Calculation of Shell Element Failure Based on the State of Stress Inside of a Neck

2015 ◽  
Author(s):  
R. C. Dragt ◽  
J. Kraus ◽  
C. L. Walters
Keyword(s):  
Three Dimensional ◽  
Shell Element ◽  
Offshore Structures ◽  
Shell Elements ◽  
Thin Walled Structures ◽  
Coulomb Failure ◽  
Correct Determination ◽  
Element Failure ◽  
The Relationship

Simulation of failure in thin-walled structures is critical for the correct determination of crash performance of ships and offshore structures. Typically, shell elements are used, but these elements are not able to adequately capture local failure, especially inside of a neck. This paper addresses these gaps by adapting the Bridgman (1952) model of a neck inside of a plate by making it three-dimensional and offering an estimate of the relationship between state parameters of a shell element and the geometry inside of a neck. Finally, recommendations are also made about how to interface this information with the Modified Mohr-Coulomb failure locus to create a practical algorithm for assessing failure in shell elements.

A Finite Element for the Analysis of Shell Intersections

1996 ◽  
Vol 118 (4) ◽  
pp. 399-406 ◽  
Author(s):  
W. J. Koves ◽  
S. Nair
Keyword(s):  
Finite Element ◽  
Stress State ◽  
Three Dimensional ◽  
Shell Element ◽  
Theory Of Elasticity ◽  
Shell Elements ◽  
Asme Code ◽  
Form Theory ◽  
Computation Scheme ◽  
Shell Intersections

A specialized shell-intersection finite element, which is compatible with adjoining shell elements, has been developed and has the capability of physically representing the complex three-dimensional geometry and stress state at shell intersections (Koves, 1993). The element geometry is a contoured shape that matches a wide variety of practical nozzle configurations used in ASME Code pressure vessel construction, and allows computational rigor. A closed-form theory of elasticity solution was used to compute the stress state and strain energy in the element. The concept of an energy-equivalent nodal displacement and force vector set was then developed to allow complete compatibility with adjoining shell elements and retain the analytical rigor within the element. This methodology provides a powerful and robust computation scheme that maintains the computational efficiency of shell element solutions. The shell-intersection element was then applied to the cylinder-sphere and cylinder-cylinder intersection problems.

scholarly journals APPLICATION OF SUPERELEMENTS IN STATIC ANALYSIS OF THIN‐WALLED STRUCTURES

2004 ◽  
Vol 10 (2) ◽  
pp. 113-122
Author(s):  
Ireneusz Kreja ◽  
Tomasz Mikulski ◽  
Czeslaw Szymczak
Keyword(s):  
Static Analysis ◽  
Standard Procedure ◽  
Dimensional Model ◽  
Fem Model ◽  
Shell Elements ◽  
One Dimensional ◽  
Thin Walled Structures ◽  
Thin Walled ◽  
Proper Solutions

A concept of a beam superelement is suggested as a new tool in the static analysis of structures made of thin‐walled members. This proposal seems to be especially attractive for treating the problems where the existing one‐dimensional models do not provide proper solutions. This class of problems includes, for instance, the torsion of thin‐walled beams with battens and the determination of the bimoment distribution at the nodes of frames made of thin‐walled members. The entire segment of the thin‐walled beam with warping stiffener or the whole node of the frame is modelled with shell elements. The stiffness matrix of such thin‐walled beam superelement can be estimated according to the standard procedure of the enforced unit displacements. The accuracy of the proposed one‐dimensional model has proved to be comparable to that offered by the detailed FEM model where the whole structure is represented by a very large number of shell elements.

