View source for Rotary friction welding

{{Multiple issues|
{{cleanup rewrite|date=January 2024}}
{{cleanup reorganize|date=January 2024}}
{{external links|date=January 2024}}
}}

{{Short description|Spinning one metal workpiece against another to join them}}
'''Rotary friction welding''' (RFW) one of the methods of [[friction welding]], the classic way of which uses the [[Work (physics)|work of friction]] to create a not separable [[Welding|weld]]. Typically one welded element is rotated relative to the other and to the forge (pressed down by axial force). The heating of the material is caused by friction work and creates a permanent connection. In this method, the materials to be welded can be the same, dissimilar, composite<ref name=":22">{{Cite journal|last1=Siedlec|first1=Robert|last2=Strąk|first2=Cezary|date=2020-10-10|title=Rotary friction welding of Al/Al2O3 Composites with Aluminium Alloys|url=http://www.pspaw.pl/index.php/pspaw/article/view/1124|journal=Welding Technology Review|language=en|volume=92|issue=6|pages=23–34|doi=10.26628/wtr.v92i6.1124|issn=2449-7959|doi-access=free}}</ref> or non-metallic materials. Friction welding methods of are often considered as solid-state welding.

== History ==
[[File:Historical photo of double spindle machine..jpg|thumb|Historical photo of double spindle machine.|282x282px]]
[[File:Friction Welding History, Техника - молодёжи 1958-02, страница 32, О. КАРЫШЕВ, Ленинград.jpg|thumb|299x299px|Friction welding description in the newspaper [[Tekhnika Molodezhi|Техника - молодёжи]] 1958-02, страница 32 from 1958 year .<ref>{{Cite web |title=Техника молодежи №2 - 1958 |url=https://djvu.online/file/DWSlJd5Jz1L1f |access-date=2023-12-21 |website=djvu.online |language=ru}}</ref><ref name=":34" />However, the newspaper is about technical [[science fiction]].

]]
Some applications and patents connected with friction welding date back to the turn of the 20th century,<ref name=":17" /> and rotary friction welding is the oldest of these methods.<ref name=":18">{{Cite journal|last=J. LOPERA|first=K. MUCIC, F. FUCHS, N. ENZINGER|date=October 2012|title=Linear Friction Welding Of High Strength Chains: Modelling And Validation|url=https://www.researchgate.net/publication/292091334|journal=Mathematical Modelling of Weld Phenomena|volume=10}}</ref> W. Richter patented the method of the linear friction welding (LFW) process in 1924 in [[England]] and 1929 in the [[Weimar Republic]]; however, the description of the process was vague<ref name=":18" /> and H. Klopstock patented the same process in the [[Soviet Union]] in 1924.<ref name=":19">{{Cite web|last=Mehmet UZKUT|first=Bekir Sadık ÜNLÜ, Selim Sarper YILMAZ, Mustafa AKDAĞ|title=Friction Welding And Its Applications In Today's World|url=https://core.ac.uk/download/pdf/153447357.pdf}}</ref> But the first description and experiments related to rotary friction welding took place in the Soviet Union in 1956,<ref name=":17" /><ref name=":19" /> by a machinist named A. J. Chudikov (А. И. Чудиков<ref name=":34">{{Cite web|title=СВАРКА * ТРЕНИЕУЧ * ИСТОРИЯ ОДНОГО ПИСЬМА * НЕОБЫЧАЙНАЯ СУДЬБА ПОЛЕЗНОГО СПОСОБА * НАУЧНОЕ ОБОСНОВАНИЕ - Техника - молодёжи 1958-02, страница 32|url=http://zhurnalko.net/=nauka-i-tehnika/tehnika-molodezhi/1958-02--num32|access-date=2021-04-18|website=zhurnalko.net|language=Ru}}</ref>), who after researching a myriad of scientific studies, suggested the use of this welding method as a commercial process.<ref name=":19" /> At first he discovered the method by accident in the [[Elbrussky]] mine where he worked: Chudikov did not pay enough attention to lubricating the lathe chuck's insides and then learned he had welded the workpiece to the lathe.<ref name=":34" /> He wondered if this accident could be used for joining and came to conclusion that it was necessary to work at high rotation speeds ({{as of|2023|lc=y}} about 1000 revolutions per second), immediately brake and press down welded components.<ref name=":34" /> He decided to write a letter to the [[Ministry of Ferrous Metallurgy|Ministry of Metallurgy]] and received the answer that this welding was inappropriate, but short notes about the method were published in the newspapers of the Union, arousing interest from Yu. Ya. Terentyeva who was manager of the national Scientific Research Institute of Electrical Welding Equipment, and with time Chudikov's method was disseminated.<ref name=":34" /> The process was introduced to the [[United States]] in 1960.<ref name=":17" /> The American companies [[Caterpillar Inc.|Caterpillar Tractor Company]] ([[Caterpillar Inc.|Caterpillar - CAT]]), [[Rockwell International]], and [[American Machine and Foundry|American Manufacturing Foundry]] all developed machines for this process. Patents were also issued throughout [[Europe]] and the former Soviet Union. The first studies of friction welding in England were carried out by [[the Welding Institute]] in 1961.<ref name=":19" /> The US through [[Caterpillar Inc.|Caterpillar Tractor Company]] and MTI developed an inertia process in 1962.<ref name=":17" /><ref name=":19" /> Europe through [[KUKA|KUKA AG]] and Thompson launched rotary friction welding for industrial applications in 1966, developed a direct-drive process and in 1974 built the rRS6 double spindle machine for heavy truck axles.<ref name=":21">{{Cite web|title=Rotary friction welding machines|url=https://www.kuka.com/en-us/products/production-machines/rotary-friction-welding-machines|access-date=2020-12-27|website=KUKA AG|language=en-US}}</ref><ref>{{Cite web|title=KUKA brochure|url=https://www.swisslog.com/-/media/swisslog/documents/corporate/events/10_vorstellung_kuka-aktiengesellschaft_andreas-bauer.pdf|access-date=2021-05-29|website=www.swisslog.com}}</ref>

newIn 1997, an international patent application was filed, entitled "Method of Friction Welding Tubular Members". Inventor A. Graham demonstrated, on welding pipes with a diameter of 152.4&nbsp;mm, a method that uses radial friction welding with an intermediate ring for connecting long pipes,<ref name=":26">{{Cite journal|date=2019-04-01|title=Full-scale friction welding system for pipeline steels|journal=Journal of Materials Research and Technology|language=en|volume=8|issue=2|pages=1773–1780|doi=10.1016/j.jmrt.2018.12.007|issn=2238-7854|doi-access=free|last1=Chludzinski|first1=Mariane|last2=Dos Santos|first2=Rafael Eugenio|last3=Pissanti|first3=Daniela Ramminger|last4=Kroeff|first4=Filipe Cantelli|last5=Mattei|first5=Fabiano|last6=Dalpiaz|first6=Giovani|last7=Piza Paes|first7=Marcelo Torres}}</ref><ref>{{Cite patent|title=A method of friction welding tubular members|pubdate=2000-12-07|country=AU|number=727311|assign=[[Stolt Offshore|Stolt Offshore Ltd.]]|inventor1-last=Hutt|inventor1-first=Graham Anthony}}</ref> at long last succeeding after some attempts occurred in 1975,<ref name=":12" /> and after scientists in [[Leningrad]] theorized on the idea in newspapers.<ref name=":34" /> Another method was invented and experimentally proven at [[The Welding Institute]] (TWI) in the [[United Kingdom|UK]] and patented in 1991, called the [[friction stir welding]] (FSW) process.<ref name=":16" /> In 2008 [[KUKA|KUKA AG]] developed the SRS 1000 rotary friction welding machine with a forging force of 1000 tons.<ref name=":21" /> An improved modification is Low Force Friction Welding, a hybrid technology developed by EWI and [https://www.mtiwelding.com/ Manufacturing Technology Inc. (MTI)]. The process can apply to both linear and rotary friction welding.<ref name=":20" /> {{As of|2020}} [[KUKA]] has been operating in 44 countries and has built more than 1200 systems,<ref name=":21" /><ref>{{Citation|title=Rotary friction welding – a process with a future| date=23 October 2020 |url=https://www.youtube.com/watch?v=X9i8jN-lWAQ|language=en|access-date=2021-05-29}}</ref> including for subcontract facilities;<ref>{{Citation|title=Thompson Friction Welding – Industrial Expertise in the Heart of The Black Country| date=4 June 2021 |url=https://www.youtube.com/watch?v=xrZ_jxpQLng|language=en|access-date=2021-06-09}}</ref>[[File:Some of KUKA friction welding machines.png|thumb|375x375px|Some of KUKA friction welding machines.|center]]
However, there are more companies in the world with experience; for example, [[The Welding Institute]] TWI has more than 50 years of expertise and insight inherent to process development.<ref>{{Cite web|title=Rotary Friction Welding|url=https://www.twi-global.com/what-we-do/research-and-technology/technologies/welding-joining-and-cutting/friction-welding/rotary-friction-welding.aspx|access-date=2021-05-29|website=www.twi-global.com|language=en-GB}}</ref> {{As of|2023}}, with the help of more and more companies, friction welding has become popular worldwide with various materials both in scientific studies and industrial applications.{{citation needed|date=March 2023}}[[File:FWT 30.ogg|thumb|375x375px|FWT 30 EWI welder [https://www.youtube.com/watch?v=nGkM7umkoyY&ab_channel=ManufacturingTechnologyInc%28MTI%29]|center]]

== Applications ==
Rotary friction welding is widely implemented across the manufacturing sector and has been used for numerous applications,<ref>{{Cite web|title=Rotary Friction Welding - Job Knowledge|url=https://www.twi-global.com/technical-knowledge/job-knowledge/rotary-friction-welding-148.aspx|access-date=2020-12-27|website=www.twi-global.com|language=en-GB}}</ref><ref name=":32">{{Cite web|title=KUKA brochure|url=https://www.kuka.com/-/media/kuka-downloads/imported/9cb8e311bfd744b4b0eab25ca883f6d3/kuka_brochure_friction-welding.pdf|access-date=2021-03-05|website=KUKA AG|language=en-US}}</ref><ref>{{Cite web |title=All Geometry Sample Parts |url=https://www.mtiwelding.com/parts/ |access-date=2023-12-08 |website=MTI Welding |language=en-US}}</ref> including:

