Remaining service life estimation method, remaining service life estimation device, and remaining service life estimation program

Abstract

This remaining service life estimation method, remaining service life estimation device, and remaining service life estimation program acquire a map generated on the basis of a pattern of backward scattering diffraction occurring due to reflected electrons from a material when the material is irradiated with an electron beam. From the map, the range of a prescribed number of crystal grains up to a surface where crack development occurs in the material is extracted as a specific range. An index value based on the crystal orientation of the material in the specific range is generated. A load condition is specified on the basis of the index value in the specific range. The remaining service life of the material is estimated on the basis of the surface crack length of the crack with reference to the relationship between the surface crack length and a service life ratio under the load condition.

Description

Remaining life estimation method, remaining life estimation device, and remaining life estimation program

[0001] The present disclosure relates to a remaining life estimation method, a remaining life estimation device, and a remaining life estimation program.

[0002] Patent Literature 1 discloses a method for evaluating the crack growth rate of a metal material by measuring the crystal orientations at multiple measurement points within a region including the tip of a crack in the material using the EBSP method. In this method, misorientation function values ​​indicating the deviation of the crystal orientations at each measurement point are analyzed to obtain evaluation parameters for the material, and the crack growth rate of the material is evaluated based on the evaluation parameters.

[0003] JP 2012-73126 A

[0004] The technology described in Patent Document 1 has the problem that the tip position of a crack that actually occurs in a material and the load conditions related to the strain that caused the crack cannot be directly measured, or that estimating them requires complicated calculations.

[0005] The present disclosure has been made in view of the above-mentioned problems, and has an object to provide a remaining life estimation method, a remaining life estimation device, and a remaining life estimation program that are capable of determining the tip position of a crack that has actually occurred in a material and the loading conditions related to the strain that caused the crack, and estimating the remaining life of the material.

[0006] The remaining life estimation method according to the present disclosure acquires a map generated based on a backscatter diffraction pattern of electrons reflected from a material when the material is irradiated with an electron beam. From the map, a range of a predetermined number of crystal grains up to the propagation surface of a crack generated in the material is extracted as a specific range. An index value based on the crystal orientation of the material in the specific range is generated. Loading conditions are identified based on the index value in the specific range. The remaining life of the material is estimated based on the surface crack length of the crack, with reference to the relationship between the surface crack length and the life ratio under the loading conditions.

[0007] The load condition may be identified based on a specific average value that is the average of the index values ​​in a specific range.

[0008] The predetermined number may be two.

[0009] The length of the particular range along the direction of crack propagation or the direction perpendicular to the surface of the material may be five times or more the diameter of the crystal grains contained in the material.

[0010] The length of the particular range along the direction of crack propagation or perpendicular to the surface of the material may be 25 times or less the diameter of a crystal grain contained in the material.

[0011] The index value may be calculated as a value indicating the average difference between the crystal orientation of the pixel and the crystal orientation of adjacent pixels adjacent to the pixel, within a crystal grain contained in the material to which the pixel included in the map belongs.

[0012] The average value of the crystal orientations of pixels contained in crystal grains included in the material may be calculated, and a value indicating the average difference of the crystal orientations of the pixels from the average value may be calculated as the index value.

[0013] The remaining life estimation device according to the present disclosure includes an acquisition unit and a controller. The acquisition unit acquires a map generated based on a backscatter diffraction pattern of electrons reflected from a material when the material is irradiated with an electron beam. The controller extracts, from the map, a range of a predetermined number of crystal grains up to the propagation surface of a crack generated in the material as a specific range. An index value based on the crystal orientation of the material in the specific range is generated. Load conditions are identified based on the index value in the specific range. The remaining life of the material is estimated based on the surface crack length of the crack, with reference to the relationship between the surface crack length and the life ratio under the load conditions.

