Patent Grant
8506201
This invention relates to friction welding and, more specifically, to friction welding of one or more structural members to form a structural assembly.
Structural devices are often formed as assemblies of a number of smaller structural members. Such assembling of individual members may be necessary to form devices that are too large or too complicated to be formed by conventional manufacturing methods. For example, such factors as casting sizes, forging sizes, available plate and block sizes, and the like can limit the size and geometry of the individual structural members that can be manufactured. To form larger or more complex devices, the structural members are typically assembled by joining the individual structural members using a variety of known joining techniques including, for example, mechanical fastening or welding.
Joints formed by mechanical fasteners such as rivets, screws, and bolts typically require an overlap of the structural materials at the joint. The fasteners and the overlap of material result in an increase in weight of the joint and the structural assembly. The joint can also introduce areas of increased stress, for example, around holes drilled for receiving rivets. Alternatively, weld joints can be formed to join the structural members, sometimes requiring little or no overlap of material. However, the formation of conventional weld joints, such as by arc or electron beam welding, can result in undesirable dimensional changes in the structural members. Welding can also introduce porosity or other discontinuities into the structural members or otherwise cause unwanted changes to the material properties of the structural members.
Friction welding has also been proposed as an alternative to conventional welding methods for joining members. Weld joints formed by friction welding generally exhibit refined grain structure as compared to weld joints formed by other conventional weld techniques such as plasma arc welding. Linear friction welding and rotational friction welding can be used to form strong joints without reducing the mechanical characteristics of the joined materials or causing significant dimensional changes. However, each of these conventional friction welding techniques is limited by the dimensions of the structural members and/or the joints to be formed. For example, conventional linear friction welding and rotational friction welding require one member to be moved, i.e., oscillated or rotated, and urged against the other member. Because of the difficulty of moving large structural members, it can be impossible or impractical to join some structural members by these techniques.
Thus, there exists a need for an improved apparatus and method of joining structural members to form structural assemblies. Preferably, the method should enable the manufacture of preforms that approximate the desired dimensions and configuration of the structural assembly and therefore require little machining or other subsequent processing to form the structural assemblies. The method should be adaptable for joining large and/or complex structural members. Further, the method should not add significant weight to the structural assembly, and should minimize dimensional changes and undesirable changes to the material properties of the structural members.
The present invention provides a preform and method for forming a frictionally welded structural assembly. The method includes linear friction welding structural members to a base member and welding each structural member to one or more of the adjacent structural members. The resulting preform can be formed with dimensions and a configuration that approximate the dimensions and configuration of the structural assembly. Thus, the assembly can be formed from the preform with a reduced amount of machining or other processing, thereby saving time, materials, and energy. Further, the structural assembly can be formed by joining multiple members that are generally smaller than the finished assembly.
According to one embodiment of the present invention, the method includes reciprocatingly moving a first structural member relative to the base member and urging the first hstructural member against a first surface of the base member. A plasticized region of material is formed between the first structural member and the base member, and the first structural member is thereby linear friction welded to the base member. The first structural member defines a connection surface that extends from the base member at an angle relative to the first surface of the base member. A second structural member can be urged against the connection surface and the base member and reciprocatingly moved to linear friction weld the second structural member to the base member and the first structural member. The connection surface of the first structural member and a corresponding surface of the second structural member can be disposed at an oblique angle relative to the first surface of the base member. Additional structural members can also be friction welded to the base member and one or more of the other structural members. After the structural members are welded to the base member, the base member and/or the structural members can be machined to the predetermined configuration of the structural assembly. The base members and structural members can be formed of materials such as aluminum, aluminum alloys, titanium, titanium alloys, steel, nickel-based alloys, copper-based alloys, and beryllium-based alloys.
According to another embodiment of the present invention, first and second structural members can be linear friction welded to a base member so that the two structural members define a space therebetween. For example, the first and second structural members can have connection surfaces disposed so that the space tapers in a direction toward the base member. A third structural member can then be linear friction welded to the base member and the first and second structural members in the space between the first and second structural members.
According to yet another embodiment of the present invention, first and second structural members can be linear friction welded to a base member so that connection surfaces of the structural members are directed in an opposing configuration to define an interface therebetween. A rotating friction stir welding pin can be urged through the structural members to form a friction stir weld joint that extends generally along the interface and joins the first and second structural members. According to one aspect of the invention, the friction stir welding tool is urged along a path that is not parallel to the interface. Also, the structural members can be positioned with a space at the interface, and the space can be filled with plasticized material during the friction stir welding operation.