* Parts in gas turbine such as: turbine shafts, turbine discs, compressor drums,<ref name=":36">{{Citation|title=NMIS-AFRC with Rolls-Royce on the rotary friction revolution| date=2 June 2021 |url=https://www.youtube.com/watch?v=v6-rBcg0sv4|language=en|access-date=2021-06-09}}</ref>
*Automotive parts including steel [[Axle track|truck axles]]<ref>{{Citation |title=Axles Friction welding machine | date=10 October 2016 |url=https://www.youtube.com/watch?v=_i_00I2gBmc |access-date=2023-12-07 |language=en}}</ref>  and casings, [[overhead valve engine]],<ref>{{Citation |title=FRICTION WELDING AUTO LOADING MACHINE | date=20 January 2015 |url=https://www.youtube.com/watch?v=sdPR_U6IvNA |access-date=2023-12-10 |language=en}}</ref> motor hollow pistons, passenger car wheel rims, converter for passenger car automatic gears, [[Drive shaft|drive shafts]],<ref>{{Citation |title=FWT 60-Ton Direct Drive Friction Welder | date=6 March 2023 |url=https://www.youtube.com/watch?v=S_5EkgnzpHs&t=273s |access-date=2023-12-07 |language=en}}</ref> yoke shaft<ref>{{Citation |title=FWT 60-Ton Direct Drive Friction Welder | date=6 March 2023 |url=https://www.youtube.com/watch?v=S_5EkgnzpHs&t=157s |access-date=2023-12-07 |language=en}}</ref> 
*Turbine for aircraft engine,<ref name=":25">{{Cite web|last=Maude|first=Dudley|title=Inerita friction welding of turbine-engine components l Reibschweißen von Turbinenkomponenten (2008) - video Dailymotion|url=https://www.dailymotion.com/video/x2p41ka|access-date=2021-02-16|website=Dailymotion|date=5 May 2015 |language=en-US}}</ref>
* Monel to steel marine fittings,
* [[Piston rod]]s,
* [[Copper]] - [[aluminium]] electrical connections,
*Heat exchangers,
* Cutting tools for example for lengthening [[Drill bit|drill bits]],<ref>{{Citation |title=FWT 3-Ton Direct Drive Friction Welder for Drill Bits | date=6 April 2023 |url=https://www.youtube.com/watch?v=35cwK3kRS8g |access-date=2023-11-30 |language=en}}</ref> 
*Drill pipes,<ref>{{Cite web|title=Rotary friction welding for geothermal applications|url=https://www.twi-global.com/media-and-events/press-releases/2020/friction-welding-for-geothermal-applications|access-date=2021-01-05|website=www.twi-global.com|language=en-GB}}</ref>
*Reactor pressure vassels nozzles,<ref name=":36" /><ref>{{Cite journal |last1=Banerjee |first1=Amborish |last2=Ntovas |first2=Michail |last3=Da Silva |first3=Laurie |last4=Rahimi |first4=Salaheddin |date=14 July 2022 |title=Microstructure and mechanical properties of dissimilar inertia friction welded 316L stainless steel to A516 ferritic steel for potential applications in nuclear reactors |journal=Manufacturing Letters |volume=33 |pages=33–37 |doi=10.1016/j.mfglet.2022.07.002 |s2cid=250516592 |issn=2213-8463|doi-access=free }}</ref>
*Tubular transition joints combining dissimilar metals ([[Aluminium]] - [[Titanium]] and Aluminium - [[Stainless steel]]),
*Potential for medical applications,<ref name=":23">{{Cite web|title=Rotary friction welding for medical application|url=https://www.twi-global.com/media-and-events/insights/rotary-friction-welding-for-medical-application|access-date=2021-01-05|website=www.twi-global.com|language=en-GB}}</ref><ref name=":38">{{Cite journal |last=A.K. Nasution, H. Gustami, S. Suprastio, M.A. Fadillah, J. Octavia, S. Saidin |date=2022-06-28 |title=Potential use of Friction Welding for Fabricating Semi-Biodegradable Bone Screws |journal=International Journal of Automotive and Mechanical Engineering |volume=19 |issue=2 |pages=9660–9667 |url=https://103.53.35.75/ijame/article/view/7087 |doi=10.15282/ijame.19.2.2022.03.0745 |doi-access=free}}</ref>
*For learning students at technical universities.

=== Connections geometry ===
[[File:Basic cross sections connections of rotary friction welding..jpg|thumb|391x391px|Basic cross sections of rotary friction welding connections.<ref name=":15" />|center]]Rotary Friction Welding can join a wide range of part geometries Typically: 
Tube to Tube, Tube to Plate, Tube to Bar, Tube to Disk, Bar to Bar, Bar to Plate and in addition, to this a rotating ring is used to connect long components.<ref name=":0" />[[File:Example modification friction welding for components.png|thumb|391x391px|Example of modification standard rotary friction welding from research that may be applicable for long components.<ref name=":12" /><ref name=":26" />|center]]Geometry of the component surface is not always [[Flat (geometry)|flat]] for example it can be [[Cone|conical]] surface and not only.<ref name=":37" />

== Types of materials to be welded ==
Rotary friction welding enables to weld various materials.
[[File:Variety welded materials photo.png|center|thumb|288x288px|Variety welded metal materials photo.]]
[[Metal]]lic materials of the same name or dissimilar either [[Composite material|composite]],<ref name=":22" /> [[superalloy]]s<ref name=":27">{{Cite journal|last1=Rehman|first1=Ateekh Ur|last2=Usmani|first2=Yusuf|last3=Al-Samhan|first3=Ali M.|last4=Anwar|first4=Saqib|date=February 2021|title=Rotary Friction Welding of Inconel 718 to Inconel 600|journal=Metals|language=en|volume=11|issue=2|pages=244|doi=10.3390/met11020244|doi-access=free}}</ref> and non-metallic e.g. [[thermoplastic]] polymers<ref name=":02">{{Cite book|last=Troughton|first=Michael J.|url=https://books.google.com/books?id=BXL_mnDzW0QC&pg=PA49|title=Handbook of Plastics Joining: A Practical Guide|date=2008-10-17|publisher=William Andrew|isbn=9780815519768}}</ref> can be welded and even the welding of wood has been investigated.<ref>{{Cite journal |last1=Li |first1=Suxia |last2=Zhang |first2=Haiyang |last3=Shu |first3=Biqing |last4=Cheng |first4=Liangsong |last5=Ju |first5=Zehui |last6=Lu |first6=Xiaoning |date=2021 |title=Study on the Bonding Performance of the Moso Bamboo Dowel Welded to a Poplar Substrate Joint by High-Speed Rotation |url=https://www.techscience.com/jrm/v9n7/41778 |journal=Journal of Renewable Materials |language=en |volume=9 |issue=7 |pages=1225–1237 |doi=10.32604/jrm.2021.014364 |issn=2164-6341 |doi-access=free}}</ref> [[Weldability]] tables of metallic alloy can be found on the Internet and in books.<ref name=":15" /> 
[[File:Rotary friction welding weldability table..jpg|thumb|371x371px|Example of Rotary friction welding weldability table.<ref name=":15" /> This is the basic table because the currently known [[List of named alloys|list of materials]] is much larger and the name alloy systems are classified by a number system ([[American National Standards Institute|ANSI]]) or by names indicating their main alloying constituents ([[Deutsches Institut für Normung|DIN]] and [[International Organization of Standardization|ISO]]).

|center]]
Sometimes an interlayer is used to connect non-compatible materials.<ref name=":23" /><ref name=":30">{{Cite journal|last1=Cheepu|first1=Muralimohan|last2=Ashfaq|first2=M.|last3=Muthupandi|first3=V.|date=2017|title=A New Approach for Using Interlayer and Analysis of the Friction Welding of Titanium to Stainless Steel|url=https://www.researchgate.net/publication/315789072|journal=Transactions of the Indian Institute of Metals|language=en|volume=70|issue=10|pages=2591–2600|doi=10.1007/s12666-017-1114-x|s2cid=136154603|issn=0972-2815}}</ref>
[[File:RFW friction welding components indirect material.jpg|center|thumb|RFW friction welding components interlayer (indirect material).<ref name=":15" />]]

== Division due to drive motor ==
In ''direct-drive friction welding'' (also called continuous drive friction welding) the drive motor and chuck are connected. The drive motor is continually driving the chuck during the heating stages. Usually, a clutch is used to disconnect the drive motor from the chuck, and a brake is then used to stop the chuck.
[[File:Schwungradreibschweissen.ogv|thumb|Example of friction welding with flywheel.]]
In ''inertia friction welding'' the drive motor is disengaged, and the workpieces are forced together by a friction welding force. The kinetic energy stored in the rotating flywheel is dissipated as heat at the weld interface as the flywheel speed decreases. Before welding, one of the workpieces is attached to the rotary chuck along with a [[flywheel]] of a given weight. The piece is then spun up to a high rate of rotation to store the required energy in the flywheel. Once spinning at the proper speed, the motor is removed and the pieces forced together under pressure. The force is kept on the pieces after the spinning stops to allow the weld to "set".<ref name=":0">[https://www.mtiwelding.com/technologies/rotary-friction-welding/ Rotary Friction Welding], video and schematic diagram</ref>

== Stages of process ==
[[File:Steps of typical rotary friction welding v2..jpg|center|thumb|802x802px|Steps of typical rotary friction welding.]]
*Step 1 and 2, friction stage: one of the components is set in rotation, and then pressed to the other stationary one in axial of rotation,
* Step 3, braking stage: the rotating component is stopped in braking time,
* Step 4, upsetting stage: the welded elements are still forging by forge pressure (pressed down),
*Step 5: in standard RFW welding (standard parameters), a flash will be created. Outside flash can be cut off on the welder.<ref>{{Cite web|title=Thompson friction welding machines|url=https://www.kuka.com/en-gb/products/production-machines/rotational-friction-welding-machines/thompson|access-date=2020-12-25|website=KUKA AG|language=en-GB}}</ref>
[[File:Stages of process RFW welding.jpg|thumb|280x280px|Exemplary stages of typical process RFW welding on the chart,<ref name=":15" /><ref>{{Cite web|title=What is Rotary Friction Welding (RFW)?|url=https://www.linkedin.com/pulse/what-rotary-friction-welding-rfw-steve-dodds|access-date=2020-12-25|website=www.linkedin.com|language=en}}</ref><ref>{{Cite journal|last1=Stütz|first1=Markus|last2=Buzolin|first2=Ricardo|last3=Pixner|first3=Florian|last4=Poletti|first4=Cecilia|last5=Enzinger|first5=Norbert|date=May 2019|title=Microstructure development of molybdenum during rotary friction welding|url=http://dx.doi.org/10.1016/j.matchar.2019.03.024|journal=Materials Characterization|volume=151|pages=506–518|doi=10.1016/j.matchar.2019.03.024|s2cid=139878258 |issn=1044-5803}}</ref><ref name=":17">{{Cite journal|last=K. K. WANG|first=WEN LIN|date=1974|title=Flywheel Friction Welding Research|url=https://app.aws.org/wj/supplement/WJ_1974_06_s233.pdf|journal=Supplement to the Welding Journal |access-date=2 August 2024}}</ref> but there are exist modifications<ref name=":8" /><ref name=":9" /> and then time of stages do not have look like this.|center]]However, referring to the stages chart:

* modifications of the process exist,[[File:Chart comparison.png|center|thumb|761x761px|Chart comparison in several friction welding methods.[https://www.youtube.com/@mtifrictionwelding/videos An overview of the charts can be found on the MTI website.]<ref>{{Citation |title=Whiteboard Wednesday: Rotary Friction Welding Processes - Direct Drive, Inertia & Hybrid | date=5 April 2023 |url=https://www.youtube.com/watch?v=ZLVb3VbqYg8 |access-date=2023-12-07 |language=en}}</ref><ref>{{Citation |title=Whiteboard Wednesday: Traditional Friction Welding VS Low Force Friction Welding for Axles | date=25 July 2023 |url=https://www.youtube.com/watch?v=_EEySIShMa8 |access-date=2023-12-07 |language=en}}</ref>]]
*may depend on the version of the process: direct-drive, inertia friction welding, hybrid welding,<ref name=":36" />
* there are many versions of welding machines,
* many materials can are welded with not the same properties, with various geometries,
* the real life process does not have to match to the ideal settings on the welding machine.

