JP2003139180A - Bending strength member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bending strength member with high energy absorption performance. SOLUTION: This bending strength member comprises an aluminum alloy hollow shape 1 having a nearly rectangular cross section formed by flanges 4, 5 and webs 2, 3. The ratio (b/tf ) of the width (b) and the thickness (tf ) of the flange 4 which is on the compressed side when a bending load (A) acts on the hollow shape 1 exceeds 5, and the ratio (h/tw ) of the width (h) and the thickness (tw ) of the webs 2, 3 exceeds 5. The local elongation of the aluminum alloy material of the hollow shape 1 at a tension test is 2.5% or more. At bending deformation of the hollow shape 1 by the bending load (A), facing surfaces 4a, 4b of the flange 4 which is bent-deformed on the compressed side contact and interfere each other so as to prevent bending deformation of each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bending strength member made of an aluminum alloy hollow material having excellent energy absorption.

[0002]

Bending strength members are among the strength (structure) members made of aluminum alloy used in the bodies of vehicles such as automobiles, structures, buildings and the like. This bending strength member,
In the case of automobiles, bumper reinforcements, door beams,
Alternatively, a frame member or the like is exemplified.

An external load is applied to this bending strength member.
The ability to absorb the energy of (external force) by bending deformation and lateral deformation (lateral crushing) of the member itself is required.

For example, the energy of the collision load (collision energy) applied by the collision of the vehicle body is applied to the bumper reinforcement (also referred to as bumper reinforcement or bumper armature) and the door beam by its own bending deformation and cross-section deformation. Absorb by (lateral crushing),
The ability to protect the vehicle body is required.

The aluminum alloy materials used for these bending strength members are also required to be lighter in weight and lower in assembly cost, and are basically hollow sections having a rectangular cross section.
And, this hollow shape material is mainly 5000 series, 6000 series,
It is manufactured by extruding and tempering (heat treatment) a high-strength aluminum alloy such as 7000 series. Further, the aluminum alloy plate may be formed by rolling and then welded to form a hollow shape member.

A conventional bending strength member made of an aluminum alloy hollow profile will be described with reference to FIG. FIG. 9 (a) shows a perspective view of a conventional bending strength member (hollow shape member) having a hollow cross-sectional shape of 1 m. Bending strength member 1m is in bending load direction
With (horizontal direction), flanges (vertical walls) 4 and 5 which are arranged vertically and parallel to each other, and horizontal webs (horizontal walls) 2 and 3 which connect them and are parallel to each other, are used to extend in the longitudinal direction of the profile. It has a substantially rectangular cross section with a uniform mouth shape. The type of this rectangular cross section is, in addition to this mouth-shaped hollow cross section,
A cross-sectional shape such as a shape in which both ends of the flange are juxtaposed to the left or right of the web width, a cross-sectional shape such as a day shape, a square shape, or an eye shape in which a middle rib is provided for reinforcement is appropriately selected according to the application.

According to such a bending strength member made of an aluminum alloy hollow shape member (hereinafter, also simply referred to as bending strength member), it is possible to reduce the weight and to prevent collision, compared to the conventionally used bending strength members made of steel material. Higher energy absorption under load can be expected.

As shown in FIG. 9 (b), when a bending load is applied in the direction of arrow A (horizontal direction) substantially perpendicular to the longitudinal direction of the bending strength member 1m, the bending on the side where the bending load acts A bending deformation occurs in which a horizontal compressive force F1 is applied to the inner flange 4 and a horizontal tensile force F2 is applied to the opposite bent outer flange 5. Therefore, the bending inner flange 4 is a compression side (compression stress side) flange, and the bending outer flange 5 is a tension side (tensile stress side) flange.

Here, as shown in the plan view of FIG. 9 (b) in the state of FIG. 9 (b), when the bending load is applied, the bending load is supported by the bending load of the bending strength member 1m at the beginning. The bending deformation takes place at the bent portion (center portion 12) as the bending center (bending portion). Normally, this bending deformation absorbs the energy of the bending load.

