Finite Element Concepts and Bezier Extraction in Hierarchical Isogeometric Analysis

Author(s):  
Anh-Vu Vuong
2021 ◽  
Author(s):  
balakrishnan devarajan

Data transmission back and forth between finite element analysis (FEA) and computer-aided design (CAD) is a matter of huge concern today [2] and Isogeometric analysis [1] has been successful in merging these two fields in the recent past. The presentation will address isogeometric finite element approach (IGA) in combination with the first-order deformation plate theory (FSDT) for thermal buckling analysis of laminated composite plates. The IGA utilizes non-uniform rational B-spline (NURBS) as basis functions, resulting in both exact geometric representation and high order approximations [3] [4]. It enables to achieve easily the smoothness with arbitrary continuous order. The analyses have been performed using Bezier extraction and conventional IGA. In conventional isogeometric analysis the basis functions are not confined to one single element, but span a global domain whereas the Bézier extraction operator decomposes a set of linear combinations of Bernstein polynomials. The presentation will give a theoretical overview of B-splines, as well as NURBS, and also the concept of Bézier decomposition of these spline functions. The focus will then be on how the use of Bézier extraction eased the implementation into an already existing finite element code. This theoretical background will then be used to explain an isogeometric finite element analysis program. With the advent of More Electric Aircrafts [5], solving thermal structural problems [6] are of utmost importance in the aerospace industry. A static thermal structural validation problem will be presented for both constant and linear thermal temperature variation along the thickness. The presentation will then explain the procedures implemented for stress recovery and computing the geometric stiffness matrix. Numerical results of circular and elliptical plates will be provided to validate the effectiveness of the proposed method as compared to traditional FEA. The final section of the presentation proposes to detail the influences of length to thickness ratio, aspect ratio, boundary conditions, stacking sequence and material property on the critical buckling temperature. A special section would cover the idea of third order deformation theory for thicker plates and the effect of degree of NURBS basis on the results.


2016 ◽  
Vol 4 (4) ◽  
pp. 78-83
Author(s):  
Tan Nguyen ◽  
Thirapong Pipatpongsa ◽  
Takafumi Kitaoka ◽  
Hiroyasu Ohtsu

2019 ◽  
Vol 24 (12) ◽  
pp. 3753-3778 ◽  
Author(s):  
Amir Norouzzadeh ◽  
Reza Ansari ◽  
Mansour Darvizeh

In Part I of this study, a variational formulation was presented for the large elastic deformation problem of micromorphic shells. Using the novel matrix-vector format presented for the kinematic model, constitutive relations, and energy functions, an isogeometric analysis (IGA)-based solution strategy is developed, which appropriately estimates the macro- and micro-deformation field components. Due to the capability of constructing exact geometries and the powerful mesh refinement tools, IGA can be successfully applied to solve the equilibrium equations with dominant nonlinear terms. It is known that different types of locking phenomena take place in the conventional finite element analysis of thin shells based on low-order elements. Non-standard finite element models with mixed interpolation schemes and additional degrees of freedom (DOFs) or the ones used the high-order Lagrangian shell elements which require high computational costs, are the available solutions to tackle locking issues. The present 16-DOFs IGA is found to be efficient because of possessing a good rate of convergence and providing locking-free stable responses for micromorphic shells. Such a conclusion is found from several comparative studies with available data in the well-known macro-scale benchmark problems based on the classical elasticity as well as the corresponding numerical examples studied in nano-scale beam-, plate-, cylindrical shell- and spherical shell-type structures on the basis of the micromorphic continuum theory.


2019 ◽  
Vol 65 (3) ◽  
pp. 807-838 ◽  
Author(s):  
F. de Prenter ◽  
C. V. Verhoosel ◽  
E. H. van Brummelen ◽  
J. A. Evans ◽  
C. Messe ◽  
...  

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.


2020 ◽  
Vol 37 (7) ◽  
pp. 2439-2466
Author(s):  
Mateus Rauen ◽  
Roberto Dalledone Machado ◽  
Marcos Arndt

Purpose This study aims to present a new hybrid formulation based on non-uniform rational b-splines functions and enrichment strategies applied to free and forced vibration of straight bars and trusses. Design/methodology/approach Based on the idea of enrichment from generalized finite element method (GFEM)/extended finite element method (XFEM), an extended isogeometric formulation (partition of unity isogeometric analysis [PUIGA]) is conceived. By numerical examples the methods are tested and compared with isogeometric analysis, finite element method and GFEM in terms of convergence, error spectrum, conditioning and adaptivity capacity. Findings The results show a high convergence rate and accuracy for PUIGA and the advantage of input enrichment functions and material parameters on parametric space. Originality/value The enrichment strategies demonstrated considerable improvements in numerical solutions. The applications of computer-aided design mapped enrichments applied to structural dynamics are not known in the literature.


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