A method of performing ultrasonic stir welding uses a welding head assembly to include a plate and a rod passing through the plate. The rod is rotatable about a longitudinal axis thereof. In the method, the rod is rotated about its longitudinal axis during a welding operation. During the welding operation, a series of on-off ultrasonic pulses are applied to the rod such that they propagate parallel to the rod's longitudinal axis. At least a pulse rate associated with the on-off ultrasonic pulses is controlled

Ding, R. Jeffrey

NASA Technical Reports Server

(12) United States Patent 
Ding 
(54) PULSED ULTRASONIC STIR WELDING 
METHOD 
(75) Inventor: R. Jeffrey Ding, Athens, AL (US) 
(73) Assignee: The United States of America as 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, DC (US) 
(*) Notice: 	 Subject to any disclaimer, the term of this 
patent is extended or adjusted under 35 
U.S.C. 154(b) by 0 days. 
(21) Appl. No.: 13/523,310 
(22) Filed: 	 Jun. 14, 2012 
Related U.S. Application Data 
(62) Division of application No. 13/240,075, filed on Sep. 
22, 2011. 
(51) Int. Cl. 
B23K 1106 	 (2006.01) 
B23K 20112 	 (2006.01) 
(52) U.S. Cl . ..................... 228/112.1; 228/113; 228/114; 
228/2.1; 228/110.1; 228/1.1; 228/111 
(58) Field of Classification Search ............... 228/110.1, 
228/1.1, 111, 112.1, 113, 114, 2.1 
See application file for complete search history. 
(1o) Patent No.: 	 US 	 8,393,523 B1 
(45) Date of Patent: 	 Mar. 12, 2013 
(56) References Cited 
U.S. PATENT DOCUMENTS 
2005/0242066 Al * 11/2005 Statnikov ................... 219/76.13 
FOREIGN PATENT DOCUMENTS 
JP 	 2005028382 A * 2/2005 
OTHER PUBLICATIONS 
Computer english translation of JP 2005028382 A.* 
* cited by examiner 
Primary Examiner Erin Saad 
(74) Attorney, Agent, or Firm Peter J. Van Bergen; James 
J. McGroary 
(57) ABSTRACT 
A method of performing ultrasonic stir welding uses a weld-
ing head assembly to include a plate and a rod passing through 
the plate. The rod is rotatable about a longitudinal axis 
thereof. In the method, the rod is rotated about its longitudinal 
axis during a welding operation. During the welding opera-
tion, a series of on-off ultrasonic pulses are applied to the rod 
such that they propagate parallel to the rod's longitudinal 
axis. At least a pulse rate associated with the on-off ultrasonic 
pulses is controlled. 
14 Claims, 2 Drawing Sheets 
34 
Controller 
f A PR 
Ultrasonic 
Energy 
Source 
30 
40 	 42 
Ultrasonic 
Energy 
Source 
44 	 f A PR 
Controller 
300 
Movement 
100 
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US 8,393,523 B1 
1 
PULSED ULTRASONIC STIR WELDING 
METHOD 
CROSS-REFERENCES TO RELATED 
APPLICATIONS 
This application is a divisional application of U.S. patent 
application Ser. No. 13/240,075, filed on Sep. 22, 2011. 
ORIGIN OF THE INVENTION 	 10 
The invention described herein was made by an employee 
of the United States Government and may be manufactured 
and used by or for the Government of the United States of 
America for governmental purposes without the payment of 15 
any royalties thereon or therefor. 
BACKGROUND OF THE INVENTION 
1. Field of the Invention 	 20 
This invention relates to stir welding methods. More spe-
cifically, the invention is a stir welding method utilizing 
pulsed ultrasonic energy. 
2. Description of the Related Art 
Stir welding is a form of welding that utilizes a small stir 25 
pin to mix abutting or faying surfaces of two pieces of mate-
rial (e.g., metal materials) to thereby form a jointbetween the 
two pieces of material. The materials must be heated into a 
plastic state where they abut prior to being "stirred." There are 
several ways to achieve such heating. In one type of stir 30 
welding known as friction stir welding (FSW), a pin tool 
includes a larger diameter shoulder and a smaller diameter 
threaded pin. The entire pin tool i s rotated and the rotating pin 
is driven axially into the weld j oint until the rotating shoulder 
comes into contact with the material surface. The rotating 35 
shoulder generates frictional energy/heat as it rotates on the 
material surface to thereby heat the material into its plastic 
state. The high rotation rates needed to generate the frictional 
forces, as well as the frictional forces, tend to wear out the pin 
tool in relatively short periods of time especially when j oining 40 
thick sections of temperature-resistant alloys such as titanium 
and steel. 
SUMMARY OF THE INVENTION 
45 
Accordingly, it is an object of the present invention to 
provide a stir welding method. 
Another object of the present invention is to provide a stir 
welding method that increases tool life. 
