JP2020055012A - Welding structural member - Google Patents

Abstract

To provide a welding structural member which has excellent fatigue strength.SOLUTION: A welding structural member 31 has a base member 32; a joint member 34; a welding bead portion 36; and a stiffening bead portion 38. The stiffening portion 38 is provided in the same side as the welding bead portion 36 when viewed from a butting surface 44a of the joint member 34 in a direction orthogonal to an extending direction of the welding bead portion 36. The stiffening portion 38 is formed so as to increase width from a rear end of the stiffening portion 38 to a front side, and then decrease it toward a front end of the stiffening bead portion 38.SELECTED DRAWING: Figure 18

Description

  The present invention relates to a welded structural member.

  2. Description of the Related Art In recent years, the weight of a vehicle body has been reduced in order to improve the fuel efficiency of an automobile. In order to reduce the weight of the vehicle body, a welded structural member in which high-strength thin steel plates are welded to each other is used as a vehicle body material.

  Excellent fatigue strength is required for a welded structural member used as a component of a vehicle body. However, even when a high-strength thin steel plate is used, it is difficult to sufficiently improve the fatigue strength of the welded structural member. Therefore, various techniques for improving the fatigue strength of welded structural members have been conventionally proposed.

  For example, a fillet arc welded joint disclosed in Patent Document 1 includes a fillet bead for joining metal members together, and a stiffening bead formed so as to overlap the fillet bead. Patent Literature 1 describes that the stiffening bead formed as described above can improve the fatigue strength of a welded joint.

International Publication No. 2013/157557

  However, as a result of various studies by the present inventors, it has been found that when the fillet bead and the stiffening bead are formed as described above, stress concentration may occur in a portion where the beads overlap. . In this case, it is conceivable that the fatigue strength is reduced in the stress concentrated portion.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a welded structural member having excellent fatigue strength.

  The gist of the present invention is the following welded structural member.

(1) a metal base member including a first plate-shaped portion having a flat surface and a thickness of 4.5 mm or less;
A second surface having a thickness of 4.5 mm or less, having a butting surface abutted against the plane of the base member, and a first surface and a second surface parallel to each other extending from the abutting surface in a direction intersecting the plane. Including a plate-shaped portion, a metal joining member,
A welding bead portion extending along the edge of the abutting surface on the first surface side and joining the flat surface of the base member and the joining member;
A stiffening bead portion formed on the plane of the base member and extending substantially parallel to the welding bead portion,
When the abutting surface of the joining member, the weld bead portion and the stiffening bead portion are projected in a direction perpendicular to the plane of the base member,
With reference to the end of the abutting surface in the extending direction of the weld bead portion, the direction in which the abutting surface exists as viewed from the end in the extending direction is the rear, and the opposite direction is the front,
The weld bead portion projects forward from the end of the abutment surface,
The stiffening bead portion is provided on the same side as the weld bead portion, as viewed from the abutting surface, in a direction perpendicular to the direction in which the weld bead portion extends,
The welded structural member, wherein a width of the stiffening bead portion increases from a rear end of the stiffening bead portion to a forward direction, and then decreases toward a front end of the stiffening bead portion.

(2) The welding structural member according to (1), wherein a portion of the stiffening bead portion having a maximum width is located rearward of a position 5 mm forward from the front end of the abutting surface.

(3) The welding structural member according to (1) or (2), wherein a center in the front-rear direction of the stiffening bead portion is located in a range of 0 to 10 mm behind the end of the abutting surface.

(4) The welding according to any one of (1) to (3) above, wherein a portion of the stiffening bead portion having a maximum width is located forward of a center in the front-rear direction of the stiffening bead portion. Structural members.

  ADVANTAGE OF THE INVENTION According to this invention, the fatigue strength of a welded structural member can be improved.

