Numerička simulacija postupka kutne ekstruzije

master's thesis

• Title (english): Numerical simulation of equal channel angular extrusion
• Author: Mirko Rožman
• Mentor: Zdenka Keran (mentor)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2018-12-06, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mechanical Engineering

Abstract

Kutna ekstruzija (eng. Equal Channel Angular Pressing, ECAP) glavni je predstavnik postupaka značajne plastične deformacije (eng. Severe Plastic Deformation, SPD). ECAP omogućava postizanje sitnozrnate mikrostrukture kod metalnih materijala, a samim time i poboljšanje njihovih mehaničkih svojstava. Kako bi se konstruirao alat za kutnu ekstruziju bitno je poznavati utjecaj konstrukcije samog alata na ponašanje i distribuciju deformacije u materijalu te nastala naprezanja. U ovome radu, numeričkim modeliranjem analiziran je utjecaj jednog od najbitnijih parametara ovoga procesa - kuta između ulaznog i izlaznog kanala matrice (Φ). U prvom dijelu rada ukratko je predstavljen postupak kutne ekstruzije te metoda konačnih elemenata. Zatim je ispitan utjecaj četiriju različitih konstrukcija alata na raspodjelu naprezanja prilikom obrade uzorka od čistog aluminija i prokomentirani su rezultati. Također, simulacija je provedena u dvodimenzionalnom i trodimenzionalnom sustavu te su uspoređeni dobiveni rezultati. Kao posljednji dio rada, eksperimentalno je proveden postupak kutne ekstruzije na aluminijskom uzorku i to u alatu s matricom čiji su ulazni i izlazni kanali pod kutom od 90°. Ovim eksperimentom izmjereni su slijedeći podaci: ovisnost sile oblikovanja o vremenu te tvrdoća uzorka prije i poslije deformacije. Na samom kraju prokomentirani su svi dobiveni rezultati te se na temelju usporedbe podataka svih analiza izvukao zaključak o pozitivnim i negativnim stranama pojedinih konstrukcija alata i pretpostavke o svojstvima materijala koja se mogu postići određenom konstrukcijom.

Abstract (english)

Equal Channel Angular Pressing – ECAP (or Equal Channel Angular Extrusion – ECAE) represents the main process of Severe Plastic Deformation – SPD processes. ECAP ensures refined grain microstructure to be achieved in metal materials, thus improving their mechanical properties. In order to design a die for ECAP, it is important to know the die design influence on behavior and distribution of stress and strain being imposed to material. In this paper, numerical modeling is used for analysis of influence of one of the most significant parameters of this process – the angle between channels of the die (Φ). At the beginning of paper, a short introduction about ECAP and Finite Element Method (FEM) is given. Then, analysis of influence of four different die designs is carried out and results are discussed. Stress distribution in these cases are investigated on pure aluminum workpiece. Furthermore, simulation is carried out in two-dimensional and threedimensional system and the results are compared. As a final part, an experiment of ECAP is carried out on an aluminum sample in a tool with an angle of 90° between channels of the die. This experiment is used to measure following information: deforming force over time distribution, and sample hardness before and after deformation. At the end, all obtained results are discussed and conclusion is extracted based on comparison of the results from all analyses. Positive and negative sides of each tool designs are given as well as assumptions on material properties that can be achieved with each design.

• Keywords: kutna ekstruzija; numerička analiza; metoda konačnih elemenata; obrada metala; mehanička svojstva
• Keywords (english): Equal Channel Angular Extrusion; Numerical analysis; Finite Element Method; Metal processing; Mechanical properties
• Language: croatian
• URN:NBN: urn:nbn:hr:235:822174
• Study programme: Title: Mechanical Engineering; 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: 2019-05-24 12:38:25