CN110883239A

CN110883239A - Forming method of large-size curved surface thin-wall metal skin

Info

Publication number: CN110883239A
Application number: CN201911189038.7A
Authority: CN
Inventors: 何祝斌; 刘建树; 凡晓波; 于江祥
Original assignee: Dalian University of Technology; Beijing Institute of Electronic System Engineering
Current assignee: Dalian University of Technology; Beijing Institute of Electronic System Engineering
Priority date: 2019-11-28
Filing date: 2019-11-28
Publication date: 2020-03-17
Anticipated expiration: 2039-11-28
Also published as: US20210162482A1; CN110883239B

Abstract

The invention provides a method for forming a large-size curved surface thin-wall metal skin, which is characterized in that the positions and size characteristics of reinforcing ribs on a curved surface wall plate are extracted according to the assembly relation between the curved surface wall plate and the thin-wall skin; assuming that the thickness of the assembled curved-surface wall plate and thin-wall skin is m, determining the size of a forming male die by taking the inner surface of the curved-surface wall plate as a reference, and offsetting the forming surface of the male die by the thickness of m along the outer side of a normal line to obtain the inner surface characteristic of the female die; the thickness dimension of the discrete support die is consistent with that of the curved wall plate, and the forming surface of the discrete support die is determined by taking the inner surface of the formed thin-wall skin as a reference; setting the number of discrete support dies to be consistent with the number n of the reinforcing ribs according to the size and distribution of the reinforcing ribs on the curved surface wall plate, wherein the positions of the discrete support dies on the male die are consistent with the positions of the reinforcing ribs on the curved surface wall plate; and (3) carrying out stamping forming on the curved surface thin-wall plate blank by utilizing the male die and the female die after the discrete supporting die is combined to obtain the required thin-wall skin member.

Description

Forming method of large-size curved surface thin-wall metal skin

Technical Field

The invention relates to a forming method of a metal skin, in particular to a forming method of a large-size curved surface thin-wall skin.

Background

In the fields of aerospace, weaponry, and the like, it is one of the most important goals to achieve a lightweight structure. In order to reduce the weight of the structure, the components need to be optimally designed on the premise of meeting the use requirements. For example, there are many lightweight hollow composite structures on rockets or missiles, such as rocket fuel tank panels, missile fairings, and the like. Such lightweight structures are typically formed of curved wall panels in combination with thin-walled skins associated therewith. Curved wall panels are generally made up of thin-walled webs and reinforcing ribs attached thereto to increase the overall stiffness of the panel. In order to further improve the rigidity of the curved wall plate and realize the continuity of the surface of one side with the reinforcing ribs, a thin-wall skin matched with the reinforcing ribs is required to be arranged on the outer sides of the reinforcing ribs which are distributed discretely.

The lightweight hollow composite structures described above typically have a relatively large dimension, which may be several meters or even tens of meters in the length direction. In order to further realize weight reduction, the materials of the curved wall plate and the thin-wall skin are mostly made of light-weight and high-strength aluminum alloy materials, such as 2024, 2219 and the like. The curved-surface wall plate is usually made of an aluminum alloy thick plate with the wall thickness of 20-50 mm, and the thin-wall skin is usually made of an aluminum alloy thin plate with the wall thickness of 2-5 mm. Due to the large difference in thickness between the aluminum alloy thick plate used to manufacture the panel and the aluminum alloy thin plate used to manufacture the skin, different forming methods and separate die tools are required.

At present, the curved wall plate is formed by press bending, roll bending or punching. For the cylindrical or conical wall plate with single curvature, the forming can be realized by adopting a press bending method or a roll bending method. However, for curved wall panels with smaller bending radius or higher requirements on dimensional accuracy, the requirements on dimensional accuracy often cannot be met by bending or roll bending, and at the moment, a rigid male die and a rigid female die are needed for stamping. The rigid male die and the rigid female die are specially designed and manufactured according to the shape and the size of a specific wallboard component.

For the thin-wall skin, the forming is mostly performed by methods such as drawing and stamping. When the large-size thin-wall skin is subjected to stretch forming, a jaw is adopted to clamp the edge of a rectangular metal blank, and then the middle area of the metal blank is deformed under the action of a stretch forming die to obtain the required profile shape. Because only the area of the middle part of the metal blank after the drawing forming is attached to the die, other surrounding materials are cut off as process excess materials. Therefore, the stretch-forming method is difficult to use for forming thin-walled skins having a pronounced curvature, particularly having a double curvature. At the moment, a rigid male die and a rigid female die which are matched with each other are needed to be adopted, and the needed thin-wall skin is obtained through stamping forming.

