U.S. patent application number 11/480970 was filed with the patent office on 2006-11-09 for load bearing member arrangement and method.
This patent application is currently assigned to CATERPILLAR INC.. Invention is credited to Brian R. Janes, Christy L. Lee, Dirk J. Schreuder, Charles F. Sieck.
Application Number | 20060251503 11/480970 |
Document ID | / |
Family ID | 21844227 |
Filed Date | 2006-11-09 |
United States Patent
Application |
20060251503 |
Kind Code |
A1 |
Janes; Brian R. ; et
al. |
November 9, 2006 |
Load bearing member arrangement and method
Abstract
In the design of load bearing members for use in work machines,
it is oftentimes beneficial to minimize the weight of such
structures which, in turn, may allow for increased payloads and
decreased cycle times of the work machine. A load bearing
arrangement for use with a work machine of the type having a
platform is provided. The load bearing arrangement comprises a
plurality of pieces connectable to form a member structured and
arranged for pivotable attachment to the platform. A weldment
connects at least two of the pieces where at least one weldment is
simulated for effects of heat on at least one of the pieces subject
to the weldment.
Inventors: |
Janes; Brian R.;
(Chillicothe, IL) ; Lee; Christy L.; (Eureka,
IL) ; Schreuder; Dirk J.; (Peoria, IL) ;
Sieck; Charles F.; (Dunlop, IL) |
Correspondence
Address: |
CATERPILLAR/FINNEGAN, HENDERSON, L.L.P.
901 New York Avenue, NW
WASHINGTON
DC
20001-4413
US
|
Assignee: |
CATERPILLAR INC.
|
Family ID: |
21844227 |
Appl. No.: |
11/480970 |
Filed: |
July 6, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10028580 |
Dec 20, 2001 |
|
|
|
11480970 |
Jul 6, 2006 |
|
|
|
Current U.S.
Class: |
414/687 |
Current CPC
Class: |
B23K 31/12 20130101;
E02F 3/38 20130101 |
Class at
Publication: |
414/687 |
International
Class: |
B66C 23/00 20060101
B66C023/00 |
Claims
1-14. (canceled)
15. A load bearing arrangement for use with a work machine of the
type having a platform, comprising: a plurality of pieces
connectable to form a load bearing member structured and arranged
for pivotable attachment to the platform; and a weldment connecting
at least two of said pieces, said weldment being simulated for
effects of heat on at least one of said pieces subject to said
weldment before said weldment is constructed.
16. The load bearing arrangement as set forth in claim 15 wherein
said effects are at least one of stress and deformation.
17. The load bearing arrangement as set forth in claim 15, further
comprising: an end attached to said load bearing member and
comprising a material having a first yield strength; an aperture
formed in said end and having an aperture wall; at least one
support member contained within said aperture adjacent to at least
a portion of said aperture wall; and said support member having a
second yield strength greater than said first yield strength.
18. The load bearing arrangement as set forth in claim 17 wherein
said support member comprises a substantially cylindrical structure
having a through opening.
19. The load bearing arrangement as set forth in claim 18 further
comprising a bearing received in said opening.
20. The load bearing arrangement as set forth in claim 18 wherein
said support member is laser welded to said end.
21. The load bearing arrangement as set forth in claim 15 wherein
said load bearing member comprises: at least one top plate; at
least one bottom plate; and at least one pair of spaced apart side
plates each attached to said top plate and said bottom plate.
22. The load bearing arrangement as set forth in claim 21 wherein
said top plate comprises at least one integral mounting
structure.
23. The load bearing arrangement as set forth in claim 21 further
comprising: a substantially cylindrical attachment structure
extending from at least one of said pair of side plates; and
wherein said at least one of said pair of side plates is attached
to said attachment structure.
24. The load bearing arrangement as set forth in claim 23 wherein:
said load bearing member has a transverse width; and said
attachment structure spans said transverse width.
25. The load bearing arrangement as set forth in claim 21 further
comprising at least one reinforcing structure attached to at least
one of said pair of side plates.
26. The load bearing arrangement as set forth in claim 25 wherein
said reinforcing structure comprises: a base portion; and a rib
portion extending from said base portion.
27. The load bearing arrangement as set forth in claim 25 wherein
said reinforcement structure is laser welded to said at least one
of said pair of side plates.
