U.S. patent application number 17/105138 was filed with the patent office on 2021-06-03 for method for forming large-size curved thin-walled metal skin.
The applicant listed for this patent is DALIAN UNIVERSITY OF TECHNOLOGY. Invention is credited to Xiaobo Fan, Zhubin He, Jianshu Liu, Jiangxiang Yu.
Application Number | 20210162482 17/105138 |
Document ID | / |
Family ID | 1000005286973 |
Filed Date | 2021-06-03 |
United States Patent
Application |
20210162482 |
Kind Code |
A1 |
He; Zhubin ; et al. |
June 3, 2021 |
METHOD FOR FORMING LARGE-SIZE CURVED THIN-WALLED METAL SKIN
Abstract
A method for forming a large-size curved thin-walled metal skin
is disclosed, wherein the position and size characteristics of
stiffeners on a curved panel is extracted; the thickness of the
curved panel and the thin-walled skin after assembly is assumed to
be m, and a forming surface of the punch is offset outwards along a
normal line by the thickness m to obtain the characteristics of the
inner surface of a female die; the number of the discrete support
moulds is set to be the same as the number n of the stiffeners
based on the size and distribution of the stiffeners on the curved
panel; and the punch and the female die combined with the discrete
support moulds are used to carry out stamping of a curved
thin-walled slab to obtain a required thin-walled skin
component.
Inventors: |
He; Zhubin; (Dalian, CN)
; Liu; Jianshu; (Dalian, CN) ; Fan; Xiaobo;
(Dalian, CN) ; Yu; Jiangxiang; (Dalian,
CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DALIAN UNIVERSITY OF TECHNOLOGY |
Dalian |
|
CN |
|
|
Family ID: |
1000005286973 |
Appl. No.: |
17/105138 |
Filed: |
November 25, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B21D 22/02 20130101;
B21D 37/10 20130101 |
International
Class: |
B21D 37/10 20060101
B21D037/10; B21D 22/02 20060101 B21D022/02 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 28, 2019 |
CN |
201911189038.7 |
Claims
1. A method for forming a large-size curved thin-walled metal skin,
comprising the following steps: step 1: extracting the position and
size characteristics of stiffeners on a curved panel according to
the assembly relationship between the curved panel and a
thin-walled skin; step 2: assuming that the thickness of the curved
panel and the thin-walled skin after assembly is m, determining the
size of a forming punch based on the shape and size of the curved
panel, and offsetting a forming surface of the punch outwards along
a normal line by the thickness m based on the size of the forming
surface to obtain the characteristics of the inner surface of a
female die; step 3: determining the size of discrete support moulds
to be the same as that of the curved panel according to the
thickness of the curved panel, and determining forming surfaces of
the discrete support moulds based on the inner surface of the
forming thin-walled skin; step 4: setting the number of the
discrete support moulds to be the same as the number n of the
stiffeners based on the size and distribution of the stiffeners on
the curved panel, and the positions of the discrete support moulds
on the punch are consistent with the positions of the stiffeners on
the curved panel; step 5: processing and manufacturing the punch,
the female die and n discrete support moulds according to step 2
and step 3; step 6: fixing the n discrete support moulds on the
punch according to step 4, and the relevant positions for
connecting the discrete support moulds are corresponding to the
positions of the stiffeners on the curved panel during assembly;
and step 7: using the punch and the female die combined with the
discrete support moulds to carry out stamping of a curved
thin-walled slab to obtain a required thin-walled skin component.
Description
TECHNICAL FIELD
[0001] The present invention relates to a method for forming a
metal skin, in particular to a method for forming a large-size
curved thin-walled skin.
BACKGROUND
[0002] In the fields of aerospace and weapon equipment, achieving a
lightweight structure is one of the main goals pursued. In order to
reduce the weight of the structure, it is necessary to optimize the
design of components on the premise of meeting the requirements of
use. For example, many lightweight hollow composite structures are
used on a rocket or a missile, such as panels of a rocket
propellant tank and fairings of a missile. This kind of lightweight
structure usually consists of a curved panel and a thin-walled skin
matched therewith. The curved panel is generally composed of
thin-walled webs and stiffeners connected thereto, and the
stiffeners are used to improve the overall stiffness of the panel.