== RFW Friction work on cylindrical rods workpieces ==
{{Expand section|date=December 2020}}<!-- uncertainty - verification needed, expansion, better mathematical description of processes during welding. -->Friction work create weld and can believe that is calculated for cylindrical workpieces from math:

Work:

(1) <math>W = M \times \alpha</math>

Moment of force ''M'' general formula:

(2) <math>M = r \times F</math>

The force F will be the frictional force ''T (F=T)'' so substituting for the formula (2):

(3) <math>M = r \times T</math>

The friction force ''T'' will be the pressure ''F'' times by the friction coefficient μ:

(4) <math>T = \mu \times F </math>

So moment of force ''M'':

(5) <math>M = r \times \mu \times F</math>

The alpha angle that each point will move with the axis of rotating cylindrical workpieces will be:

(6) <math>\alpha = 2 \pi \times n \times t</math>

So friction work:

(7) <math>W = n\times \pi \times r\times F\times \mu\times t</math> <sup>[''[[wikipedia:Verifiability|verification needed]]'']</sup>

For variable value μ over friction time:

(8) <math>W = n\times \pi \times r\times F\times \int_{0}^{t} f(\mu) \,dt</math>

This requires verification but from the equation it appears that turnover and force (or [[pressure]] on surface <math>F = p (\text{pressure}) * A (\text{area})</math>) is linear to [[Work (physics)|friction work]] (W) so for example if the pressure increases 2 times then the friction work also increase 2 times, if the turnover increase 2 times then the friction work also increase 2 times and referring to [[conservation of energy]] this can heat 2 times the material to the same temperature or the temperature may increase 2 times. Pressure has the same effect over the entire surface but rotation has more impact away from the axis of rotation because it is a rotary motion. Referring to thermal conductivity the friction time affects to the flash size when shorter time was used then friction work is more concentrated in a smaller area.{{Verify source|date=September 2022}}

or variable values μ, n, F over friction time:

(9) <math>W = \pi \times r\times \int_{0}^{t} f(\mu) f(n) f(F) \,dt</math>{{Verify source|date=September 2022}}

* [[Time|t]] [<nowiki/>[[Second|s]]]- time of friction (when piece rotary),
*μ - [[coefficient of friction]],
* [[Force|F]] [<nowiki/>[[Newton (unit)|N]]]- pressure force,
* [[Radius|r]] [<nowiki/>[[Metre|m]]]- [[radius]] of workpiece,
* n [1/s] - turnover per second,
* [[Work (physics)|W]] [<nowiki/>[[Joule|J]]] - [[Work (physics)|friction work]].
[[File:Simplified welding process in the picture v2.jpg|thumb|537x537px|Simplified welding process on the picture.<ref name=":17" />|center]]

Therefore, the calculation in this way is not reliable in real is complicated. An example article considering the variable depends on the temperature coefficient of friction steel - aluminum Al60611 - [[Alumina]] is described by authors from Malaysia in for example [https://www.researchgate.net/publication/262512682_Evaluation_of_Properties_and_FEM_Model_of_the_Friction_Welded_Mild_Steel-Al6061-Alumina this paper "Evaluation of Properties and FEM Model of the Friction Welded Mild Steel-Al6061-Alumina]"<ref name=":33">{{Cite journal|last1=Seli|first1=Hazman|last2=Awang|first2=Mokhtar|last3=Ismail|first3=Ahmad Izani Md.|last4=Rachman|first4=Endri|last5=Ahmad|first5=Zainal Arifin|date=2012-12-18|title=Evaluation of properties and FEM Model of the Friction welded mild Steel-Al6061-Alumina|journal=Materials Research|volume=16|issue=2|pages=453–467|doi=10.1590/s1516-14392012005000178|issn=1980-5373|doi-access=free}}</ref> and based on this position someone created no step by step but whatever an [https://www.youtube.com/watch?v=12TdrBzCvX4 instructional simulation video] in [[abaqus]] software and in [https://www.researchgate.net/publication/262512682_Evaluation_of_Properties_and_FEM_Model_of_the_Friction_Welded_Mild_Steel-Al6061-Alumina this paper] is possible to find the selection of the mesh type in the simulation described by the authors and there are some instructions such as use the Johnson-Cook material model choice, and not only, there is dissipation coefficient value, friction welding condition, the article included too the physical formulas related to rotary friction welding described by the authors such as: heat transfer equation and convection in rods, equations related to deformation processes.<ref name=":33" /> Article included information on the parameters of authors research, but it is not a step by step and simple instruction such as also [https://www.youtube.com/watch?v=12TdrBzCvX4 the video] and good add that it is not the only one position in literature. The conclusion include information that: ''"Even though the FE model proposed in this study cannot replace a more accurate analysis, it does provide guidance in weld parameter development and enhances understanding of the friction welding process, thus reducing costly and time consuming experimental approaches."''<ref name=":33" />

The coefficient of friction changes with temperature and there are a number of factors internal friction ([[viscosity]] - e.g. '''Dynamic viscosity''' according to [[Carreau fluid|Carreau's fluid law]]<ref>{{Cite web|title=Friction Welding Simulation Software {{!}} Software Virtua RFW|url=https://www.sampro-software.net/software-virtua-rfw|access-date=2020-12-27|website=sampro|language=de}}</ref>), forge, properties of the material during welding are variable, also there is plastic deformation.

Carreau's fluid law:

[[Generalized Newtonian fluid]] where viscosity, <math>
\mu_{\operatorname{eff}}</math>, depends upon the [[shear rate]], <math>\dot \gamma</math>, by the following equation:

(10) <math>\mu_{\operatorname{eff}}(\dot \gamma) = \mu_{\operatorname{\inf}} + (\mu_0 - \mu_{\operatorname{\inf}}) \left(1+\left(\lambda \dot \gamma\right) ^2 \right) ^ {\frac {n-1} {2}}</math>

Where:

* <math>\mu_0</math>, <math>\mu_{\operatorname{\inf}}</math>, <math>\lambda</math> and <math>n</math> are material coefficients.
* <math>\mu_0</math> = viscosity at zero shear rate (Pa.s)
* <math>\mu_{\operatorname{\inf}}</math> = viscosity at infinite shear rate (Pa.s)
* <math>\lambda</math> = relaxation time (s)
* <math>n</math> = power index
Modelling of the frictional heat generated within the RFW process can be realized as a function of conducted frictional work and its dissipation coefficient, incremental frictional work of a node 𝑖 on the contacting surface can be described as a function of its axial distance from the rotation centre, current frictional [[shear stress]], rotational speed and incremental time.<ref name=":24">{{Cite news|author=B. A. Behrens, A. Chugreev, C. Kock, K. Brunotte, T. Matthias and H. Wester|date=2020|title=FE-simulation of rotary friction welding process considering thermomechanical-metallurgical coupling|work=Institute of Forming Technology and Machines, Leibniz University of Hannover, Garbsen|url=https://www.pzh.uni-hannover.de/fileadmin/pzh-ifum/Dasifum/Paper_RFW_Numiform_final.pdf|access-date=}}</ref> The dissipation coefficient <big>𝛽<sub>FR</sub></big> is often set to 0.9 meaning that 90% of frictional work is dissipated into heat.<ref name=":24"/>

(11) <big>𝑑𝑞<sub>FR</sub>(𝑖) = 𝛽<sub>FR</sub> ∙ 𝑑𝑊<sub>FR</sub>(𝑖) = 𝛽<sub>FR</sub> ∙ 𝜏𝑅(𝑖) ∙ 𝜔 ∙ 𝑟𝑖 ∙ 𝑑𝑡</big> on contacting surface of node 𝑖<ref name=":24" />

*𝛽<sub>FR</sub> - dissipation coefficient,
* 𝑊<sub>FR</sub> - frictional work,
* 𝑟𝑖 - distance from the rotation centre,
* dt - time increment,
* 𝜏𝑅(𝑖) - current frictional shear stress,
* 𝜔 - rotational speed.

Friction work can also calculate from [[Power (physics)|power]] of used for welding and friction time (will not be greater than the friction time multiply to the power of the welder - engine of the welder) referring to rules [[conservation of energy]]. This calculation looks the simplest.

(12) [[Energy|''E'']] = [[Power (physics)|P]]<nowiki/>x[[Time|''t'']] or for not constant power  <math>E = \int_{0}^{t} f(P) \,dt</math>

* E - energy,
* P - power,
* t - power runtime.

However, in this case, energy can be also stored in the [[flywheel]] if is used depending on the welder construction.

General flywheel energy formula:

(13) <math>E_k = \frac{1}{2} I \omega^2</math>

where:

* <math>E_k</math> is the stored [[kinetic energy]],
* ω is the [[angular velocity]], and
* <math> I </math> is the [[moment of inertia]] of the flywheel about its axis of symmetry.
Sample calculations not by computer simulation also exist in the literature for example related to power input and temperature distribution can be found in the script from 1974:

K. K. Wang and Wen Lin from [[Cornell University College of Engineering|Cornell University]] in "[https://app.aws.org/wj/supplement/WJ_1974_06_s233.pdf Flywheel friction welding research]" manually calculates welding process and even at this time the weld structure was analysed.<ref name=":17" />

However, generally: The calculations can be complicated.

== Weld Zone Description ==

=== Weld photo gallery ===
{| class="wikitable"
|+
![[File:Weld_photo.jpg|thumb|Rotary Friction welding weld photo. Weld without clearly formed flash. No flash but something like the upset is visible on the right component (torsion line is not visible). The scale of the calliper is in mm. However, there's the problem:In this case, the very short friction time was used so real-time and direct temperature measurement of the weld center can be problematic, moreover  '''welding in a short time causes risks of imperfections such as weld discontinuities.'''|center|360x360px]]
![[File:Weld image of inconel superalloy after destructive tensile test.png|thumb|468x468px|Welded rods of inconel 600 and inconel 718 superalloy after destructive tensile test.<ref name=":27" />|center]]
![[File:1-s2.0-S2238785417305574-gr4 lrg.jpg|thumb|420x420px|Photo of friction welded API 5L X46 pipeline with diameter of 220 mm and wall thickness of 8 mm.<ref name=":26" /> The typically flash is visible on the image.

However, there's the problem:Internal significant flash is visible here and can be difficult to remove in pipeline.|center]]
|-
![[File:Friction welding joint.png|thumb|439x439px|Typical Rotary Friction Welding joint. Dissimilar materials: stainless and copper with  24  mm  diameter  and  75mm  length are welded.<ref name=":4" />|center]]
![[File:Rods AL AA1050 and AISI 304 Stainless steel.jpg|center|thumb|334x334px|Friction welded rods of aluminum AA1050 and AISI 304 stainless steel with diameter of 14.8 mm. Rods before and after welding prepared for tensile test.<ref name=":35">{{Cite journal|last1=Alves|first1=Eder Paduan|last2=Piorino Neto|first2=Francisco|last3=An|first3=Chen Ying|last4=Alves|first4=Eder Paduan|last5=Piorino Neto|first5=Francisco|last6=An|first6=Chen Ying|date=December 2010|title=Welding of AA1050 aluminum with AISI 304 stainless steel by rotary friction welding process|journal=Journal of Aerospace Technology and Management|volume=2|issue=3|pages=301–306|doi=10.5028/jatm.2010.02037110|issn=2175-9146|doi-access=free}}</ref> The AISI 304 stainless steel has higher strength than the aluminum alloy. Hence, the formation of flashes was restricted to AA1050 aluminum only.<ref name=":35" />]]
![[File:Rods AL AA1050 and AISI 304 Stainless steel afret tensile test.jpg|center|thumb|492x492px|Rods Aluminium AA1050 and AISI 304 Stainless steel afret tensile test.<ref name=":35" /> On this photo rupture occurring on aluminium site away from the bonding interface.]]
|-
![[File:Tungsten - steel weld.png|thumb|360x360px|[[Tungsten]] - [[steel]] weld.<ref>{{Cite journal |last1=Skowrońska |first1=Beata |last2=Bober |first2=Mariusz |last3=Kołodziejczak |first3=Paweł |last4=Baranowski |first4=Michał |last5=Kozłowski |first5=Mirosław |last6=Chmielewski |first6=Tomasz |date=2022 |title=Solid-State Rotary Friction-Welded Tungsten and Mild Steel Joints |journal=Applied Sciences |language=en |volume=12 |issue=18 |pages=9034 |doi=10.3390/app12189034 |issn=2076-3417 |doi-access=free }}</ref> Hoverer there is a problem: Some materials can be problematical to weld, those with a high melting point and differences in physical properties such as [[molybdenum]], [[tantalum]], [[tungsten]].<ref name=":43">{{Cite web |title=What materials are difficult to join by friction welding? |url=https://www.twi-global.com/technical-knowledge/faqs/faq-what-materials-are-difficult-to-join-by-friction-welding.aspx |access-date=2023-12-21 |website=www.twi-global.com |language=en-GB}}</ref> The photo shows a significant difference with melting between tungsten and steel. 

