DESCRIPTION
Title of Invention: Shock Absorbing Member
Technical Field
[ 0 0 0 1 ] The present invention relates to a shock
absorbing member which absorbs externally-applied impact
energy while buckling.
Background Art
[0002] In recent years, in the automotive field, etc.,
improvement in fuel efficiency and motion performance
have been sought, while improvement in collision safety
has also been sought. As a chassis of a motorcar, in
order to balance reduced weight and high stiffness, a
chassis structure referred to as a "monocoque body,"
wherein a frame and a body are integrally formed, is
generally used. Further, in the chassis of a motorcar,
in order to maintain a survival space for a driver and a
passenger in a collision, a shock absorbing structure is
generally used, wherein a space (for example, an engine
room or a luggage room) other than a cabin is
preferentially collapsed, so that impact load applied to
the cabin is attenuated as possible and the deformation
of the cabin is minimized.
[ 0 0 0 3 ] Therefore, in order to constitute a chassis
structure with high collision-safety performance, it is
important to how to effectively absorb the impact energy
at the time of collision. To this end, a shock absorbing
30 member for effectively absorbing the impact energy at the
time of collision has been strenuously developed (for
example, see Patent Literatures 1 to 15) .
[0004] Generally, as a shock absorbing member, a
hollow columnar thin-walled structure (or a hollow
35 columnar member) manufactured by jointing press-formed
steel plates by welding, etc., is used. In order to
balance reduced weight and high stiffness, as described
above, the shock absorbing member is constituted by a
hollow member having a polygonal cross-section such as a
tetragon or a hexagon. Such a shock absorbing member is
used as a front-side member of a chassis, for example,
and absorbs the impact energy by buckling in an axial
direction (or axial crushing) when impact load is applied
to one end of the member at the time of collision.
Therefore, in order to improve the shock-absorbing
performance, it is important to effectively generate such
buckling and increase the buckling load thereof.
[0005] In the prior art, in order to solve the above
problems in terms of material, a relatively thick or
relatively high-strength steel plate is used to
manufacture a shock absorbing plate so as to increase the
15 buckling load. On the other hand, as a structural
measure, a dimple (or a bead) providing the origin of the
buckling is arranged so as to effectively generate the
buckling. Further, by forming a cross-section of the
hollow shock absorbing member as a polygonal shape, the
20 buckling load is increased.
[0006] However, when the plate thickness of the above
shock absorbing member is increased, the weight of the
member is increased, whereby the weight of a chassis
including the shock absorbing member is also increased.
25 As a result, fuel efficiency and driving performance of a
motorcar are deteriorated. Further, in a high-strength
steel plate, the degree of elongation is generally
decreased in inverse proportion to the strength thereof.
Therefore, the formability of a high-strength steel plate
30 is not good, and thus there are limitations to increase
the strength of a steel plate for the shock absorbing
member at present.
[0007] Incidentally, when the buckling load of the
shock absorbing member is solely increased, a minimum
35 impact load for generating the buckling is increased. In
this case, the impact load applied to the shock absorbing
member is not absorbed by the deformation of the shock
absorbing member, whereby the impact load with no change
is transmitted to another structure such as a cabin.
Further, a risk of injury to driver and a passenger is
increased, since a portion which is not to be deformed is
buckled; it is difficult to keep a survival space for the
drive and the passenger due to the deformation of the
cabin; or a significant change of acceleration is applied
to the driver and the passenger.
[ 0 0 0 8 ] Therefore, for example, the shock absorbing
member is configured as a straight member in order to
keep the cross-section from a start end of the buckling
constant as possible, and secure a certain amount of
deformation due to the buckling. Further, in order to
reduce an initial impact load applied to the shock
absorbing member, the shock absorbing member is stably
buckled into concertinas due to an arrangement of the
beads as described above.
[0009] However, there is no firm theory for
determining the above arrangement of the beads, and at
present, the arrangement is determined by repeating
multiple times a buckling test or a computer simulation
regarding the shock absorbing member. Accordingly, it is
necessary to repeatedly carry out the above test or
simulation in relation to each kind of chassis, whereby
design efficiency is deteriorated. Moreover, since
various load conditions or buckling modes predicted when
actual collision cannot be dealt with, it is very
difficult to optimize the arrangement of the beads by
using the above techniques.
