Method for evaluating stress applied to weld zone

Abstract

To estimate stress on a toe.SOLUTION: A method for evaluating stress on a weld zone, comprises: a step of generating a finite element model FM of a structure including a weld zone 50 including a non-finished toe t, in such a manner that the finite element model FM includes a first element m1 extending along a surface 11 of a base material 10 from the toe t, and a second element m2 extending along a surface B1 of a bead B from the toe t; a step of performing finite element analysis using the finite element model FM; a step of selecting first stress from stress on nodes other than the toe t in the first element m1; a step of selecting second stress from stress on nodes other than the toe t in the second element m2; and a step of selecting stress having a larger absolute value, from the first stress and second stress, as an index for estimating stress in the toe t.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present disclosure relates to a method for assessing stresses on a weld. [Background technology]

[0002] Concerning methods for evaluating stress on welds, JIS E4208-1 specifies a static load test method used to confirm the strength of railroad vehicle components such as bogie frames. This method uses a single-axis strain gauge with a length of 5 mm. When attaching a strain gauge to a portion with a small radius of curvature, such as the toe of a weld bead, the toe is finished into an arc shape with a radius of about 3 mm. The strain gauge is attached to the toe so that it straddles the base material and the bead, and 1 / 2 to 2 / 3 of the gauge length covers the base material.

[0003] Patent Document 1 proposes an alternative to the above method. This method includes a first step and a second step. In the first step, a bogie frame including a weld is used for a static load test. In this method, the toe of the weld is unfinished. A strain gauge is attached to the base material. Specifically, the strain gauge is attached to the base material so that the gauge end close to the toe is located in the vicinity of the toe. In the first step, a static load test is performed using such a bogie frame. In the second step, a test piece is used for a fatigue test. The test piece includes an unfinished weld similar to the weld of the bogie frame. In addition, a strain gauge is attached to the test piece in a manner similar to that used for the bogie frame. The stress measured in the first step is compared with the fatigue limit measured in the second step. In addition, Patent Document 1 proposes that, instead of using a bogie frame to perform a static load test in the first step, a finite element model of the bogie frame is used to perform a static load test by finite element analysis. In the finite element model, stresses are calculated in regions similar to the strain gauges affixed to the bogie frame, i.e., in the base material. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-84522 Summary of the Invention [Problem to be solved by the invention]

[0005] When creating finite element models that include unfinished welds, the toes are defined as the lines where the planes meet. Such lines can be stress singularities. Therefore, it is difficult to accurately calculate the stresses at the toes.

[0006] The present disclosure aims to provide a method for assessing stresses in a weld that can estimate the toe stress. [Means for solving the problem]

[0007] A method for evaluating stress on a weld according to one embodiment of the present disclosure includes creating a finite element model of a structure having a weld including an unfinished toe, the finite element model including a first element extending from the toe along a surface of the base metal and a second element extending from the toe along a surface of the bead, performing finite element analysis using the finite element model, selecting a first stress from among stresses at nodes other than the toe in the first element, selecting a second stress from among stresses at nodes other than the toe in the second element, and selecting a stress having a larger absolute value from the first stress and the second stress as an index for estimating the stress at the toe.

[0008] Selecting the first stress may include selecting a stress at a node on the first element adjacent to the toe, and selecting the second stress may include selecting a stress at a node on the second element adjacent to the toe.

[0009] Creating a finite element model of the structure may include creating each of the first element and the second element such that a distance between a node adjacent to the toe of the first element and a node adjacent to the toe of the second element corresponds to a gauge length of a uniaxial strain gauge used in the static load test method specified in JIS E4208-1.

[0010] Each element of the finite element model may have a size corresponding to the gauge length.

[0011] The method may include calculating an estimated stress at the toe by multiplying the indicator by a predetermined factor.