28. The load bearing arrangement as set forth in claim 15 wherein:
said load bearing member comprises a first side and a second side;
one of said first side or said second side comprises a plurality of
side plates; each said side plate having a centerline axis; and at
least two adjacent side plates, each having a different thickness,
on one of said first side or said second side are coupled together
such that said centerline axis of each said side plate are
colinear.
29. The load bearing arrangement as set forth in claim 15 further
comprising an attachment pivotally coupled to said member.
30. The load bearing arrangement as set forth in claim 29 wherein
said attachment comprises a bucket.
31-35. (canceled)
36. A method of manufacturing a load bearing member, comprising a
plurality of pieces, for use with a work machine, comprising the
steps of: forming the pieces; connecting at least two of the pieces
by a weldment; and determining the effects of heat caused by the
weldment on at least one of said pieces subject to said
weldment.
37. The method as set forth in claim 36 wherein said forming step
is a performed by a thermal cutting process.
38. The method as set forth in claim 37 wherein said thermal
cutting process is laser cutting.
39. The method as set forth in claim 36 wherein forming step
includes a simulation step of simulating distortions of the pieces
caused by said thermal cutting process.
40. The method as set forth in claim 36 wherein said welding
process is a robotic process.
41. The method as set forth in claim 36 wherein said determining
step includes the steps of: determining a model of a geometry of
the material; defining a set of coordinates of elements and nodes
of the geometry model for a finite element analysis mesh;
delivering the finite element analysis mesh coordinates to a
thermal analysis model, the thermal analysis model including an
analytical solution model and a finite element analysis model;
determining a thermal analysis of the welding process as a function
of at least one of the analytical solution model and the finite
element analysis model, the analytical solution model being adapted
to provide a thermal history of the welding process for a global
distortion analysis, and the finite element analysis model being
adapted to provide a thermal history of the welding process for a
detailed residual stress analysis; delivering the thermal history
of the welding process to a structural analysis model; and
providing a structural analysis of the welding process as a
function of the thermal history.
42. The method as set forth in claim 36 wherein said determining
step includes the steps of: determining a history annihilation
model of a material being welded; determining a strain hardening
model of the material being welded; determining a three-dimensional
virtual elements detection model of the material being welded; and
incorporating the above models into a constitutive model for the
welding simulation.
43. The method as set forth in claim 36 wherein said determining
step occurs during the creation of the weldment.
44. The method as set forth in claim 36 wherein said determining
step occurs prior to the creation of the weldment.
45. The method as set forth in claim 36 wherein said effects are at
least one of stress and deformation.
46. The method as set forth in claim 36 further comprising the step
of modifying said connecting step to minimize the effects of the
heat.
47-48. (canceled)
Description
TECHNICAL FIELD
[0001] This invention relates to a load bearing member arrangement
and method and, more specifically, to such a load bearing member
and method thereof in which weld simulation, material preparation,
and structural changes to the load bearing members all contribute
in producing a load bearing member of reduces weight while not
sacrificing the strength of such members.
BACKGROUND
[0002] Load bearing members such as booms, sticks, crane booms and
so forth typically must support loads which may produce a resultant
load acting transversely across the member. Improvements in
manufacturing processes such as the welding process allow for an
improvement in the ability of the member to withstand such loads.
It has been shown that fatigue strength, particularly at weld
locations, is the limiting design factor when designing these types
of structures. It is generally accepted that welding induces high
tensile residual stresses in the local weldment region resulting in
the presence on a microscopic level of small sharp discontinuities
along the weld toe. These discontinuities, in turn, act as crack
propagators, especially when the load bearing member is subjected
to cyclic loading conditions. These improvements in the
manufacturing processes, in turn, allow for use of thinner
materials in creating these members resulting in possibly increased
payloads and improved cycle times due to the decrease in weight of
such structures.
SUMMARY OF THE INVENTION
[0003] In accordance with an embodiment of the present invention, a
load bearing arrangement for use with a work machine of the type
having a platform is provided. The load bearing arrangement
comprises at least one member structured and arranged for coupling
to the platform; the member having an end comprising a material
having a first yield strength; an aperture formed in the end and
having an aperture wall; at least one support member contained
within the opening adjacent to at least a portion of the aperture
wall; and the support member having a second yield strength greater
than said first yield strength.
[0004] In accordance with yet another aspect of the present
invention, a load bearing arrangement for use with a work machine
of the type having a platform is provided. The load bearing
arrangement comprises a plurality of pieces connectable to form a
member structured and arranged for pivotable attachment to the
platform; a weldment connecting at least two of the pieces; and at
least one weldment being simulated for effects of heat on at least
one of the pieces subject to the weldment.
