scholarly journals Buckling of a soap film spanning a flexible loop resistant to bending and twisting

2014 ◽  
Vol 470 (2172) ◽  
pp. 20140368 ◽  
Author(s):  
Aisa Biria ◽  
Eliot Fried
Keyword(s):  
Torsional Rigidity ◽  
Soap Film ◽  
Plateau Problem ◽  
Bending Rigidity ◽  
Energy Contribution ◽  
Lagrange Equations ◽  
Buckling Modes ◽  
Flexible Loop ◽  
A Value ◽  
The Stability

A generalization of the Euler–Plateau problem to account for the energy contribution due to twisting of the bounding loop is proposed. Euler–Lagrange equations are derived in a parametrized setting and a buckling analysis is performed. A pair of dimensionless parameters govern buckling from a flat, circular ground state. While one of these is familiar from the Euler–Plateau problem, the other encompasses information about the ratio of the torsional rigidity to the bending rigidity, the twist density and the size of the loop. For sufficiently small values of the latter parameter, two separate groups of buckling modes are identified. However, for values of that parameter exceeding the critical twist density arising in Michell's study of the stability of a twisted elastic ring, only one group of buckling modes exists. Buckling diagrams indicate that a loop with greater torsional rigidity shows more resistance to transverse buckling. Additionally, a twisted flexible loop spanned by a soap film buckles at a value of the twist density less that the value at which buckling would occur if the soap film were absent.

Influence of a spanning liquid film on the stability and buckling of a circular loop with intrinsic curvature or intrinsic twist density

2016 ◽  
Vol 23 (1) ◽  
pp. 43-66 ◽  
Author(s):  
Tuan Hoang ◽  
Eliot Fried
Keyword(s):  
Surface Tension ◽  
Liquid Film ◽  
Flexural Rigidity ◽  
Torsional Rigidity ◽  
Stable Solution ◽  
Variational Model ◽  
Intrinsic Curvature ◽  
Buckling Modes ◽  
Out Of Plane ◽  
The Stability

A variational model is used to study the behavior of a flexible but inextensible loop spanned by a liquid film, with the objective of explaining the stability and buckling of flat circular configurations. Loops made from filaments with intrinsic curvature and/or intrinsic twist density are considered, but attention is restricted to filaments with circular cross sections and uniform mechanical properties. Loops made with intrinsic curvature but no intrinsic twist density exhibit in-plane and out-of-plane buckling modes corresponding to stable solution branches that bifurcate from the branch of flat circular solutions and out-of-plane buckling occurs at a lower value of the dimensionless surface tension of the liquid film than does in-plane buckling. Additionally, however, the destabilizing influence of the intrinsic curvature can be countered by increasing the torsional rigidity relative to the flexural rigidity. For a loop with both intrinsic curvature and intrinsic twist density, only one branch of stable solutions bifurcates from the flat circular solution branch, the in-plane and out-of-plane buckling modes are intertwined, and bifurcation occurs at a value of the dimensionless surface tension less than that governing the behavior of loops made from filaments that are intrinsically rectilinear. Moreover, increasing the torsional rigidity relative to the flexural rigidity has no or little stabilizing effect if the loop is either too short or too long and, in contrast to what occurs for loops with only intrinsic curvature, if the intrinsic twist density is sufficiently large then the destabilizing influence of the intrinsic curvature cannot be countered by increasing the torsional rigidity relative to the flexural rigidity, regardless of the length of the loop.

scholarly journals Regional Coordination and Security of Water–Energy–Food Symbiosis in Northeastern China

2021 ◽  
Vol 13 (3) ◽  
pp. 1326
Author(s):  
Hongfang Li ◽  
Huixiao Wang ◽  
Yaxue Yang ◽  
Ruxin Zhao
Keyword(s):  
External Environment ◽  
Northeastern China ◽  
Decision Makers ◽  
Human Survival ◽  
A Value ◽  
Natural Factors ◽  
Regional Coordination ◽  
Micro Level ◽  
The Stability ◽  
Coordination Degree

