JP4555794B2 - Metal parts or metal structures excellent in fatigue crack initiation / propagation prevention characteristics and methods for producing the same - Google Patents

Description

  The present invention relates to a metal part or metal in which a metal part or metal structure using ribs for stiffening or reinforcement of a member is repeatedly subjected to a load in the length direction of the rib, and there is a concern about the occurrence or propagation of fatigue cracks. The present invention relates to a manufactured structure (including a welded structure) and a manufacturing method thereof.

Rib plates are attached to metal parts and metal structures by various methods such as welding, adhesion, casting, forging, and various plastic workings. A portion where the ribs serving as structural stress concentration portion is attached, a portion the rib longitudinal direction of the end, the repetitive load acting on the component or structure, occurrence and development of fatigue crack is a concern The In particular, the toe end of the length direction of the welding ribs, fatigue crack tends to occur because the residual stress and the stress concentration is superposed, it is often a problem relating to the component or structure life.
As a conventional technique of Fatigue Crack Initiation prevent metal parts or metal structures, or methods for removing old from the residual stress by heat treatment on the stress concentrated portion occurring in the fatigue crack, cutting using a device such as a grinder A method of reducing the stress concentration by smoothing the shape of the weld toe by the treatment (for example, see Patent Document 1) , and applying plastic working by hitting the weld toe by the peening treatment to reduce the welding residual stress and method of improving the part shape (e.g., Patent Document 2, Patent Document 3.) is widely used, thereby improving the generation characteristics of the fatigue crack.

In addition, a method of welding while applying heat in the vicinity of the weld for releasing the residual stress (see Patent Document 4) and a method in which the residual stress is reduced in consideration of the welding order of the rotating weld joint (Patent Document) 5, see Patent Document 6.) Residual stress distribution is changed by additional welding or linear heating (refer to Patent Document 7, Patent Document 8), or stress concentration is reduced by devising the shape of the weld. (See Patent Document 9).
JP 05-069128 A JP 2003-001476 A JP 2003-001477 A Japanese Patent Laid-Open No. 11-147193 Japanese Patent Laid-Open No. 08-019860 Japanese Patent Laid-Open No. 08-155635 JP 08-1118012 A Japanese Patent Laid-Open No. 08-112688 JP 08-267234 A

However, if the method according to the heat treatment of the prior art, when applied in a field such as large structure, it is necessary to transport to the place of applying a heat treatment equipment, equipment is much transport difficult to become large In many cases, the heat capacity of the structure itself is large and inefficient, which is difficult to apply. In the method according to the cutting process, but if not welded is effective in prevention of fatigue crack, if the weld, because it can not remove the residual stress, welding residual tensile weld toe portion Stress remains, and the effect of preventing the occurrence of fatigue cracks is limited. Further, peening is effective in generating deterrence characteristics improve fatigue crack, because the site to the action of the compression stress is limited to near the site struck,-out once the fatigue and fatigue crack occurs Cracks This is considered to be less effective in preventing the progress of

Further, in the method of welding while applying heat in the vicinity of the weld for releasing the residual stress, the main plate may be deteriorated due to heating. Further, if the residual stress is lowered in consideration of the welding order of the turn welded joint, the tensile residual stress due to the final bead cannot be avoided. In addition, it is difficult to manage the conditions for changing the residual stress distribution by additional welding or linear heating, and there is a concern about the occurrence of a crack from an unexpected part. In addition , if the stress concentration is reduced by devising the shape of the welded part, a large defect remains in the welded part, and it is difficult to confirm the dimensions after construction.
Therefore, in the present invention, the stress concentration is obtained by forming a compressive stress state by a simple method in the vicinity of the stress concentration portion that intersects the lengthwise end of the metal rib on the surface of the metal part or metal structure. Metal structures with excellent fatigue crack initiation / development suppression properties that can suppress the occurrence and propagation of fatigue cracks from the joints and increase resistance to fatigue crack initiation and propagation, and their manufacture It is an object to provide a method.