On the other hand, as shown in FIG. 10 (b), in the central portion 12 of the bending strength member 1m under a bending load, the compression side flange 4 and the webs 2 and 3 are not locally buckled. If deformation occurs further, the compression side flange 4 or web
While the deformation of 2 and 3 is remarkably curved, the crush deformation of the cross section formed by these (indicated by the range X) proceeds. If this crush deformation progresses, the compression side flange 4
Since the and webs 2 and 3 are curved, they cannot bear the load sufficiently. Further, since the depth of the cross section is reduced, the resistance moment against bending deformation is reduced and the bending resistance is reduced.
As a result, the energy absorption amount of the bending strength member 1m is further reduced.

Therefore, in order to increase the energy absorption amount of the bending strength member, the original energy due to the original deformation of the rectangular cross-section structure in which the collapse deformation of the cross section is prevented and the entire cross section efficiently bears the stress. It is important to allow absorption.

Conventionally, various means have been proposed in order to enhance the energy absorption performance of the bending strength member. That is, increasing the strength of the material aluminum alloy, limiting the ratio b / t _f of the compression side flange width b to the thickness t _f to a certain value or less, the ratio of the web width h to the thickness t _w h / t _w To a certain value or less, JP-A-6101732, JP-A-11-173356, and republished patents
Proposed in WO99 / 10168 and other publications, a CFRP material or FRP material reinforced with carbon fiber or the like is provided on the tensile side flange surface of an aluminum alloy hollow shape material, and so on.

[0013]

To increase the strength of the material aluminum alloy, the amount of bending deformation and the amount of deformation of the cross section of the bending strength member until the deformation of the cross section of the bending strength member (bringing of the cross section) occurs due to the bending load. Is effective in improving the energy absorption performance in a relatively small range. However, after the crush deformation of the cross section of the bending strength member occurs, the load is extremely reduced, and it is not effective for improving the energy absorption performance up to a large bending deformation.

The width b and the thickness of the compression side flange
and limiting the ratio b / t _f and t _f below a predetermined value, to a ratio h / t _w of the width h and the thickness t _w of the web to the predetermined value or less, the energy to the large bending deformation In order to improve the absorption performance, it is necessary to considerably thicken the wall. For this reason, the weight increases, and the weight saving itself, which is a great advantage of using the aluminum alloy material for the bending strength member, is impaired.

Further, in the above-mentioned CFRP material and the technology for providing the FRP material, the technique is provided on the tensile side flange surface of the bending strength member.
Since the FRP material bears the bending load applied, it suppresses the excessive deformation of the compression side flange and causes the original energy absorption due to the deformation of the rectangular cross-section structure of the hollow shape member. However, the cost of adding new CFRP material or FRP material and the increase in the number of processes are disadvantageous.

Therefore, an object of the present invention is to solve these problems of the prior art and to provide a bending strength member having an increased energy absorption amount.

[0017]

In order to achieve this object, the gist of the bending strength member of claim 1 of the present invention is that the bending strength member is made of an aluminum alloy hollow shape member having a substantially rectangular cross section formed by a flange and a web. The ratio b / t _f of the width b and the thickness t _f of the flange on the compression side when a bending load is applied to the hollow shape member exceeds 5 and the width h and the thickness t of the web are the ratio h / t _w and _w exceeds 5, and the local elongation in tensile test of the aluminum alloy material of the hollow profile is 2.5% or more, when the bending deformation of the hollow shape member by the action of the bending load, the bending deformation The facing surfaces of the compression side flanges are in contact with each other, and interfere with each other so as to prevent mutual bending deformation.

In the case of an aluminum alloy hollow shape member, when the hollow shape member is bent and deformed by the action of the bending load, as shown in FIG.
When local buckling of the compression-side flange described in (b) occurs, the faces (bending symmetry planes) facing each other of the bending-deformed compression-side flange contact each other, as shown in Fig. 1 (b) described later. It becomes a state.

