U.S. patent application number 15/957976 was filed with the patent office on 2018-08-23 for hybrid workpiece joining.
The applicant listed for this patent is GM GLOBAL TECHNOLOGY OPERATIONS LLC. Invention is credited to Bradley J. Blaski, Richard C. Janis, Pei-chung Wang.
Application Number | 20180236528 15/957976 |
Document ID | / |
Family ID | 62026298 |
Filed Date | 2018-08-23 |
United States Patent
Application |
20180236528 |
Kind Code |
A1 |
Wang; Pei-chung ; et
al. |
August 23, 2018 |
HYBRID WORKPIECE JOINING
Abstract
A joining device includes a nose, a punch, and a die anvil. The
punch is coaxially slidable within the nose. A fastener is arranged
within the nose and is coaxially slidable within the nose and
movable by the punch. An ultrasonic vibration is focused through
the die anvil to a zone on a material assembly arranged thereon for
heating the zone. The punch is configured to drive the fastener
outwardly from the nose and into the material assembly at the
zone.
Inventors: |
Wang; Pei-chung; (Troy,
MI) ; Blaski; Bradley J.; (Sterling Heights, MI)
; Janis; Richard C.; (Grosse Pointe Woods, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GM GLOBAL TECHNOLOGY OPERATIONS LLC |
DETROIT |
MI |
US |
|
|
Family ID: |
62026298 |
Appl. No.: |
15/957976 |
Filed: |
April 20, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15348595 |
Nov 10, 2016 |
|
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15957976 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B29C 65/02 20130101;
B29C 66/81871 20130101; B29C 66/81423 20130101; B29C 65/7841
20130101; B29C 66/1122 20130101; B21J 15/14 20130101; B21J 15/147
20130101; B21J 15/12 20130101; B29C 66/0242 20130101; B21J 15/08
20130101; B21J 15/025 20130101; B29C 66/8322 20130101; B29C 65/002
20130101; B21J 15/36 20130101; B29C 65/562 20130101; B29C 65/08
20130101; B29C 66/21 20130101; B29C 66/73921 20130101; B29C
66/81431 20130101; B21J 15/26 20130101; B29C 66/41 20130101; B29C
65/3408 20130101 |
International
Class: |
B21J 15/14 20060101
B21J015/14; B21J 15/36 20060101 B21J015/36; B21J 15/26 20060101
B21J015/26 |
Claims
1. (canceled)
2. (canceled)
3. (canceled)
4. (canceled)
5. (canceled)
6. A joining device comprising: a nose horn; a punch coaxially
slidable within the nose horn; a fastener arranged within the nose
horn, the fastener being coaxially slidable within the nose horn
and movable by the punch; and a die having a material assembly
arranged thereon, wherein the nose horn is axially movable to a
position contacting the material assembly, wherein an ultrasonic
vibration is focused through the nose horn to a zone on the
material assembly for heating the zone, and wherein the punch is
configured to drive the fastener outwardly from the nose horn and
into the material assembly at the zone.
7. The joining device of claim 6, wherein the material assembly
includes a first and second workpiece and wherein the fastener is
configured to join the first workpiece to the second workpiece.
8. The joining device of claim 7, wherein the fastener further
includes a head and a shank extending from the head, and wherein
the punch contacts the fastener at the head and drives the shank
through the first workpiece and into the second workpiece.
9. The joining device of claim 8, wherein the die has a die face
that receives the second workpiece when the shank of the fastener
is in the zone, and wherein the shank of the fastener is deformed
to create a mechanical joint with the first and second
workpieces.
10. The joining device of claim 6, wherein at least a portion of
the zone on the material assembly is fused upon cooling of the
zone.
11. A joining device comprising: a nose; a punch coaxially slidable
within the nose; a fastener arranged within the nose, the fastener
being coaxially slidable within the nose and movable by the punch;
and an electrode die, wherein an electrical current is focused
through the electrode die to a zone on a material assembly arranged
thereon for heating the zone, and wherein the punch is configured
to drive the fastener outwardly from the nose and into the material
assembly at the zone.
12. The joining device of claim 11, wherein the electrode die
further comprises: an insulator; a first conductor arranged about
the insulator; and a second conductor arranged on an end surface of
the first conductor, the second conductor configured to contact the
material assembly.
13. The joining device of claim 12, wherein the insulator is one of
a ceramic and a polymer.
