Metal fusion bonding – Process – Using dynamic frictional energy
Reexamination Certificate
2000-04-04
2001-05-08
Ryan, Patrick (Department: 1725)
Metal fusion bonding
Process
Using dynamic frictional energy
C228S139000, C228S114500, C228S120000
Reexamination Certificate
active
06227433
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of joining workpieces together via a fastener and, more particularly, to a method of forming a lap joint between two or more workpieces by friction welding a fastener through the workpieces.
BACKGROUND OF THE INVENTION
Mechanical fasteners are widely used for joining together two or more metal members. In most applications of mechanical fasteners, holes are formed through the workpieces to be joined, the holes are aligned, and a fastener is passed through the holes and secured. Generally, the fastener has enlarged head portions at each end to prevent the workpieces from being separated, and may also be designed to apply clamping pressure between the head portions so that the workpieces are firmly held together.
This conventional process of joining via mechanical fasteners has a number of disadvantages. For instance, machining the holes for the fasteners results in increased manufacturing cost. Moreover, the head portions of the fasteners represent added weight and cost to the structure being manufactured. For a structure using many such fasteners, the additional weight and cost of the fastener heads can be significant. Additionally, in many cases a sealant must be applied in the holes through which the fasteners extend in order to provide protection against corrosion or to otherwise seal the joints. Furthermore, the holes in the workpieces cause stress concentrations and thereby weaken the structure, so that thicker members and/or higher strength materials must be used in order to meet design safety margins. Thus, the conventional mechanical fastening process leads to increased weight of the final product, and increased cost for manufacturing the product.
SUMMARY OF THE INVENTION
The present invention overcomes the drawbacks of conventional mechanical fastening processes noted above, by providing a process for friction welding a fastener through two or more workpieces so that a metallurgical bond is formed between the workpieces and the fastener. No holes need be formed through the workpieces prior to application of the fastener, thus reducing manufacturing cost and eliminating stress concentrations associated with holes and their attendant disadvantages noted above. Furthermore, the fastener does not require any head portions, thereby reducing weight. Additionally, no sealants are required because the metallurgical bond with the fastener provides sealing and protection against corrosion, further reducing manufacturing cost.
To these ends, the method of the invention is suitable for joining any lap configured structure made up of two or more overlapping metal workpieces which preferably but not necessarily are constructed of the same material or of materials having substantially the same melting point temperature. The method comprises providing a fastener made of metal having a melting point temperature which is at least as great as the melting point temperature of the workpieces; rotating the fastener about its central axis; axially advancing the rotating fastener into engagement with an outer surface of a first of the workpieces; applying axial force between the fastener and the workpieces so as to cause the fastener to advance axially through the overlapping workpieces, the advancing fastener causing frictional heating and plasticization of the metal of the workpieces adjacent the juncture between the fastener and the workpieces; and stopping the rotation of the fastener when the fastener has advanced through substantially the entire thickness of the overlapping workpieces and has plasticized the metal of the workpieces along substantially the entire juncture with the fastener. The plasticized metal forms a metallurgical bond with the fastener. If the fastener has any portions protruding from either side of the joined workpieces, they may be removed by cutting and/or grinding or other process, so that the fastener is flush with the outer surfaces of the joined structure. The result is a fastened joint that is mechanically superior, is faster and less expensive to produce, and is lighter in weight than a conventional mechanically fastened joint.
In one preferred embodiment of the invention, the fastener has a body portion and an enlarged head portion, and the body portion of the fastener is advanced through the workpieces to cause the head portion to contact the outer surface of the first workpiece. Rotation of the fastener and application of force is continued until plasticization of the first workpiece occurs at the juncture with the head portion, such that a metallurgical bond is formed between the head portion and the outer surface of the first workpiece, in addition to the metallurgical bond formed along the length of the body portion of the fastener.
The fastener may be made of the same material as the workpieces, or alternatively may be made of a material having a higher melting point temperature than that of the workpieces. When the fastener and the workpieces are made of the same material, plasticization of metal occurs in both the workpieces and the fastener adjacent the is juncture therebetween. Alternatively, when the fastener is made of a higher-melting metal, plasticization may occur either in both the workpieces and the fastener or in the workpieces alone, depending on the difference in melting points and the amount of frictional heating produced.
REFERENCES:
patent: 2957237 (1960-10-01), Regle et al.
patent: 3477115 (1969-11-01), Martin et al.
patent: 3481803 (1969-12-01), Hewitt
patent: 3580793 (1971-05-01), Hewitt
patent: 3616980 (1971-11-01), Padilla
patent: 3848389 (1974-11-01), Gapp et al.
patent: 4676707 (1987-06-01), Cearlock et al.
patent: 5230137 (1993-07-01), Abe
patent: 5361478 (1994-11-01), Grossberndt et al.
patent: 5713706 (1998-02-01), Lozano
patent: 6067839 (1998-09-01), Xie
patent: 6095395 (2000-01-01), Fix, Jr.
Forrest Robert Scott
Toosky Ray F.
Waldron Douglas J.
Alston & Bird LLP
Edmondson L.
Ryan Patrick
The Boeing Company
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