There are some methods to solve the problem such as preheating material with a high melting point to proper temperature.<ref name=":20" />]]
!
!
|}

=== Heat and mechanical affected zones ===
Friction work is converted into rise of temperature in the welding zone area, and as a result of this the weld structure is changed. In typical rotary friction welding process rise of temperature at the beginning of process should be more extensively away from the axis of rotation<ref name=":15" /> because points away axis have greater linear velocity and in time of weld the temperature disperses according to [[thermal conductivity]] welded parts.

[[File:Weld Zones Friction Welding.jpg|thumb|346x346px|Picture shows weld zones in friction welding.<ref name=":1">{{cite journal|last1=McAndrew|first1=Anthony R.|last2=Colegrove|first2=Paul A.|last3=Bühr|first3=Clement|last4=Flipo|first4=Bertrand C.D.|last5=Vairis|first5=Achilleas|date=2018-10-03|title=A literature review of Ti-6Al-4V linear friction welding|journal=Progress in Materials Science|volume=92|pages=225–257|doi=10.1016/j.pmatsci.2017.10.003|issn=0079-6425|doi-access=free}}</ref>|center]]
''"Technically the WCZ and the TMAZ are both "thermo-mechanically affected zones" but due to the vastly different microstructures they possess they are often considered separately. The WCZ experiences significant dynamic recrystallisation (DRX), the TMAZ does not. The material in HAZ is not deformed mechanically but is affected by the heat. The region from one TMAZ/HAZ boundary to the other is often referred to as the "TMAZ thickness" or the plastically affected zone (PAZ). For the remainder of this article this region will be referred to as the PAZ."''<ref name=":1" />

Zones:

* WCZ– weld center zone,
* HAZ – [[Heat-affected zone|heat affected zone]],
* TMAZ – Thermo-Mechanically Affected Zone,
* BM – base material, parent material,
* Flash.
Furthermore, in the literature, there is also a subdivided according to the type of grain.<ref>{{Cite journal|date=2021-04-01|title=Discretization and material parameter characterization for a HAZ in direct-quenched armor steel|journal=European Journal of Mechanics - A/Solids|language=en|volume=89|pages=104305|doi=10.1016/j.euromechsol.2021.104305|issn=0997-7538|doi-access=free|last1=Neuvonen|first1=Riku|last2=Skriko|first2=Tuomas|last3=Björk|first3=Timo|bibcode=2021EuJMA..8904305N}}</ref>

Similar terms exist in [[welding]].

During typical welding initially, the outer region heats up more, due to the higher linear [[velocity]]. 
[[File:RFW friction welding components heating over time.jpg|center|thumb|Components heating over time.<ref name=":15" />]]
Next, the [[Heat flow|heat spreads]], and the material is pushed outside, thus creating an outside flash which can be cut off on the welding machine.[[File:RFW friction Flash cut off..jpg|thumb|[https://www.youtube.com/watch?v=mYJmCgmTvO4&t=94s Flash cut off on rotary friction welder.]|center]]

=== Heat flow, heat flux in rods ===
{{Main|Heat_equation#Heat_flow_in_a_uniform_rod|Heat transfer}}
{{Expand section|date=December 2020}}
It can create a [[hypothesis]] that heat flows in welding time like in a cylindrical rod it makes it possible to calculate a temperature in individual places and times from knowing the issues of [[Heat transfer|heat flow]] and [[heat flux]] in rods for example, temperature can be read by using [[thermocouple]]s and compare with computer simulation. <gallery widths="320">
File:Heat flow rod for RFW variant 2.jpg|Heat flow in Rod, and variant 1 placement of [[thermocouple]].
File:Heat flow in Rod, and variant 1 placement of thermocouples..jpg|Heat flow in Rod, and variant 2 placement of [[thermocouple]]s.
</gallery>

== Weld measuring system ==
To provide knowledge about the process, monitoring systems are often used and this are carried out in several ways which affects the accuracy and the list of measured parameters.<ref name=":28">{{Cite journal|first1=Christopher J.|last1=Bennett|first2=Dragos|last2=Axinte|first3=Andres|last3=Gameros|first4=Peter A.|last4=Stevens|first5=Luca|last5=Raimondi|date=2021-07-01|title=Development of a novel monitoring system for the in-process characterisation of the machine and tooling effects in Inertia Friction Welding (IFW)|journal=Mechanical Systems and Signal Processing|language=en|volume=156|pages=107551|doi=10.1016/j.ymssp.2020.107551|bibcode=2021MSSP..15607551R|issn=0888-3270|doi-access=free}}</ref>
[[File:CAD image and photo of the IFW measuring system.jpg|alt=|center|thumb|800x800px|The computer aided design image point out the location of the sensors and on the photo is shown the real view of the Inertia Friction Welding (IFW) machine with mounted sensors.There is situated [[Linear variable differential transformer|Linear Variable Differential Transformer]] (LVDTs), triaxial accelerometer, encoder, laser sensors, strain sensors.<ref name=":28" />]]
The list of measured and calculated parameters can looks like this:

* [[Force|axial force]] and [[pressure]],
* [[Angular speed|angular]] - [[Rotational speed|rotation speed]],
* spindle centre,
* [[velocity]],
* [[vibration]],
* length (burn off rate),
* [[temperature]].

=== Temperature measuring systems ===
Examples of weld measurements. In the literature, can be found measurements of the thermal weld area with [[thermocouple]]s<ref name=":5" /><ref name=":6" /> and not only the non-contact [[Thermography|thermographic]]<ref name=":6" /><ref name=":7" /> method is also used.
[[File:Graph measuring by the thermocouple..jpg|center|thumb|483x483px|Just an example for measuring by the contact thermocouple methods.]]

However, it also depends on the specific case for a very small area of the weld and HAZ there are cans by difficulties in thermal measuring in real time{{citation needed|date=December 2020}} it can be calculated later after friction time there is heat flow.{{citation needed|date=December 2020}}
[[File:Termocouple data acquisition example.jpg|center|thumb|450x450px|This is another example of a measurement but can be referenced. The [[thermocouple]] response can be in a dozen [[millisecond]], but thermocouple tip is all in hot tin additionally, this thermocouple was without a cover for shortened response time yet the cover protects the thermocouple. This example is not from friction welding but from measuring the temperature of hot tin.In this example [[Arduino|Andurino]] [[Open-source hardware|open source hardware]] + [[Analog-to-digital converter|Analog to digital]] (ADC) thermocouple converter [https://datasheets.maximintegrated.com/en/ds/MAX31855.pdf MAX31855K] was used.]]Sample source code for temperature measurement made on arduino, this is far away from the topic, however there are missing full open friction welding codes. Exists the free open source software for simulation ([[List of finite element software packages|List of finite element software]]) but there is no welding open codes and detailed instructions to this software.

{{Hidden|Example in Arduino IDE for temperature measurement with MAX31855. (click right show button to view)|text=Example in Arduino IDE for temperature measurement with MAX31855. However, the DAQ thermocouple measurement system may have a chip from any manufacturer.

[https://datasheets.maximintegrated.com/en/ds/MAX31855.pdf Specification MAX31855K]

[[File:Max31855K and arduino.jpg|thumb|It is student work with Max31855K and arduino although the chip is not ideal soldered it was soldered at home not in laboratory, it could have been done more nicely, but the goal was achieved, the temperature could be measured. Currently there are available this chip on the board.]]

[[File:Example temperature measurement diagram.jpg|none|thumb|358x358px|Example temperature measurement diagram used to for example for welding measurement simple students projects.]]

<syntaxhighlight lang="arduino" line="1">
#include "Adafruit_MAX31855.h"

int DO = 11;
int CS = 12;
int CLK = 13;

Adafruit_MAX31855 thermocouple(CLK, CS, DO);

void setup() {
    Serial.begin(9600);
    delay(200);
}

void loop() {
    Serial.println(thermocouple.readCelsius());
    delay(15);
}
</syntaxhighlight>
}}

== Research, temperature, parameters in the rotary friction welding process ==

Quality requirements of welded joints depend on the form of application, e.g. in the space or fly industry weld errors are not allowed.<ref name=":14">{{Cite book|last=J. Pilarczyk A. Piotr.|title=Poradnik inżyniera 1 – spawalnictwo.|publisher=Wydawnictwo WNT|year=2013|location=Warszawa|language=pl}}</ref> Science tries to gets good quality welds, also some people<ref>{{Cite journal |last1=Subramaniyan |first1=Madheswaran |last2=Eswaran |first2=Prakash |last3=Ramesh |first3=Aswin Pranav |date=2019 |others=In paper, is possible to find out list of people who are interested in friction welding but in this list not all the people are there for example there is not mentioned about mit youtube channel also there ale no mented about low force friction welding. |title=Review on Friction Welding of Similar/Dissimilar Metals |url=https://www.researchgate.net/publication/337309996 |journal=Journal of Physics: Conference Series |volume=1362:012032 |issue=1 |page=012032 |bibcode=2019JPhCS1362a2032P |doi=10.1088/1742-6596/1362/1/012032 |via=ResearchGate |doi-access=free}}</ref> have been interested in many years in welding knowledge, so there are many scientific articles describing the methods of joining, for example Bannari Amman Institute of Technology, published in 2019 year a literature review in their paper is possible to find out list of people who are interested in friction welding, however in this list not all off people are mentioned for example there is not mentioned about [https://www.youtube.com/@mtifrictionwelding/videos mti youtube] channel also there are not written about [https://www.mtiwelding.com/low-force-friction-welding/ low force friction welding] additionally, the list of people may change over time.

They are performed weld tests which give knowledge about [[mechanical properties]] of material in welded zone e.g. [[hardness|hardness tests]],<ref name=":3">{{cite journal|last1=Siedlec|first1=Robert|last2=Strąk|first2=Cezary|last3=Zybała|first3=Rafał|date=2016-11-10|title=Morfologia złączy kompozytów Al/Al2O3 zgrzewanych tarciowo ze stopem Al 44200|url=https://www.researchgate.net/publication/323333708|journal=Przegląd Spawalnictwa - Welding Technology Review|language=Pl|volume=88|issue=11|doi=10.26628/ps.v88i11.706|doi-broken-date=2 December 2024 |issn=2449-7959|doi-access=free}}</ref><ref name=":4">{{cite journal|last1=Shanjeevi|first1=C.|last2=Satish Kumar|first2=S.|last3=Sathiya|first3=P.|date=2013|title=Evaluation of Mechanical and Metallurgical Properties of Dissimilar Materials by Friction Welding|journal=Procedia Engineering|volume=64|pages=1514–1523|doi=10.1016/j.proeng.2013.09.233|issn=1877-7058|doi-access=free}}</ref><ref name=":5">{{cite journal|last1=Liu|first1=F. J.|last2=Fu|first2=L.|last3=Chen|first3=H. Y.|date=2018-02-14|title=Effect of high rotational speed on temperature distribution, microstructure evolution, and mechanical properties of friction stir welded 6061-T6 thin plate joints|url=https://www.researchgate.net/publication/323176972|journal=The International Journal of Advanced Manufacturing Technology|volume=96|issue=5–8|pages=1823–1833|doi=10.1007/s00170-018-1736-0|s2cid=253679782 |issn=0268-3768|doi-access=}}</ref> and [[Tensile testing|tensile tests]] are performed.<ref name=":4" /> Based on the [[Tensile testing|tensile tests]] the stretch curve are created which can give directly knowledge about [[ultimate tensile strength]], [[breaking strength]], maximum [[Elongation (materials science)|elongation]] and reduction in area and from these measurements the [[Young's modulus]], [[Poisson's ratio]], [[yield strength]], and [[strain-hardening]] characteristics is created.
[[File:Tension test.svg|thumb|274x274px]]
Where, the articles often contain only data related to tensile tests such as:

* [[Yield strength|Yield Strength]] in [[MPa]]
* [[Ultimate tensile strength|Ultimate Tensile Strength]] in [[MPa]]
* [[Elongation (materials science)|Elongation]] in % [[percentage]]

Where the [[International System of Units|units of SI]] are: [[Kelvin|K]], [[Kilogram|kg]], [[Newton (unit)|N]], [[Metre|m]], [[Second|s]] and then [[Pascal (unit)|Pa]] and this knowledge about this is needed for introducing data, material properties and not do errors in simulation programs.

