JP5325194B2 - Method for evaluating fatigue characteristics of T-joints in T-type welded joint structures - Google Patents

Description

  The present invention relates to a method for simply and quickly evaluating (predicting and estimating) the fatigue characteristics of a T-joint portion in a T-type welded joint structure without actually producing a welded joint and conducting a fatigue test. . The evaluation method of the present invention can be applied to various fields to which T-type welded joint structures such as shipbuilding, offshore structures, low-temperature tanks, line pipes, civil engineering / building structures and the like are applied.

  Most of the fractures in welded structures using thick steel plates such as ships and machines are caused by the occurrence of fatigue cracks, and most of the fatigue cracks are generated from welded joints. This is because the fatigue strength of the welded joint is significantly lower than that of the base material.

  It is known that the fatigue characteristics of the welded joint are greatly affected by the shape of the weld toe on the base metal side (particularly the toe radius). Therefore, conventionally, in order to improve the fatigue characteristics of the welded joint, a method has been used in which the weld toe is smoothed by grinding with a grinder (flattening the shape of the weld) and stress concentration is reduced ( For example, refer nonpatent literature 1.).

  On the other hand, the influence of the material properties (mechanical properties) of the welded joints on the fatigue properties is not clear and has been hardly studied so far. For this reason, in evaluating (predicting) the fatigue characteristics of welded joints, the fact is that they are determined by statistically processing the fatigue test results of many welded joints. Specifically, we changed the conditions of the welded joint part, produced welded joint structural specimens that reflected each condition, and conducted a fatigue test. It is.

  Therefore, Patent Document 1 discloses a test method for simply and quickly evaluating the fatigue fracture susceptibility of a welded heat-affected zone of a steel material without actually performing welding. Here, the fatigue crack is generated and propagated from the weld toe portion where the stress concentration is the most intense, but the position where the fatigue crack is most likely to occur is the weld heat affected zone (HAZ). The fatigue fracture susceptibility of HAZ is evaluated using a test piece imparted with heat history and notch processing. However, since the method of Patent Document 1 is not studied from the material characteristics of the welded joint, it is desired to provide a material design guideline useful for evaluating the fatigue characteristics of the welded joint.

JP 7-103871 A

"Fatigue Design Handbook", edited by the Japan Society of Materials Science, published by Yokendo, published in January 1995

  The present invention has been made in view of the above circumstances, and its object is to easily and quickly evaluate the fatigue characteristics of a T joint portion in a T-type welded joint structure without conducting a complicated fatigue test (prediction / It is to provide a method that can be estimated.

The evaluation method of the present invention that has solved the above problems is a method for evaluating the fatigue characteristics of a T joint portion in a T-type welded joint structure, wherein the radius of curvature of the weld toe portion of the T joint portion is ρ. (Mm), when the uniform elongation (%) of the weld heat affected _{zone of} the T joint is UE _HAZ and the yield stress (MPa) of the weld heat affected _{zone of} the T joint is YP _HAZ , the following formula (1) Is used to evaluate the fatigue characteristics of the T-type welded joint structure by using the weld toe distortion evaluation parameter (1).
Weld toe distortion evaluation parameters (1)
= (1.13 × 10 ⁻² × ρ ^−0.59 ) × (1.05 × 10 ⁻⁴ × UE _HAZ + 1.64 × 10 ⁻² ) × (5.15 × YP _HAZ ^−0.92 ) (1 )

Another evaluation method of the present invention that has solved the above-described problem is a method for evaluating fatigue characteristics of a T joint portion in a T-type welded joint structure, wherein the weld toe portion of the T joint portion The radius of curvature is ρ (mm), the uniform elongation (%) of the welded heat-affected _{zone of the} T joint after 10,000 times of plastic strain is UE _{HAZ, cycle} , and the welded heat-affected _{zone of the} T joint is 10,000 times plastic strain. When the yield stress (MPa) after loading is YP _{HAZ, cycle} , the fatigue characteristics of the T-type welded joint structure are evaluated by using the weld toe strain evaluation parameter (2) expressed by the following formula (2). Therefore, it has a gist.
Weld toe distortion evaluation parameters (2)
= (1.13 × 10 ⁻² × ρ ^−0.59 ) × (1.05 × 10 ⁻⁴ × UE _{HAZ, cycle} + 1.64 × 10 ⁻² ) × (5.15 × YP _{HAZ, cycle} ^−0.92 ) (2)

  The parameters of the formulas (1) and (2) defined in the present invention are useful as an alternative evaluation parameter for the weld toe fatigue characteristics of the T joint portion in the T-type welded joint structure. Thus, the fatigue characteristics of the T joint can be evaluated (predicted and estimated) without performing a fatigue test. The method for evaluating the fatigue characteristics of the T joint according to the present invention is not only when local plastic strain is generated at the weld toe, but also when local plastic strain is repeatedly applied to the weld toe. The fatigue characteristics of the T joint can be evaluated by using the parameter of the formula (1) in the former case and using the parameter of the formula (2) in the latter case.

