Fatigue analysis of seam welds in lightweight aluminum structures

master's thesis

• Title (croatian): Analiza zamora šavnih zavara u lakim aluminijskim konstrukcijama
• Author: Mislav Vukić
• Mentor: Zdenko Tonković (mentor)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2021-12-17, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mechanical Engineering; General Mechanical Engineering (Construction)

Abstract

Continuous advancements in the electrification of the whole automotive industry rely heavily on the use of lightweight materials. Due to the overall requirements for mass reduction that such rapid development imposes, lightweight materials such as aluminum play a major role in the optimization and development of powertrain components and vehicles while at the same time ensuring the structural integrity of the system.
In the introduction of this thesis a short overview of the four most common fatigue assessment methods is given which includes the description of the approaches based on nominal stress, structural hot spot stress, and effective notch stress as well as the crack propagation analysis. In the continuation of the thesis the focus will be on the fatigue assessment of weld seams joining extruded aluminum profiles with the use of modern-day fatigue assessment tools. A closer look will be given into the notch stress-based method behind FEMFAT Weld analysis tool and its benefits for the weld seam fatigue investigations. The fatigue assessment method for welded components proposed by FEMFAT Weld will be validated on an example of welded aluminum profiles from the literature before final experimental investigations begin. In the main focus of the work will be the high cycle fatigue testing of two different weld seams, I-seam butt weld and corner fillet weld, both made of extruded aluminum profiles. Along with the high cycle fatigue testing, additional microscopic measurements of the weld geometry and hardness will be performed. The results of such investigations will be used to conduct a thorough investigation of FEMFAT Weld in order to understand the notch stress methods that are being used and apply them in the desired way. The final results of fatigue assessment with the use of FEMFAT Weld analysis tool will be compared to the results from high cycle fatigue tests and certain conclusion will be drawn. In the end the work from this thesis will represent a detailed overview of FEMFAT Weld assessment tool and clear instructions on how to customize it to specific needs in respect to weld fatigue assessment.

Abstract (croatian)

Neprestani napredak u elektrifikaciji cijele automobilske industrije uvelike se oslanja na korištenje lakih materijala. Zbog općih zahtjeva i potreba za smanjenjem mase koje nameće takav napredak, laki materijal kao što je aluminij igraju bitnu ulogu u optimizaciji i razvoju komponenti kako pogonskog sklopa tako i cijelog vozila, dok u isto vrijeme moraju osigurati strukturalni integritet cijelog sustava.
U uvodu ovog diplomskog rada dan je kratak pregled četiri najčešće metode procjene zamora koji uključuje opis pristupa temeljenih na nominalnom naprezanju, strukturnom „hot spot“ naprezanju i efektivnom zareznom naprezanju, kao i opis analize propagacije pukotine. U nastavku rada fokus će biti na procjeni zamora šavnih zavara koji spajaju ekstrudirane aluminijske profile uz korištenje suvremenih alata za procjenu zamora. Detaljnije će se razmotriti metoda koja stoji iza FEMFAT Weld simulacijskog alata, a temelji se na zareznom naprezanju, kao i njene prednosti u procjeni zamora. Metoda procjene zamora za zavarene komponente koju predlaže FEMFAT Weld bit će provjerena na primjeru zavarenih aluminijskih profila preuzetom iz literature, prije samog početka eksperimentalnih ispitivanja. U glavnom fokusu rada bit će ispitivanje visokocikličkog zamora dvaju različitih šavnih zavara izrađenih od ekstrudiranih aluminijskih profila, sučeonog I-zavara i kutnog zavara. Uz visokocikličko ispitivanje zamora, izvršit će se i dodatna mikroskopska mjerenja geometrije te mjerenje tvrdoće zavara. Rezultati tih istraživanja poslužit će za provedbu temeljitog istraživanja FEMFAT Weld alata kako bi se bolje razumjele metode zareznih naprezanja koje se koriste kako bi ih se moglo primijeniti na željeni način. Konačni rezultati procjene zamora korištenjem FEMFAT Weld alata usporedit će se s rezultatima ispitivanja visokocikličkog zamora te će se izvući odgovarajući zaključci. Ovaj diplomski rad na kraju će predstavljati detaljan pregled FEMFAT Weld simulacijskog alata i jasne upute kako ga prilagoditi specifičnim potrebama u pogledu procjene zamora zavarenih spojeva.

• Keywords: fatigue assessment; seam weld; aluminum; FEMFAT Weld; notch stress
• Keywords (croatian): procjena zamora; šavni zavar; aluminij; FEMFAT Weld; zarezno naprezanje
• Language: english
• URN:NBN: urn:nbn:hr:235:072463
• Study programme: Title: Mechanical Engineering; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka strojarstva (magistar/magistra inženjer/inženjerka strojarstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2021-12-02 11:23:42