Projection and transfer operators in adaptive isogeometric analysis with hierarchical B-splines

2018 ◽  
Vol 334 ◽  
pp. 313-336 ◽  
Author(s):  
P. Hennig ◽  
M. Ambati ◽  
L. De Lorenzis ◽  
M. Kästner
Keyword(s):  
Isogeometric Analysis ◽  
B Splines ◽  
Transfer Operators

Extended isogeometric analysis using B++ splines for strong discontinuous problems

2021 ◽  
Vol 381 ◽  
pp. 113779
Author(s):  
Wenbin Hou ◽  
Kai Jiang ◽  
Xuefeng Zhu ◽  
Yuanxing Shen ◽  
Ping Hu
Keyword(s):  
Isogeometric Analysis ◽  
B Splines ◽  
Discontinuous Problems

B++ splines with applications to isogeometric analysis

2016 ◽  
Vol 311 ◽  
pp. 503-536 ◽  
Author(s):  
Xuefeng Zhu ◽  
Ping Hu ◽  
Zheng-Dong Ma
Keyword(s):  
Isogeometric Analysis ◽  
B Splines

scholarly journals Generalized straight and curved beam theories with isogeometric analyis

2017 ◽  
Author(s):  
Ιωάννης Τσιπτσής
Keyword(s):  
Isogeometric Analysis ◽  
Computer Aided Design ◽  
State Of The Art ◽  
Curved Beam ◽  
Analog Equation Method ◽  
B Splines ◽  
Aided Design ◽  
Analog Equation ◽  
Beam Theories ◽  
Element Method

Στη διατριβή αυτή διερευνάται και επιλύεται σειρά προβλημάτων μέσω της ανάπτυξης εξελιγμένων προσομοιωμάτων ευθύγραμμης και καμπύλης δοκού. Πιο συγκεκριμένα, αντιμετωπίζονται τα προβλήματα ανομοιόμορφης στρέψης, γενικευμένης στρέβλωσης λόγω διάτμησης και στρέψης (μέσω των οποίων μελετάται το φαινόμενο της διατμητικής υστέρησης), διαστρέβλωσης (παραμόρφωση των διατομών της δοκού στο επίπεδό τους) καθώς και το πρόβλημα της δυναμικής ανάλυσης ευθύγραμμων και καμπύλων δοκών. Η αντιμετώπιση των προβλημάτων αυτών βασίζεται στη γενικευμένη διατύπωση καινοτόμων θεωριών δοκού (Generalized Beam Theories - GBT), με τις οποίες το πεδίο μετατοπίσεων και οι συνιστώσες των τανυστών παραμόρφωσης και τάσης διατυπώνονται ως γραμμικοί συνδυασμοί γινομένων μονοδιάστατων και διδιάστατων συναρτήσεων.Η αναλυτική λύση των μονοδιάστατων και διδιάστατων προβλημάτων συνοριακών και αρχικών-συνοριακών τιμών που μορφώνονται εν γένει δεν είναι εφικτή. Ως εκ τούτου, τα προβλήματα αυτά επιλύονται αριθμητικά εφαρμόζοντας τη Μέθοδο Συνοριακών Στοιχείων (Boundary Element Method - BEM), τη Μέθοδο Αναλογικής Εξίσωσης (Analog Equation Method - AEM), η οποία αποτελεί εξέλιξη της BEM, καθώς και τη Μέθοδο Πεπερασμένων Στοιχείων (Finite Element Method - FEM). Όσον αφορά στην επίλυση μονοδιάστατων προβλημάτων, οι αριθμητικές μέθοδοι που χρησιμοποιoύνται (AEM και FEM) συνδυάζονται με εργαλεία της Ισογεωμετρικής Ανάλυσης (Isogeometric Analysis - IGA) ώστε να επιτευχθεί μία προσέγγιση με χαμηλότερο υπολογιστικό κόστος καθώς και πιο διαδραστική μεταξύ ανάλυσης και γεωμετρίας που θα επιτυγχάνει πιο αξιόπιστα αποτελέσματα περιορίζοντας το σφάλμα που πηγάζει από την προσέγγιση της γεωμετρίας. Συγκεκριμένα, οι παραμετρικές καμπύλες B-splines και NURBS (Non-Uniform Rational B-Splines) που έχουν υιοθετήσει τα λογισμικά πακέτα μοντελοποίησης με υπολογιστή (Computer-Aided Design - CAD) εφαρμόζονται στην παρούσα διατριβή. Με βάση τις αναπτυχθείσες αναλυτικές και αριθμητικές διαδικασίες συντάσσονται καινοτόμα προγράμματα ηλεκτρονικού υπολογιστή για την ανάλυση τρισδιάστατων ευθύγραμμων και καμπυλόγραμμων ραβδωτών φορέων. Κάθε κύριο κεφάλαιο της διατριβής αποτελείται από την εισαγωγή, τη διατύπωση του προβλήματος, την αριθμητική επίλυση, αντιπροσωπευτικά αριθμητικά παραδείγματα και τα συμπεράσματα. Στην εισαγωγή κάθε κύριου κεφαλαίου περιέχεται η βιβλιογραφική επισκόπηση του ερευνητικού έργου (State of the Art) του αντίστοιχου εξεταζόμενου προβλήματος και παρουσιάζονται τα πρωτότυπα σχετικά στοιχεία της εργασίας. Τέλος, στο τελικό κεφάλαιο παρουσιάζονται τα συμπεράσματα και προτάσεις για μελλοντική έρευνα.