FIG. 1 is a schematic diagram showing a state in which a fatigue crack is generated by local plastic strain generated locally at a weld toe. FIG. 2 shows that the uniform elongation UE _HAZ of the welded heat affected _{zone of} the T joint is 5% and the yield stress YP _HAZ = 500 MPa of the welded heat affected _{zone of} the T joint is constant, and only the weld toe curvature radius ρ is obtained. It is a graph which shows the influence which it has on the welding toe part local plastic strain amount when making it change. FIG. 3 shows that the weld toe curvature radius ρ = 0.5 mm, the yield stress YP _HAZ = 500 MPa of the weld heat affected _{zone of} the T joint, and the uniform elongation UE _HAZ of the weld heat affected _{zone of the} T joint only. It is a graph which shows the influence which acts on the amount of local plastic strain of a weld toe part when changing. FIG. 4 shows that the welding toe portion curvature radius ρ = 0.5 mm, the uniform elongation UE _HAZ = 5% of the weld heat affected _{zone of the} T joint, and the yield stress YP _HAZ of the weld heat affected _{zone of the} T joint. It is a graph which shows the influence which it has on the welding toe part local plastic strain amount when only changing is carried out. FIG. 5 is a diagram schematically illustrating a state in which plastic strain is locally generated when a fatigue test is performed using the micro-notched test piece used in the example. FIG. 6 is a graph showing the relationship between the weld toe strain evaluation parameter (1) defined in the present invention and the stress range Δσ / TS corresponding to the fatigue crack initiation life of 10 ⁵ times in the examples. FIG. 7 is a graph showing the relationship between the weld toe strain evaluation parameter (2) defined in the present invention and the stress range Δσ / TS corresponding to the fatigue crack initiation life of 10 ⁵ times in the examples.

In order to provide a method capable of evaluating (predicting and estimating) the fatigue characteristics of a T joint portion in a T-type welded joint structure from the viewpoint of material design without performing a complicated fatigue test, I have been considering it. As a result, if the weld toe part distortion evaluation parameter (1) represented by the following expression (1) or the weld toe part distortion evaluation parameter (2) represented by the following expression (2) is used, fatigue of the T joint part will be described. The inventors have found that the characteristics can be evaluated easily and quickly, and completed the present invention. Of these, the weld toe portion distortion evaluation parameter (1) is useful for evaluating fatigue characteristics when local plastic strain occurs at the weld toe portion, and the weld toe portion strain evaluation parameter (2) is: This is useful for evaluating fatigue characteristics when local plastic strain is repeatedly applied to the weld toe.
Weld toe distortion evaluation parameters (1)
= (1.13 × 10 ⁻² × ρ ^−0.59 ) × (1.05 × 10 ⁻⁴ × UE _HAZ + 1.64 × 10 ⁻² ) × (5.15 × YP _HAZ ^−0.92 ) (1 )
In the formula, ρ is the radius of curvature of the weld toe (mm)
UE _HAZ is the uniform elongation (%) of the weld heat affected _zone of the T joint
YP _HAZ means the yield stress (MPa) of the weld heat affected _zone of the T joint.

Weld toe distortion evaluation parameters (2)
= (1.13 × 10 ⁻² × ρ ^−0.59 ) × (1.05 × 10 ⁻⁴ × UE _{HAZ, cycle} + 1.64 × 10 ⁻² ) × (5.15 × YP _{HAZ, cycle} ^−0.92 ) (2)
In the formula, ρ is the radius of curvature of the weld toe (mm)
UE _{HAZ, cycle} is 10000 times after plastic strain loading of weld heat affected _{zone of} T joint
Uniform elongation (%),
YP _{HAZ, cycle} is the value after 10,000 times plastic strain loading of the weld heat affected _zone of the T joint.
It means the yield stress (MPa).

  Hereinafter, the background of the present invention will be described with reference to FIG.

