Numerička analiza višeosnog Arcan prihvata i optimizacija dimenzija leptirastog ispitnog uzorka

master's thesis

• Title (english): Numerical analysis of a multiaxial Arcan rig and geometry optimization of a butterfly sample
• Author: Danijel Janković
• Mentor: Zvonimir Tomičević (mentor)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2017-12-08, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mechanical Engineering

Abstract

Eksperimentalna mehanička istraživanja zahtjevaju pouzdano prenošenje željenog opterećenja na ispitni uzorak. Konstruiranje naprednih mehaničkih prihvata podrazumijeva numeričke proračune eksperimentalnog ispitivanja s ciljem unaprijeđenja ispitne metode. U ovom radu provedena je numerička analiza višeosnog Arcan prihvata te su optimirane dimenzije leptirastog ispitnog uzorka.

Cilj ovoga rada je primjenom numeričkih simulacija oponašati mehanički eksperiment i tako provjeriti krutost mehaničkog prihvata s ciljem osiguranja što pouzdanijeg višeosnog opterećenja tijekom realnog eksperimentalnog istraživanja. Budući da je razmatran višeosni prihvat koji omogućava različite režime ravninskog dvoosnog opterećenja, numerički je izmjerena raspodjela pomaka na leptirastom ispitnom uzorku s obzirom na vlačno i smično opterećenje te njihovu kombinaciju kod kojeg je uzorak opterećen pod 45°. Ispitana je i teoretska raspodjela pomaka na idealiziranom ispitnom uzorku s idealnim rubnim uvjetima te je uspoređena s numeričkim rezultatima dobivenim analizom prihvata. U sklopu primjene metode konačnih elemenata provedeni su različiti verifikacijski primjeri kako bi se procijenila točnost u korištene konačne elemente, rubne uvjete, način opterećenja i metodu definiranja kontakta.

U rada je također optimirana geometrija leptirastog ispitnog uzorka primjenom polja osjetljivosti. Ponašanje materijala ispitnog uzorka opisano je elastoplastičnim konstitutivnim zakonom uzimajući u obzir Armstrong Frederickovo kinematsko očvršćenje. Razvijenim iterativnim algoritmom optimirane su dvije karakteristične dimenzije uzorka (radijus R i kut α) koje definiraju dva simetrična V zareza. Povećanjem polja osjetljivosti pomaka i vektora osjetljivosti sila predloženog ispitnog uzorka određene su optimalne dimenzije za tri slučaja ravninskog stanja naprezanja.

Abstract (english)

Experimental mechanical studies require a reliable transfer of the desired load to the test sample. The design of advanced mechanical grips implies numerical calculations of experimental testing with the aim of improving the test method. In this thesis, a numerical analysis of the multiaxial Arcan rigs was performed. Furthermore, the geometry of the corresponding butterfly test sample was optimized.

The aim of this work is to imitate mechanical experiment via numerical simulations in order to verify the stiffness of mechanical rigs and to ensure that reliable multiaxial loading is applied during the real experimental investigation. The topic of this thesis considers multiaxial grips that can impose different biaxial loading regimes. Hence, displacement fluctuations were measured on the butterfly sample with numerical calculations during tensile, shear and their combination when the sample is loaded with under 45°. The theoretical displacement distribution was studied on the idealized test sample with the appropriate boundary conditions. Consequently, the results obtained from idealized test case were compared with the results captured by the numerical experiment analysis. As a part of the finite element method application, various verification examples were performed in order to estimate the accuracy of the prescribed finite elements, boundary conditions, loading modes and the contact method.

Within this thesis, the geometry of the butterfly test sample was also optimized using the sensitivity field. Behavior of the sample material is described with elastoplastic constitutive law, taking into account the Armstrong-Frederick's kinematic hardening. The developed iterative algorithm is used to optimize two characteristic dimensions of the sample (radius R and angle α) that define two symmetric V notch. By increasing the displacement sensitivity field and the force sensitivity vector of the proposed test sample, optimal dimensions for the three stress plane states were determined.

• Keywords: Arcan prihvat; metoda konačnih elementa; Armstrong-Frederickov materijalni model; FEMU metoda; polje osjetljivosti
• Keywords (english): Arcane grips; finite element method; Armstrong-Frederick's material model; FEMU method; sensitivity field
• Language: croatian
• URN:NBN: urn:nbn:hr:235:468974
• 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: 2019-05-22 21:01:16