Citation List
Patent Literature
[ 0010 ] PLT 1: Japanese Unexamined Patent Publication
(kokai) No. 2009-286221
PLT 2: Japanese Unexamined Patent Publication (kokai)
No. 2009-285668
PLT 3: Japanese Unexamined Patent Publication (kokai)
No. 2009-168115
PLT 4: Japanese Unexamined Patent Publication (kokai)
No. 2009-154587
PLT 5: Japanese Unexamined Patent Publication (kokai)
No. 2009-113596
PLT 6: Japanese Unexamined Patent Publication (kokai)
No. 2008-018792
PLT 7: Japanese Unexamined Patent Publication (kokai)
NO. 2007-030725
PLT 8: Japanese Unexamined Patent Publication (kokai)
No. 2006-207726
PLT 9: Japanese Unexamined Patent Publication (kokai)
No. 2006-207724
PLT 10: Japanese Unexamined Patent Publication
(kokai) No. 2005-225394
PLT 11: Japanese Unexamined Patent Publication
(kokai) No. 2005-153567
PLT 12: Japanese Unexamined Patent Publication
(kokai) No. 2005-001462
PLT 13: Japanese Unexamined Patent Publication
(kokai) No. H10-138950
PLT 14: Japanese Unexamined Patent Publication
(kokai) No. H09-277954
PLT 15: Japanese Unexamined Patent Publication
(kokai) No. H09-277953
PLT 16: Japanese Unexamined Patent Publication
(kokai) No. 2011-056997
Summary of Invention
30 Problem to be Solved by the Invention
[OOll] Incidentally, in buckling modes (or compactmodes)
wherein the above shock absorbing member is
buckled into concertinas, a "concave-convex mixed mode"
and a "concave-convex independent mode" are included.
35 The concave-convex mixed mode is a deformation mode
wherein both a concave portion and a convex portion of
concertinas are present in an arbitrary transverse crosssection
of a hollow columnar shock absorbing member which
is buckled into concertinas by impact load. On the other
hand, the concave-convex independent mode is a
deformation mode wherein only a concave portion or a
convex portion is present in the arbitrary transverse
cross-section. In this regard, a ratio of a deformed
portion to the entire member in the concave-convex
independent mode is larger than that in the concaveconvex
mixed mode. Therefore, in the concave-convex
independent mode, an amount of impact energy absorption
relative to an amount of deformation (or an amount of
crushing) is relatively high, and thus improved shockabsorbing
performance can be obtained.
[0012] In a conventional shock absorbing member,
various approaches have been made for increasing the
amount of impact energy absorption while buckling the
member into concertinas in the axial direction. However,
there has been no approach for purposely induce the above
concave-convex independent mode. In other words, in the
compact mode of the conventional shock absorbing member,
the concave-convex mixed mode is a major mode, and a
mechanism for generating the concave-convex independent
mode has not been found.
[0013] The present invention was made in view of the
25 above background, and an object of the invention is to
provide a shock absorbing member having improved shockabsorbing
performance, in particular, a shock absorbing
member capable of purposely inducing the concave-convex
independent mode.
30
Means for Solving the Problem
[0014] In order to solve the above problems, the
present invention provides a hollow columnar shock
absorbing member comprising: an axis; a plurality of
35 rectangular walls extending parallel to the axis; and a
polygonal cross-section perpendicular to the axis, the
shock absorbing member extending in a direction of the
axis and being configured to absorb externally-applied
impact energy while buckling in the direction of the
axis, wherein the shock absorbing member has at least one
bead formed on at least one wall among the plurality of
walls, the at least one bead providing the origin of
buckling, and wherein the at least one bead is positioned
so as to be deviated towards one edge of a wall on which
the at least one bead is formed, the edge extending
parallel to the axis.
Effects of Invention
[OOlS] According to the present invention, a shock
absorbing member having improved shock-absorbing
performance can be provided, in particular, the shock
absorbing member can be effectively buckled in the
direction of the axis by purposely inducing the concaveconvex
independent mode. As a result, the amount of
externally-applied impact energy absorption is increased,
and improved shock-absorbing performance can be obtained.
Brief Description of Drawings
[0016] Fig. 1A is a perspective view of a hollow
linear columnar member having a square hollow crosssection,
wherein deformation of the member when impact
load is applied to one end thereof in an axial direction
is calculated by FEM numerical analysis, the view showing
a state in which the member is bent by local buckling.
Fig. 1B is a perspective view of a hollow columnar
member similar to Fig. lA, wherein deformation of the
30 member is calculated by FEM numerical analysis, the view
showing a non-compact mode in which the member is
irregularly buckled in the axial direction.
