Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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DESCRIPTION
Title of Invention: Method of Forming Metal Sheet and Formed
Part
Technical Field
[0001] The present invention relates to a method of
forming a metal sheet in which no breakage occurs during
forming such as by drawing, stretch flanging, bending, and
stretch forming and a formed part formed by that method of
forming.
Background Art
[0002] Usually, the formability of a metal sheet falls
the more the strength of the metal sheet rises. For this
reason, when forming a particularly high strength metal
sheet, if the portion to be formed cannot plastically deform
enough, the internal stress will exceed the breaking yield
strength and the sheet will break.
[0003] FIG. 1 shows a mode of breakage at a shoulder part
of a punch when drawing a metal sheet. The blank material 1
of the metal sheet is drawn by pressing a flange part l' of
a blank material 1 in a die 2 by a blank holder 4 while
pressing it by a punch 3. Drawing proceeds by a balance of a
breaking yield strength of the blank material 1 at the
shoulder part 3' of the punch 3 and the pulling force acting
on the flange part l' of the blank material 1.
[0004] Further, when a deformation resistance 6 of the
flange part 1' becomes equal to the breaking yield strength
of the blank material 1 contacting the shoulder part 3' of
the punch 3, the flange part 1' stops deforming (being
pulled into the die 2). On the other hand, deformation
proceeds at only the portion of the blank material 1
contacting the shoulder part 3' of the punch 3 resulting in
breakage.
[0005] To avoid breakage when drawing a blank material, a
high breaking yield strength of the portion contacting the
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shoulder part of the punch is important. Up until now,
several arts have been proposed for preventing breakage of a
blank material at the time of a drawing operation.
[0006] PLT 1 proposes a method of press-forming a blank
material during which a location of the blank material where
a reduction in thickness is anticipated is provided with two
or more weld beads and then the press-forming operation is
performed.
[0007] PLT 2 proposes a tailored blank material for
press-forming use excellent in deep drawability obtained by
welding a high scrength steel sheet having a 15% or more
lower strength and sheet thickness than the material at a
center part or a 5% or more better ductility than the
material of the center part with another steel sheet forming
the center part over the entire circumference of a drawn
flange part at a part imparting a wrinkle suppressing force
at the time of forming at the outside the part becoming the
final product after deep drawing.
[0008] However, in each of the above arts, at the weld
input heat part of the blank material, the material becomes
brittle and the material of the blank material becomes
uneven, so it is difficult to completely avoid breakage of
the blank material at the time of a press-forming operation.
Citation List
Patent Literature
[0009] PLT 1. Japanese Patent Publication No. 10-175024A
PLT 2. Japanese Patent No. 4532709B
Summary of Invention
Technical Problem
[0010] In general, as techniques for preventing breakage
when forming a metal sheet, roughly classified, improvement
of the forming process and improvement of the material of
the metal sheet may be considered. For example, for
improvement of the drawing process, the method of division
of the dies and increase of the number of pressing processes
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may be considered, but with these methods, a rise in the
forming costs and fall in the productivity are unavoidable.
[0011] PLTs 1 and 2 disclose improvement of the material
of the high strength steel sheet by changing (strengthening)
the material by partial hardening or bonding with different
materials. However, with these methods as well, similarly, a
rise in the forming costs and fall in the productivity are
unavoidable.
[0012] Therefore, the present invention has as its
problem preventing a metal sheet from breaking when forming
a metal sheet without changing the material of the metal
sheet and the forming process and has as its object the
provision of a method of forming solving that problem and a
formed part formed by that method of forming.
Solution to Problem
[0013] The inventors studied in-depth means for solving
the above problem. As a result, the inventors discovered
that when forming a metal sheet, if bonding a reinforcement
to a portion where breaking yield strength is required, the
breaking yield strength at the above portion is improved and
breakage can be prevented.
[0014] The present invention was made based on the above
discovery and has as its gist the following:
[0015] (1) A method of forming a metal sheet comprising
the steps of bonding a reinforcement with a part of the
metal sheet and then forming the metal sheet.
[0016] (2) The method of forming a metal sheet according
to (1), wherein the reinforcement is bonded with a portion
of the metal sheet reduced in thickness in the
formingprocess.
[0017] (3) The method of forming a metal sheet according
to (1) or (2), wherein the metal sheet is a high strength
steel sheet having a tensile strength of 590 MPa or more.
