U.S. patent application number 10/612670 was filed with the patent office on 2004-05-20 for machined structural assemblies formed from preforms.
This patent application is currently assigned to The Boeing Company. Invention is credited to Halley, Jeremiah E., Slattery, Kevin T..
Application Number | 20040094604 10/612670 |
Document ID | / |
Family ID | 27787864 |
Filed Date | 2004-05-20 |
United States Patent
Application |
20040094604 |
Kind Code |
A1 |
Halley, Jeremiah E. ; et
al. |
May 20, 2004 |
Machined structural assemblies formed from preforms
Abstract
A method of constructing a preform for use in forming a machined
structural assembly is provided. The method includes determining
the dimensions of the machined structural assembly. First and
second structural members are selected based on the predetermined
dimensions of the machined structural assembly. The first
structural member is positioned adjacent the second structural
member so as to define at least two contact surfaces. The contact
surfaces of the first and second structural members are friction
welded to construct the preform such that the preform has
dimensions approximating the dimensions of the machined structural
assembly to thereby reduce material waste when forming the machined
structural assembly. A machined structural assembly having
predetermined dimensions is formed from the preform by machining
away excess material.
Inventors: |
Halley, Jeremiah E.; (St.
Louis, MO) ; Slattery, Kevin T.; (St. Charles,
MO) |
Correspondence
Address: |
ALSTON & BIRD LLP
BANK OF AMERICA PLAZA
101 SOUTH TRYON STREET, SUITE 4000
CHARLOTTE
NC
28280-4000
US
|
Assignee: |
The Boeing Company
|
Family ID: |
27787864 |
Appl. No.: |
10/612670 |
Filed: |
July 2, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10612670 |
Jul 2, 2003 |
|
|
|
10092675 |
Mar 7, 2002 |
|
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Current U.S.
Class: |
228/112.1 ;
228/159 |
Current CPC
Class: |
B23K 20/129
20130101 |
Class at
Publication: |
228/112.1 ;
228/159 |
International
Class: |
B23K 020/12 |
Claims
That which is claimed:
1. A machined structural assembly prepared by the process
comprising the steps of: determining the dimensions of the machined
structural assembly; selecting first and second structural members
based on the dimensions of the machined structural assembly;
friction welding the first and second structural members together
to construct a preform such that the preform has dimensions
approximating the dimensions of the machined structural assembly;
and thereafter, machining the preform to remove excess material
from the preform to form the machined structural assembly having
the predetermined dimensions.
2. A machined structural assembly according to claim 1 wherein said
friction welding step comprises: moving at least one of the first
and second structural members relative to the other; concurrently
with said moving step, urging at least one of the first and second
structural members toward the other to thereby generate frictional
heat about the at least two contact surfaces; terminating said
moving step; and concurrently with said terminating step, urging at
least one of the first and second structural members toward the
other as the at least two contact surfaces cool to thereby form a
friction weld joint at least partially between the at least two
contact surfaces.
3. A machined structural assembly according to claim 2 wherein said
moving step comprises oscillating at least one of the first and
second structural members relative to the other structural
member.
4. A machined structural assembly according to claim 2 wherein said
moving step comprises simultaneously moving the first and second
structural members in opposing directions, wherein the opposing
directions are parallel to the at least two contact surfaces.
5. A machined structural assembly according to claim 1 further
comprising forming a relief groove proximate to at least one of the
at least two contact surfaces before said positioning step.
6. A machined structural assembly according to claim 1 further
comprising cleaning at least one of the at least two contact
surfaces prior to said positioning step.
7. A machined structural assembly according to claim 1 wherein said
machining step comprises machining the friction weld joint joining
the first and second structural assembly.
8. A machined structural assembly according to claim 1 further
comprising processing at least one of the first and second
structural members before said friction welding step, wherein said
processing step comprises a material treatment selected from the
group consisting of heat treating, aging, quenching, stretching,
annealing, and solution annealing.
9. A machined structural assembly according to claim 1 further
comprising processing the preform before said machining step,
wherein said processing step comprises a material treatment
selected from the group consisting of heat treating, aging,
quenching, stretching, annealing, and solution annealing.
10. A machined structural assembly according to claim 1 further
comprising friction welding a third structural member to at least
one of the first and second structural members.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. application Ser.
