Title: Preforms for forming machined structural assemblies
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.
Patent Number: 6,910,616 Issued on 06/28/2005 to Halley, et al.
| Inventors:
|
Halley; Jeremiah E. (St. Louis, MO);
Slattery; Kevin T. (St. Charles, MO)
|
| Assignee:
|
The Boeing Company (Chicago, IL)
|
| Appl. No.:
|
092675 |
| Filed:
|
March 7, 2002 |
| Current U.S. Class: |
228/112.1; 228/2.1; 228/113; 228/114.5 |
| Intern'l Class: |
B23K 020/12; B23K031/02 |
| Field of Search: |
228/1121,113,114,114.5,21
|
References Cited [Referenced By]
U.S. Patent Documents
| 3570740 | Mar., 1971 | Stamm.
| |
| 3831459 | Aug., 1974 | Satzler et al.
| |
| 3841201 | Oct., 1974 | Kiwalle et al.
| |
| 4087038 | May., 1978 | Yagi.
| |
| 4945019 | Jul., 1990 | Bowen et al.
| |
| 5168841 | Dec., 1992 | Suzuki et al.
| |
| 5248077 | Sep., 1993 | Rhoades et al.
| |
| 5366344 | Nov., 1994 | Gillbanks et al.
| |
| 5425821 | Jun., 1995 | Kurup et al.
| |
| 5469617 | Nov., 1995 | Thomas et al.
| |
| 5470524 | Nov., 1995 | Krueger et al.
| |
| 5551623 | Sep., 1996 | Collot et al.
| |
| RE35664 | Nov., 1997 | Searle.
| |
| 5682677 | Nov., 1997 | Mahoney.
| |
| 5697544 | Dec., 1997 | Wykes.
| |
| 5718366 | Feb., 1998 | Colligan.
| |
| 5769306 | Jun., 1998 | Colligan.
| |
| 5794835 | Aug., 1998 | Colligan et al.
| |
| 5865364 | Feb., 1999 | Trask et al.
| |
| 5971247 | Oct., 1999 | Gentry.
| |
| 6022194 | Feb., 2000 | Amos et al.
| |
| 6050474 | Apr., 2000 | Aota et al.
| |
| 6068178 | May., 2000 | Michisaka.
| |
| 6070784 | Jun., 2000 | Holt et al.
| |
| 6079609 | Jun., 2000 | Fochtman.
| |
| 6095402 | Aug., 2000 | Brownell et al.
| |
| 6106233 | Aug., 2000 | Walker et al.
| |
| 6168066 | Jan., 2001 | Arbegast.
| |
| 6173880 | Jan., 2001 | Ding et al.
| |
| 6219916 | Apr., 2001 | Walker et al.
| |
| 6244492 | Jun., 2001 | Kupetz et al.
| |
| 6295893 | Oct., 2001 | Ogawa et al.
| |
| 6412175 | Jul., 2002 | Labombard.
| |
| 6478545 | Nov., 2002 | Crall et al.
| |
| 6524072 | Feb., 2003 | Brownell et al.
| |
| 6669447 | Dec., 2003 | Norris et al.
| |
| 6779708 | Aug., 2004 | Slattery.
| |
| 2002/0125297 | Sep., 2002 | Stol et al.
| |
| Foreign Patent Documents |
| 1048390 | Nov., 2000 | EP.
| |
| 1057572 | Dec., 2000 | EP.
| |
Other References
Website of TWI Technology at http://www.twi.co.uk/techfile/tffricli.html; 1 page
dated Dec. 8, 2000.
Website of TWI Technology at http://www.twi.co.uk/connect/may00/c1063.html; 3
pages dated Dec. 8, 2000.
Website of University of Southhampton, Faculty of Mathematical Studies at http://www.maths.soton.ac.uk/esgi98/problems/rolls.html;
1 page dated Dec. 8, 2000.
Website of MTS Systems Corporation at http://www.mts.com/aesd/AdvanMan.htm; 2
pages dated Dec. 8, 2000 (Copyright 2000).
Website of MTS Systems Corporation at http://www.mts.com/aesd/aerospace engine.htm;
1 page dated Nov. 13, 2000 (Copyright 2000).
Website of Inside Communications Limited at http://www.insidecom.co.uk/pwe/editorial/pwe352.htm;
2 pages dated Nov. 13, 2000.
Advanced Materials & Processes 2/91; Tech Spotlight, Linear friction welding
joins noncircular sections; p. 47.
D. L. Hollar, Jr.; Resistance Seam Welding of Thin Copper Foils; Welding Journal;
Jun., 1993; pp. 37-40.
|
Primary Examiner: Edmondson; Lynne R.
Attorney, Agent or Firm: Alston & Bird LLP
Claims
1. A method of constructing a preform for use in forming a machined structural
assembly, comprising:
determining the dimensions of the machined structural assembly;
selecting first and second structural members bused on the dimensions of the
machined structural assembly, the structural members including excess material
such that at least one of the structural members is larger in at least one dimension
than the corresponding dimension of the machined structural assembly;
positioning the first structural member adjacent the second structural member
so as to define at least two contact surfaces therebetween; and
linear friction welding the at least two contact surfaces of die first and second
structural members to construct the preform such that the preform defines an elongate
friction weld joint and has dimensions approximating the dimensions of the machined
structural assembly to thereby reduce material waste and machining time when forming
the machined structural assembly,
wherein said selecting step comprises selecting structural members with a combined
mass of at least about twice the mass of the machined structural assembly.
