U.S. patent application number 09/770092 was filed with the patent office on 2001-11-08 for alminum alloy energy-absorbing member.
Invention is credited to Bekki, Yoichiro, Ueno, Seizo.
Application Number | 20010037844 09/770092 |
Document ID | / |
Family ID | 18542370 |
Filed Date | 2001-11-08 |
United States Patent
Application |
20010037844 |
Kind Code |
A1 |
Bekki, Yoichiro ; et
al. |
November 8, 2001 |
Alminum alloy energy-absorbing member
Abstract
An aluminum alloy energy-absorbing member, which satisfies the
conditions of .alpha..gtoreq.24 and
(.alpha..times..sigma.).gtoreq.6000, wherein .alpha. (%) is the
rupture elongation at a gauge distance of 5 mm, and .sigma. (MPa)
is a 0.2% proof stress value, in the extruding direction of an
aluminum alloy extruded material. This is an aluminum alloy
energy-absorbing member that is lightweight, high in energy
absorption, adequate in required mechanical strength, and
preferable as an impact-absorbing member for an automobile, and the
like.
Inventors: |
Bekki, Yoichiro; (Tokyo,
JP) ; Ueno, Seizo; (Tokyo, JP) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
620 NEWPORT CENTER DRIVE
SIXTEENTH FLOOR
NEWPORT BEACH
CA
92660
US
|
Family ID: |
18542370 |
Appl. No.: |
09/770092 |
Filed: |
January 24, 2001 |
Current U.S.
Class: |
148/440 |
Current CPC
Class: |
C22C 21/10 20130101;
C22C 21/08 20130101 |
Class at
Publication: |
148/440 |
International
Class: |
C22C 021/06 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 24, 2000 |
JP |
2000-15005 |
Claims
What is claimed is:
1. An aluminum alloy energy-absorbing member, satisfying the
conditions of .alpha..gtoreq.24 and
(.alpha..times..sigma.).gtoreq.6000, wherein .alpha. (%) is the
rupture elongation at a gauge distance of 5 mm, and .sigma. (MPa)
is a 0.2% proof stress value, in the extruding direction of an
aluminum alloy extruded material.
2. The aluminum alloy energy-absorbing member as claimed in claim
1, wherein the aluminum alloy is an Al--Mg--Si alloy or an
Al--Zn--Mg alloy.
3. The aluminum alloy energy-absorbing member as claimed in claim
1, which is used as a frame material for a side member, or a bumper
beam material.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an energy-absorbing member
composed of an aluminum alloy extruded material. More particularly,
the invention relates to an energy-absorbing member preferably used
as a frame material for a car body side member, for reducing the
impact effect on passengers in the event of a collision of a
transport vehicle, especially an automobile.
BACKGROUND OF THE INVENTION
[0002] In transport vehicles such as automobiles, recently,
protection of passengers from collision impact is becoming more and
more important, and in automobiles, in particular, it will become
obligatory to equip them with structure and devices for protecting
passengers in the event of a crash. Specifically, in the front
engine section and rear trunk section of an automobile, structure
and means are being devised for absorbing crash energy by
accordion-like plastic deformation of structural members, such as
side members, at the time of a collision. As the structural members
for absorbing such crash energy, hitherto, cold-rolled steel sheets
have been used, and they are assembled by press forming or spread
welding.
[0003] Lately, however, from the viewpoint of environmental
problems and automotive performance improvement, lightweight
vehicles are demanded, and aluminum materials, which are lighter
than steel sheets, are being studied to apply. As the aluminum
material conforming to this purpose, an extruded material is being
highly expected, because a structural member of complicated shape
can be easily manufactured, and vehicle weight can be more reduced
than sheet materials.
[0004] Necessary material characteristics in such an
energy-absorbing member include (1) fitness for hollow extrusion,
(2) adequate mechanical strength as a structural member, (3) large
energy absorption upon a collision, and (4) fitness for
welding.