  In the present invention, a T joint shape (T joint portion) widely used in a welded structure among the weld joint shapes is targeted, and the relationship between fatigue characteristics and material properties of the T joint portion is clarified by simulation. A basic experiment was conducted. Here, a T-type welded joint structure is used in which a vertical member butt-welded with a high-strength steel plate and a horizontal member butt-welded with a high-strength steel plate are joined by welding. The plate thickness of the horizontal member and the vertical member used in the basic experiment was 60 mm, and the nominal stress (corresponding to YP of the base material) of the horizontal member was 490 MPa.

In the study, we focused not only on the weld toe curvature radius ρ (mm), which has a close relationship with fatigue properties, but also on the uniform elongation (UE) and yield stress (YP) as material property factors. . This is because the amount of local plastic strain generated at the weld toe is a governing factor of fatigue characteristics (see FIG. 1), and UE and YP are related to plastic strain. In addition, fatigue cracks are generated and propagated from the weld toe where the strain concentration is the most intense, and this toe is a weld heat affected zone (HAZ). We focused on stress. In the present invention, the uniform elongation (%) of the _{HAZ of} the T joint is UE _HAZ , and the yield stress (MPa) of the weld heat affected _{zone of} the T joint is YP _HAZ .

And when the influence which each of the conditions ((rho), _UEHAZ , and _YPHAZ ) of a T joint part has on the amount of plastic distortion of a weld toe part was investigated, the result of FIGS. 2-4 was obtained.

FIG. 2 is a graph showing the effect on the weld toe local plastic strain amount when only UE is changed and UE _HAZ = 5% and YP _HAZ = 500 MPa.

As shown in FIG. 2, when conditions other than ρ are constant, the amount of local plastic strain at the weld toe portion decreases exponentially as ρ increases. This result is consistent with conventional knowledge. As described above, it is known that the weld toe radius affects the strain concentration. As the toe radius is larger, the stress concentration is reduced, so that the local plastic strain is also reduced. The following relational expression (1A) is derived from the result of FIG.
Weld toe ^local plastic strain = 1.13 × 10 ⁻² × ρ ^−0.59 (1A)
ρ is the radius of curvature (mm) of the weld toe, and the uniform elongation UE _HAZ (%) of the weld heat affected _{zone of the} T joint and the yield stress YP _HAZ (MPa) of the weld heat affected _{zone of the} T joint are constant. It is.

FIG. 3 is a graph showing the influence on the weld toe local plastic strain when only UE _HAZ is changed, and ρ = 0.5 mm and YP _HAZ = 500 MPa.

Than 3, local plastic strain generating behavior fluctuates greatly by a change in the UE _HAZ, also it can be seen as small as weld toe departments portions plastic strain amount UE _HAZ decreases. From the result of FIG. 3, the following relational expression (1B) is derived.
Weld toe local plastic strain = 1.05 × 10 ⁻⁴ × UE _HAZ + 1.64 × 10 ⁻²
... (1B)
UE _HAZ is the uniform elongation (%) of the weld heat affected _zone of the T joint, and the weld toe curvature radius ρ (mm) and the yield stress YP _HAZ (MPa) of the weld heat affected _{zone of the} T joint are constant. It is.

FIG. 4 is a graph showing the effect on the toe local plastic strain amount when only YP _HAZ is changed and ρ = 0.5 mm and UE _HAZ = 5%. From FIG. 4, the local plastic strain generating behavior varies greatly depending YP _HAZ changes, also can be seen as small as weld toe departments portions plastic strain amount YP _HAZ increases. Since the yield stress in the weld heat affected zone has a large effect on the deformation behavior of the toe during fatigue loading, it is thought that the effect on the local plastic strain at the toe was also increased. The following relational expression (1C) is derived from the result of FIG.
Weld toe ^local plastic strain = 5.15 x YP _HAZ ^-0.92 (1C)
YP _HAZ is the yield stress (MPa) of the welded heat-affected _zone of the T joint, and the weld toe radius of curvature ρ (mm) and the uniform elongation UE _HAZ (%) of the welded heat-affected _{zone of the} T joint are constant. It is.

