scholarly journals Numerical investigation of stent designs for wireless access to integrated sensors

2019 ◽  
Vol 5 (1) ◽  
pp. 497-499
Author(s):  
Swen Großmann ◽  
Robert Ott ◽  
Richard Kosub ◽  
Klaus-Peter Schmitz ◽  
Stefan Siewert ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Mechanical Performance ◽  
Short Circuit ◽  
Pressure Sensors ◽  
Wireless Access ◽  
Von Mises Stress ◽  
Stent Design ◽  
Resonance Frequencies ◽  
Von Mises

AbstractIn recent years, a progressive interest in the implementation of wireless access to cardiovascular implants has been established. This manifests in new devices, such as arterial pressure sensors, or additional functionalities added to established implants like stents. However, common stent designs, possessing highly optimized mechanical properties, often consist of cylindrically arranged struts with connections in-between which can be considered as short-circuited inductive coils. As a consequence, the small inductance raises the resonance frequency, which may decrease the in vivo performance of the wireless connection between the stent and the external readout device. Thus, new designs were developed to overcome this limitation, for example by avoiding the short-circuit due to a helical arrangement of the struts. Within this work we compare the performance of a common stent design and a helical design by means of numerical simulations. We are using two designs which only differ in the arrangement of the struts. The electromagnetic and mechanical properties are investigated using a finitedifference time-domain algorithm and finite element method, respectively. We will show that a common stent design exhibits resonance frequencies in the gigahertz regime, much higher than the frequencies of comparable helical designs. Furthermore, we compare the mechanical performance of the two designs and reveal individual distinctions in the radial stiffness, bending stiffness, and the von Mises stress.

scholarly journals Mechanical Characterisation and Biomechanical and Biological Behaviours of Ti-Zr Binary-Alloy Dental Implants

2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
Aritza Brizuela-Velasco ◽  
Esteban Pérez-Pevida ◽  
Antonio Jiménez-Garrudo ◽  
Francisco Javier Gil-Mur ◽  
José María Manero ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Dental Implants ◽  
Binary Alloy ◽  
Von Mises Stress ◽  
Element Analysis ◽  
Poisson Coefficient ◽  
Mechanical Characterisation ◽  
Bone Level ◽  
Von Mises

The objective of the study is to characterise the mechanical properties of Ti-15Zr binary alloy dental implants and to describe their biomechanical behaviour as well as their osseointegration capacity compared with the conventional Ti-6Al-4V (TAV) alloy implants. The mechanical properties of Ti-15Zr binary alloy were characterised using Roxolid© implants (Straumann, Basel, Switzerland) via ultrasound. Their biomechanical behaviour was described via finite element analysis. Their osseointegration capacity was compared via an in vivo study performed on 12 adult rabbits. Young’s modulus of the Roxolid© implant was around 103 GPa, and the Poisson coefficient was around 0.33. There were no significant differences in terms of Von Mises stress values at the implant and bone level between both alloys. Regarding deformation, the highest value was observed for Ti-15Zr implant, and the lowest value was observed for the cortical bone surrounding TAV implant, with no deformation differences at the bone level between both alloys. Histological analysis of the implants inserted in rabbits demonstrated higher BIC percentage for Ti-15Zr implants at 3 and 6 weeks. Ti-15Zr alloy showed elastic properties and biomechanical behaviours similar to TAV alloy, although Ti-15Zr implant had a greater BIC percentage after 3 and 6 weeks of osseointegration.

Study on Mechanical Properties for Modeling and Simulation of Microneedles for Medical Applications

2013 ◽  
Vol 454 ◽  
pp. 86-89 ◽  
Author(s):  
Yan Li ◽  
Pei Yu Zhang
Keyword(s):  
Mechanical Properties ◽  
Von Mises Stress ◽  
Medical Applications ◽  
Microneedle Array ◽  
Nonlinear Buckling ◽  
Needle Structure ◽  
Linear And Nonlinear ◽  
Von Mises ◽  
Fluid Sampling

A MEMS Microneedle Array was modeled, designed and simulated. The mechanical properties of the microneedle structure were theoretically analyzed including analysis of fracture strength and distribution of von mises stress. The conditions of initial insertion and after initial insertion were considered. The detail linear and nonlinear buckling analyses on needle structure were also presented. Two modes of buckling were come to and discussed. The fabrication of microneedle array was simulated by employing Intellisuate and bi-mask technique. The microneedle array can be used in microsystem for in-vivo fluid sampling and drug delivery.