Fig. 1C is a perspective view of a hollow columnar
member similar to Fig. lA, wherein deformation of the
35 member is calculated by FEM numerical analysis, the view
showing a concave-convex mixed mode among compact modes
in which the member is buckled into concertinas in the
axial direction.
Fig. 1D is a perspective view of a hollow columnar
member similar to Fig. lA, wherein deformation of the
member is calculated by FEM numerical analysis, the view
showing a concave-convex independent mode among the
compact modes in which the member is buckled into
concertinas in the axial direction.
Fig. 2A is a schematic view for exemplifying an
arbitrary transverse cross-section perpendicular to an
axis of the hollow columnar member in the concave-convex
mixed mode.
Fig. 2B is a schematic view for exemplifying a
transverse cross-section, other than the cross-section of
Fig. 2A, perpendicular to the axis of the hollow columnar
15 member in the concave-convex mixed mode.
Fig. 3A is a schematic view for exemplifying an
arbitrary transverse cross-section perpendicular to the
axis of the hollow columnar member in the concave-convex
independent mode.
Fig. 3B is a schematic view for exemplifying a
transverse cross-section, other than the cross-section of
Fig. 3A, perpendicular to the axis of the hollow columnar
member in the concave-convex independent mode.
Fig. 4A is a schematic view for explaining a
25 function of a shock absorbing member, wherein a dimple is
formed as a bead on an outer surface of the shock
absorbing member.
Fig. 4B is a schematic view for explaining a
function of a shock absorbing member, wherein a bulge is
30 formed as a bead on an outer surface of the shock
absorbing member.
Fig. 5A is a transverse cross-sectional view of the
hollow columnar member after buckling, calculated by FEM
numerical analysis, showing the concave-convex
35 independent mode.
Fig. 5B is a transverse cross-sectional view of the
hollow columnar member after buckling, calculated by FEM
numerical analysis, showing the concave-convex mixed
mode.
Fig. 6A is a perspective view of a shock absorbing
member according to the present invention.
Fig. 6B is an enlarged view of a circle "A" in Fig.
6A.
Fig. 7A is a perspective view of a modification of a
shock absorbing member according to the present
invention.
Fig. 7B is a transverse cross-sectional view of the
shock absorbing member of Fig. 7A.
Fig. 8A is a perspective view of a shock absorbing
member of comparative example 1, showing a state before
impact load is applied to the shock absorbing member.
Fig. 8B is a perspective view of a shock absorbing
member of working example 1, showing a state before
impact load is applied to the shock absorbing member.
Fig. 8C is a perspective view of a shock absorbing
member of working example 2, showing a state before
impact load is applied to the shock absorbing member.
Fig. 8D is a perspective view of a shock absorbing
member of comparative example 2, showing a state before
impact load is applied to the shock absorbing member.
Fig. 8E is a perspective view of a shock absorbing
member of comparative example 3, showing a state before
impact load is applied to the shock absorbing member.
Fig. 9 is a perspective view of the shock absorbing
member of comparative example 1, wherein deformation
manner when impact load is applied to the shock absorbing
member is calculated by FEM numerical analysis.
Fig. 10 is a perspective view of the shock absorbing
member of working example 1, wherein deformation manner
when impact load is applied to the shock absorbing member
is calculated by FEM numerical analysis.
Fig. 11 is a perspective view of the shock absorbing
member of working example 2, wherein deformation manner
when impact load is applied to the shock absorbing member
is calculated by FEM numerical analysis.
Fig. 12 is a perspective view of the shock absorbing
member of comparative example 2, wherein deformation
manner when impact load is applied to the shock absorbing
member is calculated by FEM numerical analysis.
Fig. 13 is a perspective view of the shock absorbing
member of comparative example 3, wherein deformation
manner when impact load is applied to the shock absorbing
member is calculated by FEM numerical analysis.
Fig. 14A is a graph showing a measurement of a
relationship between a reactive force from the shock
absorbing member and an amount of deformation (crushing)
when impact load is applied to the shock absorbing
member, in relation to working example 1 and comparative
15 example 1.
Fig. 14B is a graph showing a measurement of a
relationship between a reactive force from the shock
absorbing member and an amount of deformation (crushing)
when impact load is applied to the shock absorbing
20 member, in relation to working example 2 and comparative
example 1.
Fig. 14C is a graph showing a measurement of a
relationship between a reactive force from the shock
absorbing member and an amount of deformation (crushing)
25 when impact load is applied to the shock absorbing
member, in relation to comparative examples 1 and 2.