In order to further improve the stiffness of the curved panel and
realize the continuity of the surface on the side with the
stiffeners, it is necessary to provide the thin-walled skin matched
therewith outside the discretely distributed stiffeners.
[0003] The above-mentioned lightweight hollow composite structures
usually have relatively large sizes, and the lengthwise sizes can
reach several meters or even dozens of meters. In order to further
reduce weight, lightweight and high-strength aluminum alloy
materials, such as 2024 and 2219, are mostly used as materials for
the curved panel and the thin-walled skin, wherein the curved panel
is usually made of a thick aluminum alloy plate with a wall
thickness of 20-50 mm, and the thin-walled skin is usually made of
a thin aluminum alloy plate with a wall thickness of 2-5 mm. As the
thickness of the thick aluminum alloy plate used to manufacture the
panel is very different from that of the thin aluminum alloy plate
used to manufacture the skin, different forming methods and
separate mould tooling are required.
[0004] At present, the forming methods of the curved panel include
press bending, cold roll, stamping, etc. For a single-curvature
cylindrical or conical panel, forming can be realized by the method
of press bending or cold roll. However, for a curved panel with a
small bending radius or a high dimensional accuracy requirement,
dimensional accuracy requirement cannot be met often by press
bending or cold roll. In this case, stamping need to be carried out
by a rigidity punch and a rigidity female die. The rigidity punch
and the rigidity female die need to be specially designed and
manufactured according to the shape and size of a specific panel
component.
[0005] For a thin-walled skin, forming is often realized by the
methods such as stretching and stamping. During the stretch-forming
of a large-size thin-walled skin, the edge of a rectangular metal
blank need to be clamped with jaws, and then the middle area of the
metal blank is deformed under the action of a stretching die to
obtain a required profile shape. After the stretch-forming, only
part of the middle area of the metal blank is fitted with the
stretching die, and other surrounding material will be removed as a
process remnant Therefore, the method of stretching is difficult to
be used for forming a thin-walled skin with an obvious curved
surface and especially with a double curvature. In this case, it is
necessary to use mutually matched rigidity punch and rigidity
female die to obtain a required thin-walled skin through
stamping.
[0006] Since punches, female dies and corresponding tooling in
one-to-one correspondence with parts to be formed are generally
required to be processed for stamping, the cost of moulds and
tooling is relatively high, and this is especially true for
large-sized components. For example, for a curved panel and a
thin-walled skin with a length of about 3 m and a width of 1 m, the
cost of moulds and tooling used for stamping can reach hundreds of
thousands yuan or even millions yuan. At the same time, large-scale
special equipment is required for the manufacturing of large-size
moulds and tooling, and it will take several weeks or an even
longer time to complete the manufacturing. Therefore, it is very
important to reduce the cost of moulds and tooling while ensuring
the smooth forming of components and obtaining a high forming
accuracy when the method of stamping must be used.
[0007] In order to solve the problems of high component
manufacturing cost, long production cycle, high requirements for
mould and tooling manufacturing equipment, and high requirements
for the use of the equipment due to the need of separately
manufacturing large-sized moulds and tooling when the existing
method of stamping is used to manufacture a large-size curved panel
and a thin-walled skin, it is necessary to develop a new method for
forming a large-size curved thin-walled skin.
SUMMARY
[0008] In order to solve the problems of high component
manufacturing cost, long production cycle, high requirements for
mould and tooling manufacturing equipment, and high requirements
for the use of the equipment due to the need of separately
manufacturing large-sized moulds and tooling when the existing
method of stamping is used to manufacture a large-size curved panel
and a thin-walled skin, the present invention proposes a method for
forming a large-size curved thin-walled metal skin.