{{Hidden|Info about material units for simulation. (click right show button to view)|text=The units are dependent on the unit system selected. For example, SI unit system:

* Dimensions - m
* [[Density|Mass Density]] in kg/m<sup>3</sup>
* [[Young's modulus]] - Pa
* [[Poisson's ratio]] - empty
* [[Thermal conductivity]] - W/m*K
* [[Specific heat capacity|Specific heat]] - J/Kg*K
* [[Pressure]] - Pa

<gallery widths="320">
File:Ansys Unit system.jpg|Unit system
File:Ansys sample Print Screen 316 Stainless Steel Properties.jpg|Ansys sample Print Screen 316 Stainless Steel Properties with temperature.
File:Ansys sample Print Screen Structural Steel Properties.jpg|[[Ansys]] sample print screen Structural Steel Properties. Here [[Celsius]], [[Pascal (unit)|Pa]], [[Kilogram|Kg]], [[Metre|m]] was used for all physical formulas. However, these are only starting data because the material properties change with temperature.
</gallery>

}}

Research articles also often contain information about:
* chemical composition of connected components
and inclusion process parameters is obvious such as:
* Friction Pressure (MPa)
* Friction Time (s)
* Welding Speed (rpm)
* Upset Pressure (MPa)
* Upset Time (s)
Is also possible to find descriptions in research literature about: [[mechanical properties]], [[microstructure]], [[Corrosion resistance|corrosion]] and [[wear resistance]], and even [[cytotoxicity]]<ref name=":38" /> welded material.

However, why research connect topic of cytotoxicity to welding if it is a subject not closely related ([[cytotoxicity]]<ref name=":38" /> is the quality of being toxic to cells). On this article can write that exist same off toxic metals and metals vapors such as [[polonium]]. It can be written than in some cases when welding at high temperatures, harmful metal vapors are released and then protection is recommended such as access to fresh air and exhaust these vapors to outside.

[[File:Vapor extractor..png|thumb|273x273px|Vapor extractor in welder.]]
There are several methods to determine the quality of a weld<ref name=":36" /> and for example the weld [[microstructure]] is examined by [[Optical microscope|optical microscopy]]<ref name=":4" /><ref name=":5" /><ref name=":6">{{cite journal|last1=Wang|first1=Guilong|last2=Li|first2=Jinglong|last3=Xiong|first3=Jiangtao|last4=Zhou|first4=Wei|last5=Zhang|first5=Fusheng|date=2018-06-05|title=Study on microstructure evolution of AISI 304 stainless steel joined by rotary friction welding|journal=Welding in the World|volume=62|issue=6|pages=1187–1193|doi=10.1007/s40194-018-0613-7|issn=0043-2288|s2cid=139498947}}</ref> and [[Scanning electron microscope|scanning electron microscopy]].<ref name=":2" /><ref name=":5" /><ref name=":6" /><ref name=":4" />

The computer [[finite element method]] (FEM) is used to predict the shape of the flash and interface, not only for rotary friction welding (RFW),<ref name=":7">{{cite journal|last1=Nan|first1=Xujing|last2=Xiong|first2=Jiangtao|last3=Jin|first3=Feng|last4=Li|first4=Xun|last5=Liao|first5=Zhongxiang|last6=Zhang|first6=Fusheng|last7=Li|first7=Jinglong|date=2019|title=Modeling of rotary friction welding process based on maximum entropy production principle|journal=Journal of Manufacturing Processes|volume=37|pages=21–27|doi=10.1016/j.jmapro.2018.11.016|s2cid=139752670 |issn=1526-6125}}</ref> but also for [[friction stir welding]] (FSW),<ref name=":10">{{cite journal|last1=Lacki|first1=P.|last2=Kucharczyk|first2=Z.|last3=Śliwa|first3=R.E.|last4=Gałaczyński|first4=T.|date=2013-06-01|title=Effect of Tool Shape on Temperature Field in Friction Stir Spot Welding|journal=Archives of Metallurgy and Materials|volume=58|issue=2|pages=595–599|doi=10.2478/amm-2013-0043|issn=1733-3490|doi-access=free}}</ref><ref name=":11">{{cite journal|last1=Qin|first1=D. Q.|last2=Fu|first2=L.|last3=Shen|first3=Z. K.|date=2019-01-15|title=Visualisation and numerical simulation of material flow behaviour during high-speed FSW process of 2024 aluminium alloy thin plate|url=https://www.researchgate.net/publication/330008868|journal=The International Journal of Advanced Manufacturing Technology|volume=102|issue=5–8|pages=1901–1912|doi=10.1007/s00170-018-03241-5|s2cid=253679546 |issn=0268-3768|doi-access=}}</ref> linear friction welding (LFW),<ref name=":1" /> FRIEX.<ref name=":12">{{cite journal|last1=Pissanti|first1=Daniela Ramminger|last2=Scheid|first2=Adriano|last3=Kanan|first3=Luis Fernando|last4=Dalpiaz|first4=Giovani|last5=Kwietniewski|first5=Carlos Eduardo Fortis|date=January 2019|title=Pipeline girth friction welding of the UNS S32205 duplex stainless steel|journal=Materials & Design|volume=162|pages=198–209|doi=10.1016/j.matdes.2018.11.046|issn=0264-1275|doi-access=free}}</ref>[[File:Picture from virtua RFW sampro-software.jpg|thumb|273x273px|Example Friction welding simulation in dedicated commercial sampro-software for Rotary Friction Welding.

However, it is not free and open source program (in 2023 year).

There exist also general moreover expanded software for FEM simulation, sometimes free and [[Open-source software|open-source]] - [[List of finite element software packages|List of finite element software.]]

However, there is a problem: simulation welding requiring users skills, appropriate software and knowledge, sometimes comparisons with real similar examples, it is not very easy and the files are not shared or instructions of welding contains errors.

]]

In addition to the [[Weld quality assurance|weld testing]], the weld [[heat-affected zone]]s are described.<ref name=":1" /> Knowledge of the maximum temperatures in the welding process make it possible to define the area structural changes.<ref name=":14" /> Process are analisis e.g. temperature measurements are also carried out for scientific purposes [[research]] materials, journals, by use contact [[thermocouple]]s<ref name=":5" /><ref name=":6" /> or sometimes no contact [[thermography]]<ref name=":7" /><ref name=":6" /> methods. For example, an ultra fine [[Crystallite|grain]] structure of alloy or metal which is obtained by techniques such as [[severe plastic deformation]]<ref>{{Cite book|last=Rosochowski|first=Andrzej|title=Severe plastic deformation technology.|date=2013|publisher=Whittles Publishing|isbn=978-1-84995-119-7|location=Place of publication not identified|language=en|oclc=968912427}}</ref><ref>{{Cite journal|last=Gianluca Buffa, Łukasz Morawiński, Livan Fratini, Małgorzata Lewandowska|first=Marta Orłowska, Lech Olejnik, Davide Campanella|date=2020-08-01|title=Application of linear friction welding for joining ultrafine grained aluminium|journal=Journal of Manufacturing Processes|language=en|volume=56|pages=540–549|doi=10.1016/j.jmapro.2020.05.012|issn=1526-6125|doi-access=free|hdl=10447/421431|hdl-access=free}}</ref> or [[Powder metallurgy]] is desirable, and not changed by the high temperature, a large [[Heat-affected zone|heat affected zone]] is unnecessary. Temperature may reduce material properties because [[dynamic recrystallization]] will occur, there may be changes in grain size and phase transformations<ref>{{Cite journal|last1=Cui|first1=Ling|last2=Fujii|first2=Hidetoshi|last3=Tsuji|first3=Nobuhiro|last4=Nakata|first4=Kazuhiro|last5=Nogi|first5=Kiyoshi|last6=Ikeda|first6=Rinsei|last7=Matsushita|first7=Muneo|date=2007|title=Transformation in Stir Zone of Friction Stir Welded Carbon Steels with Different Carbon Contents|journal=ISIJ International|volume=47|issue=2|pages=299–306|doi=10.2355/isijinternational.47.299|issn=0915-1559|doi-access=free}}</ref> structures of welded materials. In steel between [[austenite]], [[Allotropes of iron|ferrite]], [[pearlite]], [[bainite]], [[cementite]], [[martensite]].

Various parameters of welding are tested. The setting of the completely different parameters can obtain different weld for example the structure changes will not be the same width. It is possible to obtain a smaller [[heat-affected zone]] (HAZ) and a plastically affected zone (PAZ). The width of the weld is smaller. The results are for example not the same in welds made for the [[European Space Agency]] with a high turnover ω = 14000 rpm<ref name=":2">{{cite journal|last=M. Meisnar, S. Baker, J.M. Bennett, A. Bernad, A. Mostafa, S. Resch, N. Fernandes, A. Norman|year=2017|title=Microstructural characterization of rotary friction welded AA6082 and Ti-6Al-4V dissimilar joints|url=https://www.sciencedirect.com/science/article/pii/S0264127517306652|journal=Materials & Design|volume=132|pages=188–197|doi=10.1016/j.matdes.2017.07.004}}</ref> or [http://journals.pan.pl/Content/113022/PDF/AMM-2019-3-41-Skowronska.pdf another example] from [[Warsaw University of Technology|Warsaw technical university]] 12000 rpm<ref name=":8">{{cite journal|last=B. Skowrońska, T. Chmielewski, W. Pachla, M. Kulczyk, J. Skiba, W. Presz|date=2019|title=Friction Weldability of UFG 316L Stainless Steel|url=http://journals.pan.pl/Content/113022/PDF/AMM-2019-3-41-Skowronska.pdf|journal=Arch. Metall. Mater.|volume=3, 64|pages=1051–1058|doi=10.24425/amm.2019.129494|s2cid=216781328 }}</ref> and no typical '''very short friction time only 60 [[millisecond]]s'''<ref name=":9">{{cite journal|last1=Skowrońska|first1=Beata|last2=Siwek|first2=Piotr|last3=Chmielewski|first3=Tomasz|last4=Golański|first4=Dariusz|date=2018-05-10|title=Zgrzewanie tarciowe ultradrobnoziarnistej stali 316L|url=https://www.researchgate.net/publication/325388807|journal=Przegląd Spawalnictwa - Welding Technology Review|volume=90|issue=5|doi=10.26628/ps.v90i5.917|doi-broken-date=1 November 2024 |issn=2449-7959|doi-access=free}}</ref> instead of using an standard parameters, in addition, in this case, [[Severe plastic deformation|ultra fine grain]] alloy was welded, but for this example the welded rod workpiece was only 6mm in diameter so it is small rod friction welding<ref name=":9" /> another close to this examples with short friction time only e.g. 40 ms also exist in literature but also for small diameter.<ref name=":3" /><ref name=":22" /> Unfortunately, welding in very short time carries the risk of welding imperfections such as weld discontinuities.  

