JP2005169413A - Lap welded joint by fsw, and method of improving its fatigue strength - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lap welded joint by FSW (friction stir welding) in which stress concentration at the toe part or termination part in the welded part by FSW is relaxed, thus fatigue fracture is prevented to improve fatigue strength properties, and the fatigue life is improved. <P>SOLUTION: The lap welded joint by FSW is obtained by subjecting the platy upper member and lower member which are lapped to FSW by approaching a probe from the side of the upper member to form a welded part between the upper member and the lower member. The lap welded joint by FSW is formed in such a manner that, after the formation of the welded part, the upper member is worked so that it is gradually made thin to the side of the lower member toward the outermost tip part in the toe part or the termination part of the welded part to provide the thin part of the upper member. Thus, stress concentration in the toe part or the termination part of the welded part is relaxed to prevent the fatigue fracture, to improve the fatigue strength properties and to improve the fatigue life therein. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for improving the fatigue strength of a lap joint by friction stir welding (hereinafter referred to as “FSW” in the present specification and claims), and an FSW lap joint formed thereby.

  A conventional FSW lap joint will be described with reference to FIGS. 7A is a cross-sectional view of a lap joint with a conventional rivet, FIG. 7B is a cross-sectional view of a lap joint with FSW, and FIG. 8 is a cross-sectional view of a general FSW lap joint being joined. 9A and 9B are explanatory diagrams of problems of the conventional FSW lap joint, where FIG. 9A is a plan view of a “full wrap” state, FIG. 9B is a cross-sectional view taken along line FF in FIG. Is a plan view of the state of “partial wrap”, and (d) is a cross-sectional view taken along line GG in (c).

  Here, “full wrap” refers to a state where the upper member side of the plate-like members to be joined one above the other is continuous between the FSW portions adjacent to each other in the joining center line direction. “Wrap” refers to a state in which the upper member side is divided between adjacent FSW portions in the direction of the center line of bonding with respect to the lower member of the plate-like member to be joined one above the other. Denotes a member on the side accessed by a probe 21 described later as an FSW tool, and is used without any note in this sense in the present specification and claims.

Conventionally, the overlap bonding between plate members is not based on ordinary welding in order to avoid metal structural problems and deformation problems due to heat, particularly in the case of thin plates such as aluminum alloys such as aircraft members. The joining by the rivet 10 as shown in FIG. FIGS. 7A and 7B show a case where a flat plate portion of an aggregate such as a stringer 11 (or a frame (not shown)) of an aircraft member and an outer plate such as a skin 12 are overlapped and joined. (Note that as an aircraft member, a “frame” (not shown) is used as an aggregate that intersects with the stringer 11 and is larger than the stringer 11, and the flat plate portion of the frame may also be joined to the skin 12. In this specification, each time (Note is omitted, and the stringer 11 is described as an example, but the same applies when a frame (not shown) is joined to the skin 12 in place of the stringer 11).
However, in joining with the rivet 10, both the overlapping plate members (stringer 11 and skin 12 in FIG. 4) and the rivet 10 are not welded to each other and are still in an independent state, and the rivet hole 13 becomes a stress concentration source. There was a problem that fatigue damage was likely to occur from the rivet hole 13. Then, application of FSW which joins the overlapped board | plate materials by friction as shown in FIG.7 (b) is examined. Reference numeral 14 denotes a joint by FSW.

  Referring to FIG. 8, a general FSW lap joint will be described in brief. One side of a plate-like upper member 15 (for example, stringer 11) and a lower member 16 (for example, skin 12) made of stacked aluminum alloys (see FIG. 8) In the example shown, the probe 21 provided at the tip on the rotation center axis C of the rod tool 20 such as tool steel (SKD61) having a strength higher than that of the aluminum alloy is accessed from the upper member 15 side) and pressed while rotating at high speed T. , The members 15 and 16 are softened by friction between the probe 21 and the upper member 15 and further the lower member 16, and the probe 21 is pushed in as shown by a two-dot chain line in the figure. The surrounding softened members 15 and 16 are agitated and plastically flowed to obtain a joint 14 without a cavity.

