Finite Element Stent Design: Parametric Modeling of Braided Wirestents Using PyFormex

2007 ◽  
Author(s):  
Matthieu De Beule ◽  
Benedict Verhegghe ◽  
Peter Mortier ◽  
Kim Van Loo ◽  
Rudy Van Impe ◽  
...  
Keyword(s):  
Finite Element ◽  
Mechanical Behavior ◽  
Stent Graft ◽  
Computer Model ◽  
Geometrical Model ◽  
Parametric Modeling ◽  
Finite Element Simulations ◽  
Stent Design ◽  
Wide Range

Selfexpandable stent(graft)s are supporting tubular mesh devices used for the treatment of occlusive diseases and for the ‘exclusion’ of aneurysms. Wirestents are a class of flexible stents braided from a set of ultra fine wires and currently manufactured in a wide range of materials (e.g. phynox, nitinol, polymers) and compositions (single or multilayer). For design purposes as well as for studying the mechanical behavior of such a device by finite element simulations, a geometrical model using 1D elements will usually be appropriate. However, the computer model will contain a very large number of such elements, and building the geometrical model using classical CAD methodologies may become laborious. Consequently, literature dedicated to the mechanical behavior of braided wirestents is (very) scarce and the stent(graft)s are simplified as virtual single sheets [1].

A Compliant Transmission Mechanism With Intermittent Contacts for Cycle-Doubling

2006 ◽  
Vol 129 (1) ◽  
pp. 114-121 ◽  
Author(s):  
Nilesh D. Mankame ◽  
G. K. Ananthasuresh
Keyword(s):  
Finite Element ◽  
Conceptual Design ◽  
Finite Element Simulations ◽  
Nonlinear Finite Element ◽  
Transmission Mechanism ◽  
Input Frequency ◽  
Length Scales ◽  
Wide Range ◽  
Macro Scale ◽  
Functional Prototype

A novel compliant transmission mechanism that doubles the frequency of a cyclic input is presented in this paper. The compliant cycle-doubler is a contact-aided compliant mechanism that uses intermittent contact between itself and a rigid surface. The conceptual design for the cycle-doubler was obtained using topology optimization in our earlier work. In this paper, a detailed design procedure is presented for developing the topology solution into a functional prototype. The conceptual design obtained from the topology solution did not account for the effects of large displacements, friction, and manufacturing-induced features such as fillet radii. Detailed nonlinear finite element analyses and experimental results from quasi-static tests on a macro-scale prototype are used in this paper to understand the influence of the above factors and to guide the design of the functional prototype. Although the conceptual design is based on the assumption of quasi-static operation, the modified design is shown to work well in a dynamic setting for low operating frequencies via finite element simulations. The cycle-doubler design is a monolithic elastic body that can be manufactured from a variety of materials and over a range of length scales. This makes the design scalable and thus adaptable to a wide range of operating frequencies. Explicit dynamic nonlinear finite element simulations are used to verify the functionality of the design at two different length scales: macro (device footprint of a square of 170mm side) at an input frequency of 7.8Hz; and meso (device footprint of a square of 3.78mm side) at an input frequency of 1kHz.

Postbuckled Square Thin Film Membranes Under Differential Pressure

2001 ◽  
Vol 695 ◽  
Author(s):  
Torsten Kramer ◽  
Oliver Paul
Keyword(s):  
Thin Film ◽  
Finite Element ◽  
Silicon Nitride ◽  
Transition Process ◽  
Differential Pressure ◽  
Finite Element Simulations ◽  
Membrane Material ◽  
Silicon Nitride Films ◽  
Wide Range ◽  
Quantitative Results

ABSTRACTWe report quantitative results on the load-deflection response of compressively prestressed square membranes under differential pressure. The membranes consist of 0.485 μm and 1.9 μm thick silicon nitride films. For these square membranes we observed a new symmetry transition of the deflection profile between a state without reflection symmetries at small loads to a state with reflection symmetries at sufficiently large loads. The load-deflection response was modeled by finite element simulations covering a wide range of prestrains e0 and pressures using various geometries. From the symmetry transition process, Young's modulus E = (150±5) GPa and the prestrain ε0 = (1.6±0.1) 10-3 of the membrane material was extracted.