The interactions of water, energy, and food, which are essential resources for human survival, livelihoods, production, and development, constitute a water–energy–food (WEF) nexus. Applying symbiosis theory, the economic, social, and natural factors were considered at the same time in the WEF system, and we conducted a micro-level investigation focusing on the stability, coordination, and sustainability of the symbiotic units (water, energy, and food), and external environment of the WEF system in 36 prefecture-level cities across three northeastern provinces of China. Finally, we analyzed the synergistic safety and coupling coordination degree of the WEF system by the combination of stability, coordination, and sustainability, attending to the coordination relationship and influences of the external environment. The results indicated that the synergistic safety of the WEF system in three northeastern provinces need to equally pay attention to the stability, coordination, and sustainability of the WEF system, since their weights were 0.32, 0.36 and 0.32, respectively. During 2010–2016, the synergistic safety indexes of the WEF system ranged between 0.40 and 0.60, which was a state of boundary safety. In the current study, the coupling coordination degree of the WEF system fluctuated around a value of 0.6, maintaining a primary coordination level; while in the future of 2021–2026, it will decline to 0.57–0.60, dropping to a weak coordinated level. The conclusion could provide effective information for decision-makers to take suitable measures for the security development of a WEF system.

scholarly journals Thermally Stimulated Desorption Optical Fiber-Based Interrogation System: An Analysis of Graphene Oxide Layers’ Stability

Photonics ◽  
2021 ◽  
Vol 8 (3) ◽  
pp. 70
Author(s):  
Maria Raposo ◽  
Carlota Xavier ◽  
Catarina Monteiro ◽  
Susana Silva ◽  
Orlando Frazão ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Optical Fiber ◽  
Optical Fiber Sensor ◽  
Layer By Layer ◽  
Film Stability ◽  
A Value ◽  
Device Reliability ◽  
Sensor Devices ◽  
Lbl Films ◽  
The Stability

Thin graphene oxide (GO) film layers are being widely used as sensing layers in different types of electrical and optical sensor devices. GO layers are particularly popular because of their tuned interface reflectivity. The stability of GO layers is fundamental for sensor device reliability, particularly in complex aqueous environments such as wastewater. In this work, the stability of GO layers in layer-by-layer (LbL) films of polyethyleneimine (PEI) and GO was investigated. The results led to the following conclusions: PEI/GO films grow linearly with the number of bilayers as long as the adsorption time is kept constant; the adsorption kinetics of a GO layer follow the behavior of the adsorption of polyelectrolytes; and the interaction associated with the growth of these films is of the ionic type since the desorption activation energy has a value of 119 ± 17 kJ/mol. Therefore, it is possible to conclude that PEI/GO films are suitable for application in optical fiber sensor devices; most importantly, an optical fiber-based interrogation setup can easily be adapted to investigate in situ desorption via a thermally stimulated process. In addition, it is possible to draw inferences about film stability in solution in a fast, reliable way when compared with the traditional ones.

One-dimensional models of fourth and sixth orders for rods derived from three-dimensional elasticity

2016 ◽  
Vol 22 (2) ◽  
pp. 158-175 ◽  
Author(s):  
Erick Pruchnicki
Keyword(s):  
Order Term ◽  
Three Dimensional ◽  
Transverse Dimension ◽  
Lagrange Equations ◽  
Transverse Shearing ◽  
Natural Boundary Conditions ◽  
The Stability ◽  
Shearing Energy ◽  
Three Dimensional Elasticity ◽  
Double Symmetry

The displacement field in rods can be approximated by using a Taylor–Young expansion in transverse dimension of the rod. These involve that the highest-order term of shear is of second order in the transverse dimension of the rod. Then we show that transverse shearing energy is removed by the fourth-order truncation of the potential energy and so we revisit the model presented by Pruchnicki. Then we consider the sixth-order truncation of the potential which includes transverse shearing and transverse normal stress energies. For these two models we show that the potential energies satisfy the stability condition of Legendre–Hadamard which is necessary for the existence of a minimizer and then we give the Euler–Lagrange equations and the natural boundary conditions associated with these potential energies. For the sake of simplicity we consider that the cross-section of the rod has double symmetry axes.