FIG. 1 is a perspective view showing an analysis model of a welding structural member. FIG. 2 is a plan view showing a central portion of the analysis model in the left-right direction. FIG. 3 is a plan view showing an analysis model having a stiffening bead portion. FIG. 4 is a diagram showing an analysis result. FIG. 5 is a diagram illustrating an analysis result. FIG. 6 is a plan view showing an analysis model having a stiffening bead portion. FIG. 7 is a diagram showing an analysis result. FIG. 8 is a diagram showing an analysis result. FIG. 9 is a diagram showing an analysis result. FIG. 10 is a plan view showing an analysis model having a stiffening bead portion. FIG. 11 is a plan view showing an analysis model having a stiffening bead portion. FIG. 12 is a diagram showing an analysis result. FIG. 13 is a diagram illustrating an analysis result. FIG. 14 is a diagram illustrating an analysis result. FIG. 15 is a diagram illustrating an analysis result. FIG. 16 is a perspective view showing a welded structural member according to one embodiment of the present invention. FIG. 17 is a front view showing the base member and the joining members. FIG. 18 is a diagram in which the base member, the contact surface of the joining member, the weld bead portion, and the stiffening bead portion are projected in a direction perpendicular to the plane of the base member. FIG. 19 shows a projection of the base member of the welded structural member, the abutting surface of the joining member, the weld bead portion, and the stiffening bead portion according to another embodiment of the present invention in a direction perpendicular to the plane of the base member. FIG. FIG. 20 shows a projection of the base member of the welded structural member, the abutting surface of the joining member, the weld bead portion, and the stiffening bead portion according to another embodiment of the present invention in a direction perpendicular to the plane of the base member. FIG.

(Study by the present inventors)
The present inventors have conducted various studies in order to improve the fatigue strength of a welded structural member. Specifically, the fatigue strength of the welded structural member was examined by creating an analytical model of the welded structural member and performing FEM analysis.

  FIG. 1 is a perspective view showing an analysis model of a welding structural member. As shown in FIG. 1, the analysis model 10 includes a base member 12 extending in a first direction D1, a joining member 14 extending in a second direction D2 orthogonal to the first direction D1, and joining the base member 12 and the joining member 14. The welding bead portion 16 is provided. Each of the base member 12 and the joining member 14 has an open cross-sectional shape. In the following description, the first direction D1 is a left-right direction, and the second direction D2 is a vertical direction.

  FIG. 2 is a plan view showing a central portion of the analysis model 10 in the left-right direction. As shown in FIG. 2, in a plan view of the analysis model 10, the weld bead portion 16 is provided along the outer surface of the joining member 14. In the following description, a direction orthogonal to the first direction (left-right direction) D1 in a plan view is referred to as a front-rear direction.

  As shown in FIG. 1, a plurality of holes 12 a to 12 g are formed in the base member 12. Also, a hole 12h is formed at a position facing the hole 12g in the front-rear direction. The joining member 14 is formed with two holes 14a and 14b. As shown in FIGS. 1 and 2, both ends of the weld bead portion 16 protrude forward from the front ends 14 c and 14 d of the joining member 14.

  According to the research conducted by the present inventors, in the analysis model 10, when the joining member 14 is pulled upward, the boundary portions 18 a and 18 b between the front ends 14 c and 14 d of the joining member 14 and the weld bead portion 16 are obtained. It is known that the value of the maximum principal stress tends to increase in the vicinity of. For this reason, in the welded structural member having the same configuration as that of the analysis model 10, it is considered that cracks are likely to occur near the boundary portions 18a and 18b. Therefore, in order to improve the fatigue strength of the welded structural member, it is important to reduce the stress near the boundary portions 18a and 18b. From such a viewpoint, the present inventors have performed the analysis described below.

  The detailed configuration of the analysis model 10 will be described below.

(Base member)
Thickness: 2.6mm
Length in vertical direction (second direction D2): 50 mm
Length in left-right direction (first direction D1): 300 mm
Length in the front-rear direction (direction orthogonal to the first direction D1 and the second direction D2): 150 mm
Center distance between holes 12b and 12c: 230mm
Center distance between holes 12a and 12d: 230mm
Center distance between holes 12f and 12g: 230mm
Center distance between holes 12e and 12h: 230mm
Distance between the centers of the holes 12b and 12a: 100 mm
Distance between centers of holes 12c and 12d: 100 mm
Vertical distance from the upper surface 13 to the centers of the holes 12f, 12g, 12e, and 12h: 25 mm
Young's modulus: 210,000 MPa
Poisson's ratio: 0.3

(Joining members)
Thickness: 2.6mm
Vertical length: 80mm
Length in left and right direction: 70mm
Length in front and back direction: 80mm
Position of hole 14a: center of side wall 15a Position of hole 14b: center of side wall 15b Young's modulus: 210,000 MPa
Poisson's ratio: 0.3