In this state, under certain conditions, the opposing surfaces of the bending-deformed compression-side flanges interfere with each other so as to prevent the bending deformation. When this phenomenon occurs,
The crush deformation of the cross section formed by the compression side flange or the web does not proceed any further, and apparently the entire cross section undergoes bending deformation with the depth of the cross section increasing, and the resistance moment against bending deformation increases. In the present invention, by utilizing the interference effect of the opposing surfaces of the bending-deformed compression-side flange, the energy absorption amount of the bending strength member is significantly increased, and a certain condition capable of effectively expressing this interference effect is provided. It has been specified.

This constant condition is, for example, the width b and the thickness t of the compression side flange of the bending strength member shown in FIG. 9 (a).
_f and the ratio b / t _f and the web width h and the ratio between the thickness t _w h /
It is the condition of t _w and the local elongation δ ^' (%) in the tensile test of the hollow shape material (aluminum alloy material).

Further, in order to further strengthen the interference between the facing surfaces of the compression-side flange that has been bent and deformed, in addition, as described in claim 2, a projection is provided on the surface of the compression-side flange. It is preferable that the protrusions are configured so that the protrusions on the facing surfaces of the compression-deformed flange that have been bent and deformed contact each other when the hollow shape member is bent and deformed by the action of the bending load.

As described above, according to the present invention, the energy absorption amount of the bending strength member can be greatly increased. Therefore, as in the gist of claim 3, a frame reinforcing material for automobiles having high required characteristics of this kind. It is suitable for use in.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the bending strength member of the present invention will be described in detail below with reference to the drawings. FIG. 1 (a) is a perspective view of a bending strength member 1a made of an aluminum alloy hollow shape member according to the present invention, in which bending strength member (hollow shape member) 1a is bent in a direction substantially perpendicular to the longitudinal direction from an arrow A direction. The figure shows a state in which a load is applied and bending is deformed in a V shape in the longitudinal direction.

The cross-sectional shape of the bending strength member 1a is basically the same mouth shape as the cross-sectional shape of the conventional bending strength member 1m shown in FIG. 9, and is perpendicular to the bending load direction (horizontal direction).
The flanges (vertical walls) 4 and 5 arranged in parallel to each other and the horizontal webs (horizontal walls) 2 and 3 that connect them and connect them to each other make it possible to form a uniform mouth shape in the longitudinal direction of the profile. It has a rectangular cross section. In addition, 2a is a web portion deformed in a convex shape.

When a large bending load is applied to the bending strength member 1a in the direction of the arrow A in the member central portion (member bending center) 11, the bending strength member 1a of FIG. As shown in Fig. 1 (b), through the bending deformation state of the V shape centering on the member bending center 11 of the side flange 4, and as shown in Fig. Bending deformation progresses until they come close to or contact with 4b.

Here, the ratio b / t _f between the width b and the thickness t _f of the compression side flange 4 exceeds 5, and the ratio h / t _w between the width h and the thickness t _w of the webs 2 and 3 is increased. 5 traversal, and, when the local elongation [delta] ^'in the aluminum alloy material tensile test of the hollow shape member with more than 2.5%, the center bending bending deformation and compression-side flange 4 of the opposed surfaces 4a and 4b between 11
Faces 4a and 4b that are in contact with each other with the center of
When they are bent, they interfere with each other so as to prevent further bending. As a result, the interference portion of the compression side flange bears the compressive load, so that the crush deformation of the cross section formed by the compression side flange 4 and the webs 2 and 3 does not proceed any more, and the depth of the cross section is apparent. In the state in which is increased, the entire cross section undergoes bending deformation, and the resistance moment against bending deformation increases.

FIG. 2 schematically shows the action and effect of the bending strength member of the present invention with a load-displacement curve. In Fig. 2, in the initial stage of bending deformation of the bending strength member 1m as shown in Fig. 10 (a), the member elastically deforms, and the load-displacement relationship is linear as in the area A in Fig. 2. Become.