No. 10/092,675, filed Mar. 7, 2002, which is hereby incorporated
herein in its entirety by reference.
FIELD OF THE INVENTION
[0002] This invention relates to friction welding and, more
specifically, to friction welding of preforms for use in forming
machined structural assemblies.
BACKGROUND OF THE INVENTION
[0003] Hogout machining generally refers to a process of forming a
structural assembly by removing excess material from a piece of
stock material, such as a plate or block, to arrive at the desired
configuration and dimensions for the assembly. Oftentimes when
practicing hogout machining, the dimensions and configuration of
the structural assembly are such that appreciable amounts of
material must be removed. Thus, while hogout machining provides a
method for forming structural assemblies having complex
configurations, hogout machining can be costly due to the
relatively large amount of excess material or scrap that typically
must be removed and because the machining process can be time
consuming and labor intensive. Hogout machining also can cause
excessive wear on the cutting machine and tools, which can result
in machine downtime and/or tool breakage that in turn can adversely
affect the tolerances of the finished assembly. In addition, the
availability of stock sizes of material limits the overall
dimensions of a structural assembly formed by hogout machining.
[0004] In seeking to reduce material waste and machining times,
other methods are used for forming the stock material to be used in
machining a structural assembly. For example, one method is
machined forging, which refers to the process of machining a part
from a piece of forged stock material that approximates the final
configuration. When machined forging is used, the amount of
machining can be reduced because the forged stock material can be
hand or die forged to dimensions that more closely approximate the
desired dimensions of the finished assembly. However, the
production of forged stock material can be time consuming and labor
intensive and, in the case of die forgings, can require the
production of costly forging dies. Die forgings can require
ultrasonic inspection, as the forging process can cause internal
cracks or other defects. Additionally, both die and hand forging
can cause residual stresses in the forged stock material that can
remain in the finished structural assembly. Residual stresses can
necessitate slower cutting speeds when hogout machining and can
adversely affect the material properties and tolerances of the
finished assembly.
[0005] Thus, there remains a need for improved methods of forming
stock material or "preforms" for use in forming machined structural
assemblies. Such preforms should approximate the desired dimensions
and configuration of the structural assembly to reduce the
machining time required during machining, as well as reduce waste
material. The desired dimensions and configuration of the
structural assembly should not be limited by the sizes of available
stock materials. In addition, such preforms should have negligible
residual stresses so that the finished machined assembly will have
consistent material properties and dimensional tolerances.
SUMMARY OF THE INVENTION
[0006] The present invention provides an improved preform, machined
structural assembly, and associated methods of forming the same. In
one embodiment, the present invention provides a preform for use in
forming a machined structural assembly of predetermined dimensions.
The preform includes a first structural member defining at least
one contact surface and a second structural member defining at
least one contact surface that corresponds to the contact surface
of the first structural member. A friction weld joint joins the
contact surfaces of the first and second structural members to
thereby form a preform having dimensions approximating the
dimensions of the final machined structural assembly so as to
reduce material waste and machining time when forming the assembly.
In one embodiment, the first and second structural members comprise
aluminum, aluminum alloys, titanium, titanium alloys, nickel-based,
steel, copper-based alloys, or beryllium-based alloys. In another
embodiment, the first and second structural members comprise
dissimilar materials. In still another embodiment, the preform
comprises a third structural member friction welded to at least one
of the first and second structural members.
[0007] The present invention also provides a method for
constructing a preform for use in forming a machined structural
assembly. The method includes determining the desired dimensions of
the finished machined structural assembly. Based on the dimensions
of the structural assembly, first and second structural members are
selected. The first structural member is then positioned adjacent
to the second structural member to define at least two contact
surfaces therebetween. The first and second structural members are
then friction welded together to form a preform having dimensions
that approximate the dimensions of the machined structural
assembly. In one embodiment, the method comprises forming a relief
groove proximate to at least one of the at least two contact
surfaces prior to the positioning step. In another embodiment, the
method includes cleaning one or both of the contact surfaces before
the positioning step. In still another embodiment, at least one of
the first and second structural members is processed before
friction welding through a material treatment, such as heat
treating, aging, quenching, stretching, annealing, or solution
annealing. In yet another embodiment of the present invention, the
method of forming a preform further comprises friction welding
additional structural members to at least one of the first or
second structural members. For example, a third structural member
may be friction welded to either of the first or second structural
members or to both structural members.
