JP2009047251A - Metal plate fastening method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metallic plate fastening method capable of enhancing its fatigue strength by a simple method in a fastening structure for fastening a metallic plate to an object for fastening. <P>SOLUTION: In the metallic plate fastening method, the temporary fastening is repeated a plurality of time by using a peening tool 10 to plates 22, 24 prior to the final bolt fastening. The peening tool 10 is constituted by arranging a plurality of steel balls 16 on one side of the plate. The temporary fastening is performed preferably by changing the arrangement of the steel balls 16 by turning the peening tool 10 during the repetition. The treatment effect similar to that subjected to the so-called shot peening to each plate is thus obtained. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fastening method for fastening a metal plate material to a fastening object.

  A vehicle frame is configured by assembling left and right side members extending in the front-rear direction of the vehicle body and a plurality of cross members that bridge these in the vehicle width direction, and fastening members such as bolts and rivets are used for the assembly. There are many places where it is done. FIG. 5 is a diagram conceptually illustrating an example of an attachment structure using such a fastening member. FIG. 2A shows a perspective view of the mounting structure, and FIG. 2B shows a plan view thereof.

  FIG. 6A illustrates a structure in which an interposed member 102 such as a bush collar or a cast part is sandwiched between two plates 104 and 106 made of a metal plate and fastened with a bolt 108 and a nut 110. Has been. In such a mounting structure, for example, when a bending stress is applied to the fastening portion by applying a load that bends both plates, a crack 112 may occur in the plate 104 as shown in FIG. There is. That is, it is assumed that stress concentration occurs on the plate 104 due to the edge of the bolt 108, and that fatigue failure is caused by the repeated action of the stress.

In order to prevent such fatigue failure, for example, a method of applying a preload to a stress concentration site to be fastened and strengthening the fatigue strength by the residual stress can be considered. For example, Cited Document 1 discloses a method of applying a preload in the direction of external force action of a member as a method for strengthening a member having a stress concentration portion such as a rivet hole or a bolt hole. In addition, the cited document 2 discloses a method of compressing the sheet material before the formation of the hole in order to improve the fatigue life of the hole or notch formed in the sheet material.
JP 2000-296782 A JP 7-700773

  However, when such a method is applied, a relatively large apparatus such as a hydraulic press machine is required to apply the preload due to the tensile load or the compressive load. Such a problem can occur not only in a vehicle frame but also in a fastening structure that fastens a metal plate material that is easily affected by bending stress to a fastening target.

  The present invention has been made in view of such a problem, and an object thereof is to increase the fatigue strength of a fastening structure for fastening a metal plate material to a fastening object by a simple method.

  In order to solve the above-described problems, an aspect of the present invention relates to a fastening method for fastening a metal plate material to a fastening target. In this fastening method, prior to the fastening, a peening jig in which a plurality of protrusions are provided in a scattered manner on one surface is disposed with the plurality of protrusions facing the periphery of the fastening portion of the metal plate material. A peening process that partially plastically deforms the surface around the fastening portion of the metal plate material by fastening the temporary fastening member with a peening jig sandwiched between the tool installation step and the metal plate material, and fastening of the temporary fastening member A jig releasing step of releasing the peening jig and releasing a peening jig, and a fastening step of fastening the metal plate material to the fastening object using an actual fastening member.

  Here, the material and structure of the “fastening target” are not particularly limited. The “projection” of the peening jig may be formed integrally with the jig, or may be joined to the surface of the jig by welding or another joining method. In addition, the “spot-like” referred to here can include both cases where they are arranged in a line and randomly arranged. “Actual fastening member” means an original fastening member that fastens and holds a metal plate material to be fastened, and “temporary fastening member” means a temporary fastening member that is used particularly in a peening process. It may consist of members. According to this aspect, the peening process using the peening jig and the temporary fastening member is performed prior to the fastening of the actual fastening member. In other words, by disposing the protrusions of the peening jig opposite the periphery of the fastening part of the metal plate material and fastening the temporary fastening member, the local compressive stress due to the individual protrusions is scattered on the surface around the fastening part. Give. Thereby, the work hardening accompanying plastic deformation is generated in the surface layer around the fastening portion of the metal plate material. That is, an effect similar to so-called shot peening can be generated by pressing the protrusion formed on the peening jig against the metal plate material. Thereby, residual compressive stress is generated around the fastening portion of the metal plate material, and the fatigue strength of the portion is increased. As a result, even if bending stress is applied after the metal plate material is fastened, fatigue failure near the fastening portion can be prevented or suppressed. In particular, it is useful in that the fatigue strength can be increased by a simple method of temporary fastening with a peening jig interposed therebetween.

  In the peening process, it is preferable to repeat the fastening by the temporary fastening member a plurality of times. When the position of the protrusion is changed, for example, by rotating the peening jig during the repetition, the portion where the residual compressive stress is generated in the metal plate material can be made more uniform, and as a result, the fatigue strength around the fastening portion Can be further increased. In other words, an effect closer to shot peening can be obtained.