The gist of the present invention for solving the above problems is as follows.
(1) A plate-shaped metal rib 2 having a thickness t of 1 mm or more, a height h of 3 t or more, and a length l protrudes from a metal main plate or main pipe 1 having a thickness b, and the length of the rib A metal part or a metal structure in which an indentation-shaped compression pre-strained portion is formed in the thickness direction of the rib at the end of the direction, and the compression pre-strained portion has a plate thickness direction compressive strain of 0.5% or more and 25 %, The area p occupying on the rib surface is 0.67 t ² or more, the rib length direction dimension k is 0.5 t or more and 3 (t · b) ^0.5 or less, and the rib height direction dimension d is 0.5 t or less and 0.5 h or less, the distance a between the center of gravity and the main plate or main pipe is 0.5 h or less and 3 t or less, and the distance e from the end to the end in the rib length direction is the rib Further, the end of the rib in the length direction is further reduced by the compression pre-strain. The portion 4 intersecting with the main plate or main pipe is subjected to compressive residual stress, and has excellent fatigue crack generation / propagation suppression characteristics from the rib end portion to the main plate or main pipe. Metal parts or metal structures.
(2) The rib 2 is joined to the main plate or the main pipe 1 by welding, the yield strength of the rib and the welded portion 5 is 95% or more of the yield strength of the main plate or the main pipe 1, and the tensile strength of the rib is the main plate or The fatigue crack of the above (1), characterized in that it is larger than the tensile strength of the main pipe, and the welded portion 5 of the rib has a throat thickness of 0.5 t or more over a distance of 2 h or more from the end of the rib. Metal parts or metal structures with excellent generation / development suppression characteristics.
(3) After forming a plate-like metallic rib 2 having a thickness t of 1 mm or more and a height h of 3 t or more on the surface of a metal main plate or main pipe 1 having a thickness b, the rib plate The compression pre-strained portion 3 having a thickness direction compressive strain of 0.5% or more and less than 25% has a rib length direction dimension k of 0.5 t or more and 3 (t · b) ^0.5 or less, and a rib height direction dimension d. Is an indentation shape in which the area p on the rib surface is 0.67 t ² or more, and the distance a between the center of gravity and the main plate or main pipe is 0.5 h. And the distance e from the end portion to the rib length direction end portion is formed at a position smaller than the rib thickness t, thereby forming the rib length direction end portion, the main plate or Fatigue cracks characterized by imparting compressive residual stress to the part 4 intersecting the main pipe A method for manufacturing metal parts or metal structures with excellent generation / development suppression characteristics.

  The present invention is a surface of a metal part or a metal structure, and by generating a compressive residual stress in a simple manner in advance in a stress concentration portion that intersects with a longitudinal end portion of a metal rib, the stress concentration Since the generation and propagation of fatigue cracks from the parts can be suppressed, the industrial effect is immeasurable.

The present invention provides the stress concentration by generating a compressive residual stress in a simple manner in advance in a stress concentration portion that intersects the lengthwise end portion of the metal rib on the surface of a metal part or metal structure. It is characterized by suppressing the occurrence and propagation of fatigue cracks from the part.
Specifically, the invention described in claim 1 is a plate-shaped metal rib having a thickness t of 1 mm or more, a height h of 3 t or more, and a length l from a metal main plate or main pipe 1 having a thickness b. 2 is a metal part or metal structure in which an indentation-shaped compression pre-strained portion 3 is formed in the thickness direction of the rib 2 at an end in the length direction of the rib, and the compression pre-strain portion 3 Has a plate thickness direction compressive strain of 0.5% or more and less than 25%, an area p on the rib surface of 0.67 t ² or more, and a rib length direction dimension k of 0.5 t or more and 3 (t · b) ^0.5 or less, the rib height direction dimension d is 0.5 t or more and 0.5 h or less, and the distance a between the center of gravity position 17 and the main plate or main pipe is 0.5 h or less and 3 t or less, The distance e from the end to the end in the rib length direction is smaller than the thickness t of the rib 2, The compressive strain Pre, the a longitudinal end of the rib, the portion 4 which intersects with the main plate or main, is characterized in that the compressive residual stress is working.