Fig. 14D is a graph showing a measurement of a
relationship between a reactive force from the shock
absorbing member and an amount of deformation (crushing)
30 when impact load is applied to the shock absorbing
member, in relation to comparative examples 1 and 3.
Fig. 15A is a graph showing a measurement of a
relationship between an amount of energy absorption and
an amount of deformation (crushing) when impact load is
35 applied to the shock absorbing member, in relation to
working example 1 and comparative example 1.
Fig. 15B is a graph showing a measurement of a
relationship between an amount of energy absorption and
an amount of deformation (crushing) when impact load is
applied to the shock absorbing member, in relation to
working example 2 and comparative example 1.
Fig. 15C is a graph showing a measurement of a
relationship between an amount of energy absorption and
an amount of deformation (crushing) when impact load is
applied to the shock absorbing member, in relation to
comparative examples 1 and 2.
Fig. 15D is a graph showing a measurement of a
relationship between an amount of energy absorption and
an amount of deformation (crushing) when impact load is
applied to the shock absorbing member, in relation to
comparative examples 1 and 3.
Embodiments for Carrying out the Invention
[0017] Hereinafter, a shock absorbing member according
to the present invention will be explained in detail with
reference to the drawings.
In Figs. 1A to ID, various deformation modes are
illustrated, which are generated when impact load is
applied to one end of a hollow linear columnar shock
absorbing member in a direction of an axis thereof (or an
axial direction), the shock absorbing member having a
hollow square cross-section. The deformation modes as
shown in Figs. 1A to ID are calculated by FEM (Finite
Element Method) numerical analysis (or computer
simulation) when the shock absorbing member is deformed
by applied impact load.
[0018] Fig. 1A shows a state wherein the shock
absorbing member is bent by local buckling. On the other
hand, Fig. 1B shows a non-compact mode wherein the shock
absorbing member is irregularly buckled in the axial
direction. Figs. 1C and 1D show modes wherein the shock
35 absorbing member is buckled into concertinas in the axial
direction. In other words, Figs. 1C and 1D shows compact
modes wherein the member is crushed so that a peak and a
valley are alternately formed in the axial direction. In
particular, Fig. 1C shows a concave-convex mixed mode of
the compact modes. In the concave-convex mixed mode,
both the valley (or a concave portion) and the peak (or a
convex potion) of the concertinas are included in an
arbitrary transverse cross-section of a hollow columnar
member, as schematically shown in Figs. 2A and 2B. To
the contrary, Fig. ID shows a concave-convex independent
mode of the compact modes. In the concave-convex
independent mode, only the valley (or a concave portion)
or the peak (or a convex potion) of the concertinas is
included in an arbitrary transverse cross-section of a
hollow columnar member, as schematically shown in Figs.
3A and 3B. In addition, the "concave-convex independent
moden and the "concave-convex mixed mode" may also be
referred to as an "extension mode" and an "inextension
mode," respectively.
[0019] In such a case, a ratio of a deformed portion
to the entire member is increased as the deformation mode
is shifted from Fig. 1A to Fig. ID. Therefore, in the
concave-convex independent mode as shown in Fig. ID, an
amount of impact energy absorption relative to an amount
of deformation (crushing) of the member is the highest.
In other words, in the concave-convex independent mode,
the member can be buckled in the axial direction most
effectively, whereby significantly high impact-absorbing
performance can be obtained.
[0020] In the present invention, at least one bead is
formed on at least one wall among a plurality of walls of
30 the shock absorbing member, the at least one bead
providing the origin of buckling, and the at least one
bead being positioned so as to be deviated towards one
edge of a wall on which the at least one bead is formed,
the edge extending parallel to the axis. By virtue of
35 this, the concave-convex independent mode can be
purposely induced.
[0021] Concretely, in the present invention, a shock
absorbing member 1 with a hollow square cross-section, as
exemplified in Fig. 4A, has a center axis 0, four walls
la, lb, lc and Id positioned around center axis 0,
wherein a plurality of dimples 2a, 2b, 2c and 2d are
formed as beads on four walls la, lb, lc and Id,
respectively. Dimples 2a, 2b, 2c and 2d are positioned
while being deviated towards one edge of walls la, lb, lc
and Id. In detail, in the embodiment of Fig. 4A, in each
wall la, lb, lc and Id in a cross-section perpendicular
to center axis 0, four dimples 2a, 2b, 2c and 2d are
deviated towards edges or corners le, If, lg and lh which
are positioned on the same side relative to centers PC of
four walls la, lb, lc and Id in relation to a
circumferential direction as indicated by an arrow Y,
respectively. In addition, in this embodiment, a bottom
surface of each dimple 2a, 2b, 2c and 2d is formed as a
portion of a spherical surface.