Based on the results of the above basic experiments, the influence of the above requirements (ρ, UE _HAZ , and YP _HAZ ) on the amount of local plastic strain at the weld toe was examined in detail. As a result, when it is assumed that conditions other than the above requirements (for example, plate thickness of the horizontal member and vertical member, welding method, etc.) are the same without changing, the above formulas (1A) and (1B) It is found that the weld toe local plastic strain amount multiplied by (1C), that is, the parameter (1) represented by the above formula (1) has a good correlation with the fatigue characteristics of the weld toe. The present invention has been completed. The smaller the value of the parameter calculated by the above formula (1), the greater the amount of local plastic strain at the weld toe, indicating better fatigue characteristics (see FIG. 6 described later).

  Further, the above parameters are useful for evaluating fatigue characteristics when local plastic strain is repeatedly applied to the weld toe. In this case, the evaluation parameter of the above formula (2) may be used. I understood. That is, depending on the steel type, the yield stress and uniform elongation may change due to repeated loading of stress exceeding the yield stress. In this case, local plastic strain is repeatedly loaded even at the weld toe. For this reason, the yield stress and uniform elongation of the HAZ part change, and the fatigue life of the weld toe part is greatly affected. If the above formula (2) is used, the fatigue life when the yield stress and uniform elongation change due to repeated loading can be evaluated with high accuracy.

Here, the above formula (2) is the same as the above formula (1), in which UE _HAZ (uniform elongation of the weld heat affected _{zone of the} T joint) is set to UE _{HAZ, cycle} (10000 times plastic strain of the weld heat affected _{zone of the} T joint). YP _HAZ (yield stress of welded heat affected _{zone of} T joint) to YP _{HAZ, cycle} (yield stress after 10000 times plastic strain loading of welded heat affected _{zone of} T joint) Except for the respective replacement, it is exactly the same as the above formula (1).

  In the above formula (2), the number of repetitions was set to 10,000. The changes in yield stress and uniform elongation after repeated loading largely change up to 1000 to 5000 repeated loads, but thereafter Considering an empirical rule that it will be constant, it is as soon as each value at 10,000 times (0.5% strain) is selected as a representative value of the yield stress and uniform elongation of the HAZ part after 5000 times.

  Thus, according to the present invention, the weld toe portion distortion evaluation parameter represented by the above formula (1) or the above formula (2) is useful as an alternative evaluation parameter for the fatigue characteristics of the T joint portion in the T-type welded joint structure. It is characterized in that it has been found. According to the present invention, it is possible to evaluate the fatigue characteristics of the T joint portion without creating a welded joint as in the prior art and actually conducting a fatigue test.

  In the present invention, as described above, the condition not included in the evaluation parameter is made constant, and the expression (1) or the expression (2) is based on the premise that local plastic strain is generated at the weld toe. Therefore, the following matters are listed as preconditions for applying the method of the present invention.

  First, in order to cause local plastic deformation at the weld toe, the nominal stress range of the horizontal member (base material) is approximately 300 to 500 MPa. If the nominal stress of the horizontal member is less than 300 MPa, local plastic deformation may not occur. On the other hand, if it exceeds 500 MPa, the entire surface of the steel sheet may be plastically deformed. Similarly, the tensile strength of the horizontal member and the weld heat affected zone (HAZ) is approximately 400 to 700 MPa.

Further, the allowable ranges of ρ, UE _HAZ and YP _{HAZ to which} the above formula (1) is applied are not particularly limited, but from the viewpoint of generating local plastic deformation at the weld toe, ρ: 0.1 mm or more and 2.0 mm or less, UE _HAZ : 5% or more and 20% or less, YP _HAZ : 300 MPa or more and 650 MPa or less are preferable.

Further, the allowable range of ρ, UE _{HAZ, cycle} and YP _{HAZ, cycle to which} the above formula (2) is applied is not particularly limited, but it is from the viewpoint of causing local plastic deformation at the weld toe. For example, it is generally preferable that ρ: 0.1 mm to 2.0 mm, UE _{HAZ, cycle} : 5% to 20%, and YP _{HAZ, cycle} : 300 MPa to 650 MPa.

  The plate | board thickness of the horizontal member which comprises the welding structure made into object by this invention is 50-80 mm in general when the influence on the stress concentration factor of a weld toe part is considered. Also about a vertical member, it is preferable that it is 50-80 mm in general like the above.

  Other than the above requirements, the present invention is not particularly limited. For example, the welding method for joining a vertical member and a horizontal member is not specifically limited, For example, a submerged arc welding method and a carbon dioxide gas arc welding method are mentioned.

  Moreover, it does not specifically limit about the kind of steel plate which comprises a vertical member and a horizontal member, The steel plate normally used for a welded structure is applicable as long as requirements, such as said tensile strength, are satisfied. The types of the steel plates constituting the vertical member and the horizontal member are preferably the same.

