Stabilnost superelastičnih tankostenskih lupin iz materiala z oblikovnim spominom za uporabo v elastokalorični tehnologiji

doktorsko delo

Luka Porenta (Author), Miha Brojan (Mentor), Jaka Tušek (Co-mentor)

Abstract

V zadnjih letih se je elastokaloriˇcna tehnologija hlajenja (ETH), ki temelji na elastokaloriˇcnem uˇcinku materialov z oblikovnim spominom (MOS), uveljavila kot ena najbolj obetavnih alternativ parno-kompresijske tehnologije hlajenja. Glavna omejitev ETH je kratka ˇzivljenjska doba, ki se lahko bistveno podaljˇsa, ˇce MOS namesto nateznemu izpostavimo tlaˇcnemu obremenjevanju. Enega najveˇcjih izzivov pri razvoju tlaˇcno obremenjenih elastokaloriˇcnih naprav predstavlja iskanje kompromisa med sposobnostjo hitrega prenosa toplote, ki zahteva tankostenske elemente in strukturno (ne)stabilnostjo, na katero so takˇsni elementi obˇcutljivi. Najboljˇsi kompromis zaenkrat izkazujejo tankostenske cevi z okroglim prerezom, zato so bile osrednji predmet obravnave tega dela. Eksperimentalno smo doloˇcili stabilne dolˇzine cevi razliˇcnih preˇcnih prerezov ter izdelali dva fazna diagrama uklonskih oblik. Ugotovili smo, da temperaturne spremembe zaradi elastokaloriˇcnega uˇcinka zmanjˇsajo stabilnost. Z uporabo vmesnih podpor smo izboljˇsali stabilnost daljˇsih cevi. Kot prvi smo razvili 3D lupinski konˇcni element, ki temelji na teoriji velikih deformacij in vkljuˇcuje konstitutivne enaˇcbe za MOS. Izdelali smo numeriˇcni model za napovedovanje nestabilnosti cevi iz MOS, ki je bil verificiran s pomoˇcjo eksperimentalnih rezultatov. Uporaba razvitega lupinskega elementa omogoˇca doloˇcitev odziva poljubne tankostenske strukture iz MOS, zato je njegova aplikativnost ˇsiroka in se lahko uporabi tudi za naˇcrtovanje elementov na podroˇcju medicine, avtomobilske ali letalske industrije itd.

Keywords

strukturna stabilnost;uklon;materiali z oblikovnim spominom;lupine;superelastičnost;elastokalorični učinek;

Data

Language:	Slovenian
Year of publishing:	2022
Typology:	2.08 - Doctoral Dissertation
Organization:	UL FS - Faculty of Mechanical Engineering
Publisher:	[L. Porenta]
UDC:	621.56/.59+624.074.43(043.3)
COBISS:	131257347
Views:	303
Downloads:	130
Average score:	0 (0 votes)
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Other data

Secondary language:	English
Secondary title:	Stability of superelastic thin-walled shape memory alloy shells for apllications in elastocaloric technology
Secondary abstract:	In recent years, elastocaloric cooling technology (ECT), based on the elastocaloric effect of shape memory materials (SMA), has emerged as one of the most promising alternatives to vapor compression cooling technology. The main limitation of ECT is its short fatigue life, which can be significantly improved if compressive loading is applied instead of tensile. One of the major challenges in the development of compressionloaded elastocaloric devices is to find a compromise between the capability of rapid heat transfer, which requires thin-walled structures, and the structural (in)stability to which such structures are prone. Thin-walled tubes with round cross-sections have shown the best compromise so far and have therefore been the main focus of this work. We have experimentally determined stable tube lengths of different cross-sections and defined two phase diagrams of buckling mode shapes. We found that temperature changes reduce the stability due to the elastocaloric effect. It has been shown that the use of intermediate supports increases the stability of long tubes. For the first time, a 3D shell finite element based on large deformation theory with incorporated SMA constitutive equations has been developed. A numerical model for predicting of instabilities of SMA tubes was developed and verified by the experimental results. The developed shell element can be used to model the response of arbitrary thinwalled SMA structures. Its applicability is therefore broader and can be used to design SMA components also in various branches of industry, such as medical, automotive, aerospace, etc.
Secondary keywords:	structural stability;buckling;shape memory materials;shells;superelasticity;Materiali z oblikovnim spominom;Disertacije;
Type (COBISS):	Doctoral dissertation
Study programme:	0
Embargo end date (OpenAIRE):	1970-01-01
Thesis comment:	Univ. v Ljubljani, Fak. za strojništvo
Pages:	XXXIV, 156 str.
ID:	16830734