[0005] In accordance with even yet another aspect of the present
invention, a method of manufacturing a load bearing member,
comprising a plurality of pieces, for use with a work machine, is
provided. The method comprises the steps of forming the pieces;
connecting at least two of the pieces by a weldment; and
determining the effects of heat caused by the weldment on at least
one of said pieces subject to said weldment.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a side elevation view of an exemplary work machine
embodying the principles of the present invention;
[0007] FIG. 2 is an isometric view of a member comprising a boom
embodying the principals of the present invention;
[0008] FIG. 3 is a cross-sectional view taken on line 3-3 of FIG.
2;
[0009] FIG. 4 is a cross-sectional view taken on line 4-4 of FIG.
2;
[0010] FIG. 5 is a partial top view of the boom shown in FIG.
2;
[0011] FIG. 6 is an isometric view of a member comprising a stick
embodying the principals of the present invention;
[0012] FIG. 7 is a cross-section view taken on line 7-7 of FIG.
2;
[0013] FIG. 8 is a cross-sectional view taken on line 8-8 of FIG.
6;
[0014] FIG. 9 is a weld formed in accordance with a method of the
present invention;
[0015] FIG. 10 is a block diagram illustrating an embodiment of an
integrated welding simulation model; and
[0016] FIG. 11 is a block diagram illustrating an embodiment of a
constitutive welding simulation model.
DETAILED DESCRIPTION
[0017] With reference now to the Figures, shown in FIG. 1 is an
exemplary work machine 100 incorporating the teachings of the
present invention. The work machine 100 comprises a platform 101
onto which is mounted a plurality of load bearing members 105
embodied herein by a first member or boom 106 and a second member
or stick 107. The boom 106 is pivotally connected to the platform
101 and moveable relative thereto by a first movement means
embodied herein by a pair of first hydraulic actuators 110 which
may comprise an extensible and retractable hydraulic cylinders.
Likewise, the first end 111 of the stick 107 is pivotally coupled
to the boom 106 via a suitable connector such as a pin 112 and is
moveable relative to the boom 106 by a second movement means
embodied herein by a second hydraulic actuator 114 which also may
comprise an extensible and retractable hydraulic cylinder. It is to
be understood that the work machine 100 shown herein is embodied by
a barge unloader, however such a showing is exemplary only and it
is contemplated that the teachings of the present invention may
have wide applicability for work machines used to support loads
such as, for example, backhoe loaders, excavators and so forth.
[0018] Attached adjacent the second end 115 of stick 107, also by
use of a suitable connector such as a pin 118, is an attachment 119
for use in grasping and holding a load of material which may
comprise debris, dirt, rock, goods or other material tapes. The
attachment 119 shown herein is embodied herein by a clamshell
bucket although it is contemplated that such a showing is for
purposes of illustration and not limitation and that other
attachment types may also be used without deviating from the spirit
of the present invention. The attachment 119 may also include a
third hydraulic actuator (not shown) for use in activating the
attachment 119.
[0019] With reference now to FIGS. 2, the boom 106 is shown
incorporating the teachings of the present invention. The boom 106
comprises a pair of spaced apart side plates 200, each forming a
respective first side 200a and a second side 200b, with each
attached preferably by a robotic welding process to a top plate 201
and a bottom plate 202. The boom 106 includes a first end 205
comprising a pair of ears 206 wherein each ear 206 includes an
aperture 209 for receipt of a pin (not shown) or other suitable
device for pivotally coupling the boom 106 to the platform 101. The
boom 106 also includes a second end 210 also having a pair of ears
213 each having an aperture 214 for receipt of pin 118. An
attachment structure 217 extends from each side plate 200 and is
used to couple the first hydraulic actuators 110 to the boom 106.
Coupling assembly 218 extend from the bottom plate 202 and are used
to pivotably support the second hydraulic actuator 114 in a well
known manner.
[0020] Also shown in hidden detail in FIG. 2 is a reinforcing
structure 221 used to reinforce each of the side plates 200 against
failure. Although the specific details of the reinforcing structure
221 will be explained in greater detail as this disclosure
progresses, suffice to say for now the use of the reinforcing
structures 221 of the present invention allows for the use of
thinner side plates 200 while preventing buckling of the side
plates 200 when load placed on the boom 106 reaches or exceeds a
given amount. The top plate 201 may be provided with a plurality of
mounting structures 222 used to secure the various hydraulic
conduits (not shown) supplying hydraulic fluid to the first and
second hydraulic actuators 110,114 as well as the attachment 119.
