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Velike deformacije prostorskih kompozitnih nosilcev z nelinearnim zakonom stika med sloji
ID Lolić, Damjan (Author), ID Brojan, Miha (Mentor) More about this mentor... This link opens in a new window

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Abstract
V doktorskem delu je predstavljena formulacija končnih elementov za analizo prostorskih in ravninskih slojevitih nosilcev. Zasnovani končni elementi temeljijo na Reissnerjevi geometrijsko točni teoriji, s katero modeliramo posamezne lamele. S kvaternionsko parametrizacijo rotacij se izognemo singularnim točkam, s predpostavko o konstantnih deformacijah vzdolž posameznega končnega elementa potrebi po uporabi interpolacije, z določitvijo deformacijskih veličin za primarne spremenljivke pa efektu strižnega blokiranja. Robusten, prilagodljiv in matematično konsistenten računski model vključuje tudi porazdeljen sistem nelinearnih vzmeti za opis povezave med plastmi. Ker lahko vmesne zveze opišemo s poljubno funkcijo togosti vzmeti, je model sposoben upoštevati različne fizikalne pojave, kot so trenje med plastmi, stiki, kohezivne sile, itn. Natančni preizkusi na debelem polnem nosilcu, debelem delno delaminiranem nosilcu, strižnem testu prekrivnega spoja tankih nosilcev in kompozitu filma in substrata kažejo na učinkovitost in vsestranskost predlaganega numeričnega postopka. Primerjava naših rezultatov z rezultati iz literature in komercialnih programov za analizo končnih elementov kaže prednosti predlagane formulacije, zlasti kadar je struktura podvržena večjim strižnim deformacijam. To izhaja iz dejstva, da naš model zagotavlja matematično konsistenten postopek iterativnega posodabljanja vseh količin, ki opisujejo nosilec.

Language:Slovenian
Keywords:nelinearna teorija nosilcev, kompozitni nosilec, kohezivni model, delaminacija, preizkušanje, numerični primeri
Work type:Doctoral dissertation
Typology:2.08 - Doctoral Dissertation
Organization:FS - Faculty of Mechanical Engineering
Place of publishing:Ljubljana
Publisher:[D. Lolić]
Year:2020
Number of pages:XXVIII, 134 str., [2] f. pril.
PID:20.500.12556/RUL-117205 This link opens in a new window
UDC:624.016:539.37:519.61(043.3)
COBISS.SI-ID:21624323 This link opens in a new window
Publication date in RUL:02.07.2020
Views:719
Downloads:192
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Secondary language

Language:English
Title:Finite deformations of three-dimensional composite beams with non-linear contact between layers
Abstract:
The doctoral thesis presents the finite element formulation for the analysis of spatial and planar layered beams. The designed finite elements are based on Reissner geometrically exact theory to model the individual layers. Through quaternion parametrization of the rotations, we avoid singularities, by assuming constant deformations along the length of a finite element, the need for interpolation, and the choice of deformation quantities as primary unknowns, the effect of shear blocking. The robust, adaptive, mathematically consistent and singularity-free computational model also includes a distributed system of nonlinear springs to describe the connection between the layers. Since the interfaces can be described by any function of spring stiffness, the model is able to consider various physical phenomena such as friction between layers, contacts, cohesion forces, etc. Thorough tests on thick solid beam, thick partially delaminated beam, overlap shear test and film-substrate composite demonstrate the efficiency and versatility of the proposed numerical method. The comparison of our results with those of the literature and commercial finite element analysis software shows the advantages of the proposed formulation, especially when the structure is subject to large shear deformations. This is due to the fact that our model provides a mathematically consistent method for iterative updating of all variables describing the beam.

Keywords:nonlinear beam theory, composite beams, cohesive model, delamination, experiments, numerical examples

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