[0012] The method includes: creating a first test finite element model for each of a plurality of test structures having a weld including an unfinished toe, the first element extending from the toe along a surface of the base metal, and a second element extending from the toe along a surface of the bead; performing a finite element analysis using the plurality of first test finite element models; selecting a first stress from among stresses at nodes other than the toe in the first element for each of the plurality of first test finite element models; selecting a second stress from among stresses at nodes other than the toe in the second element for each of the plurality of first test finite element models; and using the first stress and the second stress as indicators for estimating the stress at the toe for each of the plurality of first test finite element models. The method may include selecting a stress having a large absolute value among the stresses; creating a second test finite element model for each of the plurality of test structures, wherein an end of each of the second test finite element models is finished in a circular arc shape; performing finite element analysis using the plurality of second test finite element models; calculating an average value of stresses at a plurality of nodes within an area including the toe of the second test finite element model and corresponding to the strain gauge for each of the plurality of test structures; calculating an individual coefficient for each of the plurality of test structures by dividing the average value by the index of the first test finite element model; and calculating a predetermined coefficient based on the plurality of individual coefficients of the plurality of test structures. Effect of the Invention

[0013] According to the present disclosure, it is possible to estimate the stress at the toe of the weld. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a perspective view showing an example of a structure including a welded portion. [Diagram 2] FIG. 2 is a cross-sectional view showing a weld including an unfinished toe. [Diagram 3] FIG. 3 is a cross-sectional view showing a finished toe as specified in JIS E4208-1. [Figure 4] FIG. 4 is a flow chart illustrating a method according to an embodiment. [Diagram 5] FIG. 5 is a cross-sectional view of a finite element model including an unfinished toe. [Figure 6] FIG. 6 shows an example of a finite element analysis. [Figure 7] FIG. 7 shows an example of a finite element analysis. [Figure 8] FIG. 8 shows an example of a finite element analysis. [Figure 9] FIG. 9 shows an example of a finite element analysis. [Figure 10] FIG. 10 is a perspective view showing another example of a structure including a welded portion. [Figure 11] FIG. 11 shows an example of a finite element analysis. [Figure 12] FIG. 12 shows an example of a finite element analysis. [Figure 13] FIG. 13 shows an example of a finite element analysis. [Figure 14] FIG. 14 shows the individual coefficients for each test structure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The specific dimensions, materials, numerical values, etc. shown in the embodiments are merely examples for facilitating understanding, and do not limit the present disclosure unless otherwise specified. In this specification and drawings, elements having substantially the same functions and configurations are given the same reference numerals to avoid repeated explanations, and elements not directly related to the present disclosure are omitted from the drawings.

[0016] 1 is a perspective view showing an example of a structure (test structure) 100 including a welded portion 50. For example, the structure 100 may be a part of a component for a railway vehicle, such as a bogie frame. The structure 100 is not limited to this, and may be another structure including a welded portion.

[0017] For example, the structure 100 includes a first plate (base material) 10 and two second plates (base materials) 20. For example, the second plates 20 are welded to each of the mutually opposing surfaces 11 of the first plate 10. For example, the second plates 20 are perpendicular to the surfaces 11. A weld 50 is formed between the first plate 10 and the two second plates 20. The structure 100 includes four beads B. A toe t is formed between the bead B and the first plate 10. Also, a toe t is formed between the bead B and the second plates 20. The toes t are unfinished. In this disclosure, "unfinished" means that the toes are not machined after welding.

[0018] Figure 2 is a cross-sectional view showing a weld 50 including an unfinished toe t. For better understanding, Figure 2 shows only one toe t between the bead B and the first plate 10. The unfinished toe t can be roughly represented on the cross-sectional view as simply the point where two straight lines intersect with each other.

[0019] 3 is a cross-sectional view showing a finished toe t defined in JIS E4208-1. Like FIG. 2, FIG. 3 shows only one toe t between the bead B and the first plate 10.

[0020] JIS E4208-1 specifies the static load test method used to check the strength of railroad vehicle components such as bogie frames. This method uses a single-axis strain gauge S with a length of 5 mm. In JIS E4208-1, when the strain gauge S is attached to a portion having a small radius of curvature, such as the unfinished toe t (see Figure 2) described above, the toe t is finished into an arc shape with a radius of about 3 mm, as shown in Figure 3. The strain gauge S is attached to the toe t so that it straddles the first plate 10 and the bead B, and 1 / 2 to 2 / 3 of the gauge length covers the first plate (base material) 10.