14. The joining device of claim 12, wherein the first conductor is
a tungsten carbide.
15. The joining device of claim 12, wherein the second conductor is
a steel.
16. The joining device of claim 11, wherein the material assembly
includes a first and second workpiece and wherein the fastener is
configured to join the first workpiece to the second workpiece.
17. The joining device of claim 16, wherein the fastener further
includes a head and a shank extending from the head, and wherein
the punch contacts the fastener at the head and drives the shank
through the first workpiece and into the second workpiece.
18. The joining device of claim 17, wherein at least a portion of
the zone on the material assembly is fused upon cooling of the
zone.
19. The joining device of claim 17, wherein the shank of the
fastener is deformed to create a mechanical joint with the first
and second workpieces.
20. The joining device of claim 16, wherein an electrical power
source is interconnected with the electrode die to selectively
create an electrical circuit for conducting electrical current
through the first and second conductors, wherein the electrical
current at the second conductor locally heats the second workpiece.
Description
FIELD
[0001] The present disclosure relates to a workpiece assembly
including a fastener and a joining method thereof.
INTRODUCTION
[0002] The statements in this section merely provide background
information related to the present disclosure and may not
constitute prior art.
[0003] Joining of both ferrous and non-ferrous materials can be
achieved through various methods. In one example for joining
overlapping members, a self-piercing rivet can be driven under
pressure into the members. A die or mandrel may disrupt a terminal
end of the self-piercing rivet in order to create a mechanical
interference between the members and the rivet. In another example
for joining overlapping members, an ultrasonic welding device can
use high-frequency ultrasonic vibrations to generate heat at an
interface of the workpieces. The heated workpieces may melt
sufficiently to create a joint at the interface.
SUMMARY
[0004] A joining device includes a nose, a punch, and a die anvil.
The punch is coaxially slidable within the nose. A fastener is
arranged within the nose and is coaxially slidable within the nose
and movable by the punch. An ultrasonic vibration is focused
through the die anvil to a zone on a material assembly arranged
thereon for heating the zone. The punch is configured to drive the
fastener outwardly from the nose and into the material assembly at
the zone.
[0005] In some embodiments, the material assembly includes a first
and second workpiece and the fastener is configured to join the
first workpiece to the second workpiece. The fastener further
includes a head and a shank extending from the head, and the punch
may contact the fastener at the head and drive the shank through
the first workpiece and into the second workpiece. Furthermore, the
die anvil has a die face that receives the second workpiece when
the shank of the fastener is in the zone, and the shank of the
fastener is deformed to create a mechanical joint with the first
and second workpieces. Additionally, at least a portion of the zone
on the material assembly is fused upon cooling of the zone.
[0006] A joining device includes a nose horn, a punch coaxially
slidable within the nose horn, and a die having a material assembly
arranged thereon. A fastener is arranged within the nose horn and
is coaxially slidable within the nose horn and movable by the
punch. The nose horn is axially movable to a position contacting
the material assembly. An ultrasonic vibration is focused through
the nose horn to a zone on the material assembly for heating the
zone. The punch is configured to drive the fastener outwardly from
the nose horn and into the material assembly at the zone.
[0007] In some embodiments, the material assembly includes a first
and second workpiece and the fastener is configured to join the
first workpiece to the second workpiece. The fastener further
includes a head and a shank extending from the head, and the punch
may contact the fastener at the head and drive the shank through
the first workpiece and into the second workpiece. Furthermore, the
die has a die face that receives the second workpiece when the
shank of the fastener is in the zone, and the shank of the fastener
is deformed to create a mechanical joint with the first and second
workpieces. Additionally, at least a portion of the zone on the
material assembly is fused upon cooling of the zone.
[0008] A joining device includes a nose, a punch, and an electrode
die. The punch is coaxially slidable within the nose. A fastener is
arranged within the nose and is coaxially slidable within the nose
and movable by the punch. An electrical current is focused through
the electrode die to a zone on a material assembly arranged thereon
for heating the zone. The punch is configured to drive the fastener
outwardly from the nose and into the material assembly at the
zone.
