scholarly journals Buckling Behaviors of Staggered Nanostructure of Biological Materials

2015 ◽  
Vol 83 (3) ◽  
Author(s):  
Zhiling Bai ◽  
Yewang Su ◽  
Baohua Ji
Keyword(s):  
Aspect Ratio ◽  
Mechanical Model ◽  
Volume Fraction ◽  
Biological Materials ◽  
Protein Matrix ◽  
Buckling Strength ◽  
Upper Limits ◽  
Staggered Arrangement ◽  
The Stability ◽  
Peak Value

The nanostructure of biological materials is built with hard mineral crystals embedded in soft protein matrix in a staggered manner. The staggered arrangement of the crystals is assumed to be critically important for the stability of the nanostructure. But the mechanism is not fully understood. In this paper, a mechanical model, considering the effects of overlapping ratio between the crystals, i.e., the staggering position, is developed for analyzing the buckling behaviors of the nanostructure. It is found that the buckling strength increases with the overlapping ratio λ in the range of 0–1/2 and reaches a peak value at λ = 1/2 that is generally adopted by nature's design of the biological materials. The effect of aspect ratio and volume fraction of mineral crystals are further analyzed at various overlapping ratios, and the results are in general consistent with previous studies for the case of λ = 1/2. In addition, the lower and upper limits of the buckling strength are obtained. Finally, we show that the contact between mineral tips can significantly enhance the buckling strength of the nanostructure when the aspect ratio of minerals is small.

Morphological Stability of Ni(Al)/Ni3Al Nanolaminate Composites

1999 ◽  
Vol 581 ◽  
Author(s):  
Jason P. Fain ◽  
Rajarshi Banerjee ◽  
Daniel Josell ◽  
Peter M. Anderson ◽  
Hamish Fraser ◽  
...  
Keyword(s):  
Aspect Ratio ◽  
Layer Thickness ◽  
Crystal Orientation ◽  
Volume Fraction ◽  
Morphological Stability ◽  
Morphological Instability ◽  
Columnar Grains ◽  
Two Phases ◽  
The Stability ◽  
Coherent Interfaces

ABSTRACTThis manuscript discusses the morphological instability observed when multilayered samples with alternating layers of Γ-Ni(Al)/γ-Ni3Al are exposed to 800C for approximately 100 hours. Samples with 20nm/20nm or 120nm/120nm layer thickness and <001> or <Ill> crystal orientation to the interface normal were tested. Pinching off of layers is strongly affected by crystal orientation and layer thickness. Corresponding modeling suggests that the stability of this system is sensitive to fluctuations in the volume fraction of the two phases, the aspect ratio of columnar grains in the layers, and whether coherent or semi-coherent interfaces are present.

scholarly journals Jet Impingement Heat Transfer of Confined Single and Double Jets with Non-Newtonian Power Law Nanofluid under the Inclined Magnetic Field Effects for a Partly Curved Heated Wall

2021 ◽  
Vol 13 (9) ◽  
pp. 5086
Author(s):  
Fatih Selimefendigil ◽  
Hakan F. Oztop ◽  
Ali J. Chamkha
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Particle Size ◽  
Aspect Ratio ◽  
Power Law ◽  
Volume Fraction ◽  
Inclined Magnetic Field ◽  
Magnetic Field Effects ◽  
Power Law Nanofluid ◽  
Power Law Index