[0014] The remaining life estimation program according to the present disclosure processes a map generated based on a backscatter diffraction pattern of electrons reflected from a material when the material is irradiated with an electron beam. A computer extracts from the map a range of a predetermined number of crystal grains up to the propagation surface of a crack generated in the material as a specific range. An index value based on the crystal orientation of the material in the specific range is generated. Loading conditions are identified based on the index value in the specific range. The remaining life of the material is estimated based on the surface crack length of the crack, with reference to the relationship between the surface crack length and the life ratio under the loading conditions.

[0015] According to the present disclosure, it is possible to determine the tip position of a crack that has actually occurred in a material and the loading conditions related to the strain that caused the crack, and to estimate the remaining life of the material.

[0016] Fig. 1 is a block diagram showing a configuration of a remaining life estimation device according to an embodiment of the present disclosure; Fig. 2 is a flowchart showing a processing procedure of the remaining life estimation device; Fig. 3 is a diagram showing an example of a map; Fig. 4 is a diagram showing an example of a map in which only a specific range is extracted; Fig. 5 is a diagram showing an example of the relationship between the average value of index values ​​in a specific range and load conditions; Fig. 6 is a diagram showing an example of the relationship between surface crack length and life ratio;

[0017] Hereinafter, several exemplary embodiments will be described with reference to the drawings. Note that common parts in the drawings are given the same reference numerals, and duplicated explanations will be omitted.

[0018] [Configuration of Remaining Life Estimation Device] Figure 1 is a block diagram showing the configuration of a remaining life estimation device according to an embodiment of the present disclosure. As shown in Figure 1, the remaining life estimation device 20 includes a receiving unit 21, a database 23, and a controller 25. In addition, the remaining life estimation device 20 may include an operation unit 27 and a display unit 29. The controller 25 is connected to the receiving unit 21, the database 23, the operation unit 27, and the display unit 29 so as to be able to communicate with them.

[0019] In addition, the operation unit 27 and the display unit 29 may be provided in the remaining life estimation device 20 itself, or may be installed outside the remaining life estimation device 20 and connected to the remaining life estimation device 20.

[0020] The receiver 21 is connected wirelessly or by wire so as to be able to communicate with the crystal orientation map acquisition device 10. The receiver 21 receives from the crystal orientation map acquisition device 10 a map generated based on a backscatter diffraction pattern caused by electrons reflected from a material when the material is irradiated with an electron beam.

[0021] The material is, for example, a metallic material having crystal grains (such as a steel material whose main component is iron, or a non-ferrous metallic material whose main component is a metal other than iron, such as aluminum, titanium, magnesium, nickel, or copper). The material may also be many other crystalline materials, and is not limited to the examples given here.

[0022] Alternatively, the receiving unit 21 may receive the "surface crack length" of a crack that has occurred in the material. The surface crack length will be described later.

[0023] The crystal orientation map acquisition device 10 performs, for example, EBSD (Electron Backscatter Diffraction) measurement on a cracked material. The crystal orientation map acquisition device 10 then generates a map. The map is a map of the crystal orientation of the material generated based on the backscatter diffraction pattern.

[0024] The "cracks" referred to in this disclosure are those that occur when a material is placed in an environment with a temperature range of from room temperature to approximately 600°C. In this temperature range, cracks are said to propagate within crystal grains. On the other hand, at temperatures higher than this temperature range, cracks propagate along grain boundaries, resulting in a different fracture mode.

[0025] The crystal orientation map acquisition device 10 samples a vertical cross section of the material at the crack initiation point, performs EBSD measurement, and generates a map. For example, the vertical cross section to be sampled is a plane that passes through the crack initiation point and is perpendicular to the surface of the material.

[0026] The database 23 stores various information used for estimation by the controller 25. For example, the database 23 stores the relationship between the index value and the load condition. The relationship between the index value and the load condition may be stored in a table format or may be stored as an approximate formula.

[0027] The "load condition" is a parameter that characterizes the magnitude of strain when a strain test is performed on a material. For example, if a strain test is performed in which the length of the material expands or contracts by "X%", the "load condition" is expressed as "X%". In FIG. 3, "0.8%, "1.0%, "1.2%," and "1.5%" are shown as parameters indicating the "load condition". The "load conditions" stored in the database 23 are not limited to these, and the "load conditions" to be stored are determined by a strain test previously performed on the material.

