Apparatus for evaluating residual stress in welded structures, method for evaluating residual stress, and program for evaluating residual stress

Abstract

The system must be able to analyze and evaluate residual stress in the welded structure being evaluated with high accuracy. [Solution] The system comprises: a thermal analysis unit 12 that performs thermal analysis based on an analysis mesh based on the shape of the welded structure to be evaluated and the thermophysical properties and welding conditions of the welded structure to be evaluated to determine the temperature distribution of the welded structure to be evaluated; a stress-strain characteristic conversion unit 15 that converts the reference stress-strain characteristic σs of the weld in a typical welded structure from the material properties DB 14 according to the state of the weld in the welded structure to be evaluated to determine the target stress-strain characteristic σa of the weld in the welded structure to be evaluated; and a stress analysis unit 17 that performs analysis based on the temperature distribution from the thermal analysis unit 12, the analysis mesh, the stress-strain characteristic of the base material in a typical welded structure from the material properties DB 14, and the target stress-strain characteristic σa from the stress-strain characteristic conversion unit 15 to determine the stress distribution of the welded structure to be evaluated.

Description

[Technical Field]

[0001] Embodiments of the present invention relate to a residual stress evaluation apparatus for welded structures, a residual stress evaluation method for welded structures, and a residual stress evaluation program for welded structures. [Background technology]

[0002] Residual stresses in welded structures can cause fatigue cracks, stress corrosion cracking, and creep damage. Therefore, understanding the residual stress distribution within the material of welded structures remains a crucial issue for evaluating the lifespan and reliability of equipment. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2009-250829 [Patent Document 2] Japanese Patent Publication No. 2009-250828 [Patent Document 3] Japanese Patent Publication No. 2009-128085 [Patent Document 4] Japanese Patent Publication No. 2009-48361 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] The residual stress of a welded structure has been evaluated by thermo-elastoplastic analysis using the finite element method (for example, Patent Documents 1 to 4). The main input conditions for the analysis in this evaluation are the welding conditions and the non-linear material properties (stress-strain properties). In order to perform a highly accurate evaluation, it is particularly important to improve the stress-strain properties. Therefore, it is desirable that the stress-strain properties reflect the metal structure and strain state of the welded part in the welded structure to be evaluated. However, in the conventional evaluation methods (evaluation methods that use the same stress-strain properties regardless of the welding conditions and joint shape), the metal structure and strain state of the welded part in the welded structure to be evaluated have not been sufficiently reflected in the stress-strain properties.

[0005] An embodiment of the present invention has been made in consideration of the above circumstances, and an object thereof is to provide a residual stress evaluation device for a welded structure, a residual stress evaluation method for a welded structure, and a residual stress evaluation program for a welded structure that can accurately analyze and evaluate the residual stress in the welded structure to be evaluated.

Means for Solving the Problems

[0006] The residual stress evaluation apparatus for a welded structure according to an embodiment of the present invention includes a thermal analysis condition input unit for inputting an analysis mesh created based on the shape of the welded structure to be evaluated, the thermal physical properties of the welded structure to be evaluated, and welding conditions; a thermal analysis unit that performs thermal analysis based on the information input from the thermal analysis condition input unit and obtains the temperature distribution of the welded structure to be evaluated; a material property DB in which typical information on general welded structures is accumulated; a stress-strain property conversion unit that converts the reference stress-strain property of the welded part in a general welded structure from the material property DB according to the state of the welded part in the welded structure to be evaluated and obtains the target stress-strain property of the welded part in the welded structure to be evaluated; a stress analysis condition input unit for inputting the temperature distribution from the thermal analysis unit, the analysis mesh, the stress-strain property of the base material in a general welded structure from the material property DB, and the target stress-strain property from the stress-strain property conversion unit; and a stress analysis unit that performs stress analysis based on the information input from the stress analysis condition input unit and obtains the stress distribution of the welded structure to be evaluated, and is characterized by being configured to have these components.