[0021] Generally, finite element analysis is used to calculate the stress applied to a structure. Therefore, it is conceivable that the static load test specified in JIS E4208-1 is performed by finite element analysis. However, when performing this static load test by finite element analysis, the toe t of the finite element model needs to be formed into an arc shape with a radius of about 3 mm. In addition, it is necessary to calculate the stress by averaging the calculated values ​​at multiple nodes included in the area corresponding to the strain gauge S. Performing these tasks for each new design can be a burden for the designer.

[0022] In consideration of the above problems, this embodiment proposes a method for estimating stress obtained by a static load test specified in JIS E4208-1 using a finite element model including an unfinished toe t. That is, this embodiment proposes a method for estimating stress applied to a finished toe t specified in JIS E4208-1 using a finite element model including an unfinished toe t.

[0023] Next, a method according to an embodiment will be described.

[0024] FIG. 4 is a flow chart illustrating a method according to an embodiment.

[0025] First, a first test finite element model is created (step S100).

[0026] 5 is a cross-sectional view showing a finite element model (first test finite element model) FM including an unfinished toe t. FIG. 5 shows an example of the finite element model FM corresponding to the weld 50 in FIG. 2. In FIG. 5, only elements around the unfinished toe t are shown. The measurement area SA is an area corresponding to the above-mentioned strain gauge S. Specifically, the measurement area SA is set so that the measurement area SA straddles the first plate 10 and the bead B, and 1 / 2 to 2 / 3 of the measurement area SA is located on the first plate 10.

[0027] With reference to Fig. 2, for example, a CAD model of a structure 100 having a weld 50 including an unfinished toe t is created. For example, the CAD model can be created using commercially available CAD software. In the example of Fig. 2, a two-dimensional CAD model is created. When a three-dimensional finite element analysis is to be performed, a three-dimensional CAD model is created.

[0028] With reference to FIG. 5, for example, a finite element model FM is created using the created CAD model. For example, the finite element model FM may be created by an automesh function of commercially available CAD software or finite element analysis software. In the example of FIG. 5, a two-dimensional finite element model FM is created. When a three-dimensional finite element analysis is performed, a three-dimensional finite element model is created. In the example of FIG. 5, triangular elements are used. In other examples, quadrilateral elements may be used. When a three-dimensional finite element analysis is performed, tetrahedral or hexahedral elements may be used.

[0029] The finite element model FM is created to include a first element m1 extending from the toe t along the surface 11 of the first plate 10, and a second element m2 extending from the toe t along the surface B1 of the bead B. In the finite element model FM of this embodiment, for example, a secondary element including an intermediate node may be used. In this case, at least the first element m1 and the second element m2 may be created with a node-to-node distance (size) d1 equivalent to the gauge length of the above-mentioned strain gauge S, that is, with a node-to-node distance d1 of about 5 mm (more specifically, greater than 0 and equal to or less than 5 mm). In addition, in the finite element model FM of another embodiment, for example, a primary element may be used. In this case, at least the first element m1 and the second element m2 may be created with a node-to-node distance (size) equivalent to half the gauge length of the strain gauge S, that is, with a node-to-node distance of about 2.5 mm. In these cases, the distance between node n1 of the first element m1 and node n2 of the second element m2 along the surface 11, B1 corresponds to the gauge length of the strain gauge S. Node n1 is adjacent to the toe t of the first element m1 and is located on the surface 11. Node n2 is adjacent to the toe t of the second element m2 and is located on the surface B1. The other elements may be created with similar sizes or may be created with different sizes. When performing a three-dimensional finite element analysis, the finite element model FM may be formed such that a node on one surface of the first element m1 and a node on one surface of the second element m2 are arranged on a plane (cross section) that is perpendicular to the surface 11 of the first plate 10 and includes the area where the strain gauge S is attached. Hereinafter, this embodiment will be described assuming that a secondary element including an intermediate node is used in the finite element model FM.