  If a probe 21 having a height h larger than the thickness ta of the upper member 15 and smaller than the sum (ta + tb) of the thickness ta of the upper member 15 and the thickness tb of the lower member 16 is used, In the state where the shoulder portion 22 formed around the 20 probes 21 is in contact with the surface of the upper member 15, the joining portion 14 joins both the members 15 and 16 without the probe 21 penetrating the both members 15 and 16. It becomes. By moving the probe 21 in a direction perpendicular to the paper surface in FIG. 8 in a state where the probe 21 is rotated at a high speed while being pushed in, a joint portion 14 is formed in a portion after the probe 21 has passed in succession, and both along a predetermined joint center line. The members 15 and 16 are joined to obtain an FSW lap joint.

  FSW bonding is faster than rivet bonding and enables production costs to be reduced, and is particularly effective when bonding thin plate parts of aluminum alloys such as stringers and skins for aircraft members.

  However, as shown in FIG. 9, when the plate-like upper member 15 and lower member 16 are joined by FSW overlapping as described above, both the members 15 and 16 are joined by the joint portion 14. There was a problem.

  Assuming that the load L along the joining center line X is applied as in the skin 12 of the aircraft member, in the case of the full wrap of FIGS. 9A and 9B, the upper member 15 and the lower member 16 are both joined. Although it continues in the direction of the center line X, the joint portion 14 is interrupted at the start end portion 31 and the end portion 32, so that the rigidity changes rapidly and stress concentration occurs.

  In particular, in the end portion 32, a hole (typically, a concave hole that communicates with the upper and lower members 15 and 16, but the lower member 16 does not penetrate) 33 is formed in the trace of the probe 21 being extracted. First, critical stress concentration occurs in the surrounding area, and fatigue fracture Z2 occurs in the upper and lower members 15 and 16 starting from that portion.

  9C and 9D, the lower member 16 is continuous, but the upper member has an upper member 15a having one joint 14a and an upper member 15b having the other joint 14b. Since it is divided into the members 15b, only the lower member 16 is provided between the end portion 32 of one joint portion 14a and the start end portion 31 of the other connection portion 14b, and the rigidity changes sharply at the end portion 32 and the start end portion 31. To do. For this reason, stress concentration occurs around the punched hole 33 of the terminal end portion 32 and at the start end portion 31.

  In this case, normally, critical stress concentration first occurs on the starting end portion 31 side of the upper member 15b, and fatigue failure Z1 occurs starting from that portion. This is presumably because the joint portion 14a around the punched hole 33 is concave, whereas the start end portion 31 of the joint portion 14 is convex, so that the stress concentration is increased at the leading edge 31a.

  As described above, the FSW lap joint has many merits, but measures are required for stress concentration at the start and end portions of the FSW joint and fatigue failure resulting therefrom. As shown in FIG. 12, when the strength against the load on the joint of the upper and lower members is required, the problem of stress concentration and the improvement of the fatigue strength characteristics have been demanded.

  For example, regarding the problem that the hole after extracting the probe 21 at the terminal end of the FSW overlapped joint becomes a stress concentration location, Japanese Patent No. 3045682 (Patent Document 1) discloses a probe near the joint terminal. Although a technique that does not gradually form a pull-out probe pull-out hole is shown, a rod tool having a mechanism for pulling up the probe is required, which complicates the joining apparatus and causes restrictions on the joining operation and process. In the FSW lap joint, there has been no method for solving the problems of stress concentration and fatigue strength at the joint start and end portions and fatigue strength.

Japanese Patent No. 3045682 (page 4, FIG. 4, FIG. 5)

  In the present invention, the production speed of the FSW lap joint is high and the manufacturing cost can be reduced. In particular, in order to take advantage of the advantage that is effective when joining thin plate portions, the joining start and end portions of the conventional FSW are used. It is an object of the present invention to provide a method for improving the fatigue strength of an FSW lap joint and an FSW lap joint that eliminate the problems of stress concentration and fatigue strength, prevent fatigue failure, improve fatigue strength characteristics, and improve fatigue life. To do.

