Friction stir welding process having enhanced corrosion performance
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.
Latest Patents:
- PHARMACEUTICAL COMPOSITIONS OF AMORPHOUS SOLID DISPERSIONS AND METHODS OF PREPARATION THEREOF
- AEROPONICS CONTAINER AND AEROPONICS SYSTEM
- DISPLAY SUBSTRATE AND DISPLAY DEVICE
- DISPLAY APPARATUS, DISPLAY MODULE, ELECTRONIC DEVICE, AND METHOD OF MANUFACTURING DISPLAY APPARATUS
- DISPLAY PANEL, MANUFACTURING METHOD, AND MOBILE TERMINAL
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 INVENTIONStructural 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.
These beams are typically joined together using fasteners. 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. This joining method also requires drilling holes and installing fasteners to attach the members to one another. Such holes often produce localized stresses and mechanical loads that the beams must account for. To account for such localized loads, the structure of the beam may be reinforced resulting in increased weight and loads to be handled by the beams.
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. (i.e. insuring that the proper fasteners are used with the proper torques)
Friction Stir Welding (FSW) is a joining method, as illustrated in
There are cost advantages if one applies a simple stiffened skin structure that may be produced via FSW to the exterior of a vehicle such as an aircraft. The robustness and automation of the process is very attractive for manufacturing. However, smaller complex three dimensional structures, such as aircraft designs, have not been easily addressed by the application of FSW. The FSW process works best when two pieces abut one another and are clamped tightly together. This is most effectively achieved when the two pieces are forming a single two-dimensional surface. 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. The requirement to drill holes and install fasteners to attach beams to one another requires that the fastened beams be strengthened in order to account for the localized mechanical loads caused by the fasteners. Additionally, mechanical loads within the beams may be localized at the fastener site as opposed to being transferred across the entire joint interface.
Further limitations and disadvantages of conventional and traditional joining process and related structures and functionality will become apparent to one of ordinary skill in the art through comparison with the present invention described herein.
SUMMARY OF THE INVENTIONThe 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.
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.
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.
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.
For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings in which like reference numerals indicate like features and wherein:
Embodiments of the present invention are illustrated in the FIGS., like numerals being used to refer to like and corresponding parts of the various drawings.
The present invention provides a means of joining a first structural member and a second structural member that substantially addresses the above identified needs. 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. One method of performing friction stir welding to join members is disclosed in U.S. patent application Ser. No. ______ entitled “A FRICTION STIR WELDING PROCESS TO JOIN TWO OR MORE MEMBERS IN FORMING A THREE-DIMENSIONAL JOINT,” which is incorporated by reference in its entirety for all purposes.
Embodiments of the present invention may provide a cold spray process where a powder, such as a powered metal, is directly and selectively applied to the exposed surface(s) of the FSW to act as sacrificial layer to protect the FSW joint depicted in the FIGS. Additionally, the impact of the powder during the cold spray process may create a small residual compressive stress which may add superior mechanical properties when compared to conventionally welded and aged joints. The cold spray process depicted in
Through cold spray processes, embodiments of the present invention can apply corrosion coatings to any configuration of a FSW joint to effectively protect exposed surfaces of the FSW joint. For structural members made using 7000 aluminum alloys, this may reduce or eliminate the need for a thermal treatment after FSW. This thermal treatment improves the corrosion resistance of 7000 aluminum alloys, but this sacrifices strength within the 7000 aluminum alloys. Applying cold spray materials to the FSW joint allows the 7000 aluminum alloys to retain their strength while protecting the weld area through the application of a coating via cold spray. Embodiments of the present invention may also provide the ability to apply a layer of a coatings (i.e. Commercially Pure Aluminum (CP AL)) to a lapping FSW joint prior to FSW. This will have the result of providing a faying surface that has been effectively clad. Mixing the CP Al into the joint will not affect the strength adversely because of the small addition to the weld.
The cold spraying process may also be used to form in situ fasteners to metallic materials such as aluminum through composite. One such method is disclosed in U.S. patent application Ser. No. 11/279,970 entitled “PERFORATED COMPOSITES FOR JOINING OF METALLIC AND COMPOSITE MATERIALS,” which is incorporated by reference in its entirety for all purposes. The joint need not be that dissimilar, nor aluminum. Through cold spray processes, embodiments of the present invention can deposit powdered metal directly to the surface of a metal through a hole drilled into the mating member. This will improve the fatigue resistance of the member which has not be through drilled (i.e. the metal). Additionally, a friction stir spot weld of this compacted powder may be performed to further consolidate the cold spray material and providing better “adhesion” to the substrate. Both of these methods may be applied to a drilled hole or channel.
An alternative way to form an in situ fastener provided by embodiments of the present invention employs friction stir welding. By placing a metallic panel (i.e. Al) on top of a panel with a machined recess such as a hole or channel (could be composite) and using FSW on the surface of the metal, the resulting void will be filled by extruded metal. This has been demonstrated in an Aluminum to composite panel. The main advantage is that the composite can be processed separate and does not require laying up the composite on the metal like COMELD. This process will be further discussed with reference to
To further improve the friction stir weld joint of member 50 and 52, an adhesive may be deposited within the channel in order to assist in the fitting. This adhesive may also form a barrier to prevent moisture or other contaminants from penetrating the friction stir weld joint or any spaces (interface cavities) or gaps left following the joining process.
