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finite-element-analysis and in vitro study of bioabsorbable polymer stent designs

4th European Conference of the International Federation for Medical and Biological Engineering (ECIFMBE)

作者： Schultze, C. Grabow, N. Martin, H. Schmitz, K. -P. Univ Rostock Inst Biomed Engn Rostock Germany

ISBN: (纸本)9783540892076

Objectives: Implantation of bare metal stents has therapeutic limitations, such as the permanent nature and the thrombogenicity. This has lead to the development of bioabsorbable polymer stents. With regard to the material, the stent design is a highly important factor for mechanical performance. Hence, in this study we examined the influence of the stent design on the mechanical properties of the entire stent. Materials/Methods: Three different designs were created as two dimensional stent outer shells with the CAD software Pro/Engineer Wildfire 3.0, Parametric Technology Corporation, Needham, USA. The stent outer shell was the basis for the three dimensional modeling with the preprocessor Patran, MSC Software Corporation, Santa Ana, CA, USA. For the nonlinear finite-element-analysis stent expansion, recoil and the pressure of the vessel were defined in separate load cases. Abaqus, Dassault Systemes, Providence, RI, USA, was used as processor and postprocessor. Three designs with the most promising results in terms of mechanical properties were used for manufacturing prototypes were investigated regarding recoil and radial strength. Stents were with from polymer tubes of a poly-(L-lactid) based polymer blend with an inner diameter of 1.4 mm and a wall thickness of 0.15 mm, for prototype manufacturing. Results: In the finite-element-analysis the recoil of Design A, B and C was 2.18%, 4.26%, and 2.82% and the collapse pressure was 0.81 bar, 0.66 bar, and 0.52 bar, respectively. In vitro testing yielded recoil values for Design A, B and C of: 2.09 +/- 0.11%, 2.14 +/- 0.25%, and 2.15 +/- 0.21%. The collapse pressure was 0.40 +/- 0.03 bar, 0.34 +/- 0.06 bar, and 0.44 +/- 0.04 bar, respectively. Conclusion: The differences of the results may be found in the elasto-plastic defined material properties. In next steps the finite-element-model will be further improved as a tool to reduce the need for experimental investigations during the development of polymer stents.

关键词： bioabsorbable polymer stent finite-element-analysis Recoil Collapse Mechanical Properties

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Intraoperative impaction of total knee replacements: An explicit finite-element-analysis of principal stresses in ceramic vs. cobalt-chromium femoral components

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CLINICAL BIOMECHANICS 2010年第10期25卷 1018-1024页

作者： Kluess, Daniel Mittelmeier, Wolfram Bader, Rainer Univ Rostock Dept Orthopaed D-18057 Rostock Germany

Background: In connection with technological advances in the manufacturing of medical ceramics, a newly developed ceramic femoral component was introduced in total knee arthroplasty. We generated an explicit finite-element-model to calculate the stresses developed under the highly dynamic intraoperative impaction with regard to cobalt-chromium and ceramic implant material as well as application of a silicone cover in order to reduce stress. Methods: The impaction was calculated with the hammer hitting the backside of the impactor at previously measured initial velocities. Subsequently the impactor, consisting of a steel handhold and a polyoxymethylene head, hit the femoral component. Instead of modelling femoral bone, the implant was mounted on four spring elements with spring constants previously determined in an experimental impaction model. The maximum principal stresses in the implants were evaluated at 8000 increments during the first 4 ms of impact. Findings: The ceramic implant showed principal stresses 10% to 48% higher than the cobalt chromium femoral component. The simulation of a 5 mm thick silicone layer between the impactor and the femoral component showed a strong decrease of vibration resulting in a reduction of 54% to 68% of the maximum stress amounts. The calculated amounts of principal stress were beneath the ultimate bending strengths of each material. Interpretation: Based on the results, intraoperative fracture of femoral components in total knee replacement may not be caused solely by impaction, but also by contributing geometrical factors such as inadequate preparation of the distal femur. In order to minimize the influence of impaction related stress peaks we recommend limiting the velocity as well as the weight of the impaction hammer when inserting femoral components. The silicone cover seems to deliver a strong decrease of implant stress and should be considered in surgery technique in the future. (c) 2010 Elsevier Ltd. All rights reserved

关键词： Total knee replacement Impaction finite-element-analysis Ceramics Femoral component

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Reduced Order Model of the Induction Machine Derived from finite-element-analysis 22

Reduced Order Model of the Induction Machine Derived from Fi...