[0007] The residual stress evaluation method for a welded structure in an embodiment of the present invention comprises the steps of: inputting an analysis mesh created based on the shape of the welded structure to be evaluated, the thermal properties of the welded structure to be evaluated, and the welding conditions into a thermal analysis condition input unit; performing a thermal analysis based on the information input from the thermal analysis condition input unit to determine the temperature distribution of the welded structure to be evaluated; and converting a stress-strain characteristic conversion unit to the welded structure to be evaluated by converting the standard stress-strain characteristics of a weld in a typical welded structure from a material properties DB in which representative information on typical welded structures is stored. The method is characterized by sequentially performing the following steps: determining the target stress-strain characteristics of the welded part in the welded structure to be evaluated by converting according to the state of the welded part; inputting the temperature distribution from the thermal analysis unit, the analysis mesh, the stress-strain characteristics of the base material in a typical welded structure from the material properties DB, and the target stress-strain characteristics from the stress-strain characteristic conversion unit into the stress analysis condition input unit; and having the stress analysis unit perform a stress analysis based on the information input from the stress analysis condition input unit to determine the stress distribution of the welded structure to be evaluated.

[0008] The residual stress evaluation program for a welded structure in an embodiment of the present invention is characterized by sequentially executing the following steps: a thermal analysis condition input step in which an analysis mesh created based on the shape of the welded structure to be evaluated and the thermophysical properties and welding conditions of the welded structure to be evaluated are input to a computer; a thermal analysis step in which a thermal analysis is performed based on the information input from the thermal analysis condition input step to determine the temperature distribution of the welded structure to be evaluated; a stress-strain characteristic conversion step in which the reference stress-strain characteristics of the weld in a general welded structure from a material properties DB in which representative information on general welded structures is accumulated is converted according to the state of the weld in the welded structure to be evaluated to determine the target stress-strain characteristics of the weld in the welded structure to be evaluated; a stress analysis condition input step in which the temperature distribution from the thermal analysis step, the analysis mesh, the stress-strain characteristics of the base material in a general welded structure from the material properties DB, and the target stress-strain characteristics from the stress-strain characteristic conversion step are input to a computer; and a stress analysis step in which a stress analysis is performed based on the information input from the stress analysis condition input step to determine the stress distribution of the welded structure to be evaluated. [Effects of the Invention]

[0009] According to embodiments of the present invention, residual stress in a welded structure to be evaluated can be analyzed and evaluated with high accuracy. [Brief explanation of the drawing]

[0010] [Figure 1] A block diagram showing the configuration of a residual stress evaluation device for welded structures according to the first embodiment. [Figure 2] A block diagram showing the configuration of the stress-strain characteristic conversion section in Figure 1. [Figure 3] Figures 1 and 2 illustrate the concept of material properties DB, where (A) is the stress-strain characteristic diagram of the weld and base material in a typical welded structure, (B) is the metallographic diagram of the weld, and (C) is the intragranular strain distribution diagram of the weld. [Figure 4]Figure 2 shows the concept of the stress-strain characteristic calculation unit, where (A) is a graph explaining the calculation of the target stress-strain characteristics of the welded joint in the welded structure under evaluation, (B) is a graph showing the calculation of the coefficient α1 that reflects the difference in grain size, and (C) is a graph explaining the calculation of the coefficient α2 that corrects the intragranular strain value. [Figure 5] The second embodiment shows the concept of the stress-strain characteristic conversion unit in the residual stress evaluation device for welded structures, where (A) is a graph explaining the calculation of the target stress-strain characteristics of the welded part in the welded structure to be evaluated, and (B) is a graph explaining the calculation of the coefficient α3 that reflects the strain removal heat treatment. [Figure 6] The test specimen of the welded structure to be evaluated is shown, with (A) being a perspective view and (B) being a cross-sectional view along the VIB-VIB line in Figure 6(A). [Figure 7] This figure shows the analytical values ​​of residual stress obtained by the residual stress evaluation device for a welded structure according to the second embodiment, compared with the measured values ​​of residual stress obtained by a welding experiment using the test specimen shown in Figure 6. [Modes for carrying out the invention]

[0011] Hereinafter, embodiments for carrying out the present invention will be described based on the drawings.