  The present invention has been made to solve the above problems, and provides the following means (1) to (5), and will be described below in the order of the claims.

  (1) As the first means, an FSW lap joint that forms a joint between the upper member and the lower member by performing FSW by accessing the probe from the upper member side with the upper and lower members of the stacked plate-like members. Then, after forming the joined portion, the upper member is gradually thinned toward the lower member side toward the foremost end portion or the end portion of the joined portion to form a thin portion of the upper member. A method for improving the fatigue strength of an FSW lap joint is provided.

  (2) As the second means, in the fatigue strength improving method of the FSW lap joint of the first means, the thin wall portion is provided at both the start end portion and the end portion, and the FSW lap joint is characterized in that Provide a method for improving fatigue strength.

  (3) Further, as a third means, FSW superposition is performed in which a probe is accessed from the upper member side of the superposed plate-like upper member and lower member to perform FSW and a joint is formed between the upper member and lower member. In the joint, after the joint is formed, the probe is pressed against the probe hole formed at the end of the joint by reducing the rotational speed and the pressing force from the time of the FSW. Provided is a method for improving the fatigue strength of an FSW lap joint, characterized in that the inner surface of the punched hole is smoothed by deepening and expanding.

  (4) As a fourth means, in an FSW lap joint that forms a joint between the upper member and the lower member by performing FSW by accessing the probe from the upper member side to the upper and lower members of the stacked plate-like members A method for improving the fatigue strength of an FSW lap joint is provided in which the upper member and the lower member are rivet-bonded adjacent to the start or end of the joint after forming the joint.

  (5) As a fifth means, in the FSW lap joint where the probe is accessed from the upper member side of the superposed plate-like upper member and lower member to perform FSW and a joint is formed between the upper member and the lower member After the joint is formed, a through hole that penetrates the upper member and the lower member is provided at a position of the punched hole of the probe formed at the terminal portion of the joint, and the upper member and the lower member are provided in the through hole. Provided is a method for improving the fatigue strength of an FSW lap joint, characterized by rivet joining a member.

  (6) As a sixth means, an FSW lap joint is used to access the probe from the upper member side of the superposed plate-like upper and lower members and perform FSW to form a joint between the upper and lower members. An FSW lap joint is provided, which is formed by the method for improving fatigue strength of an FSW lap joint according to any one of the first to fifth means.

  (7) As a seventh means, in the FSW lap joint of the sixth means, the upper member is a flat plate portion of an aircraft member aggregate, and the lower member is an outer plate of the aircraft member. An FSW lap joint is provided.

  (1) According to the invention of claim 1, the fatigue strength improving method for the FSW lap joint is achieved by accessing the probe from the upper member side to the upper and lower members of the stacked plate. In the FSW lap joint where FSW is performed to form a joint portion between the upper member and the lower member, after the joint portion is formed, the upper member is directed toward the forefront at the start end portion or the end portion of the joint portion. Since the thin part of the upper member is provided by being processed so as to be gradually thinned toward the lower member side, the upper member is directed toward the forefront at the start or end of the joint of the FSW lap joint. Since the processed start end or processed end is provided with a thin part of the upper member that is processed to gradually become thinner on the lower member side, the rigidity change at the start end or end becomes smooth and stress Relaxed concentration , Fatigue strength characteristics are prevented from fatigue failure is improved, thereby improving the fatigue life of the FSW superposition joint.

  (2) According to the invention of claim 2, in the fatigue strength improving method for an FSW lap joint according to claim 1, since the thin portion is provided in both the start end portion and the end portion, the start end Since the same fatigue strength improvement is made at both the end portion and the end portion, the effect of the invention of claim 1 can be more effectively exhibited in the FSW lap joint of the partial wrap.

