Numeričko modeliranje procesa deformiranja heterogenoga sinteriranoga materijala na mikrostrukturnoj razini

master's thesis

• Title (english): Numerical modelling of heterogeneous sintered material deformation processes at the microstructural level
• Author: Benjamin Pavlović
• Mentor: Zdenko Tonković (mentor)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2022-07-20, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mechanical Engineering; Precision Mechanical Engineering

Abstract

Sinterirani materijali su u posljednje vrijeme postali neizostavan dio u sustavima prijenosa snage i gibanja. Zbog relativno niskih troškova proizvodnje, visoke iskoristivosti materijala, smanjenja buke i vibracija te ekološke prihvatljivosti sinterirani materijali imaju veliku prednost u odnosu na klasične materijale. Jedan od problema sinteriranih materijala je poroznost zbog koje dolazi do koncentracije naprezanja na mikrorazini što pospješuje nastanak i razvoj oštećenja u materijalu.
Dobivenim rezultatima metalografske analize u ovom radu je provedeno numeričko modeliranje procesa deformiranja heterogenog sinteriranog materijala Astaloy Mo+0,2C na mikrostrukturnoj razini za konstitutivne modele oštećenja i elastoplastičnog ponašanja materijala. Analizirane su tri različite gustoće sinteriranih čelika i posebno za svaku gustoću tri različite veličine modela. Dvodimenzionalni heterogeni modeli sastoje se od kristalnih zrna ferita i bainita te pora. Svojstva ferita i bainita su dobivena preko instrumentirane metode utiskivanja. Predprocesiranje, procesiranje i postprocesiranje je provedeno u programskom paketu Abaqus koji se temelji na metodi konačnih elemenata. Nakon numeričke simulacije prikazan je utjecaj različitih veličina modela te utjecaj različitih poroznosti za elastično i elastoplastično ponašanje materijala te za elastoplastično ponašanje materijala s oštećenjem.
Rad je koncipiran tako da je dan kratki uvod o metalurgiji praha i sinteriranim čelicima. Nakon toga su opisani konstitutivni modeli ponašanja materijala korištenih u ovom radu. Kratko je opisana instrumentirana metoda utiskivanja na mikrorazini i rekonstrukcija podataka za dobivanje materijalnih svojstava korištenih u ovom radu. Dan je uvid u metodu konačnih elemenata i prikazana je formulacija dvodimenzionalnih elemenata korištenih za numeričku simulaciju. Na kraju je opisan postupak predprocesiranja modela te su analizirani rezultati. Rezultati numeričkih analiza uspoređeni su s eksperimentalnim rezultatima na makrorazini dobivenih putem jednoosnih testova. Na kraju, prema rezultatima dan je zaključak.

Abstract (english)

Sintered materials have recently become an indispensable part of power and motion transmission systems. Due to relatively low production costs, high material efficiency, reduced noise and vibration, and low environmental impact, sintered materials have a great advantage over classic materials. One of the problems of sintered materials is porosity, due to which there is a microlevel stress concentration which promotes the initiation and propagation of damage in the material.
Using the obtained results of metallographic analysis, numerical modeling of the deformation process of the heterogeneous sintered material Astaloy Mo+0.2C at the microstructural level was carried out in this work for constitutive models of damage and elastoplastic behaviour of the material. Three different densities of sintered steels were analysed and separately for each density three different model sizes. Two-dimensional heterogeneous models consist of crystalline grains of ferrite and bainite and pores. The properties of ferrite and bainite were obtained through the instrumented indentation method. Preprocessing, processing and postprocessing was performed in the Abaqus software package, which is based on the finite element method. After the numerical simulation, the influence of different sizes and the influence of different porosity for the elastic and elastoplastic behaviour of the material and for the elastoplastic behaviour of the material with damage is shown.
The paper is designed in such a way that a short introduction to powder metallurgy and sintered steels is given. After that, the constitutive models of the behaviour of the materials used in this work are described. The instrumented micro-level indentation method and data reconstruction to obtain the material properties used in this work are briefly described. An insight into the finite element method is given and the formulation of two-dimensional elements used for numerical simulation is presented. At the end, the model preprocessing procedure is described, and the results are analysed. The results of the numerical analyses were compared with the experimental results at the macro level obtained through uniaxial tests. Finally, according to the results, a conclusion is given.

• Keywords: elastoplastični model; koncentracija naprezanja; metalografska analiza; numerička analiza; poroznost; sinterirani čelik; heterogenost
• Keywords (english): elastoplastic model; heterogeneity; metallographic analysis; numerical analysis; porosity; sintered steel; stress concentration
• Language: croatian
• URN:NBN: urn:nbn:hr:235:129506
• Study programme: Title: Mechanical Engineering; specializations in: Design, Process and Energy Engineering, Production Engineering, Engineering Modelling and Computer Simulation, Marine Engineering, Industrial Engineering and Management, Materials Engineering, Mechatronics and Robotics, Autonomous Systems; Course: Engineering Modelling and Computer Simulation; 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: 2022-07-06 12:59:37