[0028] The "index value" is a parameter that characterizes the magnitude of strain in the crystal grains contained in a material when a strain test is carried out under predetermined "load conditions."

[0029] For example, the index value may be calculated by calculating the average value of the crystal orientations of the pixels contained in the crystal grains for a map obtained by EBSD measurement of a material subjected to a strain test under a predetermined "load condition." In other words, the index value may be the grain orientation spread (GOS).

[0030] Alternatively, the index value may be a value indicating the average difference between the crystal orientation of the pixel and the crystal orientation of adjacent pixels in the crystal grain to which the pixel included in the map belongs. In other words, the index value may be KAM (Kernel Average Misorientation).

[0031] As shown in FIG. 5, the database 23 stores the relationship between the average index value and the load conditions. By using this relationship, it is possible to estimate the "load conditions" that led to the cracking of a material for which the "load conditions" are unknown. Specifically, an EBSD measurement is performed on the material in which the cracking has occurred, and the index value is calculated based on the map obtained by the EBSD measurement. Then, using the "relationship between the average index value and the load conditions," it is possible to estimate the "load conditions" that led to the cracking of the material from the calculated index value.

[0032] The database 23 stores the relationship between the surface crack length and the life ratio for each load condition. The relationship between the surface crack length and the life ratio may be stored in a table format or an approximate formula.

[0033] The "surface crack length" is the length of a crack that appears on the surface of a material when a strain test is conducted under specified "load conditions." The "surface crack length" increases as the number of loads applied in the strain test increases.

[0034] The "life ratio" is a value obtained by dividing the number of loads applied in a strain test under specified "load conditions" by the number of loads applied when the material breaks, and then normalizing the result. For example, if the number of loads applied when the material breaks is 100,000, the "life ratio" of a material that has only been loaded 50,000 times in the strain test is 50,000 times / 100,000 times = 0.5. Therefore, the "life ratio" can take a value between 0 and 1.

[0035] As shown in Figure 6, the database 23 stores the relationship between surface crack length and life ratio for each load condition. By using this relationship, it is possible to estimate the "life ratio" of a material whose "life ratio" is unknown based on the "load condition" and "surface crack length." Specifically, the load condition is estimated for a material in which a crack has occurred. The surface crack length on the surface of the material is also measured. Then, using the "relationship between surface crack length and life ratio" corresponding to the estimated load condition, the life ratio can be estimated based on the measured surface crack length.

[0036] The operation unit 27 is an input device that can be operated by a user of the remaining life estimation device 20. For example, the operation unit 27 is a keyboard, a mouse, a trackball, a touch panel, or the like. The operation unit 27 is not limited to the examples given here. The user's operation content input via the operation unit 27 is transmitted to the controller 25.

[0037] Additionally, the operation unit 27 may receive from the user the "surface crack length" of the crack that has occurred in the material.

[0038] The display unit 29 displays information received from the controller 25. For example, it displays the remaining life of the material estimated by the controller 25, which will be described later.

[0039] The display unit 29 may be a display that displays figures and characters by combining a plurality of display pixels, or may be a rotating light, a buzzer, etc. The display unit 29 is not limited to the examples given here.

[0040] The controller 25 (controller) is a general-purpose computer equipped with a CPU (central processing unit), memory, and input / output units. A computer program (remaining life estimation program) for functioning as the remaining life estimation device 20 is installed in the controller 25. By executing the computer program, the controller 25 functions as the multiple information processing circuits (251, 253, 255, 257) included in the remaining life estimation device 20. The computer program (remaining life estimation program) may be stored in a storage medium readable and writable by a computer.