[0008] According to one embodiment of the present invention, the
friction welding step comprises moving at least one of the first
and second structural members relative to the other structural
member while concurrently urging at least one of the structural
members toward the other to generate frictional heat about the
contact surfaces. The moving step is then terminated, and
concurrently therewith, at least one of the first and second
structural members is urged toward the other as the contact
surfaces cool to thereby form a friction weld joint at least
partially between the contact surfaces. In one embodiment, the
moving step comprises oscillating at least one of the first and
second structural members relative to the other. In another
embodiment, the moving step comprises moving the first and second
structural members in opposing directions, wherein the opposing
directions are parallel to the at least two contact surfaces of the
first and second structural members forming the preform.
[0009] The present invention also provides a machined structural
assembly and a method of forming a machined structural assembly.
The method includes determining the dimensions of the machined
structural assembly. Based on the dimensions of the machined
structural assembly, a preform is constructed as described above.
The preform is machined to remove excess material from the preform
to form the machined structural assembly having the predetermined
dimensions. In one embodiment, the preform is processed before the
machining step through a material treatment, such as a heat
treating, aging, quenching, stretching, annealing or solution
annealing. In another embodiment, the machining step comprises
machining at least a portion of the friction weld joint joining the
first and second structural members.
[0010] Accordingly, there is provided a preform for forming
machined structural assemblies having dimensions approximating the
dimensions of the machined structural assembly to thereby reduce
material waste and machining time. The dimensions of the machined
structural assembly are not limited by the sizes of stock
materials. Advantageously, the friction weld between the structural
members provides a strong material bond with the formation of
negligible residual stresses. Thus, the preform of the present
invention facilitates the efficient production of structural
assemblies having consistent material properties and dimensional
tolerances.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] 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:
[0012] FIG. 1 is an elevation view illustrating the first and
second structural members being positioned before friction welding,
according to one embodiment of the present invention;
[0013] FIG. 2 is an elevation view illustrating a preform
constructed from the first and second structural members of FIG.
1;
[0014] FIG. 3 is a perspective view illustrating the formation of
the preform of FIG. 2; FIG. 4 is an elevation view illustrating the
material to be removed from the preform of FIG. 2 to form a
machined structural assembly;
[0015] FIG. 4A is an elevation view illustrating a conventional
block of stock material used to form a hogout structural assembly,
as is known in the art;
[0016] FIG. 5 is an elevation view illustrating the machined
structural assembly formed from the preform of FIG. 2;
[0017] FIG. 6 is an elevation view illustrating first, second, and
third structural members being positioned before friction welding,
according to another embodiment of the present invention;
[0018] FIG. 7 is an elevation view illustrating a preform
constructed from the first, second and third structural members of
FIG. 6;
[0019] FIG. 8 is an elevation view illustrating the material to be
removed from the preform of FIG. 7 to form a machined structural
assembly;
[0020] FIG. 8A is an elevation view illustrating a conventional
block of stock material used to form a hogout structural assembly,
as is known in the art;
[0021] FIG. 9 is an elevation view illustrating the machined
structural assembly formed from the preform of FIG. 7;
[0022] FIG. 10 is an elevation view illustrating first and second
structural members being positioned before friction welding with
one of the structural members having two relief grooves, according
to another embodiment of the present invention;
[0023] FIG. 11 is an elevation view illustrating the preform
constructed from the first and second structural members of FIG.
10;
[0024] FIG. 12 is an elevation view illustrating the material to be
removed from the preform of FIG. 11 to form a machined structural
assembly;
[0025] FIG. 12A is an elevation view illustrating a conventional
block of stock material used to form a hogout structural assembly,
as is known in the art;
[0026] FIG. 13 is an elevation view illustrating the machined
structural assembly formed from the preform of FIG. 11;
[0027] FIG. 14 is a flow chart illustrating a method for forming a
preform, according to one embodiment of the present invention;
[0028] FIG. 14A is a flow chart further illustrating the method of
FIG. 14; and
[0029] FIG. 15 is a flow chart illustrating a method for forming a
machined structural assembly, according to one embodiment of the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0030] 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.