scholarly journals Mechanical Strength Study of a Cranial Implant Using Computational Tools

2022 ◽  
Vol 12 (2) ◽  
pp. 878
Author(s):  
Pedro O. Santos ◽  
Gustavo P. Carmo ◽  
Ricardo J. Alves de Sousa ◽  
Fábio A. O. Fernandes ◽  
Mariusz Ptak
Keyword(s):  
Structural Integrity ◽  
Mechanical Performance ◽  
Skull Fracture ◽  
Human Head ◽  
Element Model ◽  
Von Mises Stress ◽  
Cranial Implant ◽  
Von Mises ◽  
Two Parameters ◽  
The Brain

The human head is sometimes subjected to impact loads that lead to skull fracture or other injuries that require the removal of part of the skull, which is called craniectomy. Consequently, the removed portion is replaced using autologous bone or alloplastic material. The aim of this work is to develop a cranial implant to fulfil a defect created on the skull and then study its mechanical performance by integrating it on a human head finite element model. The material chosen for the implant was PEEK, a thermoplastic polymer that has been recently used in cranioplasty. A6 numerical model head coupled with an implant was subjected to analysis to evaluate two parameters: the number of fixation screws that enhance the performance and ensure the structural integrity of the implant, and the implant’s capacity to protect the brain compared to the integral skull. The main findings point to the fact that, among all tested configurations of screws, the model with eight screws presents better performance when considering the von Mises stress field and the displacement field on the interface between the implant and the skull. Additionally, under the specific analyzed conditions, it is observable that the model with the implant offers more efficient brain protection when compared with the model with the integral skull.

High-Resolution Three-Dimensional-pQCT Images Can Be an Adequate Basis for In-Vivo μFE Analysis of Bone

2000 ◽  
Vol 123 (2) ◽  
pp. 176-183 ◽  
Author(s):  
W. Pistoia ◽  
B. van Rietbergen ◽  
A. Laib ◽  
P. Ru¨egsegger
Keyword(s):  
High Resolution ◽  
Trabecular Bone ◽  
Elastic Properties ◽  
Bone Structure ◽  
Reference Model ◽  
Von Mises Stress ◽  
Micro Ct ◽  
Von Mises

Micro-finite element (μFE) models based on high-resolution images have enabled the calculation of elastic properties of trabecular bone in vitro. Recently, techniques have been developed to image trabecular bone structure in vivo, albeit at a lesser resolution. The present work studies the usefulness of such in-vivo images for μFE analyses, by comparing their μFE results to those of models based on high-resolution micro-CT (μCT) images. Fifteen specimens obtained from human femoral heads were imaged first with a 3D-pQCT scanner at 165 μm resolution and a second time with a μCT scanner at 56 μm resolution. A third set of images with a resolution of 165 μm was created by downscaling the μCT measurements. The μFE models were created directly from these images. Orthotropic elastic properties and the average tissue von Mises stress of the specimens were calculated from six FE-analyses per specimen. The results of the 165 μm models were compared to those of the 56 μm model, which was taken as the reference model. The results calculated from the pQCT-based models, correlated excellent with those calculated from the reference model for both moduli R2>0.95 and for the average tissue von Mises stress R2>0.83. Results calculated from the downscaled micro-CT models correlated even better with those of the reference models (R2>0.99 for the moduli and R2>0.96 for the average von Mises stress). In the case of the 3D-pQCT based models, however, the slopes of the regression lines were less than one and had to be corrected. The prediction of the Poisson’s ratios was less accurate (R2>0.45 and R2>0.67) for the models based on 3D-pQCT and downscaled μCT images respectively). The fact that the results from the downscaled and original μCT images were nearly identical indicates that the need for a correction in the case of the 3D-pQCT measurements was not due to the voxel size of the images but due to a higher noise level and a lower contrast in these images, in combination with the application of a filtering procedure at 165 micron images. In summary: the results of μFE models based on in-vivo images of the 3D-pQCT can closely resemble those obtained from μFE models based on higher resolution μCT system.

scholarly journals Finite Element Analysis of Schwarz P Surface Pore Geometries for Tissue-Engineered Scaffolds

2012 ◽  
Vol 2012 ◽  
pp. 1-13 ◽  
Author(s):  
Jaemin Shin ◽  
Sungki Kim ◽  
Darae Jeong ◽  
Hyun Geun Lee ◽  
Dongsun Lee ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Phase Field ◽  
Field Model ◽  
Phase Field Model ◽  
Volume Ratio ◽  
Von Mises Stress ◽  
High Porosity ◽  
Tissue Engineering Scaffolds ◽  
Element Analysis ◽  
Von Mises