2. A method 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 hear 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 method 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 method according to claim 2 wherein said moving step comprises simultaneously
moving the first and second structural members in opposing directions, wherein
the opposing directions arc parallel to the at least two contact surfaces.
5. A method according to claim 1 further comprising forming a relief groove proximate
to at least one of the at least two contact surfaces prior to said positioning step.
6. A method according to claim 1 further comprising cleaning at least one of
the at least two contact surfaces prior to said positioning step.
7. A method 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.
8. A method according to claim 1 further comprising friction welding a third
structural member to at least one of the first and second structural members.
9. A method of forming a machined structural assembly, comprising:
determining the dimensions of the machined structural assembly;
selecting first and second structural members based on the dimensions of the
machined structural assembly, the structural members including excess material
such that at least one of the structural members is larger in at least one dimension
than the corresponding dimension of the machined structural assembly;
positioning the first structural member adjacent the second structural member
so as to define at least two contact surfaces therebetween; and
linear friction welding the at least two contact surfaces of the first and second
structural members to construct a preform such that the preform defines an elongate
friction weld joint and has dimensions approximating the dimensions of the machined
structural assembly; and
thereafter, machining the preform to remove the excess material from the preform
including at least a portion of the elongate weld joint to form the machined structural
assembly defining the elongate friction weld joint and having the predetermined
dimensions, at least one of the structural members defining a machined surface
adjacent the elongate friction weld joint,
wherein said machining step comprises removing at least about one-half of the
mass of the preform such that the structural member has a mass of less than about
one-half of the preform.
10. A method according to claim 9 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.
11. A method according to claim 10 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.
12. A method according to claim 10 wherein said moving step comprises oscillating
at least one of the first and second structural members relative to the other structural member.
13. A method according to claim 9 further comprising forming a relief groove
proximate to at least one of the at least two contact surfaces before said positioning step.
14. A method according to claim 9 further comprising cleaning at least one of
the at least two contact surfaces prior to said positioning step.
15. A method according to claim 9 wherein said machining step comprises machining
at least a portion of the friction weld joint joining the first and second structural members.
16. A method according to claim 9 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.
17. A method according to claim 9 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.
18. A method according to claim 9 further comprising friction welding a third
structural member to at least one of the first and second structural members.
19. A method according to claim 9 wherein said machining step comprises machining
each of the structural members adjacent the elongate weld joint such that each
of the structural members defines a machined surface adjacent the elongate weld joint.
20. A method according to claim 1 wherein said selecting step comprises selecting
at least one of the structural members defining the excess material over an entire
exposed surface.
21. A method according to claim 1 wherein said determining step comprises determining
a curved contour of the structural member and wherein said selecting and linear
friction welding steps comprise selecting and welding the structural members as
rectangular blocks.
22. A method according to claim 9 wherein said machining step comprises removing
excess material from an entire exposed surface of at least one of the structural members.
23. A method according to claim 9 wherein said selecting and linear fiction welding
steps comprise selecting and welding the structural members as rectangular blocks
and wherein said machining step comprises machining at least one of the structural
members to define a curved contour.
Description
FIELD OF THE INVENTION
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
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.
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.
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
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.
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.
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.
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.
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
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:
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;
FIG. 2 is an elevation view illustrating a preform constructed from the first
and second structural members of FIG. 1;
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;
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;
FIG. 5 is an elevation view illustrating the machined structural assembly formed
from the preform of FIG. 2;
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;
FIG. 7 is an elevation view illustrating a preform constructed from the first,
second and third structural members of FIG. 6;
FIG. 8 is an elevation view illustrating the material to be removed from the
preform of FIG. 7 to form a machined structural assembly;
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;
FIG. 9 is an elevation view illustrating the machined structural assembly formed
from the preform of FIG. 7;
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;
FIG. 11 is an elevation view illustrating the preform constructed from the first
and second structural members of FIG. 10;
FIG. 12 is an elevation view illustrating the material to be removed from the
preform of FIG. 11 to form a machined structural assembly;
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;
FIG. 13 is an elevation view illustrating the machined structural assembly formed
from the preform of FIG. 11;
FIG. 14 is a flow chart illustrating a method for forming a preform, according
to one embodiment of the present invention;
FIG. 14A is a flow chart further illustrating the method of FIG. 14; and
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
The present invention now will be described more fully hereinafter with reference
to the accompanying drawings, in which preferred embodiments of the invention are
shown. This invention may, however, be embodied in many different forms and should
not be construed as limited to the embodiments set forth herein; rather, these
embodiments are provided so that this disclosure will be thorough and complete,
and will fully convey the scope of the invention to those skilled in the art. Like
numbers refer to like elements throughout.
Referring to the drawings and, in particular, to 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.
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.
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.
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.
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.
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 plasticized 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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
*