[0018] (4) The method of forming a metal sheet according
to any one of (1) to (3), wherein the reinforcement is a
fiber reinforced plastic.
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[0019] (5) The method of forming a metal sheet according
to (4), wherein the fiber reinforced plastic is bonded so
that the direction of the fibers runs along the direction in
which the breaking strength of the metal sheet is required.
[0020] (6) The method of forming a metal sheet according
to any one of (1) to (3), wherein the reinforcement is a
high strength steel foil.
[0021] (7) A formed part drawn by the method of forming
of a high strength steel sheet according to any one of (1)
to (6).
[0021a] A method of forming a metal sheet into a formed
part having a reinforced portion. The method comprises the
steps of: bonding a sheet of fiber reinforced plastic to a
portion of the metal sheet where improved breaking yield
strength is required; and forming the reinforced metal
sheet into the formed part having a reinforced portion. A
bonding location of the sheet of fiber reinforced plastic
is determined based on a thickness of a portion of the
metal sheet that is predicted, by computer aided
engineering (CAE), to be reduced, during the forming, to a
thickness where internal stress-dependent breakage is
likely to occur during the forming step if the sheet of
fiber reinforced plastic is not bonded thereto, thereby
improving the breaking yield strength of the formed part.
[0021b] In embodiments of the above aspect, the fiber
reinforced plastic is bonded such that a direction of the
fibers runs along a direction in which the breaking yield
strength is required.
Advantageous Effects of Invention
[0022] According to the present invention, when forming a
metal sheet, it is possible to raise the breaking yield
strength of a portion where breaking yield strength is
required, improve the formability of the metal sheet, and
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prevent breakage during drawing without changing the
material of the metal sheet and the forming process.
Brief Description of Drawings
[0023] FIG. 1
is a view showing a mode of breakage at a
shoulder part of a punch when drawing high strength steel
sheet.
FIG. 2 is a view showing a mode of preventing breakage by
bonding a sheet of fiber reinforced plastic with a portion
where breaking yield strength is required when drawing high
strength steel sheet.
FIGS. 3A and 3B are views showing a mode of bonding a
reinforcement comprised of fiber reinforced plastic with a
portion where breaking yield strength is required when
drawing a high strength steel sheet. FIG. 3A shows the mode
of bonding ring-shaped fiber reinforced plastic to a ring-
shaped portion where breaking yield strength is required,
while FIG. 3B shows a cross-section of a formed part
obtained by drawing the blank material shown in FIG. 3A.
FIGS. 4A and 4B are views showing another mode of bonding a
reinforcement comprised of fiber reinforced plastic with a
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portion where breaking yield strength is required when
drawing a high strength steel sheet. FIG. 4A shows the mode
of bonding ring-shaped fiber reinforced plastic to two ring-
shaped portions where breaking yield strength is required,
while FIG. 4B shows a cross-section of a formed part
obtained by drawing the blank material shown in FIG. 4A.
FIG. 5 is a view showing a mode of bonding reinforcements
comprised of divided patches of ring-shaped fiber reinforced
plastic at a ring-shaped portion where breaking yield
strength is required.
FIG. 6 is a view showing the position of a punch shoulder
expected to become a portion where breakage in deep drawing
is a concern.
FIG. 7 is a view showing the position of a flange end
expected to become a portion where breakage in stretch
flanging is a concern.
FIG. 8 is a view showing a position of bending expected to
become a portion where breakage in bending is a concern.
FIG. 9 is a view showing a position of a punch stretching
portion expected to become a portion where breakage in
stretch forming is a concern.
FIG. 10 is a chart showing the flow for determining the
position where the reinforcement is bonded when forming a
metal sheet of a complicated shape where it is difficult to
predict a portion where breaking yield strength will be
required.
FIG. 11 is a view showing a method of bonding a sheet of
fiber reinforced plastic with a portion of high strength
steel sheet where breaking yield strength is required.
FIGS. 12A and 12B are views showing the case of a drawing
operation withouz a sheet of fiber reinforced plastic bonded
to a portion where breaking yield strength is required when
drawing high strength steel sheet and the case of a drawing
operation with a sheet of fiber reinforced plastic bonded.
FIG. 12A shows the case of a drawing operation without
bonding a sheet of fiber reinforced plastic with a portion
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where breaking yield strength is required, while FIG. 12B
shows the case of a drawing operation while bonding a sheet
of fiber reinforced plastic with a portion where breaking
yield strength is required.
