Destructive evaluation device, method, and program

Abstract

To provide a breakdown evaluation technique of easily and instantaneously performing breakdown evaluation of an instrument, structure or the like and quickly determining the propriety of a continuous operation and a period thereof as well as maintenance countermeasures and plan such as continuous inspection, repair and replacement.SOLUTION: A breakdown evaluation device 10 comprises: a regulation part 11 of a first parameter 21 indicating the shape of a crack model 32 of a defect 31; a regulation part 12 of a second parameter 22 indicating the stress distribution; a registration part 15 of a breakdown load 25 calculated by inputting data (a,c,Pm,Pb) about the shape of the crack model 32 and the stress distribution; a setting part 16 of coordinates with a continuous variable of a crack dimension 26 and the breakdown load 25 as two axes; a setting part 17 which sets any of the first parameter 21 and the second parameter 22 as a constant number; a setting part 18 which sets the other as a discrete variable; and a graph creation part 19 which overwrites the coordinates with a plurality of line graphs corresponding to each discrete variable.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a technique for evaluating damage caused by defects in equipment or structures. [Background technology]

[0002] As nuclear power generation facilities age and their lifespans are extended, the risk of age-related deterioration events occurring is increasing. Under these circumstances, it is becoming increasingly important to address the risk of age-related deterioration events occurring. Stable operation and improved availability of power generation facilities are important from the perspective of efficient use of the entire facility and a stable supply of electricity.

[0003] In order to determine maintenance measures and plans for equipment, structures, etc., inspections are conducted to detect defects related to age-related deterioration phenomena. Dimensional measurements (sizing) of the detected defects are then performed to evaluate the damage to the equipment, structures, etc. Based on the results of this damage evaluation, decisions are made regarding maintenance measures and plans, such as continued operation, repair, or replacement.

[0004] In the destructive assessment, the material properties of the target equipment or structure are set, a modeled defect is applied, and pre-established evaluation formulas and structural analysis methods are used. The destructive load for the defect size is then evaluated, and the appropriate maintenance measures and plans for the equipment or structure are determined. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-60244 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the typical process of fracture assessment requires time and effort to prepare reliable data on material properties. Furthermore, advanced knowledge of nonlinear analysis and finite element analysis using various evaluation methods is required. For these reasons, fracture assessment is generally difficult. In particular, when the material properties of the target equipment or structure change during its service life, fracture assessment inevitably becomes a complicated procedure.

[0007] In other words, previous fracture assessment procedures required a huge amount of time and effort, including modeling defects, preparing the necessary input parameters, performing stress analysis, conducting the assessment, and analyzing the assessment results, and also involved complicated calculations and analyses.

[0008] In this way, it takes a long time to carry out a destructive evaluation of defects detected during inspections and to determine maintenance measures and plans for structures, etc. This requires time to decide how to deal with detected defects, which results in unnecessary extended shutdowns of the entire facility.

[0009] The embodiments of the present invention have been made in consideration of the above circumstances, and have as their object to provide a destructive evaluation technology that can easily and instantly perform destructive evaluation of equipment, structures, etc., and quickly determine whether or not continued operation is possible and for how long, as well as maintenance measures and plans such as continued inspections, repairs, and replacements. [Means for solving the problem]

[0010] In the destruction evaluation device of the embodiment, it comprises a first definition unit that defines a first parameter indicating the shape of a crack model of a defect assumed in the evaluation object, a second definition unit that defines a second parameter indicating the stress distribution assumed in the evaluation object, a registration unit that registers the fracture load of the evaluation object output by calculation in response to input of data regarding the shape of the crack model and the stress distribution, a coordinate setting unit that sets coordinates with continuous variables of the crack dimension of the defect and the fracture load as two axes, a constant setting unit that sets one of the first parameter and the second parameter to a constant, a discretization setting unit that sets the other of the first parameter and the second parameter to a discrete variable, and a graph creation unit that creates an evaluation graph in which multiple line graphs corresponding to each of the discrete variables are overlaid on the coordinates. [Effects of the Invention]