{| class="wikitable"
|+
![[File:Welding imperfections - weld discontinuities..png|center|thumb|406x406px|Welding imperfections such as weld discontinuities. - Risk of welding in very short time.<ref name=":45">{{Cite journal |last1=Morawiński |first1=Łukasz |last2=Jasiński |first2=Cezary |last3=Ciemiorek |first3=Marta |last4=Chmielewski |first4=Tomasz |last5=Olejnik |first5=Lech |last6=Lewandowska |first6=Małgorzata |date=2021-05-27 |title=Solid-state welding of ultrafine grained copper rods |journal=Archives of Civil and Mechanical Engineering |volume=21 |issue=3 |page=89 |doi=10.1007/s43452-021-00244-0 |bibcode=2021ACME...21...89M |issn=1644-9665|doi-access=free }}</ref> Moreover research articles do not always describe the risks.]]
![[File:Corner problem in friction welding.png|center|thumb|406x406px|Corner problem in friction welding with specific parameters time below 100 ms and conical contact surface.<ref name=":45" />
There is a complete weld inside but corner is not welded. In individual cases this can be initially predicted and some case is possible make the welded elements with a larger diameter and after welding turn on a lathe.  Appropriate parameters, tests, are also helpful it may be also a solution before welding preheating of the front surface to the appropriate temperature. However to sum up, the photo shows the corner problem.]]
|}
Some cases of welding are made only individually or only in research such as: The welds created in with specific parameters such as welding time below 100 ms,<ref name=":9" /><ref name=":8" /> with an appropriate front surface for example (conical contact surface),<ref name=":45" /> with materials that are difficult to weld (tungsten to steel),<ref name=":44" /> these are not always serial production.

The rotations in the research literature for small diameters can be more as standard even e.g. 25000 rpm.<ref name=":13">{{Cite journal|last=Pietras, Bogucki|first=Adam, Bogucki|year=2005|title=Charakterystyka zgrzewania tarciowego elementów konstrukcji metalowych.|url=http://www.obrum.gliwice.pl/upload/downloads/spg/105/13-PIETRAS-BOGUCKI.pdf|journal=Szybkobieżne Pojazdy Gąsienicowe (21) nr 1, 2005|language=pl|access-date=2020-12-20|archive-date=2019-10-13|archive-url=https://web.archive.org/web/20191013153501/http://www.obrum.gliwice.pl/upload/downloads/spg/105/13-PIETRAS-BOGUCKI.pdf|url-status=dead}}</ref> Unfortunately the diameter of the workpiece can be a limitation to the use of high speeds of rotation.

The key points to understand is that: Fine grain of the welded metal material according to [[Hall-Petch relation]] should have better strength and for the description of one technique for obtaining this material [[Percy Williams Bridgman]] won the [[Nobel Prize in Physics]] in 1946<ref>{{Citation|title=List of Nobel laureates in Physics|date=2020-11-30|url={{Oldid|page=List of Nobel laureates in Physics|oldid=991432995|label=}}|work=Wikipedia|language=en|access-date=2020-12-21}}</ref> referring to the achievements related to [[High pressure torsion|High Pressure Torsion]] (HPT),.<ref>{{Cite journal|last1=ZHILYAEV|first1=A|last2=LANGDON|first2=T|date=August 2008|title=Using high-pressure torsion for metal processing: Fundamentals and applications|url=http://dx.doi.org/10.1016/j.pmatsci.2008.03.002|journal=Progress in Materials Science|volume=53|issue=6|pages=893–979|doi=10.1016/j.pmatsci.2008.03.002|issn=0079-6425}}</ref> However, by [[High pressure torsion|High Pressure Torsion]] is obtained only thin film thickness material.
{| class="wikitable"
|[[File:HallPetchLimit.png|thumb|[[Hall-Petch relation]].|274x274px|center]]
|[[File:Stress strain ductile.svg|thumb|[[Stress–strain curve|Stress-strain curve]] typical of a low carbon steel.|420x420px|center]]
|}
[[File:EDP painting.png|thumb|229x229px|The research [[Electrophoretic deposition|electrodeposition deposition]] technique of applying an intermediate interlayer. The properties of this layer are used later for welding.<ref name=":30" /> However, in this study, nickel interlayer thickness was of 70 <math>\mu</math>m (micrometre )and in this case only small rods of 12mm diameter were welded.

]]
There is also research into the introduction of interlayers. Even though dissimilar material joining is often more difficult the introduction for example [[nickel]] interlayer by an experimental [[Electrophoretic deposition|electrodeposition deposition]] technique to increase the connection quality has been investigated by the [[Indian Institute of Metals]], however in this case nickel interlayer thickness was of 70 <math>\mu</math>m (micrometre ) and only small rods of 12mm diameter were welded.<ref name=":30" /> This nickel layer is only on top of the welded parts. In addition, this topic is not very related to welding but nickel layer may affect off corrosion resistance.

Some scientists describe material research. Group of known materials is large includes: [[nickel|Ni nickel]] based [[superalloy]]s such as [[Inconel]], ultra-fine grain materials such as ultra-fine grain aluminum, low carbon steel e.g. Ultra Low Carbon Bainitic Steel (ULCBS). Friction welding is used for connection many materials including [[superalloy]]s for example [[nickel]]-based [[Inconel]],<ref name=":27" /> scientists describe connecting various materials and on the internet is possible finding articles about this and same part of the research relates to joining [[superalloy]]s materials or materials with improved properties. Nickel based superalloys exhibit excellent high temperature strength, high temperature corrosion and oxidation resistance and creep resistance.<ref name=":27" /> However, referring to this research good add that nickel is not the most common and cheapest material: [[Prices of chemical elements|Prices list of chemical elements]].

=== Parameters ===
* Turnover: Typically turnover is selected depending on the type of material and dimensions of welded parts have different values:  400 - 1450 rpm, sometimes max 10000 rpm.<ref name=":15">{{Cite book|last=Klimpel|first=A.|title=Spawanie zgrzewanie i cięcie metali|publisher=Wydawnictwo Naukowo-Techniczne|year=2009|isbn=978-83-204-3625-9|language=pl}}</ref> Not typically, in research literature turnover is to 25000 rpm.<ref name=":13" />
* Friction time: typically 1 - to several dozen seconds. Not typically, in research literature friction time can be in tens of [[millisecond]]s, however when time is very short and parameters are not typical process can require a lot of preliminary preparation and testing to the positive result.<ref name=":37">{{Cite journal|last1=Morawiński|first1=Łukasz|last2=Jasiński|first2=Cezary|last3=Ciemiorek|first3=Marta|last4=Chmielewski|first4=Tomasz|last5=Olejnik|first5=Lech|last6=Lewandowska|first6=Małgorzata|date=2021-05-27|title=Solid-state welding of ultrafine grained copper rods|journal=Archives of Civil and Mechanical Engineering|language=en|volume=21|issue=3|pages=89|doi=10.1007/s43452-021-00244-0|bibcode=2021ACME...21...89M|s2cid=236347826 |issn=1644-9665|doi-access=free}}</ref><ref name=":22" /><ref name=":8" /> 
*Forge time: Up to a few seconds.
'''However''', the parameters will be different as elements of different sizes can be welded. For example, can be produced ranging from the smallest component with a diameter of 3&nbsp;mm to [[turbine]] components with a diameter in excess of 400&nbsp;mm.<ref name=":21" /><ref name=":25" />

By combining methods of connecting long elements perhaps future science may study the friction welding of rails for example for the [[High-speed rail|high speeds railway]] industry and use the preheat Low force linear friction welding<ref>{{Cite web|title=Low-Force Friction Welding: A Promising Solution for the Rail Industry|url=https://blog.mtiwelding.com/low-force-friction-welding-rail|access-date=2021-08-08|website=blog.mtiwelding.com|language=en-us}}</ref> or modified Linear friction welding (LFW) method and vibrating insert (just like the rotating insert in FRIEX method) for do this if the machine are developed and also good add that most of attention are directed to safety of travelers, '''user safety should be preserved''' at the first place.<ref>Received private email message from A. Klimpel professor, Silesian University of Technology, 2021, private quotation.</ref>
[[File:Clearly visible flash, not recommended and difficult to remove..png|thumb|219x219px|For example, the article:''"Pipeline girth friction welding of the UNS S32205 duplex stainless steel"'' describes friction welding of pipeline.<ref name=":12" />However, in this case is problem, on the photo is clearly visible internal flash, not recommended and difficult to remove.<ref>{{Citation |title=Whiteboard Wednesday: Rotary Friction Welding VS Low Force for Drill Pipe | date=12 September 2023 |url=https://www.youtube.com/watch?v=lbByaYl9p6o |access-date=2023-12-08 |language=en}}</ref>]]
Preliminary research involving similar welds and geometry has shown improved tensile strength and increased performance in the fatigue tests.[[File:MASF 1500 welder.jpg|thumb|Image of the machine from research on friction welding system for pipeline steel.<ref name=":26" /> Unfortunately, in this case to 08.2022 only one image of the machine was shared, so is difficult to deduce reality of this image. The authors of paper wher image is, mentions that this welder is for long components with an outer diameter of 220 mm and wall thickness of 8 mm, however additional tests should be performed with regard to the risk of crack<ref name=":26" /> and also good add safety of users and the environment if it is used for pipeline: [[List of pipeline accidents]]]]
{| class="wikitable"
| colspan="7" |Table with sample book typical parameters of the welding process.<ref name=":15" />
|-
! rowspan="2" |Materials
<small>(Symbols are standardized but dependent on the region)</small>
! rowspan="2" |Diameter  [mm]
! rowspan="2" |Rotation speed [RPM]
! colspan="2" |Pressure  [MPa]
! rowspan="2" |Friction time

[s]
! rowspan="2" |Burn off rate

[mm]
|-
!Friction
!Forge
|-
|steel S235JR + steel S235JR
|40
|750
|80
|100
|11
|6–6.5
|-
|steel C55 + steel C55
|40
|1000
|100
|140
|15
|11.1–11.4
|-
|steel 41Cr4 + steel 41Cr4
|20
|1000
|60
|120
|8.5
|5–5.5
|-
|steel X20Cr13 + steel X20Cr13
|20
|1000
|100
|206
|6
|5.5
|-
|steel OOH18M2Nb + steel OOH18M2Nb
|24
|1450
|90
|120
|225
|<nowiki>-</nowiki>
|-
|steel X3CrTi17 + steel X3CrTi17
|35
|750
|50
|100
|8
|7–7.5
|-
|steel X6CrNiTi18 + steel X6CrNiTi18
|35
|750
|90
|200
|23
|6.5–7.2
|-
|Aluminium + Aluminium
|40
|750
|30
|30
|9
|30
|-
|copper CW004A + copper CW004A
|35
|1500
|52
|150
|1
|8.6–9.4
|-
|steel 100Cr6 + steel C45
|22
|1000
|50
|140
|7–8
|5.6
|-
|steel HHS+ C55
|20
|1450
|140
|160
|8
|<nowiki>-</nowiki>
|-
|steel HS18-0-1 + steel C55
|20
|1450
|140
|160
|10
|<nowiki>-</nowiki>
|-
|steel X6CrNiTi18-10 + steel E295 
|40
|1000
|110
|145
|30
|<nowiki>-</nowiki>
|-
|Aluminium + steel S235JR
|50
|400
|50
|120
|7
|15
|-
|copper CW004A + steel S195
|20
|1450
|25
|160
|5.3
|12
|}Controversies in research
# As of August 2022, there are no step-by-step reviewed instructions on how to simulate the temperature of welded components. There are no shared source files for programs where simulation of welding is possible. On the other hand, some of the knowledge is difficult<ref>{{Cite thesis |title=Friction stir welding (FSW) simulation using an arbitrary Lagrangian -Eulerian (ALE) moving mesh approach |publisher=West Virginia University Libraries |first=Hua |last=Zhao|year=2005 |doi=10.33915/etd.4208 |doi-access=free }}</ref><ref name=":40">{{Cite journal |last=Hua Zhao |date=2005 |title=Friction stir welding (FSW) simulation using an arbitrary Lagrangian-Eulerian (ALE) moving mesh approach |url=https://researchrepository.wvu.edu/cgi/viewcontent.cgi?article=5245&context=etd |journal=Dissertation: West Virginia University, Statler College of Engineering and Mineral Resources, Mechanical and Aerospace Engineering}}</ref> for example in 08.2022 an article: Hamed, Maien Mohamed Osman the "[https://open.uct.ac.za/handle/11427/36777 Numerical simulation of friction welding processes: An arbitrary Lagrangian-Eulerian approach]"<ref name=":40" /> was shared on google scholar but it is difficult to understand.
# Problem with open article reviews or review no exist.
# Correct use of grants, and repeating of knowledge for example the structure of a lot of articles is similar and sometimes generally only the next material is welded so there is nothing new but some of research is granted.
# It is only friction welding, generally nothing difficult, on the other hand there are many complicated descriptions, but the practical result of this articles is missing: The expectation is to create something new, unknown so far.
# Correct use of grants, time of articles, who is first, announcing about the desire to create something new an innovative device by the university but this is not done:
#* '''Poland'''
[[File:PW RFW Welder Foto.jpg|thumb|Rotary Friction Welder Photo from [[Warsaw University of Technology]] (photo from 2019 year).]]
Google scholar finds 246 articles in response to the "friction welding" phrase in 8.2022, this is only part of all available research, and for some of them financial grants are given. However, for example in 2016 [http://www.itme.edu.pl/index.php?page=itme The Institute of Electronic Materials Technology in Poland]  published t [https://www.researchgate.net/publication/323333708_Morfologia_zlaczy_kompozytow_AlAl2O3_zgrzewanych_tarciowo_ze_stopem_Al_44200 he article in Polish language about welding Al/Al2O3 Composites],<ref name=":39">{{cite journal |last1=Siedlec |first1=Robert |last2=Strąk |first2=Cezary |last3=Zybała |first3=Rafał |date=2016-11-10 |title=Morfologia złączy kompozytów Al/Al2O3 zgrzewanych tarciowo ze stopem Al 44200 |url=https://www.researchgate.net/publication/323333708 |journal=Przegląd Spawalnictwa - Welding Technology Review |language=Pl |volume=88 |issue=11 |doi=10.26628/ps.v88i11.706 |doi-broken-date=2 December 2024 |issn=2449-7959 |doi-access=free}}</ref> after then two years later the [[Warsaw University of Technology]] publishes an article in Polish language about friction welding ultrafine grained 316L steel in 2018, although the materials was different, but the process parameters suggest that the welding machine is the same, so in this case The Institute of Electronic Materials Technology was published the data first, and summarizing in this case: in 2018 only the new material, which was steel, was welded and tested, the machine was not new but for this a [https://projekty.ncn.gov.pl/en/index.php?projekt_id=394754 grant was obtained] (843 920 PLN = ~US$177476). It has not been written into the articles since the two institutes had a machine and since studies with short friction times were carried out. 
Students were informed about the willingness to create by the university a new '''innovative''' friction welder, but to 08.2022 there is no information about this, there are new research articles, but '''the device is still old''' (information valid in 2019 year).