Tissue engineering scaffolds provide temporary mechanical support for tissue regeneration. To regenerate tissues more efficiently, an ideal structure of scaffolds should have appropriate porosity and pore structure. In this paper, we generate the Schwarz primitive (P) surface with various volume fractions using a phase-field model. The phase-field model enables us to design various surface-to-volume ratio structures with high porosity and mechanical properties. Comparing the Schwarz P surface's von Mises stress with that of triply periodic cylinders and cubes, we draw conclusions about the mechanical properties of the Schwarz P surface.

The effect of Trichinella spiralis infection on the mechanical properties of the mammalian diaphragm

Parasitology ◽  
1996 ◽  
Vol 113 (6) ◽  
pp. 535-543 ◽  
Author(s):  
C. L. Harwood ◽  
I. S. Young ◽  
D. L. Lee ◽  
J. D. Altringham
Keyword(s):  
Mechanical Properties ◽  
Fatigue Resistance ◽  
Power Output ◽  
Mechanical Performance ◽  
Trichinella Spiralis ◽  
Muscle Cells ◽  
Duration Of Infection ◽  
Secretory Products ◽  
Stress Work

SUMMARYTrichinella spiralis larvae infect and develop within skeletal muscle cells causing major changes to their mechanical properties. The aim of this investigation was to determine the effects of T. spiralis on the power output and fatigue resistance of the mammalian diaphragm under conditions simulating in vivo operation and to relate these to respiratory performance. Infection with T. spiralis leads to major reductions in mechanical stress, work, power output and fatigue resistance. These changes are associated with the number of larvae present in the muscle and the duration of infection. However, the initial decline in mechanical performance occurs during the onset of infection when there are few larvae observed within the muscle cells, indicating that T. spiralis may affect the properties of muscle before encapsulation. This may correspond to the host's inflammatory response and the effects of larval excretory/secretory products. The decline in mechanical performance will have a profound effect on respiration both at rest and during exertion. This must influence the behaviour of the host and increase its chance of capture by predators, which is likely to benefit the parasite by facilitating its transmission.

scholarly journals Electrospun polyester-urethane scaffold preserves mechanical properties and exhibits strain stiffening during in situ tissue ingrowth and degradation

2019 ◽  
Author(s):  
Hugo Krynauw ◽  
Rodaina Omar ◽  
Josepha Koehne ◽  
Georges Limbert ◽  
Neil H Davies ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Mechanical Performance ◽  
Hydrolytic Degradation ◽  
Material Strength ◽  
Fibre Direction ◽  
Tissue Ingrowth ◽  
Polyester Urethane

AbstractConsistent mechanical performance from implantation through healing and scaffold degradation is highly desired for tissue-regenerative scaffolds, e.g. when used for vascular grafts. The aim of this study was the paired in vivo mechanical assessment of biostable and fast degrading electrospun polyester-urethane scaffolds to isolate the effects of material degradation and tissue formation after implantation. Biostable and degradable polyester-urethane scaffolds with substantial fibre alignment were manufactured by electrospinning. Scaffold samples were implanted paired in subcutaneous position in rats for 7, 14 and 28 days. Morphology, mechanical properties and tissue ingrowth of the scaffolds were assessed before implantation and after retrieval. Tissue ingrowth after 28 days was 83 ± 10% in the biostable scaffold and 77 ± 4% in the degradable scaffold. For the biostable scaffold, the elastic modulus at 12% strain increased significantly between 7 and 14 days and decreased significantly thereafter in fibre but not in cross-fibre direction. The degradable scaffold exhibited a significant increase in the elastic modulus at 12% strain from 7 to 14 days after which it did not decrease but remained at the same magnitude, both in fibre and in cross-fibre direction. Considering that the degradable scaffold loses its material strength predominantly during the first 14 days of hydrolytic degradation (as observed in our previous in vitro study), the consistency of the elastic modulus of the degradable scaffold after 14 days is an indication that the regenerated tissue construct retains it mechanical properties.