Other objects and advantages of the present invention will 50 
become more obvious hereinafter in the specification and 
drawings. 
In accordance with the present invention, a method of 
performing ultrasonic stir welding uses a welding head 
assembly to include a plate and a rod passing through the 55 
plate. The rod is rotatable about a longitudinal axis thereof. In 
the method, the rod is rotated about its longitudinal axis 
during a welding operation. A series of on-off ultrasonic 
pulses are applied to the rod as it rotates such that the on-off 
ultrasonic pulses propagate parallel to the rod's longitudinal 60 
axis. At least a pulse rate associated with the on-off ultrasonic 
pulses is controlled. 
BRIEF DESCRIPTION OF THE DRAWING(S) 
65 
Other objects, features and advantages of the present 
invention will become apparent upon reference to the follow- 
2 
ing description of the preferred embodiments and to the draw-
ings, wherein corresponding reference characters indicate 
corresponding parts throughout the several views of the draw-
ings and wherein: 
FIG. 1 is a schematic view of an ultrasonic stir welding 
system used to implement an embodiment of the present 
invention; and 
FIG. 2 is a schematic view of an ultrasonic stir welding 
system used to implement another embodiment of the present 
invention. 
DESCRIPTION OF THE PREFERRED 
EMBODIMENT(S) 
Referring now to the drawings and more particularly to 
FIG. 1, an ultrasonic stir welding (USW) system used to 
implement an embodiment of the present invention is shown 
and is referenced generally by numeral 10. USW system 10 
will be used to weld two abutting material surfaces that are not 
shown in order to more clearly illustrate the elements used by 
the method of the present invention. 
USW system 10 includes a welding head assembly 12 
defined by a containment plate 14 and a stir pin or rod 16 that 
will generally pass through containment plate 14. Stir rod 16 
can be a substantially cylindrical rod that is capable of rota-
tion about its longitudinal axis 16A while plate 14 either 
remains stationary, rotates at the same speed as stir rod 16, or 
rotates at a different speed than stir rod 16. Rotational motion 
of stir rod 16 is indicated by rotational arrow 18 and will occur 
during a stir welding operation as would be understood by one 
of ordinary skill in the art. Stir rod 16 is made from a rigid 
material (e.g., metal) that can withstand the rigors of a stir 
welding operation. Such materials are well known in the art of 
stir welding. Further, the particular motor/system used to 
provide rotation of stir rod 16 relative to plate 14 is not a 
limitation of the present invention. 
In accordance with the present invention, an ultrasonic 
source 20 capable of generating ultrasonic energy is coupled 
to stir rod 16. The frequency of the ultrasonic energy is not a 
limitation of the present invention, but generally frequencies 
up to approximately 100 KHz would be sufficient for most 
applications. During a welding operation with plate 14 abut-
ting a work piece's surface and rotating stir rod 16 embedded 
in the work piece, ultrasonic source 20 is controlled in such a 
way that on-off pulses (indicated by dashed line 22) of ultra-
sonic energy produced by source 20 are applied to stir rod 16. 
More specifically, ultrasonic pulses 22 are applied to stir rod 
16 as it rotates in a work piece such that pulses 22 propagate 
along or parallel to longitudinal axis 16A. 
The application of ultrasonic energy to rotating stir rod 16 
enhances the heating of the work piece to its plastic state that 
is required for the welding operation. This reduces the rota-
tional rates required for stir rod 16 thereby improving tool 
life. In addition, the application of ultrasonic energy to rotat-
ing stir rod 16 reduces the frictional forces between rotating 
stir rod 16 and the work piece in which it rotates. While this 
also improves tool life, constant application of the ultrasonic 
energy is detrimental to the stirwelding operation. That is, the 
stir welding operation requires that rotating stirrod 16 "stick" 
to plasticized work piece material just forward of stir rod 16 
with the "sticking" plasticized work piece material then being 
rotated or moved to just aft of stir rod 16 where it is released 
back into the work piece. However, constant application of 
ultrasonic energy to rotating stir rod 16 reduces this "stick-
ing" attribute as the frictional forces are reduced between 
rotating stir rod 16 and the plasticized work piece thereby 
comprising the quality of the weld. The present invention 
US 8,393,523 B1 
3 
	