Description of Embodiments
[0024] The method of forming a metal sheet of the present
invention is a method of forming a metal sheet comprising
drawing a sheet with a reinforcement bonded in advance to a
portion where breaking yield strength is required (below,
referred to as "a portion where breakage is a concern").
[0025] The formed part of the present invention is
characterized by being formed by the method of forming of
the present invention.
[0026] The method of forming of the present invention
will be explained based on the drawings.
[0027] FIG. 2 shows as one example of the present
invention a mode of drawing a high strength steel sheet
wherein a sheet of fiber reinforced plastic is bonded with a
portion where breaking yield strength is required so as to
prevent breakage.
[0028] A blank material 1 of a high strength steel sheet
is drawn by pressing a flange part l' of the blank material
1 in a die 2 by a blank holder 4 while pressing it by a
punch 3. Drawing proceeds by a balance of the breaking yield
strength of the blank material 1 at the shoulder part 3' of
the punch 3 and the pulling force acting on the flange part
1' of the blank material 1.
[0029] Further, as explained above, when a deformation
resistance 6 of the flange part l' becomes equal to the
breaking yield strength of the blank material 1 contacting
the shoulder part 3' of the punch 3, the flange part 1'
stops deforming (being pulled into the die 2). On the other
hand, deformation proceeds at only the portion of the blank
material 1 contacting the shoulder part 3' of the punch 3
resulting in breakage (see FIG. 1).
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[0030] On the other hand, when drawing high strength
steel sheet shown in FIG. 2, a reinforcement comprised of a
sheet of fiber reinforced plastic 8 is bonded in advance
with a portion 7 where breaking yield strength is required
and then the drawing operation is performed.
[0031] In drawing the blank material 1, if bonding a
sheet of fiber reinforced plastic 8 with a portion where
breakage during drawing is a concern, that is, the portion 7
where breaking yield strength is required, the breaking
yield strength is improved at the portion 7 where breaking
yield strength is required and the blank material 1 will not
break during drawing.
[0032] FIG. 2 shows a mode of bonding a fiber reinforced
plastic sheet 8 so as to surround a bottom part of a drawn
part so that during drawing of high strength steel sheet,
the fiber reinforced plastic sheet 8 reliably bonds with the
portion 7 where breaking yield strength is required and can
sufficiently exert the function of improving the breaking
yield strength. The mode of bonding the reinforcement to the
portion where breaking yield strength is required is not
limited to the mode of bonding shown in FIG. 2. Various
modes of bonding can be employed so long as reliably bonding
the reinforcement with the portion where breaking yield
strength is required. This point will be explained later
while showing another bonding mode.
[0033] The technique of bonding with a formed part a
sheet or patch of carbon fiber reinforced plastic (CFRP)
formed separately matching the shape of the formed part to
improve the mechanical properties or functionality of the
formed part or reinforce it has been known (for example, see
FY2010 Report on Project for Assisting Advancement of
Strategic Basic Technologies, "Research Relating to Press-
Forming Technology for CFRP-Metal Hybrid Parts for
Automobile Struc:.ural Members", and FY2014 Proceedings of
the Japanese Spring Conference for the Technology of
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Plasticity, "Basic Studies on Reinforcing Effect of CFRP
Sheet in Impact Bending Deformation in Tubular State").
[0034] However, the method of forming of the present
invention has as its basic idea bonding a reinforcement with
a forming material (blank material) before a forming
operation so as to raise the formability of the portion with
the sheet or patch bonded to it. On this point, the method
of forming of the present invention basically differs from
the above technique of bonding a sheet or patch of fiber
reinforced plastic to a formed part after the forming
operation so as to improve the mechanical properties or
functionality of the formed part or reinforce it.
[0035] That fact that when forming a blank material 1, if
bonding a fiber reinforced plastic sheet with a portion
where breakage during forming is a concern, that is, a
portion where breaking yield strength is required, the
breaking yield strength is improved in a portion where
breaking yield strength is required and the blank material
will not break during forming is a new discovery obtained by
the inventors and is the characterizing feature of the
method of forming of the present invention.
[0036] FIGS. 3A and 3B show a mode in drawing high
strength steel sheet where a patch of fiber reinforced
plastic is bonded with a portion where breaking yield
strength is required. FIG. 3A shows a mode where a patch of
ring-shaped fiber reinforced plastic is bonded to a ring-
shaped portion where breaking yield strength is required,
while FIG. 3B shows a cross-section of a formed part
obtained by drawing the blank material shown in FIG. 3A.