[0030] The measurement area SA is defined by the intermediate node n1 and the intermediate node n2. Specifically, one end of the measurement area SA is defined by the intermediate node n1, and the other end of the measurement area SA is defined by the intermediate node n2.

[0031] A finite element model (first test finite element model) FM as described above is created for each of a plurality of test structures having a weld 50 including an unfinished toe t.

[0032] Referring to FIG. 4, a finite element analysis is performed using a plurality of first test finite element models FM (step S102).

[0033] For each analysis result, in the first element m1, a first stress is selected from the stresses of the nodes other than the toe t (step S104). Specifically, in this embodiment, the stress of the intermediate node n1 adjacent to the toe t is selected as the first stress.

[0034] For each analysis result, in the second element m2, a second stress is selected from the stresses of the nodes other than the toe t (step S106). Specifically, in this embodiment, the stress of the intermediate node n2 adjacent to the toe t is selected as the second stress.

[0035] For each analysis result, the first stress and the second stress, i.e., the stress at the intermediate node n1 and the stress at the intermediate node n2, whichever has the larger absolute value, is selected as an index for estimating the stress at the toe t (step S108).

[0036] FIG. 6 shows an example of finite element analysis. In FIG. 6 and the following FIGS. 7 to 9, 11 to 13, the display of elements and nodes is omitted. In the example of FIG. 6, the structure 100 shown in FIG. 1 was created using a 1 / 4 cut two-dimensional finite element model. In the example of FIG. 6, the end of the first plate 10 was pulled. This corresponds to pulling both ends of the first plate 10. For the toe t shown in FIG. 6, the stress at the intermediate node n1 and the stress at the intermediate node n2 that had the larger absolute value was selected as an index (test structure 1).

[0037] Fig. 7 shows an example of finite element analysis. In the example of Fig. 7, the structure 100 shown in Fig. 1 was created as a two-dimensional finite element model. In the example of Fig. 7, both ends of the first plate 10 were fixed, and one of the second plates 20 was bent. For the toe t shown in Fig. 7, the stress having the larger absolute value among the stresses at the intermediate nodes n1 and n2 was selected as an index (test structure 2).

[0038] FIG. 8 shows an example of a finite element analysis. In the example of FIG. 8, the structure 100 shown in FIG. 1 was created as a two-dimensional finite element model. In the example of FIG. 8, the ends of each second plate 20 were fixed, and one end of the first plate 10 was bent. For the toe t shown in FIG. 8, the stress having the larger absolute value among the stress at the intermediate node n1 and the stress at the intermediate node n2 was selected as an index. In the example of FIG. 8, two finite element analyses were performed by changing the length of the second plate 20 (test structures 3 and 4).

[0039] FIG. 9 shows an example of finite element analysis. In the example of FIG. 9, the structure 100 shown in FIG. 1 was created as a two-dimensional finite element model. In the example of FIG. 9, one end of the first plate 10 was fixed. The other end of the first plate 10 was pulled, and a shear force in the opposite direction was applied to the end of each second plate 20. For the toe t shown in FIG. 9, the stress at the intermediate node n1 and the stress at the intermediate node n2 that had the larger absolute value was selected as an index (test structure 5).

[0040] 10 is a perspective view showing another example of a structure (test structure) 200 including a welded portion 60. For example, the structure 200 may be a part of a component for a railway vehicle, such as a bogie frame. The structure 200 is not limited to this, and may be another structure including a welded portion.

[0041] For example, the structure 200 includes a third plate (base material) 30 and a fourth plate (base material) 40. For example, the fourth plate 40 is welded to a surface 31 of the third plate 30. For example, the fourth plate 40 is perpendicular to the surface 31. A weld 60 is formed between the third plate 30 and the fourth plate 40. The structure 200 includes a bead B. A toe t is formed between the bead B and the third plate 30. Also, a toe t is formed between the bead B and the fourth plate 40. The toe t is unfinished.