Low-Temperature Mobility of Thionine in a Faujasite Cage

1994 ◽  
Vol 366 ◽  
Author(s):  
F. W. Deeg ◽  
M. Ehrl ◽  
C. Bräuchle
Keyword(s):  
Low Temperature ◽  
Pore Structure ◽  
Zeolite Y ◽  
Three Dimensional ◽  
Molecular Size ◽  
Energy Difference ◽  
Temperature Dependent ◽  
Host Interaction ◽  
The Relationship

ABSTRACTWe have used low-temperature optical spectroscopy to characterize the guest/host interaction of thiazine and oxazine dyes encapsulated in the three-dimensional pore structure of faujasite cages. The system thionine in dehydrated zeolite-Y exhibits a thermal and optical equilibrium between two spectroscopically distinguishable species. Temperature-dependent measurements allow the determination of the energy difference and barrier between these two forms as 170 cm−1 and 120 cm−1, respectively. The two forms are associated with two different locations/conformations of the chromophore within the faujasite pore structure. The degree of freedom responsible for the interconversion of the two forms is extremely sensitive to the relationship between molecular size and form of the void.

scholarly journals Robustness of Hierarchical Laminated Shell Element Based on Equivalent Single-Layer Theory

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Jae S. Ahn ◽  
Seung H. Yang ◽  
Kwang S. Woo
Keyword(s):  
Three Dimensional ◽  
Single Layer ◽  
Laminated Composite ◽  
Shell Element ◽  
Linear Mapping ◽  
Large Radius ◽  
Laminated Shell ◽  
Shell Elements ◽  
Aspect Ratios ◽  
Material Conditions

This paper deals with the hierarchical laminated shell elements with nonsensitivity to adverse conditions for linear static analysis of cylindrical problems. Displacement approximation of the elements is established by high-order shape functions using the integrals of Legendre polynomials to ensureC0continuity at the interface between adjacent elements. For exact linear mapping of cylindrical shell problems, cylindrical coordinate is adopted. To find global response of laminated composite shells, equivalent single-layer theory is also considered. Thus, the proposed elements are formulated by the dimensional reduction from three-dimensional solid to two-dimensional plane which allows the first-order shear deformation and considers anisotropy due to fiber orientation. The sensitivity tests are implemented to show robustness of the present elements with respect to severe element distortions, very high aspect ratios of elements, and very large radius-to-thickness ratios of shells. In addition, this element has investigated whether material conditions such as isotropic and orthotropic properties may affect the accuracy as the element distortion ratio is increased. The robustness of present element has been compared with that of several shell elements available in ANSYS program.

Consequences of Using the Plane Stress Assumption for Damage Calculations in Crash Analyses

2014 ◽  
Author(s):  
Carey L. Walters ◽  
Lars O. Voormeeren
Keyword(s):  
Plane Stress ◽  
Stress Triaxiality ◽  
Shell Element ◽  
Element Model ◽  
Offshore Structures ◽  
Two Dimensions ◽  
Shell Structures ◽  
Planar Case ◽  
Lode Parameter ◽  
Shell Elements

Simulation of failure in plate materials (represented as shell elements) is critical for the correct determination of crash performance of ships and offshore structures. This need has traditionally been filled with failure loci that give the failure strain in terms of stress triaxiality. In recent years, a third dimension (Lode parameter) has been introduced in the form of the Modified Mohr Coulomb failure criterion and Lode parameter adjusted Gurson-type models. This development introduces ambiguity for shell structures, in which only two dimensions are represented. The typical way of addressing this is to assume that shell structures fail in plane stress, thus reducing the problem back to 2-D. However, the assumption of plane stress is violated as soon as necking begins, causing different stress triaxialities and Lode parameters than would be expected from the planar case. More importantly, the inhomogenous necked region is then homogenized over the entire shell element. In this paper, the consequences of the through-thickness plane stress assumption are assessed through a finite element model of a plate that is subjected to a far-field stress.

Four-Node Quadrilateral Shell Element MITC4

2016 ◽  
Vol 825 ◽  
pp. 99-104 ◽  
Author(s):  
Edita Dvořáková ◽  
Bořek Patzák
Keyword(s):  
Three Dimensional ◽  
Shell Element ◽  
Thin Shells ◽  
Element Formulation ◽  
Finite Element Code ◽  
Shear Locking ◽  
Benchmark Problem ◽  
Quadrilateral Element ◽  
Shell Elements ◽  
Continuum Description

Four-node quadrilateral element MITC4 applicable to both thick and thin shells is presented. The element formulation starts from three-dimensional continuum description degenerated to shell behavior. Shear locking, which is common problem in analysis of thin shells, is overcome by the use of MITC (Mixed Interpolation of Tensorial Components) approach. Element has been implemented into finite element code OOFEM and its performance is demonstrated on Scordelis-Lo shell, a benchmark problem frequently used in the evaluation of shell elements.

