Asymmetrical, one-piece, hollow metal structure such as a traili

Details Asymmetrical, one-piece, hollow metal structure such as a traili Asymmetrical, one-piece, hollow metal structure such as a traili

1997-07-01

1999-11-02

Poon, Peter M.

Aeronautics and astronautics

Aircraft structure

Airfoil construction

244119, B64C 320

Patent

active

059754656

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

1. Technical Field
The invention mainly relates to a hollow metal structure having outer skins with substantially different curvatures, joined along an edge, as well as inner reinforcements defining cavities between the outer skins.
Such a structure, whose originality is based both on its asymmetry and its one-piece nature, can be advantageously used for forming at least one section of the trailing edge of an aircraft wing leading edge slat.
The invention also relates to a process for manufacturing such an asymmetrical structure by diffusion welding and superplastic forming.
2. Prior Art
On existing aircraft, the trailing edges of wing leading edge slats are manufactured by assembling several parts by bonding and riveting. These parts generally comprise two outer skins for forming the upper surface and inner surface of the trailing edge, an extruded terminal part forming the actual trailing edge, a spar with a U-shaped cross-section for providing the connection between the two outer skins opposite to the trailing edge and a honeycomb filling structure filling the space formed between the aforementioned parts. The outer skins and the terminal part are made from an aluminium alloy. The spar with the U-shaped cross-section is made from a carbon-based composite material. Finally, the honeycomb filling material is generally aluminium.
This description shows that the methods used at present for producing the trailing edges of aircraft leading edge slats are particularly complex and difficult to implement.
Moreover, the superplastic properties of metals such as titanium-based alloys make it possible to manufacture in such materials hollow, one-piece structures by successively carrying out diffusion welding between stacked sheets, followed by a superplastic forming of said sheets.
As is e.g. illustrated by U.S. Pat. No. 5,344,063, this process is generally performed in several stages requiring different tools and it is particularly appropriate for the manufacture of parts having a symmetry with respect to a plane.
As is illustrated by U.S. Pat. No. 4,833,768, it is also known to manufacture by this process asymmetrical structures, whereof the two outer skins are inwardly curved, whilst remaining substantially parallel to one another. In particular, the inwardly curved structure whose manufacture is described in this document has inner reinforcements, whose I-shaped cross-section is perpendicular to the outer skins. In order that there are no excessive displacements in the elongation or extension of the different sheets during superplastic forming, the stack of sheets is progressively inwardly curved during the closing of the forming tools, in order to assume a mean curvature close to the curvature of the structure which it is wished to produce.
In U.S. Pat. No. 4,833,768, to enable the superplastic forming to be carried out under satisfactory conditions, i.e. without any risk of an uncontrolled folding of the sheets, the latter must be tensioned during the closing of the tools, which makes it necessary to add thereto abutments which bear against the tools just prior to complete closure. This procedure suffers from the disadvantage of imposing a welding of the sheets, particularly in areas intended to form inner reinforcements, prior to the putting into place of the stack of sheets in the tooling.
Comparable disadvantages are encountered in U.S. Pat. No. 5,330,092, which proposes manufacturing an asymmetrical, one-piece, hollow metal wing from a stack of sheets by preceding a structure superplastic forming operation in adapted tooling by an operation of welding the different sheets together performed with the aid of a laser, prior to the placing of the structure in the forming tooling.
As is disclosed by U.S. Pat. No. 5,323,536, it is also known to manufacture an asymmetrical, one-piece, hollow metal structure, such as a fan blade from a stack of sheets, by making welds between the sheets by diffusion welding, followed by shaping by superplastic forming. However, the asymmetrical nature of the structur

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patent: 5534354 (1996-07-01), Gregg et al.
patent: 5544847 (1996-08-01), Bliesner

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