2023.
Doctoral thesis
University of Rijeka, UNIVERSITY OF RIJEKA - FACULTY OF ENGINEERING
https://urn.nsk.hr/urn:nbn:hr:190:739429
U doktorskom je radu prikazan numerički pristup rješavanju problema nelinearne stabilnosti grednih nosača i konstrukcija izrađenih od FG (Fuctionally graded) materijala u uvjetima promjenjive temperature. Geometrijski nelinearni algoritam razvijen je uporabom 1D numeričkog modela koji se temelji na primjeni prostornog grednog konačnog elementa. Uključeni su efekti velikih prostornih pomaka i prostornih rotacija. Deformacije su smatrane malima te se za njihovo definiranje rabi Green-Lagrangeov tenzor deformacije. Konačnoelementni model temelji se na Euler-Bernoullijevoj teoriji savijanja i Vlasovljevoj teoriji uvijanja. Kod nelinearne analize implementirana je UL (updated Lagrangian) inkrementalna formulacija uporabom principa virtualnih radova. Predloženi gredni model omogućuje provođenje analize izvijanja za slučajeve uniforme, linearne i nelinearne temperaturne distribucije po debljini stijenke poprečnoga presjeka nosača, kao i pri linearnoj promjeni temperature uzduž nosača. Analiza uključuje i temperaturnu ovisnost mehaničkih svojstava materijala. Temeljem prethodno izrečenog izrađen je računalni program THINWALL FG. Problem je rješavan u dvije faze. U prvoj fazi određuje se odziv konstrukcije za zadano mehaničko opterećenje. U drugoj fazi, dok se mehaničko opterećenje drži konstantnim, nanosi se temperaturno opterećenje te se određuje temperatura kod koje dolazi do toplinskoga izvijanja. Točnost i pouzdanost numeričkog algoritma testirane su usporedbom s rezultatima dostupnima iz literature te onima dobivenim primjenom 2D i/ili 3D konačnoelementnih modela iz etabliranih programskih paketa.
tankostjeni presjeci MKE toplinsko izvijanje kompoziti FGM stabilnost
Authors Kvaternik Simonetti, Sandra (Author)
Advisors Lanc, Domagoj (Thesis advisor) ; Turkalj, Goran (Thesis co-advisor)
Committee members Čanađija, Marko (Committee chair) ; Jelenić, Gordan (Committee member) ; Tonković, Zdenko (Committee member)
Alternative titles
(English) Numerical model for thermal buckling analysis of FG composite beam structures : doctoral dissertation
Alternative abstracts
(English) In this doctoral dissertation, a numerical approach for solving the problem of nonlinear stability of beam structures made of FG (functionally graded) materials under conditions of variable temperature is developed. The geometric nonlinear algorithm was developed using a 1D numerical model based on the application of a spatial beam finite element. The effects of large spatial displacements and spatial rotations are included. Deformations are considered small and the Green-Lagrange deformation tensor is used to define them. The finite element model is based on the Euler-Bernoulli beam theory for bending and the Vlasov theory for torsion. In the nonlinear analysis, the UL (updated Lagrangian) incremental formulation was implemented using the principle of virtual works. The proposed beam model enables the implementation of buckling analysis for cases of uniform, linear and nonlinear temperature distribution through the thickness of the crosssectional walls as well as linear temperature distribution along the beam length will be conducted. The analysis also includes the temperature dependence of the mechanical properties of the material. The computer program THINWALL FG was created on the basis of the above. The problem was solved in two stages. In the first phase, the response of the structure to a given mechanical load is determined. In the second phase, while the mechanical load is kept constant, a temperature load is applied and the temperature at which thermal buckling occurs is determined. The accuracy and reliability of the numerical algorithm was tested by comparison with the results available from the literature and those obtained using 2D and/or 3D finite element models from established software packages.
Alternative keywords
thin-walled
FEM
thermal buckling
composites
FG materials
stability
Degree grantor
University of Rijeka, UNIVERSITY OF RIJEKA - FACULTY OF ENGINEERING
Study program
Poslijediplomski doktorski studij iz područja Tehničkih znanosti, polja Strojarstva, Brodogradnje i Temeljnih tehničkih znanosti i Interdisciplinarnih tehničkih znanosti; university; postgraduate
Areas, fields, branches
Technical Sciences / Mechanical Engineering
Dates
Defence date: September 8, 2023
Languages
Croatian
Version
defended version
Object creation date
October 17, 2023
Identifiers