On determination of material parameters from loading and unloading responses in nanoindentation with a single sharp indenter

2006 ◽  
Vol 21 (4) ◽  
pp. 995-1011 ◽  
Author(s):  
Lugen Wang ◽  
S.I. Rokhlin
Keyword(s):  
Finite Element ◽  
Strain Hardening ◽  
Yield Stress ◽  
Finite Element Simulations ◽  
Strain Hardening Exponent ◽  
Scaling Functions ◽  
Stress And Strain ◽  
Wide Range ◽  
Loading And Unloading

This paper quantitatively describes the loading-unloading response in nanoindentation with sharp indenters using scaling analyses and finite element simulations. Explicit forward and inverse scaling functions for an indentation unloading have been obtained and related to those functions for the loading response [L. Wang et al., J. Material Res.20(4), 987–1001 (2005)]. The scaling functions have been obtained by fitting the large deformation finite element simulations and are valid from the elastic to the full plastic indentation regimes. Using the explicit forward functions for loading and unloading, full indentation responses for a wide range of materials can be obtained without use of finite element calculations. The corresponding inverse scaling functions allow one to obtain material properties from the indentation measurements. The relation between the work of indentation and the ratio between hardness and modulus has also been studied. Using these scaling functions, the issue of nonuniqueness of the determination of material modulus, yield stress, and strain-hardening exponent from nanoindentation measurements with a single sharp indenter has been further investigated. It is shown that a limited material parameter range in the elastoplastic regime can be defined where the material modulus, yield stress, and strain-hardening exponent may be determined from only one full indentation response. The error of such property determination from scattering in experimental measurements is determined.

A Study of Mechanical Behavior of an Encapsulated Stent Design Using Finite Element Analysis

2014 ◽  
pp. 391-394
Author(s):  
Kiruthigha Shanmuga Sundaram ◽  
Davidson Jebaseelan ◽  
Rince Jose ◽  
Ranjitha Rebecca Jeevan ◽  
George Joseph ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Mechanical Behavior ◽  
Stent Design ◽  
Element Analysis

scholarly journals On the Influence of Material Parameters in a Complex Material Model for Powder Compaction

2016 ◽  
Vol 25 (10) ◽  
pp. 4408-4415 ◽  
Author(s):  
Hjalmar Staf ◽  
Per Lindskog ◽  
Daniel C. Andersson ◽  
Per-Lennart Larsson
Keyword(s):  
Finite Element ◽  
Plastic Strain ◽  
Continuum Mechanics ◽  
Material Model ◽  
Sensitivity Study ◽  
Powder Compaction ◽  
Finite Element Simulations ◽  
Complex Material ◽  
Material Parameters ◽  
Wide Range

Abstract Parameters in a complex material model for powder compaction, based on a continuum mechanics approach, are evaluated using real insert geometries. The parameter sensitivity with respect to density and stress after compaction, pertinent to a wide range of geometries, is studied in order to investigate completeness and limitations of the material model. Finite element simulations with varied material parameters are used to build surrogate models for the sensitivity study. The conclusion from this analysis is that a simplification of the material model is relevant, especially for simple insert geometries. Parameters linked to anisotropy and the plastic strain evolution angle have a small impact on the final result.

Mechanical behavior of linear amorphous polymers: Comparison between molecular dynamics and finite-element simulations

2012 ◽  
Vol 85 (2) ◽  
Author(s):  
Mathieu Solar ◽  
Hendrik Meyer ◽  
Christian Gauthier ◽  
Christophe Fond ◽  
Olivier Benzerara ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Finite Element ◽  
Mechanical Behavior ◽  
Amorphous Polymers ◽  
Finite Element Simulations
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