Title:
Wave relieving geometric features in structural members that are radially expandable into workpieces
Kind Code:
A1


Abstract:
A bushing with wave relieving geometric features includes a unique geometric end feature such as a countersink or arcuate surface, which creates a pocket, volume, and/or reservoir, to receive 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.



Inventors:
Glenn, Douglas W. (Des Moines, WA, US)
Application Number:
11/796545
Publication Date:
12/20/2007
Filing Date:
04/27/2007
Assignee:
Fatigue Technology, Inc. (Seattle, WA, US)
Primary Class:
Other Classes:
72/392
International Classes:
B21D39/08
View Patent Images:



Primary Examiner:
BATTULA, PRADEEP CHOUDARY
Attorney, Agent or Firm:
SEED INTELLECTUAL PROPERTY LAW GROUP PLLC (701 FIFTH AVE, SUITE 5400, SEATTLE, WA, 98104, US)
Claims:
What is claimed is:

1. A structural member installable in an opening of a workpiece by radial expansion via an expansion mandrel, the structural member comprising: 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.

2. The structural member of claim 1 wherein in the pre-installed state the tubular body has a second recess formed on the second face about the longitudinally-extending passage and adjacent thereto, the second recess having a volume sized to accommodate a second 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.

3. The structural member of claim 2 wherein the volume of one of the first or the second recesses is sized to accommodate an entrance amount of upset material formed by entrance of the expansion mandrel into the opening of the workpiece and wherein the volume of the other one of the first or the second recesses is sized to accommodate an exit amount of upset material formed by exit of the expansion mandrel from the opening of the workpiece, wherein the entrance amount of upset material is not equal to the exit amount of upset material.

4. The structural member of claim 1, further comprising: a radial flange radially extending from the peripheral outer surface of the tubular body, the radial flange proximate one of the first end or the second end thereof.

5. The structural member of claim 1 wherein the longitudinally-extending passage is concentric with the peripheral outer surface.

6. The structural member of claim 5 wherein a cross-section of the peripheral outer surface taken perpendicularly to a longitudinal axis of the longitudinally-extending passage is approximately circular.

7. The structural member of claim 6 wherein a cross-section of the longitudinally-extending passage taken perpendicularly to the longitudinal axis of the longitudinally-extending passage is approximately circular.

8. The structural member of claim 1 wherein the structural member comprises at least one selected from the group consisting of a liner, a bearing, a fastener, a shank, and a conduit.

9. The structural member of claim 1 wherein the structural member is a rivet, and further comprises: a radial flange sized to engage at least a portion of a nut cage.

10. A structural member installation, comprising: 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 beyond the first face of the tubular body or inwardly from the inner surface into the longitudinally-extending passage.

11. The structural member installation of claim 10 wherein, in the installed state, a second 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 is accommodated by a second recess adjacent to and surrounding the longitudinally-extending passage such that the second amount of upset material does not extend outwardly from the second face of the tubular body or inwardly from the inner surface into the longitudinally-extending passage.

12. The structural member installation of claim 10 wherein the first amount of upset material is not equal to the second amount of upset material.

13. The structural member installation of claim 10, further comprising: a radial flange radially extending from the peripheral outer surface of the tubular body, the flange proximate one of the first end or the second end.

14. The structural member installation of claim 10 wherein the longitudinally-extending passage is concentric with the peripheral outer surface, a cross-section of the peripheral outer surface taken perpendicularly to a longitudinal axis of the longitudinally-extending passage is approximately circular, and a cross-section of the longitudinally-extending passage taken perpendicularly to the longitudinal axis of the longitudinally-extending passage is approximately circular.

15. A method of radially expanding a structural member into a workpiece, the method comprising: 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 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 of the structural member, the 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.

16. The method of claim 15 wherein longitudinally displacing some of the material of the structural member into the at least one recess includes displacing an amount of material into the recess in the form of a pocket defined by an arcuate surface.

17. The method of claim 15 wherein longitudinally displacing some of the material of the structural member into the at least one recess includes moving a wave of the material ahead of the expansion mandrel passing through the longitudinally-extending passage.

18. The method of claim 15 wherein longitudinally displacing some of the material of the structural member into the at least one recess includes permanently deforming an amount of the material in a region proximate to where the expansion mandrel enters the structural member.

19. A method of manufacturing a structural member to be secured into an opening of a workpiece, the method comprising: 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 a 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.

20. The method of claim 19 wherein forming the recess includes machining the first face so as to form the recess, the recess located adjacent the longitudinally-extending passage.

21. The method of claim 19 wherein forming the recess includes machining the second face so as to form the recess, the recess located adjacent the longitudinally-extending passage.

22. The method of claim 19 wherein forming the first end includes forming a radial flange.

23. The method of claim 22 wherein forming the recess includes machining in at least a portion of the radial flange to form at least a portion of the recess.

24. The method of claim 19 wherein forming the recess includes forming an arcuate surface on at least one of either the first face or the second face of the structural member.

25. The method of claim 19 wherein forming the recess includes forming a countersink surface on at least one of either the first face or the second face of the structural member.

Description:

CROSS-REFERENCE TO RELATED APPLICATION

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.