  The plurality of protrusions may be composed of a plurality of steel balls joined to one surface of the peening jig. The steel ball may be partially embedded in one surface of the peening jig, or may be joined by welding or the like. By forming the protrusions with spherical hard spheres, the contact state with the surface of the metal plate becomes close to point contact, and the surface pressure can be further increased. As a result, the surface can be work hardened efficiently.

  More specifically, each fastening member may be a bolt and a nut. Further, the peening jig is formed with an insertion hole for inserting a bolt at a position corresponding to the fastening portion of the metal plate material, and protrudes in a range wider than the projection range of the bolt head around the insertion hole. May be provided. When fastening the bolt, the shaft is passed through the insertion hole of the peening jig and joined to the nut.

  Thus, by arranging the protrusions in a range wider than the projected area of the bolt head, it is possible to reliably increase the fatigue strength at a location where stress concentration tends to occur at the fastening portion.

  ADVANTAGE OF THE INVENTION According to this invention, the fatigue strength can be raised with a simple method in the fastening structure which fastens a metal plate material to the fastening object.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is a diagram illustrating a schematic configuration of a peening jig used in the metal plate fastening method according to the present embodiment. FIG. 2A shows a perspective view of the peening jig. The figure (B) represents the bottom view of the 1st jig | tool which comprises a peening jig | tool.

  The peening jig 10 includes a first jig 11 and a second jig 12. The first jig 11 includes a jig main body 14 formed of a disk-shaped steel plate and a plurality of steel balls 16 arranged in a scattered manner on one surface of the jig main body 14. Is done. The rigidity of each jig is increased by, for example, quenching.

  A circular insertion hole 18 is provided in the center of the jig body 14 so as to penetrate in the axial direction. The jig body 14 is formed to be sufficiently larger than the head of a bolt, which will be described later, inserted through the insertion hole 18. The insertion hole 18 is formed in a size that allows insertion of the bolt shaft. A number of steel balls 16 are arranged radially and welded around the insertion hole 18 of the jig body 14. Note that the second jig 12 has substantially the same configuration as the first jig 11, and therefore the description thereof is omitted.

  Next, a method for fastening a metal plate material in the present embodiment will be described. 2 and 3 are explanatory diagrams showing a method of fastening a metal plate material. (A)-(C) of each figure represents the flow of each process of the fastening method in time series. In addition, in this Embodiment, the structure similar to what was shown in FIG. 5 as a fastening object is illustrated. FIG. 4 is a reference diagram showing the relationship between nominal compressive plastic strain and fatigue strength in a metal material.

  As shown in FIG. 2, in the present embodiment, a plate 22 and a plate 24 each made of a stainless steel plate are fastened with a bush collar 26 interposed therebetween. That is, here, the fastening object is also made of a metal member. Bolts and nuts are used as the fastening members.

  In this fastening method, as shown in FIG. 6A, the surface of each plate opposite to the bush collar 26 with the bush collar 26 interposed at a predetermined position between the plates 22 and 24. The first jig 11 and the second jig 12 are respectively disposed in Each jig is disposed so that the surface on which the steel ball 16 is disposed is opposed to the periphery of the fastening portion of each plate. At this time, the bolt insertion hole 32 formed in each plate, the bolt insertion hole 34 formed in the center of the bush collar 26, and the insertion hole 18 formed in each jig are arranged on the same axis. Then, as shown in FIG. 4B, the shaft of the bolt 28 (corresponding to the “temporary fastening member”) is inserted along the axis and screwed into the nut 30. Then, as shown in FIG. 3C, preliminary fastening with bolts 28 (also referred to as “temporary fastening”) is repeated a plurality of times. This temporary fastening is performed by an operator, but the fastening torque may be such that the surface of each plate is plastically deformed by pressing the steel balls 16 and an appropriate residual compressive stress is obtained.

  That is, by this temporary fastening, compressive stress is applied to the contact surface of each plate with the steel ball 16, and work hardening occurs in the surface layer. In addition, when the first jig 11 and the second jig 12 are rotated around the axis line in the process of repeating the temporary fastening a plurality of times, the relative positions of the steel balls 16 change and press the surface of each plate more uniformly. be able to. In this way, by pressing a plurality of steel balls 16 arranged in the peening jig 10 against each plate a plurality of times, it resembles so-called shot peening as if a large number of steel balls 16 were projected onto each plate. An effect can be obtained. Thereby, fatigue strength is increased in the work-hardened portion.

  Thereafter, the bolt 28 and the peening jig 10 are removed, and fastening with a bolt 36 (corresponding to “actual fastening member”) shown in FIG. 3A is performed instead to obtain the original fastening structure. In the present embodiment, a bolt 28 as a temporary fastening member used for temporary fastening and a bolt 36 as an actual fastening member that actually holds the fastening state are prepared separately. This is because the required length of the bolt is different between when the peening jig 10 is mounted and when the peening jig 10 is not mounted, but both the fastening members may be formed of the same bolt. For example, the thread portion of the bolt 28 may be lengthened and used as an actual fastening member. Thereby, the number of parts can be reduced.