== Low Force Friction Welding ==
'''An improved modification''' of the standard friction welding is Low Force Friction Welding, hybrid technology developed by EWI and Manufacturing Technology Inc. (MTI),<ref>{{Cite web|date=2020-11-30|title=Joining Bimetallics with Low Force Friction Welding|url=https://buffalomanufacturingworks.com/joining-bimetallics-with-low-force-friction-welding/|access-date=2020-12-25|website=Buffalo Manufacturing Works|language=en-US}}</ref><ref>{{Cite news|last=Gould|first=Jerry|date=2020|title=Application of Low Force Friction Welding to a 6061-T6 Aluminum Alloy|language=en-US|work=|url=https://ewi.org/joining-6061-t6-aluminum-using-low-force-friction-welding/|access-date=2021-01-15}}</ref> "''uses an external energy source to raise the interface temperature of the two parts being joined, thereby reducing the process forces required to make a solid-state weld compared to traditional friction welding''".<ref name=":20">{{Cite web|last=Jones|first=Simon|title=Low Force Friction Welding -- What is it?|url=https://blog.mtiwelding.com/low-force-friction-welding|access-date=2020-12-25|website=blog.mtiwelding.com|language=en-us}}</ref> The process applies to both linear and rotary friction welding.<ref name=":20" /> 

Following the informations from the Manufacturing Technology blog and website, the technology is promising.

Low force friction advantages:<ref name=":20" />

*Little or no flash,<ref name=":41">{{Citation |title=Whiteboard Wednesday: Traditional Friction Welding VS Low Force Friction Welding for Axles | date=25 July 2023 |url=https://www.youtube.com/watch?v=_EEySIShMa8 |access-date=2023-11-30 |language=en}}</ref><ref name=":42">{{Citation |title=Whiteboard Wednesday: Rotary Friction Welding VS Low Force for Drill Pipe | date=12 September 2023 |url=https://www.youtube.com/watch?v=lbByaYl9p6o |access-date=2023-11-30 |language=en}}</ref>[[File:Example of flash difference.png|thumb|Example of flash difference:<ref name=":41" /><ref name=":42" /> On the left in the photo is shown flash from standard welding, on the right from low force friction welding.  The welded element on the right looks correct.]]
*Joining of components previously limited by friction welding,<ref name=":43" /><ref name=":44">{{Cite journal |last1=Skowrońska |first1=Beata |last2=Bober |first2=Mariusz |last3=Kołodziejczak |first3=Paweł |last4=Baranowski |first4=Michał |last5=Kozłowski |first5=Mirosław |last6=Chmielewski |first6=Tomasz |date=2022-09-08 |title=Solid-State Rotary Friction-Welded Tungsten and Mild Steel Joints |journal=Applied Sciences |volume=12 |issue=18 |pages=9034 |doi=10.3390/app12189034 |issn=2076-3417 |doi-access=free }}</ref>  
For example, those with a high melting point such as refractory metals like [[molybdenum]], [[tantalum]], [[tungsten]] or if there is a difference in material properties.<ref name=":43" /><ref name=":44" />


The manufacturer also listed same advantages, which are not fully explained, this is not true for every case:
*Reduced machine footprint,<ref>{{Cite web |title=Low-Force Friction Welding |url=https://www.mtiwelding.com/low-force-friction-welding/#smaller-machine-size |access-date=2023-12-08 |website=MTI Welding |language=en-US}}</ref> but machine must have additional heating elements.
* Reduced weld cycle time,<ref name=":20" /> but preheating also takes time.
* Higher orientation precision,<ref name=":20" />
* Part repeatability,<ref name=":20" /> but this may also occur in some traditional welders if welding is repeatable.
Moreover, in 2021 the number of scientific articles for example on Google Scholar about Low force friction is smaller compared to description of the standard method about friction welding where an external energy source to raise the interface temperature is not used.

== Construction of the welding machine ==
[[File:RFW Welder2 v2.jpg|thumb|397x397px|Examples of components of the RFW welding machine created in cad, however this is a simplified example for knowledge extension,  so it must contain many errors.]]
Depending on the construction, but a standard welding machine may include the following systems:

* [[Control system]]
* [[Engine|Motor]] or motors in e.g. direct-drive welder
* [[Pneumatic actuator|Pneumatic]] or [[Hydraulic actuator|hydraulic]] pressure system
* Handle
* Non rotating [[vise|vice]]
* [[Clutch]] in direct-drive friction welder
* [[Spindle (tool)|Spindle]]
* [[Flywheel]] in inertia friction welder
* Housing
* [[Measuring|Measuring systems]]
Producers present solutions and welding machines can include:<ref name=":32" /><ref>{{Cite web|title=Linear Friction Welders|url=https://www.taylor-winfield.com/linear-friction-welding/|access-date=2021-03-05|website=Taylor Winfield Technologies|language=en-US}}</ref><ref>{{Cite web|title=US Korea Hotlink {{!}} Your Connection to Korean Industrial Manufacturers|url=https://www.uskoreahotlink.com/wp-content/uploads/Friction-Welding-Machines.pdf|access-date=2021-03-05|website=US Korea Hotlink {{!}} LPR Global}}</ref>

* Measurement and control dimensional systems: Active Travel Control, burn off rate measurement,
* Automation solutions, Defined angle positioning, Component lifter, Automatic door operations, Weld data export, Ready for industrial solutions, Automatic temperature control of the headstock, Monitoring of the cooling unit, servo motor control, 
* Have solutions for clean environment with no arcs, sparks, smoke or flames,
*Have ergonomic workspace, nice design,
*No special foundations or power supplies are required,
* Process control and documentation systems: All process data is documented numerically and graphically, have program management, Calculated parameters - Smart machine
* HMI touchscreen panels, 
* Barcode scanner for generate database of frictioned elements, 
* There are optional methods qr, barcode tagging manufactured elements for example on an additional machine such as laser barcode, or tagging if it is necessary and possible, <ref>{{Cite web |last=Laser |first=Epilog |date=2023-03-02 |title=Barcode Engraving with a Laser Engraver |url=https://www.epiloglaser.com/how-it-works/applications/barcode-engraving-system/ |access-date=2023-12-21 |website=Epilog Laser |language=en-US}}</ref>
* Flash cut off device systems on the welder, flash removal and facing, chip conveyor,
* Completely integrated solution in the specific production workflow using state of the art 3D process simulation,[[File:Friction welding simulation - movie..webm|thumb|Example of: Friction welding simulation - from [[Otto von Guericke University Magdeburg|Otto-von-Guericke University Magdeburg]] Future and additional  modernization in welding - but it is not easy, in addition, there is a risk of errors.  |252x252px]]
* Service assistance: Remote Service, Alarm conditions,
* Have certificates,
* Vapor extractor,

* Advanced Measurement systems,<ref name=":28" />[[File:Fully Automated Welder Cell from MTI.ogg|thumb|Fully Automated Welder Cell from MTI.ogv |252x252px]]
* Include innovative solutions: for example hybrid technology Low Force Friction Welding,<ref name=":20" /> and the system associated with this technology,
'''However''', there is not one manufacturer<ref>{{Cite web|title=360 Research Reports – Worldwide Market Research Report, Analysis & Consulting|url=https://www.360researchreports.com/TOC/15075697#Companies|access-date=2021-04-12|website=www.360researchreports.com}}</ref> on the market and no one welder machine model and in addition, not always the same material and diameters is welded and a good presentation, technology description, design, may or not may determine the best solutions. There are also exist advertising presentations related to welding.

=== Workpiece handles ===
The type of chuck depends on the technology used, their construction sometimes may be similar to a [[lathe]] and [[milling machine]]. 
{| class="wikitable"
|+
![[File:Three-jaw chuck..jpg|thumb|Three-jaw chuck, multi-jaws are also used.|center]]
![[File:Handle with a ER Colletsv2.jpg|thumb|Exemplary handle with an ER Collets (for small diameters of workpiece).]]
![[File:RFW Rotary friction welding handle.jpg|thumb|Rotary friction welding.|282x282px]]
![[File:Example handles for small comonents ~(6-14) mm.jpg|thumb|Example Handles for small components: diameter~(6-14)mm used in Rotary Friction Welder machine]]
|}

== Safety during friction welding ==
*Before starting the work, even if the short and basic safety regulations should be known.
*Compliance with [[occupational safety and health]] regulations
* Following the manufacturer's recommendations
* Set up the machine in a safe place: not blocking the entrance door, electric wires away from water, free movement of the users
* Recommended security systems for example: Emergency stop button, possibility of a quick stop of the machine
* Protection against touching a too hot object also it is not always visible that the object is hot - it also depends on the material being welded for example welding [[copper]] to [[Aluminium|aluminum]]<ref>{{Citation |title=20 Ton Copper to Aluminium Friction Welding Machine | date=19 August 2019 |url=https://www.youtube.com/watch?v=eGWxVn4cSuE |access-date=2023-12-10 |language=en}}</ref>
* Protection against lifting to massive components
[[File:Massive welding machine..png|center|thumb|400x400px|Massive welding machine.<ref>{{Cite web |title=Aerospace 300 Tri Mode Rotary Friction Welder |url=https://www.mtiwelding.com/aerospace-300-tri-mode-rotary-friction-welder/ |access-date=2023-12-10 |website=MTI Welding |language=en-US}}</ref>]]

* Caution with hot and sharp things for example the hot welded components, chips if they are cut off on the welding machine

[[File:RFW friction Flash cut off..jpg|center|thumb|400x400px|Chips -sharp edges. ]]
*Fresh air, for example do not smoke on the production hall near the machine also in some cases vapor extractor to outside in welder
[[File:Vapors in welding.png|center|thumb|400x400px|Vapors in welding and heated object.]]