(Weld bead part)
Width WB (see FIG. 2): 4.3 mm
Height (length in the vertical direction): 5.0 mm
Length LB (see FIG. 2) of a portion protruding forward from the front end of the joining member: 13.7 mm
Young's modulus: 210,000 MPa
Poisson's ratio: 0.3

  In the FEM analysis, fixing jigs (rigid bodies) are arranged in a plurality of holes 12a to 12h of the base member 12 to fix the base member 12, and a cylindrical member (rigid body) is inserted into the holes 14a and 14b of the joining member 14. Through the member, the joining member 14 was pulled upward (in a direction away from the base member 12) with a force of 2.0 kN. Then, in the analysis model 10, the maximum principal stress generated near the boundaries 18a and 18b was determined. As a result, the maximum value of the maximum principal stress was 830 MPa. Since the analysis model 10 has a symmetrical shape, the maximum principal stress generated near the boundary 18a is equal to the maximum principal stress generated near the boundary 18b.

Further, as shown in FIG. 3, the present inventors formed a pair of stiffening bead portions 20 extending in the front-rear direction on the upper surface 13 of the base member 12 outside the joining member 14 in the analysis model 10 described above. Then, similarly to the above analysis, the joining member 14 was pulled upward with a force of 2.0 kN. Then, the maximum principal stress generated near the boundaries 18a and 18b was determined. The present inventors have created several analytical model 10 the center position P ₁ stiffening bead portion 20 are different in the length L, and longitudinal direction in the longitudinal direction of the stiffening bead portion 20, the boundary portion 18a , 18b. The shape of the stiffening bead portion 20 was a rectangular parallelepiped, and the distance d in the left-right direction between the joining member 14 and the stiffening bead portion 20 was 5.3 mm.

  Hereinafter, a detailed configuration of the stiffening bead portion 20 will be described.

(Stiffening bead part)
Width W1 (length in the left-right direction): 5.0 mm
Height (length in the vertical direction): 2.0 mm
Length L1: 20.0 mm, 26.0 mm, 32.0 mm, 35.0 mm, 38.0 mm
Distance d: 5.3 mm
Young's modulus: 210,000 MPa
Poisson's ratio: 0.3

4, in the analysis model set the length L1 of the stiffening bead 20 to 32.0 mm, the maximum value of the maximum principal stress occurring in the vicinity of the center position _{P 1} and the boundary portion 18a, 18b of the stiffening bead 20 FIG.

In other figures 4 and later, the center position _{P 1} stiffening bead portion 20, the front end portion 14c of the joint member 14, shown at a distance in the longitudinal direction from the position _{P 0} of 14d. When the position P ₁ is shown by a positive value means that the position P ₁ is a position ahead of the position P _0, if the position P ₁ is shown in a negative value means that the position P ₁ is a rear position from the position P _0.

  As shown in FIG. 4, as a result of the analysis by the present inventors, when the length L1 of the stiffening bead portion 20 is set to 32.0 mm, the center position of the stiffening bead portion 20 is appropriately adjusted. By doing so, it can be seen that the maximum value of the maximum principal stress generated near the boundary portions 18a and 18b can be made sufficiently smaller than the maximum value (830 MPa) of the maximum principal stress in the analytical model having no stiffening bead portion. Was.

  FIG. 5 shows the relationship between the length L1 of the stiffening bead portion 20 of each analysis model and the value when the maximum value of the maximum principal stress is the lowest (minimum value of the maximum principal stress) in each analysis model. FIG. From the results shown in FIG. 5, it was found that by increasing the length L1 of the stiffening bead portion 20, the maximum value of the maximum principal stress generated near the boundary portions 18a and 18b can be reduced.

Based on the above results, the present inventors further studied in detail the relationship between the shape of the stiffening bead portion and the stress generated near the boundary portions 18a and 18b. Specifically, as shown in FIG. 6, instead of the above-described stiffening bead portion 20, an analysis model 10 in which a stiffening bead portion 30 whose width changes in the front-rear direction is created, and the same as the above-described analysis is performed. The analysis was performed under the following conditions. The stiffening bead portion 30 shown in FIG. 6 has a semi-elliptical column shape. In this analysis, the length L2 of the stiffening bead portion 30 and 32.0 mm, a height as 2.0 mm, the center position _{P 1} in the maximum width W2 and the longitudinal direction of the stiffening bead portion 30 is different analysis models 10, the maximum principal stress occurring near the boundary portions 18a and 18b was determined.