When the bending deformation further progresses and the bending strength member 1m shown in FIG. 10 (b) is obtained, the compression side flange 4 and the web 2 are formed at the central portion of the bending strength member 1a under the bending load. , 3, while the curved buckling occurs, the crush deformation of the cross-section progresses, and the solid line 2 in the areas B and C in Fig. 2
The load decreases as shown in. As a result, the energy absorption amount of the conventional bending strength member is significantly reduced.

On the other hand, when all three conditions of the above-mentioned two bending strength member cross-sectional shape conditions and aluminum alloy material conditions are satisfied, as described above, the bending-deformed compression side flanges face each other, and , Interfering with each other's bending deformation so as to prevent further bending deformation, the resistance moment against bending deformation increases. As a result, the solid line 1 in the areas B and C in Fig. 2
The load increases like. As a result, the energy absorption amount of the bending strength member of the present invention is significantly increased.

Of course, there are various differences in the conditions of the bending strength member itself and the conditions of use of the bending strength member. The strength of the bending strength member itself, the difference in the cross-sectional shape conditions, and the difference in the usage conditions of the bending strength member such as the level of bending load required for the automobile, etc. Within the range of difference, in order to make the opposing faces of the bending side compression deformed flanges interfere with each other to the extent that energy absorption is improved, in order to interfere with each other's bending deformation, It is necessary to satisfy all three conditions: strength member cross-sectional shape condition and aluminum alloy material condition.

On the other hand, the ratio b / t _f between the width b and the thickness t _f of the compression side flange is 5 or less, or the ratio h / t _w between the width h and the thickness t _w of the web is 5 or less. If
Faces of the compression-deformed flange that have been bent and deformed do not come into contact with each other, so that they do not interfere with each other. In addition, since the compression side flange thickness t _f and the web thickness t _w are increased, no significant buckling occurs in the bending strength member,
Shows high energy absorption. However, the increase in the thickness of the bending-strength member due to the increase in the thickness is large, which is not practical.

Further, bending deformability as raw material in the case of local elongation [delta] ^'is less than 2.5% in the aluminum alloy material tensile test of the hollow shape member is reduced. Therefore, the above b /
Even _if the two conditions of t _f and h / t _w are satisfied, the curved side of the compression side flange and the above-mentioned curved deformation part of the web may be bent before or after the faces of the compression side flange that have been bent and deformed contact each other. Breakage easily occurs.

As a result, depending on the condition of the bending strength member or regardless of the condition of the bending strength member, the facing surfaces of the compression-deformed flanges that have been bent and deformed may interfere with each other against the bending deformation. However, only the crush deformation of the cross section progresses, and the load decreases as shown by the solid line 2 in the regions B and C in FIG.

Next, as described in claim 2, a mode in which a projection is provided on the surface of the compression side flange will be described.
When a protrusion is provided on the surface of the compression-side flange, when the hollow shape member is bent and deformed by the action of the bending load, contact between the protrusions occurs from an early stage of bending and deformation, so Interference with each other's bending deformation occurs quickly. Therefore, in the area B in Fig. 2, the resistance moment against bending deformation increases, and the load increases. As a result, the energy absorption amount of the bending strength member is significantly increased.

FIG. 3 (a) is a perspective view of an aluminum alloy hollow profile bending strength member 1b according to the present invention provided with this protrusion, and FIGS. 3 (b) and 3 (c) are bending strength members (hollow type). It shows a state in which a bending load is applied from the direction of arrow A, which is substantially perpendicular to the longitudinal direction of the material 1b, and the material is bent and deformed in a V shape in the longitudinal direction. The cross-sectional shape of the bending strength member 1b is basically the same mouth shape as the cross-sectional shape of the bending strength member 1a of FIG. 1a.