  (3) According to the invention of claim 3, the fatigue strength improving method of the FSW lap joint is carried out by performing FSW by accessing the probe from the upper member side of the superposed plate-like upper member and lower member and lowering the upper member and lower member. In an FSW lap joint that forms a joint between members, after forming the joint, the rotational speed and pressing force are applied to the punched hole of the probe formed at the terminal end of the joint from the time of the FSW. Since the inner surface of the hole in the probe is smoothed by pressing the probe down and pressing the probe to deepen and expand the hole, the inner surface of the hole in the probe is smoothed. Is generated, and the punched hole is processed to be deep and expanded, so that compressive residual stress is added, resistance to load is improved, and fatigue strength characteristics at the end of the joint are remarkably improved. , F Fatigue life of the W superposition joint is improved.

  (4) According to the invention of claim 4, the fatigue strength improving method of the FSW lap joint is carried out by performing FSW by accessing the probe from the upper member side of the stacked plate-like upper member and lower member and lowering the upper member and lower member. In the FSW lap joint for forming a joint portion between members, the upper member and the lower member are rivet-joined adjacent to the start end portion or the end portion of the joint portion after the joint portion is formed. Therefore, the joint load at the start and end portions can be distributed to the separately added rivets, stress concentration can be reduced, fatigue strength characteristics are improved, and the fatigue life of the FSW lap joint is improved.

  (5) According to the invention of claim 5, the fatigue strength improving method of the FSW lap joint is carried out by performing FSW by accessing the probe from the upper member side of the overlapped plate-like upper member and lower member and performing the FSW. In an FSW lap joint that forms a joint portion between members, after the joint portion is formed, the upper member and the lower member are penetrated to a position of a hole in the probe formed at a terminal portion of the joint portion. Since a through hole is provided and the upper member and the lower member are rivet-bonded in the through hole, the upper and lower members of the upper and lower members are blocked by closing the probe hole at the end of the joint. By effectively increasing the effective area and reducing the change in rigidity, stress concentration is reduced and fatigue failure is also eliminated from the inner surface of the punched hole. Together Fatigue life of the causes joints can be improved.

  (6) According to the invention of claim 6, the FSW overlap joint is joined between the upper member and the lower member by performing FSW by accessing the probe from the upper member side of the upper plate member and the lower member which are overlapped. Since the FSW lap joint is formed by the method for improving fatigue strength of an FSW lap joint according to any one of claims 1 to 5, the FSW lap joint is formed. In addition, the FSW lap joint has the operational effects of any one of claims 1 to 6.

  (7) According to the invention of claim 7, in the FSW lap joint according to claim 6, the upper member is a flat plate portion of an aggregate of an aircraft member, and the lower member is an outer plate of the aircraft member. By virtue of the effect of the invention of claim 6, the stress concentration can be reduced and the fatigue can be reduced in the FSW overlapped joint structure of the aggregate such as a stringer or frame as an aircraft member and the outer plate such as a skin. An FSW lap joint with high strength and high reliability can be obtained.

  Examples 1 to 4 will be described below as the best mode for carrying out the present invention.

  The FSW lap joint according to Example 1 of the present invention and its fatigue strength improving method will be described with reference to FIGS. FIG. 1A is a cross-sectional view before formation of the FSW lap joint of this embodiment, FIG. 1B is a plan view taken along the line AA in FIG. 1A, and FIG. 1C is the FSW lap of this embodiment. It is sectional drawing after formation of a mating joint, (d) is a BB arrow top view in (c). 2 (a) to 2 (f) are comparative explanatory views of the occurrence of stress concentration between the FSW lap joint of this embodiment and the conventional example, and FIG. 3 is a fatigue life comparison graph of each example of FIG.