7 and 8 show the analysis results. Note that FIG. 7 is a diagram showing the relationship between the maximum value of the maximum principal stress occurring in the vicinity of the center position P ₁ and the boundary portion 18a, 18b of the stiffening bead portion 30. FIG. 8 is a diagram showing the relationship between the minimum value of the maximum maximum principal stress generated near the boundary portions 18a and 18b and the maximum width W2 of the stiffening bead portion 30.

As shown in FIG. 7, also in this analysis, by appropriately adjusting the center position of the stiffening bead portion 30, the maximum value of the maximum principal stress generated near the boundary portions 18a and 18b can be determined by using the stiffening bead portion. It was found that the maximum principal stress (830 MPa) in the analysis model that was not performed can be made sufficiently smaller. In this analysis, the center position _{P 1} of the stiffening bead portion 30, by positioning the rear in the range of 0~10mm from the front end portion 14c of the joint member 14, 14d position _{P 0} (see FIG. 6), the boundary portion 18a , 18b can be effectively reduced. In particular, the center position _{P 1} of the stiffening bead portion 30, the front end portion 14c, when the position _{P 0} of 14d located about 5mm behind the boundary portion 18a, the maximum value of the maximum principal stress occurring in the vicinity of 18b It was also found that the amount of reduction was large. Further, as shown in FIG. 8, it was also found that the stress reduction effect was improved by increasing the maximum width W2 of the stiffening bead portion 30.

  FIG. 9 is a diagram comparing an analysis result obtained when the stiffening bead portion 20 is formed and an analysis result obtained when the stiffening bead portion 30 is formed. In the above analysis, when forming the stiffening bead portion 20, the width W1 (see FIG. 3) is fixed to 5.0 mm, the length L1 (see FIG. 3) is changed, and the stiffening bead portion is formed. When forming 30, the length L2 (see FIG. 6) is fixed at 32.0 mm, and the maximum width W2 (see FIG. 6) is changed. Therefore, in order to unify the evaluation criteria, in FIG. 9, the volumes of the stiffening bead portions 20 and 30 are compared with the minimum value of the maximum value of the maximum principal stress generated near the boundary portions 18a and 18b.

  From the results shown in FIG. 9, when the volume of the stiffening bead portion is the same, the width of the stiffening bead portion is changed in the front-rear direction rather than increasing the length of the stiffening bead portion. It has been found that increasing the maximum width of the portion can effectively reduce the maximum value of the maximum principal stress generated near the boundary portions 18a and 18b. When forming a stiffening bead portion in expectation of a predetermined stress reduction effect, it is more preferable to form a stiffening bead portion whose width changes in the front-rear direction than to form a linear stiffening bead portion. However, the volume of the stiffening bead portion can be reduced. For this reason, when forming the stiffening bead portion whose width changes in the front-rear direction, it is possible to suppress an increase in weight of the welded structural member due to the formation of the stiffening bead portion.

  In the stiffening bead portion 30 whose width has been changed in the front-rear direction, the present inventors further have a position in the front-rear direction of a portion having the largest width (a portion indicating the maximum width W2), and a vicinity of the boundary portions 18a, 18b. We examined the relationship with the stress that occurs. Specifically, instead of the above-described stiffening bead portion 30, an analysis model 10 in which stiffening bead portions 30a and 30b shown in FIGS. 10 and 11 are formed is created and generated near the boundary portions 18a and 18b. The maximum principal stress was determined.

Incidentally, the stiffening bead portion 30a shown in FIG. 10 differs from the stiffening bead portion 30 described above, the width of the stiffening bead portion 30a is positioned P ₂ of the maximum portion serving (portion indicated by a broken line), the stiffening a point which is located 3mm forward from the center position P ₁ in the longitudinal direction of the bead portion 30a. Further, the stiffening bead portion 30b shown in FIG. 11 differs from the stiffening bead portion 30 described above, the width of the stiffening bead portion 30b is the position P ₂ of the maximum portion serving (portion indicated by a broken line), the stiffening a point which is located 3mm rearward than the center position P ₁ in the longitudinal direction of the bead portion 30a.