4 
overcomes this problem by applying the ultrasonic energy to 	 reducing frictional forces generated by relative movement 
rotating stir rod 16 in the form of pulses 22. During the "on" 
	
300. Note that some materials and/or applications may 
period of pulses 22, the work piece is being heated while 	 require an additional heat source 50 properly positioned 
frictional forces acting on rotating stir rod 16 are reduced. 	 based on relative movement 300 for heating the material(s) to 
During the "off' period of pulses 22, the plasticized work 5 be welded into a plastic state. Each of controllers 34 and 44 
piece material "sticks" to rotating stir rod 16 so it can be 	 can employ open-loop or closed-loop control where closed- 
moved and released just aft of stir rod 16. 	 loop control could utilize inputs from sensors "S" included in 
Ultrasonic pulses 22 can be controlled during a welding 	 plate 14 as described above. 
operation. The controllable parameters of pulses 22 include 	 The advantages of the present invention are numerous. Stir 
the frequency of the ultrasonic energy, the amplitude of the io welding tool life will be increased as the use of ultrasonic 
ultrasonic energy, and the on-off pulse rate of pulses 22. Such 	 energy applied during welding reduces frictional forces act- 
control can be provided by a controller 24 coupled to source 	 ing on the tool. By pulsing the ultrasonic energy, the stir 
20 where controller 24 can adjust the frequency (f) and/or 	 welding tool is "pulsed" between its heating/friction reduc- 
amplitude (A) of the ultrasonic energy as well as the pulse rate 	 tion and welding functions. Additional pulsed ultrasonic 
(PR) of pulses 22. The particular construction and/or arrange-  15 energy can be applied to the tool's containment plate and/or 
ment of source 20 and controller 24 are not limitations of the 	 the base/anvil on which the work piece sits to enhance heating 
present invention. For example, source 20 and controller 24 	 and reduce frictional forces generated during a stir welding 
could be an integrated device or separate devices without 	 operation. 
departing from the scope of the present invention. 	 Although the invention has been described relative to a 
Controller 24 could employ pre-programmed or open-loop 20 specific embodiment thereof, there are numerous variations 
control of pulses 22, or could employ an adaptable closed- 	 and modifications that will be readily apparent to those 
loop control of pulses 22. For example, in terms of closed- 	 skilled in the art in light of the above teachings. It is therefore 
loop control, one or more sensors "S" could be included with 	 to be understood that, within the scope of the appended 
plate 14 (and/or stir rod 16) to sense attributes (e.g., tempera- 	 claims, the invention may be practiced other than as specifi- 
ture) of the work piece in the region of stir rod 16. The sensed 25 cally described. 
attributes could then be used by controller 24 to adjust the 	 What is claimed as new and desired to be secured by 
attributes of pulses 22 to improve the welding operation. 	 Letters Patent of the United States is: 
A system that can be used to implement another embodi- 	 1. A method of performing ultrasonic stir welding, com- 
ment of the method of the present invention is illustrated in 	 prising the steps of: 
FIG. 2 where identical reference numerals are used for ele-  30 providing a welding head assembly to include a plate and a 
ments common to those described above. In FIG. 2, a work 	 rod passing through said plate wherein said rod is rotat- 
piece to be welded is shown and is referenced by numeral 100 	 able about a longitudinal axis thereof, said rod being in 
and a base or anvil supporting work piece 100 is referenced by 	 contact with a work piece to be welded; 
numeral 200. Similar to plate 14, base 200 is made from a 	 rotating said rod about said longitudinal axis thereof during 
rigid material that can withstand the rigors of an ultrasonic stir 35 	 a welding operation wherein said work piece is plasti- 
welding operation of the present invention. A drive source 26 	 cized adjacent said rod with a first region of said work 
coupled to stir rod 16 provides rotation 18 needed for a 	 piece plasticized and in contact with said rod being 
welding operation. 	 forward of said rod and a second region of said work 
During a welding operation, relative movement (indicated 	 piece plasticized and in contact with said rod being aft of 
by arrow 300) is induced between welding head assembly 12 40 	 said rod; 
and work piece 100 where movement 300 is generally per- 	 applying a series of on-off ultrasonic pulses to said rod as 