[0009] The technical solution of the present invention is:
[0010] A method for forming a large-size curved thin-walled metal
skin, comprising the following steps:
[0011] Step 1: extracting the position and size characteristics of
stiffeners on a curved panel according to the assembly relationship
between the curved panel and a thin-walled skin;
[0012] Step 2: assuming that the thickness of the curved panel and
the thin-walled skin after assembly is m, determining the size of a
forming punch based on the shape and size of the curved panel, and
offsetting a forming surface of the punch outwards along a normal
line by the thickness m based on the size of the forming surface to
obtain the characteristics of the inner surface of a female
die;
[0013] Step 3: determining the size of discrete support moulds to
be the same as that of the curved panel according to the thickness
of the curved panel, and determining forming surfaces of the
discrete support moulds based on the inner surface of the forming
thin-walled skin;
[0014] Step 4: setting the number of the discrete support moulds to
be the same as the number n of the stiffeners based on the size and
distribution of the stiffeners on the curved panel, and the
positions of the discrete support moulds on the punch are
consistent with the positions of the stiffeners on the curved
panel;
[0015] Step 5: processing and manufacturing the punch, the female
die and n discrete support moulds according to step 2 and step
3;
[0016] Step 6: fixing the n discrete support moulds on the punch
according to step 4, and the relevant positions for connecting the
discrete support moulds are corresponding to the positions of the
stiffeners on the curved panel during assembly; and
[0017] Step 7: using the punch and the female die combined with the
discrete support moulds to carry out stamping of a curved
thin-walled slab to obtain a required thin-walled skin
component.
[0018] The present invention has the following beneficial
effects:
[0019] (1) In the method for forming a large-size curved
thin-walled metal skin of the present invention, the n discrete
support moulds used are combined with the curved panel forming
punch, then the stamping of the thin-walled skin is carried out,
and the positions of the discrete support moulds are consistent
with the positions of the stiffeners on the curved panel, so that
it can be ensured that the part of the thin-walled skin
corresponding to the stiffeners obtains sufficiently high shape and
dimensional accuracy, thereby realizing the subsequent reliable
connection of the thin-walled skin and the panel.
[0020] (2) In the method for forming a large-size curved
thin-walled metal skin of the present invention, the n discrete
support moulds used are only in partial contact with the
thin-walled slab, so that the areas on the thin-walled skin that do
not need to be assembled with the stiffeners are in a relatively
free state during stamping, which can avoid unreasonable,
uncontrollable or redundant deformation in such areas when a solid
punch is used for stamping.
[0021] (3) In the method for forming a large-size curved
thin-walled metal skin of the present invention, the connecting
positions of the discrete support moulds used on the punch can be
easily adjusted, so that the problems such as wrinkling and warping
which may occur during a forming process can be easily
eliminated.
[0022] (4) In the method for forming a large-size curved
thin-walled metal skin of the present invention, the discrete
support moulds used can be assembled and connected with the punch,
so that the discrete support moulds are easy to replace, and can be
replaced by different discrete support moulds to be used for
forming thin-walled skins of different thicknesses.
[0023] (5) In the method for forming a large-size curved
thin-walled metal skin of the present invention, the discrete
support moulds used only need to be in contact with the thin-walled
slab in partial areas, so that the shape thereof is simple, the
manufacturing cycle is short, and the manufacturing cost is greatly
reduced.
DESCRIPTION OF DRAWINGS
[0024] FIG. 1(a) is a schematic diagram of a curved panel.
[0025] FIG. 1(b) is a schematic diagram of a thin-walled skin.
[0026] FIG. 2 is a schematic diagram of stamping of a curved
panel.
[0027] FIG. 3 is a schematic diagram of forming a large-size curved
thin-walled skin by a discrete support mould;
[0028] FIG. 4 is a schematic diagram of assembly of a discrete
support mould and a curved panel forming punch;
[0029] FIG. 5 is a schematic diagram of action of a discrete
support mould on a thin-walled skin.
[0030] In the figures: 1 curved panel; 2 thin-walled skin; 3 punch;
4 female die; 5 connecting bolt; 6 discrete support mould.
DETAILED DESCRIPTION
[0031] The technical solution of the present invention is further
described below in combination with the drawings and specific
embodiments.
