Patent Application
20070289351
1. Field of Disclosure
This disclosure generally relates to a structural member, such as a bushing, having geometrical features that may reduce surface upset at the ends of the member when the member is radially expanded into a workpiece.
2. Description of the Related Art
Conventional structural members, which may be hollow members such as bushings, with or without a radial flange, liners, sleeves, tubes, pipes, etc. are commonly installed into openings of workpieces for a variety of reasons. Bushings, for example, may be installed in the workpiece to reinforce and/or structurally support the region around the opening. In addition, the radial flange of the bushing may function as a washer to transmit the fastener clamp-up loads into the workpiece and/or structural joint.
One method of installing structural members, which shall be referred to in this section as bushings, is the FORCEMATE® installation method developed by Fatigue Technology, Inc. The FORCEMATE® installation method is especially suitable for components that will undergo repetitive load cycles and/or may be susceptible to accumulating fatigue damage. The FORCEMATE® installation method utilizes an installation tool to pass a tapered mandrel (i.e., expansion mandrel) through a passage in the bushing after the bushing has been placed in the opening of the workpiece. The tapered mandrel radially expands the bushing into the opening to obtain a controlled, but consistently higher, interference fit than would be achievable by other installation methods, such as shrink or press fitting methods. In addition, the FORCEMATE® installation method may induce beneficial residual compressive stresses into the structural material surrounding the opening, which may advantageously extend the fatigue and damage tolerance (e.g., crack growth) life of the component, assembly, and/or installation. The FORCEMATE® installation method, as well as other cold-working methods, tooling, and the like, such as the BUSHLOC®, FORCETEC®, and FLEXMATE® methods are described in U.S. Pat. Nos. 3,566,662; 3,892,121; 4,187,708; 4,423,619; 4,425,780; 4,471,643; 4,524,600; 4,557,033; 4,809,420; 4,885,829; 4,934,170; 5,083,363; 5,096,349; 5,405,228; 5,245,743; 5,103,548; 5,127,254; 5,305,627; 5,341,559; 5,380,136; 5,433,100; and in U.S. patent application Nos. U.S. patent application Ser. Nos. 09/603,857; 10/726,809 (U.S. Pat. No. 7,100,264); 10/619,226 (U.S. Pat. No. 7,024,908); and 10/633,294 (US/2005/0025601).
Installation of conventional bushings has been known to produce a certain amount of extruded material, upset material, and/or distorted material, near at least one end of the bushing. In some cases, the amount of upset material is typically minimal and may be removed with a subsequent machining process to make the upset material substantially flush with the corresponding end surface of the bushing (e.g., the end surface may be the exposed end surface of the radial flange or may be the exposed end surface of the non-flange end of the bushing).
Conventional bushings are typically configured to have the non-flanged end surface be a bit under-flush to flush, but not over-flush, relative to the surface of the workpiece. To achieve such an under-flush condition, a number of variables should be accounted for, such as the workpiece thickness tolerance, the bushing manufacturing length tolerance, and/or the extrusion or growth of the bushing during the radial expansion installation process.
In wing assemblies, for example, the installed bushings must meet specific flushness requirements. One such requirement in the aerospace industry is that the non-flanged end of the bushing must be flush to under flush within a range of 0 to 0.008 inches from the workpiece surface to maximize the bearing area of the bushing in the workpiece. If a bushing were to be installed in an over-flush or protruding condition relative to the workpiece surface, such a condition may cause the protruding bushing end to contact and/or damage a mating part. In addition, such an over-flush bushing condition may adversely alter the fastener clamp-up load distribution through the assembled members. Such an altered load path is typically undesirable, and may lead to structural joint problems after the airplane is in service.
To correct an over-flush condition and/or to remove the upset material, the excess material may be machined off (i.e., ground). If the workpiece is a titanium lug or a hardened, surface-treated steel, for example, extreme care must be taken to not damage the workpiece when using a grinding wheel to remove the excess or over-flush portion of the bushing. This type of a machining operation to bring the bushing flush with the workpiece may be done hundreds of times in a single component, such as a wing skin or fuselage skin. In turn, this may add significant time and cost to the overall assembly, as well as increase the risk of damaging the overall assembly, which may be nearly complete.
The amount of bushing extrusion may vary significantly based upon a particular application. For example, some assemblies may call for the installation of a bushing that has a thick wall. Radially expanding a thick-walled bushing into a workpiece typically requires a larger mandrel pull or draw force. The large force often results in a greater amount of bushing material being upset and may also result in the formation of a substantially large extrusion or growth from at least one end of the bushing. Additionally, or alternatively, the extrusion or growth may not be uniform across the non-flanged end of the bushing where, for example, the majority of the growth occurs in an area adjacent to the inner surface of the bushing.