[0005] As an energy-absorbing member made of aluminum alloy,
materials having rupture elongation and local (locally-caused)
elongation defined in a specified range, are proposed in
JP-A-7-118782 ("JP-A" means unexamined published Japanese patent
application), but the energy absorption, which is the most
important characteristic for an energy-absorbing member, was not
sufficient.
[0006] Among conventional aluminum alloy extruded materials,
Al--Mg--Si alloy and Al--Zn--Mg alloy are known to be relatively
excellent in mechanical strength and elongation, but there is the
problem that their energy absorption is insufficient by only
conventional extrusion.
SUMMARY OF THE INVENTION
[0007] The present invention is an aluminum alloy energy-absorbing
member, which satisfies the conditions of .alpha..gtoreq.24 and
(.alpha..times..sigma.).gtoreq.6000, wherein .alpha. (%) is the
rupture elongation at a gauge distance of 5 mm, and .sigma. (MPa)
is a 0.2% proof stress value, in the extruding direction of an
aluminum alloy extruded material.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is an explanatory view showing a method of the
compression test in the examples.
[0009] FIG. 2 is an example diagram of measurement of a
displacement load curve of the compression test in the
examples.
DETAILED DESCRIPTION OF THE INVENTION
[0010] The present inventors intensively investigated the
energy-absorbing properties and material characteristics of
aluminum alloy extruded material, and discovered that the energy
absorption cannot be evaluated correctly by the combination of
rupture elongation and local elongation of conventional tensile
test specimens of JIS No. 13B and JIS No. 5, and that the energy
absorption depends on a correlative relation between the rupture
elongation at a gauge distance of 5 mm and a 0.2% proof stress
value. The present invention has been accomplished based on these
findings.
[0011] That is, according to the present invention there is
provided: an aluminum alloy energy-absorbing member, satisfying the
conditions of .alpha..gtoreq.24 and
(.alpha..times..sigma.).gtoreq.6000, wherein .alpha. (%) is the
rupture elongation at a gauge distance of 5 mm, and .sigma. (MPa)
is a 0.2% proof stress value, in the extruding direction of an
aluminum alloy extruded material.
[0012] The values of .alpha. and .sigma. in the present invention
are values obtained by tensile testing at a tensile speed of 5
mm/min, using JIS No. 13B test specimens. The rupture elongation
.alpha. at a gauge distance of 5 mm in the extruding direction is
the value (%) expressing the rate of elongation to the initial
length of 5 mm, by performing the tensile test by drawing lines at
intervals of 5 mm in the vertical direction to the extruding
direction in the parallel section of the specimen, and measuring
the interval of the lines when the specimen is ruptured.
[0013] The energy-absorbing member of the present invention is made
of an aluminum alloy extruded material. As long as the values of
.alpha. and .sigma. are as described later, the composition of the
aluminum alloy is not restricted, but an Al--Mg--Si alloy or an
Al--Zn--Mg alloy can be preferably used, because the mechanical
strength and elongation are relatively high.
[0014] The aluminum alloy extruded material used in the
energy-absorbing member of the present invention has the following
values as the rupture elongation .alpha. (%) of a gauge length of 5
mm and a 0.2% proof stress value .sigma. (MPa), in the extruding
direction.
[0015] The value of .alpha. of the aluminum alloy extruded material
used in the present invention is 24% or more, preferably 30% or
more. If the value of .alpha. is too small, the member is not
deformed uniformly, accordion-like, when receiving an impact, and
the intended energy absorption property is not obtained. The upper
limit of .alpha. is generally 60% or less.
[0016] The product of .alpha. and .sigma. (.alpha..times..sigma.)
of the aluminum alloy extruded material is 6000 or more, preferably
6500 or more. If the value of (.alpha..times..sigma.) is too small,
the energy absorption in plastic deformation of material is small,
and it cannot be used as an energy-absorbing member. The upper
limit of (.alpha..times..sigma.) is generally 100000 or less.
[0017] The energy absorption property of the energy-absorbing
member of the present invention is an energy-absorbing amount in
compression testing of generally 10 kg.multidot.m or more,
preferably 12 kg.multidot.m or more.
