Model plitkoga gravurnoga kovanja temeljen na veličini kristalnoga zrna

doctoral thesis

• Title (english): Closed die coining model based on grain size
• Author: Petar Piljek
• Mentor: Zdenka Keran (mentor)
• Committee member: Damir Ciglar (predsjednik povjerenstva)
• Committee member: Zdenka Keran (član povjerenstva)
• Committee member: Branko Grizelj (član povjerenstva)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2017-05-26, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mechanical Engineering; Production Mechanical Engineering
• Universal decimal classification (UDC): 621 - Mechanical engineering. Nuclear technology. Machinery

Abstract

Poznato je da se proces plitkog gravurnog kovanja može uvrstiti u skupinu procesa mikro oblikovanja deformiranjem. Kod takvih procesa mikrostruktura i red veličine geometrije gravure imaju značajan utjecaj na mehanizam deformiranja te se mikro procesi fundamentalno razlikuju od klasičnih procesa oblikovanja. Zbog toga je potrebno odrediti utjecaj efekta veličine na silu kovanja i pomak alata kod procesa plitkog gravurnog kovanja. U tu svrhu istražen je utjecaj veličine kristalnog zrna materijala na elastični povrat materijala nakon prestanka djelovanja sile oblikovanja, popunjavanje gravure i silu kovanja otkovaka materijala. Materijal sirovaca (rondela) je 99,5% aluminij i koristi se gravura relativno složene geometrije. Predloženi model plitkog gravurnog kovanja uzima u obzir utjecaj efekata veličine na naprezanje plastičnog tečenja preko geometrije gravure te daje procjenu konačne sile kovanja i pripadajućeg pomaka alata. Time je omogućen kontroliran utjecaj veličine kristalnog zrna na silu kovanja i pomak alata, kao i pouzdana predikacija konačne sile kovanja i pomaka alata kod kojeg se postiže potpuno popunjavanje gravurne šupljine.

Abstract (english)

It is known that the coining process can be categorised as a micro forming process. In micro forming processes, the microstructure of the material and dimension scale of the forged geometry can have a substantial influence on the mechanism of material deformation. That is the essential difference between macro and micro forming processes. Influence of the grain size on the elastic springback of the material, filling of the die and the forging force in process of coining will be investigated in this study. The material of the billet is 99.5% aluminium and the die geometry is relatively complex. The presented model takes into account the influence of size effect on the material flow curve through engraving geometry and estimates the final forging force and corresponding associated displacement of the tool. This enables a controlled influence of the grain size on forming force and tool displacement and also a reliable prediction of final forging force and related tool displacement associated with a completely filled engraving cavity.

• Keywords: plitko gravurno kovanje; mikro oblikovanje; veličina kristalnog zrna; efekti veličine; sila kovanja
• Keywords (english): coining; micro forming; grain size; size effects; forming force
• Language: croatian
• URN:NBN: urn:nbn:hr:235:180642
• 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: 2020-04-09 22:39:28