Identification of the mechanical properties of nodular graphite cast iron via multiaxial tests

doctoral thesis

• Title (croatian): Identifikacija mehaničkih svojstava nodularnog lijeva kod višeosnih opterećenja
• Author: Zvonimir Tomičević
• Mentor: Janoš Kodvanj (mentor)
• Mentor: François Hild https://orcid.org/0000-0001-5553-0066 (komentor)
• Committee member: Zdenko Tonković (predsjednik povjerenstva)
• Committee member: Janoš Kodvanj (član povjerenstva)
• Committee member: François Hild https://orcid.org/0000-0001-5553-0066 (član povjerenstva)
• Committee member: Michel Grediac (član povjerenstva); strani drzavljanin: Nije dostupno
• Committee member: Ante Bakić (član povjerenstva)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2015-12-13, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mechanical Engineering; General Mechanical Engineering (Construction)
• Universal decimal classification (UDC): 620 - Materials testing. Power stations. Economics of energy ; 53 - Physics

Abstract

The development of new engineering elements has increased the application of new technologies and materials. This trend has stimulated in the last few decades scientists to describe the material behaviour with more reliable and complex constitutive laws. The latter ones require advanced methods for the identification and validation of material parameters. Digital Image Correlation (DIC) as a full-field measurement technique coupled with Finite Element analyses is suited for identification and validation purposes. Within this thesis, identification and validation of the nonlinear behaviour of nodular graphite cast iron is carried out. Finite Element Model Updating procedures will be used as the identification tool.rnRegularised DIC code was developed and its application found compromise between standard displacement resolution and spatial resolution. As a result of regularised DIC is decrease of uncertainty of the measured displacement field in comparison with existing DIC algorithms.The challenge of analysing poor texture of nodular graphite cast iron where conventional DIC approaches fail to capture accurately the displacement is successfully bypassed with R-DIC.The overall contribution of this thesis is related to a better understanding of the nonlinear mechanical behavior of the investigated nodular graphite cast iron. The main part of this research hase been implementation of an generic algorithms for identification of material parameters. Thus, its use is also applicable on other materials that may include various load regimes and constitutive laws. Further investigation is proposed which should yield with more reliable description of the material behavior.

Abstract (croatian)

Razvojem novih konstrukcijskih elemenata sve je veća potreba za primjenom novih tehnologija i materijala. Takav trend potaknuo je u posljednjih nekoliko desetljeća znanstenike da ponašanje materijala opisuju pouzdanijim i složenijim materijalnim modelima. Primjena kompleksnih konstitutivnih modela zahtijeva korištenje naprednih metoda za identifikaciju i validaciju parametara materijala. Metoda korelacije digitalne slike (DIC) kao metoda mjerenja cijeloga polja pomaka povezan s metodom konačnih elemenata prikladan je za identifikacijske i validacijske svrhe. Istraživanje provedeno u okviru ovoga doktorskoga rada je identifikacija i validacija nelinearnoga ponašanja nodularnoga lijeva. Identifikacijska procedura ažuriranja modela konačnih elemenata (FEMU) korištena je kao alat za identifikaciju. Za uspješnu provedbu predloženoga istraživanja razvijen je regulariziran DIC. Primjenom regularizacije pronađen je kompromis između standardne rezolucije pomaka te prostorne rezolucije te je smanjena mjerna nesigurnost polja pomaka u usporedbi s postojećim DIC algoritmima. Razvijeni algoritam uspješno je analizirao siromašnu teksturu nodularnoga lijeva, što nije bilo moguće standardnim korelacijskim pristupima. Cjelokupni doprinos doktorskoga rada odnosi se na bolje razumijevanje nelinearnoga mehaničkoga ponašanja promatranoga nodularnoga lijeva. U okviru ovoga istraživanja razvijeni su generički algoritmi za identifikaciju parametara materijala te je njihova primjena moguća i na drugim materijalima koji mogu uključivati raznovrsne režime opterećenja

• Keywords: nonlinear material behaviour; full-field measurement; identification; nodular graphite cast iron; multiaxial loading; crack networks; regularization; tomography
• Keywords (croatian): nelinearno mehaničko ponašanje materijala; mjerenje cijelog polja pomaka; identifikacija; nodularni lijev; višeosno opterećenje; mreža mikropukotina; regularizacija; tomografija
• Language: english
• URN:NBN: urn:nbn:hr:235:459809
• Study programme: Title: Mechanical Engineering and Naval Architecture; Study programme type: university; Study level: postgraduate; Academic / professional title: doktor/doktorica znanosti, područje tehničkih znanosti (doktor/doktorica znanosti, područje tehničkih znanosti)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2020-04-24 07:58:43