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Optimization and Robustness

Analysis of a Stent

Axel Reichert

Dassault Systemes Deutschland GmbH

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1 CAD Modeling

2 Finite Element Analysis

3 Fatigue Analysis

4 Parameter Optimization

5 Shape Optimization

6 Robustness Analysis

Overview

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CAD Modeling SolidWorks

2D sketch 2D geometry

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Finite Element Analysis Abaqus

2D mesh

3D mesh

Wrapped 3D mesh

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Finite Element Analysis

Artery (anisotropic-hyperelastic)

Stent (elastic-plastic)

Expansion/crimping cylinders

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Finite Element Analysis Crimping and insertion Blood pressure loading

Preloading stress Cyclic stress

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Fatigue Analysis fe-safe

Surgical stainless steel with

ultimate tensile strength

Brown-Miller (critical plane method)

with Gerber (fatigue reserve factor)

Infinite life estimate: 1 billion cycles

(around 20 years)

Fatigue envelope:

Worst FRF: 1.223 Mean stress (MPa)

Str

ain (1e−

6)

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Parameter Optimization Isight

Design sweet spot

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Parameter Optimization Shape Changes

Baseline Parameter optimized Comparison

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Parameter Optimization Mises Stress

Parameter optimized Baseline

5%

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Parameter Optimization Fatigue Reserve Factor

Parameter optimized Baseline

8%

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Shape Optimization Tosca Structure.shape

Method

Controller approach

Objective

Minimize maximum Mises stress

over all load cases

Geometrical restrictions

Preserve manufacturability

Cyclic symmetry

Design nodes

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Shape Optimization Shape Changes

Parameter optimized Shape optimized

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Shape Optimization Mises Stress

Shape optimized Parameter optimized

14%

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Shape Optimization Fatigue Reserve Factor

Shape optimized Parameter optimized

14%

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Robustness Analysis Isight

Artery dimensions are varied

DoE generates approximation

Monte Carlo simulation uses

approximation

Radius Mean

(mm)

Standard deviation

(mm)

Outer 1.62 0.028

Inner 1.13 0.018

Inner radius

Outer

radius

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Robustness Analysis Generating the Approximation

Response surface

DoE

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Robustness Analysis Using the Approximation

Monte Carlo simulation Fatigue reserve factor

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Summary Process Integration with the Power of the Portfolio

CAD Modeling

Finite Elements

Fatigue

Parametric

Non-Parametric

Design Optimization Drives and Analysis

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