  First, as shown in FIGS. 1A and 1B, the FSW lap joint of the present embodiment is a plate-like upper member 15 such as a superposed aluminum alloy as described in FIGS. By accessing the probe 21 from one side (for example, the upper member 15 side in the drawing) of the stringer 11 (for example, the stringer 11) and the lower member 16 (for example, the skin 12), the upper member 15 is pressed while rotating at high speed. The joint 14 is formed between the lower member 16 and the lower member 16. In the drawing, the hole 33 of the probe 21 is not shown, but FIG. 1 shows the start end 31 and the end 32 of the joint 14 in common.

  After the joint 14 is formed, the FSW lap joint according to the present embodiment further includes the start end 31 and the end 32 of the joint 14 as shown in FIGS. 1 (c) and 1 (d). The upper member 15 is processed so as to gradually become thinner toward the lower member 16 toward 31a and 32a, and the thin portion 15 ′ of the upper member 15 is provided to form a processed start end portion 31 ′ and a processed end portion 32 ′. It is. The form of gradually decreasing the thickness is not limited to the stepped slope as shown in the figure, and may be a curved surface.

  Although it is more effective to reduce the thickness ta ′ of the thin portion 15 ′ at the leading edges 31a and 32a, the thicknesses of the upper member 15 and the lower member 16 are, for example, ta and tb = 2 mm, respectively, from the precision of machining. In the case of thickness, ta ′ may be about 0.25 mm or less.

  The characteristics and effects of the FSW lap joint according to this embodiment will be described in comparison with the conventional FSW lap joint. FIGS. 2 (a) and 2 (b) show what is shown in FIGS. 9 (c) and 9 (d). It is a partial wrap FSW lap joint similar to that shown, and the lower member 16 is continuous, but the upper member is divided into an upper member 15a having one joint 14a and an upper member 15b having the other joint 14b. As described above, only the lower member 16 is provided between the end portion 32 of one joint portion 14a and the start end portion 31 of the other connection portion 14b as described above, and the rigidity at the end portion 32 and the start end portion 31 is sharp. To change. Therefore, stress concentration occurs around the hole 33 of the terminal end portion 32 and the start end portion 31, and critical stress concentration first occurs on the start end portion 31 side of the joint portion 14b. The fatigue fracture Z1 occurs starting from that portion. The fatigue life in that case is as illustrated in the graph “(1) As FSW” in FIG. 3.

  2 (c) and 2 (d) show a machined starting end obtained by thinning the starting end 31 as shown in FIG. 1 in order to prevent fatigue fracture Z1 of the starting end 31 which has become critical in the conventional partial lap. The portion 31 ′ is used. In this case, at the starting end portion 31, the upper member 15b is processed so as to gradually become thinner toward the lower member 16 toward the most distal end 31a, and a thin portion 15 ′ (see FIG. 1) of the upper member 15b is provided. Since the finished start end portion 31 ′ is formed, the rigidity change at the start end portion 31 becomes smooth, stress concentration is relaxed, and fatigue failure Z 1 is prevented.

  However, the stress concentration around the hole 33 in the end portion 32 becomes critical, and fatigue failure Z2 occurs starting from that portion. In this case, the fatigue life is as illustrated in the graph of “(2) Start end machining” in FIG. 3, and is improved from the fatigue life of “As is FSW”.

  2 (e) and 2 (f) show this embodiment in which the end portion 32 is also processed into a processed end portion 32 'which is thinned as shown in FIG. 1 in order to prevent fatigue fracture Z2 of the end portion 32. This is an example FSW lap joint.

  In the case of the FSW lap joint of the present embodiment, the upper member 15a is processed so as to gradually become thinner toward the lower member 16 toward the distal end 32a of the end portion 32, and the thin portion 15 ′ ( 1) is formed, the change in rigidity at the end portion 32 becomes smooth, stress concentration is relaxed, and fatigue failure Z2 is prevented.

  In the processed end portion 31 ′ or the processed end portion 32 ′, the fatigue failure Z3 finally occurs. The fatigue life in this case is as illustrated in the graph of “(3) Both end processing” in FIG. It is further improved from the fatigue life of "(2) Start end machining".