[0012] [A] First Embodiment (Figures 1-4) Figure 1 is a block diagram showing the configuration of a residual stress evaluation device for welded structures according to the first embodiment. The residual stress evaluation device 10 for welded structures shown in Figure 1 analyzes and evaluates the residual stress generated in a welded structure, and is composed of a thermal analysis condition input unit 11, a thermal analysis unit 12, a temperature distribution output unit 13, a material properties DB 14, a stress-strain characteristic conversion unit 15, a stress analysis condition input unit 16, a stress analysis unit 17, and a stress distribution output unit 18.

[0013] The thermal analysis condition input unit 11 inputs the analysis mesh created based on the shape of the welded structure to be evaluated, the thermal properties of the welded structure to be evaluated, and the welding conditions to the thermal analysis unit 12. Here, the thermal properties are the specific heat, thermal conductivity, and density of the weld and base material in the welded structure to be evaluated. The welding conditions are the welding current, welding voltage, welding speed, and welding sequence.

[0014] The thermal analysis unit 12 performs a thermal analysis using the finite element method based on the information input from the thermal analysis condition input unit 11 to determine the temperature distribution of the welded structure to be evaluated. Depending on the welding method, the heat source model used in this thermal analysis can be selected from a homogeneous transfer heat source model, a Goldak transfer heat source model, or an instantaneous transfer heat source model, etc.

[0015] The temperature distribution output unit 13 outputs the temperature distribution of the welded structure to be evaluated, obtained from the thermal analysis unit 12, and transmits it to the stress analysis unit 17 via the stress analysis condition input unit 16.

[0016] Material Properties DB14 is a database (DB) that stores representative information about typical welded structures. In other words, as shown in Figure 3, Material Properties DB14 stores the stress-strain characteristics of the weld (reference stress-strain characteristics σs) of a typical welded structure, the stress-strain characteristics σss of the base material of a typical welded structure, the metallographic diagram M of the weld, and the intragranular strain distribution N of the weld. From the metallographic diagram M of the weld described above, the grain size of this weld (reference grain size d) can be determined. DB ) is required, and this standard particle size d DB This information is stored in the material properties database DB14.

[0017] In addition, the in-grain strain value in the in-grain strain distribution N of the welded part can be expressed using the KAM (Kernel Average Misorientation) value obtained from SEM-EBSD (Field Emission Scanning Electron Microscope). In this KAM value, the evaluation of sub-grain boundaries of 5 degrees or less is important, and the average value of the KAM count of 5 degrees or less, or the KAM count of a specific angle, or an index of grain boundary length calculated based on the KAM count is used as the KAM value. Therefore, in the material property DB14, the in-grain strain value (reference in-grain strain value KAM DB ) of the welded part obtained from the in-grain strain distribution N of the welded part in a general welded structure is accumulated.

[0018] The stress-strain characteristic conversion unit 15 converts the reference stress-strain characteristic σs of the welded part in a general welded structure from the material property DB14 according to the state of the welded part in the welded structure to be evaluated (the target grain size d TT and the target in-grain strain value KAM TARGET ) shown in FIG. 4, and obtains the strain characteristic (target stress-strain characteristic σa shown in FIG. 4(A)) of the welded part in the welded structure to be evaluated. As shown in FIG. 2, this stress-strain characteristic conversion unit 15 is configured to include a stress-strain characteristic calculation unit 20 and an output unit 21.

[0019] The above target stress-strain characteristic σa will be input to the stress analysis unit 17 via the stress analysis condition input unit 16 shown in FIG. 1. As the stress-strain characteristic input to the stress analysis unit 17, the stress-strain characteristic having a grain size equivalent to that of the welded part in the welded structure to be evaluated and an in-grain strain value close to the strain-free state immediately after melting is most suitable.