[0041] In this disclosure, an example is shown in which multiple information processing circuits (251, 253, 255, 257) are realized by software. However, it is also possible to configure the information processing circuits (251, 253, 255, 257) by preparing dedicated hardware for executing each of the information processes described below. Furthermore, the multiple information processing circuits (251, 253, 255, 257) may be configured by individual hardware.

[0042] As shown in FIG. 1, the controller 25 includes a specific range extraction unit 251, an index value generation unit 253, a load condition specification unit 255, and a life ratio estimation unit 257 as a plurality of information processing circuits (251, 253, 255, 257).

[0043] The specific range extraction unit 251 extracts, from the received map, a range of a predetermined number of crystal grains up to the propagation surface of the crack that has occurred in the material as the specific range. For example, the specific range extraction unit 251 extracts a range consisting of crystal grains facing the propagation surface of the crack and crystal grains adjacent to the crystal grains facing the propagation surface of the crack, with the predetermined number being two.

[0044] Fig. 3 is a diagram showing an example of a map. Fig. 4 is a diagram showing an example of a map in which only a specific range is extracted. In Figs. 3 and 4, the crack propagation direction is from left to right in the figure. The crack propagation surface is shown as the boundary between the black area at the top of the figure and the gray area adjacent to the black area. In Figs. 3 and 4, twin boundaries are also shown in addition to the grain boundaries of crystal grains.

[0045] The predetermined number is set to 2 in order to extract the plastic region around the crack. For example, the length R of the plastic region from the crack propagation surface can be evaluated using the following formula: R = 1 / 2π × (K / σ)^2

[0046] Here, σ is the yield strength and K is the stress intensity factor. σ is known from the standard value, and K can be estimated from the results of a crack growth test.

[0047] The crack growth rate of the portion of the material to be evaluated is derived from the relationship between the crack length and the number of cycles. Then, by referring to the results of the crack growth test, the stress intensity factor can be estimated. By substituting the estimated K into the above formula, R was found to be approximately 40 μm. In the material used in this disclosure, the predetermined number was set to two because two crystal grains corresponded exactly.

[0048] The length of the specific range along the crack propagation direction or the direction perpendicular to the surface of the material may be 5 times or more the diameter of the crystal grains contained in the material, and the length of the specific range along the crack propagation direction or the direction perpendicular to the surface of the material may be 25 times or less the diameter of the crystal grains contained in the material.

[0049] The reason why the length of the specific range is set to at least five times the diameter of the crystal grains contained in the material is explained as follows: The index values ​​calculated for crystal grains (e.g., GOS, KAM) vary from crystal grain to crystal grain. Therefore, to reduce the impact of variation on the estimation, it is necessary to evaluate at least 10 crystal grains. Therefore, the length of the specific range is set to at least five times the diameter of the crystal grains contained in the material. In the material used in this disclosure, the crystal grains were approximately 10 to 20 μm in size, so if the measurement width was 100 μm, at least 10 crystal grains would be included when two crystal grains were extracted from the crack propagation surface.

[0050] The reason for setting the length of the specific range to 25 times or less the diameter of the crystal grains contained in the material is explained as follows: In the early stages of crack initiation, the crack grows relatively slowly. On the other hand, after the life ratio reaches 0.8, the crack grows rapidly, resulting in a large error in estimation. Assuming that the surface crack length at the initial stage of crack initiation is 1 mm and that the crack is semi-elliptical, in the material used in this disclosure, the initial stage of the crack can be considered to be when the crack grows 0.25 mm (250 μm) inward. Therefore, it is required that the measurement target be 250 μm or less. Since the crystal grains were approximately 10 to 20 μm in size, the length of the specific range is set to 25 times or less the diameter of the crystal grains contained in the material.

[0051] The index value generating unit 253 generates an index value based on the crystal orientation of the material in a specific range.

[0052] For example, the index value generating unit 253 may calculate, as an index value, a value indicating the average difference between the crystal orientation of adjacent pixels adjacent to the pixel and the crystal orientation of the pixel, which are in a crystal grain contained in the material and to which the pixel included in the map belongs. In other words, the index value generating unit 253 may calculate a grain orientation spread (GOS).

