Modificirano hidraulično udubljivanje na sferi

doctoral thesis

• Title (english): Modified hydraulic bulging on the sphere
• Author: Marko Škunca
• Mentor: Miljenko Math (mentor)
• Committee member: Mladen Šercer (predsjednik povjerenstva)
• Committee member: Miljenko Math (član povjerenstva)
• Committee member: Zdravko Virag (član povjerenstva)
• Committee member: Janoš Kodvanj (član povjerenstva)
• Committee member: Branko Grizelj (član povjerenstva)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2009-09-03, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mechanical Engineering
• Universal decimal classification (UDC): 53 - Physics ; 620 - Materials testing. Power stations. Economics of energy ; 621 - Mechanical engineering. Nuclear technology. Machinery

Abstract

U radu je predložena nova metoda snimanja krivulje plastičnog tečenja pod nazivom modificirano hidraulično udubljivanje na sferi. Metoda je izvedena iz postupka hidrauličnog udubljivanja. Na napravi izrađenoj za oba navedena postupka, snimljene su krivulje plastičnog tečenja aluminijskog lima. Kako bi se mogle usporediti dvije metode, izvedeni su za to prikladni izrazi; za kinematiku i pripadajuća naprezanja. U oba slučaja korištena je pretpostavka membranskih naprezanja u limu i izvedeni su uvjeti plastičnog tečenja, neophodni za snimanje krivulje plastičnog tečenja. Usporedbom korištenih metoda ukazano je na prednosti modificirane metode. Uz analitički pristup problemu te provedene eksperimente, rezultati su modelirani i metodom konačnih elemenata. Modificirani postupak se pokazao primjerenim i za provjeru numeričkog modela, jer omogućava izravno mjerenje naprezanja u materijalu što nije moguće kod klasičnog hidrauličnog udubljivanja.

Abstract (english)

In the paper, an original method of the stress-strain diagram acquisition named modified hydraulic bulging on the sphere is introduced. The method has been derived from the hydraulic bulging test. True stress-strain curves were established for aluminium sheet on the experimental apparatus designed for both methods. For the purpose of comparing the two research methods, appropriate expressions, i.e. expressions for kinematics and particular equivalent stresses, were derived. In both cases, the assumption of the membrane stress state was used and the flow rule was determined, which was necessary for establishing the true stress-strain curve. The comparison between the used methods has shown the advantages of the modified method. Besides the analytical approach and the conducted experiments, the results were modelled using the finite element method. The modified method has proved to be adequate for checking the numerical model, because it enables direct experimental measurement of the true stresses in the material, which cannot be done when the classical hydraulic bulging test is used.

• Keywords: hidraulično udubljivanje; krivulja plastičnog tečenja; modificirano hidraulično udubljivanje; oblikovanje lima; ravninski napregnuto stanje; membranska naprezanja
• Keywords (english): hydraulic bulging; true stress-strain diagram; modified hydraulic bulginig; sheet metal forming; plane stress; membrane stress
• Language: croatian
• URN:NBN: urn:nbn:hr:235:832417
• 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: 2020-12-30 12:37:00