The object of the present invention is a metal component or metal structure in which a plate-like metallic rib 2 having a length l, a height h, and a thickness t protrudes from a metal main plate or main pipe 1 having a thickness b. The main plate or main pipe made of metal and the protruding rib are in contact with each other, and the end 4 in the length direction of the rib becomes a stress concentration part when a load is applied to a part or a structure, and fatigue occurs under repeated load. This is because it becomes a source of cracks.
In addition, the compression pre-strained portion 3 of 0.5% or more and less than 25% in the rib thickness direction is formed at the end of the rib in the length direction at the portion where the rib contacts the metal main plate or main pipe 1. In order to generate a compressive residual stress at the end of the rib in the length direction, a sufficient residual stress cannot be generated with a compressive strain smaller than 0.5%, and with a strain larger than 25%. This is because the effect reaches a peak, and the reduction of the plate thickness and macroscopic deformation of the member become remarkable, and the shape accuracy as a component or structure is impaired.
The reason why the thickness t of the rib 2 is set to 1 mm or more is that when the t is smaller than 1 mm, it is difficult to manage the pre-strain amount . Even when the rib thickness t is smaller than 1 mm , the same effects as the present invention can be exhibited if the specific matters of the present invention other than the rib thickness t can be applied with high accuracy.
Further, the compression prestrain is applied to the region where the dimension k in the length direction of the rib is 0.5 t or more and 3 (t · b) ^0.5 or less. This is because sufficient compressive residual stress is not generated in the stress concentration portion, and when k is greater than 3 (t · b) ^0.5 , the deformation of the main plate becomes prominent and the occurrence of fatigue cracks is a concern. This is because the compressive residual stress of the sample reaches a peak or decreases.

Moreover, the rib height direction dimension d of the compression pre-strained part is set to 0.5 t or more and 0.5 h or less because the compressive residual stress of the stress concentration part 4 where the occurrence of fatigue cracks is concerned as the value of d increases. Because it becomes. The compression pre-strain is applied to the region where the area p on the rib surface is 0.67 t ² or more, and the compression pre-strain part where the occurrence of fatigue cracks is concerned when the area p is smaller than 0.67 t ^2. This is because a sufficient compressive stress for preventing the generation of fatigue cracks cannot be generated in the stress concentration portion 4 away from 3.
The reason why the distance a between the center of gravity position 17 of the compressive strain portion 3 and the main plate or main pipe is 0.5 h or less and 3 t or less and the distance e from the end of the rib to the indentation is smaller than the thickness t of the rib is as follows. When the compressive strain portion is separated from the end in the length direction of the rib, the compressive residual stress of the stress concentration portion 4 where the occurrence of fatigue cracks is a concern is reduced, and the fatigue crack initiation resistance which is the effect of the present invention is reduced. Because it will end up.

FIG. 1 is a view showing an embodiment of the present invention. In FIG. 1, 1 is a metal plate, 2 is a metal rib plate, 3 is a compression pre-strain portion, and 4 is a stress concentration portion. FIG. 1a shows the shortest distance from the center of gravity 17 of the compression prestrained portion to the metal plate where the occurrence of fatigue cracks is a concern. 1e of FIG. 1 shows the shortest distance between the end of the compressive strain portion 3 and the end of the rib 2 in the length direction.
The invention according to claim 2 is a metal part or metal structure having excellent fatigue crack initiation / development suppressing characteristics according to claim 1, wherein the rib is joined to the main plate or main pipe 1 by welding. The yield strength of the rib and the welded portion 5 is 95% or more of the yield strength of the main plate or the main pipe, the tensile strength of the rib is larger than the tensile strength of the main plate or the main pipe, and the welded portion 5 of the rib is 2 h from the end of the rib. The throat thickness c is 0.5 t or more over the above distance . The rib welded portion 5 has a throat thickness c of 0.5 t or more over a distance of 2 h or more from the end of the rib. The reason is that the compression prestrain applied to the rib and the main plate on which the rib and the rib are attached by welding Without destroying the weld due to welding residual stress generated between the main pipe and the main pipe or the main pipe 1 in contact with the rib plate 2 through the weld, the stress generated by the compression pre-strain applied to the rib is transmitted. This is because a sufficient thickness of the throat is necessary to make it . In addition, the yield strength of the rib and the welded portion 5 is 95% or more of the yield strength of the main plate or the main pipe 1 and the tensile strength of the rib is larger than the tensile strength of the main plate or the main pipe. Or it is for fully transmitting to the main pipe 1, and the effect of this invention becomes high, so that the intensity | strength of a rib and a welding part is high.