When the projections 6 and 7 are provided on the compression-side flange 4, the surfaces 4a and 4b of the normal compression-side flange 4 which face each other are opposed to each other.
Before contacting each other, the protrusions 6 and 7 are pushed in front of each other (repulsing each other), further advancing or contacting between the facing surfaces 4a and 4b, that is, more dogleg bending deformation. Hinder the progression of. In other words, compression side flange 4
When the projections 6 and 7 are provided on the surfaces of the compression-side flanges, which are bent and deformed, the opposing surfaces of the compression side flanges interfere with each other from an early stage of the bending deformation.

As a result, as compared with the case where there is no protrusion, the resistance moment against bending deformation increases due to the interference of the opposing surfaces 4a and 4b against the bending deformation from each other at an early stage, and B and C in FIG. The load increases as shown by the dotted line 3 in the area. Therefore, the energy absorption amount of the bending strength member of the present invention is significantly increased.

The cross-sectional shape of the protrusion is, in short, to suppress the local buckling of the compression-side flange 4 and to make contact before the usual contact between the facing surfaces 4a and 4b of the compression-side flange 4. The shape is appropriately selected, including the size, from the relationship between the required energy absorption amount of the bending strength member and the weight increase allowable amount by providing the protrusion. Further, the shape of protrusions in the longitudinal direction may be uniform or may not be uniform.

Other embodiments of this protrusion shape are shown in FIGS. First, FIGS. 4 (a) to 4 (e) show an example in which arc-shaped (semi-circular) projections are provided on the compression side flange 4. In the bending strength member 1c shown in the perspective view of FIG. 4 (a), one of the arc-shaped (semi-circular) projections 8 larger than the projections 6 and 7 of FIG. 3 is used as the center portion in the width direction of the compression side flange 4. It was installed in.

In addition, in the bending strength member 1d shown in FIG. 4 (b) showing only the cross section, a protrusion is formed in the same manner as the protrusions 6 and 7 in FIG. The example provided is shown. In the bending strength member 1e of FIG. 4 (c) showing only the cross section,
An example in which protrusions are provided in the same cross section as in FIG. 4 (b) as in FIG. 4 (a) is shown. The bending strength member 1f of FIG. 4 (d) showing only the cross section shows an example in which two protrusions are provided, one on each web side. In the bending strength member 1g of FIG. 4 (e) showing only the cross section,
An example is shown in which both ends of the compression-side and tension-side flanges are shaped so as to project outward from the web width, and two protrusions are provided on the compression-side flange-side middle rib joint portion.

In the bending strength member shown in FIG. 5, the compression-side flange 4 itself having a mouth-shaped cross section is projected outward in an appropriate shape to form a projection on the compression-side flange surface. Among them, the bending strength member 1h shown in FIG. 5 (a) is provided with one square-shaped protruding portion 9 in which the surface center of the compression-side flange 4 protrudes outward. In addition, in the bending strength member 1i shown in FIG. 5 (b) showing only the cross section, two points, that is, the upper side and the lower side of the compression side flange surface of the mouth-shaped cross section, are projected outward in a square shape. Also, FIG.
In the bending strength member 1j of (c), the same overhanging portion 9 as in FIG. 5 (b) is used.
The following shows an example in which is provided in a day cross section. Further, in the bending strength member 1k shown in FIG. 5 (d), the same square-shaped overhanging portion as the above-mentioned FIG.
It is provided with an individual.

Further, in the bending strength member of FIG. 6, the compression-side flange itself having a day-shaped cross section is formed as projections 10a and 10b on the compression-side flange surface as arc-shaped walls that project outward at two locations. Therefore, the hollow profile has a substantially B-shaped cross section.

It is not always necessary to provide these protrusions or bulges over the entire length of the compression side flange, and it is also possible to partially provide only the portions corresponding to the surfaces 4a and 4b facing each other with the bending center 11 of the member as the center. It is possible. Further, as the cross-sectional shape of the overhang, an appropriate shape such as a smooth or stepped arcuate shape or a square shape is selected.