Embodiment 1
[0032] Referring to FIG. 3 for description, a method for forming a
large-size curved thin-walled metal skin, comprising the following
steps:
[0033] Step 1: extracting the position and size characteristics of
stiffeners on a curved panel according to the assembly relationship
between the curved panel and a thin-walled skin;
[0034] Step 2: assuming that the thickness of the curved panel and
the thin-walled skin after assembly is m, determining the size of a
forming punch based on the shape and size of the curved panel, and
offsetting a forming surface of the punch outwards along a normal
line by the thickness m based on the size of the forming surface to
obtain the characteristics of the inner surface of a female
die;
[0035] Step 3: determining the size of discrete support moulds to
be the same as that of the curved panel according to the thickness
of the curved panel, and determining forming surfaces of the
discrete support moulds based on the inner surface of the forming
thin-walled skin;
[0036] Step 4: setting the number of the discrete support moulds to
be the same as the number n of the stiffeners based on the size and
distribution of the stiffeners on the curved panel, and the
positions of the discrete support moulds on the punch are
consistent with the positions of the stiffeners on the curved
panel;
[0037] Step 5: processing and manufacturing the punch, the female
die and n discrete support moulds according to step 2 and step
3;
[0038] Step 6: fixing the n discrete support moulds on the punch
according to step 4, and the relevant positions for connecting the
discrete support moulds are corresponding to the positions of the
stiffeners on the curved panel during assembly; and
[0039] Step 7: using the punch and the female die combined with the
discrete support moulds to carry out stamping of a curved
thin-walled slab to obtain a required thin-walled skin
component.
[0040] The n discrete support moulds used are combined with the
curved panel forming punch, then the stamping of the thin-walled
skin is carried out, and the positions of the discrete support
moulds are consistent with the positions of the stiffeners on the
curved panel, so that it can be ensured that the part of the
thin-walled skin corresponding to the stiffeners obtains
sufficiently high shape and dimensional accuracy, thereby realizing
the subsequent reliable connection of the thin-walled skin and the
curved panel.
Embodiment 2
[0041] Referring to FIG. 4 for description, a method for forming a
large-size curved thin-walled metal skin, comprising the following
steps:
[0042] In step 6, the n discrete support moulds are dispersedly
arranged on the punch, the dispersing positions of discrete support
moulds can be determined according to the positions of the
stiffeners on the curved panel, the replacement stiffeners of the
discrete support moulds are distributed on the punch, and the
dispersing positions of the discrete support moulds can also be
adjusted according to the forming condition of the thin-walled slab
after forming. Other steps are the same as those in embodiment
1.
[0043] When a sheet is formed by a solid die, due to the uneven
load distribution and different contact states on various parts of
a slab, the problems of wrinkling and warping are prone to occur
during forming; whereas a certain distance exists among the
discrete support moulds, so that the problems such as wrinkling and
warping which may occur during a forming process can be easily
eliminated by adjusting the positions of the discrete support
moulds on the punch. The discrete support moulds are assembled and
connected with the punch, so that the discrete support moulds are
easy to replace, and can be replaced by different discrete support
moulds to be used for forming thin-walled skins of different
thicknesses, which saves the material and processing cost of the
moulds.
Embodiment 3
[0044] Referring to FIG. 5 for description, a method for forming a
large-size curved thin-walled metal skin, comprising the following
steps:
[0045] In step 6, the discrete support moulds and the punch can be
effectively connected by bolts, and each discrete support mould is
composed of a plurality of small moulds with surface shape and size
requirements. Each discrete support mould used in other steps is
composed of a plurality of small mould blocks, and a gap exists
among adjacent small mould blocks. Other steps are the same as
those in embodiment 1.
[0046] In a traditional stamping process, most of the moulds are in
a solid form, which are prone to have excessive local contact
stress and redundant deformation. The discrete support moulds
composed of a plurality of small mould blocks are only in partial
contact with the thin-walled slab, so that the areas on the
thin-walled skin that do not need to be assembled with the
stiffeners are all in a relatively free state, which can avoid
unreasonable, uncontrollable or redundant deformation in such areas
when a solid punch is used for forming.
* * * * *