[0018] If necessary, by adjusting the composition of the aluminum
alloy, or adjusting the heat treatment condition, the aluminum
alloy extruded material having such values of .alpha. and .sigma.
can be obtained. The method of adjustment varies with the
composition of the alloy to be used, and if the value of .alpha. is
too small, for example, it is adjusted by heat treatment. If the
value of (.alpha..times..sigma.) is too small, it may be adjusted
by adding an element for increasing the mechanical strength, or by
changing the aging condition.
[0019] By using the aluminum alloy extruded material adjusted to
such values of .alpha. and .sigma., an energy-absorbing material
that prevents a decrease of the energy-absorbing amount while
maintaining the necessary characteristics such as mechanical
strength, can be obtained.
[0020] The shape and size of the energy-absorbing member of the
present invention are not particularly restricted, and it may be
properly used as a member necessary for absorbing energy, for
example, at a crash. Specifically, in an automobile, for example,
it is preferably used as a member for lessening the impact effect
on passengers in the event of a collision. It may be used as a
frame material for a side member, and a bumper beam material, and
the like.
[0021] The energy-absorbing member of the present invention is made
of a lightweight aluminum alloy, and it has high energy absorption
while satisfying the necessary mechanical strength and the like as
a structural member. Therefore, the present invention is very
useful as an impact-absorbing member for an automobile and the
like.
[0022] The present invention is described in more detail based on
the following examples and comparative examples, but the invention
is not limited to those.
EXAMPLES
Examples 1 to 9, Comparative Examples 1 to 4
[0023] Each of alloys having the composition shown in Table 1 was
melted and casted into a billet of 220 mm in diameter, then the
billet was homogenized for 2 to 8 hours at 470 to 580.degree. C.,
and extruded into a square form with a cross inside, with one side
of 100 mm and a wall thickness of 2.5 mm. Further, as shown in
Table 2, the thus-obtained extruded material was fan-cooled right
after extrusion, and aged, to obtain a T5 tempered material (which
is referred to as "air-cooled" in Table 2), or the material was
held at a temperature of 470 to 520.degree. C. for 40 minutes,
cooled in water, and aged, to obtain a T6 tempered material (which
is referred to as "water-cooled" in Table 2), and the following
tests were conducted.
(1) Tensile Test
[0024] Each of the materials was cut into a JIS No. 13B test
specimen, lines were drawn at intervals of 5 mm in the vertical
direction to the extruding direction in the parallel section of the
specimen, and the test was conducted at a tensile speed of 5
mm/min.
[0025] The elongation .alpha. (%) after rupture in the parallel
section of 5 mm, the 0.2% proof stress value .sigma. (MPa), and the
tensile strength (MPa) were measured, and the results are shown in
Table 2.
[0026] Tensile strength of 150 MPa or more is sufficient for use as
a structural member of an automobile.
[0027] Separately, each of the materials was cut into a JIS No. 13B
test specimen, and the tensile test was conducted in the same
manner as in the above, except that the gauge length was changed to
50 mm-interval, and the overall elongation (.epsilon. (%)) of each
specimen was measured.
[0028] The results are also shown in Table 2.
(2) Compression Test
[0029] As shown in FIG. 1, a shaped specimen of 300 mm in length
was loaded at a compressive speed of 10 mm/min, and the
energy-absorbing amount was determined from the load, which was
applied from the start of compression until compressive deformation
of 100 mm, and the amount of deformation. An example of measurement
of a displacement load curve in the compression test is given in
FIG. 2. The obtained energy-absorbing amount is shown in Table
2.
