Vpliv parametrov laserskega udarnega utrjevanja na zaostale napetosti v visoko-trdnostnih aluminijevih zlitinah

Ahačič, Jan (author), Trdan, Uroš (mentor), BERTHE, Laurent (comentor)

Izločevalno utrjene, visokotrdnostne aluminijeve (Al) zlitine so v industriji pomemben ter nepogrešljiv material predvsem zaradi dobrega razmerja med trdnostjo in gostoto. V letalski industriji so tako še vedno pogosto v uporabi, kljub velikemu porastu kompozitnih materialov z ogljikovimi vlakni, ojačanega z epoksidno matrico. Vendar pa izpostavljenost izrednim razmeram v aviaciji, kot so visoko-ciklično utrujanje ter korozijska degradacija, zahteva dodatno tehnologijo površinskega utrjevanja. Novodobna tehnologija laserskega udarnega utrjevanja (LSP) počasi, a vztrajno izpodriva konvencialno kinetično utrjevanje s kroglicami (SP), saj omogoča višjo kontrolo obdelovalnosti, odsotnost kontaminacije ter vnos višjih tlačnih zaostalih napetosti v tankem površinskem sloju materiala. V zaključni nalogi smo preučevali vpliv različnih parametrov LSP tretiranja na vnešene zaostale napetosti na vzorcih iz Al zlitin 2017A-T451 ter 7075-T651. Analizirali smo vpliv dveh različnih prevlek (Al trak in črni PVC), različnih gostot moči ter števila prehodov. Z metodo rentgenske difrakcije (XRD) smo tako izmerili zaostale napetosti na LSP obdelani površini ter na nasprotni/neobdelani strani 10mm debilih Al plošč. Rezultati analiz so potrdili največje tlačne zaostale napetosti, ki jih na površju dosežemo z uporabo črne PVC zaščitne prevleke, višje gostote moči ter ob uporabi večjega števila prehodov laserskega snopa preko površine. Največje vrednosti tlačnih zaostalih napetosti smo dobili pri večji gostoti moči (8 GW/cm2), največjem številu prehodov (3) ter pri uporabi črnega PVC traku, kjer so tlačne zaostale napetosti v transverzalni smeri znašale -420 MPa v primeru zlitine Al 2017A-T451 ter -421 MPa v primeru zlitine Al 7075A-T651. Največje tlačne zaostale napetosti na neobdelani/nasprotni strani LSP so bile dosežene pri zlitini Al 7075A-T651, obdelane z največjo gostoto moči, največjim številom prehodov ter z uporabo črnega PVC zaščitnega medija.

• Language: Slovenian
• Keywords: visoko-trdnostne aluminijeve zlitine, površinsko utrjevanje s plastično deformacijo, lasersko udarno utrjevanje, zaostale napetosti, rentgenska difrakcija
• Work type: Final paper
• Typology: 2.11 - Undergraduate Thesis
• Organization: FS - Faculty of Mechanical Engineering
• Place of publishing: Ljubljana
• Publisher: [J. Ahačič]
• Year: 2021
• Number of pages: XIX, 51 str.
• PID: 20.500.12556/RUL-130439
• UDC: 669.715:620.179:621.9.048(043.2)
• COBISS.SI-ID: 76935939
• Publication date in RUL: 15.09.2021

AHAČIČ, Jan, 2021, Vpliv parametrov laserskega udarnega utrjevanja na zaostale napetosti v visoko-trdnostnih aluminijevih zlitinah [online]. Bachelor’s thesis. Ljubljana : J. Ahačič. [Accessed 28 March 2025]. Retrieved from: https://repozitorij.uni-lj.si/IzpisGradiva.php?lang=eng&id=130439

Secondary language

• Language: English
• Title: Effect of laser shock peening parameters on residual stresses in high-strength aluminium alloys

Abstract

Precipitation hardened aluminium alloys are a very important and infallible material in industry mostly because of their good density/strength ratio. They are used especially a lot in aviation industry despite a large increase in epoxy matrix reinforced carbon fiber composite materials. Because of the exposure to extreme conditions in aviation, such as high-cycling fatigue and corrosive degradation, additional technology for surface hardening is neded. The modern method of Laser Shock Peening (LSP) is slowly but persistantly displacing the conventional kinetic method of Shock Peening (SP), because it allows more workability control, absence of contamination and imparting of higher residual stress into the thin surface of the material. In this thesis we have studied the effect of differen LSP treatment parameters on entered residual stress on samples of Al alloys 2017A-T451 and 7075-T651. We have analized the impact of two different coatings (Al tape and black PVC tape), different power densities and also different numbers of passes. By using x-ray diffraction (XRD) method we have measured residual stresses on the treated surface and on the other/untreated side of the Al plates with 10mm thickness. The results of the analys have confirmed that largest residual stress has been entered using black PVC tape as coating, higher power density and larger number of laser beam passes across the surface. The highest compressive residual stresses were obtained using highest power density (8 GW/cm2), highest number of passes (3) and with the use of black PVC tape, where the compressive residual stresses in transversal direction were -420 MPa for 2017A-T451 and -421 MPa for 7075A-T651 Al alloy. The highest residual stresses on the untreated/opposite side were confirmed with alloy Al 7075A-T651, treated with the highest power density, highest number of passes and coated with black PVC tape.

• Keywords: high-strength aluminium alloys, surface peening of aluminium alloys, laser shock peening (LSP), residual stress, x-ray diffraction