Single and double impinging jets heat transfer of non-Newtonian power law nanofluid on a partly curved surface under the inclined magnetic field effects is analyzed with finite element method. The numerical work is performed for various values of Reynolds number (Re, between 100 and 300), Hartmann number (Ha, between 0 and 10), magnetic field inclination (γ, between 0 and 90), curved wall aspect ratio (AR, between 01. and 1.2), power law index (n, between 0.8 and 1.2), nanoparticle volume fraction (ϕ, between 0 and 0.04) and particle size in nm (dp, between 20 and 80). The amount of rise in average Nusselt (Nu) number with Re number depends upon the power law index while the discrepancy between the Newtonian fluid case becomes higher with higher values of power law indices. As compared to case with n = 1, discrepancy in the average Nu number are obtained as −38% and 71.5% for cases with n = 0.8 and n = 1.2. The magnetic field strength and inclination can be used to control the size and number or vortices. As magnetic field is imposed at the higher strength, the average Nu reduces by about 26.6% and 7.5% for single and double jets with n greater than 1 while it increases by about 4.78% and 12.58% with n less than 1. The inclination of magnetic field also plays an important role on the amount of enhancement in the average Nu number for different n values. The aspect ratio of the curved wall affects the flow field slightly while the average Nu variation becomes 5%. Average Nu number increases with higher solid particle volume fraction and with smaller particle size. At the highest particle size, it is increased by about 14%. There is 7% variation in the average Nu number when cases with lowest and highest particle size are compared. Finally, convective heat transfer performance modeling with four inputs and one output is successfully obtained by using Adaptive Neuro-Fuzzy Interface System (ANFIS) which provides fast and accurate prediction results.

scholarly journals Modelling the Molecular Permeation through Mixed-Matrix Membranes Incorporating Tubular Fillers

Membranes ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 58
Author(s):  
Ali Zamani ◽  
F. Handan Tezel ◽  
Jules Thibault
Keyword(s):  
Aspect Ratio ◽  
Relative Permeability ◽  
Polymer Matrix ◽  
Volume Fraction ◽  
Mixed Matrix Membranes ◽  
Analytical Prediction ◽  
Mixed Matrix ◽  
Permeability Ratio ◽  
Filler Volume Fraction ◽  
Matrix Membranes

Membrane-based processes are considered a promising separation method for many chemical and environmental applications such as pervaporation and gas separation. Numerous polymeric membranes have been used for these processes due to their good transport properties, ease of fabrication, and relatively low fabrication cost per unit membrane area. However, these types of membranes are suffering from the trade-off between permeability and selectivity. Mixed-matrix membranes, comprising a filler phase embedded into a polymer matrix, have emerged in an attempt to partly overcome some of the limitations of conventional polymer and inorganic membranes. Among them, membranes incorporating tubular fillers are new nanomaterials having the potential to transcend Robeson’s upper bound. Aligning nanotubes in the host polymer matrix in the permeation direction could lead to a significant improvement in membrane permeability. However, although much effort has been devoted to experimentally evaluating nanotube mixed-matrix membranes, their modelling is mostly based on early theories for mass transport in composite membranes. In this study, the effective permeability of mixed-matrix membranes with tubular fillers was estimated from the steady-state concentration profile within the membrane, calculated by solving the Fick diffusion equation numerically. Using this approach, the effects of various structural parameters, including the tubular filler volume fraction, orientation, length-to-diameter aspect ratio, and permeability ratio were assessed. Enhanced relative permeability was obtained with vertically aligned nanotubes. The relative permeability increased with the filler-polymer permeability ratio, filler volume fraction, and the length-to-diameter aspect ratio. For water-butanol separation, mixed-matrix membranes using polydimethylsiloxane with nanotubes did not lead to performance enhancement in terms of permeability and selectivity. The results were then compared with analytical prediction models such as the Maxwell, Hamilton-Crosser and Kang-Jones-Nair (KJN) models. Overall, this work presents a useful tool for understanding and designing mixed-matrix membranes with tubular fillers.

scholarly journals A Micro-mechanical Investigation of Empirical Models for the Effective Properties of Aligned Short-Fibre Composites

1995 ◽  
Vol 4 (1) ◽  
pp. 096369359500400
Author(s):  
T.D. Papathanasiou
Keyword(s):  
Aspect Ratio ◽  
Volume Fraction ◽  
Tensile Modulus ◽  
Fibre Volume ◽  
Short Fibre ◽  
Computational Results ◽  
Volume Fractions ◽  
Fibre Composites ◽  
Effective Tensile Modulus ◽  
Fibre Aspect Ratio

