the equipment, and it is confirmed that the equipment's integrity can be maintained until the next inspection.

[0004] Generally, crack propagation evaluation is performed by determining stress intensity factors using simplified equations or the finite element method. As shown in Patent Documents 1 and 2, crack propagation evaluation using the finite element method can reflect complex geometric shapes and stress distributions, but it requires the creation of a complex analytical model, and if crack propagation is involved, the analytical model must be recreated and reanalyzed, resulting in extremely high calculation costs. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-324497 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-4599 [Non-patent literature]

[0006] [Non-Patent Document 1] Japan Nuclear Technology Association, "Guidelines for Inspection and Evaluation of Reactor Internal Structures, etc." Summary of the Invention [Problem to be solved by the invention]

[0007] As a result, it was not possible to quickly carry out life and remaining life assessments that reflected the defect shapes obtained through non-destructive testing, and the time required to formulate maintenance plans often led to extended shutdown periods for power plants.

[0008] Furthermore, because there is no means to quickly and efficiently incorporate the defect shapes obtained through non-destructive testing into an analysis model and provide crack propagation evaluation results in a short period of time, conservative life and remaining life assessments are carried out with a large safety factor. As a result, the remaining life of power plant equipment is estimated to be short, leading to a decrease in the efficiency of the entire power plant.

[0009] In view of the above, an object of the present invention is to provide a remaining life assessment system and method that can provide a prompt maintenance plan by quickly performing a soundness assessment of defects detected during inspection. [Means for solving the problem]

[0010] Based on the above, the present invention is a "remaining life assessment system for assessing the remaining life of a structure, which comprises a preparatory step of creating an analytical model corresponding to the soundness and design state of the part of the structure to be assessed in advance, and an on-site measurement step of inspecting and measuring the shape of the part to be assessed, Obtained through on-site measurement process a reflection step of reflecting the dimensional measurement results of the evaluation target portion in the analysis model; By finite element method There is an evaluation process for evaluating the remaining life of fatigue cracks. In the reflection process, the nodes of the analysis model prepared in advance are moved only in the radial direction of the pipe to reflect the shape (curved surface, point cloud) created from the results of measuring the deteriorated shape (defects, thinning) of the evaluation target using UT. The remaining life assessment system is characterized by:

[0011] Furthermore, in the present invention, "a remaining life evaluation method for evaluating the remaining life of a structure, which comprises the steps of: creating an analytical model corresponding to the sound state and design state of the evaluation target part of the structure in advance; inspecting the part; measuring the shape of the evaluation target part; and reflecting the dimensional measurement results of the evaluation target part in the analytical model; By finite element methodRemaining life assessment of fatigue cracks In this process, the nodes of the analysis model prepared in advance are moved only in the radial direction of the pipe to reflect the shape (curved surface, point cloud) created from the results of measuring the deteriorated shape (defects, thinning) of the evaluation target using UT. The remaining life assessment method is characterized by the following. [Effects of the Invention]

[0012] According to the present invention, a soundness evaluation of defects detected during inspection can be performed in a short time, thereby enabling a prompt maintenance plan to be provided. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a flow diagram showing an evaluation procedure in a remaining life evaluation system (fatigue crack growth evaluation) according to a first embodiment of the present invention. [Figure 2] A diagram showing a part of a pipe divided into elements in a grid-like mesh. [Figure 3] FIG. 10 is a diagram showing a schematic diagram of a method for reflecting a measured shape in an analysis model. [Figure 4] FIG. 10 is a diagram showing an example of an analysis model that reflects the results of non-destructive testing. [Figure 5] A diagram showing an example of element and node number settings in a basic analysis model. [Figure 6] FIG. 6 is a flow chart showing an evaluation procedure in a remaining life evaluation system (fatigue crack initiation evaluation) according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In Example 1, the application of the remaining life assessment system to fatigue crack propagation evaluation will be described, and in Example 2, the application of the remaining life assessment system to fatigue crack initiation evaluation will be described. [Example]

[0015] Figure 1 is a flow diagram showing the evaluation procedure in a remaining life assessment system according to a first embodiment of the present invention. The remaining life assessment system 1 (fatigue crack propagation assessment) shown in Figure 1 evaluates, in this example, the fatigue crack propagation life of equipment in a power plant facility, for example. The processing steps in the remaining life assessment system 1 are outlined as follows: a preparatory step 11 in which an analytical model corresponding to the sound state and design state of the part to be evaluated is created in advance; an on-site measurement step 12 in which inspections are performed using nondestructive testing during periodic inspections to measure defects and deteriorated shapes in the part to be evaluated; an application step 13 in which the inspection results and dimensional measurement results obtained during manufacturing are applied to the analytical model; and an evaluation step 14 in which fatigue crack propagation is evaluated using the finite element method to evaluate the remaining life.

[0016] In the present invention, it is assumed that the preparation step 11 and the on-site measurement step 12 are performed manually in advance, and the reflection step 13 and the evaluation step 14 are performed by a computer. Note that the evaluation of piping will be described here.