[0020] As shown in FIG. 2, the stress-strain characteristic calculation unit 20 includes the reference stress-strain characteristic σs of the welded part in a general welded structure accumulated in the material property DB14, the reference grain size d DB and the reference in-grain strain value KAM DB , and the target grain size d TT and the target in-grain strain value KAM TARGETBased on this, the target stress-strain characteristics σa of the welded joint in the welded structure under evaluation (Figure 4(A)) are calculated. The output unit 21 outputs the target stress-strain characteristics σa obtained from the stress-strain characteristics calculation unit 20 to the stress analysis condition input unit 16.

[0021] The stress-strain characteristic calculation unit 20 will be further explained with reference to Figure 4. The stress-strain characteristic calculation unit 20 calculates the standard stress-strain characteristics σs and standard grain size d of a welded joint in a typical welded structure, which are stored in the material properties DB14. DB and standard grain strain value KAM DB And, the target particle size d of the welded part in the welded structure being evaluated TT (Figure 4(B)) and target intragranular strain value KAM TARGET Based on (Figure 4(C)), first, a coefficient α1 is calculated that reflects the difference in grain size in the welds of a typical welded structure and the welded structure under evaluation. In other words, the stress-strain characteristic calculation unit 20 calculates the coefficient α1 based on the reference grain size d DB and target particle size d TT The yield strength σ required from each of these is Y,DB and yield strength σ Y、TT Using the ratio, it is calculated by equation (1). α1 = σ Y、TT / σ Y,DB ………(1)

[0022] Next, the stress-strain characteristic calculation unit 20 calculates a coefficient α2 to correct the intragranular strain values ​​in the welds of both the general welded structure and the welded structure under evaluation, using the reference intragranular strain value KAM. DB and target intragranular strain value KAM TARGET The yield strength σ required from each of these is Y、DB and yield strength σ Y、TARGET Using the ratio, the calculation is performed using equation (2). α² = σ Y、TARGET / σ Y、DB ………(2)

[0023] Next, the stress-strain characteristic calculation unit 20 constructs a function f(α1, α2) from at least one of the coefficients α1 and α2 described above. Here, the reference stress-strain characteristic σs from the material properties DB14 is defined as having an initial yield strength of σ0, a work hardening coefficient of H, and a plastic strain of ε p Then it can be expressed by equation (3). In this equation (3), Hε p This represents the work hardening increment. σs = σ0 + Hε p …………(3)

[0024] The stress-strain characteristic calculation unit 20 calculates the above function f(α1, α2) using the initial yield strength σ0 of the reference stress-strain characteristic σs and the work hardening increment Hε p By multiplying each of these by the values, the target stress-strain characteristic σa of the welded joint in the welded structure under evaluation is calculated, as shown in equation (4). σa = σ0f(α1, α2) + Hε p f(α1, α2) ………(4)

[0025] The above target particle size d TT This is obtained from the metallographic diagram K of the welded joint of the welded structure being evaluated. Furthermore, the relationship between grain size and yield strength is evaluated based on, but is not limited to, the Hall-Petch rule. Also, the relationship between intragranular strain value and yield strength is evaluated based on an experimentally determined empirical rule. Furthermore, the target intragranular strain value KAM is used. TARGET This represents a state close to a strain-free state, which can be achieved through strain-relieving heat treatment. Note that while the intragranular strain value is expressed by the KAM value, it is not limited to this.

[0026] The stress analysis condition input unit 16 shown in Figure 1 inputs the following to the stress analysis unit 17: the temperature distribution of the welded structure to be evaluated, calculated by the thermal analysis unit 12 and output from the temperature distribution output unit 13; the analysis mesh created based on the shape of the welded structure to be evaluated; the stress-strain characteristics σss of the base material in a typical welded structure obtained from the material properties DB 14; and the target stress-strain characteristics σa of the weld in the welded structure to be evaluated, calculated by the stress-strain characteristic calculation unit 20 of the stress-strain characteristic conversion unit 15.

[0027] The stress analysis unit 17 performs thermoelastoplastic analysis using the finite element method based on the information input from the stress analysis condition input unit 16 to determine the stress distribution in the welded structure under evaluation. The stress distribution determined by this stress analysis unit 17 is output by the stress distribution output unit 18.

