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Title:RAČUNALNIŠKO MODELIRANJE CELIČNIH GRADIV NEUREJENE STRUKTURE
Authors:ID Borovinšek, Matej (Author)
ID Ren, Zoran (Mentor) More about this mentor... New window
Files:.pdf DR_Borovinsek_Matej_2009.pdf (12,17 MB)
MD5: AF9588044D372F55E1599653D55D81CF
PID: 20.500.12556/dkum/e4d568f6-325f-4655-aabf-122c5dca20eb
 
Language:Slovenian
Work type:Dissertation
Organization:FS - Faculty of Mechanical Engineering
Abstract:Obstoječi konstitutivni modeli celičnih gradiv, ki so danes vključeni v različnih sistemih za inženirske računalniške simulacije, ne upoštevajo vpliva geometrijske neurejenosti na spremembo makroskopskih lastnosti celičnega gradiva ob istočasnem upoštevanju različnih deformacijskih hitrosti oziroma ob upoštevanju dinamičnih obremenitev. Zaradi tega je bil razvit nov rešetkasti model neurejenih odprto-celičnih gradiv, ki omogoča upoštevanje vpliva neurejenosti in različnih deformacijskih hitrosti na lastnosti odprto-celičnih gradiv pri velikih deformacijah. Zaradi velikega vpliva neurejenosti strukture odprto-celičnih gradiv na njihove lastnosti in pomanjkanja podatkov o geometrijski strukturi odprto-celičnih gradiv, je bila za namen modeliranja neurejenih odprto-celičnih gradiv razvita tehnika avtomatizirane 3D rekonstrukcije njihovih geometrijskih značilnosti na osnovi tomografskih posnetkov. Analize rekonstruiranih modelov so pokazale, da imajo realne trdne pene bogato in raznoliko porazdelitev osnovnih geometrijskih značilnosti in se njihove geometrijske lastnosti bistveno razlikujejo od urejenih struktur s tetrakaidekaedrično oziroma kubično osnovno celico, ki so služile kot osnova številnim raziskavam v preteklosti. Na podlagi statistično obdelanih podatkov o strukturi realnih aluminijastih pen je bila narejena primerjava s statistično obdelanimi podatki dveh računalniških modelov neurejenih odprto-celičnih gradiv, ki sta osnovana na ravnotežnih Kelvinovih in Weaire-Phelanovih celicah. Dokazano je, da modeli osnovani na Weaire-Phelanovi delitvi prostora bolje opisujejo strukturo realnih pen. Pokazalo se je tudi veliko odstopanje realnih pen od popolnoma naključnih računalniških modelov, kar potrjuje predpostavko, da trdne pene vendarle niso povsem naključne strukture, ampak na njihov nastanek močno vpliva fizikalno ozadje načina penjenja med proizvodnim postopkom. S primerjalno analizo je bila določena tudi ustrezna stopnja neurejenosti novo razvitega modela odprto-celičnih struktur, pri kateri lastnosti računalniško generiranih modelov najbolj sovpadajo z lastnostmi podobnih realnih aluminijastih pen. Za namen validacije uporabe razvitih Weaire-Phelanovih modelov v računalniških simulacijah so bili opravljeni eksperimentalni kvazi-statični in dinamični (udarni) tlačni enoosni eksperimentalni preizkusi vzorcev aluminijastih odprto-celičnih pen, kjer je bil ugotovljen pričakovano velik vpliv relativne gostote na togost celičnih gradiv. Primerjava rezultatov eksperimentalnih preizkusov in računalniških simulacij je pokazala dobro ujemanje makroskopskih mehanskih lastnosti, kar dokazuje primernost uporabe neurejenih rešetkastih modelov odprto-celičnih aluminijastih pen na osnovi Weaire-Phelanovih celic v računalniških simulacijah obnašanja teh gradiv pri različnih hitrostih tlačnega obremenjevanja.
Keywords:odprto-celična gradiva, računalniška tomografija, geometrijska rekonstrukcija, mehanske lastnosti, eksperimentalni preizkusi, računalniške simulacije, udarne obremenitve
Place of publishing:Maribor
Publisher:M. Borovinšek]
Year of publishing:2009
PID:20.500.12556/DKUM-10617 New window
UDC:621
COBISS.SI-ID:246160384 New window
NUK URN:URN:SI:UM:DK:G3KZGYOM
Publication date in DKUM:02.06.2009
Views:4555
Downloads:458
Metadata:XML DC-XML DC-RDF
Categories:KTFMB - FS
:
BOROVINŠEK, Matej, 2009, RAČUNALNIŠKO MODELIRANJE CELIČNIH GRADIV NEUREJENE STRUKTURE [online]. Doctoral dissertation. Maribor : M. Borovinšek. [Accessed 1 April 2025]. Retrieved from: https://dk.um.si/IzpisGradiva.php?lang=eng&id=10617
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Secondary language

Language:English
Title:COMPUTATIONAL MODELING OF IRREGULAR CELLULAR STRUCTURES
Abstract:Constitutive models of cellular materials integrated into existing computer simulation software do not account for the effects of cell shape irregularity of such materials on their macroscopic mechanical properties in combination with different strain rates under impact loading conditions. Thus a new lattice computer model of irregular open-cell materials was developed which accounts for irregularity and strain rate effects on the mechanical properties of open-cell materials at large deformations. Due to large effect of the cell shape irregularity on mechanical properties of open-cell materials and lack of data on geometrical structure of open-cell materials, an automated 3D geometry reconstruction technique based on analysis of tomographic pictures was developed for the purpose of more realistic modelling of irregular open-cell materials. Analyses of the reconstructed models showed that real open-cell structures have rich and diverse distribution of basic geometrical properties and that their geometrical properties significantly differ from the regular structures with cubic or tetrakaidekahedral basic cells, which where used in many research studies in the past. Geometrical data of aluminium foam samples was statistically analysed and compared with similarly statistically analysed geometrical data of two irregular open-cell computer models, which were based on equilibrium Kelvin cells and Weaire-Phelan cells. It was proven that models based on Weaire-Phelan cells describe the structure of real foams better in comparison with models based on Kelvin cells. Also, a significant discrepancy between the real foam geometry and the geometry of completely random generated computer models was determined, which confirms the assumption that the structure of a solid real foam is not random and that its formation is strongly influenced by the physical background of the foaming type during the production process. Comparative analysis was used to determine the irregularity parameter of newly developed representative lattice model of open-cell materials, at which the properties of computer generated models concur best with properties of similar real aluminium foams. Quasi-static and dynamic (impact) experimental uni-axial compression tests of aluminium open-cell foam samples were carried out to validate the developed Weaire-Phelan computer models. The results showed expected significant influence of relative density on open-cell foam load carrying capacity. Comparison of experimental results and results of computer simulations showed a good agreement of macroscopic mechanical properties, which confirms that irregular lattice modelling of open-cell aluminium foams based on Weaire-Phelan cell model is appropriate for simulating the behaviour of such materials under different compressive loading rates.
Keywords:open-cell cellular materials, computer tomography, geometry reconstruction, mechanical properties, experimental testing, computer simulations, impact loading


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