[0017] First, in advance preparation step 11 (first stage), specifically processing step S10, a finite element analysis model is created in advance as an analysis model corresponding to the soundness and design state of the part to be evaluated, for example, a piping model based on the design shape (soundness state). In this invention, fatigue crack propagation is assumed to be evaluated using X-FEM, so the part to be evaluated for fatigue crack propagation is modeled using a lattice mesh.

[0018] Figure 2 shows a portion of a pipe 20 divided into elements in a lattice mesh, and at this stage, an analysis model is created with dimensions consistent with the design drawings. As shown in the example of enlarged view 21, the lattice mesh is created not only on the inner surface of the pipe, but also in the thickness direction. At this time, it is recommended that the nodes of each element of the analysis model (the four corners of the elemental mesh) be divided evenly in the radial direction 61, circumferential direction 62, and axial direction 63 of the pipe 20.

[0019] Next, in the on-site measurement process 12 (second stage) shown in Figure 1, non-destructive testing is performed during regular inspections to measure defects and deterioration shapes in the evaluation target area. Specifically, in processing step S11, the pipe wall thickness (including thinning) and crack shape are measured using a UT inspection, which is generally used to detect defects. At this time, when targeting welded areas, it is advisable to also evaluate shapes such as back ripples. Note that a more accurate evaluation is possible if elliptical deformation of the pipe can be measured using a non-contact 3D measuring device or the like.

[0020] In the reflection step 13 (third stage), in which the inspection results and the dimensional measurement results during manufacturing are reflected in the analysis model, specifically, the shape of the evaluation object obtained by non-destructive testing in processing step S12 is imported as surface data (for example, surface / point cloud data of the measured shape), and in processing step S13, the data is reflected in the basic analysis model prepared in the first stage (preparation step 11) based on the aging shape indicated by the data.

[0021] Figure 3 is a schematic diagram of how the measured shape is reflected in the analysis model. Figure 3 is a diagram showing an enlarged cross section of the pipe in the radial direction 61, i.e., a thick portion of the pipe, and shows an example in which the inner circumferential surface of the pipe, which was simulated as 30 at the time of pipe design (when the pipe began operation), is simulated as 34 after the inner circumferential surface has been thinned by a crack. Note that 31 indicates the simulated line of the first layer meshed in a lattice pattern in the thickness direction, and the first layer after the crack is shown as the simulated line 35.

[0022] In the present invention, as shown in Figure 3, as an example of the reflection process 13 when a crack is measured on the inner surface 30 in the on-site measurement process 12 (second stage), the shape of the thick pipe wall at the crack site is simulated by an arc-shaped inner surface 34 and first layer 35, and the measured shape is reflected in the analysis model.

[0023] In the reflection step 13 in Figure 3, which shows a case where localized thinning is measured on the inner surface of a pipe, the nodes (the four corners of the elementized mesh) on the inner surface of the pipe's analytical model are first moved to the curved surface of the measured inner surface. Note that the movement of the nodes (for example, moving node 33 to node 34) is adjusted only in the radial direction 61 of the pipe, with the coordinates in the axial direction 63 and circumferential direction 62 remaining fixed. The node on the first layer (35) in the depth direction from the inner surface is also moved to match the crack depth in the radial direction 61, and this too is moved only in the radial direction, with the coordinates in the axial direction 62 and circumferential direction 63 remaining fixed. While the initial crack shape in X-FEM requires a shape dependent on the element shape in the general-purpose analysis code Abaqus, the initial defect shape is defined using the elements on the moved surface.

[0024] From the second layer onwards, the nodes are moved radially to match the distance between the coordinates of the nodes on the first layer 35 and the outer surface. The amount of node movement is adjusted using an iterative method such as Newton's method. Figure 4 shows an example where a localized metal loss shape is assumed and reflected in the analysis model. This method makes it easy to reflect the shape of aging obtained through non-destructive testing. In Figure 4, crack 24 represents a simulated crack that occurred between the surface layer 34 and the first layer 35.

[0025] In evaluation process 14 (fourth stage), in which fatigue crack propagation evaluation is performed using the finite element method and the remaining life is evaluated, fatigue crack propagation analysis such as crack propagation evaluation is performed in processing step S14 using an analytical model that reflects the shape and defect shape obtained by non-destructive testing created in the third stage, and the life until penetration, for example, can be calculated in processing step S15.

[0026] In the analysis model created in advance, as shown in Fig. 5, node and element numbers can be assigned to any digit for the radius, circumference, and axial directions, and created with consecutive numbers. This makes it easy to identify the position of each node when changing the shape of the analysis model and setting the crack position in the third stage, thereby making model corrections more efficient.