It has been determined that the overall grip length of one type of thick-walled bushing may vary by as much as ±0.020 inches from a pre-installed state with no upset material present at one end of the bushing to a post-installed state with upset material present. This type of bushing growth makes it difficult to keep the entire bushing end surface flush or under-flush relative to the workpiece surface during installation of the bushing.
The upset material is extruded and/or displaced axially from at least one end of the bushing as the tapered mandrel is passed through the bushing. In one instance, a wave of material adjacent to the inner-surface region of the bushing is longitudinally pulled or pushed in the direction of the mandrel travel. In another instance, the radial force of the tapered mandrel causes at least a small amount of material to be pushed axially out and away from the mandrel entry side of the bushing. Thus, the upset material may occur on the flange side or the opposite side of the bushing. The amount of upset material on a particular side of the bushing corresponds, at least in part, to the direction of the mandrel travel.
Consequently, conventional bushings may not adequately and repeatedly meet certain quality and/or aerodynamic requirements or specifications. Based on the foregoing, it would be desirable to have a bushing or like component configured to overcome at least some of the aforementioned drawbacks of conventional bushings when radially expanded into a workpiece.
At least one embodiment generally relates to a bushing having a unique geometric end feature such as a countersink detail, a counterbore, or a combination of the two features, for the purpose of receiving an amount of material that is extruded in a longitudinal direction during radial expansion of the bushing. At the mandrel exit side of the bushing, the extruded material may be accumulated from a propagating wave of material preceding a radial expansion mandrel. At the mandrel entry side of the bushing, the extruded material may be caused by the radial force of the expansion mandrel near the unrestrained end surface at the entry side of the bushing. The unique geometric end features of the bushing may also include a high portion on the end surface of the bushing to direct the fastener clamp-up loads through the radial flange of the bushing and into the workpiece.
In one aspect, a structural member installable in an opening of a workpiece by radial expansion via an expansion mandrel includes a tubular body having a first end, a second end opposite the first end, a peripheral outer surface disposed between the first and the second ends, the tubular body having a first face at the first end, a second face at the second end, and an inner surface that extends between the first and the second ends to form a longitudinally-extending passage therebetween, wherein in a pre-installed state the tubular body has a first recess formed on the first face about the longitudinally-extending passage and adjacent thereto, the first recess having a volume sized to accommodate a first amount of upset material that will be formed by passage of the expansion mandrel through the longitudinally-extending passage to install the structural member in the opening of the workpiece.
In another aspect, a structural member installation includes a workpiece having an opening formed therein; and a tubular body having a first end, a second end opposite the first end, a peripheral outer surface disposed between the first and the second ends, the tubular body having a first face at the first end, a second face at the second end, and an inner surface that extends between the first and the second ends to form a longitudinally-extending passage therebetween, wherein in an installed state the peripheral outer surface deformingly engages the workpiece to form an interference fit therewith and a first amount of upset material formed by passage of an expansion mandrel through the longitudinally-extending passage to install the structural member in the opening of the workpiece is accommodated by a first recess adjacent to and surrounding the longitudinally-extending passage such that the first amount of upset material does not extend outwardly from the first face of the tubular body or inwardly from the inner surface into the longitudinally-extending passage.
In yet another aspect, a method of radially expanding a structural member into a workpiece includes positioning an expansion mandrel at an entrance of a longitudinally-extending passage extending through the structural member, the structural member having a first end, a second end opposite the first end, a peripheral outer surface disposed between the first and the second ends, the structural member further having a first face at the first end, a second face at the second end, and an inner surface that extends between the first and the second ends to form the longitudinally-extending passage therebetween; passing the expansion mandrel through the longitudinally-extending passage from the first face to a second face of the structural member to radially expand at least a portion of the structural member into the workpiece; and longitudinally displacing some of the material of the structural member into at least one recess having a volume sized to accommodated a first amount of upset material, wherein the volume of the recess is sufficient to receive the displaced material without permitting any of the displaced material to extend beyond a desired distance relative to the respective face.
In still yet another aspect, a method of manufacturing a structural member to be secured into an opening of a workpiece, the method includes forming an outer surface and an inner surface, the outer surface radially offset from the inner surface to form a wall of the structural member; forming first end and a second end opposite the first end; forming a first face at the first end and a second face at the second end, the inner surface extending between the first and the second ends to form a longitudinally-extending passage therebetween; and forming a recess into at least one of either the first face or the second face, wherein the recess defines a volume sized to accommodated a first amount of upset material expected when an expansion mandrel is passed through the longitudinally-extending passage during a radial expansion process to secure the structural member into the opening of the workpiece.