Effect of operating parameters on functional fatigue characteristics of an Ni-Ti shape memory alloy on partial thermomechanical cycling

2022 ◽  
pp. 1045389X2110722
Author(s):  
Swaminathan Ganesan ◽  
Sampath Vedamanickam
Keyword(s):  
Yield Strength ◽  
Applied Stress ◽  
Stress Level ◽  
Crack Nucleation ◽  
Maximum Temperature ◽  
Thermomechanical Cycling ◽  
Permanent Strain ◽  
A Value ◽  
The Stability ◽  
Cycle Temperature

In this study, the influence of upper cycle temperature (maximum temperature in a cycle) and the magnitude of applied stress on the functional properties of an SMA during partial thermomechanical cycling has been studied. A near-equiatomic NiTi SMA was chosen and tested under different upper cycle temperatures (between martensite finish (Mf) and austenite finish (Af) temperatures) and stress level (below and above the yield strength of the martensite). The upper cycle temperature was varied by controlling the magnitude of the current supply. The results show that a raise in the upper cycle temperature causes the permanent strain to increase and also lowers the stability. However, decreasing the stress imposed to a value lower than the yield strength of the martensite improves cyclic stability. The upper cycle temperature was found to influence the crack nucleation, whereas the applied stress level the crack propagation during partial thermomechanical cycling of SMAs. Therefore, decreasing the upper cycle temperature as well as the magnitude of stress applied to lower than the yield stress of martensite have been found to be suitable strategies for increasing the lifespan of SMA-based actuators during partial thermomechanical cycling.

Analytical and Experimental Flutter Analysis of a Typical Wing Section Carrying a Flexibly Mounted Unbalanced Engine

2019 ◽  
Vol 19 (02) ◽  
pp. 1950013 ◽  
Author(s):  
A. S. Mirabbashi ◽  
A. Mazidi ◽  
M. M. Jalili
Keyword(s):  
Stability Domain ◽  
Governing Equations ◽  
Lagrange Equations ◽  
Wing Section ◽  
Unbalanced Force ◽  
Engine Thrust ◽  
Finite State Model ◽  
Flutter Analysis ◽  
Finite State ◽  
The Stability

In this paper, both experimental and analytical flutter analyses are conducted for a typical 5-degree of freedon (5DOF) wing section carrying a flexibly mounted unbalanced engine. The wing flexibility is simulated by two torsional and longitudinal springs at the wing elastic axis. One flap is attached to the wing section by a torsion spring. Also, the engine is connected to the wing by two elastic joints. Each joint is simulated by a spring and damper unit to bring the model close to reality. Both the torsional and longitudinal motions of the engine are considered in the aeroelastic governing equations derived from the Lagrange equations. Also, Peter’s finite state model is used to simulate the aerodynamic loads on the wing. Effects of various engine parameters such as position, connection stiffness, mass, thrust and unbalanced force on the flutter of the wing are investigated. The results show that the aeroelastic stability region is limited by increasing the engine mass, pylon length, engine thrust and unbalanced force. Furthermore, increasing the damping and stiffness coefficients of the engine connection enlarges the stability domain.