[0022] In this case, as shown in Figs. 4A and 5A, by
applying impact load to one end of shock absorbing member
1 in a direction of the axis (or the axial direction),
the shock absorbing member begins to be buckled while a
ridge of each corner le, If, lg and lh is inclined in the
same circumferential direction (Y), i.e., towards the
side (in the X-direction) on which each dimple 2a, 2b, 2c
and 2d is arranged, respectively. By virtue of this, the
above concave-convex independent mode can be purposely
induced.
[0023] In other words, the bead in the invention
functions as a buckling-inducing part for purposely
inducing the concave-convex independent mode.
Concretely, the bead has a function for determining the
direction of the inclination of the ridge of each corner
so that the ridges are inclined in the same direction in
relation to the circumferential direction when the shock
35 absorbing member begins to be buckled in the axial
direction. Therefore, the bead of the invention is
different from a conventional bead having a function to
provide the origin (or the start point) of the buckling,
and does not directly become the origin of the buckling.
Rather, the bead of the invention has a function for
rapidly making the transition to the concave-convex
independent mode after the ridge of the corner is
inclined (or after the buckling).
[0024] On the other hand, in the concave-convex mixed
mode, as shown in Fig. 5B, when the member begins to be
buckled, the ridges of corners le, If, lg and lh are
inclined in different directions. As a matter of
convenience, each component in Fig. 5B equivalent to the
component in Fig. 5A is provided with the same reference
numeral as in Fig. 5A.
[0025] The shock absorbing member according to the
present invention can be effectively buckled in the axial
direction thereof, by purposely inducing the above
concave-convex independent mode. As a result, the amount
of externally-applied impact energy absorption is
increased, whereby remarkable shock-absorbing performance
can be obtained.
COO261 When such a shock absorbing member is used in a
chassis of a motorcar, etc., fuel efficiency and motion
performance are improved while balancing reduced weight
and high stiffness, and further, the chassis may have a
structure with high collision-safety performance.
[0027] Although shock absorbing member 1 as shown in
Fig. 4A is exemplified, the shock absorbing member of the
invention is not limited as such, and may have various
configurations. In other words, the invention may be
widely applied to a hollow columnar shock absorbing
member with a hollow polygonal cross-section, which
absorbs externally-applied impact energy while buckling
(or crushing) in the axial direction thereof.
[0028] Concretely, as the shock absorbing member, for
example, a thin-walled structure formed as a hollow
column (or a hollow columnar member), constituted by
joining a press-formed steel plates by welding, etc., may
be used. In this case, the bead may be formed by pressforming,
etc., before and/or after joining the hollow
columnar member.
[0029] A material of the shock absorbing member is not
limited to a steel plate as described above. For
example, the material may be a metal such as iron,
aluminum, copper or an alloy thereof; or a resin such as
an FRP, as long as the member can absorb externallyapplied
impact energy while buckling (or crushing) in the
axial direction thereof. Further, the shock absorbing
member is not limited to a member formed by joining
plates by welding, etc., and may be a hollow columnar
member formed by extrusion molding, etc. In this case,
the bead may be formed by press-forming, etc., after
forming the hollow columnar member. In addition, it is
preferable that the shock absorbing member have a hollow
cross-section with a triangular, quadrangular,
pentagonal, hexagonal, heptagonal or octagonal shape, for
example, in order to balance reduced weight and high
stiffness.
[ 0 0 3 0 ] The beads are not limited to the dimples of
concave portions formed on the outer surface of shock
absorbing member 1 as shown in Fig. 4A, and may be a
plurality of bulges which bulge from the outer surface of
25 shock absorbing member 1. With reference to Fig. 4B, a
shock absorbing member 1' with a hollow square crosssection
has four walls la', lb', lc' and Id' and a
plurality of bulges 2a', 2b1, 2c' and 2d' formed as beads
on four walls la', lb', lc' and Id', respectively.
30 Bulges 2a', 2b1, 2c' and 2d' are positioned while being
deviated towards corners lev, If', lg' and lh' which are
positioned on the same side relative to centers PC' of
four walls la', lb', lc' and Id' in relation to a
circumferential direction as indicated by an arrow Y,
35 respectively. In addition, each bulge 2a', 2b', 2c' and
2d' is formed as a portion of a spherical surface.