[0028] Next, the operation of the residual stress evaluation device 10 for welded structures, configured as described above, will be explained. First, the thermal analysis condition input unit 11 performs a thermal analysis condition input step (S1) in which it inputs the analysis mesh created based on the shape of the welded structure to be evaluated, the thermal properties of the welded structure to be evaluated, and the welding conditions to the thermal analysis unit 12. Next, the thermal analysis unit 12 performs a thermal analysis step (S2) in which it performs a thermal analysis using the finite element method based on the information input from the thermal analysis condition input unit 11 to determine the temperature distribution of the welded structure to be evaluated. Finally, the temperature distribution output unit 13 performs a temperature distribution output step (S3) in which it outputs this temperature distribution to the stress analysis condition input unit 16.

[0029] Next, the stress-strain characteristic conversion unit 15 performs a stress-strain characteristic conversion step (S4) to determine the target stress-strain characteristic σa of the weld in the weld in the weld to be evaluated, according to the state of the weld in the weld in the weld to be evaluated, using the standard stress-strain characteristic σs of the weld in a typical weld in a general welded structure, which is stored in the material characteristics DB 14, which contains representative information on general welded structures.

[0030] Next, the stress analysis condition input step is performed in which the stress analysis condition input unit 16 inputs the temperature distribution from the thermal analysis unit 12, the same analysis mesh input to the thermal analysis condition input unit 11, the stress-strain characteristics σss of the base material in a typical welded structure from the material properties DB 14, and the target stress-strain characteristics σa calculated by the stress-strain characteristic calculation unit 20 of the stress-strain characteristic conversion unit 15 to the stress analysis unit 17 (S5).

[0031] Next, the stress analysis unit 17 performs a stress analysis using the finite element method based on the information input from the stress analysis condition input unit 16, and performs a stress analysis step to determine the stress distribution of the welded structure to be evaluated (S6). After that, the stress distribution output unit 18 outputs the stress distribution from the stress analysis unit 17 in a stress distribution output step (S7).

[0032] As configured as described above, the first embodiment provides the following effect (1). (1) The stress-strain characteristic conversion unit 15 converts the standard stress-strain characteristic σs of a weld in a typical welded structure from the material characteristics DB14 to the state of the weld in the welded structure to be evaluated (target particle size d TT and target intragranular strain value KAM TARGET The system converts the data according to the specified parameters to determine the target stress-strain characteristic σa of the welded joint in the welded structure under evaluation. Based on this target stress-strain characteristic σa, the stress analysis unit 17 analyzes the stress distribution of the welded structure under evaluation. As a result, the residual stress of the welded structure under evaluation can be analyzed and evaluated with high accuracy.

[0033] [B] Second embodiment (Figures 1, 5-7) Figure 5 shows a conceptual diagram of the stress-strain characteristic conversion unit in the residual stress evaluation device for welded structures according to the second embodiment. In this second embodiment, parts that are the same as in the first embodiment are denoted by the same reference numerals as in the first embodiment, and their explanation is simplified or omitted.

[0034] The difference between the residual stress evaluation device 25 (Figure 1) for welded structures in this second embodiment and the first embodiment is that the stress-strain characteristic conversion unit 26 (Figure 5) converts the reference stress-strain characteristic σs of a weld in a typical welded structure from the material characteristics DB14 to the state of the weld in the weld to be evaluated (the intragranular strain value KAM after heat treatment, described later). HT The point is to convert the stress-strain characteristics (target stress-strain characteristics σb) of the welded joint in the welded structure being evaluated according to the following. This stress-strain characteristics conversion unit 26 is configured to include a strain removal heat treatment influence reflection unit 27 and an output unit 28.

[0035] The strain removal heat treatment influence reflection unit 27 reflects the influence of strain removal heat treatment on the reference stress-strain characteristics σs of welds in general welded structures stored in the material properties DB 14, and calculates the target stress-strain characteristics σb of the weld in the welded structure under evaluation. The output unit 28 outputs the target stress-strain characteristics σb obtained from the strain removal heat treatment influence reflection unit 27 to the stress analysis condition input unit 16.