[0031] Referring to the drawings and, in particular, to FIGS. 1, 2,
3, 4, and 5, there is illustrated the formation of a machined
structural assembly 6 from a preform, according to one embodiment
of the present invention. As illustrated in FIGS. 1, 2, and 3, the
preform 1 is formed from a first structural member 2 and a second
structural member 3. In other embodiments, as illustrated in FIGS.
6 and 7, the preform 1 is formed from three or more structural
members 2, 3, 8. The number of structural members used to construct
the preform 1 will depend on the dimensions and configuration of
the machined structural assembly 6, which in turn depends on the
specifications and design requirements of the assembly.
[0032] The configuration and material composition of the structural
members 2, 3, 8 also will vary depending on the specifications and
design requirements of the assembly. The first and second
structural members 2, 3 are illustrated in FIG. 1 as plates having
rectangular cross-sections. However, the structural members 2, 3, 8
can be formed in other configurations, including, for purposes of
example only and not limitation, blocks having rectangular or
square cross-sections, tubes and cylinders having circular or oval
cross-sections, or channels having L-shaped, C-shaped, U-shaped,
T-shaped or V-shaped cross-sections. The structural members 2, 3
can also have irregular geometric configurations. The structural
members 2, 3 can be formed from a variety of fabricating processes,
as is known in the art, including milling, casting, or forging,
provided that the forging process does not create appreciable
residual stresses. The structural members 2, 3 preferably are
formed from materials having high strength to weight ratios and
good corrosion resistance. For purposes of example only and not
limitation, the structural members can comprise aluminum, aluminum
alloys, titanium, titanium alloys, nickel-based, steel,
copper-based alloys, or beryllium-based alloys. According to one
embodiment, the structural members 2, 3, 8 are formed from the same
or similar materials. In another embodiment, one or more of the
structural members 2, 3, 8 are formed from dissimilar materials
provided that the materials will create a strong material bond when
joined by friction welding.
[0033] In addition to the material composition and properties of
the structural members 2, 3, 8, the selection of the structural
members is based on the desired dimensions of the machined
structural assembly 6 that is to be formed. More specifically, the
desired dimensions of the machined structural assembly 6 are
determined and then the structural members 2, 3, 8 are selected so
that the resulting preform 1 will closely approximate the
predetermined dimensions and configuration of the finished
assembly. Advantageously, by constructing preforms having
dimensions and configurations closely or substantially
approximating the predetermined dimensions and configuration of the
corresponding machined structural assembly 6, a reduction in
machining time and material waste can be achieved, thus making
these assemblies more economical to produce. One measure of wasted
material in a machining process is the buy:fly ratio, which
compares the mass of the block of material that is to be machined
to the mass of the finished machined component. Hogout machining
typically results in a buy:fly ratio of between about 10:1 and
50:1. Thus, between about 90% and 98% of the mass of a conventional
block of stock material is typically removed when hogout machining
is used. Buy:fly ratios for machined structural assemblies formed
according to the present invention vary, but are typically between
about 2:1 and 6:1.
[0034] As illustrated in FIG. 1, the preform 1 is formed by
positioning the first and second structural members 2, 3 adjacent
to one another so that the first structural member 2 defines at
least one contact surface 4 and the second structural member 3
defines at least one contact surface 5 corresponding to the contact
surface 4 of the first structural member 2. The corresponding
contact surfaces 4, 5 complement each other so that when the first
and second structural members 2, 3 are brought together, the
contact surface 4 of the first structural member 2 and the contact
surface 5 of the second structural member 3 form an interface
substantially along the entire area of the contact surfaces. The
structural members can then be secured to a support, such as a
backing plate or table, using clamps, bolts, tack welding, tooling
or the like, or to a device for imparting movement, such as a
computer numeric control (CNC) machine or similar device, as is
known in the art.