BACKGROUND

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.

SUMMARY OF THE INVENTION

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.

BRIEF DESCRIPTION OF THE DRAWINGS

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.

FIG. 1 is a cross-sectional view of a prior art structural member in an opening of a workpiece, wherein the structural member is about to be radially expanded by an expansion mandrel, according to one illustrated embodiment.

FIG. 2 is a cross-sectional view of the prior art structural member of FIG. 1 after being radially expanded in the opening of the workpiece, wherein the structural member includes first and second displaced-material portions formed during a radial expansion process, according to one illustrated embodiment.

FIG. 3 is a detailed cross-sectional view of the first displaced material portion of FIG. 2, wherein the first displaced-material portion is located at a mandrel entrance side of the structural member, according to one illustrated embodiment.

FIG. 4 is a detailed cross-sectional view of the second displaced-material portion of FIG. 2, wherein the second displaced-material portion is located at a mandrel exit side of the structural member, according to one illustrated embodiment.

FIG. 5 is a cross-sectional view of a prior art installation of two workpieces that are adversely influenced by displaced-material portions of a radially-expanded structural member located in one of the workpieces, according to one illustrated embodiment.

FIG. 6A shows the prior art installation of FIG. 5 having a fastener to clamp the two workpieces together, according to one illustrated embodiment.

FIG. 6B shows another prior art installation having a fastener to clamp the two workpieces together, according to one illustrated embodiment.

FIG. 7 is a cross-sectional view of a first structural member in a pre-radially expanded state having geometric features capable of accommodating an amount of displaced material expected when the first structural member is radially expanded with a cold-expansion mandrel, according to one illustrated embodiment.

FIG. 8 is a cross-sectional view of the first structural member of FIG. 7 in a post-radially-expanded state showing the displaced material received in the geometric features, according to one illustrated embodiment.

FIG. 9 is a cross-sectional view of a second structural member in a pre-radially expanded state having geometric features capable of accommodating an amount of displaced material expected when the second structural member is radially expanded with a cold-expansion mandrel, according to one illustrated embodiment.

FIG. 10 is a cross-sectional view of the second structural member of FIG. 9 in a post-radially-expanded state showing the displaced material received in the geometric features, according to one illustrated embodiment.

DETAILED DESCRIPTION

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.

FIG. 1 shows a pre-radially-expanded installation 100 comprising a workpiece 102 and a conventional, pre-radially-expanded structural member 104. An expansion mandrel 106 is passed through the structural member 104 to radially expand the structural member 104 into the workpiece 102. For example, the mandrel 106 may be pulled in a mandrel direction 108, which in the illustrated embodiment is directed from the flange side 110 to the non-flange side 112 of the structural member 104.

FIG. 2 shows a radially-expanded installation 200 comprising a workpiece 202 and a radially-expanded structural member 204. A mandrel (e.g., the mandrel 106 of FIG. 1) passing through the structural member 204 in the mandrel direction 208 radially expands the structural member 204 such that an outer surface 214 of the radially-expanded member forms a tight interference fit with the workpiece 202. The inner perimeter of a passage 218 formed by the inner surface 216 is enlarged by the passage of the mandrel. A wall thickness between the outer and the inner surfaces 214, 216 may be reduced by the passage of the mandrel. In addition, the radially-expanded structural member 204 includes a first surface 220 and an opposing second surface 222. In one embodiment, the radially-expanded structural member 204 may include a radial flange 224. Other embodiments may omit the radial flange 224.

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.

FIG. 3 shows a detailed view of the upset region 226 located along and adjacent to the inner surface 216 and further located at the mandrel entry side 228. The first upset region 226 may be formed because the first surface 220 is a free surface and a Poisson's affect occurs due to the radial-expansion force of the mandrel 106 (FIG. 1) near the entry side 228. The Poisson's affect is generally understood to mean that the lateral or transverse strain normal to the direction of the applied stress in an elastic member is not equal to zero. “Mechanics of Materials,” by Ferdinand P. Beer and E. Russell Johnston, Jr., 1991, by McGraw-Hill, Inc. In the illustrated embodiment, the applied stress is the radial stress from the mandrel 106 while the transverse strain comprises the first upset region 226.

FIG. 4 shows a detailed view of the upset region 230 located along and adjacent to the inner surface 216 and further located at the mandrel exit side 232 of the member 204. Generally, the upset region 230 at the mandrel exit side 232 will be larger than the upset region 226 at the mandrel entry side 228 because the upset region 230 is typically caused by a wave of material that is drawn or pushed by the mandrel 106. The wave of material propagates ahead of the expansion mandrel 106 during radial expansion. It has generally been found that thick-walled bushings, for example, are more susceptible to forming a larger, more extended, and/or more protruded second upset region 230 than thin-walled bushings. The mandrel forces during expansion of thick-walled bushings tend to be relatively large to ensure an adequate interference fit between the thick-walled structural member 204 and the workpiece 202.

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.

