@phdthesis{
author = "Eramah, Abdsalam M.",
year = "2014",
abstract = "Friction stir welded is relatively new- solid-states joining process for welded several material such as aluminum, copper, titanium and magnesium. Also FSW technique is preformed in solid state without melting hence avoiding hot cracking. In this research selected aluminum 5083 alloy, it is widely used in applications in which the combination of strength and low weight is attractive. In friction stir welding (FSW) pin connected to a shoulder in rotated and slowly plunged into the joint line between two pieces of plats. When the shoulder tools rotation and contact the material surface, it generated friction heating between the welding tool and the material of the work pieces. This heat causes the latter soften without reaching the melting point and allows traversing of tool along the welding. Friction stir welding presents several benefit for joining of various alloys, specially of aluminum alloy one of the significant advantage of FSW is the heat inputs are small relative to fusion welding techniques and due to the low temperature of the process, material such as Al, Cu, Mg alloys that cannot be welded by fusion processes are easily weld by FSW. On the other hand, FSW has some drawback is often slower traverse rate then some fusion welding and exit hole left when tool is withdrawn.
Friction stir welding process generates three distinct microstructural zones that result from the welding process as following: nugget zone also known as the dynamically recrystallized zone (DRZ) where the tool piece pin passes into this zone and by experience, it has high deformation and high heat, generally consists of fine equated grains due to recrystallisation, the thermo mechanically affected zone (TMAZ) and the heat affected zone (HAZ), all zones together are called welding zone. After welded aluminum alloy tested specimens alloy by charpy impact test to evaluate absorbed energy caused the fracture material and toughness of material. Also obtained high resolution images by macro-photographs and by scanning electron microscope (SEM) to evaluate type of surface fracture and detected fracture and micro void in material then analysis material by energy dispersive x-ray spectroscopy (EDX) to shown distribution elements of chemical compound in aluminum alloy after heating and cooling precipitation. Finally, selection the optimized FSW parameters for welded aluminum 5083 alloy, it achieved higher fracture resistance in welded zone of alloy., Frikciono zavarivanje mešanjem predstavlja relativno nov, savremen postupak zavarivanja velikog broja materijala, kao što su legure aluminijuma, bakra, titanijuma, magnezijuma itd. Jedinstvena osobina ovog postupka je da se odvija u čvrstom stanju, bez pojave topljenja. U ovoj disertaciji, ispitivana je Al-Mg legura 5083, koju odlikuje dobra kombinacija čvrstoće, žilavosti i otpornosti na koroziju. Tokom frikcionog zavarivanja mešanjem, specijalno dizajniran alat, koji se rotira, prodire u materijal, upravo u liniji spajanja dve ploče koje se zavaruju. Na kontaktnoj površini oslobađa se toplota koja omekšava materijal, olakšava kretanje alata uz istovremeno mešanje materijala. Ovako zavreni spojevi imaju čitav niz prednosti u odnosu na klasično zavarene spojeve – ukupna potrošnja energije daleko je manja, nema pojave tečnih faza, čvrstoća spoja često bude veća nego kod osnovnog materijala i, konačno, nema štetnih uticaja na prirodnu okolinu. Postoje, naravno, i nedostaci ove tehnologije, pre svega povezani sa dužinom zavarenih spojeva koja zavisi od dimenzija mašine na kojoj se postupak izvodi.
Tokom ovog postupka zavarivanja, u zoni zavarenih spojeva javljaju se jasno definisane zone uticaja toplote, kao i kod postupka klasičnog zavarivanja. Međutim, kod frikcionog zavarivanja mešanjem, pojavljuje se i zona termo-mehaničkog uticaja pod simultanog dejstva toplote i plastične deformacije materijala. U ovoj disertaciji, ispitivan je uticaj procesnih parametara frikcionog zavarivanja na čvrstoću zavarenih spojeva. Ispitivan je uticaj (i) rotacione brzine zavarivanja (u opsegu 500 do 800 obrtaja u minuti), (ii) uticaj translacione brzine (75-150 mm/min) i, (iii) uticaj napadnog ugla alata (1°-4°). Svi zavareni spojevi ispitivani su na otpornost prema udarnoj žilavosti. Numeričkom obradom eksperimentalnih rezultata, određena je udarna žilavost zavarenih spojeva kao i brzina i energija loma. Pored mehaničkih ispitivanja, izvršena su opsežna mikrostrukturna ispitivanja primenom optičkog i skening elektronskog mikroskopa (SEM). Ova ispitivanja omogućila su bolji uvid u mehanizam i kinetiku duktilnog loma zavarenih spojeva. Konačno, na osnovu analize mehaničkih i mirostrukturnih ispitivanja, određeni su optimalni parametri frikcionog zavarivanja ispitivane legure.",
journal = "Univerzitet u Beogradu, Mašinski fakultet",
title = "Friction stir welding parameters influencing the fracture resistance of an Al 5083 alloy welded joint, Uticaj parametara frikcionog zavarivanja mešanjem na otpornost na lom zavarenog spoja legure Al 5083",
url = "https://hdl.handle.net/21.15107/rcub_machinery_6538"
}