[0042] FIG. 11 shows an example of finite element analysis. In the example of FIG. 11, the structure 200 shown in FIG. 10 was created as a 1 / 4 cut three-dimensional finite element model. In the example of FIG. 11, the end of the third plate 30 was pulled. This corresponds to pulling both ends of the third plate 30. For the toe t shown in FIG. 11, the stress having the larger absolute value among the stress at the intermediate node n1 and the stress at the intermediate node n2 was selected as an index (test structure 6).

[0043] FIG. 12 shows an example of finite element analysis. In the example of FIG. 12, the structure 200 shown in FIG. 10 was created as a 1 / 4 cut three-dimensional finite element model. In the example of FIG. 12, the end (top end) of the fourth plate 40 was fixed. Also, the end of the third plate 30 was bent downward. This corresponds to bending both ends of the third plate 30 downward. For the toe t shown in FIG. 12, the stress having the larger absolute value among the stresses of the intermediate nodes n1 and n2 was selected as an index (test structure 7).

[0044] FIG. 13 shows an example of finite element analysis. In the example of FIG. 13, the structure 200 shown in FIG. 10 was created as a three-dimensional finite element model. In FIG. 13, a portion near one end of the third plate 30 is omitted. The other end of the third plate 30 was pulled, and a shear force in the opposite direction was applied to the end of the fourth plate 40. For the toe t shown in FIG. 13, the stress at the intermediate node n1 and the stress at the intermediate node n2 that had the larger absolute value was selected as an index (test structure 8).

[0045] With reference to FIG. 4, a second test finite element model is created for each of the above test structures 1 to 8 (step S110). Specifically, with reference to FIG. 3, in the second test finite element model, at least the toe t of the measurement target is finished into an arc shape with a radius of 3 mm (not shown). The second test finite element model differs from the first test finite element model FM in that the toe t is finished into an arc shape with a radius of 3 mm. In other respects, the second test finite element model is the same as the first test finite element model FM. Also, the size of the elements of the second test finite element model may be different from the size of the elements of the first test finite element model FM. For example, since the second test finite element model includes an arc shape with a radius of 3 mm, at least the arc-shaped region may be created with elements smaller than the above-mentioned first element m1 and second element m2 of the first test finite element model FM. For example, the second test finite element model may be created to include a node at the toe t.

[0046] 4, a finite element analysis is performed using a plurality of second test finite element models (step S112). In step S112, the same loading conditions and boundary conditions are used as those used for the first test finite element models FM in step S102 above.

[0047] An individual coefficient is calculated for each of the test structures 1 to 8 (step S114).

[0048] FIG. 14 shows the individual coefficients of each test structure. For each of test structures 1 to 8, the average value of the stresses of multiple nodes in the region including the toe t of the second test finite element model and corresponding to the strain gauge S was calculated. In addition, for each of test structures 1 to 8, the calculated average value was divided by the index of the first test finite element model FM, i.e., the stress of the intermediate node n1 or the intermediate node n2, to calculate the individual coefficient. As shown in FIG. 14, the individual coefficients varied between 0.98 and 1.27, but were generally close to 1. This means that the individual coefficients of test structures 1 to 8 were generally equal.

[0049] For each of the test structures 1 to 8, a finite element analysis was performed using the method shown in Patent Document 1. For each of the test structures 1 to 8, an individual coefficient was calculated by dividing the stress at the node at the toe t of the second test finite element model by the average stress in the region where the strain gauge is attached in Patent Document 1 (not shown). As a result, the individual coefficients in the method of Patent Document 1 varied between 1.11 and 3.10. These results show that the method according to the present embodiment can calculate individual coefficients within a small range of variation for various joint shapes and load forms.

[0050] Referring to Fig. 4, a predetermined coefficient is calculated based on the individual coefficients of the test structures 1 to 8 (step S116). For example, the predetermined coefficient may be calculated by calculating an average value of the multiple individual coefficients and considering a safety margin. For example, in the example of Fig. 14, the average value of the multiple individual coefficients is 1.16, and the standard deviation σ is 0.08. When 2σ is considered as a safety margin, the predetermined coefficient is 1.32.