[0011] An embodiment of the present invention provides a destructive evaluation technology that allows for simple and instantaneous destructive evaluation of equipment, structures, etc., and quickly determines whether or not continued operation is possible and for how long, as well as maintenance measures and plans such as continued inspections, repairs, and replacements. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a block diagram of a destruction evaluation device according to an embodiment of the present invention. [Figure 2] (A) Front view of an evaluation object with a defect opening on the surface, (B) longitudinal cross-sectional view of the same, (C) explanatory diagram of a crack model of a defect opening on the surface of the evaluation object. [Figure 3] (A) A diagram showing the stress distribution acting on the cross section of the evaluation object, (B) a diagram showing the membrane stress component of the stress distribution, and (C) a diagram showing the bending stress component of the stress distribution. [Figure 4] Evaluation graph in which the first parameter, which is the aspect ratio of the crack model, is set as a discrete variable. [Figure 5] Evaluation graph in which the second parameter, which is expressed as the ratio of membrane stress to bending stress, is set as a discrete variable. [Figure 6]The graph shows the relationship between the initial flaw size and the fracture load when the second parameter is set as a discrete variable (when the initial flaw depth is 5 mm). [Figure 7] The graph shows the relationship between the initial flaw size and the fracture load when the second parameter is set as a discrete variable (when the initial flaw depth is 10 mm). [Figure 8] The graph shows the relationship between the initial flaw size and the fracture load when the second parameter is set as a discrete variable (when the initial flaw depth is 15 mm). [Figure 9] The graph shows the relationship between the initial flaw size and the fracture load when the second parameter is set as a discrete variable (when the initial flaw depth is 20 mm). [Figure 10] 2 is a flowchart illustrating the steps of a destruction assessment method and an algorithm of a destruction assessment program according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a block diagram of a destruction evaluation device 10 according to an embodiment of the present invention. As shown in Figs. 1 and 2, the destruction evaluation device 10 includes a first defining unit 11 that defines first parameters 21 indicating the shape of a crack model 32 of a defect 31 assumed in an evaluation object 30, and a second defining unit 12 that defines second parameters 22 indicating the stress distribution (Fig. 3(A)) assumed in this evaluation object 30.

[0014] Furthermore, the destruction evaluation device 10 acquires data (a, c, P) relating to the shape and stress distribution of the crack model 32 (FIG. 3(A)). m ,P b), a coordinate setting unit 16 that sets coordinates with continuous variables of the crack dimension 26 of the defect 31 and the fracture load 25 as two axes, a constant setting unit 17 that sets one of the first parameter 21 and the second parameter 22 as a constant, a discretization setting unit 18 that sets the other of the first parameter 21 and the second parameter 22 as a discrete variable, and a graph creation unit 19 that creates an evaluation graph 27 (see Figures 4 and 5) in which multiple line graphs corresponding to each of these discrete variables are superimposed on the coordinates.

[0015] Fig. 2(A) is a front view of an evaluation object 30 having a defect 31 opening on the surface. Fig. 2(B) is a longitudinal cross-sectional view of the evaluation object 30. Fig. 2(C) is an explanatory diagram of a crack model 32 of the defect 31. The first defining unit 11 defines a crack model 32 for this defect 31 that simulates a semi-elliptical surface crack.

[0016] Regarding the dimensions of the crack model 32, taking into consideration the detection limit in defect inspection by visual inspection of reactor internal structures, for example, the minimum dimensions for a semi-elliptical circumferential inner surface defect are set to 1 mm deep x 10 mm long, etc. Then, using the initial defect with the set minimum dimensions as a reference, the shape of the crack model 32 is specified at appropriate dimensional intervals.