The aluminum alloy hollow profile used for the bending strength member of the present invention has a hollow shape in which the cross-sectional shape in the longitudinal direction is not necessarily the same, but the hollow shape in which the cross-sectional shape changes partially or sequentially is on the design side of the member. You can choose freely. In addition, the cross-sectional shape is also mouth-shaped, sun-shaped, eye-shaped, or T-shaped, or a shape in which both ends of the flange as shown in Fig. 4 (e) above are projected to the left and right outside the web width. The cross-sectional shape that is deformed or added to the rectangular cross-section is appropriately selected according to the application, such as an arc shape in which the web bulges outward or inward, or a shape in which the flange and the web are inclined instead of parallel. To be done.

Therefore, the rectangular cross section referred to in the present invention does not mean a rectangular shape in a strict sense, but means a substantially or substantially rectangular cross section. Therefore, the stipulations of flanges such as being arranged perpendicular to the bending load direction and parallel to each other, and web regulations such as horizontal webs parallel to each other do not require strictness in the regulation of vertical, parallel or horizontal. It means abbreviation (generally).

In addition, the aluminum alloy profile used for the bending strength member of the present invention is a hollow profile having a substantially rectangular cross section because of other requirements such as weight reduction and assembly cost reduction.
The hollow profile is preferably composed of extruded profiles. The production itself of this extruded shape is made by casting, homogenizing heat treatment,
It is appropriately produced by a conventional method having hot extrusion, heat treatment for tempering and the like as main steps. By using the extruded shape member, it becomes possible to easily and efficiently manufacture even if the design has a complicated cross-section. It should be noted that the aluminum alloy plate may be formed into a hollow shape by welding, bonding or the like after forming the aluminum alloy plate by rolling.

As the aluminum alloy used in the hollow shape member of the present invention, an aluminum alloy that does not meet the standards of AA to JIS or that satisfies the required characteristics can be appropriately used. Among these, 6000 series and 7000 series aluminum alloys, which are commonly used for structural materials such as transportation machines, are preferable.

(Example) A linear aluminum alloy extruded shape having a mouth-shaped cross-sectional shape shown in FIG. 1 (length 1300 mm)
The energy absorption was determined by changing the mechanical properties of the aluminum alloy and the cross-sectional conditions of the profile. In the test, the bending deformation of the bending strength member was simulated, and the three-point bending test with load P shown in Fig. 11 was performed, and the energy absorption amount was obtained from the relationship between the load and the displacement of the extruded profile. The energy absorption amount is represented by the energy absorption amount E (N.mm) up to 270 mm of bending deformation amount (indentation deformation amount) in FIG. 11 and the energy absorption amount obtained by making this E dimensionless, and each is shown in Table 1. It should be noted that the dimension E is made dimensionless by the cross-sectional area A (mm ² ) of the profile, the tensile strength σb (MPa) of the aluminum alloy, and the distance between the three-point bending test support points
It was calculated by E / (A σbL) divided by the product of (span L, mm).

The mechanical properties of the aluminum alloy are hollow
Changing the condition of heat treatment (heat treatment) after extrusion of the material
In addition, in the tensile test of hollow shape material (aluminum alloy material)
Local elongation δ^'(%) Was changed. Also, the cross section of the profile
The condition is that the width b of the compression side flange shown in FIG. 9 (a) and
Thickness t_fRatio with b / t_fAnd the width h and thickness t of the web _w
Ratio with h / t_wThe compression side fla
Thickness t_fAnd web thickness t_wChange by changing
Let These conditions are also shown in Table 1.

In addition, in Table 1, the invention example 4 in which the number is marked with * is the projections 6 and 7 having the arcuate cross section shown in FIG. 3 (a).
(Height 3 mm, width 5 mm) has a cross-sectional shape provided on the compression flange side (however, the cross-sectional area A of the profile does not include the cross-sectional area of the protrusion), and the other conditions are the same as in Invention Example 1.