FIG. 5 shows an installation 300 comprising a first workpiece 302, a structural member 304, and a second workpiece 336, according to one illustrated embodiment. The second workpiece 336 should be in flush contact with the first workpiece 302, but the second upset region 330 causes the second workpiece 336 to be separated from the first workpiece 302 by a gap or space 338. In the illustrated embodiment, the direction of mandrel travel is indicated by the arrow 339. It is appreciated that the grip length of the structural member 304 could be shortened to keep the upset region 330 from becoming over-flush with respect to the abutting surface 341 of the workpiece 302. However, shortening the grip length of the structural member 304 may adversely reduce the bearing area between the structural member 304 and the workpiece 302, thus leading to yet another undesirable condition.

FIG. 6A shows the installation 300 of FIG. 5 further comprising a fastener 340 inserted through the structural member 304, the first workpiece 302, and the second workpiece 336, respectively. A threaded end 341 of the fastener 340 receives a threaded nut 342. Optionally, a washer 344 may be placed between the nut 342 and the second workpiece 336 to protect the surface of the second workpiece. As the fastener 340 and nut 342 combination is torqued down, the first upset region 326 causes the clamp-up forces in the installation 300 to proceed approximately along a load path line 348 (shown in phantom line). It is typically highly advantageous in a structural joint to have the fastener clamp-up forces be distributed along the radial flange 224 (FIG. 2), the first workpiece 302, and the second workpiece 336. The illustrated upset regions 326, 330 generate an undesirable load path during fastener clamp-up.

FIG. 6B shows a structural joint 400 comprising a fastener 440 inserted through a first structural member 404 and a second structural member 405, which are located in a first workpiece 402 and a second workpiece 436, respectively. A threaded end 441 of the fastener 440 receives a nut 442. Optionally, a washer 444 may be positioned between the nut 442 and the second workpiece 436. As the first and second structural members 404, 405 are radially expanded by an expansion mandrel being pulled in a direction 407, at least one upset region 426 is formed on the flanged-side of the first structural member 404. In addition and as shown in the illustrated embodiment, the strain energy from the radial-expansion process can cause a flange 451 to move away from the workpiece 402.

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.

FIG. 7 shows a structural member 500 in a pre-radially-expanded state. The structural member 500 can be configured to reduce, limit, or substantially eliminate unwanted protruding of deformed material formed during installation.

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 (FIG. 1) can travel through the passage 506 of the structural member 500 during radial expansion of the structural member 500.

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 (FIG. 8) expected to form on the expansion mandrel exit side 528 of the structural member 500. In some embodiments, a substantial portion of the upset material 530 is received in the recess 520. The recess 520 can become smaller as the amount of upset material 530 is increased. In some embodiments, the upset material 530 does not extend beyond a surface 524, as shown in FIG. 8. The depth 522, cross-sectional area, and configuration of the recess 520 can be selected based on the amount and location of upset material 530. The surface 524 is the surface located farthest from the first surface 508. The outer diameter of the recess 520 is less than the outer perimeter that corresponds to the outer surface 502. The surface 524 may be an approximately flat surface surrounding the recess 520. The size of the surface 524 can be a function of the wall thickness of the structural member 400, as well as other design parameters, according to one embodiment.

FIG. 8 shows the structural member 500 in a radially-expanded state after the expansion mandrel 106 has passed through the passage 506 of the structural member 500 to radially expand the structural member 500 into the workpiece 102. The recess 520 accommodates the mandrel exit upset material 530. The mandrel exit upset material 530 is the same material as the material of the structural member 500, but is shown with different cross-hatching for the sake of clarity.

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 (FIG. 8) that forms when the expansion mandrel 106 (FIG. 1) enters the opening 506 and begins to radially expand the structural member 500.

FIG. 9 shows a structural member 600 in a pre-radially-expanded state. The structural member 600 can include an outer surface 602 and an inner surface 604 that forms a passage 606 through the structural member 600. In addition, the structural member 600 includes a radial flange 608, a first surface 610, and a second surface 612. The first surface 610 is substantially perpendicular to a longitudinal axis 611 of the structural member 600. The arrow 613 represents the direction the mandrel 106 (FIG. 1) passes through the passage 606 when the structural member 600 is radially expanded.

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 (FIG. 10) that may be deformed as the expansion mandrel 106 exits the structural member 600 during the radial-expansion process. The recess 622 includes a depth 624 which, in combination with the area of at least the first region 614, provides a volume sized to receive the mandrel exit upset material 630 (FIG. 10) expected to form on the expansion mandrel exit side of the structural member 600 without permitting the material 630 to extend beyond a portion 634 (FIG. 10) adjacent to a surface 626. In one embodiment, the surface 626 is a flat surface located longitudinally farthest from the first surface 610 and is also substantially parallel to the first surface 610. Optionally, the structural member 600 may include an entry recess 628 proximate a countersink surface or an arcuate surface 529.

FIG. 10 shows the structural member 600 in a radially-expanded state after the expansion mandrel 106 has passed through the opening 606 of the structural member 600 to radially expand the structural member 600 into the workpiece 102. The recess 622 accommodates the mandrel exit upset material 630. The mandrel exit upset material 630 is the same as the material of the structural member 600, but is shown with different cross-hatching for the sake of clarity.

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.