[0017] The evaluation object 30 may be a part such as a bolt or nut, or may be a large structure such as a pressure boundary of a reactor pressure vessel, a core shroud, or recirculation system piping. The evaluation object 30 may also be other equipment or structural parts of a nuclear power plant, and may also be structures of other power generation facilities, without being limited to nuclear power plants.

[0018] In this embodiment, the first parameter 21 that defines the surface crack defect 31 is the aspect ratio (a / c), which is the ratio of the crack depth a to the crack length (semi-length) c of the semi-elliptical crack model 32. Note that the defect 31 targeted by the first defining unit 11 is not limited to the surface crack shown as an example, but may also be an internal crack that does not have an opening on the surface. Furthermore, the first parameter 21 that defines the shape of the crack model 32 does not need to be limited to the aspect ratio (a / c).

[0019] 3A is a diagram showing the stress distribution acting on the cross section of the evaluation object 30. FIG. 3B is a diagram showing the membrane stress P m Fig. 3(C) shows the bending stress P b In the second defining section 12, the second parameter 22 is defined as the film stress P m and bending stress P b Ratio of (P m / P b ) The second parameter 22 is defined as (P m / P b ) and any method that defines the stress distribution expected in the evaluation object 30 can be used as appropriate.

[0020] The calculation unit 20 calculates the data (a, c, P) relating to the shape and stress distribution of the crack model 32. m ,P b ) input, the breaking load 25 (P f ) and register it in the registration unit 15. These input variables and the breaking load 25 (P f ) is expressed by the following relational expression (1): The details of the calculation unit 20 will be described later. P f =f(P m ,P b ,a,c)···(1)

[0021] FIG. 4 shows an evaluation graph 27a in which the first parameter 21 expressed by the aspect ratio (a / c) of the crack model 32 is set as a discrete variable. m and bending stress P b Ratio of (P m / P b) the second parameter 22(P m / P b ) is set as a discrete variable. Note that the crack dimension 26 shown on the horizontal axis of the evaluation graph 27 is represented by the crack depth a, but may also be represented by the crack length (half length) c.

[0022] Returning to FIG. 1, the explanation will be continued. The coordinate setting unit 16 sets the continuous variable of the crack dimension 26(a) on the horizontal axis of the evaluation graph 27. Then, the fracture load 25(P f ) are set as continuous variables. The scales of these two axes can be set arbitrarily.

[0023] The constant setting unit 17 sets the second parameter 22 (P m / P b ) is set as a constant, the discretization setting unit 18 sets the first parameter 21(a / c) as a discrete variable. m +P b Furthermore, the discretization setting unit 18 also sets the range and interval of the discrete variables as shown in FIG. 4, i.e., a / c=0.1 to 2.0. As a result, the graph creation unit 19 creates a plurality of line graphs corresponding to each of these discrete variables (a / c) in plane coordinates (aP f ) to create an evaluation graph 27a(27).

[0024] When the constant setting unit 17 sets the first parameter 21 (a / c) to a constant, the discretization setting unit 18 sets the second parameter 22 (P m / P b ) is set as a discrete variable. Then, the discretization setting unit 18 sets P m +P b By imposing a constraint that keeps P constant, m / P b = 0.1 to 2.0, the range and interval of the discrete variables are set as shown in FIG. 5. As a result, the graph creation unit 19 calculates the values ​​of each of these discrete variables (P m / P b ) are plotted on a plane coordinate system (aP f ) to create an evaluation graph 27b(27).

[0025] The breaking load on the vertical axis is 25 (P f ) may be a conservatively reduced value taking into account the safety factor (SF). The area below each line is the area where it is judged that no destruction occurs, and the area above is the area where destruction occurs. In the explanation, it is assumed that the evaluation graph 27 (27a, 27b) is displayed graphically, but it is not necessary to visually confirm the evaluation graph 27 as shown. In other words, for example, it may be expressed in the form of a numerical table or a function showing the relationship between the defect size and the allowable load. In the case of a function, the data (a, c, P) relating to the shape and stress distribution (Fig. 3(A)) of the crack model 32 of the measured defect are used. m ,P b ) allows for accurate and instantaneous destruction judgment and display.

