Numerička analiza zaostalih naprezanja i deformacija kod zavarivanja

Putar, Filip (2014) Numerička analiza zaostalih naprezanja i deformacija kod zavarivanja. = Numerical Analysis of Welding Residual Stresses and Deformations. Master's thesis (Bologna) , Sveučilište u Zagrebu, Fakultet strojarstva i brodogradnje, UNSPECIFIED. Mentor: Tonković, Zdenko.

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Abstract (Croatian)

Tema ovog diplomskog rada je numerička analiza zaostalih naprezanja i deformacija pri zavarivanju. Zaostala naprezanja imaju vrlo važan utjecaj na cjelovitost komponente i procjenu radnog vijeka zavarenih konstrukcija. Procjena zaostalih naprezanja numeričkim modeliranjem zavarivanja je računalno vrlo skup postupak. Stoga je većina simulacija zavarivanja provedena uz odgovarajuća pojednostavljenja, kao što je reduciranje trodimenzijskog problema na dvodimenzijski. Prije same numeričke analize koja je vršena metodom konačnih elemenata u programskom paketu Abaqus, ukratko su iznesene teorijske osnove modeliranja procesa zavarivanja u pogledu izmjene topline i elastoplastičnog ponašanja materijala. Također, objašnjeno je nastajanje zaostalih naprezanja i deformacija u zavarenim konstrukcijama te je izvršena njihova podjela. \Numeričko modeliranje procesa zavarivanja započeto je kratkim osvrtom na vrste toplinsko-mehaničkih analiza kao i na jednadžbe konačnih elemenata za nelinearnu toplinsku i mehaničku analizu, pri čemu je za nelinearnu mehaničku analizu objašnjen i proces dobivanja rješenja. Pokazane su osnove rješavanja nelinearnih problema inkrementalno-iterativnim metodama te je dan pregled konačnih elemenata korištenih u simulacijama zavarivanja. Provedeno je modeliranje procesa zavarivanja dviju sučeono zavarenih ploča primjenom klasične metode i metode rađanja elemenata. Klasičnom metodom analizirani su potpuni 3D model, potpuni ljuskasti model te dva 3D/ljuskasta modela različitih širina 3D zona u svrhu određivanja kriterija prijelaza s 3D na ljuskastu zonu. Metoda rađanja elemenata je kao fizikalno točnija metoda modeliranja zavarivanja upotrijebljena za analizu 3D modela kako bi se ustvrdila točnost klasične metode. Sa zaključcima dobivenima pri analizi zavarivanja dviju sučeono zavarenih ploča pristupilo se modeliranju procesa zavarivanja poklopca rebra linera pri montaži na konstrukciju ispušnog kućišta plinske turbine tvrtke Alstom te je izvršena analiza zaostalih naprezanja i deformacija.

Abstract

Subject of this master thesis is numerical analysis of residual stresses and deformations in welded structures. Residual stresses are an important factor in the component integrity and life assessment of welded structures. Prediction of residual stresses by numerical modeling of welding process is computational very expensive. Most of the welding simulations are performed with certain level of simplifications such as reducing a three dimensional problem to a two dimensional. Before numerical analysis which was performed by using finite element method in Abaqus software package, theoretical fundamentals of welding process modelling concerning heat transfer and elastoplastic behaviour of materials were briefly given. Formation of residual stresses and deformations in welded structures was explained. Classification of residual stresses and deformations was also given. Numerical modeling of welding process was started with a brief review of types of thermal-stress analyses as well of finite element equations for nonlinear thermal and stress analyses. Process of solution obtaining for nonlinear stress analysis was explained. Fundamentals of incremental-iterative methods were shown and overview of used finite elements was given. Welding process modeling of two butt welded plates by use of classical techniqe and element birth technique was carried out. By use of classical technique full 3D model, full shell model and two 3D/shell models with different sizes of 3D zones were analysed for the purpose of transition criterion determination from 3D to shell zone. As physicaly more accurate technique of welding process modeling, element birth technique was used only for 3D model analysis, so that accuracy of classical technique could be verified. With conclusions obtained in two butt-welded plates welding analyses, it was approached to welding process modeling of liner rib cover during assembly on construction of exhaust housing of gas turbine provided by Alstom company. Analysis of residual stresses and deformations was carried out.

Item Type: Thesis (Master's thesis (Bologna))
Uncontrolled Keywords: metoda konačnih elemenata; zavarivanje; sučeono zavarene ploče; zaostala naprezanja
Date Deposited: 22 Sep 2014 18:00
Last Modified: 16 Oct 2015 12:48
URI: http://repozitorij.fsb.hr/id/eprint/2829

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