Adaptive Numerical Modeling of Engineering Problems Using Hierarchical Fup Basis Functions and Control Volume IsoGeometric Analysis

2021 ◽  
Author(s):  
◽  
Grgo Kamber ◽  
Keyword(s):  
Isogeometric Analysis ◽  
Numerical Solutions ◽  
Control Volume ◽  
Spatial Scales ◽  
Basis Functions ◽  
Approximation Properties ◽  
Unified Framework ◽  
B Splines ◽  
Engineering Problems ◽  
Resolution Level

The main objective of this thesis is to utilize the powerful approximation properties of Fup basis functions for numerical solutions of engineering problems with highly localized steep gradients while controlling spurious numerical oscillations and describing different spatial scales. The concept of isogeometric analysis (IGA) is presented as a unified framework for multiscale representation of the geometry and solution. This fundamentally high-order approach enables the description of all fields as continuous and smooth functions by using a linear combination of spline basis functions. Classical IGA usually employs Galerkin or collocation approach using B-splines or NURBS as basis functions. However, in this thesis, a third concept in the form of control volume isogeometric analysis (CV-IGA) is used with Fup basis functions which represent infinitely smooth splines. Novel hierarchical Fup (HF) basis functions is constructed, enabling a local hp-refinement such that they can replace certain basis functions at one resolution level with new basis functions at the next resolution level that have a smaller length of the compact support (h-refinement), but also higher order (p-refinement). This hp-refinement property enables spectral convergence which is significant improvement in comparison to the hierarchical truncated B-splines which enable h-refinement and polynomial convergence. Thus, in domain zones with larger gradients, the algorithm uses smaller local spatial scales, while in other region, larger spatial scales are used, controlling the numerical error by the prescribed accuracy. The efficiency and accuracy of the adaptive algorithm is verified with some classic 1D and 2D benchmark test cases with application to the engineering problems with highly localized steep gradients and advection-dominated problems.

scholarly journals Multigrid solvers for immersed finite element methods and immersed isogeometric analysis

2019 ◽  
Vol 65 (3) ◽  
pp. 807-838 ◽  
Author(s):  
F. de Prenter ◽  
C. V. Verhoosel ◽  
E. H. van Brummelen ◽  
J. A. Evans ◽  
C. Messe ◽  
...  
Keyword(s):  
Finite Element ◽  
Finite Element Methods ◽  
Isogeometric Analysis ◽  
Convergence Rates ◽  
Computational Cost ◽  
Iterative Solvers ◽  
System Matrix ◽  
B Splines ◽  
Immersed Finite Element ◽  
Immersed Finite Element Methods

