scholarly journals Preconditioning the Quad Dominant Mesh Generator for Ship Structural Analysis

Algorithms ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 2
Author(s):  
Luka Grubišić ◽  
Domagoj Lacmanović ◽  
Josip Tambača
Keyword(s):  
Heuristic Method ◽  
Offshore Structures ◽  
Element Analysis ◽  
Mesh Generator ◽  
Quality Requirements ◽  
Shell Elements ◽  
Low Degree ◽  
The Finite Element Analysis ◽  
Fully Automatic ◽  
Automatic Mesh

This paper presents an algorithm for the fully automatic mesh generation for the finite element analysis of ships and offshore structures. The quality requirements on the mesh generator are imposed by the acceptance criteria of the classification societies as well as the need to avoid shear locking when using low degree shell elements. The meshing algorithm will be generating quadrilateral dominated meshes (consisting of quads and triangles) and the mesh quality requirements mandate that quadrilaterals with internal angles close to 90° are to be preferred. The geometry is described by a dictionary containing points, rods, surfaces, and openings. The first part of the proposed method consists of an algorithm to automatically clean the geometry. The corrected geometry is then meshed by the frontal Delaunay mesh generator as implemented in the gmsh package. We present a heuristic method to precondition the cross field of the fronatal quadrilateral mesher. In addition, the influence of the order in which the plates are meshed will be explored as a preconditioning step.

scholarly journals Preconditioning the Quad Dominant Mesh Generator for Ship Structural Analysis

2021 ◽  
Author(s):  
Luka Grubisic ◽  
Domagoj Lacmanović ◽  
Josip Tambača
Keyword(s):  
Heuristic Method ◽  
Offshore Structures ◽  
Element Analysis ◽  
Mesh Generator ◽  
Quality Requirements ◽  
Shell Elements ◽  
Low Degree ◽  
The Finite Element Analysis ◽  
Fully Automatic ◽  
Automatic Mesh

This paper presents an algorithm for the fully automatic mesh generation for the finite element analysis of ships and offshore structures. The quality requirements on the mesh generator are imposed by the acceptance criteria of the classification societies as well as the need to avoid shear locking when using low degree shell elements. The meshing algorithm will be generating quadrilateral dominated meshes (consisting of quads and triangles) and the mesh quality requirements mandate that quadrilaterals with internal angles close to $90\degree$ are to be preferred. The geometry is described by a dictionary containing points, rods, surfaces and openings. The first part of the proposed method consist of an algorithm to automatically clean the geometry. The corrected geometry is then meshed by the frontal Delaunay mesh generator as implemented in the gmsh package. We present a heuristic method to precondition the cross field of the frontal quadrilateral mesher. Also the influence of the order in which the plates are meshed will be explored as a preconditioning step.

Some new results and current challenges in the finite element analysis of shells

Acta Numerica ◽  
2001 ◽  
Vol 10 ◽  
pp. 215-250 ◽  
Author(s):  
Dominique Chapelle
Keyword(s):  
Finite Element ◽  
Shell Theory ◽  
Shell Structures ◽  
Engineering Practice ◽  
Element Analysis ◽  
Shell Elements ◽  
Shell Models ◽  
The Finite Element Analysis ◽  
Shell Finite Element ◽  
Mathematical Analyses

This article, a companion to the article by Philippe G. Ciarlet on the mathematical modelling of shells also in this issue of Acta Numerica, focuses on numerical issues raised by the analysis of shells.Finite element procedures are widely used in engineering practice to analyse the behaviour of shell structures. However, the concept of ‘shell finite element’ is still somewhat fuzzy, as it may correspond to very different ideas and techniques in various actual implementations. In particular, a significant distinction can be made between shell elements that are obtained via the discretization of shell models, and shell elements – such as the general shell elements – derived from 3D formulations using some kinematic assumptions, without the use of any shell theory. Our first objective in this paper is to give a unified perspective of these two families of shell elements. This is expected to be very useful as it paves the way for further thorough mathematical analyses of shell elements. A particularly important motivation for this is the understanding and treatment of the deficiencies associated with the analysis of thin shells (among which is the locking phenomenon). We then survey these deficiencies, in the framework of the asymptotic behaviour of shell models. We conclude the article by giving some detailed guidelines to numerically assess the performance of shell finite elements when faced with these pathological phenomena, which is essential for the design of improved procedures.