Unlike prior applications of FSW where two pieces were abutted against each other and friction stir welded to form a single continuous panel. Embodiments of the present invention allow the creation of a three dimensional structure. Additionally, the application of FSW limits any deformation of the vertical portions of the members to be joined. Thus preserving the load bearing capability of the beams.
In the embodiment presented previously, one can deposit the adhesive or barrier material in the channel 54 of
These FSW joints may be subject to crevice corrosion of the joint surfaces. One embodiment of the present invention addresses this issue with the addition of a corrosively inert layer applied prior to the FSW process. As shown in
This will allow in one embodiment, aluminum powder to form a sacrificial layer on the surface of the FSW joint that corrodes or oxidizes preferentially. This sacrificial layer extends the life of the FSW joint. Additionally, the small residual compressive stresses may be imparted to the surface of the FSW joint. These compressive stresses may improve the static and dynamic properties. This process provides a significant advantage in that cold spray is a relatively inexpensive process that allows precise deposition of sacrificial material where required. Additionally almost any material can be converted into a powder that can be deposited using cold spray. When compared to other techniques used to improve the corrosion performance application of the material over the entire part is required and does not provide a selective deposition process.
In another embodiment of the present invention as illustrated in
Additional steps may require the placing of an adhesive or barrier material within the channel, upon the male connectors, or within the female receptacles. This adhesive or barrier material fills interface cavities to prevent contaminants from entering.
This invention solves prior problems by using the existing structural members, such as I-beams C-beams, that incorporate alignment guides (i.e. channels, connectors, and/or receptacles) to fit and FSW these materials to form three dimensional shapes such as T-joint configurations. By incorporating a groove or channel into the horizontal pieces and inserting the vertical pieces into these alignment guides, both members are joined together without disturbing the radius of the upstanding channel or groove. This joint can be further enhanced through the application of an adhesive or barrier material near the top of the alignment guide which will allow load transfer of material not joined by the FSW. The adhesive or barrier material acts to deny penetration into the joint by moisture or other contaminants. This adhesive facilitates fitting the parts (i.e. structural members), during setup.
The T grooved or channel T FSW joint provided by embodiments of the present invention has many advantages. First the drilling of holes and fastener installation is eliminated for assembly of structure members. In so doing, the fatigue lives of the structural members are extended through the elimination of localized stresses concentrated by these holes. Stiffness can be distributed over the entire cross section versus 2 or 3 bolts/fasteners interfaces enabling lower overall weight of the structural members and structure. Set up time is reduced by using the adhesive to locate the mating parts. This reduces or eliminates complex tooling requirements. Pull off strength and fatigue life in the finished structure may be improved by the addition of adhesives. The adhesive also fills the interface cavities disallowing water or contaminant entrapment. In so doing crevice corrosion is inhibited. Cold spray and adhesives improve the stiffness and rigidity of the finished assembly by improving the stiffener effectiveness. Nascent adhesive from the weld joint also provides a visual indicator that adhesive materiel is present in the weld joint, thus simplifying NDE verification.
In summary, embodiments of the present invention provide a three dimensional 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. 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 FSW joint. One embodiment then coats the plasticized surfaces of the FSW joint with cold sprayed materials to inhibit corrosion. Another embodiment places corrosively inert materials within the mating surfaces to prevent or inhibit corrosion or oxidation. 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.
Although the present invention is described in detail, it should be understood that various changes, substitutions and alterations can be made hereto without departing from the spirit and scope of the invention as described by the appended claims.
Claims
1. A method for joining structure members, comprising:
- aligning a first structural member to a second structural member, the first structural member having a channel to receive a portion of the second structural member;
- friction stir welding (FSW) at the channel to join the first structural member to the second structural member;
- cold spraying material on exposed surfaces of an FSW joint to inhibit corrosion.
2. The method of claim 1, further comprising placing a corrosively inert material at the channel to inhibit crevice crack corrosion.
3. The method of claim 2, further comprising preventing moisture penetration into a FSW joint formed by the first structural member and the second structural with the corrosively inert material.
4. The method of claim 1, further comprising placing an adhesive material at the channel, the adhesive material operable to fit the first structural member to the second structural member prior to FSW.
5. The method of claim 1, wherein the first structural member and the second structural member are within a vehicle frame.
6. The method of claim 1, wherein the first structural member and the second structural member comprise:
- a box beam;
- an I-beams;
- a double I-beam; or
- a C-Beam.
7. The method of claim 1, wherein the first structural member and the second structural member comprise an aluminum alloy.
8. The method of claim 1, further comprising:
- inserting a male connector of the first structural member and/or second structural member into a female receptacle of the second structural member and/or first structural member; and
- friction stir welding materials of the male connector into the female receptacle to create a FSW coupling.