[0051] Referring to FIG. 4, in the next design, the index of a new structure having a weld including an unfinished toe is calculated by the method shown in steps S100 to S108 used for the first test finite element model FM. Specifically, a finite element model of the new structure is created (step S100), and a finite element analysis is performed (step S102). From the analysis result, a first stress and a second stress are selected (steps S104, S106), and an index is selected from the first stress and the second stress (step S108). The obtained index, that is, the stress having a larger absolute value among the stresses of the intermediate node n1 and the stresses of the intermediate node n2, is multiplied by the above-mentioned predetermined coefficient (for example, 1.32) to estimate the stress applied to the finished toe t specified in JIS E4208-1. The estimated stress is compared with the criteria specified in JIS E4207.

[0052] The method according to the present embodiment as described above includes the steps of: creating a finite element model FM of a structure 100 having a weld 50 including an unfinished toe t, the finite element model including a first element m1 extending from the toe t along the surface 11 of the first plate 10, and a second element m2 extending from the toe t along the surface B1 of the bead B; performing a finite element analysis using the finite element model FM; selecting a first stress from the stresses of nodes other than the toe t in the first element m1; selecting a second stress from the stresses of nodes other than the toe t in the second element m2; and calculating the stress at the toe t (in the present embodiment, according to JIS Based on E4208-1, a strain gauge S having a gauge length of 5 mm is attached to the toe t, which is finished into an arc shape with a radius of about 3 mm, so that 1 / 2 to 2 / 3 of the gauge length covers the first plate (base material) 10, and the stress measured in this state is selected from the first stress and the second stress, which has a larger absolute value, as an index for estimating the toe t (hereinafter referred to as "JIS stress"). When creating a finite element model including an unfinished welded part, the toe may be a stress singularity. Therefore, it is difficult to calculate the stress at the toe t with high accuracy. However, for example, among the stresses around the toe t, the stress having a larger absolute value has a correlation with the JIS stress as described above. Therefore, by using the index according to this embodiment, the stress at the toe t can be estimated.

[0053] In the method according to the present embodiment, selecting the first stress includes selecting the stress of node n1 adjacent to the toe t in the first element m1, and selecting the second stress includes selecting the stress of node n2 adjacent to the toe t in the second element m2. According to this configuration, by selecting the stress of the node adjacent to the toe, it is possible to obtain a value that has a high correlation with the JIS stress, and it is possible to estimate the JIS stress with higher accuracy.

[0054] Moreover, in the method according to this embodiment, creating the finite element model FM of the structure 100 includes creating each of the first element m1 and the second element m2 such that the distance between the node n1 adjacent to the toe t in the first element m1 and the node n2 adjacent to the toe t in the second element m2 corresponds to the gauge length of the single-axis strain gauge S used in the static load test method specified in JIS E4208-1. With this configuration, it is possible to perform an analysis taking into account the gauge length of the strain gauge S used in the static load test.

[0055] Moreover, in the method according to this embodiment, each element of the finite element model FM has a size equivalent to the gauge length of the strain gauge S. With such a configuration, it is possible to reduce the number of elements of the finite element model FM.

[0056] The method according to the present embodiment also includes calculating an estimated stress at the toe t (in the present embodiment, the finished toe t) by multiplying the indicator by a predetermined coefficient. With this configuration, the stress at the toe t can be estimated.

[0057] Moreover, the method according to the present embodiment includes: creating a first test finite element model FM for each of a plurality of test structures 1 to 8 having a weld 50 including an unfinished toe t, the first element m1 extending from the toe t along a surface 11 of the first plate 10 (the second plate 20 in the example of FIG. 8 ) and a second element m2 extending from the toe t along a surface B1 of the bead B; performing a finite element analysis using the plurality of first test finite element models FM; selecting a first stress from among the stresses of nodes other than the toe t in the first element m1 for each of the plurality of first test finite element models FM; selecting a second stress from among the stresses of nodes other than the toe t in the second element m2 for each of the plurality of first test finite element models FM; The method includes: selecting a stress having a larger absolute value from the first stress and the second stress as an index for estimating the stress at t; creating a second test finite element model for each of the plurality of test structures 1 to 8, the toe of each of the second test finite element models being finished in a circular arc shape; performing a finite element analysis using the plurality of second test finite element models; calculating an average value of stresses at a plurality of nodes in an area including the toe of the second test finite element model and corresponding to the strain gauge S for each of the plurality of test structures 1 to 8; calculating an individual coefficient for each of the plurality of test structures 1 to 8 by dividing the average value by the index of the first test finite element model FM; and calculating a predetermined coefficient based on the plurality of individual coefficients of the plurality of test structures 1 to 8. With this configuration, the stress acting on the finished toe t specified in JIS E4208-1 can be estimated.