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22nd IEEE International Conference on Electrical Machines (ICEM)

作者： Bals, Christoph Gerling, Dieter AUDI AG Dept Proc & Methods Tech Dev D-85045 Ingolstadt Germany Univ Fed Def Munich Dept Elect Drives & Actuators D-85577 Neubiberg Germany

ISBN: (纸本)9781509025381

This paper proposes a method to automatically derive a reduced order model of the induction machine from the electromagnetic finite-element-analysis. The benefit is a consistent workflow between the detailed designing process of the electrical machine and system level modeling. The basis of the model structure are the differential equations of the induction machine in rotating d-q coordinates. The equations are combined with the nonlinear correlation between current and flux linkage. Therefore a current driven parameter study in the finite-element-analysis is performed. The voltage driven reduced order model is able to start the simulation in steady-state because an initialization process is implemented. The validation results show a good agreement between the reduced order model of the induction machine and the voltage driven finite-element-analysis.

关键词： finite-element-analysis induction machine model simplification reduced order model

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FPGA Permanent Magnet Synchronous Motor Floating-Point Models with Variable-DQ and Spatial Harmonic finite-element analysis Solvers

FPGA Permanent Magnet Synchronous Motor Floating-Point Model...

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15th International Power Electronics and Motion Control Conference and Exposition (EPE-PEMC ECCE Europe)

作者： Dufour, Christian Cense, Sebastien Yamada, Takashi Imamura, Ryoko Belanger, Jean OPAL RT Technol 1751 RichardsonBur 2525 Montreal PQ H3K 1G6 Canada JSOL Corp Engn Technol Dept Chuo Ku Tokyo Japan

ISBN: (纸本)9781467319720

This paper explains the FPGA implementation of a Permanent Magnet Synchronous Motor (PMSM) model using the latest JMAG-RT finite-element-analysis software's real-time models: variable-DQ and Spatial Harmonic. In the variable-DQ (VDQ) model, the DQ inductances are varied according to the saturation level and a sinusoidal back-EMF is assumed. In the Spatial Harmonic (SH) model, the instantaneous magnetisation state is used to integrate the model;differential inductance and nonsinusoidal back-EMF are considered for all possible points of operation, resulting in improved precision, especially in transient states. The SH model also includes torque and current harmonics contents induced by machine slots and back-EMF spatial configurations. Both VDQ and SH models are implemented in a ML605 FPGA board running in the RT-LAB real-time simulation environment.

关键词： Hardware-In-the-Loop Simulation PMSM FPGA. Power Electronics finite-element-analysis

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Reduced Order Model of the Induction Machine Derived from finite-element-analysis

Reduced Order Model of the Induction Machine Derived from Fi...

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International Conference on Electrical Machines

作者： Christoph Bals Dieter Gerling Department for Processes and Methods of the Technical Development AUDI AG Ingolstadt 85045 Germany Department of Electrical Drives and Actuators University of Federal Defense Munich Neubiberg 85577 Germany

ISBN: (纸本)9781509025398

关键词： finite-element-analysis Induction machine Model simplification Reduced order model

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FPGA Permanent Magnet Synchronous Motor Floating-Point Models with Variable-DQ and Spatial Harmonic finite-element analysis Solvers

FPGA Permanent Magnet Synchronous Motor Floating-Point Model...

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International Power Electronics and Motion Control Conference

作者： Christian Dufour Sebastien Cense Takashi Yamada Ryoko Imamura Jean Belanger OPAL-RT Technologies JSOL Corporation/Engineering Technology Dept.

ISBN: (纸本)9781467319706

This paper explains the FPGA implementation of a Permanent Magnet Synchronous Motor (PMSM) model using the latest JMAG-RT finite-element-analysis software's real-time models: variable-DQ and Spatial Harmonic. In the variable-DQ (VDQ) model, the DQ inductances are varied according to the saturation level and a sinusoidal back-EMF is assumed. In the Spatial Harmonic (SH) model, the instantaneous magnetisation state is used to integrate the model;differential inductance and non-sinusoidal back-EMF are considered for all possible points of operation, resulting in improved precision, especially in transient states. The SH model also includes torque and current harmonics contents induced by machine slots and back-EMF spatial configurations. Both VDQ and SH models are implemented in a ML605 FPGA board running in the RT-LAB real-time simulation environment.

关键词： Hardware-In-the-Loop Simulation PMSM FPGA. Power Electronics finite-element-analysis

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Numerical analysis of the biomechanical complications accompanying the total hip prosthesis: prosthetic bone remodeling and migration

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MATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK 2015年第9期46卷 881-893页

作者： Behrens, B. -A. Bouguecha, A. Vucetic, M. Escobar, S. Betancur Stukenborg-Colsman, C. Lerch, M. Nolte, I. Almohallami, A. Leibniz Univ Hannover Inst Umformtech & Umformmaschinen Hannover Germany Hannover Med Sch Orthopad Klin Annastift Hannover Germany Univ Vet Med Hannover Klin Kleintiere Hannover Germany

Aseptic loosening of the prosthesis is still a problem in artificial joint implants. The loosening can be caused by, among other factors, resorption of the bone surrounding the prosthesis owing to stress shielding. A numerical model was developed at the Institute of Forming Technology and Machines, Leibniz Universitat Hannover, in order to anticipate the bone remodelling process according to the stress shielding. This study is carried out to validate this model by means of DEXA- as well as CT-clinical studies on patients with different kinds of prostheses and use it to map the cup migration. The model was applied to the periprosthetic femur and pelvis. In both cases it shows very good results. With a mean difference of 12% in case of the femur and 6.8% in case of the pelvis the numerical bone remodelling model is successfully validated. A new method is developed to map the prosthetic migration in the pelvis. Using mechanical relationships and remeshing regulations the finite-element-analysis (FEA) calculates the possible migration of the cup in pelvis. This method was applied to polyethylene cup and showed good results in comparison with a clinical study. In order to increase the accuracy of the numerical model, the difference in hip contact forces caused by the migration of the cup is calculated by multi body simulation and embedded in the FEA using online coupling software developed by our scientific group.