[0036] Further explanation will be given regarding the strain removal heat treatment effect reflection section 27. The strain removal heat treatment effect reflection section 27 reflects the standard stress-strain characteristics σs and standard intragranular strain values ​​KAM of the welded joint in a typical welded structure, which are stored in the material properties DB14. DB The intragranular strain value (intragranular strain value after heat treatment KAM) obtained by applying strain-relieving heat treatment to the welded portion of the welded structure being evaluated. HT Based on the above, first, a coefficient α3 that reflects the strain removal heat treatment is calculated. In other words, the strain removal heat treatment influence reflection section 27 uses the coefficient α3 to calculate the standard grain strain value KAM. DB and the intragranular strain value KAM after heat treatment HT The yield strength σ required from each of these is Y、DB and yield strength σ Y、HT Using the ratio, it is calculated by equation (5). α3 = σ Y、HT / σ Y、DB …………(5)

[0037] Next, the strain relief heat treatment influence reflection section 27 constructs a function f(α3) from the coefficient α3, and this function f(α3) is obtained by comparing the initial yield strength σ0 and the work hardening increment Hε in the reference stress-strain characteristic σs from the material property DB14 expressed by the aforementioned equation (3). p By multiplying each of these by the values, the stress-strain characteristics of the welded joint in the welded structure under evaluation (target stress-strain characteristics σb) are calculated, as shown in equation (6). σb = σ0f(α3) + Hε p f(α3)…………(6)

[0038] Here, the intragranular strain value KAM after heat treatment HTAs described above, this is the intragranular strain value obtained by applying strain-relieving heat treatment to the welded portion of the welded structure being evaluated. Specifically, it is the target intragranular strain value KAM, which represents a state close to a strain-free state achieved by the strain-relieving heat treatment. TARGET This is the KAM value of the neighboring area.

[0039] Next, the residual stress analysis values ​​obtained by the residual stress evaluation device 25 of the welded structure of the second embodiment configured as described above are compared with the measured residual stress values ​​obtained by welding experiments using the test specimen shown in Figure 6.

[0040] Figure 6 shows the test specimen 30 of the welded structure to be evaluated. The dimensions of this test specimen 30 are 200 mm × 200 mm × 35 mm, the base material is a nickel alloy material (NCF600 - JIS standard), and the weld metal material (welding rod) is WEL Auto TIG82. The welding method used in the welding experiment was TIG welding, with a heat input of 1950 J / mm and a welding speed of 1.67 mm / sec. A total of 12 passes of welding were performed in a groove 31 with a depth of 20 mm in the test specimen 30. In Figure 6, reference numeral 32 indicates the weld line, and reference numeral 33 indicates the weld formed by the welding experiment.

[0041] Residual stress was evaluated through welding experiments and analysis. In the welding experiment, the stress in the depth direction of the weld 33 at the longitudinal center of the weld line 32 was measured using the DHD (Deep Hole Drilling) method. In the analysis, two types of analysis were performed: a conventional analysis (Analysis Ls) using the reference stress-strain characteristic σs of the weld accumulated in the material properties DB14 as the stress-strain characteristic of the weld, and an analysis (Analysis Lb) using the target stress-strain characteristic σb of the weld converted by the strain-removal heat treatment influence reflection section 27 of the stress-strain characteristic conversion section 26 shown in Figure 5. In Analysis Lb, the heat treatment conditions for strain removal were 1000°C for 1 hour.

[0042] Figure 7 shows the results of comparing stress values. The stress values ​​near the surface of the welded structure were compared at a position 6 mm from the surface, and the stress values ​​inside the welded structure were also compared at a position 20 mm from the surface. The stress value of the conventional analysis Ls was up to approximately 200 MPa higher than the stress value obtained in the welding experiment in the X direction (weld line direction 32) at a position 6 mm from the surface. On the other hand, the difference between the stress value of analysis Lb and the stress value obtained in the welding experiment was significantly reduced, and it was possible to evaluate a value equivalent to the stress value obtained in the welding experiment. The stress values ​​of analysis Lb also showed a tendency to be close to the stress values ​​obtained in the welding experiment for the stress values ​​in the Y direction perpendicular to the X direction and for the stress value at a position 20 mm from the surface.