Electrically driven jets

1969 ◽  
Vol 313 (1515) ◽  
pp. 453-475 ◽  
Keyword(s):  
Electric Field ◽  
Soap Film ◽  
Radial Electric Field ◽  
Viscous Fluids ◽  
Critical Fields ◽  
Water Jets ◽  
Viscous Jets ◽  
The Stability ◽  
Stability Of Water ◽  
Long Cylinder

Fine jets of slightly conducting viscous fluids and thicker jets or drops of less viscous ones can be drawn from conducting tubes by electric forces. As the potential of the tube relative to a neighbouring plate rises, viscous fluids become nearly conical and fine jets come from the vertices. The potentials at which these jets or drops first appear was measured and compared with calculations. The stability of viscous jets depends on the geometry of the electrodes. Jets as small as 20 μm in diameter and 5 cm long were produced which were quite steady up to a millimetre from their ends. Attempts to describe them mathematically failed. Their stability seems to be due to mechanical rather than electrical causes, like that of a stretched string, which is straight when pulled but bent when pushed. Experiments on the stability of water jets in a parallel electric field reveal two critical fields, one at which jets that are breaking into drops become steady and another at which these steady jets become unsteady again, without breaking into drops. Experiments are described in which a cylindrical soap film becomes unstable under a radial electric field. The results are compared with calculations by A. B. Basset and after a mistake in his analysis is corrected, agreement is found over the range where experiments are possible. Basset’s calculations for axisymmetrical disturbances are extended to those in which the jet moves laterally. Though this is the form in which the instability appears, calculations about uniform jets do not seem to be relevant. In an appendix M. D. Van Dyke calculates the attraction between a long cylinder and a perpendicular plate at a different potential.

The stability of onoratoite, Sb8O11Cl2, in the supergene environment

2014 ◽  
Vol 78 (7) ◽  
pp. 1671-1675 ◽  
Author(s):  
Adam J. Roper ◽  
Peter Leverett ◽  
Timothy D. Murphy ◽  
Peter A. Williams
Keyword(s):  
Significant Influence ◽  
Secondary Phase ◽  
Low Ph ◽  
Stable Phase ◽  
Supergene Zone ◽  
A Value ◽  
Solubility Studies ◽  
The Stability ◽  
Very High

AbstractSynthesis and solubility studies of onoratoite have been undertaken to determine the role of this rare secondary phase in the immobilization of Sb and the conditions responsible for its formation in the supergene zone. Solubility studies were undertaken at 298.15 K. A value of ΔGfθ (Sb8O11Cl2, s, 298.15 K) = –2576 ±12 kJ mol–1 was derived. Calculations involving sénarmontite, Sb2O3, klebelsbergite, Sb4O4SO4(OH)2 and schafarzikite, FeSb2O4, show that onoratoite is a thermodynamically stable phase only at negligible activities of SO42–(aq) and low activities of Fe2+(aq), at low pH and very high activities of Cl–(aq). This explains why onoratoite is such a rare secondary phase and why it cannot exert any significant influence on the dispersion of Sb in the supergene environment.

The Stability of an Axially–Loaded Continuous Beam

1955 ◽  
Vol 59 (535) ◽  
pp. 506-509
Author(s):  
A. M. Dobson
Keyword(s):  
Axial Load ◽  
Classical Method ◽  
Complete Solution ◽  
Critical Value ◽  
Continuous Beam ◽  
Independent Variables ◽  
A Value ◽  
Method Of Solution ◽  
Axially Loaded ◽  
The Stability

The Classical method of solution of the stability of an axially–loaded continuous beam is by means of the three moments equation, using the Berry Functions, which are functions of the axial load. As the axial load approaches a value equal to the critical value for a pin–jointed beam, the Berry Functions tend to infinity, and the use of the three moments equations —(i. e. treating the end fixing moments as the independent variables)—leads to certain difficulties in the complete solution of the problem.The major difficulty lies in the question of stability. The critical value is determined by the vanishing of the determinant of the coefficients of the fixing moments in the three moments equations. This value could be found by plotting the determinant against end load (c. f. Pippard and Pritchard). However, in a problem involving a large number of bays, the calculation necessary to do this is likely to be considerable, for there may be many branches to the curve.

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