Inventive Examples 1 to 4 are, as is clear from Table 1,
Ratio b / t of width b and thickness t _f of compression side flange 4 of the hollow profile
_{When f} exceeds 5, the ratio h / t _w between the width h and the thickness t _w of the webs 2 and 3 exceeds 5, and the local elongation δ ^'
Is 2.5% or more.

As a result, for example, the dimensionless energy absorption amount [E / (Aσb
L)] is set to 0.0100, the invention examples 1 to 4 show that the energy absorption amount E (N · mm) and the energy absorption amount [E / (AσbL)] obtained by making this E dimensionless are the local elongation δ. ^' Is less than 2.5%, which is higher than Comparative Examples 5 to 7, which satisfies the dimensionless energy absorption criterion of 0.0100. This tendency is stronger as the local elongation δ ^' is higher. Further, in particular, Invention Example 4 in which the protrusion is provided on the compression flange side is Invention Example 1 under the same conditions other than the above.
Energy absorption is higher than.

Further, according to the visual observation at the time of the three-point bending test, in Invention Examples 1 to 4, when the hollow shape member is bent and deformed by the action of the bending load, (b) of FIG. 1 and (c) of FIG. ), The opposite faces of the compression-side flange that have been bent and deformed
It was confirmed that (the protrusions facing each other in Inventive Example 4) were in contact with each other and interfered with each other so as to prevent mutual bending deformation. In Invention Examples 1, 2, and 4, cracks (breakages) did not occur in the compression side flange and the curved deformation portion of the web. However, only in Invention Example 3 in which the local elongation δ ^' is low,
Since the bending deformability was relatively small, minute cracks were formed in the compression side flange and the curved deformed portion of the web.

[0054] In contrast, Comparative Example 5 local elongation of the hollow shape member [delta] ^'is less than 2.5% of the lower limit, the invention example low energy absorption amount compared to 1, the energy absorption amount of criteria dimensionless 0.0100 is not satisfied either. In Comparative Example 6, 7 local elongation of the hollow shape member [delta] ^'is less than 2.5% of the lower limit, the invention Example
The energy absorption is lower than that of 2, and the dimensionless energy absorption criterion 0.0100 is not satisfied. Furthermore, these Comparative Examples 5, 6, and 7 have a low local elongation δ ^′ ,
Since the bending deformability was reduced, large cracks were formed in the compression side flange and the curved deformed portion of the web.

Actually, according to the visual observation of the comparative examples 5 to 7 in the above-mentioned three-point bending test, which is similar to the invention examples, the bending deformation of the hollow shape member due to the action of the bending load causes the bending deformation. Before the facing surfaces of the side flanges contact each other,
As shown in Fig. 10 (b), there is a local buckling 12 on the compression side flange 4 and the webs 2 and 3 under bending load, and
It was confirmed that the crushing deformation of the cross section formed by these proceeded.

On the other hand, the width b and the thickness t of the compression side flange are
The ratio b / t _f with _f is 5 or less, or the ratio h / t _w is Comparative Example 8-12 5 or less of the width h and the thickness t _w of the web,
Faces of the compression-deformed flange that have been bent and deformed do not come into contact with each other, so that they do not interfere with each other. In Comparative Examples 8 to 12, as shown in Table 1, since the compression side flange thickness t _f and the web thickness t _w inevitably become large,
No significant buckling occurs in the flexural strength member, and a high energy absorption amount is exhibited as compared with the invention examples. However, in these Comparative Examples 8 to 12, the weight increase of the bending strength member due to the increase in the thickness is large, which is not practical.

Loads of Invention Examples 1 to 4 and Comparative Examples 5 to 7-
Figure 7 shows the displacement curve. In FIG. 7, invention examples 1 to 4
(Black circles, white circles, black squares, black diamonds) are compared with Comparative Examples 5 to 7 (black triangles, white triangles, white squares) as shown by dotted lines 2 and 3 in the areas B and C in FIG. 2. The increase in load or the decrease in load is small, which supports the increase in energy absorption. However, in the invention example 3 in which the local elongation δ ^′ is around 2.6% and the lower limit value is around 2.5%, the load decrease in the regions B and C in FIG. 2 is small as compared with Comparative examples 5 to 7, There is no increase in load as in Invention Examples 1 and 2.