[0053] The index value generating unit 253 may also calculate an average value of the crystal orientations of pixels included in crystal grains contained in the material. The index value generating unit 253 may then calculate a value indicating the average of the differences of the crystal orientations of the pixels from the average value as the index value. In other words, the index value generating unit 253 may calculate KAM (Kernel Average Misorientation, local misorientation).

[0054] Alternatively, the index value generating unit 253 may calculate, as the index value, a value (GAM (Grain Average Misorientation)) obtained by averaging the orientation differences of adjacent pixels within a crystal grain. The index value generating unit 253 may calculate, as the index value, a contrast difference in an inverse pole figure orientation map based on the map. The index value generating unit 253 may calculate, as the index value, a contrast difference in the map.

[0055] Alternatively, the index value generator 253 may use, as the index value, an image quality (IQ (Image Quality) value) obtained during EBSD measurement, which is an index indicating the quality of a pattern other than the crystal orientation. Alternatively, the index value generator 253 may use, as the index value, a confidence index (CI (Confidence Index) value) obtained during EBSD measurement. Alternatively, the index value generator 253 may use, as the index value, a fit value obtained during EBSD measurement. The fit value has the meaning of both an IQ value and a CI value, and becomes a large value where the strain is large.

[0056] The load condition identifying unit 255 identifies a load condition based on the index values ​​in a specific range. For example, the load condition identifying unit 255 identifies a load condition based on a specific average value that is the average of the index values ​​in the specific range.

[0057] Specifically, the load condition identifying unit 255 reads the "relationship between the average value of the index values ​​and the load conditions" stored in the database 23. Then, the load condition identifying unit 255 identifies the "load condition" corresponding to the index value calculated by the index value generating unit 253 in the relationship between the average value of the index values ​​and the load conditions. In this way, the load condition identifying unit 255 estimates the "load condition" that led to the occurrence of a crack for a material whose "load condition" is unknown.

[0058] The life ratio estimation unit 257 refers to the relationship between the surface crack length and the life ratio under the load conditions, and estimates the remaining life of the material based on the surface crack length of the crack.

[0059] Specifically, the life ratio estimation unit 257 reads the "relationship between surface crack length and life ratio" stored in the database 23. At that time, the life ratio estimation unit 257 reads the "relationship between surface crack length and life ratio" corresponding to the "load condition" identified by the load condition identification unit 255. The life ratio estimation unit 257 also reads the surface crack length for a crack that has occurred in the material.

[0060] Then, the life ratio estimation unit 257 identifies the "life ratio" corresponding to the surface crack length in the relationship between the surface crack length and the life ratio. As a result, the life ratio estimation unit 257 estimates the "life ratio" for a material whose "life ratio" is unknown based on the "load condition" and the "surface crack length."

[0061] The remaining life estimated by the life ratio estimation unit 257 is displayed to the user via the display unit 29 .

[0062] [Processing Procedure of Remaining Life Estimation Device] FIG. 2 is a flowchart showing the processing procedure of the remaining life estimation device.

[0063] 2 is started, the "relationship between index value and load condition" and the "relationship between surface crack length and life ratio" are stored in the database 23. The "relationship between index value and load condition" and the "relationship between surface crack length and life ratio" stored in the database 23 are determined based on the results of a strain test previously performed on the material.

[0064] In step S101, the receiving unit 21 receives a map generated based on the backscatter diffraction pattern of electrons reflected from the material when an electron beam is irradiated onto the material to be subjected to remaining life estimation (a material whose "load conditions" and "remaining life" are unknown).

[0065] In step S103, the receiving unit 21 acquires the surface crack length for the crack that has occurred in the material that is the target of remaining life estimation. Instead of acquiring the surface crack length by the receiving unit 21, the surface crack length may be received via the operation unit 27.

[0066] In step S105, the specific range extraction unit 251 extracts, from the received map, the range of a predetermined number of crystal grains up to the propagation surface of the crack that has occurred in the material as a specific range.