[ 0 0 3 1 ] When the beads correspond to a plurality
dimples formed on the outer surface of shock absorbing
member 1, as schematically shown in Fig. 4A, the shock
absorbing member begins to be buckled while the ridge of
each corner le, If, lg and lh is inclined in the
circumferential direction towards the side (in the Xdirection)
on which each dimple la, lb, lc and Id is
arranged, respectively. On the other hand, in shock
absorbing member 1' schematically shown in Fig. 4B, when
bulges 2a', 2b1, 2c' and 2d' bulging outward from the
outer surface of the member are positioned while being
deviated towards corners letf If', lg' and lh' which are
positioned on the same side in relation to a
circumferential direction as indicated by an arrow Y',
respectively, the shock absorbing member begins to be
buckled while the ridge of each corner lev, If', lg' and
lh' is inclined in the circumferential direction towards
an opposite side (in the XI-direction) of the side on
which each bulge la', lb', lc' and Id' is arranged,
respectively.
[0032] As shown in Figs. 6A and 6Bf the beads or
dimples 2 may be aligned in the axial direction, from a
start end of the buckling of shock absorbing member 1.
In this case, it is preferable that dimples 2 be
positioned at an interval corresponding to a length of
one side of the wall. Further, it is preferable that
dimple 2 closest to the start end be positioned so as to
be separated from the start end by a distance which is
more than a half of the length of one side of the wall.
By virtue of this, the shock absorbing member can be
stably buckled into concertinas. The above positioning
of the beads is also applicable to the case wherein the
beads are bulges protruding from the outer surface of
shock absorbing member 1.
[0033] The shape of the bead is not limited the above
35 dimple or bulge having a portion of a spherical surface,
as long as the bead has a function of the invention. For
example, the bead may have a V-shaped or U-shaped crosssection.
Dimple 2 as shown in Figs. 7A and 7B is
configured as a concave portion with a trough shape
extending in a direction (or a transverse direction)
perpendicular to the axial direction of shock absorbing
member 1. In this case, the function of the bead of the
invention may be further improved. Preferably, a length
L1 of trough-shaped concave portion 2, in a direction
perpendicular to axis 0 of shock absorbing member 1, is
represented as below, wherein "W" is a width of the wall
(or a distance between the ridges of shock absorbing
member 1) .
(l/lO)W I L1 I (3/4)W
Preferably, a length L2 of trough-shaped concave
portion 2, in a direction of axis 0 of shock absorbing
member 1, is represented as below.
(1/20)L1 I L2 I L1
Preferably, a distance L3 between concave portion 2
and the ridge is represented as below, wherein "T" is a
thickness of the plate.
T I L3 I (1/5)T
[ 0 0 3 4 ] According to the invention, by arranging the
bead on at least one of the walls constituting the hollow
cross-section of the shock absorbing member so that the
bead is deviated towards one corner of the wall, the
above concave-convex independent mode can be purposely
induced. In other words, in the invention, the bead
deviated towards one corner of at least one wall
functions as the origin for determining the direction of
the inclination of the ridge on the side towards which
the bead is deviated. Similarly, the.other ridges are
induced to incline in the same direction as the ridge of
the corner which becomes the origin.
[0035] However, in order that the corners are stably
inclined in the same direction, it is preferable that the
35 bead be deviated towards the corner in two or more walls.
More preferably, the bead is deviated towards the corner
in all of the walls. A portion of the hollow crosssection
of the shock absorbing member, to which the bead
is provided, will become a valley (or a concave portion)
of the concertinas after the buckling. Therefore, when
the bead is arranged on all of the walls, a corner in the
transverse cross-section, to which the bead is not
provided, can be prevented from being a peak (or a convex
portion) of the concertinas after the buckling. In
addition, when the bead is positioned so as to be
deviated towards the corner on the plurality of walls, it
is preferable that the wall constituting an opposing
corner of the hollow cross-section of the polygonal shape
is preferentially provided with the bead, in view of the
balance of arrangement of the beads.
[0036] In the invention, "the bead is positioned so as
to be deviated towards the corner" means that the bead is
displaced towards the corner so that the center of the
wall does not exist in the bead (i.e., the center is not
deformed). Further, it is preferable that the beads be
positioned in the vicinity of the corners which are
located on the same sides with respect to the
circumferential direction. In this regard, "in the
vicinity of the corner" means the position near the
corner so that the ridge of the corner does not exist in
the bead (i-e., the corner is not deformed), and a
distance between the center of the bead and the corner is
equal to or smaller than a quarter of a width of the
wall. In the invention, by positioning the bead in the
vicinity of the corner, the ridge of the corner can be
30 stably inclined. On the other hand, when the bead is
formed on the corner, the buckling is stably carried out,
whereas the load supported by the corner is decreased.