[0009] In some embodiments, the electrode die includes an insulator
(e.g., ceramic or polymer), a first conductor (e.g., tungsten
carbide) arranged about the insulator, and a second conductor
(e.g., steel) arranged on an end surface of the first conductor,
with the second conductor configured to contact the material
assembly. The material assembly can include a first and second
workpiece with the fastener configured to join the first workpiece
to the second workpiece. The fastener further includes a head and a
shank extending from the head, and the punch may contact the
fastener at the head and drive the shank through the first
workpiece and into the second workpiece. Additionally, at least a
portion of the zone on the material assembly is fused upon cooling
of the zone. Furthermore, the shank of the fastener is deformed to
create a mechanical joint with the first and second workpieces. In
addition, an electrical power source can be interconnected with the
electrode die to selectively create an electrical circuit for
conducting electrical current through the first and second
conductors, where the electrical current at the second conductor
locally heats the second workpiece.
[0010] Further areas of applicability will become apparent from the
description provided herein. It should be understood that the
description and specific examples are intended for purposes of
illustration only and are not intended to limit the scope of the
present disclosure.
DRAWINGS
[0011] The drawings described herein are for illustration purposes
only and are not intended to limit the scope of the present
disclosure in any way.
[0012] FIGS. 1A through 1E depict schematic views of an exemplary
hybrid joining machine according to the present disclosure;
[0013] FIG. 2 is a flow diagram of an exemplary hybrid joining
process utilizing the hybrid joining machine of FIGS. 1A through
1E;
[0014] FIGS. 3A through 3E depict schematic views of another
exemplary hybrid joining machine according to the present
disclosure;
[0015] FIG. 4 is a flow diagram of another exemplary hybrid joining
process utilizing the hybrid joining machine of FIGS. 3A through
3E;
[0016] FIGS. 5A through 5E depict schematic views of yet another
exemplary hybrid joining machine according to the present
disclosure; and
[0017] FIG. 6 is a flow diagram of yet another exemplary hybrid
joining process utilizing the hybrid joining machine of FIGS. 5A
through 5E.
DETAILED DESCRIPTION
[0018] The following description is merely exemplary in nature and
is not intended to limit the present disclosure, application, or
uses. It should be understood that throughout the drawings,
corresponding reference numerals indicate like or corresponding
parts and features. Further, directions such as "top," "side,"
"back", "lower," and "upper" are used for purposes of explanation
and are not intended to require specific orientations unless
otherwise stated. These directions are merely provided as a frame
of reference with respect to the examples provided, but could be
altered in alternate applications.
[0019] The present disclosure describes a hybrid technique for
joining workpieces, such as polymeric composites, by a combination
of integral fastening (e.g., self-piercing riveting) and localized
material fusing. With reference to the drawings, wherein like
reference numbers refer to like components, each of the exemplary
hybrid joining machines includes a nose 12, a punch 14, and a die
16. The hybrid joining machines can be used to join first and
second workpieces 18, 20 with a fastener 22. In one exemplary
embodiment, the fastener 22 can be a rivet having a head portion 24
and a generally cylindrical hollow shank 26 ending in a tapered
extremity 28. The rivet 22 is configured to mechanically fasten the
first and second workpieces 18, 20 when subjected to a driving
force, such as may be achieved by the punch 14 acting on the rivet
22. The rivet 22 is referred to as a "self-piercing" rivet, as the
tapered extremity 28 is sufficient to cause penetration of the
workpieces 18, 20 under the force of the punch 14. Furthermore, the
shank 26 is configured to deform to create a mechanical joint
without requiring a lead hole for the rivet 22 in the workpieces
18, 20.
[0020] With reference now to FIGS. 1A through 1E, an exemplary
hybrid joining machine 10 incorporates a hybrid joining technique
involving the mechanical fastening of riveting with an ultrasonic
energy applied to the second workpiece 20. In this regard, line
power (e.g., low-frequency electrical signal of about 50-60 Hz) is
converted to a high frequency, high voltage electrical signal
(e.g., 15-70 kHz, and more particularly 20-40 kHz). The high
frequency electrical signal is then converted to a mechanical
vibration at an ultrasonic frequency in a converter (i.e.,
transducer). An optional booster may be included in the system in
order to amplify the mechanical vibration such that the vibration
amplitude can be increased. The ultrasonic vibrations then
propagate through the die anvil 16. An end face 30 of the die anvil
16 can then focus the ultrasonic vibration and deliver the
vibration energy to a specified area on a material (e.g., at a
portion of the second workpiece 20 to be riveted).