[0037] In the blank material 1 shown in FIG. 3A, a
reinforcement comprised of a ring-shaped fiber reinforced
plastic sheet 8a is bonded so as to cover a portion where
breakage during drawing is a concern, that is, a ring-shaped
portion abutting against a shoulder part of the punch and
requiring breaking yield strength.
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[0038] As shown in FIG. 3A, when drawing high strength
steel sheet, if it were possible to identify before drawing
the portion where breakage during drawing is a concern, that
is, the portion abutting against the shoulder part of the
punch and where breaking yield strength is thus required, it
would be possible to bond a sheet of fiber reinforced
plastic wider than the width of the identified portion so as
to completely cover the identified portion and thereby raise
the breaking yield strength and improve the formability at
that portion.
[0039] As shown in FIG. 32, in the formed part la
obtained by drawing the blank material shown in FIG. 3A, no
breakage occurs at the portion with which the fiber
reinforced plastic sheet 8a is bonded and where breakage
during drawing is a concern, that is, the portion abutting
against the shoulder part of the punch and where breaking
yield strength is thus required.
[0040] FIGS. 4A and 4B show another mode when drawing
high strength steel sheet where patches of fiber reinforced
plastic are bonded to portions where breaking yield
strength is required. FIG. 4A shows a mode where patches of
ring-shaped fiber reinforced plastic are bonded to two ring-
shaped portions where breaking yield strength is required,
while FIG. 42 shows a cross-section of a formed part
obtained by drawing the blank material shown in FIG. 4A.
[0041] In the blank material 1 shown in FIG. 4A, ring-
shaped fiber reinforced plastic sheet 8b and 8c are bonded
so as to cover the portions where breakage during drawing is
a concern, that is, the two ring-shaped portions abutting
against the shoulder parts of a punch and requiring breaking
yield strength.
[0042] As shown in FIG. 4A, when drawing high strength
steel sheet, even if there were a plurality of portions
where breakage during drawing was a concern, that is, the
portions abutting against the shoulder parts of the punch
and where breaking yield strength is thus required, if it
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were possible to identify the positions of those portions,
it would be possible to bond a sheet of fiber reinforced
plastic so as to completely cover the identified portions
and thereby raise the breaking yield strength and improve
the formability at those identified plurality of portions.
[0043] As shown in FIG. 4B, in the formed part lb
obtained by drawing the blank material shown in FIG. 4A, no
breakage occurs at the portions to which the fiber
reinforced plastic sheets Ob and Sc are bonded and where
breakage during drawing is a concern, that is, two ring-
shaped portions abutting against the shoulder parts of the
punch and where breaking yield strength is thus required.
[0044] FIGS. 3A and 3B and FIGS. 4A and 4B show the case
of drawing a circular blank material axially symmetrically,
but the blank material is not limited to a circular blank
material. Further, the drawing operation is not limited to
drawing axially symmetrically.
[0045] According to the method of forming of the present
invention, the breaking yield strength of a portion where
breaking yield strength is required (a portion where
breakage is a concern) is improved, so the freedom of shape
of the blank material, freedom of the forming mode, and
freedom of shape of the formed part are greatly expanded.
[0046] In the method of forming of the present invention,
when drawing a blank material, if it were possible to
identify a portion where breakage is a concern, that is, a
portion abutting against d shoulder part of a punch and.
where breaking yield strength is required, it would be
possible to bond a reinforcement so as to cover the
identified portion and raise the breaking yield strength and
prevent breakage at the above identified portion.
[0047] FIGS. 3A and 38 and FIGS. 4A and 4B show the
states when bonding reinforcements comprised of ring-shaped
sheets of fiber reinforced plastic to portions where
breaking yield strength is required. The shape of the
reinforcement is not limited to a specific shape and may be
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suitably set in accordance with the shape, position, etc. of
the identified portion where breaking yield strength is
required.
[0048] FIGS. 3A and 3B and FIGS. 4A and 4B show modes of
bonding ring-shaped sheets of fiber reinforced plastic to
the outsides of portions where breaking yield strength is
required, but the locations of bonding the reinforcement are
not limited to the outsides of the portions where breaking
yield strength is required. They may be any of the inside,
outside, and two sides of the portion where breaking yield
strength is required. The locations of bonding the
reinforcement may be suitably set according to the shapes,
positions, etc. of the portions where breaking yield
strength is required.