pendicular to longitudinal axis 16A of rotating stir rod 16. 	 said rod rotates about said longitudinal axis thereof such 
Work piece 100 can remain stationary on base 200 as welding 	 that said on-off ultrasonic pulses propagate parallel to 
head assembly 12 moves in accordance with arrow 300, or 	 said longitudinal axis of said rod; and 
welding head assembly 12 and base 200 can remain station-  45 	 controlling at least a pulse rate associated with said on-off 
ary while work piece 100 is moved in accordance with arrow 	 ultrasonic pulses during said step of rotating wherein 
300. 	 said pulse rate is selected such that said first region of 
Regardless of how relative movement 300 is induced, the 	 said work piece plasticized sticks to said rod and said 
embodiment in FIG. 2 includes one or more additional ultra- 	 second region of said work piece plasticized is released 
sonic energy sources. In the illustrated embodiment, two 50 	 from said rod. 
ultrasonic energy sources 30 and 40 are provided with corre- 	 2. A method according to claim 1, further comprising the 
sponding controllers 34 and 44. Source 30/controller 34 	 step of controlling at least one of frequency and amplitude 
cooperate to produce/apply ultrasonic pulses 32 to plate 14 in 	 associated with said on-off ultrasonic pulses. 
a direction parallel to relative movement 300 (or perpendicu- 3. A method according to claim 1, wherein said step of 
lar to longitudinal axis 16A of stir rod 16). Controller 34 can 55 controlling is accomplished using a closed-loop control sys-
control frequency (F), amplitude (A), and/or pulse rate (PR) tem. 
of pulses 32 where the particular attribute values can be 	 4. A method according to claim 2, wherein said steps of 
independent of those associated with pulses 22. Similarly, 	 controlling are accomplished using a closed-loop control sys- 
source 40/controller 44 cooperate to produce/apply ultrasonic 	 tem. 
pulses 42 to base 200 such that pulses 42 propagate in base 60 	 5. A method of performing ultrasonic stir welding, com- 
200 in a direction parallel to relative movement 300 (or per- 	 prising the steps of: 
pendicular to longitudinal axis 16A of stir rod 16). Controller 	 providing a stationary base; 
44 can control frequency (F), amplitude (A), and/or pulse rate 	 providing a welding head assembly to include a plate 
(PR) of pulses 42 where the particular attribute values can be 	 spaced apart from said base and a rod with an end of said 
independent of those associated with pulses 22 and pulses 32. 65 	 rod spaced apart from said base, said rod passing 
The application of pulses 32 and/or 42 during a welding 	 through said plate wherein said rod is rotatable about a 
operation enhances heating of work piece 100 while also 	 longitudinal axis thereof, 
US 8,393,523 B1 
5 
rotating said rod about said longitudinal axis thereof during 
a welding operation; 
applying a series of on-off ultrasonic pulses to said rod as 
said rod rotates about said longitudinal axis thereof such 
that said on-off ultrasonic pulses propagate parallel to 5 
said longitudinal axis of said rod; and 
applying additional on-off ultrasonic pulses to at least one 
of said base and said plate as said rod rotates such that 
said additional on-off ultrasonic pulses propagate per- io 
pendicular to said longitudinal axis of said rod. 
6. A method according to claim 5, further comprising the 
step of controlling a pulse rate associated with said on-off 
ultrasonic pulses. 
7. A method according to claim 6, wherein said step of 15 
controlling is accomplished using a closed-loop control sys-
tem. 
8. A method according to claim 6, further comprising the 
step of controlling at least one of frequency and amplitude 
associated with said on-off ultrasonic pulses.  
6 
9. A method according to claim 8, wherein said steps of 
controlling are accomplished using a closed-loop control sys-
tem. 
10. A method according to claim 5, further comprising the 
step of controlling a pulse rate associated with said additional 
on-off ultrasonic pulses. 
11. A method according to claim 10, wherein said step of 
controlling is accomplished using a closed-loop control sys-
tem. 
12. A method according to claim 10, further comprising the 
step of controlling at least one of frequency and amplitude 
associated with said additional on-off ultrasonic pulses. 
13. A method according to claim 12, wherein said steps of 
controlling are accomplished using a closed-loop control sys-
tem. 
14. A method according to claim 5, wherein a material to be 
welded resides between said base and said plate, said method 
further comprising the step of heating the material to a plastic 
state thereof. 


Pulsed ultrasonic stir welding method

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