The details of the mounting structures 222 will be described
further with reference to FIG. 5. 11 With reference to FIGS. 3-5,
various structural features of the boom 106 will now be discussed.
Shown in cross-sectional detail in FIG. 3 is the attachment
structure 217 which is used to secure each first hydraulic actuator
110 to the boom 106. The attachment structure 217 is shown
comprising two substantially hollow cylindrical members 301 and 302
which may be coupled together in coaxial alignment, but it is to be
understood that a single such member may be utilized without
deviating from the spirit of the present invention. As shown, the
combined length of the attachment structure 217 is sufficient to
extend the transverse length of the boom 106 with each distal end
305 of each member 301,302 extending beyond each side plate 200 for
a user-selected distance. Placed within each respective member
301,302 adjacent each distal end 305 is a substantially cylindrical
support member 306 which is attached to each respective member
301,302 by a suitable method such as laser welding. Although the
details of the support member 306 will be discussed in greater
detail as this disclosure progresses, suffice to say for now each
support member 306 is sized to receive a respective bearing 307
each of which, in turn, supports a pin (not shown) used to secure
the first hydraulic actuators 110 to the boom 106.
[0021] As should be appreciated by those or ordinary skill in such
art, each of the side plates 200 may be attached to each respective
member 301,302 by a welding process preferably comprising a robotic
welding process which may be optimized based on the teaching to be
described herein with respect to FIGS. 9-11. When prepared in such
a manner the need to provide a conventional attachment structure
comprising a heavier casting to compensate for the traditionally
weaker weldment is eliminated. To further secure each member
301,302, reinforcement plates 310 may be attached to each member
301,302 by a welding process or other suitable attachment
method.
[0022] With respect to FIG. 4, shown is an arrangement for coupling
the different pieces of the boom 106 in which the pieces may
comprise plates of different thicknesses. For exemplary purposes,
shown is the side plate 200 comprising two adjacent plates denoted
plate 400 having a centerline 401 and plate 404 having a centerline
405. As shown, plates 400 and 404 are attached by a welding or like
process such that the centerlines 401,405 are substantially
co-linear. By attaching adjacent plates 400 and 404 in such manner,
a more uniform distribution of stress flow may be obtained which,
in turn, may allow for thinner plates 400 and 404.
[0023] Shown in FIG. 5 is a top view of mounting structures 222.
Each mounting structure 222 is preferably integrally formed with
the top plate 201. As also should be appreciated, forming the
mounting structures 222 as a part of the top plate 201 eliminates
the need to weld such attachment structures to the top plate 201
which, in turn, eliminates tensile residual stresses in the local
weldment region which may require the need to utilize thicker plate
materials. Each mounting structure may be provided with apertures
500 each sized to receive a suitable fastener (not shown) for use
in securing the hydraulic conduits to the top plate 201 by use of a
bracket (not shown) or other suitable attachment device.
[0024] With reference now to FIG. 6, the stick 107 is shown also
incorporating the teachings of the present invention. The stick 107
also comprises a pair of spaced apart side plates 600 each
attached, also preferably by a robotic welding process, to a top
plate 601 and a bottom plate 602. The stick 107 includes the first
end 111 sized to fit between the ears 213 of the second end 210 of
the boom 106. The first end 111 further includes an aperture 606
for receipt of pin 112 thereby providing for the aforementioned
pivotal attachment to the boom 106. The second end 115 of the stick
107 also includes an aperture 607 sized to receive pin 118.
Coupling assembly 609 extend from the bottom plate 602 and is used
to pivotably support the second hydraulic actuator 114 in a well
known manner.