AbstractIll-conditioning of the system matrix is a well-known complication in immersed finite element methods and trimmed isogeometric analysis. Elements with small intersections with the physical domain yield problematic eigenvalues in the system matrix, which generally degrades efficiency and robustness of iterative solvers. In this contribution we investigate the spectral properties of immersed finite element systems treated by Schwarz-type methods, to establish the suitability of these as smoothers in a multigrid method. Based on this investigation we develop a geometric multigrid preconditioner for immersed finite element methods, which provides mesh-independent and cut-element-independent convergence rates. This preconditioning technique is applicable to higher-order discretizations, and enables solving large-scale immersed systems at a computational cost that scales linearly with the number of degrees of freedom. The performance of the preconditioner is demonstrated for conventional Lagrange basis functions and for isogeometric discretizations with both uniform B-splines and locally refined approximations based on truncated hierarchical B-splines.

scholarly journals A Non-Intrusive Stochastic Isogeometric Analysis of Functionally Graded Plates with Material Uncertainty

Axioms ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 92
Author(s):  
Shaima M. Dsouza ◽  
Tittu Mathew Varghese ◽  
P. R. Budarapu ◽  
S. Natarajan
Keyword(s):  
Zirconium Oxide ◽  
Isogeometric Analysis ◽  
Deformation Theory ◽  
Polynomial Chaos ◽  
Shear Deformation Theory ◽  
Functionally Graded ◽  
Functionally Graded Plates ◽  
B Splines ◽  
First Order ◽  
Graded Material

A non-intrusive approach coupled with non-uniform rational B-splines based isogeometric finite element method is proposed here. The developed methodology was employed to study the stochastic static bending and free vibration characteristics of functionally graded material plates with inhered material randomness. A first order shear deformation theory with an artificial shear correction factor was used for spatial discretization. The output randomness is represented by polynomial chaos expansion. The robustness and accuracy of the framework were demonstrated by comparing the results with Monte Carlo simulations. A systematic parametric study was carried out to bring out the sensitivity of the input randomness on the stochastic output response using Sobol’ indices. Functionally graded plates made up of Aluminium (Al) and Zirconium Oxide (ZrO2) were considered in all the numerical examples.

Generalized B-splines as a tool in isogeometric analysis

2011 ◽  
Vol 200 (5-8) ◽  
pp. 867-881 ◽  
Author(s):  
Carla Manni ◽  
Francesca Pelosi ◽  
M. Lucia Sampoli
Keyword(s):  
Isogeometric Analysis ◽  
B Splines

scholarly journals Analysis of cross-ply laminated plates using isogeometric analysis and unified formulation

2014 ◽  
Vol 1 (1) ◽  
Author(s):  
S. Natarajan ◽  
A.J.M. Ferreira ◽  
Hung Nguyen-Xuan
Keyword(s):  
Free Vibration ◽  
Isogeometric Analysis ◽  
Laminated Composite ◽  
Composite Plates ◽  
Laminated Plates ◽  
Smooth Functions ◽  
B Splines ◽  
Modification Factor ◽  
Carrera Unified Formulation ◽  
Plate Kinematics

AbstractIn this paper, we study the static bending and free vibration of cross-ply laminated composite plates using sinusoidal deformation theory. The plate kinematics is based on the recently proposed Carrera Unified Formulation (CUF), and the field variables are discretized with the non-uniform rational B-splines within the framework of isogeometric analysis (IGA). The proposed approach allows the construction of higher-order smooth functions with less computational effort.Moreover, within the framework of IGA, the geometry is represented exactly by the Non-Uniform Rational B-Splines (NURBS) and the isoparametric concept is used to define the field variables. On the other hand, the CUF allows for a systematic study of two dimensional plate formulations. The combination of the IGA with the CUF allows for a very accurate prediction of the field variables. The static bending and free vibration of thin and moderately thick laminated plates are studied. The present approach also suffers fromshear locking when lower order functions are employed and shear locking is suppressed by introducing a modification factor. The effectiveness of the formulation is demonstrated through numerical examples.

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