Because the stamping generally needs to process the male die, the female die and the corresponding tooling which correspond to the parts to be formed one by one, the cost of the die and the tooling is higher, and the stamping is particularly suitable for large-size components. For example, for curved wall panels and thin-walled skins having a length of about 3m and a width of 1m, the cost of the die and tooling used for stamping can reach tens of thousands of dollars or even millions of dollars. Meanwhile, large-scale special equipment is needed for manufacturing large-size moulds and tools, and the production can be completed in a plurality of weeks or even longer. How to reduce the cost of the die and the tooling while ensuring the smooth forming of the component and obtaining high forming precision by adopting a stamping forming method is very important.

In order to solve the problems that when the existing stamping method is used for manufacturing large-size curved surface wall plates and thin-wall skins, large-size dies and tools need to be manufactured respectively, so that the manufacturing cost of components is high, the production period is long, the requirements on die tool manufacturing equipment are high, the requirements on using equipment are high, and the like, a new forming method of the large-size curved surface thin-wall skins needs to be developed.

Disclosure of Invention

The invention provides a forming method of a large-size curved surface thin-wall metal skin, aiming at solving the problems that when the existing stamping method is used for manufacturing a large-size curved surface wallboard and a thin-wall skin, a large-size die and a large-size tool are required to be manufactured respectively, so that the manufacturing cost of a component is high, the production period is long, the requirements on the die tool manufacturing equipment are high, the requirements on the using equipment are high, and the like.

The technical scheme of the invention is as follows:

a method for forming a large-size curved surface thin-wall metal skin comprises the following steps:

the method comprises the following steps that firstly, the position and size characteristics of reinforcing ribs on a curved surface wall plate are extracted according to the assembly relation between the curved surface wall plate and a thin-wall skin;

step two, assuming that the thickness of the assembled curved wall plate and the thin-wall skin is m, determining the size of a forming male die by taking the shape and the size of the curved wall plate as a reference, and offsetting the thickness of m from the forming surface along the outer side of a normal line by taking the size of the forming surface of the male die as a reference to obtain the internal surface characteristic of a female die;

determining that the size of the discrete support die is consistent with that of the curved wall plate according to the thickness of the curved wall plate, and determining the forming surface of the discrete support die by taking the inner surface of the required forming thin-wall skin as a reference;

setting the number of the discrete support dies to be consistent with the number n of the reinforcing ribs according to the size and distribution of the reinforcing ribs on the curved surface wall plate, wherein the positions of the discrete support dies on the male die are consistent with the positions of the reinforcing ribs on the curved surface wall plate;

step five, machining and manufacturing a male die, a female die and n discrete supporting dies according to the step two and the step three;

step six, fixing the n discrete support dies on the male die according to the step four, wherein the corresponding positions of the connection of the discrete support dies correspond to the positions of the reinforcing ribs on the curved surface wall plate during assembly;

and seventhly, performing stamping forming on the curved surface thin-wall plate blank by using the male die and the female die after the discrete supporting die is combined to obtain the required thin-wall skin member.

The invention has the beneficial effects that:

(1) according to the forming method of the large-size curved surface thin-wall metal skin, n discrete support dies are combined with the convex die for forming the curved surface wall plate, then the thin-wall skin is stamped and formed, the positions of the discrete support dies correspond to the positions of the reinforcing ribs on the curved surface wall plate, the parts, corresponding to the reinforcing ribs, on the thin-wall skin can be guaranteed to obtain high enough shape and size precision, and therefore the subsequent reliable connection of the thin-wall skin and the wall plate is achieved.

(2) According to the forming method of the large-size curved surface thin-wall metal skin, the n discrete supporting molds are only in local contact with the thin-wall plate blank, the regions, which are not required to be assembled with the reinforcing ribs, on the thin-wall skin are in a relatively free state during stamping forming, and unreasonable, uncontrollable or redundant deformation of the regions during stamping forming by adopting an integral male mold can be avoided.