9. A method for joining structural members, comprising:
- aligning a first structural member to a second structural member, the first structural member having a channel to receive a portion of the second structural member;
- inserting a male connector of the first structural member and/or second structural member into a female receptacle of the second structural member and/or first structural member;
- friction stir welding (FSW) at the channel and a male connector/female receptacle interface to join the first structural member to the second structural member; and
- cold spraying material on exposed surfaces of an FSW joint to inhibit corrosion.
10. The method of claim 9, further comprising placing a corrosively inert material at the channel to inhibit crevice crack corrosion
11. The method of claim 10, further comprising preventing penetration of contaminates into a friction stir weld joint formed by the first structural member and the second structural, the penetration prevented with the corrosively inert material.
12. The method of claim 9, wherein the first structural member and the second structural member are within a vehicle frame.
13. The method of claim 9, wherein the first structural member and the second structural member comprise:
- a box beam;
- an I-beams;
- a double I-beam; or
- a C-Beam.
14. The method of claim 9, wherein the first structural member and the second structural member comprise an aluminum alloy.
15. A friction stir weld joint, comprising:
- a first structural member, the first structural member having a channel;
- at least one second structural member, the channel of the first structural member receives a portion of the at least one second structural member, the materials of the first structural member and at least one second structural member friction stir welded at the interface of the first structural member and at least one second structural member at the channel; and
- cold sprayed material deposited on an exposed surface of the friction stir welded interface operable to inhibit corrosion.
16. The friction stir weld joint of claim 15, wherein the channel is within a horizontal member of the first structural member, the channel receives a vertical member of the second structural member.
17. The friction stir weld joint of claim 15, wherein a barrier material within the channel fills interface cavities at the friction stir weld joint to prevent contamination from entering the friction stir weld joint.
18. The friction stir weld joint of claim 16, wherein the barrier material comprises corrosively inert material.
19. The friction stir weld joint of claim 15, further comprising:
- a male connector of the first structural member and/or second structural member;
- a female receptacle of the second structural member and/or first structural member operable to receive the male connector,
- the materials of the male connector friction stir welded into the female receptacle.
20. The friction stir weld joint of claim 15, wherein an adhesive material at the channel, the male connector, and or the female receptacle, the adhesive material operable to fit the first structural member to the second structural member prior to friction stir welding.
21. The friction stir weld joint of claim 15, wherein the first structural member and the second structural member are within a vehicle frame.
22. The friction stir weld joint of claim 15, wherein the first structural member and the second structural member comprise:
- a box beam;
- an I-beams;
- a double I-beam; or
- a C-Beam.
23. The friction stir weld joint of claim 15, wherein the first structural member and the second structural member comprise an aluminum alloy.
24. A friction stir weld joint, comprising:
- a first structural member, the first structural member having a channel;
- at least one second structural member, the channel of the first structural member receives a mating surface of the at least one second structural member, the mating surface and/or channel being coated with corrosively inert material, the materials of the first structural member and at least one second structural member friction stir welded at the interface of the first structural member and at least one second structural member at the channel; and
- cold sprayed material deposited on an exposed surface of the friction stir welded interface operable to inhibit corrosion.
25. A friction stir weld joint, comprising:
- a first structural member, the first structural member having a channel; and
- at least one second structural member, the channel of the first structural member receives a mating surface of the at least one second structural member, the mating surface and/or channel being coated with corrosively inert material, the materials of the first structural member and at least one second structural member friction stir welded at the interface of the first structural member and at least one second structural member at the channel.
26. A method for joining structure members, comprising:
- aligning a first structural member to a second structural member, the first structural member having a channel to receive a portion of the second structural member;
- placing a corrosively inert material at the channel to inhibit crevice crack corrosion; and
- friction stir welding (FSW) at the channel to join the first structural member to the second structural member.
27. A method for joining structural members, comprising:
- aligning a first structural member to a second structural member, the first structural member having a channel to receive a mating of the second structural member;
- inserting a male connector of the first structural member and/or second structural member into a female receptacle of the second structural member and/or first structural member;
- placing a corrosively inert material at the channel/mating surface to inhibit crevice crack corrosion;
- placing a corrosively inert material at a male connector/female receptacle interface to inhibit crevice crack corrosion;
- friction stir welding (FSW) at the channel and a male connector/female receptacle interface to join the first structural member to the second structural member.
28. A method for retarding crack growth within a structural member, comprising:
- identifying a crack within the structural member; and
- cold spraying material on/within the crack to retard crack growth.
29. A method for joining a first structural member and a substrate, comprising:
- aligning a first structural member to a metallic substrate, the first structural member having at least one shaped cavity; and
- friction stir welding an exterior surface of the metallic substrate proximate to the at least one shaped cavity to extrude metallic material to the at least one shaped cavity.
Type: Application
Filed: Aug 23, 2006
Publication Date: Feb 28, 2008
Applicant:
Inventor: John E. Barnes (Roswell, GA)
Application Number: 11/508,678