[0026] Furthermore, a three-dimensional display may be used in addition to the two-dimensional evaluation graph 27. Furthermore, by combining these graph displays with function forms, it is possible to create a form that meets the user's convenience in terms of both visual appearance and accuracy.

[0027] The evaluation unit 28 evaluates the limit conditions for fracture of the evaluation object 30 based on the evaluation graph 27. That is, the limit conditions for fracture with respect to the load applied to the evaluation object 30 and the crack size of the defect 31 can be evaluated in light of the first parameter 21 and the second parameter 22. Alternatively, the limit conditions for fracture with respect to the known first parameter 21 and second parameter 22 can be evaluated in light of the applied load and the crack size of the defect 31.

[0028] For example, in Figures 4 and 5, the crack size (crack depth) is a s The object to be evaluated 30 in which the defect 31 is detected is P s When a load of is applied, the aspect ratio is 0.5 or more and the stress distribution (P m / P b ) is 0.5 or more, the evaluation unit 28 can instantly make a conservative judgment that there is no risk of fracture. Note that the evaluation unit 28 can perform not only the evaluation based on determinism as described above, but also evaluation based on, for example, probabilistic fracture mechanics (PFM) based on probability theory.

[0029] In this way, the evaluation graph 27 (27a, 27b) created by the destruction evaluation device 10 is used to evaluate the impact of defects found in an investigation of a nuclear reactor facility or the like on a structure. The destruction load 25 (P f The evaluation graph 27 showing the defect 31 can be prepared in advance prior to the investigation of the defect 31. This can shorten the evaluation period for the destruction of the evaluation object 30, and can avoid a situation in which the plant shutdown period is extended.

[0030] The calculation unit 20 evaluates the fracture parameters from the stress acting on the evaluation object 30 having the defect 31, and calculates the fracture load 25 (P f ) is calculated. Examples of such fracture parameters include stress intensity factors in the evaluation of linear fracture mechanics criteria for brittle fracture, and J-integral and collapse load (maximum load) in the evaluation of elastic-plastic fracture mechanics and plastic collapse criteria for ductile fracture. The stress intensity factor can be calculated using simplified evaluation formulas published in standards such as the Japan Society of Mechanical Engineers' Maintenance Standards and ASME Boiler & Pressure Vessel Code Section XI, or widely known simplified evaluation formulas such as the Raju & Newman formula or influence function method, or it can be calculated using finite element method (FEM) analysis.

[0031] The stress intensity factor K is calculated for each of the three modes: in-plane opening mode I, in-plane shear mode II, and out-of-plane shear mode III. However, for example, these three modes may be combined into mode I to be on the safe side and set as representative by mode I. The following explanation will be given taking the case where mode I is used as an example. In this case, the stress intensity factor K is calculated as follows: I It is expressed as follows. It is assumed that a far-field stress σ is applied to the evaluation object 30. The stress intensity factor K for a defect at a depth a at each time point is I can be calculated using the following formula (2). Stress concentration factor K I =σ√(πa) (2)

[0032] The J-integral required for elastic-plastic fracture mechanics evaluation can be calculated using the reference stress method with the stress intensity factor mentioned above, or directly using FEM analysis. Numerical analysis using the GTN (Gurson-Tvergaard-Needleman) model is also available as a method for evaluating fracture behavior associated with ductile crack propagation, and this method can determine the limit load of a structure with a defect, i.e., the maximum load that the structure can withstand. Furthermore, in the evaluation of plastic collapse criteria, the limit load can be similarly determined using limit analysis.