[0049] Furthermore, when bonding a reinforcement to a
portion where breaking yield strength is required, it may
also be bonded divided into suitable sections.
[0050] FIG. 5 shows a mode of bonding a reinforcement
comprised of divided sections of ring-shaped fiber
reinforced plastic to a ring-shaped portion where breaking
yield strength is required. In FIG. 5, the ring-shaped fiber
reinforced plastic is divided into four sections. The
sections of fiber reinforced plastic 8a' are bonded arranged
in a ring shape.
[0051] When joining a divided reinforcement, the mode of
division may be suitably determined according to the shape,
position, etc. of the portion where the specified breaking
yield strength is required.
[0052] Above, the method of forming of the present
invention was explained with reference to the example of a
drawing operation. The method of forming of the present
invention is not however limited to a drawing operation. It
may also be applied to various forming operations such as
shown in FIGS. 6 to 9. FIGS. 6 to 9 show portions where
breakage is a concern in various forming operations. FIG. 6
shows deep drawing, FIG. 7 shows stretch flanging, FIG. 8
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shows bending, and FIG. 9 shows stretch forming. If such
general forming operations, a portion where breakage is a
concern can be predicted relatively easily.
[0053] Specifically, when deep drawing, the portion where
breakage is a concern is the punch shoulder 61, with stretch
flanging, it is the flange end 71, with bending, it is the
bent portion 81, and with stretch forming, it is the punch
stretching portions 91. Therefore, before forming the metal
sheet, it is sufficient to bond a reinforcement and then
performing forming so as to cover a position forming that
portion at the time of forming.
[0054] When forming a metal sheet of a complicated shape
where a portion where breaking yield strength is required
would be difficult to predict, as shown in FIG. 10, CAE
(computer aided engineering) may be used to predict a
portion where thickness would be reduced if not using a
reinforcement and where breakage is thus a concern and then
forming in the case of bonding a reinforcement at that
portion where breakage is a concern may be again analyzed by
CAE so as to determine the position for bonding the
reinforcement.
[0055] The reinforcement is not particularly limited in
grade so long as one able to bear the stress applied to the
portion where breakage during forming is a concern. If
considering the strength and ease of handling, a sheet of
fiber reinforced plastic or high strength steel foil is
preferably used. The fiber reinforced plastic need only be a
plastic reinforced by a fiber. It is not limited to any
specific fiber or plastic. As a suitable example, carbon
fiber reinforced plastic may be mentioned. As high strength
steel foil, steel foil having a tensile strength at ordinary
temperature of 600 MAa or more can be illustrated.
[0056] When using a reinforcement comprised of fiber
reinforced plastic, the fiber reinforced plastic is
preferably bonded so that the direction of the fibers runs
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along the direction in which breaking yield strength is
required, specifically, cuts across any crack formed.
[0057] The reinforcement is designed to improve the
breaking yield strength at the portion where breaking yield
strength is required, so a required thickness is necessary,
but the material is not limited to a specific thickness. The
thickness of the reinforcement may be suitably set
considering the grade of the blank material, the mode of
drawing, the shape of the formed part, etc.
[0058] The formed part obtained by forming a blank
material with a reinforcement bonded to the portion where
breaking yield strength is required may, depending on the
application, be used after removing the reinforcement or may
be used with the reinforcement remaining bonded as it is.
[0059] For this reason, the bonding strength when bonding
a reinforcement with a portion where breaking yield strength
is required may be suitably selected in accordance with the
application of the formed part.
[0060] The method of bonding the reinforcement with a
portion where breaking yield strength is required is not
particularly limited. When the reinforcement is fiber
reinforced plastic, an adhesive or resin is preferably used.
The types of the adhesive and resin are not particularly
limited. It is also possible to consider whether to remove
the reinforcement from the formed part or leave it as it is
so as to suitably select the adhesive. If the reinforcement
is high strength steel foil and the reinforcement does not
have to be removed from the formed part, it may be bonded by
diffusion bonding.
[0061] Here, the mechanism by which bonding of a
reinforcement improves the breaking yield strength and
improves the formability will be explained.