Note that, in the stiffening bead portions 30a and 30b shown in FIGS. 10 and 11, the portions ahead of the broken line and the portions behind the broken line each have a quarter elliptical shape in plan view. In this analysis, the stiffening bead portion 30a, the length L2 of 30b as 32.0 mm, the maximum width W2 as 7.5 mm, a stiffening bead portions 30a, by changing the center position _{P 1} in the longitudinal direction 30b, The maximum principal stress generated near the boundaries 18a and 18b was determined.

12 to 15 show the analysis results. Specifically, FIGS. 12 and 13 are diagrams showing stiffening bead portion 30a, the center position _{P 1} and the boundary portion 18a of 30b, the relationship between the maximum value of the maximum principal stress occurring in the vicinity of 18b. As shown in FIGS. 12 and 13, in this analysis, as in the case of forming the stiffening bead portion 30, a stiffening bead portion 30a, by appropriately adjusting the center position P ₁ of the 30b, the boundary portion 18a , 18b can be made sufficiently smaller than the maximum value (830 MPa) of the maximum principal stress in the analytical model having no stiffening bead portion.

  FIG. 14 is a diagram comparing the values when the maximum value of the maximum principal stress generated near the boundary portions 18a, 18b becomes the lowest in the analysis model in which the stiffening bead portions 30, 30a, 30b are formed. The analysis result of the stiffening bead portion 30 shown in FIG. 14 is an analysis result when the maximum width W2 is set to 7.5 mm. As shown in FIG. 14, the minimum value of the maximum value of the maximum principal stress generated near the boundary portions 18a and 18b was the lowest in the analysis model 10 in which the stiffening bead portion 30a was formed. From this result, it was found that the stress reduction effect was further improved by positioning the portion having the maximum width in the stiffening bead portion ahead of the center in the front-rear direction of the stiffening bead portion.

FIG. 15 is a diagram showing the relationship between the position of the portion where the width of the stiffening bead portions 30, 30a, 30b is maximum (the maximum width portion) and the maximum value of the maximum principal stress generated near the boundary portions 18a, 18b. is there. The portion where the width of the stiffening bead portion 30 is maximized, as shown in FIG. 6, equal to the center position P ₁ in the longitudinal direction of the stiffening bead portion 30. On the other hand, as shown in FIGS. 10 and 11, the position in the longitudinal direction of the portion stiffening bead portion 30a, the width of 30b is maximized, the position P _2.

In FIG. 15, the position of the maximum width portion of the stiffening bead portion, the front end portion 14c of the joint member 14, shown at a distance in the longitudinal direction from the position P ₀ of 14d. If the position of the maximum width portion is shown in a positive value, shown in a sense, and a negative value is the position of the maximum width portion that is the position of the maximum width portion is a position ahead of the position P ₀ it is if they will be, means that the position of the maximum width portion is the rearward position from the position P _0.

From the results shown in FIG. 15, it is preferable that the maximum width portion of the stiffening bead portion is located forward of the position P ₀ of the front ends 14 c and 14 d of the joining member 14 and behind the position of 5 mm. than the position of 15mm rearward from P ₀ has been found that it is preferably located in front.

  The present invention has been made based on the above findings.

(Description of Embodiment of the Present Invention)
Hereinafter, a welded structural member according to an embodiment of the present invention will be described with reference to the drawings. FIG. 16 is a perspective view showing a welded structural member according to one embodiment of the present invention.

  As shown in FIG. 16, the welding structural member 31 includes a base member 32 extending in a first direction D1, a joining member 34 extending in a second direction D2, and a welding bead portion 36 joining the base member 32 and the joining member 34. And a stiffening bead portion 38.

  In the example shown in FIG. 16, the second direction D2 is perpendicular to the first direction D1, but the second direction D2 may be inclined with respect to the first direction D1. That is, in the present embodiment, the joining member 34 is welded to the base member 32 so as to be perpendicular to the base member 32, but the joining member 34 is inclined so as to be inclined with respect to the base member 32. 32 may be welded. In the following, the first direction D1 is defined as a left-right direction, and the second direction D2 is defined as a vertical direction.

  FIG. 17 is a front view showing the base member 32 and the joining member 34. In FIG. 17, the illustration of the weld bead portion 36 and the stiffening bead portion 38 is omitted. Referring to FIGS. 16 and 17, base member 32 includes a first plate-shaped portion 42. The first plate portion 42 has a flat surface 42a. In the present embodiment, the base member 32 is constituted only by the first plate-shaped portion 42, but the base member has a portion having another shape in addition to the first plate-shaped portion 42 (for example, a columnar portion or Other plate-like portions). For example, the base member 32 may have the same shape as the base member 12 shown in FIG.