  As a result of the fastening process as described above, as shown in FIG. 5B, the reinforcing portion 40 whose fatigue strength is increased by the residual compressive stress is formed in each plate. The reinforcing portion 40 is formed in a wider range than both the head of the bolt 36 and the nut 30. As a result, even if a load in the bending direction is applied in the fastened state and bending stress is generated in each plate, fatigue failure due to the load can be prevented or suppressed. As shown in FIG. 4, generally, there is a property that the fatigue strength is increased in a range where the strain is equal to or less than a predetermined amount between the strain due to plastic deformation of the metal material and the fatigue strength. For this reason, it is preferable to adjust the fastening torque at the time of temporary fastening to such an extent that distortion of the surface of each plate can be obtained in the range where the fatigue strength is increased in the same figure (in the example shown, the strain is less than 50%).

  As described above, in the fastening method of the metal plate material of the present embodiment, the fatigue strength of the plate to be fastened by performing the temporary fastening using the peening jig 10 prior to the final bolt fastening. Can be increased. The peening jig 10 can be realized by a simple configuration in which the steel balls 16 are disposed on one surface of the plate material, and an effect similar to so-called shot peening can be obtained by repeating the temporary fastening a plurality of times. In other words, in this fastening method, it is possible to improve the fatigue strength of the metal plate material and to suppress the fatigue failure by a simple method without using a large-scale device.

  The present invention is not limited to the above-described embodiments, and various modifications such as design changes can be added to the embodiments based on the knowledge of those skilled in the art. The described embodiments can also be included in the scope of the present invention.

  In the said embodiment, the example which comprised the peening jig | tool 10 with a pair of jig | tool consisting of the 1st jig | tool 11 and the 2nd jig | tool 12 was shown. This is in consideration that the fastening target is also made of a metal plate material. However, when the fastening target is a member having sufficient strength, the peening jig 10 is replaced with the first jig 11 and the second jig 12. However, it can also be configured. In that case, a jig is disposed on the metal plate side. In that case, bolts and nuts may be similarly used as the fastening members, but other fastening members such as screws and rivets may be used.

  In the said embodiment, although the example which welded the several steel ball 16 to one surface of the board | plate material as the peening jig | tool 10 was shown, the specific aspect is not restricted to this. For example, a plurality of protrusions may be integrally formed on one surface of the plate material by forging or casting. Or you may embed a steel ball. In that case, the shape of the protrusion may be hemispherical, or may be a conical or other protrusion shape. However, the jig in which the protrusion is integrally formed is selected from a material having a higher rigidity than the metal plate to be fastened, or is subjected to a curing process.

It is a figure showing schematic structure of the peening jig | tool used for the fastening method of the metal plate material which concerns on embodiment. It is explanatory drawing showing the fastening method of a metal plate material. It is explanatory drawing showing the fastening method of a metal plate material. It is a reference figure showing the relationship between the nominal compressive plastic strain and fatigue strength in a metal material. It is a figure which shows notionally an example of the attachment structure by a fastening member.

Explanation of symbols

  10 Peening jig, 11 First jig, 12 Second jig, 14 Jig body, 16 Steel ball, 18 Insertion hole, 22 Plate, 24 Plate, 26 Bush collar, 28 Bolt, 30 Nut, 32 Bolt insertion hole 34 bolt insertion holes, 36 bolts, 40 reinforcements.

Claims (5)

In the fastening method of fastening the metal plate material to the fastening object,
Prior to the fastening, a jig installation step in which a peening jig provided with a plurality of protrusions on one surface in a scattered manner is arranged with the plurality of protrusions facing the periphery of the fastening portion of the metal plate material; ,
A peening step of partially plastically deforming the surface around the fastening portion of the metal plate material by fastening the temporary fastening member so as to sandwich the peening jig between the metal plate material,
A jig releasing step for releasing the fastening of the temporary fastening member and removing the peening jig;
A fastening process for fastening a metal plate to a fastening object using an actual fastening member,
A method for fastening a metal plate material, comprising:   The said temporary fastening member and the said actual fastening member consist of the same fastening members, The fastening method of the metal plate material of Claim 1 characterized by the above-mentioned.   The method for fastening a metal plate according to claim 1 or 2, wherein the fastening by the temporary fastening member is repeated a plurality of times in the peening step.   The method of fastening metal sheets according to any one of claims 1 to 3, wherein the plurality of protrusions are made of a plurality of steel balls joined to one surface of the peening jig. Each fastening member consists of a bolt and a nut,
The peening jig is formed with an insertion hole for inserting the bolt at a position corresponding to the fastening portion of the metal plate material, and at least a range wider than the projection range of the head of the bolt around the insertion hole. 5. The method for fastening a metal plate according to claim 1, wherein the protrusions are arranged.

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