The weld toe distortion evaluation parameters represented by the above formula (1) or the above formula (2) are the weld toe radius ρ and material characteristics (UE _HAZ and YP _HAZ , or UE _{HAZ, cycle} and YP _{HAZ, cycle} ). It is suitably used for comparing and examining the fatigue characteristics of T-joint portions in which at least one of the two is different. The numerical value calculated based on these formulas is an index for determining the superiority or inferiority (fatigue characteristic design guideline) of fatigue characteristics between two or more types of T joints, but the numerical value itself has no meaning. It is not an index for estimating the fatigue characteristics of each T joint.

Specifically, as a typical application example of the present invention, when several T-type welded joints having the same combination of plate thicknesses of the horizontal member and the vertical member are prototyped, a complicated fatigue test is performed on each joint. Even if it is not performed, a simple curvature survey for calculating ρ and a tensile test for calculating the material properties (for example, UE _HAZ and YP _HAZ ) are performed, and the above formula (1) or (2) By calculating and comparing the value of the represented evaluation parameter, it is possible to determine a welded joint having excellent fatigue characteristics. The smaller the numerical value, the better the fatigue characteristics. Therefore, the T joint having the best fatigue characteristics can be selected.

Furthermore, if the relationship between the evaluation parameter represented by the above formula and the necessary fatigue characteristics is created in advance in a database, the material design guidelines, welding conditions, and the like of the T joint portion having excellent fatigue characteristics can be determined. Here, ρ is by changing the type of welding material (specifically, the welding wire forming the weld metal), while the material properties of uniform elongation and yield stress (eg UE _HAZ and YP _HAZ ) are the total during welding. Since both can be changed by changing the amount of heat (J), the relationship between welding conditions and material properties can be made into a database.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, and may be implemented with appropriate modifications within a range that can meet the purpose described above and below. All of these are possible within the scope of the present invention.

Example 1
In the present example, a micro-notch test piece was prepared as a test piece for simulating a welded joint, and fatigue characteristics when a fatigue test was performed using the test piece, the above formula (1) or the above formula (2) The relationship with the weld toe distortion evaluation parameter (1) or (2) represented by

  Specifically, a smooth plate-shaped notch test piece shown in FIG. 5 (a test piece having no discontinuous shape such as a welded portion, length 65 mm × width 16 mm × thickness 4 mm) was prepared. When this test piece is used, strain concentrates in the notch portion and local plastic strain is generated, so that the strain state of the weld toe portion of the T joint can be reproduced.

The fatigue characteristics (fatigue crack life) of the smooth specimen shown in FIG. 5 is the load stress range Δσ (difference between repeated maximum stress S ₁ and repeated minimum stress S ₂ acting in the fatigue test) in terms of tensile strength TS of the specimen. Evaluation was made based on the divided value (Δσ / TS). In this example, a fatigue test was performed by the following method, and a stress range Δσ / TS corresponding to a fatigue crack generation life of 10 ⁵ times was calculated.

(Fatigue test)
The test piece was attached to a hydraulic fatigue testing machine so that a tensile load was applied to the test piece in the axial direction (the arrow direction in FIG. 5), and a repeated load was applied under the condition that S ₁ and S ₂ were constant. S ₁ and S ₂ were measured with a strain cage attached at a position sufficiently away from the notch of the test piece. In addition, three identical specimens were prepared (n = 3), and the stress load conditions were changed under conditions where the fatigue crack initiation life was in the range of about 10 ⁴ to 10 ^6. The relationship of life was obtained, the stress range was formulated as a function of fatigue crack initiation life, and the stress range was calculated when fatigue crack initiation life = 10 ⁵ . Similarly, the relationship between the stress range after cyclic plastic strain of 10,000 cycles (0.5% strain) and the fatigue crack initiation life was obtained, and the stress range when fatigue crack initiation life = 10 ⁵ was calculated.

Specifically, the fatigue test was performed using the test pieces 1 to 8 in Table 1 having different yield stress YP, uniform elongation UE, and notch curvature R, and Δσ / TS was measured by the above method. Furthermore, the weld toe part distortion evaluation parameters (1) and (2) were calculated for the test pieces 1 to 8, respectively. Here, the notch curvature R of the test piece corresponds to the weld toe curvature radius ρ of the T joint, and the yield stress YP and uniform elongation UE of the test piece are the yield stress YP of the HAZ part of the T joint part, respectively. _{It corresponds to HAZ} or YP _{HAZ, cycle} and uniform elongation UE _HAZ or UE _{HAZ, cycle} .