[0043] As configured as described above, the second embodiment provides the following effect (2). (2) The stress-strain characteristic conversion unit 26 converts the standard stress-strain characteristic σs of a weld in a typical welded structure from the material characteristics DB14 to the state of the weld in the weld to be evaluated (intragranular strain value KAM after heat treatment) HT The system converts the data according to the specified parameters to determine the target stress-strain characteristic σb of the welded joint in the welded structure under evaluation. Based on this target stress-strain characteristic σb, the stress analysis unit 17 analyzes the stress distribution of the welded structure under evaluation. As a result, the residual stress of the welded structure under evaluation can be analyzed and evaluated with high accuracy.

[0044] As described above, the residual stress evaluation devices 10 and 25 for welded structures are equipped with a control device that highly integrates 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 display, an input device such as a mouse or keyboard, and a communication interface, and can be realized with a hardware configuration using a normal computer. Therefore, the components of the residual stress evaluation devices 10 and 25 can also be realized with a computer processor and can be operated by a residual stress evaluation program.

[0045] The above-mentioned residual stress evaluation program is provided pre-installed on ROM or the like. Alternatively, this program may be provided as an installable or executable file stored on a computer-readable storage medium such as a CD-ROM, CD-R, memory card, DVD, or flexible disk (FD).

[0046] Furthermore, the residual stress evaluation program may be stored on a computer connected to a network such as the Internet and provided for download via the network. In addition, the residual stress evaluation devices 10 and 25 for welded structures can be configured by connecting and combining separate modules, each independently performing the function of its constituent elements, via a network or dedicated line.

[0047] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be carried out in various other forms, and various omissions, substitutions, modifications, and combinations can be made without departing from the spirit of the invention, and such substitutions, modifications, and combinations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Explanation of Symbols]

[0048] 10...Residual stress evaluation device, 11...Thermal analysis condition input unit, 12...Thermal analysis unit, 14...Material property database (DB), 15...Stress-strain characteristic conversion unit, 16...Stress analysis condition input unit, 17...Stress analysis unit, 20...Stress-strain characteristic calculation unit, 25...Residual stress evaluation device, 26...Stress-strain characteristic conversion unit, 27...Strain removal heat treatment effect reflection unit, σs...Reference stress-strain characteristic, σss...Stress-strain characteristic, σa...Target stress-strain characteristic, σb...Target stress-strain characteristic, d DB ...Reference particle size, d TT …Target particle size, KAM DB ...Reference intragranular strain value, KAM TARGET ...Target intragranular strain value, KAM HT ...Intragranular strain value after heat treatment, α1, α2, α3... coefficients, σ Y,DB ...Yield strength, σ Y、TT ...Yield strength, σ Y、TARGET ...Yield strength, σ Y,HT ...Yield strength, f(α1, α2), f(α3)...function.

Claims

1. A thermal analysis condition input unit for inputting an analysis mesh created based on the shape of the welded structure to be evaluated, the thermophysical properties of the welded structure to be evaluated, and the welding conditions, A thermal analysis unit performs thermal analysis based on the information input from the thermal analysis condition input unit and determines the temperature distribution of the welded structure to be evaluated, A material properties database containing representative information on typical welded structures, A stress-strain characteristic conversion unit converts the standard stress-strain characteristics of a weld in a typical welded structure from the material characteristics DB according to the state of the weld in the welded structure to be evaluated, in order to determine the target stress-strain characteristics of the weld in the welded structure to be evaluated. A stress analysis condition input unit for inputting the temperature distribution from the thermal analysis unit, the analysis mesh, the stress-strain characteristics of the base material in a typical welded structure from the material properties DB, and the target stress-strain characteristics from the stress-strain characteristic conversion unit, A residual stress evaluation device for a welded structure, characterized by comprising: a stress analysis unit that performs stress analysis based on information input from the stress analysis condition input unit and determines the stress distribution of the welded structure to be evaluated.