FIG. 2 is a view showing an embodiment of the present invention. In FIG. 2, 5 indicates a fillet weld. FIG. 3 shows a cross section when the welded structure of FIG. 2 is cut along a plane corresponding to the center of the plate thickness of the rib plate 2. FIG. 3 c shows the thickness of the fillet weld 5.
According to the third aspect of the present invention, a plate-shaped metallic rib 2 having a thickness l of 1 mm or more and a height h of 3 t or more is formed on the surface of a metal main plate or main pipe 1 having a thickness b. After that, the rib pre-strained portion 3 having a rib thickness direction compressive strain of 0.5% or more and less than 25%, the rib length direction dimension k is 0.5 t or more and 3 (t · b) ^0.5 or less, The indentation shape in which the dimension d in the rib height direction is 0.5 t or more and 0.5 h or less and the area p occupying on the rib surface is 0.67 t ² or more, and its center of gravity position and the main plate or main pipe the distance a is less and 3t below 0.5h, by a distance e from the end to the rib lengthwise end portion is formed to a thickness t smaller than the position of the rib, the rib longitudinal ends a is the portion 4 which intersects with the main plate or main, especially of imparting compressive residual stress That is for the manufacturing method of the excellent metal parts or metal structures to generation and progress suppression characteristics of fatigue cracks. The effect of applying compressive pre-strain after the formation of the metal rib is to cause a shear stress between the rib and the main plate or main pipe, and at the longitudinal end of the rib, intersecting the main plate or main pipe. the portion 4 which is intended to produce a residual compressive stress.

A finite element analysis of the structural model shown in FIG. 4 of the present invention and a structural model that has the same shape as the structural model and does not give a compressive pre-strain is performed, and the compressive pre-strain in the structure of the present invention generates a fatigue crack. The influence of the stress concentrated part on the stress situation will be explained.
As an example , the structural model assumes that the main plate and the rib plate are made of a steel material having a yield stress of 330 MPa and a tensile strength of 490 MPa, and a tensile load acts in the direction of the arrow in FIG. And modeled. There are 25 types of structural models from symbols A to Y as shown in Table 1 together with the dimensions of each part, and finite element analysis was performed for all of these. The thickness b of the main plate of the structural model was 8 to 16 mm, and the thickness t of the rib plate was 8 to 24 mm. The compression pre-strained portion has a rectangular surface in which the length k of the rib plate 2 is 10 to 80 mm and the height d of the rib plate 2 is 8 to 24 mm. The distance ad-2 to the pre-strained portion 3 was 8 to 16 mm, and the distance e from the end in the longitudinal direction of the rib was 5 to 10 mm. About 2.5% of plastic strain was applied to the rib plate 2 as a residual strain in the thickness direction by compressing and unloading the surface to be the pre-strain portion by displacement control.

As an example, FIG. 5 shows an example of the residual stress distribution in the vicinity of the prestrained portion after the prestraining for the model D. When a tensile load is applied in the direction of the arrow of the structural model, the stress at the portion 4 that becomes the stress concentration portion is compressed. The numbers attached to the contour lines in FIG. 5 indicate the tensile stress in the material axis direction of the rib in units of MPa. In addition, in FIG. 5, 6 has shown the cross section at the time of making it half in the plate | board thickness center of the rib board 2. FIG.
Next, the tensile direction stress distribution obtained by applying a half of the yield stress (165 MPa) in the arrow direction of the structural model D after applying the pre-strain in the structural model, obtained by finite element method analysis, is shown in FIG. 7 and FIG. 6 shows the tensile direction stress distribution in the case of model D ′ in which a tensile load half the yield stress is applied in the direction of the arrow in the same manner as the structural model D without prestraining. 6 and 7 indicate the tensile stress in the material axis direction of the rib in units of MPa. The stress at the site 4 of the structural model D is significantly lower than the stress at the site 4 of the structural model D ′.

Generally, metal parts or metal structures subjected to cyclic loading, the stress during use at a site other than the stress concentration are designed to be equal to or less than about half the yield stress. In the stress concentration part 4 as shown by the structural model D ′, stress that yields locally may repeatedly act, and there is a concern about the occurrence of fatigue cracks . In the stress concentration portion 4 of the structural model D of the present invention, the tensile stress generated even when a tensile load that is half the yield stress is applied to the end portion becomes extremely small.
The stress generated in the stress concentration portion 4 when a tensile load is applied to the end portion of the structural model to which the present invention is applied is that resistance to fatigue crack generation increases as the compressive residual stress at the time of unloading with prestrain is increased. Is considered large. The compressive residual stress, in particular, the rib plate thickness t and the height h and compression prestrain portions of the position and size of, also, because if the rib plate is attached by welding is influenced by the shape of the weld The effect of each factor was examined using finite element analysis. Was prepared using the results of the finite element analysis, based on Table 1 described compressive residual stress generated in the stress concentration portion of the structure model of the present invention will be described the present invention according to claim 1.

