Friction stir welding process having enhanced corrosion performance

Abstract

A three dimensional joint is formed by coupling (joining) a first structural member and a second structural member. This involves first aligning a first structural member to a second structural member. The first structural member has a channel with which to receive a portion of the second structural member. Certain embodiments may place corrosively inert materials within the mating surfaces to prevent or inhibit corrosion or oxidation. Once aligned, the first structural member and second structural member may be friction stir welded at the channel to plasticize the material adjacent to the channel of both the first structural member and the second structural member to form a friction stir weld joint. Embodiments may then coat the plasticized surfaces of the FSW joint with cold sprayed materials to inhibit corrosion. Should a crack occur within either the plasticized or non-plasticized materials, cold sprayed material may be deposited within and on the crack to retard or arrest the growth of the crack.

Description

TECHNICAL FIELD OF THE INVENTION[0001]The present invention relates generally to structural joints and more particularly a method to join two or more members in forming a three-dimensional joint.BACKGROUND OF THE INVENTION[0002]Structural beams translate stiffness and other mechanical loads within structures such as buildings, vehicles, and bridges, etc. In one example, structural beams may be used to translate loads associated with the wing of an aircraft. These structural beams may include box beams, I-beams, double I-beams, C-Beams or other like structures that are efficient load carrying members. FIGS. 1A and 1B provide a cross section of a typical I-Beam and C-Beam. Such beams may be used in a variety of applications. I-Beams may be used for long clear spans requiring heavy loads. While C-Beams can be used where design and load requirements allow use of a C-Beam as opposed to an I-Beam, which provides additional support. Additionally a C-Beam may provide one flush surface not p...

AI Technical Summary

Benefits of technology

[0009]The present invention provides a means of joining a first structural member and a second structural member that substantially addresses the above identified needs as well as others. Embodiments of the present invention provide a joint formed by coupling (joining) a first structural member and a second structural member. This involves first aligning a first structural member to a second structural member. The first structural member has a channel with which to receive a portion of the second structural member. Certain embodiments may place corrosively inert materials within the mating surfaces to prevent or inhibit corrosion or oxidation. Once aligned, the first structural member and second structural member may be friction stir welded at the channel to plasticize the material adjacent to the channel of both the first structural member and the second structural member to form a friction stir weld joint. Embodiments may then coat the plasticized surfaces of the FSW joint with cold sprayed materials to inhibit corrosion. Should a crack occur within either the plasticized or non-plasticized materials, cold sprayed material may be deposited within and on the crack to retard or arrest the growth of the crack.

[0010]Another embodiment in the present invention provides a method for joining structural members. This involves aligning the first structural member to a second structural member. The first structural member has a channel with which to receive a portion of the second structural member. As in the prior embodiment, this channel serves as a guide with which to position the first structural member relative to the second structural member. For example, the first and second structural member may be an I-beam or C-beam wherein the channel is placed within the horizontal members and not the vertical webs of the I-beam. Certain embodiments may place corrosively inert materials within the mating surfaces to prevent or inhibit corrosion or oxidation. Once fitted together FSW takes place at the channel to join the first structural member to the second structural member. This results in plasticizing and mixing the materials within and adjacent to the channel of both the first and the second structural member to form a single continuous joint at the channel. Cold sprayed materials may then coat the plasticized surfaces of the FSW joint to inhibit corrosion. Should a crack occur within either the plasticized or non-plasticized materials, cold sprayed material may be deposited within and on the crack to retard or arrest the growth of the crack.

[0011]Additional embodiments may place an adhesive or barrier material that may both assist in fitting the first structural member to the second structural member prior to the friction stir weld as well as providing a barrier as the adhesive or barrier material is extruded into interface cavities at the friction stir weld joint. This method is particularly useful for structures where weight is a concern, such as an aircraft using aluminum or aluminum alloy structural members. By eliminating the need reinforce structural components due to the coupling of structural members using traditional fastener methods, the weight associated with these structural; members may be greatly reduced.

[0012]Another embodiment of the present invention provides a similar method for joining structural members. Again the first structural member is aligned and fitted to a second structural member wherein a channel within the first structural member receives a portion of the second structural member. In addition to this channel which may be used to fit the first structural member to the second structural member a male connector within either the first structural member and / or second structural member may be received within a female receptacle of the second structural member and / or first structural member. This may further facilitate the setup and alignment process. Certain embodiments may place corrosively inert materials on the mating surfaces to prevent or inhibit corrosion or oxidation. The materials of the male connector and female receptacle may be friction stir welded at the interface to further enhance the joint coupling the first structural member to the second structural member. Additionally, adhesive, barrier, and / or corrosively inert material may be placed at the channel, male connector, and / or female receptacle to assist in fitting, preventing contaminants from entering or penetrating the interface cavities that remain after joining the structural members, and / or inhibit corrosion.

Problems solved by technology

Structures constructed via bolted and fastened I-beams and C-beams often have problems translating stiffness and loads with minimal weight due to moment continuity.

Such holes often produce localized stresses and mechanical loads that the beams must account for.

Additionally, set up, tooling and the time required to drill holes may become major drivers in manufacturing as well as issues in quality assurance.

The installation of fasteners is also a process prone to quality assurance issues.

However, smaller complex three dimensional structures, such as aircraft designs, have not been easily addressed by the application of FSW.

Joining and properly plasticizing three-dimensional surfaces is difficult.

Thus it has been difficult to apply FSW processing to complex three-dimensional structures.

There are problems associated with each of these joining methods.

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