Preoperative determination of anatomic variations of the small saphenous vein for varicose vein surgery by three-dimensional computed tomography venography

2011 ◽  
Vol 27 (5) ◽  
pp. 235-241 ◽  
Author(s):  
S-Y Kim ◽  
E-A Park ◽  
Y-C Shin ◽  
S-I Min ◽  
W Lee ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Saphenous Vein ◽  
Varicose Vein ◽  
Preoperative Evaluation ◽  
Three Dimensional ◽  
Anatomical Variations ◽  
The Impact ◽  
The Relationship ◽  
Computed Tomography Venography

Objective To define the anatomical variations of small saphenous vein (SSV) for varicose vein (VV) surgery by three-dimensional computed tomography venography (3D-CTV) and to analyse the impact of this preoperative evaluation on surgical outcomes. Methods A total of 120 consecutive limbs with SSV insufficiency having undergone VV surgery from January 2005 until December 2007 were enrolled. The medical records and images were analysed retrospectively. Results The relationship between SSV and gastrocnemial vein (GNV) were categorized into two: (a) SSV and GNV drained to popliteal vein (PV) separately (100 limbs, 87%) and (b) SSV and GNV made common channel which drained to PV (15 limbs, 13%). Saphenopopliteal junction morphology was normal (75 limbs), severe tortuosity near PV (19 limbs), ampullary ectasia (4 limbs) and duplicated drainage to PV (2 limbs). No recurrence of VV was noted. Conclusions CTV can provide thorough preoperative anatomic information of the SSV variations and reduce the recurrence of VV.

scholarly journals ESL Based Cylindrical Shell Elements with Hierarchical Shape Functions for Laminated Composite Shells

2015 ◽  
Vol 2015 ◽  
pp. 1-11
Author(s):  
Jae S. Ahn ◽  
Seung H. Yang ◽  
Kwang S. Woo
Keyword(s):  
Cylindrical Shell ◽  
Three Dimensional ◽  
Single Layer ◽  
Laminated Composite ◽  
Shell Element ◽  
Composite Shells ◽  
Shell Elements ◽  
Cylindrical Coordinate ◽  
Laminated Composite Shells ◽  
Geometry Mapping

We introduce higher-order cylindrical shell element based on ESL (equivalent single-layer) theory for the analysis of laminated composite shells. The proposed elements are formulated by the dimensional reduction technique from three-dimensional solid to two-dimensional cylindrical surface with plane stress assumption. It allows the first-order shear deformation and considers anisotropic materials due to fiber orientation. The element displacement approximation is established by the integrals of Legendre polynomials with hierarchical concept to ensure theC0-continuity at the interface between adjacent elements as well asC1-continuity at the interface between adjacent layers. For geometry mapping, cylindrical coordinate is adopted to implement the exact mapping of curved shell configuration with a constant curvature with respect to any direction in the plane. The verification and characteristics of the proposed element are investigated through the analyses of three cylindrical shell problems with different shapes, loadings, and boundary conditions.

Mixed-dimensional coupling modeling for laser forming process

2014 ◽  
Vol 228 (16) ◽  
pp. 2950-2959
Author(s):  
Hong Shen ◽  
Jun Hu ◽  
Zhenqiang Yao
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Shell Element ◽  
Element Model ◽  
Thermomechanical Analysis ◽  
Coupling Method ◽  
Computational Time ◽  
Laser Forming ◽  
Forming Process ◽  
Shell Elements

Efficient laser forming modeling for industrial application is still in the developing stage and many researchers are in the process of modifying it. Conventional three-dimensional finite element models are still expensive on computational time. In this paper, a finite element model adopting a shell-solid coupling technique is developed for the thermomechanical analysis of laser forming process. In the shell-solid coupling method, an additional shell element plane is utilized to transfer heat flux and displacement from the solid elements to the shell elements. The effects of the additional interface shell element thickness on temperature distribution and final distortion are investigated. The presented shell-solid coupling method is evaluated by the results of three-dimensional simulations and experimental data.

Sign in / Sign up

Export Citation Format

Share Document