scholarly journals Mechanical stability of custom-made implants: Numerical study of anatomical device and low elastic Young's modulus alloy

2017 ◽  
Vol 74 ◽  
pp. 399-409 ◽  
Author(s):  
P. Didier ◽  
B. Piotrowski ◽  
M. Fischer ◽  
P. Laheurte
2021 ◽  
Vol 138 (27) ◽  
pp. 50648 ◽  
Author(s):  
Roberto Yáñez‐Macías ◽  
Jorge E. Rivera‐Salinas ◽  
Silvia Solís‐Rosales ◽  
Daniel Orduña‐Altamirano ◽  
David Ruíz‐Mendoza ◽  
...  

2009 ◽  
Vol 9 ◽  
pp. 1382-1393 ◽  
Author(s):  
Jürgen Paletta ◽  
Karla Erffmeier ◽  
Christina Theisen ◽  
Daniel Hussain ◽  
Joachim H. Wendorff ◽  
...  

The aim of this study was to characterize the influence of functionalization of synthetic poly-(L-lactic acid) (PLLA) nanofibers on mechanical properties such as maximum load, elongation, and Young's modulus. Furthermore, the impact of osteoblast growth on the various nanofiber scaffolds stability was determined. Nanofiber matrices composed of PLLA, PLLA-collagen, or BMP-2–incorporated PLLA were produced from different solvents by electrospinning. Standardized test samples of each nanofiber scaffold were subjected to failure protocol before or after incubation in the presence of osteoblasts over a period of 22 days under osteoinductive conditions. PLLA nanofibers electrospun from hexafluoroisopropanol (HFIP) showed a higher strain and tended to have increased maximum loads and Young's modulus compared to PLLA fibers spun from dichloromethane. In addition, they had a higher resistance during incubation in the presence of cells. Functionalization by incorporation of growth factors increased Young's modulus, independent of the solvent used. However, the incorporation of growth factors using the HFIP system resulted in a loss of strain. Similar results were observed when PLLA was blended with different ratios of collagen. Summarizing the results, this study indicates that different functionalization strategies influence the mechanical stability of PLLA nanofibers. Therefore, an optimization of nanofibers should not only account for the optimization of biological effects on cells, but also has to consider the stability of the scaffold.


2019 ◽  
Vol 17 (08) ◽  
pp. 1950054
Author(s):  
Tittu Varghese Mathew ◽  
Lars Beex ◽  
Stéphane PA Bordas ◽  
Sundararajan Natarajan

In this paper, the cell-based smoothed finite element method is extended to solve stochastic partial differential equations with uncertain input parameters. The spatial field of Young’s Modulus and the corresponding stochastic results are represented by Karhunen-Loéve expansion and polynomial chaos expansion, respectively. Young’s Modulus of structure is considered to be random for stochastic static as well as free vibration problems. Mathematical expressions and the solution procedure are articulated in detail to evaluate the statistical characteristics of responses in terms of the static displacements and the free vibration frequencies. The feasibility and the effectiveness of the proposed SGCS–FEM method in terms of accuracy and lower demand on the mesh size in the solution domain over that of conventional FEM for stochastic problems are demonstrated by carefully chosen numerical examples. From the numerical study, it is inferred that the proposed framework yields accurate results.


Holzforschung ◽  
2009 ◽  
Vol 63 (1) ◽  
Author(s):  
Falk Liebner ◽  
Emmerich Haimer ◽  
Antje Potthast ◽  
Dieter Loidl ◽  
Stefanie Tschegg ◽  
...  

Abstract Ultra-lightweight cellulose aerogels can be obtained in three steps: (1) preparation of a cellulose solution in molten N-methylmorpholine-N-oxide monohydrate (NMMO·H2O) at 110–120°C and casting of the viscous mass into moulds; (2) extraction of the solidified castings with ethanol to initiate cellulose aggregation and to remove NMMO·H2O so that the fragile, fine-porous texture of cellulose II is largely retained; and (3) drying of the lyogel using supercritical carbon dioxide (scCO2). According to this approach, cellulosic aerogels were prepared from eight commercial cellulosic materials and pulps and analysed for selected chemical, physicochemical and mechanical parameters. The results reveal that all aerogels obtained from 3% cellulose containing NMMO·H2O melts had a largely uniform mesoporous structure with an average pore size of ∼9–12 nm, surface area of 190–310 m2 g-1, and specific density of 0.046–0.069 g cm-3, but rather low mechanical stability expressed as compressive yield strain of 2.9–5.5%. All samples showed viscoelastic behaviour, with Young's modulus ranging from ∼5 to 10 N mm-2. Doubling the cellulose content in the NMMO·H2O melt from 3% to 6% increased Young's modulus by one order of magnitude. Shrinkage of the fragile cellulose bodies during scCO2 drying was still considerable and is subject to further investigations. Influencing parameters such as scCO2 pressure, cellulose content, regenerating solvent and the number of regenerating baths were optimised.


2009 ◽  
Vol 90A (3) ◽  
pp. 792-803 ◽  
Author(s):  
Nele Stoppie ◽  
Hans Van Oosterwyck ◽  
John Jansen ◽  
Joop Wolke ◽  
Martine Wevers ◽  
...  

2009 ◽  
Vol 628-629 ◽  
pp. 505-510 ◽  
Author(s):  
Yan Qiu Zhang ◽  
S.Y. Jiang ◽  
Y.F. Zheng ◽  
Li Hong Zhao

The influences of four parameters such as young’s modulus, yield ratio, punch radius and blank thickness on the springback of diaphragm of automotive horn are analyzed by combining experiment with FEM (finite element method), and the springback laws of the parameters’ interaction are revealed. The results show that the springback of diaphragm is influenced by the yield ratio of material evidently, but is influenced by punch radius slightly when the parameters interact. However, the influence of punch radius increases greatly when the young’s modulus is very low. Therefore, the influence of the parameters’ interaction must be considered so as to control the springback effectively when the forming scheme of diaphragm is designed.


Metals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1889
Author(s):  
Yuta Kimura ◽  
Takashi Nakamura ◽  
Koji Amezawa ◽  
Keiji Yashiro ◽  
Tatsuya Kawada

Lattice defects significantly affect the mechanical properties of crystalline metal oxides. The materials for the components of solid oxide fuel cells (SOFCs) are no exception, and hence understanding of the interplay between lattice defects and the mechanical properties of components is important to ensure the mechanical stability of SOFCs. Herein, we performed an in situ evaluation of the temperature and P(O2) dependence of the elastic moduli of La2NiO4 (LN214), a candidate for the cathode material of SOFCs, using the resonance method to understand the influence of interstitial oxygen on its elastic properties. Above 873 K, both the Young’s and shear moduli of LN214 slightly decreased with increasing P(O2), suggesting that these elastic moduli are correlated with interstitial oxygen concentration and decreased with increasing interstitial oxygen. We analyzed the influence of interstitial oxygen on the Young’s modulus of LN214, based on numerically obtained lattice energy. The P(O2) dependence of the Young’s modulus of LN214 was found to be essentially explained by variation in the c-lattice constant, which was triggered by variation in interstitial oxygen concentration. These findings may contribute to a better understanding of the relationship between lattice defects and mechanical properties, and to the improvement of the mechanical stability of SOFCs.


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