[0062] In general, when drawing a blank material by a die
and a punch, the breaking yield strength Pbreak of the blank
material abutting against a shoulder part of the punch can
be calculated by the following formula (1) (see Plastic
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Forming Technology Series 13 "Press Drawing - Process Design
and Die Design -" (Corona), page 23):
Pbreak=27tRt0Ff2(r+1)(r+2)/3(2r+1)1 (n+ 1 ) /2
(11/e)n ===(1)
where,
R: radius of punch
to: thickness of blank material
r: Lankford value
e: Napier's constant (base of natural logarithm)
F, n: parameters of Swift formula
[0063] The breaking yield strength P'break of the blank
material when reinforcing by a reinforcement a portion of
the blank material where breakage is a concern (portion
where breakage during drawing is a concern), that is, a
portion abutting against a shoulder part of the punch and
where breaking yield strength is thus required, can be
calculated by the following formula (2) :
P' break=Pbreak+2nRtfrpTSfrp = = . (2)
P'break: breaking yield strength of blank material abutting
against shoulder part of punch
210 R: radius of punch
tfrp: thickness of reinforcement
TSfrp: tensile strength of reinforcement
[0064] As shown in the above formula (2), if bonding a
sheet or patch of fiber reinforced plastic as a
reinforcement with a portion of the blank material where
breakage is a concern, the breaking yield strength P'break
after bonding will exceed the breaking yield strength Pbreak
of the blank material, so it is possible to estimate the
improvement in formability at the above portion where
breakage is a concern. In this way, the method of forming of
the present invention can be theoretically verified.
[0065] The method of forming of the present invention
exhibits its effect without regard to the worked material,
that is, the metal sheet, and the content of the forming
operation. In particular, it exhibits a large effect in
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forming high strength steel sheet with a tensile strength of
590 MPa or more - which tends to become low in formability.
Examples
[0066] Next, an example of the present invention will be
explained, but the conditions in the example are an
illustration of the conditions employed for confirming the
workability and effect of the present invention. The present
invention is not limited to this illustration of conditions.
The present invention can employ various conditions so long
as not deviating from the gist of the present invention and
achieving the object of the present invention.
[0067] Example
As shown in FIG. 11, on a thickness 1.0 mm, diameter 108 mm
blank material (dual phase steel) 112, a thickness 0.7 mm,
diameter 58 mm adhesive sheet (polypropylene resin sheet)
113 and thickness 0.23 mm, diameter 52 mm sheet of carbon
fiber reinforced plastic 111 were stacked in that order. The
assembly was heated by a hot crimping machine 114 at 180 C
for 1 minute, then pressed at 0.049 MPa (L=5 tonf/m2) for 1
minute and air-cooled to bond the carbon fiber reinforced
plastic 111 with the blank material 112.
[0068] The blank material 112 with the carbon fiber
reinforced plastic 111 bonded to it was drawn using the
punch and die used in the comparative example.
[0069] Comparative Example
A thickness 1.0 mm, diameter 108 mm blank material (dual
phase steel) was drawn using the following punch and die:
Punch shoulder: R5
Punch diameter: 50 mm
Die shoulder: R5
Die diameter: 60 mm
Blank holder pressure: 0.098 MPa (Lt10 tonf/m2)
[0070] .. The results are shown in FIG. 12. (a) shows the
results of a comparative example of drawing a portion where
breaking yield strength is required to which a sheet of
fiber reinforced plastic is not bonded, while (b) shows the
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results of an example of drawing a portion where breaking
yield strength is required to which a sheet of fiber
reinforced plastic is bonded.
Industrial Applicability
[007].] According to the present invention, when forming a
metal sheet, it is possible to raise the breaking yield
strength of a portion where breaking yield strength is
required, improve the formability of the metal sheet, and
prevent breakage during forming without changing the
material of the metal sheet and the forming process. The
present invention exhibits its effect regardless of the
worked material, that is, the metal sheet, and the content
of the forming operation. In particular, it exhibits a great
effect for operations on high strength steel sheet where the
formability tends to become low like drawing, stretch
forming, stretch flanging, and bending. The present
invention has high applicability in industries manufacturing
metal products.
Reference Signs List
[0072] 1. blank material
1'. flange part
la, lb. formed part
2. die
3. punch
3'. shoulder part
4. blank holder
5. breakage
6. deformation resistance
7. portion where breaking yield strength is required
8. sheet of fiber reinforced plastic
8a, 8a'. reinforcement of fiber reinforced plastic
8b, 8c. reinforcement of fiber reinforced plastic
61. punch shoulder
71. flange end
81. bent portion
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91. punch stretching portion
111. sheet of carbon fiber reinforced plastic
112. blank material
113. adhesive sheet
114. hot crimping machine.
