Vpliv skupkov nehomogenosti zaradi tlačnega litja na dobo trajanja ulitkov

Tomažinčič, Dejan (author), Klemenc, Jernej (mentor)

Pri obravnavi ulitkov se večina dosedanjih raziskav omejuje le na vpliv posameznih, izoliranih por. Ta doktorska naloga se zato osredotoča na slabše raziskano področje vpliva obsežne makro poroznosti na dobo trajanja. Gre za celovito raziskavo pogosto uporabljene aluminijeve zlitine v livarski industriji AlSi9Cu3. Pomemben segment raziskav predstavlja opis ugotovljenih makro poroznih defektov, tj. por in hladnih spojev, s tehniko z voksli, ki je nato primerjana še z alternativno tehniko opisa defektov z vektorsko segmentacijo. Povratni inženiring poroznosti je izveden na osnovi µ-CT posnetkov in nato uporabljen za numerični izračun dobe trajanja po teoriji malociklične trdnosti, s komercialnim paketom SIMULIA (Abaqus in fe-safe). Študija služi kot pomoč pri oceni, kdaj so odlitki lahko še uporabni in kdaj so tveganja za hitre iniciacije poškodb zaradi prisotnih por prevelika. Skozi analize lahko primerjamo različne metalurške defekte in dobimo vpogled, kateri bolj in kateri manj vplivajo na znižanje dinamične nosilnosti. V raziskave so vključene tudi eksperimentalno-teoretične primerjave zdržljivosti različnih celičnih struktur z negativnim Poissonovim razmerjem iz zlitine Al7075-T651. Skupni rezultati kažejo na pridobitev koristnih novih orodij, ki jih lahko uporabimo pri ocenjevanju tako urejenih kot tudi naključnih poroznih struktur, ali te še vedno omogočajo funkcionalno delovanje in zahtevano trajnost izdelka.

• Language: Slovenian
• Keywords: aluminijeva zlitina, visokotlačno litje, makro poroznost, avksetičnost, povratni inženiring, malociklična trdnost, metoda končnih elementov, poškodba, Taguchijeva metoda, disipacija energije
• Work type: Doctoral dissertation
• Typology: 2.08 - Doctoral Dissertation
• Organization: FS - Faculty of Mechanical Engineering
• Place of publishing: Ljubljana
• Publisher: [D. Tomažinčič]
• Year: 2021
• Number of pages: XXVI, 149 str.
• PID: 20.500.12556/RUL-130440
• UDC: 621.74:669.715:539.217(043.3)
• COBISS.SI-ID: 76936451
• Publication date in RUL: 15.09.2021

TOMAŽINČIČ, Dejan, 2021, Vpliv skupkov nehomogenosti zaradi tlačnega litja na dobo trajanja ulitkov [online]. Doctoral dissertation. Ljubljana : D. Tomažinčič. [Accessed 31 March 2025]. Retrieved from: https://repozitorij.uni-lj.si/IzpisGradiva.php?lang=eng&id=130440

Secondary language

• Language: English
• Title: Influence of inhomogeneity clusters to fatigue life of dye-casted products

Abstract

When dealing with casted parts most research to this date is limited to the influence of individual and isolated pores. This doctoral dissertation therefore focuses on the less researched area of the influence of large-scale macro porosity on fatigue life. It is a comprehensive study of commonly used aluminium alloy in the foundry industry AlSi9Cu3. An important segment of research is a description of the identified macroporous defects, i.e. pores and cold shuts with the voxel technique, which is then compared with the alternative technique of defect description using a vector segmentation technique. By applying a reversed engineering the porosity is modelled on the basis of μ-CT scans and then used for the numerical calculation of the fatigue life according to the theory of low-cyclic fatigue with the commercial SIMULIA software (Abaqus and fe-safe). The study serves as an aid in assessing when castings parts may still be useful and when the risks of rapid initiation of fatigue damage due to the pore clusters present are too great. Through analyses, different metallurgical defects can be compared and estimated which defects have greater and which less effect on the reduction of fatigue life. Experimental-theoretical comparisons of the durability of different cellular structures with a negative Poisson ratio from the Al7075-T651 alloy are also included in the research with an objective to first test the proposed methodology on the cases of regular geometric inhomogeneities. The overall results indicate the acquisition of useful new tools that can be used to assess both the ordered and random porous structures, in order to assess whether these still allow functional operation and the required fatigue life of the product.

• Keywords: aluminium alloy, high-pressure die casting, macroporosity, auxetics, reverse engineering, low-cycle fatigue, finite element method, damage, Taguchi method, energy dissipation