In the drawings, identical reference numbers identify similar elements or acts. The sizes and relative positions of elements in the drawings are not necessarily drawn to scale. For example, the shapes of various elements and angles are not drawn to scale, and some of these elements are arbitrarily enlarged and positioned to improve drawing legibility. Further, the particular shapes of the elements as drawn are not intended to convey any information regarding the actual shape of the particular elements and have been solely selected for ease of recognition in the drawings.
In the following description, certain specific details are set forth in order to provide a thorough understanding of various disclosed embodiments. However, one skilled in the art will understand that the embodiments may be practiced without these details. In other instances, well-known structures and methods associated with cold working and/or installing a structural member into an opening in a workpiece may not be shown or described in detail to avoid unnecessarily obscuring descriptions of the disclosed embodiments. The structural member can be a bushing, sleeve (including a split sleeve), liner, shank, rivet, or other similar component. It is appreciated and understood that the process of installing the component into the opening of the workpiece may or may not result in the creation of a zone of residual compressive stress (e.g., an annular zone of compressive stresses) in the workpiece or workpieces.
In the following description and for purposes of brevity, reference shall be made to cold working and/or radial expanding of the workpiece. This reference is not intended to limit or otherwise narrow the scope of the disclosure. In the context of this description, the process of cold expansion is to be broadly interpreted as any process that radially expands at least some of the material surrounding the opening in the workpiece, even if the expansion is for the purpose of impeding the growth of a fatigue crack. It is further understood that cold expanding the opening of the workpiece may or may not induce beneficial compressive residual stresses and may or may not produce fatigue-enhancing benefits in the workpiece.
Unless the context requires otherwise, throughout the specification and claims which follow, the word “comprise” and variations thereof, such as “comprises” and “comprising,” are to be construed in an open, inclusive sense, that is as “including, but not limited to.”
The headings provided herein are for convenience only and do not interpret the scope or meaning of the claimed invention.
The following description generally relates to a structural member with geometric features that permit the member to be radially expanded into an opening of a workpiece while reducing, limiting, or substantially eliminating unwanted deformed, upset, or distorted regions of the member that may adversely affect the structural joint and/or create an undesirable installation condition. In some embodiments, the structural member may even be the workpiece itself. By way of example, the process of passing an expansion mandrel through a thick-walled bushing and radially expanding the thick-walled bushing into the workpiece may result in at least some amount of deformation (e.g., upset, displaced, and/or distorted material) near both the mandrel entry and exit sides of the bushing.
In some bushing installations in which the mandrel is pulled from the non-flanged end toward the flanged end of the bushing, the radial flange of the bushing may move away or separate from the workpiece, thus creating an undesirable gap between the radial flange of the bushing and the workpiece. Gaps between the bushing and the workpiece can significantly reduce the performance of the installation.
Large stresses can develop in the bushing. As the mandrel is passed through the busing, the stresses can result in a plastic flow of bushing material with a large amount of residual strain energy. The residual strain energy can be relieved as the mandrel exits through the upset material and displacement of the radial flange. The bushing flange may be re-seated against the workpiece in a subsequent seating operation. However, this seating operation may have to be performed hundreds of times for a single component, which may increase the time and the cost to manufacture the component.
The inner surface 216 may be allowed to displace axially during the expansion process. The lack of axial constraint permits at least some of the material along and adjacent to the inner surface 216 of the structural member 204 to be axially deformed (e.g., permanently upset or distorted). In the illustrated embodiment, a first upset region 226 is observable at the mandrel entry side 228 of the structural member 204, while a second upset region 230 is observable at the mandrel exit side 232.
In conjunction with the formation of the upset region 230, a pocket 234 may be formed by an end surface 235 of the structural member 204. The structural member 204 can be configured with an under-flush grip length before the member is installed into the workpiece 202, which results in the illustrated under-flush end surface 235.
As the fastener 440 and nut 442 combination is torqued down, the first upset region 426 causes the clamp-up forces in the structure to proceed approximately along a load path line 448, which may generate a substantial amount of shear stress between the radial flange 451 and a body 453 of the first structural member 404, where the shear region is shown by dashed line 449. It is typically advantageous in a structural joint to have the load path line 448 from the fastener clamp-up forces be carried directly through the radial flange 411 and into the first workpiece 402 to reduce or limit the shear stresses in the region 415. Consequently, the upset region 426, with or without the additional flange gapping, may cause an undesirable load path through the structural joint 400.
The illustrated structural member 500 includes an outer circumferential surface 502 and an inner surface 504 that forms a passage 506 through the structural member 500, according to one illustrated embodiment. In addition, the structural member 500 includes a first surface 508 and a second surface 510 opposed to the first surface 508. In the illustrated embodiment, the first surface 508 is substantially perpendicular to a longitudinal axis 511 of the structural member 500. In some embodiments, a radial flange contact surface 509 is substantially perpendicular to the longitudinal axis 511 and the surface 508 may be non-perpendicular to the axis 511. The arrow 513 represents the direction the mandrel 106 (
The second surface 510 includes a first region 512 and a second region 514. A portion 512a of the first region 512, which is radially adjacent to and/or includes a portion of the inner surface 504, is longitudinally located from the first surface 508 by a first member length 516.