(3) According to the forming method of the large-size curved surface thin-wall metal skin, the connecting position of the discrete supporting die on the male die can be easily adjusted, so that the problems of wrinkling, warping and the like which can occur in the forming process can be easily eliminated.

(4) According to the forming method of the large-size curved surface thin-wall metal skin, the adopted discrete support die can be assembled and connected with the male die, so that the discrete support die is easy to replace, and the forming method can be used for forming the thin-wall skins with different thicknesses by replacing different discrete support dies.

(5) According to the forming method of the large-size curved surface thin-wall metal skin, the adopted discrete support die is only required to be in contact with the thin-wall plate blank in a local area, so that the forming method is simple in shape, short in manufacturing period and greatly reduced in manufacturing cost.

Drawings

FIG. 1(a) is a schematic view of a curved wall panel;

FIG. 1(b) is a schematic view of a thin-walled skin;

FIG. 2 is a schematic view of a curved wall panel press forming;

FIG. 3 is a schematic view of the formation of a large curved thin-walled skin using discrete support molds;

FIG. 4 is a schematic view of the assembly of the discrete support die with the curved panel forming punch;

FIG. 5 is a schematic diagram of the function of the discrete support mold and thin-walled skin.

In the figure: 1, curved surface wall plates; 2, thin-wall skin; 3, a male die; 4, curved surface wall plates; 5, a female die; 6-connecting bolt 7 male die; 8 discrete supporting moulds; 9 thin-wall skin; 10, forming a concave die.

Detailed Description

The technical scheme of the invention is further explained by the specific implementation mode in combination with the attached drawings.

Example 1:

referring to fig. 3, the method for forming the large-size curved thin-wall metal skin comprises the following specific steps:

and seventhly, performing stamping forming on the thin-wall plate blank by using the male die and the female die after the discrete supporting die is combined to obtain the required thin-wall skin member.

The n discrete supporting dies are combined with the convex die for forming the curved-surface wall plate, then the thin-wall skin is stamped, the positions of the discrete supporting dies correspond to the positions of the reinforcing ribs on the curved-surface wall plate, and the parts, corresponding to the reinforcing ribs, on the thin-wall skin can be guaranteed to obtain high enough shape and size precision, so that the subsequent reliable connection of the thin-wall skin and the curved-surface wall plate is realized.

Example 2:

referring to fig. 4, the method for forming the large-size curved thin-wall metal skin comprises the following specific steps:

in the sixth step, the n discrete supporting molds are dispersedly arranged on the male mold, the dispersing positions of the supporting molds can be determined according to the positions of the reinforcing ribs on the curved wall plate, the supporting molds replace the reinforcing ribs to be distributed on the male mold, and the dispersing positions of the supporting molds of the discrete supporting molds can be adjusted according to the forming condition of the thin-walled plate blank after forming, which is the same as that in the embodiment 1.

When the plate is formed by adopting the integral die, the problems of wrinkling and warping are easy to occur during forming due to uneven load distribution and different contact states at all positions on the plate blank, a certain distance exists between the discrete support dies, and the problems of wrinkling, warping and the like which may occur during forming can be easily eliminated by adjusting the positions of the discrete support dies on the male die. The discrete support die is assembled and connected with the male die, so that the discrete support die is easy to replace, and different discrete support dies can be replaced to form thin-wall skins with different thicknesses, so that the material and the processing cost of the die are saved.

Example 3:

referring to fig. 5, the method for forming the large-size curved thin-wall metal skin comprises the following specific steps:

in the sixth step, the discrete support die and the male die can be effectively connected by using bolts, and the discrete support die is formed by combining a plurality of small dies with surface shapes and size requirements. Each discrete supporting die adopted in other steps is formed by combining a plurality of small die blocks, and gaps exist between the adjacent small die blocks. Other steps are the same as those in the first embodiment.

In the traditional stamping forming process, most of dies adopt an integral form, local contact stress is easy to generate, and redundant deformation is generated. The discrete supporting die combined by the small die blocks is only partially contacted with the thin-wall plate blank, and the regions of the thin-wall skin, which do not need to be assembled with the reinforcing ribs, are in a relatively free state, so that unreasonable, uncontrollable or redundant deformation of the regions can be avoided when the integral male die is used for forming.

Claims

1. A forming method of a large-size curved surface thin-wall metal skin is characterized by comprising the following steps: