magistrsko delo
Nebojša Ilić (Author), Srečko Glodež (Mentor), Janez Kramberger (Co-mentor)

Abstract

Magistrsko delo obravnava dva različna pristopa k numerični analizi utrujanja komponente na dizelskem motorju. Analiziral se je nosilec EGR sistema, ki je privijačen na blok motorja. Vibracije pri obratovanju motorja povzročajo utrujanje materiala nosilca. Cilj magistrskega dela je s pomočjo MKE analize izračunati življenjsko dobo EGR nosilca. Na začetku so predstavljene osnove sestave dizelskega motorja in položaj obravnavanih komponent. Razloženo je tudi teoretično ozadje dimenzioniranja dinamično obremenjenih komponent. Prvi pristop zajema izračun življenjske dobe nosilca s pomočjo napetostne metode in statične numerične analize. Dobljeni rezultati prve analize prikazujejo porazdelitev napetosti po numeričnem modelu. Napetosti so bile precej pod pričakovanim velikostnim razredom, kar kaže na neprimernost prvega pristopa. Takšen način analize ne upošteva dinamičnih karakteristik nosilca, zato je v nadaljevanju predstavljen še drugi pristop, ki se imenuje analiza vibracijskega utrujanja. Ta analiza je bila opravljena s pomočjo namenskega programskega paketa za analize utrujanja fe-safe. Program omogoča posebno PSD analizo, ki upošteva lastne frekvence in harmonične lastnosti modela. Pri PSD analizi utrujanja se morajo obremenitve pretvoriti iz časovne domene v frekvenčno domeno. Predhodno je bilo potrebno opraviti analizo lastnih frekvenc ter analizo harmoničnega vzbujanja. Opravljene so bile še meritve vibracij na traktorskem dizelskem motorju. Iz rezultatov meritev smo naredili PSD diagram. Vse potrebne podatke smo uvozili v fe-safe, s pomočjo katerega smo izračunali življenjsko dobo nosilca. Rezultati PSD analize so po pričakovanju pokazali, da se v nosilcu ne pojavijo utrujenostne poškodbe, zato lahko sklepamo, da nosilec doseže neskončno življenjsko dobo. Nato je bila narejena še PSD analiza s FRF algoritmom, pri kateri se je izračunal varnostni faktor. Rezultate te analize si je mogoče grafično ogledati na numeričnem modelu.

Keywords

življenjska doba;vibracije;numerična analiza;frekvenčna domena;PSD;magistrske naloge;

Data

Language: Slovenian
Year of publishing:
Typology: 2.09 - Master's Thesis
Organization: UM FS - Faculty of Mechanical Engineering
Publisher: [N. Ilić]
UDC: [519.6:620.178.3]:629.3.026(043.2)
COBISS: 18867734 Link will open in a new window
Views: 1387
Downloads: 113
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Other data

Secondary language: English
Secondary title: Designing of bracket for EGR system
Secondary abstract: The master’s thesis addresses two different approaches of numerical fatigue analysis of diesel engine components. The bracket of EGR system was analysed, which is mounted onto the engine block with bolts. The vibrations of running engine cause the fatigue of the bracket’s material. The main goal of this master’s thesis is to calculate the lifetime of the EGR bracket with the help of FEA analysis. The basics of diesel engine structure and the position of the addressed components are represented at the beginning. The theoretical background of the dimensioning of the components with dynamical loading is also explained. The first approach involves the calculation of the bracket’s lifetime with the help of stress life approach and static numerical analysis. The results of the first analysis show the distribution of the stresses on the numerical model. The stresses have been quite below the expected value range, which indicates the unsuitability of the first approach. This kind of analysis does not take into consideration the dynamical characteristics of the bracket, this is why a second approach is represented, which is called a vibration fatigue analysis. This analysis has been done with the help of specialized program for fatigue analyses fe-safe. This program allows the use of a special PSD analysis, which takes into consideration the natural frequencies and harmonic properties of a model. PSD fatigue analysis requires that loading definition is transferred from time domain into frequency domain. We preliminary had to made natural frequency analysis and harmonic response analysis. The measurements of the vibrations on diesel engine were also made. From the gained measurements we made a PSD diagram. We had to import all the necessary data into fe-safe and then with its help we calculated the lifetime of a bracket. The results of PSD analysis have showed as expected that the fatigue damages do not occur on a bracket, this is why we assume that a bracket reaches an infinite lifetime. Afterwards a PSD analysis with a FRF algorithm was done, where a reserve factor was calculated. The results of this analysis can be graphically seen on a numerical model.
Secondary keywords: lifetime;vibrations;numerical analysis;frequency domain;PSD;
URN: URN:SI:UM:
Type (COBISS): Master's thesis/paper
Thesis comment: Univ. v Mariboru, Fak. za strojništvo
Pages: X, 50 f.
ID: 8757626