As a result, the amount of energy absorption due to the
buckling is decreased.
35 [0037] In addition, in the invention, by conforming
the direction of the deviation of the bead to a direction
of a torsional load applied to the shock absorbing
member, the impact absorbing performance of the shock
absorbing member is also effective for the torsional
load.
Examples
[0038] Hereinafter, the effect of the present
invention will be more clearly explained. The invention
is not limited to following examples, and numerous
modifications could be made thereto, without departing
from the basic concept and scope of the invention.
[0039] First, in relation to shock absorbing members
of working examples 1, 2 and comparative examples 1 to 3,
deformation states thereof were calculated by FEM
numerical analysis (computer simulation), when the impact
load is applied to one end of the member in the axial
direction of the member. As an analysis condition of the
FEM numerical analysis, a linear hollow columnar member
with a square hollow cross-section, having a plate
thickness of 1.4 mm, a side length of 50 mm and an axial
length of 300 mm, was used as a model. Material
constants of the model are indicated in table 1 as
follows.
[0040]
[Table 11
[0041] Then, the deformation state was calculated,
when a rigid wall with a weight of 1000 kg fell at a rate
of 4.44 m/s towards one end (or an upper end) of the
hollow columnar member. In this regard, a constitutive
30 equation used in the FEM numerical analysis was a Swift-
Cowper-Symonds equation, as follows. In addition, an
analysis time was 50 ms (milliseconds).
[0042]
Base Material
Four corners
K [GPa]
1.5
2.5
Eo
0.001
n
0.2
D [l/ms]
1 . 0 ~ 1 0 ~ ~
D [l/ms]
3.0
[ 0 0 4 3 ] Comparative example 1
As shown in Fig. 8A, in comparative example 1, the
bead was not provided to the hollow columnar member. In
this case, as shown in Fig. 9, although the concaveconvex
independent mode was represented for a moment in
initial stage of the buckling, the mode was change to the
concave-convex mixed mode immediately, and from that
time, the deformation progressed in the concave-convex
mixed mode.
100441 Working example 1
As shown in Fig. 8Bf in working example 1, a bead or
a dimple having a depth of 2.5 mm was arranged on each of
four walls constituting the hollow columnar member, so
that the beads were deviated towards corners positioned
on the same side with respect to the circumferential
direction. Further, the dimples were aligned in the
axial direction of the member at intervals of 50 mm. In
this case, as shown in Fig. 10, the bucking of the member
progressed in the concave-convex independent mode from
initial stage of the buckling.
[0045] Working example 2
As shown in Fig. 8C, in working example 2, a bead or
a dimple having a depth of 2.5 mm was arranged on each of
four walls constituting the hollow columnar member, so
that the beads were deviated towards corners positioned
on the same side with respect to the circumferential
direction. Further, the dimples were arranged in a row
only on an upper part of the member in the axial
direction of the member. In this case, as shown in Fig.
11, the bucking of the member progressed in the concaveconvex
independent mode from initial stage of the
buckling. In addition, it is predicted that, if the
buckling further progresses due to increase in the impact
load, the bucking will progress in the concave-convex
mixed mode, similarly to the case wherein the bead is not
arranged.
100461 Comparative example 2
As shown in Fig. 8D, in comparative example 2, a
groove extending in the axial direction was arranged on
each of four walls constituting the hollow columnar
member, so that the grooves were deviated towards corners
positioned on the same side with respect to the
circumferential direction. In this case, as shown in
Fig. 12, although the concave-convex independent mode was
represented for a moment in initial stage of the
buckling, the mode was change to the concave-convex mixed
mode immediately, and from that time, the deformation
progressed in the concave-convex mixed mode.
100471 Comparative example 3
As shown in Fig. 8E, in comparative example 3, a
groove extending in the axial direction was arranged on
each of three walls constituting the hollow columnar
20 member, so that the grooves were deviated towards corners
positioned on the same side with respect to the
circumferential direction. In this case, as shown in
Fig. 13, the bucking of the member progressed in the
concave-convex mixed mode from initial stage of the
25 buckling.