表１の結果から以下のことが読み取れる。すなわち、モデルＫ、Ｌ、Ｍの結果から、主板に対してリブ板２は厚い方が応力集中部に生じる圧縮残留応力が大きくなっており、本発明に用いられる圧縮予ひずみ部３の寸法についてはリブ板の厚みｔを基準に規定することが妥当であると判断した。
モデルＫ、Ｘ、Ｙ、の結果から、リブ板の背ｈは高い方が応力集中部４に生じる圧縮残留応力が大きい。これは、圧縮予ひずみを受けた部分の周りの弾性領域が大きい方が応力集中部に生じる圧縮残留応力が大きくなることを表しており、圧縮予ひずみを受けた部分の周りの弾性領域が十分確保できるようｈ≧２ｄとした。
モデルＫとＯの比較、モデルＢ、Ｃ、Ｄの比較の結果、また、モデルＨ、Ｉ、Ｊの比較の結果から、圧縮予ひずみ部３の寸法ｄは大きい方が応力集中部に生じる圧縮残留応力が大きく、圧縮応力が顕著に表れるが、ｄが大きくなりｈに近づくと効果が頭打ちになるため、ｄは０．５ｔ以上０．５ｈ以下とした。

The following can be read from the results in Table 1. That is, from the results of models K, L, and M, the compressive residual stress generated in the stress concentration portion increases as the rib plate 2 is thicker than the main plate. Was determined to be appropriate based on the thickness t of the rib plate.
From the results of the models K, X, and Y, the compressive residual stress generated in the stress concentration portion 4 is larger when the rib plate h is higher. This indicates that the larger the elastic region around the part subjected to compressive prestrain, the greater the compressive residual stress generated in the stress concentration part, and the elastic region around the part subjected to compressive prestrain is sufficient. In order to ensure, h ≧ 2d.
From the comparison results of models K and O, models B, C, and D, and the comparison results of models H, I, and J, the compression pre-strained portion 3 having a larger dimension d causes compression at the stress concentration portion. Although the residual stress is large and the compressive stress appears remarkably, d increases to 0.5 h or more and 0.5 h or less because the effect reaches its peak when d increases and approaches h.

From the comparison results of models D, E, F, G, and H and the comparison results of models O, P, Q, R, S, T, and U, when the dimension k of the compression pre-strained portion 3 increases, The generated compressive residual stress is increased, but when the compressive residual stress is increased to a certain extent, the compressive residual stress is reduced. This is because when k is large and the rib plate 2 is thick, the main plate 1 is likely to be bent, and plastic strain is also likely to occur on the main plate side, and 0.5 t <k <3 (t · b) ^0.5 . did.
From the comparison results of models O and N, etc., the smaller the distance e from the end portion of the rib 2 to the compression pre-strained portion 3, the larger the compressive residual stress generated in the stress concentration portion 4, and e <t.
From the comparison results of models A and D, the compressive residual stress generated in the stress concentration portion is larger when the distance ad-2 from the main plate 1 to the compression pre-strained portion 3 is smaller, and a <3t.
From the results of comparison of models U, V, and W, when compressive prestrain is applied in the present invention with rib plates attached to both sides, the compressive residual stress generated in the stress concentration portion is larger than in the case of single-sided rib plates, Both-side ribs are more effective than one-side ribs.

As a method for applying the compression pre-strain, a method of pressing a pressing punch 7 having a circular or rectangular cross section as shown in FIG. 8 against the rib plate 2 using a pressing device or the like can be considered. Other devices are possible as long as they can be loaded. When compression prestrain is applied by the push punch 7, the corner of the push punch 7 creates a step in the rib plate 2. This step generates stress concentration, so that the chamfer is made as smooth as possible. Or curved surface processing is desirable.
As for the cross-sectional shape of the punch, various shapes other than a rectangle can be applied besides the rectangle, and it is considered that there will be no significant difference in the effect, so it can be freely designed, but it will extend the life of the punch and compress the load In order to make the height as low as possible, an outwardly convex solid section is reasonable.
As for the size of the punch, it is important to give sufficient plastic strain to the inside of the steel material, so the size of the punch needs to be proportional to the rib plate thickness t. Further, in order to apply a predetermined compressive strain to the rib plate, a large compressive load is required in proportion to the compression area, and care must be taken because the load may be difficult. Compression prestrain applied area p has been defined as 0.67T ² or more with respect to the plate thickness t, above which excessively large, Ri Na increased in proportion to the load area required to impart prestrain implementation It must be noted that the equipment to be used may become difficult due to the increase in size, and that the flatness of the main plate may be lost due to residual stress due to pre-strain . It is desirable to prepare an appropriate compression prestraining device and set each dimension to be within a range where the effect of the present invention can be expected.