[0035] Once the structural members 2, 3 are positioned opposite one
another, the first and second structural members are then friction
welded to form a weld joint about the interface between the
structural members. Friction welding is accomplished by moving at
least one of the structural members 2, 3 relative to the other
structural member 2, 3, or, alternatively, moving both the
structural members at the same time. As illustrated in FIG. 3, the
first structural member 2 is held fixed to a support member 15,
while the second structural member 3 is moved by a machine or
device 16 in a linear oscillatory pattern relative to the first
structural member, as indicated by the arrows 16a. In another
embodiment (not shown), the first and second structural members 2,
3 are each moved linearly in a direction opposite to the direction
of motion of the other structural member. The direction of motion
of the structural member or members can vary, but preferably is
generally parallel to the contact surfaces 4, 5. In other
embodiments, the motion of the first and second structural members
2, 3 can be oscillatory or non-oscillatory and can have a
rotational, elliptical or orbital pattern.
[0036] At the same time one or both of the structural members 2, 3
are being moved, the structural members are urged together by
applying force to the second structural member 3 generally in the
direction of the first structural member 2 and applying a reactive
force to the first structural member 2 generally in the direction
of the second structural member 3. For example, as illustrated in
FIG. 3, the force applied to the second structural member 3 can be
applied by the machine or device 16 used to impart the motion to
the second structural member, as indicated by the arrow 16b,
whereas the reactive force can be applied by the support member 15.
In another embodiment (not shown), the forces applied to the first
and second structural members 2, 3 are each generated from a
machine or device used to impart the motion to the corresponding
member. As the structural members 2, 3 are urged together, a
compressive force is established between the contact surfaces 4, 5
along the interface defined between the structural members. The
compressive force is typically great enough to result in a pressure
between the structural members 2, 3 of at least about 1000 pounds
per square inch. The motion of at least one of the structural
members 2, 3 is continued while the compressive force is maintained
resulting in friction between the structural members 2, 3. The
friction between the structural members 2, 3 results in heating of
the respective contact surfaces 4, 5, which causes plasticised
regions to form about the contact surfaces. Once sufficient
plasticization has occurred along the interface defined by the
contact surfaces 4, 5, the motion between the structural members 2,
3 is then terminated. The compressive force between the structural
members 2, 3 is maintained by urging the structural members
together as the contact surfaces 4, 5 cool to thereby form a
friction weld joint 14 about the interface.
[0037] Referring to FIGS. 6 and 7, there is illustrated a preform 1
formed from first, second and third structural members 2, 3, 8. The
second and third structural members 3, 8 are joined to opposite
sides of the first structural member 2. In other embodiments (not
shown), the third structural member 8 can be joined to the second
structural member 3 or both the first and second structural members
2, 3, depending on the desired dimensions and configuration of the
machined structural assembly 6. When constructing preforms 1 having
three or more structural members 2, 3, 8, the friction weld joints
14 joining the respective structural members can be formed at the
same time or by first joining one pair of structural members and
then joining additional members thereto.
[0038] According to one embodiment of the present invention, the
structural members 2, 3, 8 are processed before friction welding.
For example, the contact surfaces 4, 4a, 5, 9 of the structural
members 2, 3, 8 are cleaned using a solvent or abrasive cleaner to
remove any oxidation or surface defects so that a strong material
bond can be obtained by friction welding. In other embodiments, one
or more of the structural members 2, 3, 8 can undergo a material
treatment, such as heat treatment, aging, quenching, stretching,
annealing, or solution annealing, to obtain desired mechanical or
chemical properties, as is known in the art.
[0039] In another embodiment of the present invention, as
illustrated in FIGS. 10, 11, and 12, one or more relief grooves 7
are formed in at least one of the structural members 2, 3 proximate
to the corresponding contact surface or surfaces 4, 5. The relief
grooves 7 can be formed using cutting or routing equipment, as is
known in the art. The relief grooves 7 illustrated in FIG. 10 are
straight grooves disposed in the first structural member 2 parallel
and proximate to the contact surface 4 defined by the first
structural member 2. The position, dimensions and configuration of
the relief grooves 7 can vary depending on the particular
application of the machined structural assembly 6. The relief
grooves 7 allow plasticized material from both the first and second
structural members 2, 3 to flow, facilitating the formation for a
strong weld joint between the structural members 2, 3.