  As shown in FIG. 17, the joining member 34 includes a second plate-shaped portion 44. The second plate-shaped portion 44 has a butting surface 44a that abuts against the plane 42a of the base member 32, and a second surface D that extends from the butting surface 44a in a direction intersecting the plane 42a (a second direction D2 in the present embodiment). It has a first surface 44b and a second surface 44c. The first surface 44b and the second surface 44c are provided in parallel with each other. In the present embodiment, the joining member 34 is constituted only by the second plate portion 44, but the joining member has a portion having another shape in addition to the second plate portion 44 (for example, a columnar portion or Other plate-like portions). For example, the joining member may have the same shape as the joining member 14 shown in FIG.

  As a material of the base member 32 and the joining member 34, for example, various metal materials such as steel can be used. Specifically, for example, a steel plate having a tensile strength of 270 MPa or more can be used as a material of the base member 32 and the joining member 34. In particular, in order to sufficiently secure the strength of the welded structural member 31, for example, a high-strength steel plate (for example, a steel plate having a tensile strength of 590 MPa or more) is used as a material of the base member 32 and the joining member 34. In order to further improve the strength of the welded structural member 31, the tensile strength of the steel plate used as the base member 32 and the joining member 34 is preferably 780 MPa or more, more preferably 980 MPa or more, and more preferably 1180 MPa or more. It is more preferred that there be. Further, as the base member 32 and the joining member 34, a steel plate having a higher strength (for example, a steel plate having a tensile strength of 1500 MPa or more) can be used. In the present embodiment, a thin plate is used as the base member 32 and the joining member 34. The thickness of the first plate-shaped portion 42 of the base member 32 and the thickness of the second plate-shaped portion 44 of the joining member 34 are each 4.5 mm or less, and are approximately the same as the thickness of a steel plate used as a vehicle underbody member. is there. In the present embodiment, the thickness of each of the first plate-shaped portion 42 and the second plate-shaped portion 44 is set, for example, in a range of 0.8 mm to 4.5 mm.

  As shown in FIG. 16, the welding bead portion 36 joins the flat surface 42a of the base member 32 and the joining member 34. In the present embodiment, the base member 32 and the joining member 34 are fillet welded by the weld bead portions 36. The weld bead portion 36 is formed to extend along the edge of the butting surface 44a (see FIG. 17) on the first surface 44b side. The stiffening bead portion 38 is formed to extend substantially parallel to the weld bead portion 36 on the plane 42 a of the base member 32.

  In the present embodiment, the weld bead portion 36 is configured by one bead 36a, but may be configured by a plurality of beads. Further, in the present embodiment, the stiffening bead portion 38 is constituted by a plurality of (three in the present embodiment) beads 38a, but may be constituted by a single bead. The weld bead portion 36 and the stiffening bead portion 38 are each formed by, for example, arc welding. As the material of the weld bead portion 36 and the stiffening bead portion 38, various known welding materials can be used.

  FIG. 18 shows the base member 32, the abutting surface 44a of the joining member 34 (the second plate-shaped portion 44), the weld bead portion 36, and the stiffening bead portion 38 with respect to the flat surface 42a of the base member 32 (see FIG. 17). FIG. 6 is a diagram projected in a vertical direction (a second direction D2 in the present embodiment). In the present embodiment, as shown in FIG. 18, the front-back direction is defined for each end 46a, 46b of the abutting surface 44a in the extending direction of the weld bead portion 36. Specifically, when the end 46a of the abutting surface 44a is used as a reference, the direction in which the abutting surface 44a exists is viewed from the end 46a in the extending direction of the weld bead portion 36, and the opposite direction is the forward. And When the end portion 46b of the abutting surface 44a is used as a reference, the direction in which the abutting surface 44a exists when viewed from the end portion 46b in the direction in which the weld bead portion 36 extends is defined as rearward, and the opposite direction is defined as forward.

  Hereinafter, the positional relationship between the joining member 34, the weld bead portion 36, and the stiffening bead portion 38 will be described. The positional relationship is the positional relationship in the projection view shown in FIG.