  Therefore, as shown in FIG. 3, according to the FSW lap joint of this embodiment and the fatigue strength improving method thereof, as compared with the graphs of “both end machining” and “rivet” in FIG. The lap joint having a fatigue strength not inferior to that of the lap joint is obtained, and the fatigue strength characteristics are remarkably improved and the fatigue life is improved as compared with the conventional FSW lap joint.

  In this embodiment, both the start end portion 31 and the end portion 32 are provided with the processed start end portion 31 ′ and the processed end portion 32 ′ each having the thin wall portion 15 ′. You may combine using another fatigue strength improvement means. However, in the partial wrap FSW lap joint, since the same fatigue strength improvement is made at both the start end portion 31 and the end portion 32, the fatigue strength characteristics are more effectively improved. It is preferable to provide a processed end portion 31 ′ and a processed end portion 32 ′ in each of the parts 32.

  Based on FIG. 4, the FSW lap joint according to the second embodiment of the present invention and the fatigue strength improving method thereof will be described. FIG. 4A is a longitudinal sectional view of the FSW lap joint of the present embodiment, and FIG. 4B is a fatigue life comparison graph of the present embodiment.

  The FSW lap joint of the present embodiment is FSW lap joint as described with reference to FIGS. 8 and 9, but after joining by FSW and the temperature is lowered, as shown in FIG. The probe 21 of the rod tool 20, that is, the probe 21 of the rod tool 20 is pressed against the punched hole 33 of the terminal end portion 32 by reducing the rotational speed and the pressing force from the time of FSW, and rotates while suppressing heat generation. In this way, the inner surface is smoothed to form a processed punch hole 33 '.

  In order to suppress the heat generation, for example, ironing is performed at about 60 rpm for the probe rotation speed of about 600 rpm at the time of bonding, and at a pressing force P ′ of about 20 to 30 kg for the pressing force P of about 700 kg at the time of bonding. .

  Therefore, according to the FSW lap joint and the fatigue strength improving method of the present embodiment, the inner surface of the processed punch hole 33 'is smoothed, so that the generation of cracks is prevented.

  Further, since the processed punch hole 33 ′ is processed so as to expand the punch hole 33 deeply, a compressive residual stress is added, and a resistance against a load is improved. For example, when the thickness ta of the upper member 15 is 2 mm, the thickness tb of the lower member 16 is 2 mm, and the depth of the punched hole 33 remains 2.3 mm, the depth of the punched hole 33 ′ processed by ironing The depth of the hole 33 is increased to 2.4 mm to 2.5 mm, and the punched hole 33 is tapered.

  FIG. 4B shows “(1) FSW as it is (depth 2.3 mm)” in the conventional example, “(2) Ironing (depth 2.4 mm)” and “(3) Ironing” in this example. It is a comparative example of the fatigue life of (depth 2.5 mm), and it can be seen that it has a fatigue strength close to rivet bonding. Therefore, in the FSW lap joint of this embodiment, the fatigue strength characteristics of the terminal portion 32 are remarkably improved and the fatigue life is improved as compared with the conventional example.

  Since the present embodiment improves the fatigue strength of the end portion 32, it can easily and effectively exhibit the effect in a full-wrap FSW lap joint where the fatigue strength of the end portion 32 becomes critical. If implemented together with other means for improving fatigue strength at the starting end portion 31, an effect can be effectively obtained even in an FSW lap joint of a partial wrap.

  Based on FIG. 5, the FSW lap joint according to Example 3 of the present invention and its fatigue strength improving method will be described. Fig.5 (a) is a top view of the FSW overlap joint of a present Example, (b) is a top view of the other form of a present Example.

  The FSW lap joint of this embodiment is FSW lap jointed as described with reference to FIGS. 8 and 9, but after the joint portions 14a and 14b (14) are formed, it is shown in FIG. 5 (a). As described above, joining by the rivet 10 is further added to a position adjacent to the starting end portion 31 or the terminal end portion 32 in the joining center line X direction.