[0021] With reference to FIG. 2, a method 50 of joining the
workpieces 18, 20 will be described with respect to the hybrid
joining machine 10 of FIGS. 1A through 1E. Specifically, at step
52, first and second workpieces 18, 20 are arranged on the die
anvil 16 such that the second, lower workpiece 20 rests directly on
the die anvil 16 and the first, upper workpiece 18 rests on the
lower workpiece 20, as shown in FIG. 1A. At step 54, the nose 12 is
actuated by hydraulic pressure so as to behave as a retractable
clamping cylinder for the machine 10. The nose 12 is driven
downwardly towards the upper workpiece 18 to urge the workpieces
18, 20 against the die anvil 16, as shown in FIG. 1B. It should be
noted that other drive mechanisms may be used for driving the nose
12, e.g., an electrically powered screw assembly, an electrically
powered actuator, or via a spring.
[0022] At step 56, the die anvil 16 is excited with ultrasonic
vibration so as to locally heat the workpieces 18, 20. The
transmitted waves are bounced back by the die anvil 16. The
mechanical waves from the vibration cause the workpieces 18, 20 to
oscillate (i.e., deform). The oscillations of the workpieces 18, 20
generate heat at the both the interface between the die anvil 16
and workpiece 20 and at the interface between the workpieces 18, 20
creating a localized heated material zone 32. At step 58, the punch
14, which is coaxially slidable within the nose 12, is actuated so
as to drive the rivet 22 into the upper workpiece 18 (see FIG. 1C).
The punch 14 continues driving the rivet 22 until the rivet 22
penetrates the lower workpiece 20. In particular, the punch 14
contacts the head portion 24 and pierces the upper workpiece 18
with the shank 26 only partially piercing and entering, but not
completely passing through the lower workpiece 20 (i.e., does not
pass through the bottom surface of the lower workpiece 20).
Notably, the localized heated material zone 32 allows for enhanced
riveting since stresses and friction in this material zone are
reduced.
[0023] At step 60 (see FIG. 1D), the shank 26 and the material of
the lower workpiece 20 immediately adjacent to the shank 26 are
then deformed through interaction with the die anvil 16. The bottom
surface of the lower workpiece 20 is subjected to the force of the
die anvil 16 as described herein such that the shape of the surface
of the lower workpiece 20 is modified to conform to the shape of
the die anvil 16. The complementary shape on the lower workpiece 20
mechanically interlocks the workpieces 18, 20.
[0024] Furthermore, as the localized heated material zone 32 cools,
a fused region 34 is created at an interface between the workpieces
18, 20. In this way, the mechanical joint is supplemented by the
fused region 34 between the upper and lower workpieces 18, 20. The
fused region 34 contributes to the strength of the mechanical
interface. The fused region 34 is most conveniently achieved if
both the workpieces 18, 20 are thermoplastic composite materials,
having similar melting temperatures. However, the workpieces 18, 20
may be alternate materials, including materials different from one
another provided they are weldably compatible. The fused region 34
should be considered representative of a wide range of fused areas
that may result from this process. Depending on the duration and
magnitude of application of the ultrasonic vibration, the extent of
fused region 34 may vary. However, to strengthen the interface and
ease the insertion of the rivet 22, at least a minimum localized
heated material zone 32 should be developed around the
circumference of shank 26.
[0025] At step 62, the punch 14 and nose 12 are withdrawn from the
riveted workpieces 18, 20 and the riveted workpieces 18, 20 are
removed from the die anvil 16 (see FIG. 1E). The assembled
workpieces 18, 20 and rivet 22 provide a robust weld, capable of
withstanding delamination and microcracking.
[0026] With reference now to FIGS. 3A through 3E, an exemplary
hybrid joining machine 100 incorporates a hybrid joining technique
involving the mechanical fastening of riveting with an ultrasonic
energy applied to a workpiece. As previously noted, line power
(e.g., low-frequency electrical signal of about 50-60 Hz) is
converted to a high frequency, high voltage electrical signal
(e.g., 15-70 kHz, and more particularly 20-40 kHz). The high
frequency electrical signal is then converted to a mechanical
vibration at an ultrasonic frequency in a converter (i.e.,
transducer). An optional booster may be included in the system in
order to amplify the mechanical vibration such that the vibration
amplitude can be increased. The ultrasonic vibrations then
propagate through a nose horn 112. An end face 136 of the nose horn
112 can then focus the ultrasonic vibration and deliver the
vibration energy to a specified area on a material (e.g., at a
portion of a first workpiece 118 to be riveted).