The number of compression loads may be pushed several times until the predetermined strain range is reached. If the load of the compression load device is not sufficient due to the relationship between the size of the punch and the strength of the rib plate 2, the position of the punch is shifted. while, by area the area the 0.67T ² or more areas providing a plurality of times the compression load with 0.5 t ² or more punches, to give the compressive load distortion less than 0.5% or more and 25% A similar effect can be obtained.
Further, in the present invention, if the compression pre-strained portion is not provided after the rib is attached, the compression stress due to the compression pre-strain does not occur at the longitudinal end portion 4 of the rib plate on the surface of the main plate and in contact with the rib plate, and fatigue The effect of preventing crack initiation cannot be obtained. Therefore, in the case of doubt about whether the present invention is applied, the present invention can be easily applied by confirming the residual stress distribution near the compression pre-strained portion by a method using a magnetostriction method or an X-ray. It can be confirmed.
The present invention can also be applied to existing structures, and is also effective as a method for preventing the occurrence of fatigue cracks in existing structures.

A fatigue crack initiation test was performed on the steel sheet with rib plates shown in FIG. The steel plate used is a welded structural steel plate with a main plate 8 having a thickness of 24 mm and a yield stress of 400 MPa, and a rib plate 9 is a welded structural steel plate with a thickness of 10 mm and a yield stress of 380 MPa. The attachment welding 10 of the rib plate 9 was performed by CO ₂ welding using a material having a strength of 490 MPa class. Test pieces F1 to F5 are test bodies to which the present invention is applied, and the dimensions of the compression load portion are shown in Table 2. Moreover, the compression pre-strain amount was 2.5%. The test piece F0 is a test piece to which the present invention is not applied. For any specimen, the rib plate was fillet welded under the same conditions, the leg length was 5 mm, and the cross section of the weld was examined, and a throat thickness of 3.5 mm was ensured.

The applied load is a repetitive load in which the stress amplitude at the edge of the main plate is 1/4 of the yield stress centering on 1/4 of the yield load of the member so that one cycle is 10 times per second. The number of cycles of the repeated load when the fatigue crack length generated in the portion 11 becomes 10 mm was experimentally determined.
As a result of the experiment, a predetermined fatigue crack occurred in the test piece F0 at a repeated load cycle of about 1 × 10 ⁶ times. On the other hand, in the specimen of the present invention, the test piece F1 was 5 × 10 ⁶ times and the test piece F5 was 7 × 10 ⁶ times, and a predetermined crack was observed, but the test pieces F2, F3 and F4 were 1 No fatigue cracks occurred even after 5 × 10 ⁷ times. From this, it is considered that a performance of about 5 times or more can be obtained for the occurrence of fatigue cracks.

Steel pipe poles used for road lighting and the like are subjected to repeated bending loads caused by wind. In addition, a rib plate may be attached to the base of the steel pipe pole for reinforcement, and the stress concentration on the pole side due to the rib plate is superimposed on the end of the rib by superimposing residual stress due to welding and repeated load due to wind. Fatigue cracks may occur at the part. Therefore, a full-scale model of a steel pipe pole 13 having a diameter of 17 cm 2 and a pipe thickness b of 6 mm shown in FIG. 10 was produced. The base portion of the model was attached to the base plate 12 by welding using a rib plate 15, and the present invention was applied to the cylindrical pole 13 side of the rib plate 15. The rib plate 15 had a thickness t of 6 mm, and eight plates were attached by complete penetration welding.
A steel pipe pole model to which the present invention was applied and a normal steel pipe pole model as welded with a rib plate were prepared, a repeated bending test of both swings was performed, and fatigue crack generation characteristics were compared.
When the dimensions of the compression pre-strained portion 14 are indicated by the dimensions of the respective portions shown in FIG. 1, a is 6 mm, d is 12 mm, e is 2 mm, k is 12 mm, and h is 25 mm.
As the loading condition, a double swing test was performed so that the stress amplitude of the base was 160 MPa.
As a result of the experiment, the normal steel pipe pole model has reached the fatigue crack length of 10 mm, which is the fatigue crack evaluation standard used in Example 1, from the stress concentration portion 16 in 7 × 10 ⁵ times, but the model to which the present invention is applied. Then, fatigue cracks could not be confirmed. In the model to which the present invention was applied, when repeated loading was performed up to 1 × 10 ⁷ times, the fatigue crack reached 10 mm, and it was confirmed that the present invention was effective.