2. The residual stress evaluation apparatus for a welded structure according to claim 1, characterized in that the stress-strain characteristic conversion unit comprises a stress-strain characteristic calculation unit that calculates the target stress-strain characteristics of the weld in the weld in the weld to be evaluated based on the standard stress-strain characteristics, standard particle size, and standard intragranular strain value of the weld in a general welded structure stored in a material characteristics DB, and the target particle size and target intragranular strain value of the weld in the weld to be evaluated. demand

3. The stress-strain characteristic calculation unit is configured to calculate the target stress-strain characteristic of the weld in

4. The residual stress evaluation device for a welded structure according to claim 1, characterized in that the stress-strain characteristic conversion unit is configured to include a strain-removal heat treatment influence reflection unit that reflects the influence of strain-removal heat treatment on the reference stress-strain characteristics of a weld in a typical welded structure stored in a material characteristics DB, and calculates the target stress-strain characteristics of the weld in the weld to be evaluated.

5. The strain-relieving heat treatment influence reflection unit is configured to calculate a coefficient α3 that reflects the strain-relieving heat treatment based on the reference stress-strain characteristics and reference intragranular strain values ​​of a weld in a typical welded structure accumulated in a material properties DB, and the intragranular strain values ​​after heat treatment obtained by applying strain-relieving heat treatment to the weld in the weld to be evaluated. This coefficient α3 is calculated from the ratio of yield strength obtained from the reference intragranular strain value and the intragranular strain value after heat treatment, respectively, and the function composed of the coefficient α3 is multiplied by the initial yield strength and the work hardening increment of the reference stress-strain characteristics, respectively, to calculate the target stress-strain characteristics of the weld in the weld in the weld to be evaluated, as described in claim 4.

6. The thermal analysis condition input unit inputs an analysis mesh created based on the shape of the welded structure to be evaluated, the thermal properties of the welded structure to be evaluated, and the welding conditions. The thermal analysis unit performs a thermal analysis based on the information input from the thermal analysis condition input unit to determine the temperature distribution of the welded structure to be evaluated. The stress-strain characteristic conversion unit converts the standard stress-strain characteristics of a weld in a typical welded structure, taken from a material properties database containing representative information on typical welded structures, according to the state of the weld in the weld to be evaluated, in order to determine the target stress-strain characteristics of the weld in the weld to be evaluated. The stress analysis condition input unit inputs the temperature distribution from the thermal analysis unit, the analysis mesh, the stress-strain characteristics of the base material in a typical welded structure from the material properties DB, and the target stress-strain characteristics from the stress-strain characteristic conversion unit. A method for evaluating residual stress in a welded structure, characterized by sequentially performing the following steps: a stress analysis unit performs a stress analysis based on information input from the stress analysis condition input unit to determine the stress distribution of the welded structure to be evaluated; and

7. On the computer, A thermal analysis condition input step involves inputting an analysis mesh created based on the shape of the welded structure to be evaluated, the thermophysical properties of the welded structure to be evaluated, and the welding conditions. A thermal analysis step which involves performing a thermal analysis based on the information input from the thermal analysis condition input step to determine the temperature distribution of the welded structure to be evaluated, A stress-strain characteristic conversion step involves converting the standard stress-strain characteristics of a weld in a typical welded structure, obtained from a material properties database containing representative information on typical welded structures, according to the state of the weld in the weld to be evaluated, in order to determine the target stress-strain characteristics of the weld in the weld to be evaluated. A stress analysis condition input step inputs the temperature distribution from the thermal analysis step, the analysis mesh, the stress-strain characteristics of the base material in a typical welded structure from the material properties DB, and the target stress-strain characteristics from the stress-strain characteristic conversion step. A residual stress evaluation program for a welded structure, characterized by sequentially executing a stress analysis step that performs a stress analysis based on the information input from the stress analysis condition input step and determines the stress distribution of the welded structure to be evaluated.

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