[0027] With reference to FIG. 4, a method 150 of joining first and
second workpieces 118, 120 will be described with respect to the
hybrid joining machine 100 of FIGS. 3A through 3E. Specifically, at
step 152, the first and second workpieces 118, 120 are arranged on
a die 116 such that the second, lower workpiece 120 rests directly
on the die 116 and the first, upper workpiece 118 rests on the
lower workpiece 120, as shown in FIG. 3A. At step 154, the nose
horn 112 is actuated by hydraulic pressure so as to behave as a
retractable clamping cylinder for the machine 100. The nose horn
112 is driven downwardly towards the upper workpiece 118 to urge
the workpieces 118, 120 against the die 116, as shown in FIG. 3B.
It should be noted that other drive mechanisms may be used for
driving the nose horn 112, e.g., an electrically powered screw
assembly, an electrically powered actuator, or via a spring.
[0028] At step 156, the nose horn 112 is excited with ultrasonic
vibration so as to locally heat the workpieces 118, 120. The
mechanical waves from the vibration cause the workpieces 118, 120
to oscillate (i.e., deform). The oscillations of the workpieces
118, 120 generate heat at both the interface between the nose horn
112 and the workpiece 118 and at the interface between the
workpieces 118, 120 creating a localized heated material zone 132.
At step 158, a punch 114, which is coaxially slidable within the
nose horn 112, is actuated so as to drive a rivet 122 into the
upper workpiece 118. The punch 114 continues driving the rivet 122
until the rivet 122 penetrates the lower workpiece 120 (see FIG.
3C). In particular, the punch 114 contacts a head portion 124 of
the rivet 122 and pierces the upper workpiece 118 with a shank 126
of the rivet 122 only partially piercing and entering, but not
completely passing through the lower workpiece 120 (i.e., does not
pass through the bottom surface of the lower workpiece 120).
Notably, the localized heated material zone 132 allows for enhanced
riveting since stresses and friction in this material zone are
reduced.
[0029] At step 160, the shank 126 and the material of the lower
workpiece 120 immediately adjacent to the shank 126 are deformed
through interaction with the die 116. The bottom surface of the
lower workpiece 120 is subjected to the force of the die 116 as
described herein such that the shape of the surface of the lower
workpiece 120 is modified to conform to the shape of the die 116.
The complementary shape on the lower workpiece 120 mechanically
interlocks the workpieces 118, 120, as shown in FIG. 3D.
[0030] Furthermore, as the localized heated material zone 132
cools, a fused region 134 is created at an interface between the
workpieces 118, 120. In this way, the mechanical joint is
supplemented by the fused region 134 between the upper and lower
workpieces 118, 120. The fused region 134 contributes to the
strength of the mechanical interface. The fused region 134 is most
conveniently achieved if both the workpieces 118, 120 are
thermoplastic composite materials, having similar melting
temperatures. However, the workpieces 118, 120 may be alternate
materials, including materials different from one another provided
they are weldably compatible. The fused region 134 should be
considered representative of a wide range of fused areas that may
result from this process. Depending on the duration and magnitude
of application of the ultrasonic vibration, the extent of the fused
region 134 may vary. However, to strengthen the interface and ease
the insertion of the rivet 122, at least a minimum localized heated
material zone 132 should be developed around the circumference of
shank 126.
[0031] At step 162, the punch 114 and nose 112 are withdrawn from
the riveted workpieces 118, 120 and the riveted workpieces 118, 120
are removed from the die 116 (see FIG. 3E). The assembled
workpieces 118, 120 and rivet 122 provide a robust weld, capable of
withstanding delamination and microcracking.
[0032] With reference now to FIGS. 5A through 5E, an exemplary
hybrid joining machine 200 incorporates a hybrid joining technique
involving the mechanical fastening of riveting with an electrode
energy (i.e., Joule heat) applied to a workpiece. In this regard,
an electrical power source may be connected to a die to create an
electrical circuit that generates heat at a specified area on a
material (e.g., at a portion of a workpiece to be riveted).