The present invention also provides a preform for forming a structural assembly of a predetermined configuration. The preform includes a base member and structural members that are connected by linear friction weld joints to the base member. The adjacent structural members also define correspondingly angled connection surfaces that are connected by a friction weld joint such as a linear friction weld joint or friction stir weld joint. Advantageously, the base and structural members can be configured to correspond to the predetermined configuration of the structural assembly. The base member and the structural members can be formed of materials such as aluminum, aluminum alloys, titanium, titanium alloys, steel, nickel-based alloys, copper-based alloys, and beryllium-based alloys.
The foregoing and other advantages and features of the invention, and the manner in which the same are accomplished, will become more readily apparent upon consideration of the following detailed description of the invention taken in conjunction with the accompanying drawings, which illustrate preferred and exemplary embodiments, but which are not necessarily drawn to scale, wherein:
The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout.
Referring to the drawings and, in particular, to
The structural assemblies 10 of the present invention can be formed from any number of structural members depending on the desired dimensions and configuration of the structural assembly 10. Further, the configuration and material composition of the structural members can be formed and selected according to the specifications and design requirements of the structural assembly 10. For example, as illustrated in
The base member 22 illustrated in
In addition to the material composition and properties of the base and structural members 22, 24, 26, 28 the selection of the members 22, 24, 26, 28 is also based on the desired dimensions of the structural assembly 10 that is to be formed. More specifically, the desired dimensions of the structural assembly 10 can be determined first, and the base and structural members 22, 24, 26, 28 can then be selected so that the resulting preform 20 will correspond in configuration to the structural assembly 10, i.e., the configuration of the preform 20 is such that material can be machined or otherwise removed or reconfigured to achieve the dimensions of the finished structural assembly 10. Advantageously, by constructing preforms 20 having dimensions and configurations closely or substantially approximating the predetermined dimensions and configuration of the corresponding structural assembly 10, machining time and material waste can be minimized, making the assemblies 10 more economical to produce. The selection of materials and the subsequent formation of preforms 20 and structural assemblies 10 therefrom are described in U.S. application Ser. No. 10/092,675, titled “Preforms for Forming Machined Structural Assemblies,” filed Mar. 7, 2002, which is assigned to the assignee of the present invention and the entirety of which is incorporated herein by reference.
The structural assemblies 10 of the present invention can be used as structural components of a vehicle, such as an aircraft, automobile, or marine craft. For example, the structural members 10 can be panels, spars, beams, or other components that are joined to form a wing, wing support structure, fuselage, and the like of an airplane. Alternatively, the assemblies 10 can be used in buildings, machinery, and the like.
Generally, the structural assembly 10 is formed by connecting the structural members 24, 26, 28 to the base member 22 and connecting the structural members 24, 26, 28 to one another. The base member 22 and/or the structural members 24, 26, 28 can then be machined or otherwise trimmed or processed to the dimensions of the structural assembly 10.
The structural members 24, 26, 28 are connected to the base member 22 by welding and, in particular, the structural members 24, 26, 28 are preferably linear friction welded to the base member 22. For example, as shown in
The relative motion between each of the structural members 24, 26 and the base member 22 generates frictional heating that plasticizes a portion of the structural member 24, 26 and/or the base member 22. Once sufficient plasticization has occurred, the reciprocating motion of the structural member 24, 26 is terminated. Plasticization can be detected, for example, by mechanical or optical measurements, or friction welding can be continued for a predetermined duration based on such factors as the type of materials being joined, the size or type of the joint to be formed, and the compressive force therebetween. After the motion of the structural member 24, 26 is terminated, the compressive force between the structural member 24, 26 and the base member 22 can be maintained by continuing to urge the structural members 24, 26 in direction 38 against the base member 22 as the structural member 24, 26 and the base member 22 cool to thereby form a friction weld joint 40 between the structural members 24, 26 and the base member 22.
It is appreciated that the forces and ranges of motion required for linear friction welding the structural members 24, 26 to the base member 22 can vary according to such factors as the material of the members 22, 24, 26, the dimensions of the members 22, 24, 26, the surface finishes of the members, and the like. For example, according to one embodiment of the present invention, in which the members 22, 24, 26 are formed of aluminum, each of the structural members 24, 26 is urged in direction 38 against the base member 22 with a force sufficient to provide a pressure of about 20,000 psi between the structural member 24, 26 and the base member 22. The structural members 24, 26 are reciprocated about 0.1 inch alternately in directions 30, 32.