  These results are also shown in Table 1. FIG. 6 is a graph showing the relationship between the weld toe portion distortion evaluation parameter (1) and Δσ / TS, and FIG. 7 is a graph showing the relationship between the weld toe portion distortion evaluation parameter (2) and Δσ / TS. Shown in the form.

  From Table 1 and FIGS. 6 and 7, the following can be considered.

  As described above, the smaller the numerical value of the evaluation parameter (1) or (2), the higher the fatigue characteristics tend to be. However, the results of FIGS. 6 and 7 almost agree with this tendency. Yes. For example, referring to FIG. 6, among test pieces 1 to 8, test pieces 2 and 4 having the smallest evaluation parameter (1) have a larger Δσ / TS and improved fatigue characteristics than other test pieces. . The same tendency as in FIG. 6 was also observed in FIG.

  Specifically, for example, when test pieces 1 and 3 in Table 1 (both are notched curvature R = 0.8 mm) and test pieces 2 and 4 (both are notched curvature R = 1.6 mm) are compared, The test pieces 2 and 4 having a larger notch curvature R than the pieces 1 and 3 have a large Δσ / TS and the numerical values of the evaluation parameters (1) and (2) are small (see FIG. 6). However, this result is consistent with the conventional knowledge (the larger the weld toe curvature radius ρ, the better the fatigue characteristics).

On the other hand, even if the notch curvature R is the same, the fatigue characteristics may differ depending on the material characteristics. Specifically, since the test pieces 2 and 4 having the notch curvature R = 1.6 mm have different YP and UE (corresponding to YP _HAZ and uniform elongation UE _HAZ of the T joint portion), the above evaluation parameters Although the numerical values of (1) and (2) are different, the test piece 2 having a smaller numerical value of the evaluation parameters (1) and (2) than the test piece 4 is excellent in fatigue characteristics. Similarly, the test pieces 1 and 3 having the notch curvature R = 0.8 mm have different evaluation parameters (1) because YP and UE of the test piece (corresponding to YP _HAZ and uniform elongation UE _HAZ of the T joint portion) are different. ) And (2) are different examples, but the test piece 1 having smaller evaluation parameters (1) and (2) than the test piece 3 is excellent in fatigue characteristics.

  These results are derived for the first time by using the above-mentioned parameters defined in the present invention, and according to the present invention, the fatigue properties between test pieces caused by material properties that could not be discriminated in the past are also evaluated. It is very useful in that it was able to.

Claims (2)

A method for evaluating fatigue characteristics of a T-joint portion in a T-type welded joint structure,
The radius of curvature of the weld toe of the T joint is ρ (mm), the uniform elongation (%) of the weld heat affected _{zone of} the T joint is UE _HAZ , and the yield stress (MPa) of the weld heat affected _{zone of} the T joint. ) Is YP _HAZ, and the fatigue characteristics of the T-type welded joint structure is evaluated by using the weld toe distortion evaluation parameter (1) represented by the following formula (1). Fatigue property evaluation method.
Weld toe distortion evaluation parameters (1)
= (1.13 × 10 ⁻² × ρ ^−0.59 ) × (1.05 × 10 ⁻⁴ × UE _HAZ + 1.64 × 10 ⁻² ) × (5.15 × YP _HAZ ^−0.92 ) (1 ) A method for evaluating fatigue characteristics of a T-joint portion in a T-type welded joint structure,
The radius of curvature of the weld toe of the T joint is ρ (mm), the uniform elongation (%) of the weld heat affected zone of the T joint after 10000 plastic strain loading is UE _{HAZ, cycle} , By using the weld toe strain evaluation parameter (2) represented by the following formula (2) when the yield stress (MPa) after 10000 times plastic strain loading of the weld heat affected _zone is YP _{HAZ, cycle} , the T-type A method for evaluating fatigue characteristics of a T-joint portion, characterized by evaluating fatigue characteristics of a welded joint structure.
Weld toe distortion evaluation parameters (2)
= (1.13 × 10 ⁻² × ρ ^−0.59 ) × (1.05 × 10 ⁻⁴ × UE _{HAZ, cycle} + 1.64 × 10 ⁻² ) × (5.15 × YP _{HAZ, cycle} ^−0.92 ) (2)