[0033] In particular, a lower electrode die 216 may be split into a
first portion 238, also referred to as an insulator (e.g., polymer,
ceramic); a second portion 240, also referred to as a first
conductor (e.g., tungsten carbide); and a washer 242, also referred
to as a second conductor (e.g., steel). The insulator 238 may be
formed with the first conductor 240 to establish an interior wall
244 of the die 216. The second conductor 242 may be arranged on an
end surface 230 of the first conductor 240 so as to contact a lower
workpiece 220. An electrical power source 246 may be interconnected
with the die 216 at the first conductor 240, in order to
selectively create an electrical circuit. The electrical circuit
runs through the electrically conducting components of the
assembly, namely from the first conductor 240 through the second
conductor 242 and out again through the first conductor 240. The
electrical energy running through the second conductor 242 locally
heats the lower workpiece 220.
[0034] With reference now to FIG. 6, a method 250 of joining
workpieces 218, 220 will be described with respect to the hybrid
joining machine 200 of FIGS. 5A through 5E. Specifically, at step
252, first and second workpieces 218, 220 are arranged on the die
216 such that the second, lower workpiece 220 rests directly on the
die 216 and the first, upper workpiece 218 rests on the lower
workpiece 220, as shown in FIG. 5A. At step 254, the nose 212 is
actuated by hydraulic pressure so as to behave as a retractable
clamping cylinder for the machine 200. The nose 212 is driven
downwardly towards the upper workpiece 218 to urge the workpieces
218, 220 against the die 216, as shown in FIG. 5B. It should be
noted that other drive mechanisms may be used for driving the nose
212, e.g., an electrically powered screw assembly, an electrically
powered actuator, or via a spring.
[0035] At step 256, the electrical power source 246 is initiated
and electrical current flows through the first conductor 240 to the
second conductor 242, around the second conductor 242, and back out
through the opposite side of the first conductor 240, as depicted
by arrows 248. The electrical current passing through the second
conductor 242 locally generates joule heat, consequently heating
the workpieces 218, 220. The heat may propagate through the
workpiece 220 creating a localized heated material zone 232.
[0036] At step 258, a punch 214, which is coaxially slidable within
the nose 212, is actuated so as to drive a rivet 222 into the upper
workpiece 218. The punch 214 continues driving the rivet 222 until
the rivet 222 penetrates the lower workpiece 220 (see FIG. 5C). In
particular, the punch 214 contacts a head portion 224 of the rivet
222 and pierces the upper workpiece 218 with a shank 226 of the
rivet 222 only partially piercing and entering, but not completely
passing through the lower workpiece 220 (i.e., does not pass
through the bottom surface of the lower workpiece 220). Notably,
the localized heated material zone 232 allows for enhanced riveting
since stresses and friction at least in this material zone are
reduced.
[0037] At step 260, the shank 226 and the material of the lower
workpiece 220 immediately adjacent to the shank 226 are deformed
through interaction with the die 216. The bottom surface of the
lower workpiece 220 is subjected to the force of the die 216 as
described herein such that the shape of the surface of the lower
workpiece 220 is modified to conform to the shape of the die 216.
The complementary shape on the lower workpiece 220 mechanically
interlocks the workpieces 218, 220, as shown in FIG. 5D. The
electrical current from the electrical power source 246 may then be
removed in order to allow the material zone 232 to cool. As
previously noted, to ease the insertion of the rivet 222, at least
a minimum localized heated material zone 232 should be developed
around the circumference of shank 226.
[0038] At step 262, the punch 214 and nose 212 are withdrawn from
the riveted workpieces 218, 220 and the riveted workpieces 218, 220
are removed from the die 216 (see FIG. 5E). The assembled
workpieces 218, 220 and rivet 222 provide a robust weld, capable of
withstanding delamination and microcracking.
[0039] Embodiments of the present disclosure are described herein.
This description is merely exemplary in nature and, thus,
variations that do not depart from the gist of the disclosure are
intended to be within the scope of the disclosure. The figures are
not necessarily to scale; some features could be exaggerated or
minimized to show details of particular components. Therefore,
specific structural and functional details disclosed herein are not
to be interpreted as limiting, but merely as a representative basis
for teaching one skilled in the art to variously employ the present
invention. As those of ordinary skill in the art will understand,
various features illustrated and described with reference to any
one of the figures can be combined with features illustrated in one
or more other figures to produce embodiments that are not
explicitly illustrated or described. The combinations of features
illustrated provide representative embodiments for various
applications. Various combinations and modifications of the
features consistent with the teachings of this disclosure, however,
could be desired for particular applications or
implementations.
* * * * *