[0067] In step S107, the index value generating unit 253 generates an index value based on the crystal orientation of the material in the specific range.

[0068] In step S109, the load condition specifying unit 255 specifies the load condition based on the index value in the specific range.

[0069] In step S111, the life ratio estimation unit 257 refers to the relationship between the surface crack length and the life ratio under the load conditions, and estimates the remaining life of the material based on the surface crack length of the crack.

[0070] [Effects of the embodiment] As described in detail above, the remaining life estimation method, remaining life estimation device, and remaining life estimation program according to the present disclosure acquire a map generated based on a backscatter diffraction pattern of electrons reflected from a material when the material is irradiated with an electron beam. From the map, a range of a predetermined number of crystal grains up to the propagation surface of a crack generated in the material is extracted as a specific range. An index value based on the crystal orientation of the material in the specific range is generated. Load conditions are identified based on the index value in the specific range. The remaining life of the material is estimated based on the surface crack length of the crack, with reference to the relationship between the surface crack length and the life ratio under the loading conditions.

[0071] This allows the tip position of a crack that has actually occurred in the material and the loading conditions related to the strain that caused the crack to be determined, making it possible to estimate the remaining life of the material. In particular, it is possible to estimate the loading conditions in the environment in which the material is used based on cracks that have actually occurred in materials used in products, etc. Furthermore, it is possible to estimate the remaining life. As a result, it is possible to gain insight into the environment in which the material is used. Furthermore, it can be used to estimate the remaining life of the product itself in which the material is used.

[0072] In the remaining life estimation method, remaining life estimation device, and remaining life estimation program according to the present disclosure, the loading conditions may be determined based on a specific average value, which is the average of index values ​​within a specific range. This reduces the influence of the variation on the estimation even if the index values ​​calculated for the crystal grains vary from grain to grain. As a result, the loading conditions and remaining life of the material can be estimated with high accuracy.

[0073] In the remaining life estimation method, remaining life estimation device, and remaining life estimation program according to the present disclosure, the predetermined number may be 2. The plastic zone around the crack can be extracted with high accuracy. Since the plastic zone around the crack can be focused on, the loading conditions that caused the crack to occur can be identified with high accuracy.

[0074] In the remaining life estimation method, remaining life estimation device, and remaining life estimation program according to the present disclosure, the length of the specific range along the crack propagation direction or the direction perpendicular to the surface of the material may be five times or more the diameter of a crystal grain contained in the material. This reduces the influence of variation on the estimation even if the index values ​​calculated for the crystal grains vary from one crystal grain to another.

[0075] In the remaining life estimation method, remaining life estimation device, and remaining life estimation program according to the present disclosure, the length of the specific range along the crack propagation direction or the direction perpendicular to the surface of the material may be 25 times or less the diameter of a crystal grain contained in the material. This makes it possible to capture the condition of crack initiation in the early stages. As a result, the loading conditions and remaining life of the material can be estimated with high accuracy.

[0076] The remaining life estimation method, remaining life estimation device, and remaining life estimation program according to the present disclosure may calculate an index value that indicates the average difference between the crystal orientation of adjacent pixels adjacent to a pixel and the crystal orientation of the pixel. Here, the adjacent pixels are within the crystal grains contained in the material to which the pixel included in the map belongs. This makes it possible to capture the distribution of crystal orientation differences on the scale of the crystal grain size. This allows the tip position of a crack that has actually occurred in the material and the loading conditions related to the strain that caused the crack to be determined, thereby estimating the remaining life of the material.

[0077] The remaining life estimation method, remaining life estimation device, and remaining life estimation program according to the present disclosure may calculate the average value of the crystal orientation of pixels contained in crystal grains contained in a material. Alternatively, a value indicating the average difference of the crystal orientation of the pixels from the average value may be calculated as an index value. This makes it possible to capture local changes in crystal orientation. This allows the tip position of a crack that has actually occurred in the material and the loading conditions related to the strain that caused the crack to be determined, thereby estimating the remaining life of the material.