  As shown in FIG. 18, the weld bead portion 36 extends between the butting surface 44a of the joining member 34 and the stiffening bead portion 38 in the front-rear direction along the butting surface 44a. More specifically, the weld bead portion 36 extends along the edge on the first surface 44b (see FIG. 17) side of the both edges of the abutting surface 44a in the left-right direction (first direction D1). I have. With reference to the end 46a of the abutting surface 44a, the weld bead 36 projects forward from the end 46a. Similarly, the weld bead portion 36 projects forward from the end 46b with reference to the end 46b of the abutment surface 44a. In the present embodiment, the length LB of a portion of the weld bead portion 36 that projects forward from the end 46a with respect to the end 46a is, for example, 20 mm or less. The same applies to the length of a portion of the weld bead portion 36 that projects forward from the end 46b with respect to the end 46b.

  The stiffening bead portion 38 is provided on the same side as the welding bead portion 36 when viewed from the abutting surface 44a in a direction (left-right direction) orthogonal to the extending direction (front-rear direction) of the welding bead portion 36. In the present embodiment, for example, the stiffening bead portion 38 is formed such that the length of the stiffening bead portion 38 in the front-rear direction is longer than the length of the stiffening bead portion 38 in the left-right direction. In the example shown in FIG. 18, the rear end of the stiffening bead 38 is located behind the end 46a with respect to the end 46a of the abutting surface 44a, and the front end of the stiffening bead 38 is , Is located forward of the end 46a. However, the rear end of the stiffening bead portion 38 may be located ahead of the end portion 46a, and the front end of the stiffening bead portion 38 may be located behind the end portion 46a.

  In the present embodiment, the stiffening bead 38 has a width (length in the left-right direction) that increases from the rear end of the stiffening bead 38 toward the front and then decreases toward the front end of the stiffening bead 38. It is formed so that. In the present embodiment, the plurality of beads 38a are provided such that the central portion in the front-rear direction of the stiffening bead portion 38 expands in a direction away from the weld bead portion 36 in the left-right direction.

In the present embodiment, the position P ₂ in the longitudinal direction of the part width in the stiffening bead portion 38 is maximum (maximum width portion) is positioned behind the position of 5mm forwardly from the end portion 46a of the abutting surface 44a Is preferred. Further, the position P ₂ is preferably positioned in front of the position P ₁ of the center in the longitudinal direction of the stiffening bead portion 38. Further, the center position _{P 1} in the longitudinal direction of the stiffening bead portion 38 is preferably from the end portion 46a of the abutting surface 44a is positioned in a range of 0~10mm backwards. The maximum width portion of the stiffening bead portion 38 is preferably provided near the end 46a.

  In addition, it is preferable that the rear end of the stiffening bead portion 38 is located, for example, forward of a position 40 mm rearward from the end 46a of the abutting surface 44a, and forward of a position 30 mm rearward from the end 46a. Is more preferable, and it is still more preferable to be located ahead of the position of 25 mm behind the end 46a. In this case, the present invention can be suitably used even if the region for disposing the stiffening bead portion 38 is limited. The length L in the front-rear direction of the stiffening bead portion 38 is set to, for example, 10.0 mm or more, and is preferably set to 14.0 mm or more. Further, it is preferable that the length L of the stiffening bead portion 38 be set to 50.0 mm or less. The maximum width (the maximum length in the left-right direction) of the stiffening bead portion 38 is set to, for example, 5.0 to 9.0 mm. In the present embodiment, the distance d between the stiffening bead 38 and the abutment surface 44a in the left-right direction is set to, for example, less than 16.0 mm. It is preferable that the distance d is set to 5.3 mm or more.

  In the welding structural member 31 according to the present embodiment, by forming the stiffening bead portion 38 as described above, one end of the second plate-shaped portion 44 in the extending direction of the welding bead portion 36 and the welding bead 36 are formed. In the vicinity of the boundary portion, generation of a large stress can be suppressed. Thereby, the fatigue strength of the welded structural member 31 can be improved.

  Further, in the present embodiment, if the stiffening bead portion 38 is formed at a position slightly deviated from the designated position (designated position) as long as the stiffening bead portion 38 is located near the end 46a of the abutting surface 44a. A similar stress suppression effect can be obtained. Further, in the present embodiment, a stiffening bead portion 38 may be formed outside the weld bead portion 36. As a result, the fatigue strength of the welded structural member 31 can be easily improved.