100481 Next, Figs. 14A to 14D indicate a result of
measurement of the relationship between a reactive force
from the shock absorbing member (or a resistive force of
the member against the impact energy) and an amount of
30 deformation (or an amount of crushing) when impact force
was applied to one end of the member in the axial
direction thereof, in relation to working examples 1, 2
and comparative examples 1 to 3. Figs. 14A to 14D
indicate the results of working example 1, working
35 example 2, comparative example 2 and comparative example
3, respectively, and each result is compared to a result
of comparative example 1. In this regard, since a
product of the reactive force from the shock absorbing
member and the amount of crushing corresponds to an
amount of energy absorption, the impact absorbing
performance of the member is improved as the reactive
force is increased.
[0049] Further, Figs. 15A to 15D indicate a result of
measurement of the relationship between the amount of
deformation (or the amount of crushing) and an amount of
energy absorption when impact force was applied to one
end of the member in the axial direction thereof, in
relation to working examples 1, 2 and comparative
examples 1 to 3. Figs. 15A to 15D indicate the results
of working example 1, working example 2, comparative
example 2 and comparative example 3, respectively, and
each result is compared to a result of comparative
example 1.
[0050] As shown in Figs. 14A to 14D and 15A to 15D, in
the shock absorbing member of working examples 1 and 2,
by inducing the concave-convex independent mode, a ratio
of the amount of energy absorption relative to the amount
of deformation (or crushing) was higher than comparative
example 1 having the concave-convex mixed mode. In other
words, the shock absorbing member of working examples 1
and 2 had improved shock absorbing performance.
[Reference Signs List]
[0051]
1 shock absorbing member
1 ' shock absorbing member
la wall
lb wall
lc wall
Id wall
la' wall
lb' wall
lc' wall
Id' wall
le
I f
l g
lh
l e '
I f '
19 '
l h '
2a
2b
2c
2d
2a'
2b'
2c'
2d'
corner
corner
corner
corner
corner
corner
corner
corner
dimple
dimple
dimple
dimple
bulge
bulge
bulge
bulge

[Claim 11
- 13 -
-
CLAIMS (10 764 0 3 FEB 2014
A hollow columnar shock absorbing member comprising:
an axis;
a plurality of rectangular walls extending
parallel to the axis; and
a polygonal cross-section perpendicular to the
axis, the shock absorbing member extending in a direction
of the axis and being configured to absorb externally-
10 applied impact energy while buckling in the direction of
the axis,
wherein the shock absorbing member has at least
one bead formed on at least one wall among the plurality
of walls, the at least one bead providing the origin of
15 buckling, and
wherein the at least one bead is positioned so
as to be deviated towards one edge of a wall on which the
at least one bead is formed, the edge extending parallel
to the axis.
[Claim 21
The shock absorbing member according to claim 1,
wherein the at least one bead has one bead formed on one
wall.
[Claim 31
The shock absorbing member according to claim 1,
wherein the at least one bead includes a plurality of
beads.
[Claim 41
The shock absorbing member according to claim 3,
30 wherein the plurality of beads are positioned on a
straight line in the direction of the axis on one wall at
regular intervals.
[Claim 51
The shock absorbing member according to claim 3,
35 wherein the plurality of beads are arranged on at least
two of the plurality of walls one-by-one, and are
positioned in the same plane perpendicular to the axis
and in the vicinity of edges on the same side with
14
respect to a circumferential direction about the axis of
the shock absorbing member.
[Claim 61
5 The shock absorbing member according to claim 3,
wherein the same number of beads are arranged on each of
at least two of the plurality of walls, and are
positioned in a plurality of planes perpendicular to the
axis and in the vicinity of edges on the same side with
10 respect to a circumferential direction about the axis of
the shock absorbing member, so that the beads are
positioned on straight lines extending in the direction
of the axis.
[Claim 71
15 The shock absorbing member according to any one of
claims 1 to 6, wherein the bead includes a dimple formed
on an outer surface of shock absorbing member.
[Claim 81
The shock absorbing member according to claim 7,
20 wherein the bead is a concave portion with a trough shape
extending in a direction perpendicular to the direction
of the axis of the shock absorbing member.
[Claim 91
The shock absorbing member according to any one of
25 claims 1 to 6, wherein the bead includes a budge which
bulges from an outer surface of the shock absorbing
member.
[Claim 101
The shock absorbing member according to claim 4 or
30 6, wherein the beads are aligned in the direction of the
axis, from a start end of buckling of the shock absorbing
member.
Dated this 3rd day of February, 2014
[SWATI PAHUJA]
OF REMFRY & SAGAR
ATTORNEY FOR THE APPLICANT[S]