The predictions of the Halpin equation concerning the effect of fibre volume fraction and fibre aspect ratio on the effective tensile modulus of uniaxially aligned short-fibre composites are compared with computational experiments on three-dimensional, multiparticle composite samples. The method of boundary elements is used to model the mechanical behaviour of composite specimens consisting of up to 40 discrete aligned fibres randomly dispersed in an elastic matrix. Statistical averages of computational results relating the effective tensile modulus to the aspect ratio and volume fraction of the fibres are found to agree very well with the predictions of the Halpin equation for fibre aspect ratio up to 10 and fibre volume fractions up to 20%. Computational results seem to indicate that the predictions of the Halpin equation fall bellow those of micro-mechanical models at higher volume fractions.

The Experimental Analysis on the Regularity of Heating Load in Buildings Using Heat Meters with On-Off Time and Area Method in Shijiazhuang Area

2014 ◽  
Vol 694 ◽  
pp. 272-275
Author(s):  
Chao Wang ◽  
Chun Hua Sun ◽  
Cheng Ying Qi ◽  
Feng Yun Jin ◽  
Bo Shao
Keyword(s):  
Load Distribution ◽  
Distribution Curve ◽  
Heating System ◽  
Measuring Method ◽  
Heating Period ◽  
Heating Load ◽  
The Stability ◽  
Heating Loads ◽  
Off Time ◽  
Peak Value

Based on the heating load experiment adopting on-off time and area measuring method of typical heat users located in different places of different buildings in Shijiazhuang, the heating loads of the heat users which are summarized as two typical heat using modes are studied in this paper and the heating loads in the whole winter heating season of the building is estimated. The results shows that with the user’s heat adopting ratio in these two modes increases, the corresponding heating load is lower, the heating load distribution curve gets smoothly in the whole heating period and the peak value of the system heating loads reduces. This regularity of heating load distribution is beneficial for enhancing the stability of heating system and the thermal efficiency of the heat source.

Investigation of sustainability of lubricated journal bearing under relevant design parameters

2018 ◽  
Vol 70 (4) ◽  
pp. 789-804 ◽  
Author(s):  
M.M. Shahin ◽  
Mohammad Asaduzzaman Chowdhury ◽  
Md. Arefin Kowser ◽  
Uttam Kumar Debnath ◽  
M.H. Monir
Keyword(s):  
Aspect Ratio ◽  
Elastic Strain ◽  
Journal Bearing ◽  
Design Parameters ◽  
Content Type ◽  
Computational Fluid Dynamics Cfd ◽  
Stress Formation ◽  
Bearing Design ◽  
The Stability ◽  
Bearing Friction

Purpose The purposes of the present study are to ensure higher sustainability of journal bearings under different applied loads and to observe bearing performances such as elastic strain, total deformation and stress formation. Design/methodology/approach A journal bearing test rig was used to determine the effect of the applied load on the bearing friction, film thickness, lubricant film pressure, etc. A steady-state analysis was performed to obtain the bearing performance. Findings An efficient aspect ratio (L/D) range was obtained to increase the durability or the stability of the bearing while the bearing is in the working condition by using SAE 5W-30 oil. The results from the study were compared with previous studies in which different types of oil and water, such as Newtonian fluid (NF), magnetorheological fluid (MRF) and nonmagnetorheological fluid (NMRF), were used as the lubricant. To ensure a preferable aspect ratio range (0.25-0.50), a computational fluid dynamics (CFD) analysis was conducted by ANSYS; the results show a lower elastic strain and deformation within the preferable aspect ratio (0.25-0.50) rather than a higher aspect ratio using the SAE 5W-30 oil. Originality/value It is expected that the findings of this study will contribute to the improvement of the bearing design and the bearing lubricating system.