The second region 514 extends radially outward from the first region 512. A portion 514a of the second region 514, which is radially located farthest from the inner surface 504, is longitudinally located from the first surface 508 by a second member length 518. In one embodiment, the first member length 516 is less than the second member length 518 such that the first region 512 and the second region 514 form a recess 520.
The recess 520 may generally be referred to as, but not limited to, a pocket, countersink, counterbore, chamfer, taper, or the like. The recess 520 is dimensioned to receive at least some material that may be deformed when the structural member 500 is installed (e.g., radially expanded into the opening of a workpiece). The recess 520 can define a volume sized to receive a desired amount of mandrel exit upset material 530 (
The structural member 500 can further include an entry recess 526 defined by a surface 527 (illustrated as an arcuate surface). The surface 527 extends between the inner surface 504 and the first surface 508. The entry recess 526 can receive a selected amount of mandrel entrance upset material 532 (
The second surface 612 includes a first region 614 and a second region 616. A portion 614a of the first region 614, which is radially adjacent to and/or includes a portion of the inner surface 604, is longitudinally located from the first surface 610 by a first member length 618. The second region 616 extends radially outward from the first region 614. A portion 616a of the second region 616 is radially spaced from the inner surface 604 and is radially farther from the longitudinal axis 611 than the outer surface 602. In addition, the portion 616a of the second region 616 is longitudinally located from the first surface 610 by a second member length 620. In one embodiment, the first member length 618 is less than the second member length 620 such that the first region 614 and the second region 616 form a recess.
The recess 622 may generally be referred to as, but not limited to, a countersink, gradual taper, and/or an arcuate surface. The recess 622 is dimensioned to receive a selected amount of a mandrel exit upset material 630 (
In some embodiments, the volume of the recess 622 is sufficient to receive the mandrel exit upset material 630 without permitting the mandrel exit upset material 630 to extend beyond a portion 634 of the structural member 600. In another embodiment, the volume of the recess 622 is sufficient to receive the mandrel exit upset material 630 without permitting the material 630 to extend up to and/or become flush with the portion 634 of the structural member 600. In the illustrated embodiment, the surface 626 is angled by an angle, θ, towards the first surface 610, such that the portion 634 is located farthest from the first surface 610 relative to the surfaces 612 and 626.
One purpose for having the surface 626 angled towards the first surface 610 and not allowing the mandrel exit upset material 630 to extend beyond the portion 634 is to ensure that a load path 638 (e.g., the load path for the fastener clamp-up loads or other applied loads) goes through the radial flange 608 and directly into the workpiece 102.
The portion 634 can be located radially outwardly from a cutout 640 so that the load path 638 does not travel through the thinnest or narrowed portion of the radial flange 608. Accordingly and as illustrated, the portion 634 is located radially outward on the flange 608 to allow the fastener clamp-up loads to be reacted through the radial flange 608, which may operate as a washer to spread the load into the workpiece 102. If the mandrel exit upset material 630 were permitted to extend beyond the portion 634, the fastener clamp-up loads would react through the bushing wall 642 and generate a non-desirable shear load 644 through the radial flange 608. Further, another countersink surface 628 may accommodate the mandrel entrance upset material 632.
The various embodiments described above can be combined to provide further embodiments. All of the above U.S. patents, patent applications and publications referred to in this specification as well as U.S. Pat. Nos. 3,566,662; 3,892,121; 4,187,708; 4,423,619; 4,425,780; 4,471,643; 4,524,600; 4,557,033; 4,809,420; 4,885,829; 4,934,170; 5,083,363; 5,096,349; 5,405,228; 5,245,743; 5,103,548; 5,127,254; 5,305,627; 5,341,559; 5,380,136; 5,433,100; and U.S. patent application Ser. Nos. 09/603,857; 10/726,809 (U.S. Pat. No. 7,100,264); 10/619,226 (U.S. Pat. No. 7,024,908); and 10/633,294 (US/2005/0025601) are incorporated herein by reference. Aspects can be modified, if necessary, to employ devices, features, and concepts of the various patents, applications, and publications to provide yet further embodiments.
These and other changes can be made in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the invention to the specific embodiments disclosed in the specification and the claims, but should be construed to include all types of bushings, sleeves, liners, and other similar components that are installable in an opening of a workpiece and that operate in accordance with the claims. Accordingly, the invention is not limited by the disclosure, but instead its scope is to be determined entirely by the following claims.
This application claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Patent Application No. 60/795,888 filed Apr. 27, 2006, which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 60795888 | Apr 2006 | US |