  Moreover, as another aspect, after joining part 14a, 14b (14) is formed, as shown in FIG.5 (b), it is further laterally from the joining centerline X from the starting end part 31 or the terminal part 32. The joining by the rivet 10 is added to the position which is separated and adjacent.

  In both cases (a) and (b), the joining with the rivet 10 is shown at one place, but a plurality of joining may be provided. FIG. 5 shows a partial wrap FSW lap joint, but, of course, the same can be applied to a full wrap FSW lap joint.

  According to the FSW lap joint of this embodiment and the method for improving fatigue strength thereof, the load on the joint portions 14a and 14b (14) at the start end portion 31 and the end end portion 32 is distributed to the separately added rivet 10 to concentrate stress. The fatigue strength characteristics can be improved and the fatigue life can be improved.

  In particular, although not shown, when the stringer 11 (upper member 15) of the aircraft member and the skin 12 (lower member 16) are joined, a frame connecting the stringers 11 may be provided so as to intersect with the stringer 11. However, in that case, if the three members added to the skin 12 and the stringer 11 are rivet joined on the extension line of the FSW joint between the stringer 11 and the skin 12, the optimization of the arrangement of each member and the fatigue of the FSW lap joint It is possible to achieve both improvement in strength characteristics.

  Based on FIG. 6, the FSW lap joint according to Example 4 of the present invention and its fatigue strength improving method will be described. FIG. 6 is a plan view of the FSW lap joint of the present embodiment.

  The FSW lap joint of this embodiment is FSW lap jointed as described in FIGS. 8 and 9, but after the joint portion 14 is formed, as shown in FIG. A through-hole 34 that penetrates the upper and lower members 15, 16 is provided at the position of the punching hole 33, and joining by the rivet 10 is added to the through-hole 34.

  According to the FSW lap joint and the fatigue strength improving method of this embodiment, the upper member 15 and the lower member 16 are closed together with the hole 33 in the end portion 32, and the effective area of the upper and lower members 15, 16 is substantially increased. By increasing and reducing the change in rigidity, stress concentration is reduced, fatigue failure is also eliminated from the inner surface of the punched hole 33, the fatigue strength characteristics of the end portion 32 are improved, and the fatigue life is improved. It becomes.

  Since the present embodiment improves the fatigue strength of the end portion 32, it can easily and effectively exhibit the effect in a full-wrap FSW lap joint where the fatigue strength of the end portion 32 becomes critical. If implemented together with other means for improving fatigue strength at the starting end portion 31, an effect can be effectively obtained even in an FSW lap joint of a partial wrap.

  As described above, according to the FSW lap joint and the fatigue strength improving method of each embodiment of the present invention, the fatigue strength characteristics are improved and the fatigue life of the FSW lap joint is improved. In the FSW superposition joining structure of the stringer 11, the aggregate such as the frame and the outer plate such as the skin 12, the load applied to the outer plate such as the skin 12, the outer plate such as the skin 12 and the stringer 11, the aggregate such as the frame, etc. The stress concentration can be relaxed even with respect to the load applied during the period, and a FSW lap joint with high fatigue strength and high reliability can be obtained.

  Although the present invention has been described with reference to the illustrated embodiments, the present invention is not limited to the above-described embodiments, and various modifications may be made to the specific configuration and structure within the scope of the present invention. Not too long.

  For example, in the above-described embodiment, the combination of the stringer 11 and the skin 12 of the aircraft member is described as an example of the combination of the upper member 15 and the lower member 16, but as described above, the combination of the frame and the skin 12 (not shown) of the aircraft member as well. It is the same. The FSW lap joint and the method for improving fatigue strength of the present invention are not limited to the aircraft members described above, but can be applied to general lap joints using FSW and exhibit their effects.

  In addition, although the names “upper member” and “lower member” are used in each embodiment, they are intended to relatively distinguish both members that are overlapped and joined together, and limit the upper and lower positions in the arrangement. Not what you want.