Nonlinear Inverse Perturbation in Structural Dynamics Redesign of Risers

1985 ◽  
Vol 107 (2) ◽  
pp. 256-263 ◽  
Author(s):  
M. M. Bernitsas ◽  
C. J. Hoff ◽  
J. E. Kokarakis
Keyword(s):  
Offshore Structures ◽  
Mode Shapes ◽  
Drilling Mud ◽  
Element Analysis ◽  
Marine Risers ◽  
Geometric Stiffness ◽  
Stiffness Matrices ◽  
The Finite Element Analysis ◽  
Baseline System ◽  
Structural Redesign

Marine risers, and offshore structures in general, may have undesirable natural frequencies and/or mode shapes. Structural redesign is mandatory in such cases. An Inverse Perturbation Redesign (IPR) method, which uses only the finite element analysis of the baseline system and was developed in previous work for general structures, is extended in this work to handle systems with geometric stiffness matrices like marine risers. The IPR method is currently applicable to undamped structural systems or systems with Rayleigh damping and is valid for large or small changes which are frequently required to change modal characteristics of offshore structures. The vibratory characteristics of risers can be altered by modifying among others, the riser top tension, the drilling mud density and the geometry of the riser tubes. The effects of their change on the riser frequencies and modes are derived and applied to two typical riser redesign problems using the IPR method.

Practical Considerations for the Structural Analysis of Offshore Topside Structures Under Gas Explosion Accidents

2012 ◽  
Author(s):  
Dae Suk Han ◽  
Gyusung Kim ◽  
Woo Seung Sim ◽  
Young Sik Jang ◽  
Hyun Soo Shin
Keyword(s):  
Structural Analysis ◽  
Offshore Structures ◽  
Structural Members ◽  
Gas Explosion ◽  
Element Analysis ◽  
Numerical Investigations ◽  
The Finite Element Analysis ◽  
Explosion Accidents ◽  
Blast Loadings ◽  
Dynamic Structural Analysis

Gas explosion accidents have been recognized as a major hazard of offshore facilities in oil & gas industries. Due to the nature of offshore topside structures, even a single collapse of structural members or equipments may lead to enormous economic and environmental losses. Therefore, such potential hazards that cause the accidental collapse need to be evaluated closely. Gas explosion has been categorized as an important issue of the design of offshore structures regarding the severity of the accident. This paper presents practical considerations for the nonlinear dynamic structural analysis of offshore structures under blast loadings from gas explosion accidents. Numerical investigations including modeling of blast loads and idealization of structural materials and members have been conducted for the overall topside structures. As a design step for offshore structures under blast loadings, an applicable guidance on the finite element analysis (FEA) is described in this study.

Fully automatic mesh generator for 3D domains of any shape

1990 ◽  
Vol 2 (3) ◽  
pp. 187-218 ◽  
Author(s):  
P.L. George ◽  
F. Hecht ◽  
E. Saltel
Keyword(s):  
Mesh Generator ◽  
Fully Automatic ◽  
Automatic Mesh

Topology optimisation via the moving iso-surface threshold method: implementation and application

2014 ◽  
Vol 118 (1201) ◽  
pp. 315-342 ◽  
Author(s):  
S. Vasista ◽  
L. Tong
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Leading Edge ◽  
Topology Optimisation ◽  
Threshold Method ◽  
Element Analysis ◽  
The Finite Element Analysis ◽  
Wing Skin ◽  
Automatic Mesh ◽  
3D Wing

AbstractTopology optimisation is a useful tool for the design of aircraft structures. This work details how the new moving iso-surface threshold (MIST) topology optimisation method works and how it can be applied to aircraft structural design. This method has been coupled with commercial finite element analysis software in a simple manner without requiring the modification of the commercial software source code. In this way the user is able to take advantage of the finite element analysis tools such as automatic mesh generation and efficient solving. The extension of the method to 3D designs is also presented. The topology results of a 2D leading-edge rib for stiffness, stress and morphing objectives and a 3D wing skin stringer for stress design demonstrate the functionality of this method.

Some Notes on the Finite Element Analysis of Tires

1995 ◽  
Vol 23 (3) ◽  
pp. 175-188 ◽  
Author(s):  
R. Gall ◽  
F. Tabaddor ◽  
D. Robbins ◽  
P. Majors ◽  
W. Sheperd ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Local Analysis ◽  
Element Analysis ◽  
Shell Elements ◽  
Development Cycle ◽  
The Finite Element Analysis ◽  
Modeling Techniques ◽  
Massively Parallel Processing ◽  
New Generation

Abstract Over the past ten years the Finite Element Analysis (FEA) has been increasingly integrated into the tire design process. The FEA has been used to study the general tire behavior, to perform parameter studies, and to do comparative analyses. To decrease the tire development cycle, the FEA is now being used as a replacement for certain tire tests. This requires the accuracy of the FEA results to be within those test limits. This paper investigates some of the known modeling techniques and their impact on accuracy. Some of the issues are the use of shell elements, assumptions for boundary conditions, and global/local analysis approaches. Finally, the use of new generation supercomputers, massively parallel processing systems (MPP), is discussed.

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