In addition, in the invention examples 1 to 3 and the comparative examples 5 to 7, the local elongation δ ^' (horizontal axis) and the dimensionless energy absorption [E
Figure 8 shows the relationship with / (AσbL)] (vertical axis). From Figure 8,
It can be seen that there is a boundary point in the vicinity of 2.5 of the local elongation δ ^' , whether or not the dimensionless energy absorption criterion 0.0100 is satisfied.

From the above results, the ratio b / t _{f of} the compression side flange width b to the thickness t _f, and the ratio of the web width h to the thickness t _w.
h / t _w and the critical significance of local elongation in tensile test of the aluminum alloy material of the hollow shape members, and the effect of improving the energy absorption amount of the present invention the bending strength member is clear.

[0060]

[Table 1]

[0061]

According to the present invention, it is possible to provide a bending strength member that sufficiently satisfies the required energy absorption amount without impairing the advantages of the aluminum alloy material. Therefore, the use of the aluminum alloy material for vehicle body structural materials such as transport aircraft is greatly expanded, and the industrial value is great.

[Brief description of drawings]

FIG. 1 shows the bending deformation state of the bending strength member of the present invention from (a).
It is a perspective view shown to (b).

FIG. 2 is an explanatory view showing a load-displacement state of the bending strength member of FIG.

FIG. 3A is a perspective view showing another embodiment of the bending strength member of the present invention, and FIGS. 3B and 3C are perspective views showing the bending deformation state thereof.

4A and 4B respectively show another embodiment of the bending strength member of the present invention, FIG. 4A is a perspective view, and FIGS. 4B to 4E are sectional views.

5A and 5B respectively show another embodiment of the bending strength member of the present invention, FIG. 5A is a perspective view, and FIGS. 5B to 5D are sectional views.

FIG. 6 is a perspective view showing another embodiment of the bending strength member of the present invention.

FIG. 7 is an explanatory diagram showing a load-displacement curve in the example.

FIG. 8 is an explanatory diagram showing the relationship between the local elongation and the energy absorption amount in the example.

FIG. 9A is a perspective view showing a conventional bending strength member, and FIG.
FIG. 4 is a perspective view showing a bending deformation state thereof.

10 (a) and 10 (b) are plan views showing the bending deformation state of FIG.

FIG. 11 is a plan view showing a three-point bending test in an example.

[Explanation of symbols]

1: Bending strength member (hollow shape), 2, 3: Web, 4: Compression side flange, 5: Tensile side flange, 6, 7, 8, 9, 10: Protrusion, 11: Bending center,

Claims (3)

[Claims] 1. A bending strength member made of an aluminum alloy hollow frame having a substantially rectangular cross section formed by a flange and a web, wherein the width b of the flange is a compression side when a bending load is applied to the hollow frame. And the thickness t _f ratio b / t _f is
5 with excess of a ratio h / t _w of the width h and the thickness t _w of the web exceed 5, and the local elongation in tensile test of the aluminum alloy material of the hollow profile is 2.5% or more, the bending load The bending strength member characterized in that, when the hollow shape member is bent and deformed by the action of, the facing surfaces of the bent and deformed compression side flanges come into contact with each other and interfere with each other so as to prevent mutual bending deformation. . 2. A protrusion is provided on a surface of the compression side flange,
The bending strength member according to claim 1, wherein when the hollow shape member is bent and deformed, the protrusions are configured so that the protrusions on the surfaces of the compression-side flange that have been bent and deformed contact each other. 3. The bending strength member according to claim 1, wherein the bending strength member is an automobile frame reinforcing material.