  In the above-described embodiment, the welded structural member 31 having one stiffening bead portion 38 has been described, but the number of the stiffening bead portions 38 is not limited to the above example. For example, as in the case of the welding structure member 31a shown in FIG. 19, the stiffening bead portion 38 may be similarly formed near the end portion 46b of the abutment surface 44a.

  In the above-described embodiment, the case where the joining member 34 has the second plate-shaped portion 44 extending linearly in a plan view has been described, but the shape of the second plate-shaped portion 44 is not limited to the above-described example.

  FIG. 20 shows a base member 32 of a welding structural member 31b according to another embodiment of the present invention, an abutting surface 44a of a joining member 34 (second plate-like portion 44), a welding bead portion 36, and a pair of stiffening bead portions. FIG. 18 is a diagram in which 38 is projected in a direction perpendicular to a plane 42 a of the base member 32 (see FIG. 16). The welding structure member 31b shown in FIG. 20 differs from the above-described welding structure member 31 in that the second plate-like portion 44 of the joining member 34 has a V-shape in plan view, and the welding bead portion 36 Are formed so as to extend in a V-shape in plan view, and have a pair of stiffening bead portions 38.

  In the present embodiment, as described above, since the second plate-shaped portion 44 has a V-shape in plan view, the abutting surface 44a also has a V-shape in plan view. The weld bead portion 36 is provided so as to extend in a V shape along the outer surface of the joining member 34 (the second plate-shaped portion 44).

  In the present embodiment, as shown in FIG. 20, the front-back direction is defined for each of a pair of ends (ends in the extending direction of the weld bead portion 36) of the abutting surface 44a in the same manner as in the above-described embodiment. A stiffening bead 38 is formed on each of the pair of ends. Accordingly, it is possible to suppress generation of a large stress in the vicinity of the boundary between the both ends of the second plate-shaped portion 44 and the weld bead portion 36. As a result, the fatigue strength of the welding structural member 31b can be improved.

  Although a detailed description is omitted, the front-back direction is defined for each end of the abutting surface even when the joining member has a U-shape in plan view, similarly to the above-described analysis model 10. Then, the present invention can be applied.

  According to the present invention, a welded structural member having excellent fatigue strength can be obtained. Therefore, the welded structural member according to the present invention can be suitably used, for example, as a constituent member of a vehicle body.

10 Analytical model 12, 32 Base member 14, 34 Joining member 16, 36 Weld bead portion 20, 30, 38 Stiffening bead portion 31, 31a, 31b Welding structural member

Claims (4)

A metal base member including a first plate-shaped portion having a flat surface and a thickness of 4.5 mm or less;
A second surface having a thickness of 4.5 mm or less, having a butting surface abutted against the plane of the base member, and a first surface and a second surface parallel to each other extending from the abutting surface in a direction intersecting the plane. Including a plate-shaped portion, a metal joining member,
A welding bead portion extending along the edge of the abutting surface on the first surface side and joining the flat surface of the base member and the joining member;
A stiffening bead portion formed on the plane of the base member and extending substantially parallel to the welding bead portion,
When the abutting surface of the joining member, the weld bead portion and the stiffening bead portion are projected in a direction perpendicular to the plane of the base member,
With reference to the end of the abutting surface in the extending direction of the weld bead portion, the direction in which the abutting surface exists as viewed from the end in the extending direction is the rear, and the opposite direction is the front,
The weld bead portion projects forward from the end of the abutment surface,
The stiffening bead portion is provided on the same side as the weld bead portion, as viewed from the abutting surface, in a direction perpendicular to the direction in which the weld bead portion extends,
The welded structural member, wherein a width of the stiffening bead portion increases from a rear end of the stiffening bead portion to a forward direction, and then decreases toward a front end of the stiffening bead portion.   The welding structural member according to claim 1, wherein a portion of the stiffening bead portion having a maximum width is located forward of a position 5 mm from the end of the abutting surface.   The welding structure member according to claim 1, wherein a center of the stiffening bead portion in the front-rear direction is located in a range of 0 to 10 mm rearward from the end of the abutment surface.   The welded structural member according to any one of claims 1 to 3, wherein a portion of the stiffening bead portion having a maximum width is located forward of a center of the stiffening bead portion in the front-rear direction.

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