1TABLE 1 Alloy Composition (wt %) (balance Al) No. Si Fe Cu Mn Mg
Cr Zn Zr Ti Remarks 1 0.48 0.17 -- -- 0.5 -- -- -- 0.02 JIS 6063 2
0.35 0.19 -- -- 0.48 -- -- -- 0.02 JIS 6063 3 0.51 0.18 0.09 0.08
0.6 0.02 -- 0.03 0.01 JIS 6N01 4 0.7 0.22 0.08 0.09 0.72 0.02 0.01
0.03 0.02 JIS 6N01 5 0.71 0.23 0.25 0.06 1.11 0.23 -- -- 0.01 JIS
6061 6 0.09 0.22 0.08 0.12 0.73 0.02 5.54 0.18 0.02 JIS 7003 7 0.1
0.23 0.09 0.42 1.37 0.01 4.48 0.17 0.01 JIS 7N01 8 0.88 0.17 0.53
0.11 0.72 0.08 -- -- 0.03 --
[0030]
2TABLE 2 Aging condition Tensile Energy Alloy Hardening Temperature
Time .alpha. .sigma. .epsilon. strength absorption No. No.
condition .degree. C. hr % MPa .alpha. .times. .sigma. % .epsilon.
.times. .sigma. MPa kg .multidot. m Example 1 1 Air-cooled 200 2 42
198 8316 16.6 3287 230 13.9 Example 2 2 Air-cooled 180 10 34 196
6664 13.2 2587 217 13.4 Example 3 3 Air-cooled 190 1 36 176 6336
15.8 2781 236 12.4 Example 4 3 Water-cooled 160 8 28 244 6832 12.2
2977 269 16.2 Example 5 4 Air-cooled 180 6 26 249 6474 14.4 3586
277 16.5 Example 6 6 Air-cooled 150 12 36 262 9432 17 4454 314 16.6
Example 7 7 Air-cooled 120 24 30 315 9450 17 5355 357 17.2 Example
8 5 Water-cooled -- -- 52 147 7644 18.2 2675 238 12.3 Example 9 3
Air-cooled -- -- 48 134 6432 16.8 2251 225 12.2 Comparative 5
Water-cooled 170 10 20 329 6580 10 3290 341 7 Example 1 Comparative
4 Air-cooled 210 6 28 203 5684 13.4 2720 244 8.4 Example 2
Comparative 7 Air-cooled -- -- 22 241 5302 18.2 4386 361 9.3
Example 3 Comparative 8 Air cooled -- -- 34 147 4998 13.6 1999 268
9.8 Example 4 (Note) .alpha.: Rupture elongation at a gauge length
of 5 mm .sigma.: 0.2% proof stress .epsilon.: Overall elongation at
a gauge length of 50 mm
[0031] As is apparent from Table 2, in Examples 1 to 9 according to
the present invention, a quite large energy-absorbing amount was
obtained while maintaining the necessary material strength.
Contrary to the above, sufficient energy absorption was not
obtained in Comparative Examples 1 to 4, in which .alpha.<24%
and/or (.alpha..times..sigma.)<6000.
[0032] When the rupture elongation (.alpha.) and the value
(.alpha..times..sigma.) were within the range defined in the
present invention, an excellent energy-absorbing characteristics
were obtained.
[0033] By contrast, if evaluated by the overall elongation
(.epsilon.) instead of the rupture elongation (.alpha.), it is
understood that no correlative relation was recognized at all
between the magnitude of energy absorption and overall elongation
(.epsilon.) or (.epsilon..times..sigma.). That is, the rupture
elongation (.alpha.) and overall elongation (.epsilon.) have
different meanings as physical properties (value), and the overall
elongation (.epsilon.) cannot be used instead of the rupture
elongation (.alpha.) as a parameter of the energy-absorbing
characteristic. More specifically, different from the rupture
elongation (.epsilon.) of the very narrow gauge length of 5 mm
defined in the present invention, the overall elongation (.alpha.)
at the gauge length of 50 mm employed conventionally in the
evaluation could not be used as a means for defining or evaluating
the energy-absorbing characteristic, or for defining or evaluating
the material excellent in compression (crushing) buckling
resistance as an automotive structural member.
[0034] Having described our invention as related to the present
embodiments, it is our intention that the invention not be limited
by any of the details of the description, unless otherwise
specified, but rather be construed broadly within its spirit and
scope as set out in the accompanying claims.
* * * * *