关键词： Bone remodelling cup migration finite-element-analysis DEXA validation multi body simulation

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Vibration analysis of non-homogeneous circular plate of nonlinear thickness variation by differential quadrature method

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JOURNAL OF SOUND AND VIBRATION 2006年第4-5期298卷 892-906页

作者： Gupta, U. S. Lal, R. Sharma, Seema Indian Inst Technol Dept Math Roorkee 247667 Uttar Pradesh India

Free axisymmetric vibrations of non-homogeneous isotropic circular plates of nonlinear thickness variation have been analyzed on the basis of classical plate theory employing the differential quadrature (DQ) method. The non-homogeneity is assumed to arise due to the variation in Young's modulus and also the density of the plate material. The first three natural frequencies have been obtained for clamped, simply supported and free edge conditions, taking grid points as zeros of Chebyshev polynomials. The effect of non-homogeneity and thickness variation on natural frequencies of vibration has been investigated for the first three modes of vibration. The results for linear as well as parabolic thickness variations have been obtained as special cases. Comparison studies have been carried out to establish the accuracy and versatility of the present DQ method. (c) 2006 Elsevier Ltd. All rights reserved.

关键词： finite-element-analysis VARIABLE THICKNESS AXISYMMETRIC VIBRATIONS ANNULARPLATES TRANSVERSE VIBRATION ELASTIC-FOUNDATION VARYING THICKNESS

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Evaluation of tension field theory for wrinkling analysis with respect to the post-buckling study

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JOURNAL OF APPLIED MECHANICS-TRANSACTIONS OF THE ASME 2004年第4期71卷 532-540页

作者： Iwasa, T Natori, MC Higuchi, K Univ Tokyo Dept Aeronaut & Astronaut Tokyo Japan Inst Space & Astronaut Sci Div Spacecraft Engn Kanagawa 2298510 Japan

A comparative study of two representative wrinkling theories, a bifurcation theory and a tension field theory, is carried out for quantitative evaluation of the tension field theory regarding wrinkling analysis. Results obtained from the bifurcation theory show the limitations of tension field theory on the wrinkling analysis. Existence of compressive stresses caused by wrinkling phenomena, which is not accounted for tension field theory, is quantitatively presented. Considering strain energy due to these compressive stresses and geometrical boundary constraints, it is clarified that there are regions, in which the tension field theory is not properly applied.

关键词： finite-element-analysis GENERAL SHELL elementS MIXED INTERPOLATION MEMBRANES

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Sensitivity analysis of large-eddy simulations to subgrid-scale-model parametric uncertainty using polynomial chaos

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JOURNAL OF FLUID MECHANICS 2007年 585卷 255-279页

作者： Lucor, Didier Meyers, Johan Sagaut, Pierre Univ Paris 06 Alembert Inst F-75252 Paris 05 France Katholieke Univ Leuven Dept Mech Engn B-3001 Heverlee Belgium

We address the sensitivity of large-eddy simulations (LES) to parametric uncertainty in the subgrid-scale model. More specifically, we investigate the sensitivity of the LES statistical moments of decaying homogeneous isotropic turbulence to the uncertainty in the Smagorinsky model free parameter C-s (i.e. the Smagorinsky constant). Our sensitivity methodology relies on the non-intrusive approach of the generalized Polynomial Chaos (gPC) method;the gPC is a spectral non-statistical numerical method well-suited to representing random processes not restricted to Gaussian fields. The analysis is carried out at Re-lambda=100 and for different grid resolutions and C-s distributions. Numerical predictions are also compared to direct numerical simulation evidence. We have shown that the different turbulent scales of the LES solution respond differently to the variability in C-s. In particular, the study of the relative turbulent kinetic energy distributions for different C-s distributions indicates that small scales are mainly affected by changes in the subgrid-model parametric uncertainty.

关键词： finite-element-analysis STOCHASTIC DIFFERENTIAL-EQUATIONS WIENER-HERMITE EXPANSION WEIGHTED INTEGRAL METHOD TRANSIENT HEAT-TRANSFER TURBULENT CHANNEL FLOW RESPONSE VARIABILITY PHYSICAL CONSTRAINTS ISOTROPIC TURBULENCE SMAGORINSKY MODEL

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