[0025] Also shown in hidden detail in FIG. 6 are a plurality of
reinforcing structures each denoted by the reference numeral 610
which are used to reinforce each of the side plates 600 against
buckling at pre-determined buckling prone areas. Although the
specific details of the reinforcing structures 610 will also be
explained in greater detail as this disclosure progresses, suffice
to say for now the use of the reinforcing structures 610 of the
present invention also allows for the use of thinner side plates
600 on the stick 107 while preventing buckling of the side plates
600 at pre-determined buckling prone areas when loads placed on the
stick 107 reach or exceed a given amount. It should be appreciated
by those of ordinary skill in such art, that the number of
reinforcing structures 221,610 to be used is a matter of design
selection and need not constitute any more than is necessary to
achieve the needed performance, and by limiting the number of
reinforcing structures 221,610 used the weight of the boom 106 and
the stick 107 may be minimized. The top plate 601 may also be
provided with mounting structures 611 which are used to secure the
various hydraulic conduits (not shown) supplying hydraulic fluid to
the first and second hydraulic actuators 110,114 as well as the
attachment 119. The details of the mounting structures 611 are
substantially similar to those of mounting structures 222 described
above and so will not be described any further herein.
[0026] With reference to the cross-sectional shown in FIG. 7, the
location and configuration of the reinforcing structures 221,610
will now be discussed. For purposes of brevity the following
discussion will be limited to the reinforcing structure 221 for the
boom 106, however it is to be understood that the disclosure herein
is equally applicable to the reinforcing structures 610 used for
the stick 107. As shown, at least one reinforcing structure 221 is
attached to an inner surfaces 700 of the side plates 200 by a
suitable attachment method preferably a laser welding method. As
should be appreciated by those of ordinary skill in such art, it
has been found that the use of laser welding to attach the
reinforcing structure 221 to the side plates 200 reduces the heat
effected zone surrounding the weld area, thereby allowing for
thinner side plates 200 then would otherwise be required for
different welding-type attachment methods. It is to be understood
that the attachment location of each reinforcing structure 221 is
exemplary only and it is contemplated that other attachment
locations for the reinforcing structures 221 may be had such as,
for example, the outer surface 701 of each of the side plates
200.
[0027] As shown, each reinforcing structure 221 comprises a
substantially straight member having a base portion 704 and a rib
portion 705 extending from the base portion 704. The reinforcing
structure 221 may comprise a metallic or other rigid material and
has a length which is user-selected based on the failure analysis
performed by using a suitably selected failure analysis package
such as Nastran (TM). Furthermore, it is also contemplated that
other geometry's for the reinforcing structure 221 may also be used
with deviating from the spirit of the present invention such as,
for example, a cylindrical or flat configuration.
[0028] Shown in cross-section in FIG. 8 are the details of the
first end 111 of stick 107. A pair of substantially cylindrical
support members 801 are received within the aperture 606 are used
to house a corresponding pair of bearings 802 which, in turn,
support pin 112. Each of the support members 801 are sized to lie
adjacent to the aperture wall 803 and each are preferably laser
welded to the surrounding stick material denoted 805. In addition,
and the material comprising each support member 801 is preferably
chosen to have a yield strength exceeding that of the surrounding
stick material 805. In selecting a material for the support members
801 having a higher yield strength then the surrounding stick
material 805, the support members 801 can absorb the radial
stresses produced by pressure fitting the bearings 802 into the
respective support members 801 which allows for less stick material
805 surrounding the aperture 606 then otherwise would be required.
By providing for less stick material 805 at the first end 111, the
effective moment arm between the stick 107 and the boom 106 may be
decreased resulting in a decreased stress level produced in the
stick 107 for the same relative loading condition. As should be
apparent to those of ordinary skill in such art, support members
exhibiting similar properties can be provided in the remaining
stick aperture 607, the boom apertures 209 and 214, as well as the
support members 306 used with the attachment structure 217.
[0029] Shown in FIG. 9 is a diagrammatical representation of the
weldment 900 created to secure two plates together both denoted as
901. The weld geometry of the weldment 900 includes a weld toe 904,
a weld profile 905 and a penetration 908. In the manufacture of the
load bearing members 105 described herein, it is advantageous to
control the resultant residual stresses at the location of the
weldment. For example, the stress diagram denoted 910 illustrates
the resultant residual stress located under the weld toe 904 with
"+" indicating a compressive residual stress, and "-" indicating a
tensile residual stress. At the weld toe 904 it is desirable to
achieve a compressive residual stress without the need for any post
weld treatment of the weldment 900. To control the resultant
residual stress at the location of the weldment 900, the weld
simulation tools to be discussed immediately hereinafter may be
utilized. The results of the simulation may then be used to control
the weld process which preferably comprises a robotic welding
process. To control the fit-up of the plates 901 as well as the
penetration 908, it is preferred that the plates are formed from a
precision cutting operation such as laser cutting.