(A) is sectional drawing before formation of the FSW overlap joint which concerns on Example 1 of this invention, (b) is an AA arrow top view, (c) concerns on a present Example. It is sectional drawing after formation of a FSW overlap joint, (d) is a BB arrow top view in (c). (A)-(f) is a comparison explanatory drawing of stress concentration generation | occurrence | production of the FSW overlap joint of a present Example, and a prior art example. It is a fatigue life comparison graph of each example of FIG. (A) is a longitudinal cross-sectional view of the FSW lap joint according to Example 2 of the present invention, and (b) is a fatigue life comparison graph of this example. (A) is a top view of the FSW overlap joint which concerns on Example 3 of this invention, (b) is a top view of the other form of a present Example. It is a top view of the FSW overlap joint which concerns on Example 4 of this invention. (A) is sectional drawing of the lap joint by the conventional rivet, (b) is sectional drawing of the lap joint by FSW. It is sectional drawing of the common FSW lap joint during joining. It is explanatory drawing of the problem of the conventional FSW lap joint, (a) is a top view of the state of "full wrap", (b) is a sectional view taken along the line F-F in (a), (c) is "partial" The top view of the state of "wrap", (d) is GG arrow sectional drawing in (c).

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Rivet 11 Stringer 12 Skin 13 Rivet hole 14 Joint part 14a, 14b Joint part 15 Upper member 15a, 15b Upper member 15 'Thin part 16 Lower member 16a, 16b Lower member 20 Rod tool 21 Probe 22 Shoulder part 31 Starting end part 31a Tip 31 'Processed start end 32 End part 32b Cutting edge 32' Processed end part 33 Punched hole 33 'Processed punched hole 34 Through hole X Joint center line Z1, Z2, Z3 Fatigue failure

Claims (7)

  In the FSW overlapped joint that forms the joint between the upper member and the lower member by accessing the probe from the upper member side by accessing the probe from the upper member side to the overlapped plate-like upper member and lower member, after forming the joint, An FSW lap joint, wherein the upper member is processed so as to be gradually thinned toward the lower member side toward the foremost end portion or the end portion of the joint portion, and a thin portion of the upper member is provided. Fatigue strength improvement method.   2. The method for improving fatigue strength of an FSW lap joint according to claim 1, wherein the thin wall portion is provided at both the start end portion and the end portion.   In the FSW overlapped joint that forms the joint between the upper member and the lower member by accessing the probe from the upper member side by accessing the probe from the upper member side to the overlapped plate-like upper member and lower member, after forming the joint, The probe hole formed in the terminal end of the joint is reduced in number of rotations and pressing force from the time of the FSW, and the probe is pressed to deepen and enlarge the hole. A method for improving the fatigue strength of an FSW lap joint, wherein the inner surface of the FSW is smoothed.   In the FSW overlapped joint that forms the joint between the upper member and the lower member by accessing the probe from the upper member side by accessing the probe from the upper member side to the overlapped plate-like upper member and lower member, after forming the joint, A method for improving the fatigue strength of an FSW lap joint, wherein the upper member and the lower member are rivet-joined adjacent to the start end or the end of the joint.   In the FSW overlapped joint that forms the joint between the upper member and the lower member by accessing the probe from the upper member side by accessing the probe from the upper member side to the overlapped plate-like upper member and lower member, after forming the joint, A through hole penetrating the upper member and the lower member is provided at a position of a hole in the probe formed at a terminal portion of the joint portion, and the upper member and the lower member are rivet-joined in the through hole. A method for improving the fatigue strength of an FSW lap joint.   An FSW lap joint in which a probe is accessed from the upper member side of the superposed plate-like upper member and lower member to perform FSW to form a joint portion between the upper member and the lower member. 5. An FSW lap joint, which is formed by the method for improving fatigue strength of an FSW lap joint according to any one of 5 above. The FSW lap joint according to claim 6, wherein the upper member is a flat plate portion of an aggregate of an aircraft member, and the lower member is an outer plate of the aircraft member.

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