[0027] 5, for example, 43 is an element (grid mesh), 44 is a node, and each contact point is expressed by a code indicating the radial direction 61, the circumferential direction 62, and the axial direction 63. For example, the last two digits of the five-digit code are number 46 indicating the radial direction 61, the middle two digits of the five-digit code are number 47 indicating the axial direction 63, and the first digit of the five-digit code is number 48 indicating the circumferential direction 62. [Example]

[0028] 1 is a flow chart showing an evaluation procedure in a remaining life evaluation system (fatigue crack initiation evaluation) according to Example 2 of the present invention. The fatigue crack growth evaluation system shown in FIG. 1 has the processing step S14 of the fatigue crack growth evaluation process removed, and instead has a crack initiation life evaluation (fatigue crack initiation prediction) function as processing step S14A, making it a system for predicting the crack initiation life of equipment in a power plant facility.

[0029] This system consists of a preparation process 11 in which an analytical model equivalent to the sound and designed state of the part to be evaluated is created in advance, an on-site measurement process 12 in which non-destructive testing is carried out during regular inspections to measure the deteriorated shape of the part to be evaluated (oval deformation, thinning, etc.), an input process 13 in which the inspection results and dimensional measurement results during manufacturing are reflected in the analytical model, and an evaluation process 14 in which fatigue crack initiation is evaluated using the finite element method and the lifespan is evaluated. In this example, by measuring the outer surface shape using non-contact 3D measurement and evaluating the plate thickness using UT, it is possible to predict crack initiation taking into account errors during manufacturing and deformed shapes due to operation. [Explanation of symbols]

[0030] 1: Fatigue crack growth evaluation system 11: Advance preparation process 12: On-site measurement process 13: Reflection process 14: Evaluation process 20: Piping analysis model 21: Expanding the piping analysis model 22:Analysis model reflecting measurement results 23: Expanding the analytical model to reflect measurement results 31: Element boundary (basic model, first layer) 30: Pipe inner surface (basic model) 32: Post-movement node (measurement shape) 33: Pre-movement node (basic model) 34: Definition surface of measurement shape 35: Definition surface equivalent to crack depth 61: Radial direction 63: Axial direction 62: Circumferential direction 43: Element 44: Node 45: Node number 46: Radial node number assignment 47: Node number assignment in the axial direction 48: Circumferential node number assignment

Claims

1. A remaining life assessment system for assessing the remaining life of a structure, comprising: The method comprises a preparatory step of preparing an analytical model corresponding to the sound state and design state of the evaluation target part of the structure in advance, an on-site measurement step of inspecting and measuring the shape of the evaluation target part, an reflecting step of reflecting the dimensional measurement results of the evaluation target part obtained in the on-site measurement step in the analytical model, and an evaluation step of evaluating the remaining life of fatigue cracks using the finite element method, In the reflection process, the measured shape (surface, point cloud) of the deteriorated shape (defects, thinning) of the object to be evaluated is reflected by moving the nodes of a pre-prepared analysis model only in the radial direction of the pipe to the shape (surface, point cloud) created from the results of measuring the deteriorated shape (defects, thinning) of the object to be evaluated using UT.

2. 2. The remaining life assessment system according to claim 1, The remaining life assessment system is characterized in that the assessment step comprises assessing fatigue crack growth.

3. 2. The remaining life assessment system according to claim 1, The remaining life assessment system is characterized in that the assessment step comprises assessing occurrence of fatigue cracks.

4. 2. The remaining life assessment system according to claim 1, A remaining life assessment system characterized in that in the assessment step, a mesh-free method (extended finite element method: X-FEM) is used for fatigue crack growth assessment using the finite element method.

5. 2. The remaining life assessment system according to claim 1, A remaining life assessment system characterized in that, in the shape adjustment of the analysis model in the reflection process, the surface on the side where the defect shape is reflected and the depth direction are moved to match the initial crack depth assumed for the next node.

6. 2. The remaining life assessment system according to claim 1, A remaining life assessment system characterized in that, in the shape adjustment of the analysis model in the reflection step, the movement of nodes uses an iterative method in accordance with the curved surface and point group of the movement destination.

7. 2. The remaining life assessment system according to claim 1, A remaining life assessment system characterized in that, in an analytical model of the evaluation target that is prepared in advance, when the target is piping, node and element numbers for the evaluation section are assigned identifiable numbers in any digits according to radius, circumference, and axial direction.

8. A remaining life assessment method for assessing the remaining life of a structure, comprising: An analytical model corresponding to the sound state and design state of the evaluation target part of the structure is created in advance, an inspection is performed, the shape of the evaluation target part is measured, the dimensional measurement results of the evaluation target part are reflected in the analytical model, and a remaining life evaluation of fatigue cracks is performed using the finite element method; A remaining life assessment method characterized in that, in the reflection, the measured shape is reflected by moving the nodes of a pre-prepared analytical model only in the radial direction of the pipe to a shape (curved surface, point cloud) created from the results of measuring the deteriorated shape (defects, thinning) of the evaluation target using UT.

9. A remaining life assessment method according to claim 8, comprising:

10. A remaining life assessment method, wherein the remaining life assessment is an assessment of fatigue crack growth.

10. 9. A remaining life assessment method according to claim 8, comprising:

10. A remaining life assessment method, wherein the remaining life assessment is an assessment of fatigue crack initiation.

Images