[0030] Referring to FIG. 10, a block diagram illustrating a
preferred embodiment of a set of integrated models 1000 for
performing a simulation analysis of a welding process is shown. The
integrated models 1000 work together to determine stresses and
distortions of a material which is welded in the welding process.
The stresses and distortions have an adverse effect on the
strengths and characteristics of the material. Therefore, it is
desired to model the stresses and distortions and use the
information from the models to determine methods which may minimize
the adverse effects of welding.
[0031] In the preferred embodiment, an interconnection tool 1014,
such as a graphical user interface (GUI), interconnects the models
into an integrated network of working models to determine stresses
and distortions of the material.
[0032] The interconnection tool 1014 is preferably computer-based
and may be configured to operate autonomously, through manual
intervention, or some combination of the two modes. For example,
the interconnection tool 1014 may coordinate the modeling functions
while displaying the status and results to a human, who may
override the system or input additional information at any desired
time.
[0033] A geometry modeler 1002 determines the geometry model for
the materials to be welded. Preferably, the geometry modeler 1002
simplifies the geometry by removing unnecessary features of the
materials from the model. Examples of such features include, but
are not limited to, chamfers, holes, slight irregularities, and the
like.
[0034] The geometry model data is then delivered to a meshing tool
1004. The meshing tool 1004 is used to generate a finite element
analysis mesh, preferably by defining coordinates for elements and
nodes which constitute the mesh. Finite element analysis techniques
which use mesh coordinates are well known in the art and will not
be described further.
[0035] A thermal analysis model 1006 is used to perform a thermal
analysis of the materials during the welding process. In the
preferred embodiment, the thermal analysis model 1006 includes at
least two models. An analytical solution model 1008 provides a
rapid analytical solution of the thermal process, i.e., welding
process, for a global solution of distortions caused by the welding
process. A finite element analysis model 1010 provides local
detailed analysis of residual stress from the welding process.
[0036] In the preferred embodiment, the analytical solution model
1008 determines solutions of point heat sources, the point heat
sources being obtained from heat input based on welding processes
and reflected heat sources determined from adiabatic boundary
conditions of the material. The total analytical solution is
determined from superposition of all the point heat sources. The
principle of obtaining reflected heat sources from adiabatic
boundary conditions is well known in the art and will not be
discussed further. The analytical solution model 1008 provides a
rapid solution for the complete welding process. However, the
solution is not highly detailed. Therefore, the analytical solution
model 1008 is typically used when a fast, global solution is
desired, and a high degree of detail is not needed.
[0037] The finite element analysis model 1010 employs numerical
computations of conditions at each of the desired node and element
coordinates of the finite element analysis mesh. The finite element
analysis model tends to be computationally lengthy and intensive.
Therefore, the finite element analysis model 1010 is generally used
only when a detailed analysis of a specific portion of the model is
desired.
[0038] The information from the thermal analysis model 1006 is
compiled into a thermal history and delivered to a structural
analysis model 1012. In addition, the finite element mesh provided
by the meshing tool 1004 is delivered to the structural analysis
model 1012. The interconnection is automatically established in the
interconnection tool 1014. In the preferred embodiment, the thermal
history is delivered from the thermal analysis model 1006 to the
structural analysis model 1012 by way of an interface module 1016.
Preferably, the interface module 1016 is automated from the
interconnection tool 1014 and is adapted to seamlessly connect the
thermal solution from the analytical solution model 1008, the
finite element analysis model. 1010, or both, to the structural
analysis model 1012.
[0039] The structural analysis model 1012 provides further analysis
of the materials during the welding process. Typically, the
behavior of the material during welding is analyzed and modeled.
Examples of features analyzed include, but are not limited to,
melting and remelting of the material, phase transformation of the
material, cyclic effects of multiple weld passes, and the like. The
stresses and distortions of the material are determined by the
structural analysis model. Preferably, the determined stresses and
distortions may be further analyzed and subsequently used to modify
the welding process to reduce the adverse effects of the extreme
heat associated with welding.
[0040] Referring to FIG. 11, a model 2000 of the weld process is
shown, which is based on a constitutive model 2002. Constitutive
models, e.g., for welding process simulation, are well known in the
art and have been used for many years. A constitutive model is a
model based on a compilation of physical laws associated with the
phenomenon desired to be modeled.