Numerical Investigations of the Long Blade Performance Using RANS Solution and FEA Method Coupled With One-Way and Two-Way Fluid-Structure Interaction Models

2017 ◽  
Author(s):  
Minyan Yin ◽  
Jun Li ◽  
Liming Song ◽  
Zhenping Feng
Keyword(s):  
Rotor Blade ◽  
Mechanical Performance ◽  
Fluid Structure Interaction ◽  
Interaction Model ◽  
Leading Edge ◽  
Von Mises Stress ◽  
Maximum Displacement ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Von Mises

The aerodynamic and mechanical performance of the last stage was numerically investigated using three-dimensional Reynolds-Averaged Navier-Stokes (RANS) solution and Finite Element Analysis (FEA) coupled with the one-way and two-way fluid-structure interaction models in this work. The part-span damping snubber and tip damping shroud of the rotor blade and aerodynamic pressure on rotor blade mechanical performance was considered in the one-way model. The two-way fluid-structure interaction model coupled with the mesh deformation technology was conducted to analyze the aerodynamic and mechanical performance of the last stage rotor blade. One-way fluid-structure interaction model numerical results show that the location of nodal maximum displacement moves from leading edge of 85% blade span to the trailing edge of 85% blade span. The position of nodal maximum Von Mises stress is still located at the first tooth upper surface near the leading edge at the blade root of pressure side. The two-way fluid-structure interaction model results show that the variation of static pressure distribution on long blade surface is mostly concentrated at upper region, absolute outflow angle of long blade between the 40% span and 95% span reduces, the location of nodal maximum displacement appears at the trailing edge of 85% blade span. Furthermore, the position of nodal maximum Von Mises stress remains the same and the value decreases compared to the oneway fluid-structure model results.

Dynamic Analysis of Three Types of Bioprosthetic Heart Valves

2011 ◽  
Vol 71-78 ◽  
pp. 2683-2688
Author(s):  
Xin Ye ◽  
Quan Yuan ◽  
Hua Cong ◽  
Hai Bo Ma ◽  
Dong Liang Wei
Keyword(s):  
Stress Distribution ◽  
Heart Valve ◽  
Computer Aided Design ◽  
Heart Valves ◽  
Mechanical Performance ◽  
Bioprosthetic Valve ◽  
Von Mises Stress ◽  
Element Analysis ◽  
Diastolic Phase ◽  
Von Mises

This paper constructs three types of bioprosthetic valve leaflets’ parametric model via computer aided design, a series of accurate parameters of the bioproshtetic heart valve, such as radius of the sutural ring, height of the supporting stent and inclination of the supporting stent, are determined. Numerical simulation is used to determine the effect of different shape designs on the mechanical performance of the bioprosthetic valve leaflet. The dynamic behavior of the valve during diastolic phase is analyzed. The finite element analysis results show the stress distribution of the ellipsoidal and spherical valve leaflets are comparatively reasonable. The ellipsoidal and spherical valve leaflets have the following advantages over the cylindrical leaflet valve, lower peak von-Mises stress, smaller stress concentration area, and relatively uniform stress distribution. The ellipsoidal and spherical valve leaflets may contribute to the long term durability of the valve. This work is very helpful to manufacture valvular leaflets with reasonable shapes and to prolong the lifetime of the bioprosthetic heart valve.

scholarly journals Multi-layered bird beaks: a finite-element approach towards the role of keratin in stress dissipation

2012 ◽  
Vol 9 (73) ◽  
pp. 1787-1796 ◽  
Author(s):  
Joris Soons ◽  
Anthony Herrel ◽  
Annelies Genbrugge ◽  
Dominique Adriaens ◽  
Peter Aerts ◽  
...  
Keyword(s):  
Finite Element ◽  
Material Properties ◽  
Speckle Pattern ◽  
Young Modulus ◽  
Von Mises Stress ◽  
Fe Model ◽  
Element Approach ◽  
Von Mises ◽  
The Impact

Bird beaks are layered structures, which contain a bony core and an outer keratin layer. The elastic moduli of this bone and keratin were obtained in a previous study. However, the mechanical role and interaction of both materials in stress dissipation during seed crushing remain unknown. In this paper, a multi-layered finite-element (FE) model of the Java finch's upper beak ( Padda oryzivora ) is established. Validation measurements are conducted using in vivo bite forces and by comparing the displacements with those obtained by digital speckle pattern interferometry. Next, the Young modulus of bone and keratin in this FE model was optimized in order to obtain the smallest peak von Mises stress in the upper beak. To do so, we created a surrogate model, which also allows us to study the impact of changing material properties of both tissues on the peak stresses. The theoretically best values for both moduli in the Java finch are retrieved and correspond well with previous experimentally obtained values, suggesting that material properties are tuned to the mechanical demands imposed during seed crushing.

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