It is a figure which shows typically the perspective view which partly cut out the welding structure of Claim 1. It is a figure which shows typically the perspective view which partially cut out the welding structure of Claim 2. It is a figure which shows typically the throat thickness of a welding part with sectional drawing of a welding part. It is a figure which shows typically the structural model which analyzed in order to determine the position and dimension of a compression pre-strain part with a perspective view. It is a figure which shows the stress distribution after the compression pre-strain obtained by model analysis with a perspective view. It is a figure which shows the stress distribution at the time of applying a load, without giving the compression pre-strain obtained by model analysis with a perspective view. It is a figure which shows the stress distribution at the time of applying a load after the compression prestraining obtained by model analysis by a perspective view. It is a figure which shows typically the example of the compression predistortion provision method with a perspective view. It is a figure which shows typically the test piece shape and test method of Example 1 with a perspective view. It is a figure which shows typically the test body shape and test method of Example 2 with a perspective view.

DESCRIPTION OF SYMBOLS 1 Main plate or main pipe 2 Rib plate 3 Compression pre-strained part 4 Stress concentrated part 5 Welded part 6 Structural model central section 7 Punch 8 Steel plate 9 Rib plate 10 Welded part 11 Welded toe part 12 Base plate 13 Steel pipe pole 14 Stress concentrated part 15 Rib plate 16 Compression pre-strain part 17 Center of gravity of compression pre-strain part

Claims (3)

A plate-shaped metal rib 2 having a thickness t of 1 mm or more, a height h of 3 t or more, and a length 1 protrudes from a metal main plate or main tube 1 having a thickness b, and the end of the rib in the length direction A metal part or metal structure in which an indentation-shaped compression prestrained part is formed in the thickness direction of the rib in the part, and the compression prestrained part 3 has a plate thickness direction compressive strain of 0.5% or more and less than 25%. The area p occupying on the rib surface is 0.67 t ² or more, the rib length direction dimension k is 0.5 t or more and 3 (t · b) ^0.5 or less, and the rib height direction dimension d is 0.00. The distance a between the center of gravity and the main plate or the main pipe is 0.5 h or less and 3 t or less, and the distance e from the end to the end in the rib length direction is the thickness of the rib. t is smaller than t, and further, due to the compression pre-strain, at the longitudinal end of the rib Thus, the metal part having excellent fatigue crack generation / propagation preventing characteristics from the rib end to the main plate or main pipe, wherein compressive residual stress is applied to the portion 4 intersecting the main plate or main pipe Or a metal structure.   The rib 2 is joined to the main plate or the main pipe 1 by welding, the yield strength of the rib and the welded portion 5 is 95% or more of the yield strength of the main plate or the main pipe 1, and the tensile strength of the rib is the tensile strength of the main plate or the main pipe. 2. The suppression of the generation and propagation of fatigue cracks according to claim 1, wherein the welded portion 5 of the rib is greater than strength and has a throat thickness of 0.5 t or more over a distance of 2 h or more from the end of the rib. Metal parts or metal structures with excellent characteristics. After forming a plate-like metallic rib 2 having a thickness t of 1 mm or more, a height h of 3 t or more and a length 1 on the surface of a metal main plate or main pipe 1 having a thickness b, compression of the rib in the plate thickness direction is performed. The compression pre-strained portion 3 having a strain of 0.5% or more and less than 25% has a rib length direction dimension k of 0.5 t or more and 3 (t · b) ^0.5 or less, and a rib height direction dimension d of 0. 5t above 0.5h or less, the area p occupied on the rib surface at the indentation shape such that 0.67T ² or more, the distance a is 0.5h less and 3t of the main plate or main and center of gravity position The distance e from the end portion to the rib length direction end portion is formed at a position smaller than the rib thickness t, so that the rib length end portion intersects the main plate or the main pipe. the portion 4, and wherein the imparting compressive residual stress, - the occurrence of the fatigue crack Excellent production method for metal parts or metal structures on exhibition deterrence characteristics.

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