[0041] A history annihilation model 2004 models melting/remelting
of the material during the weld process. In addition, annealing of
the material during cyclic melting/remelting of the material during
multiple weld passes is modeled. As the material melts, the
deformation history, i.e., the stresses and deformations, of the
material is eliminated, and the material is restored to a virgin
state. Therefore, for accurate modeling of the welding process,
stresses and distortions must be reset in response to the
occurrence of a melting/remelting condition.
[0042] A large deformation model 2006 is used to model thermal and
mechanical strain increments of the material being welded. More
specifically, the large deformation model 2006 models the
distinguishing characteristics between plastic and elastic
annealing strains during the welding process.
[0043] A virtual elements detection model 2008 provides virtual
elements for weld passes which have not actually occurred. In a
multiple pass welding process, models must include all passes
before any weld metal is actually deposited. For example, the
stiffness of the material must be modeled as though all weld passes
have been completed, even though welding has not begun. Typical
welding model packages compensate for this by a process known as
element birth and death. The finite elements of the weld metal must
be deactivated until later in the modeling process. This method is
very tedious and requires much time and computational power to
perform, since the elements must be removed from the files and
restored later. The virtual elements detection model 2008 overcomes
this by assuming that the weld metal has been deposited at a
minimal stiffness. As the subsequent weld passes are performed, the
metal stiffness from each pass is modified to more closely reflect
the actual stiffness created by the welding process. In the
preferred embodiment, the virtual elements detection model 2008 is
a three-dimensional model to provide modeling not only of the
portion of the material being welded, but to also provide modeling
of portions of the material to be welded as the overall weld
process takes place.
[0044] A strain hardening model 2010 models the yield strength
which increases as a result of the thermal cycles associated with
the multiple weld passes. Yield strength increases as the stresses
and strains of welding move from a zero state to a yield state,
i.e., from before heating the material to a point just prior to the
material yielding to the application of the heat. The strain
hardening model 2010 is adapted to perform a series of iterations
to determine the increments of plastic strain of the material.
[0045] A phase transformation model 2012 models changes in the
microstructure of the material during the welding process. The
changes in the microstructure of the material are a function of
parameters such as the chemical composition of the material,
conditions of the welding process, and the like. Changes in the
material include, but are not limited to, volumetric changes during
the phase transformation, transformation plasticity, and yield
hysteresis due to phase differences in the heating and cooling
processes.
[0046] A temperature history database 2014 stores and provides a
temperature history of the material during the welding process.
Preferably, the temperature history database 2014 provides
temperature history data to the constitutive model 2002 and the
history annihilation model 2004.
[0047] A microstructure database 2016 stores and provides data of
the microstructure of the material during the welding process.
Preferably, the microstructure database 2016 provides
microstructure data to the constitutive model 2002 and the phase
transformation model 2012. In addition, the microstructure database
2016 may receive microstructure data of the material from the phase
transformation model 2012.
[0048] A material data database 2018 stores and provides data of
the material, e.g., stresses and strains of the material, during
the welding process. Preferably, the material data database
provides data to the constitutive model 2002, the strain hardening
model 2010, and the phase transformation model 2012.
INDUSTRIAL APPLICABILITY
[0049] In use and in operation, the present invention provides for
weight savings in load bearing members 105 while maintaining the
same payload capacity of the work machine 100. As should be
appreciated by those of ordinary skill in such art, controlling the
amount of distortion and residual stresses at the weldment 900
provides for a weld having a greater fatigue life then otherwise
would be possible. The present invention also utilizes an enhanced
and more accurate model of the stresses and distortions which occur
during a welding process, as compared to typical welding process
models currently known. The characteristics of the materials being
welded are modeled as temperatures approach levels which cause
changes in the material properties. Examples of welding related
material behaviors which are modeled include, but are not limited
to, melting/remelting caused by multiple weld passes, material
history annihilation caused by annealing, thermal cycling, i.e.,
alternate heating and cooling of the material, phase
transformations, and the like. The results of the above modeling
are incorporated into a constitutive weld model to provide a
complete model of the effects of the weld process. This complete
model may then be used to minimize adverse effects caused by
welding.
[0050] In addition, it should also be appreciated by those of
ordinary skill in such art, the use of support members 306,801,
integral mounting structures 222, 611, aligned centerlines 401,405,
reinforcing structure 221, 610 and the attachment structure 217 all
as illustrated and described herein may contribute to a further
weight savings in the weight of these structures.
[0051] Other aspects, objects and advantages of this invention can
be obtained from a study of the drawings, the disclosure and the
appended claims.
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