[0033] Figures 6 to 9 show the P when the initial crack size (defect depth) is 5 mm, 10 mm, 15 mm, and 20 mm, respectively. m / P b The second parameter 22 expressed as f ) is a graph showing the relationship between the breaking load 25 (P f ) is determined based on the crack size of the defect 31 and the stress applied to the defect 31. In other words, the critical load determined for the above-mentioned fracture parameters is the fracture load 25 (P f ) and the membrane stress (P m ) and bending stress (P b ) ratio (P m / P b ) is calculated repeatedly for all cases, and the curve of the fracture load against an arbitrary applied load for a given crack size is evaluated. Based on the evaluation results shown in Figures 6 to 9, the evaluation graphs 27 (27a, 27b) shown in Figures 4 and 5 are constructed.

[0034] The breaking load is 25 (P f In addition to the above-mentioned methods, there is also a method of determining the initial dimensions corresponding to the fracture criteria from the load applied to the structure by inverse analysis. It is also possible to set an applied load that determines fracture, and then determine the initial crack dimensions that satisfy that condition by inverse analysis as a response surface.

[0035] The steps of the destruction assessment method and the algorithm of the destruction assessment program according to the embodiment of the present invention will be described with reference to the flowchart in Figure 10. First, first parameters 21 indicating the shape of a crack model 32 of a defect 31 assumed in the evaluation object 30 are defined (S11). Then, second parameters 22 indicating the stress distribution (Figure 3(A)) assumed in the evaluation object 30 are defined (S12).

[0036] Next, data on the shape and stress distribution of the crack model 32 (P m ,P b The fracture load 25 of the evaluation object 30 output by calculation in response to the inputs of (a, c) is registered (S13). Then, a coordinate system is set with two axes representing the continuous variables of the crack size 26 and the fracture load 25 (S14).

[0037] Next, one of the first parameter 21 and the second parameter 22 is set to a constant (S15 (S15A, S15B)), and the other of the first parameter 21 and the second parameter 22 is set to a discrete variable (S16 (S16A, S16B)). Then, an evaluation graph 27 (27a, 27b) is created in which a plurality of line graphs corresponding to each of these discrete variables are superimposed on the coordinates (S17 (S17A, S17B)).

[0038] Next, the evaluation object 30 is inspected to detect a defect 31 (S18). Then, a crack model 32 is associated with this defect 31 to set its dimensions, and a first parameter 21 (aspect ratio (a / c)) is acquired (S19). Furthermore, a second parameter 22 (membrane stress P m and bending stress P b Ratio of (P m / P b )) is obtained (S20).

[0039] Next, the crack size of the detected defect 31, the first parameter 21, and the second parameter 22 are compared with the evaluation graph 27 (27a, 27b) (S21), and the fracture load 25 (P f ) is evaluated (S22, END).

[0040] By preparing the evaluation graph 27 in advance in this way, it is possible to speed up the destructive evaluation of the evaluation object 30 based on the dimensions of the defect 31 detected at the inspection site or through monitoring. However, there may be cases where the defect 31 cannot be measured by actual inspection, the measurement results themselves contain a great deal of uncertainty, or parameters such as depth, length, and shape are unknown. In such cases, it is possible to use available dimensional information and set defect dimensions that are deemed conservative and technically appropriate based on the condition and geometric shape of the target part, the required function, past performance, etc.

[0041] According to at least one embodiment of the destruction assessment device described above, by specifying a first parameter indicating the shape of the crack model and a second parameter indicating the stress distribution, it is possible to easily and instantly assess the destruction of equipment, structures, etc., and quickly determine whether or not they can continue to operate and for how long, as well as maintenance measures and plans such as continued inspections, repairs, and replacements.

[0042] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, modifications, and combinations can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as the inventions described in the claims and their equivalents.