In other embodiments of the invention, the structural members 24, 26 can be reciprocated in other directions while being urged against the base member 22. Further, it is appreciated that while the motion of the structural members 24, 26 is generally linear in the alternating directions, the motion of each structural member 24, 26 can have some nonlinear component of motion, e.g., so that the motion of each structural member 24, 26 defines an elliptical path. Alternatively, the structural members 24, 26 can be connected to the base member 22 by other types of friction weld joints such as rotary friction weld joints. Preforms with rotary friction weld joints and methods therefor are described in U.S. application Ser. No. 10/737,873, entitled “Structural Assemblies and Preforms therefor Formed by Friction Welding,” filed concurrently herewith, assigned to the assignee of the present application, and the contents of which is incorporated herein in its entirety by reference.
The first and second structural members 24, 26 are friction welded to the base member 22 with a space 18 therebetween for receiving the third structural member 28. More particularly, as illustrated in
Thereafter, the third structural member 28 is welded to the base member 22 and each of the first and second structural members 24, 26. For example, the third structural member 28 can be linear friction welded to the members 22, 24, 26 by urging the third structural member 28 in direction 38 against the base member 22 and the connection surfaces 34, 36 of the structural members 24, 26 and reciprocatingly moving the third structural member 28 in the directions 30, 32. The third structural member 28 can be grasped by the jaws 50 and actuated by one or more actuators, e.g., the same actuators used to move the other structural members 24, 26. At least a portion of the third structural member 28 and/or the base member 22, first structural member 24, or second structural member 26 is plasticized as previously described to form linear weld joints 42, 44, 46 between the third structural member 28 and each of the base member 22 and the first and second structural members 24, 26.
Thus, each of the structural members 24, 26, 28 is friction welded to the base member 22, and the third structural member 28 joins the first and second structural members 24, 26, as shown in
Each of the third and fourth structural members 128a, 128b is friction welded to the base member 122 and at least one of the first and second structural members 124, 126. For example, as shown in
The resulting preform 120, shown in
In the embodiments illustrated in
After the first and second structural members 224, 226 are joined to the base member 222, the structural members 224, 226 can be joined by friction stir welding. For example, the members 224, 226 can be friction stir welded with a rotatable friction stir welding tool 260 that includes a pin 262 extending from a shoulder 264. With the tool 260 rotating in direction 266, the shoulder 264 (which is not shown in
For example, as shown in
As discussed above in connection with
It is also noted that the structural members can be configured in various other configurations prior to friction stir welding. For example,
In addition, it is appreciated that the tool 260a can be urged and moved through the members 24a, 26a, 28a in various directions to form the friction stir weld joints 44a, 46a. For example, the tool 260a can be urged along a longitudinal direction of the members 24a, 26a, 28a, i.e., in a direction that is perpendicular to the direction 33a and parallel to the base member 22a. The friction stir weld joints 44a, 46a can be disposed to connect the portions of the interfaces of the structural members 24a, 26a, 28a that ultimately are used to form the structural assembly, though the friction stir weld joints 44a, 46a need not join the entire area of the connection surfaces 34a, 36a to the third structural member 28a.
It is appreciated that the granular structure of one or more of the members 22, 24, 26, 28, 122, 124, 126, 128a, 128b, 222, 224, 226 can be refined by the friction welding operations. Thus, in some cases, the welding of the various members can enhance the material properties thereof, e.g., by increasing the strength, ductility, or corrosion resistance of one or more of the members. Further, the members can be thermally or chemically treated before, during, or after formation of the structural assemblies. For example, the members can be heat treated individually or in combination before being joined. Alternatively, or in addition, the preforms 20, 120, 220 or structural assemblies 10, 110, 210 formed from the members can be exposed to other processing to relieve stress or improve strength. Processing can include subjecting the preforms and/or structural assemblies to a predetermined heating schedule which can include annealing, quenching, aging, solution annealing, and the like as is known in the art. Further, the preforms 20, 120, 220 or structural assemblies 10, 110, 210 can be formed after the members have been welded to change the shape of the preforms 20, 120, 220 or structural assemblies 10, 110, 210, for example, by bending the preforms 20, 120, 220 or structural assemblies 10, 110, 210 to a desired shape.
Many modifications and other embodiments of the invention will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
This application is a divisional of U.S. application Ser. No. 10/738,594, filed Dec. 16, 2003, now U.S. Pat. No. 7,225,965 B2, which is hereby incorporated herein in its entirety by reference.
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| Number | Date | Country | |
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| Number | Date | Country | |
|---|---|---|---|
| Parent | 10738594 | Dec 2003 | US |
| Child | 11740520 | US |