* Covering moving components


The description of the security rules depends on the joining method and situation - access to fresh air, electrical ground, wearing protective clothing, protect the eyes is required.
<ref>{{Cite book|url=https://www.wilhelmsen.com/globalassets/marine-products/welding/documents/wilhelmsen-ships-service---unitor-welding-handbook.pdf|title=Maritime Welding Handbook Welding and Related Processes for Repair and Maintenance Onboard|publisher=Wilhelmsen Ships Service - Unitor}}</ref> 

However, personal protective equipment is recommended, but in some cases may be uncomfortable and in sometimes unnecessary, so protection depends on the situation.

The human factor also influences safety.

'''Staff negligence:'''
* theft for example copper grounding, because it can be sold for scrap,
* neglect of medical examinations, performed carelessly, even paided, because it's about earning money and not staff health,
* no cleaning for example because the shift time is over, 
* accidents on the way to work, 
* alcohol, an employee's bad day,
* spinal strains - e.g. several hours of quality control of manufactured components in a forced body position because for management [[workforce productivity]], quality and earning money is more important than staff health,
* outsourcing - transferring responsibility to another company,
* neglect of management, because sometimes they want to only make money, they look at production, not to employees. 

== Other techniques of friction welding ==

* [[Forge welding]]
* [[Friction stir welding]] (FSW)<ref name=":16">{{cite patent|country=AU|number=1016495|title=Improvements relating to friction welding|pubdate=1995-03-30|assign=[[The Welding Institute]]|inventor1-last=Dawes|inventor1-first=Christopher John|inventor2-last=Murch|inventor2-first=Michael George|inventor3-last=Needham|inventor3-first=James Christopher|inventor4=Edward David Nicholas;Peter Temple-Smith;Wayne Morris Thomas}}</ref><ref name=":11" /><ref name=":5" />
* Friction stir spot welding (FSSW)<ref name=":10" />
* Linear friction welding (LFW)<ref name=":1" />
* Research on friction welding of pipeline girth welds (FRIEX)<ref name=":12" />
* Friction hydro pillar overlap processing (FHPPOW)<ref>{{Cite journal|last1=Buzzatti|first1=Diogo Trento|last2=Chludzinki|first2=Mariane|last3=Santos|first3=Rafael Eugenio dos|last4=Buzzatti|first4=Jonas Trento|last5=Lemos|first5=Guilherme Vieira Braga|last6=Mattei|first6=Fabiano|last7=Marinho|first7=Ricardo Reppold|last8=Paes|first8=Marcelo Torres Piza|last9=Reguly|first9=Afonso|date=2019|title=Toughness properties of a friction hydro pillar processed offshore mooring chain steel|journal=Journal of Materials Research and Technology|volume=8|issue=3|pages=2625–2637|doi=10.1016/j.jmrt.2019.04.002|issn=2238-7854|doi-access=free}}</ref>
* Friction hydro pillar processing (FHHP)<ref>{{Cite journal|last1=Buzzatti|first1=Diogo Trento|last2=Buzzatti|first2=Jonas Trento|last3=Santos|first3=Rafael Eugenio dos|last4=Mattei|first4=Fabiano|last5=Chludzinski|first5=Mariane|last6=Strohaecker|first6=Telmo Roberto|date=2015|title=Friction Hydro Pillar Processing: Characteristics and Applications|journal=Soldagem & Inspeção|volume=20|issue=3|pages=287–299|doi=10.1590/0104-9224/si2003.04|issn=0104-9224|doi-access=free|hdl=10183/132809|hdl-access=free}}</ref>

== Terms and definitions, name shortcuts ==
'''[[Welding]]''' vs '''joining''' - Definitions depend on the author. Welding in Cambridge English dictionary means: "the activity of joining metal parts together"<ref>{{Cite web|title=welding|url=https://dictionary.cambridge.org/dictionary/english/welding|access-date=2021-02-26|website=dictionary.cambridge.org|language=en}}</ref> in Collins dictionary "the activity of uniting metal or plastic by softening with heat and hammering, or by fusion",<ref>{{Cite web|title=Welding definition and meaning {{!}} Collins English Dictionary|url=https://www.collinsdictionary.com/us/dictionary/english/welding|access-date=2021-02-26|website=www.collinsdictionary.com|language=en-US}}</ref> which means that welding is related to connect. '''Join''' or '''joining''' has a similar meaning that welding and can mean the same in English dictionary means "to connect or fasten things together"<ref name=":29">{{Cite web|title=join|url=https://dictionary.cambridge.org/dictionary/english/join|access-date=2021-02-26|website=dictionary.cambridge.org|language=en}}</ref><ref>{{Cite web|title=Join definition and meaning {{!}} Collins English Dictionary|url=https://www.collinsdictionary.com/us/dictionary/english/join|access-date=2021-02-26|website=www.collinsdictionary.com|language=en-US}}</ref> but joining otherwise has many meanings for example "If roads or rivers join, they meet at a particular point".<ref name=":29" /> Joining opposed to welding, is a general term and there are several methods available for joining metals, including riveting, [[soldering]], [[adhesive]], [[brazing]], coupling, [[Fastener|fastening]], press fit. Welding is only one type of joining process.<ref>{{Cite web|date=2018-09-24|title=Difference Between Joining and Welding|url=http://www.differencebox.com/engineering/difference-between-joining-and-welding/|access-date=2021-02-26|website=Difference Box|language=en-US}}</ref>

'''Solid-state''' weld - connect below the melting point,

'''welder''' - welding machine, but also mean a person who welds metal.

'''weld''' - the place of connection where the materials are mixed.<ref name=":31">{{Cite book|last=Singh|first=Bharat Raj|url=http://rgdoi.net/10.13140/RG.2.1.5088.6244|title=A Hand Book on Friction Stir Welding|date=2012|publisher=LAP Lambert Academic Publishing, UK|language=en|doi=10.13140/rg.2.1.5088.6244}}</ref>

'''weldability'''  - a measure of the ease of making a weld without errors.<ref name=":31" />

'''interlayer''' - an indirect component, indirect material.

To quote ISO ([[International Organization for Standardization|the International Organization for Standardization]], unfortunately the all ISO text is not free and open shared) - ISO 15620:2019(en) Welding 

'''"axial force''' - force in axial direction between components to be welded,

'''burn-off length''' - loss of length during the friction phase,

'''burn-off rate''' - rate of shortening of the components during the friction welding process,

'''component''' - single item before welding,

'''component induced braking''' - reduction in rotational speed resulting from friction between the interfaces,

'''external braking''' - braking located externally reducing the rotational speed,

'''faying surface''' - surface of one component that is to be in contact with a surface of another component to form a joint,

'''forge force''' - force applied normal to the faying surfaces at the time when relative movement between the components is ceasing or has ceased,

'''forge burn-off length''' - amount by which the overall length of the components is reduced during the application of the forge force,

'''forge phase''' - interval time in the friction welding cycle between the start and finish of application of the forge force,

'''forge pressure''' - pressure (force per unit area) on the faying surfaces resulting from the axial forge force,

'''forge time''' - time for which the forge force is applied to the components,

'''friction force''' - force applied perpendicularly to the faying surfaces during the time that there is relative movement between the components,

'''friction phase''' - interval time in the friction welding cycle in which the heat necessary for making a weld is generated by relative motion and the friction forces between the components i.e. from contact of components to the start of deceleration,

'''friction pressure''' - pressure (force per unit area) on the faying surfaces resulting from the axial friction force,

'''friction time''' - time during which relative movement between the components takes place at rotational speed and under application of the friction forces,

'''interface''' - contact area developed between the faying surfaces after completion of the welding operation,

'''rotational speed''' - number of revolutions per minute of rotating component,

'''stick-out''' - distance a component sticks out from the fixture, or chuck in the direction of the mating component,

'''deceleration phase''' - interval in the friction welding cycle in which the relative motion of the components is decelerated to zero,

'''deceleration time''' - time required by the moving component to decelerate from friction speed to zero speed,

'''total length loss (upset)''' - loss of length that occurs as a result of friction welding, i.e. the sum of the burn-off length and the forge burn-off length,

'''total weld time''' - time elapsed between component contact and end of forging phase,

'''welding cycle''' - succession of operations carried out by the machine to make a weldment and return to the initial position, excluding component - handling operations,

'''weldment''' - two or more components joined by welding."<ref>{{Cite web|last=|first=|date=|title=iso:15620|url=https://www.iso.org/obp/ui/#iso:std:iso:15620:ed-2:v1:en|access-date=2021-02-05|website=www.iso.org}}</ref>

And more than that:

* RFW - Rotary friction welding,
* LFW - Linear friction welding,
* FSSW - Friction stir spot welding,
* FRIEX -  Research on friction welding of pipeline girth welds,
* FHPPOW - Friction hydro pillar overlap processing,
* FHHP - Friction hydro pillar processing,
* LFFW - Low Force Friction Welding,
* FSW - Friction stir welding,
* BM - Base material,
* HAZ - Heat affected zone,
* PAZ - Plastically affected zone,
* DRX - Dynamic recrystallization,
* TMAZ - Thermo-Mechanically Affected Zone,
* UFG - Ultra fine grain,
* SPD - Serve plastic deformation,
* HPT - High Pressure Torsion,
* FEM - Finite element method,
* SEM - Scanning electron microscopy,
* ADC - Analog to digital converter.

== See also ==
*[[Welding]]
*[[Friction]]
*[[Friction welding]]
*[[Friction stir welding]]
*[[Temperature]]
*[[Heat-affected zone]]
*[[Dynamic recrystallization]]
*[[Grain boundary strengthening]]
*[[Severe plastic deformation]]

== Curiosities ==

* Frictional welding (μ[[Friction stir welding|FSW]]) was also performed using a [[CNC machine]].<ref>{{Cite journal|last1=Wang|first1=Kaifeng|last2=Khan|first2=Haris Ali|last3=Li|first3=Zhiyi|last4=Lyu|first4=Sinuo|last5=Li|first5=Jingjing|date=October 2018|title=Micro friction stir welding of multilayer aluminum alloy sheets|journal=Journal of Materials Processing Technology|volume=260|pages=137–145|doi=10.1016/j.jmatprotec.2018.05.029|s2cid=140028992 |issn=0924-0136|doi-access=free}}</ref> which does not mean that it is safe and recommended for the milling machine.
* Sometimes it is possible to perform welding on a lathe.{{Citation needed|date=January 2024}}

* Scientists even describe measurements of [[acoustic emission]]s during joining.<ref name=":28" /><ref>{{Cite journal|last=Jolly|first=W. D.|title=Use of Acoustic Emission as a Weld Quality Monitor |date=1969-01-01|doi=10.2172/4072855 |osti=4072855|language=English|doi-access=free}}</ref>

== References ==
<references />

== External links ==
{{Prone to spam|date=April 2024}}
<!--     
      {{No more links}}

Please be cautious adding when more external links.

Wikipedia is not a collection of links and should not be used for advertising.

Excessive or inappropriate links will be removed.

See [[Wikipedia:External links]] and [[Wikipedia:Spam]] for details.

If there are already suitable links, propose additions or replacements on
the article's talk page.

-->
* [https://scholar.google.pl/scholar?hl=pl&as_sdt=0%2C5&q=rotary+friction+welding&btnG=&oq=rotary+friction+ Rotary Friction Welding at google scholar] - scientific search engine also to many articles about rotary friction welding.
*[https://www.twi-global.com/technical-knowledge/job-knowledge/rotary-friction-welding-148 Rotary Friction Welding at TWI] and [https://www.twi-global.com/search-results.aspx#/?term=rotary%20friction%20welding search-results at TWI]

{{Metalworking navbox/weld}}

[[Category:Welding]]