Research on pressure fluctuation phenomenon using the smart isolation tool in subsea pipeline maintenance operation

2018 ◽  
Vol 233 (2) ◽  
pp. 643-652 ◽  
Author(s):  
Kang Zhang ◽  
Qingxin Ding ◽  
Shuhai Liu ◽  
Shimin Zhang ◽  
Xiaoxiao Zhu
Keyword(s):  
Aspect Ratio ◽  
Flow Velocity ◽  
Pressure Fluctuation ◽  
Subsea Pipeline ◽  
Control Precision ◽  
Time Flow ◽  
Fluctuation Phenomenon ◽  
Accurate Position ◽  
Peak Value ◽  
Deceleration Time

A new isolation technology in subsea pipeline maintenance has been gradually developed in recent years. During the operation, the smart isolation tool is desired to decelerate and stop in the accurate position, which will cause a pressure surge in pipe, it was named “pressure fluctuation phenomenon” in this article. For control precision and sealing reliability, avoiding or reducing the fluctuation phenomenon has been necessary. The characteristics of this phenomenon and the effects of parameters have been investigated using numerical methodologies. The results indicated that this phenomenon mainly affected by deceleration time, flow velocity and aspect ratio, and the optimal parameters are t = 1.5 s, v = 1 m/s and γ = 1.2, respectively. The identical results could be achieved from the sensitivity analysis. It can be concluded that the peak value is more sensitive to deceleration time, less sensitive to flow velocity and least sensitive to aspect ratio. All the studies in this article will provide a reference to improve the control precision and seal reliability using smart isolation tool in subsea pipeline maintenance.

scholarly journals Development and Motion Testing of a Robotic Ray

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
Jianhui He ◽  
Yonghua Zhang
Keyword(s):  
Aspect Ratio ◽  
Morphological Parameters ◽  
Kinematic Parameters ◽  
Motion Patterns ◽  
Pectoral Fins ◽  
Fin Ray ◽  
The Stability ◽  
And Control ◽  
Undulating Fin ◽  
Fin Shape

Biomimetics takes nature as a model for inspiration to immensely help abstract new principles and ideas to develop various devices for real applications. In order to improve the stability and maneuvering of biomimetic fish like underwater propulsors, we selected bluespotted ray that propel themselves by taking advantage of their pectoral fins as target. First, a biomimetic robotic undulating fin driven propulsor was built based on the simplified pectoral structure of living bluespotted ray. The mechanical structure and control circuit were then presented. The fin undulating motion patterns, fin ray angle, and fin shape to be investigated are briefly introduced. Later, the kinematic analysis of fin ray and the whole fin is discussed. The influence of various kinematic parameters and morphological parameters on the average propulsion velocity of the propulsor was analyzed. Finally, we conclude that the average propulsion velocity generally increases with the increase of kinematic parameters such as frequency, amplitude, and wavelength, respectively. Moreover, it also has a certain relationship with fin undulating motion patterns, fin ray angle, fin shape, and fin aspect ratio.

scholarly journals Aeroelastic Behavior of Low Aspect Ratio Metal and Composite Blades

1986 ◽  
Author(s):  
James F. White ◽  
Oddvar O. Bendiksen
Keyword(s):  
Aspect Ratio ◽  
Opposite Effect ◽  
Design Parameters ◽  
Aeroelastic Stability ◽  
Low Aspect Ratio ◽  
Supersonic Flutter ◽  
Type Mode ◽  
The Stability ◽  
Composite Blades ◽  
Plate Type

The aeroelastic stability of titanium and composite blades of low aspect ratio is examined over a range of design parameters, using a Rayleigh-Ritz formulation. The blade modes include a plate-type mode to account for chordwise bending. Chordwise flexibility is found to have a significant effect on the unstalled supersonic flutter of low aspect ratio blades, and also on the stability of tip sections of shrouded fan blades. For blades with a thickness of less than approximately four percent of chord, the chordwise, second bending, and first torsion branches are all unstable at moderately high supersonic Mach numbers. For composite blades, the important structural coupling between bending and torsion cannot be modeled properly unless chordwise bending is accounted for. Typically, aft fiber sweep produces beneficial bending-torsion coupling that is stabilizing, whereas forward fiber sweep has the opposite effect. By using crossed-ply laminate configurations, critical aeroelastic modes can be stabilized.

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