[0040] As illustrated in FIGS. 4 and 5, FIGS. 8 and 9, and FIGS. 12
and 13, once the preform 1 is formed a predetermined amount of
excess material 11 can be machined from the preform to form the
machined structural assembly 6. The machining process can be
performed by any known means, including using a manual or
computer-guided machining device, such as a CNC machine. As
illustrated in FIGS. 4 and 5 and FIGS. 12 and 13, excess material
11 is removed from the entire exposed surface of the second
structural member 3, but only a portion of the exposed surface of
the first structural member 2. As illustrated in FIGS. 8 and 9,
substantially all of the entire exposed surface of the first,
second, and third structural members 2, 3, 8 is removed.
Advantageously, because the preforms 1 closely or substantially
approximate the predetermined dimensions and configuration of the
corresponding machined structural assembly 6, the amount of
machining is relatively small compared to, for example, the amount
of machining that would be required to machine hogout structural
assemblies from solid rectangular blocks of material 12, such as
those illustrated in FIGS. 4A, 8A and 12A.
[0041] As illustrated in FIGS. 10, 11, and 12, friction welding
structural members 2, 3 defining one or more relief grooves 7 can
result in the formation of extraneous material deposits in the form
of flash or spars 10. The flash 10 results from extrusion of
plasticised material during friction welding due to the compressive
force between the structural members 2, 3 as the members are urged
together. The high compressive force causes some of the plasticised
material to be extruded from the region between the contact
surfaces 4, 5, which can collect, forming a bead or multiple
isolated deposits adjacent to each side of the weld joint 14. As
illustrated in FIGS. 12 and 13, the flash 10 is typically removed
when machining the preform 1 to form the machined structural
assembly 6.
[0042] Referring to FIG. 14, there is illustrated the operations
performed in forming a preform, according to one embodiment of the
present invention. The method includes determining the desired
dimensions of the machined structural assembly. See Block 20. Based
on the dimensions of the structural assembly, first and second
structural members are selected. See Block 21. In one embodiment,
the method comprises forming a relief groove proximate to at least
one of the at least two contact surfaces prior to the positioning
step. See Block 22. In another embodiment, the method includes
cleaning one or both of the contact surfaces before the positioning
step. See Block 23. In still another embodiment, at least one of
the first and second structural members is processed before
friction welding through a material treatment, such as heat
treating, aging, quenching, stretching, annealing, or solution
annealing. See Block 24. The first structural member is then
positioned adjacent to the second structural member to define at
least two contact surfaces therebetween. See Block 25. The first
and second structural members are then friction welded together to
form a preform having dimensions that approximate the dimensions of
the machined structural assembly. See Block 26.
[0043] Referring to FIG. 14A, there is illustrated the steps in
friction welding the structural members of FIG. 14, according to
one embodiment of the present invention. The friction welding step
includes moving at least one of the first and second structural
members relative to the other structural member. See Block 28. In
one embodiment, the moving step comprises oscillating at least one
of the first and second structural members relative to the other.
See Block 29. In another embodiment, the moving step comprises
moving the first and second structural members in opposing
directions, wherein the opposing directions are parallel to the at
least two contact surfaces of the first and second structural
members forming the preform. See Block 30. Concurrently with the
moving step, at least one of the structural members is urged toward
the other to generate frictional heat about the contact surfaces.
See Block 31. The moving step is then terminated. See Block 32.
Concurrently with the termination step, at least one of the first
and second structural members is urged toward the other as the
contact surfaces cool to thereby form a friction weld joint at
least partially between the contact surfaces. See Block 33. In one
embodiment, a third structural member is friction welded to at
least one of the first and second structural members. See Block
27.
[0044] Referring to FIG. 15, there is illustrated the operations
performed in forming a machined structural assembly, according to
one embodiment of the present invention. A preform is constructed
as described above in connection with FIGS. 14 and 14A. The preform
is machined to remove excess material from the preform to form the
machined structural assembly having the predetermined dimensions.
See Block 42. In one embodiment, the preform is processed before
the machining step through a material treatment, such as a heat
treating, aging, quenching, stretching, annealing or solution
annealing. See Block 41. In another embodiment, the machining step
comprises machining at least a portion of the friction weld joint
joining the first and second structural members. See Block 43.
[0045] Accordingly, there is provided a preform for forming
machined structural assemblies having dimensions approximating the
dimensions of the machined structural assembly to thereby reduce
material waste and machining time. Advantageously, the preform of
the present invention facilitates the efficient production of
machined structural assemblies having consistent material
properties and dimensional tolerances. 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.
* * * * *