[0043] The destruction assessment device described above includes a control device with a highly integrated processor such as a dedicated chip, FPGA (Field Programmable Gate Array), GPU (Graphics Processing Unit), or CPU (Central Processing Unit), a storage device such as ROM (Read Only Memory) or RAM (Random Access Memory), an external storage device such as HDD (Hard Disk Drive) or SSD (Solid State Drive), a display device such as a monitor, input devices such as a mouse and keyboard, and a communication I / F, and can be realized with a hardware configuration using a normal computer. Therefore, the components of the destruction assessment device can also be realized by a computer processor and can be operated by a destruction assessment program.

[0044] The destruction assessment program may be provided by being pre-installed in a ROM, etc. Alternatively, the program may be provided by being stored in an installable or executable file format on a computer-readable storage medium such as a CD-ROM, CD-R, memory card, DVD, or flexible disk (FD).

[0045] The destruction assessment program according to this embodiment may be stored on a computer connected to a network such as the Internet and provided by downloading it via the network. The destruction assessment device may also be configured by combining separate modules that independently perform the functions of the components and are interconnected via a network or dedicated lines. [Explanation of symbols]

[0046] 10...destruction evaluation device, 11...first definition unit, 12...second definition unit, 15...registration unit, 16...coordinate setting unit, 17...constant setting unit, 18...discretization setting unit, 19...graph creation unit, 20...calculation unit, 21...first parameter, 22...second parameter, 25...fracture load, 26...crack dimension, 27 (27a, 27b)...evaluation graph, 28...evaluation unit, 30...evaluation object, 31...defect, 32...crack model.

Claims

1. a first defining unit that defines a first parameter indicating a shape of a crack model of a defect assumed in the evaluation object; a second defining unit that defines a second parameter indicating a stress distribution assumed in the evaluation object; a registration unit that registers the fracture load of the object to be evaluated, which is output by calculation in response to input of data relating to the shape of the crack model and the stress distribution; a coordinate setting unit that sets a coordinate having two axes representing continuous variables of the crack size of the defect and the fracture load; a constant setting unit that sets one of the first parameter and the second parameter to a constant; a discretization setting unit that sets the other of the first parameter and the second parameter to a discrete variable; a graph creating unit that creates an evaluation graph in which a plurality of line graphs corresponding to each of the discrete variables are superimposed on the coordinates.

2. 2. The destructive evaluation device according to claim 1, A destruction evaluation device in which the crack model employs a semi-elliptical surface crack, and the first parameter is an aspect ratio of the crack model.

3. 3. The destructive evaluation device according to claim 1 or 2, The second parameter is a ratio of membrane stress to bending stress.

4. 4. The destructive evaluation device according to claim 3, A destruction evaluation device in which the second parameter is set as a discrete variable and the destruction load is determined based on a graph showing the relationship between the crack size and the destruction load.

5. A step of defining a first parameter indicating the shape of a crack model of a defect assumed in the evaluation object; defining a second parameter indicating an expected stress distribution in the evaluation object; a step of registering a fracture load of the object to be evaluated that is output by calculation in response to input of data relating to the shape of the crack model and the stress distribution; setting a coordinate system having two axes representing continuous variables of the crack size of the defect and the fracture load; setting one of the first parameter and the second parameter to a constant; setting the other of the first parameter and the second parameter to a discrete variable; and creating an evaluation graph in which a plurality of line graphs corresponding to each of the discrete variables are superimposed on the coordinates.

6. On the computer, A step of defining a first parameter indicating the shape of a crack model of a defect assumed in the evaluation object; defining a second parameter indicating an expected stress distribution in the evaluation object; a step of registering the fracture load of the object to be evaluated output by calculation in response to input of data relating to the shape of the crack model and the stress distribution; setting a coordinate system having two axes representing continuous variables of the crack size of the defect and the fracture load; setting one of the first parameter and the second parameter to a constant; setting the other of the first parameter and the second parameter to a discrete variable; and creating an evaluation graph in which a plurality of line graphs corresponding to each of the discrete variables are superimposed on the coordinates.

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