[0058] Although the embodiments have been described above with reference to the accompanying drawings, the present disclosure is not limited to the above embodiments. It is clear that a person skilled in the art can think of various modifications or alterations within the scope of the claims, and it is understood that these also belong to the technical scope of the present disclosure. In addition, the steps of the method of the above embodiments do not have to be performed in the above order, and may be performed in a different order as long as there is no technical contradiction.

[0059] Also, for example, steps S110 and S112 with respect to the second test finite element model may be performed before steps S100 through S108 with respect to the first test finite element model. [Explanation of symbols]

[0060] 10 First plate (base material) 11 Surface of the first plate 20 Second plate (base material) 30 3rd plate (base material) 31 Surface of the third plate 40 4th plate (base material) 50 Welding 60 Welding 100 Structures (Test Structures) 200 Structures (Test Structures) B Bead B1 Bead surface FM finite element model (first test finite element model) m1 1st element m2 second element n1 Node adjacent to the toe n2 Node adjacent to the toe S strain gauge t toe

Claims

1. creating a finite element model of a structure having a weld including an unfinished toe, the model including a first element extending from the toe along a surface of the base metal, and a second element extending from the toe along a surface of the bead; performing a finite element analysis using the finite element model; and selecting a first stress from among stresses at nodes other than the toe in the first element; selecting a second stress from among stresses at nodes other than the toe in the second element; selecting a stress having a larger absolute value from the first stress and the second stress as an index for estimating the stress at the toe; Including, A method for assessing the stresses in welds.

2. selecting the first stress includes selecting a stress at a node of the first element adjacent the toe; selecting the second stress includes selecting a stress at a node of the second element adjacent to the toe. The method for assessing stress on a weld according to claim 1.

3. creating the finite element model of the structure includes creating each of the first element and the second element such that a distance between the node adjacent to the toe in the first element and the node adjacent to the toe in the second element corresponds to a gauge length of a uniaxial strain gauge used in a static load test method specified in JIS E4208-1; The method for assessing stress on a weld according to claim 2.

4. Each element of the finite element model has a size corresponding to the gauge length. A method for assessing stress on a weld as claimed in claim 3.

5. The method comprises: calculating an estimated stress at the toe by multiplying the index by a predetermined coefficient; Including, A method for assessing stress on a weld as claimed in claim 4.

6. The method comprises: creating a first test finite element model of each of a plurality of test structures having a weld including an unfinished toe, the first element extending from the toe along a surface of the base metal and the second element extending from the toe along a surface of the bead; performing a finite element analysis using the plurality of first test finite element models; selecting a first stress from among stresses at nodes other than the toes in the first element for each of the plurality of first test finite element models; selecting a second stress from among stresses at nodes other than the toes in the second element for each of the plurality of first test finite element models; selecting, for each of the plurality of first test finite element models, a stress having a larger absolute value among the first stress and the second stress as an index for estimating a stress at the toe; creating a second test finite element model for each of the plurality of test structures, a toe of each second test finite element model being finished in a circular arc shape; performing a finite element analysis using the plurality of second test finite element models; and calculating an average value of stresses at a plurality of nodes in a region of the second test finite element model that includes the toe and corresponds to the strain gauge for each of the plurality of test structures; calculating an individual coefficient for each of the plurality of test structures by dividing the average value by the index of the first test finite element model; calculating the predetermined coefficient based on the plurality of individual coefficients of the plurality of test structures; Including, A method for assessing stress on a weld as claimed in claim 5.

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