[0078] Each of the functions described in the above embodiments may be implemented by one or more processing circuits, including programmed processors, electrical circuits, and even devices such as application specific integrated circuits (ASICs), or circuit components arranged to perform the described functions.

[0079] According to the present disclosure, it becomes possible to easily estimate the damage and remaining lifespan of materials, which can contribute to, for example, Goal 12 of the Sustainable Development Goals (SDGs) led by the United Nations, "Ensure sustainable consumption and production patterns."

[0080] Although several embodiments have been described, the embodiments can be modified or varied based on the above disclosure. All components of the above embodiments and all features described in the claims may be individually extracted and combined, unless they are mutually inconsistent.

[0081] The entire contents of Japanese Patent Application No. 2024-002016 (filing date: January 10, 2024) are incorporated herein by reference.

[0082] REFERENCE SIGNS LIST 10 Crystal orientation map acquisition device 20 Remaining life estimation device 21 Receiving unit 23 Database 25 Controller 251 Specific range extraction unit 253 Index value generation unit 255 Load condition identification unit 257 Life ratio estimation unit 27 Operation unit 29 Display unit

Claims

1. Obtain a map generated based on the pattern of backscattered diffraction by reflected electrons from the material when irradiating the material with an electron beam. Extract, from the map, a range of a predetermined number of crystal grains up to the crack propagation surface that has occurred in the material as a specific range. Generate an index value based on the crystal orientation of the material in the specific range. Specify the loading conditions based on the index value in the specific range. Estimate the remaining life of the material based on the surface crack length of the crack by referring to the relationship between the surface crack length and the life ratio under the loading conditions. A method for estimating the remaining life.

2. The method for estimating the remaining life according to claim 1, wherein the loading conditions are specified based on a specific average value that is the average of the index values in the specific range.

3. The method for estimating the remaining life according to claim 1, wherein the predetermined number is two.

4. The method for estimating the remaining life according to claim 1, wherein the length of the specific range along the crack propagation direction or the direction perpendicular to the surface of the material is 5 times or more the diameter of the crystal grains contained in the material.

5. The method for estimating the remaining life according to claim 1, wherein the length of the specific range along the crack propagation direction or the direction perpendicular to the surface of the material is 25 times or less the diameter of the crystal grains contained in the material.

6. The method for estimating the remaining life according to any one of claims 1 to 5, wherein a value indicating the average of the difference between the crystal orientation in an adjacent pixel adjacent to the pixel and the crystal orientation in the pixel, which belongs to the pixel included in the map and is within the crystal grain contained in the material, is calculated as the index value.

7. The method for estimating the remaining life according to any one of claims 1 to 5, wherein an average value of the crystal orientation in the pixel contained in the crystal grain included in the material is calculated, and a value indicating the average of the difference between the crystal orientation in the pixel and the average value is calculated as the index value.

8. A remaining life estimation device comprising: an acquisition unit that acquires a map generated based on a backscattered diffraction pattern of reflected electrons from the material when the material is irradiated with an electron beam; and a controller, wherein the controller extracts, as a specific range, a range of a predetermined number of crystal grains up to the crack propagation surface generated in the material from the map, generates an index value based on the crystal orientation of the material in the specific range, specifies a load condition based on the index value in the specific range, and estimates the remaining life of the material based on the surface crack length of the crack with reference to the relationship between the surface crack length and the life ratio under the load condition.

9. A remaining life estimation program for processing a map generated based on a backscattered diffraction pattern of reflected electrons from the material when the material is irradiated with an electron beam, which causes a computer to execute steps of extracting, as a specific range, a range of a predetermined number of crystal grains up to the crack propagation surface generated in the material from the map, generating an index value based on the crystal orientation of the material in the specific range, specifying a load condition based on the index value in the specific range, and estimating the remaining life of the material based on the surface crack length of the crack with reference to the relationship between the surface crack length and the life ratio under the load condition.