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Search for "shear" in Full Text gives 182 result(s) in Beilstein Journal of Nanotechnology.
Physical principles of fluid-mediated insect attachment - Shouldn’t insects slip?
Beilstein J. Nanotechnol. 2014, 5, 1160–1166, doi:10.3762/bjnano.5.127
- mm2 [16], the maximal possible shear stress before sliding occurs (with cos α1 − cos α2 ≤ 2) would be only approx. 0.38 kPa. This value (and the corresponding value for smaller contact areas) is several orders of magnitude smaller than the shear stresses measured in smooth adhesive pads of the stick
- generated by a continuous fluid film of 90 nm height would be one order of magnitude smaller than the shear stresses observed in adhesive organs [30]. Thus it is not yet clear how insects with a fluid-mediated adhesive pad generate the observed friction forces preventing them from sliding down smooth
- results suggest that thixotropic (shear-thinning) non-Newtonian properties of the secretion could explain the presence of high static friction forces [46][60]. A second, yet to be tested, hypothesis to explain the observed high friction forces is the formation of local “dry” rubber like direct contacts
A nanometric cushion for enhancing scratch and wear resistance of hard films
Beilstein J. Nanotechnol. 2014, 5, 1005–1015, doi:10.3762/bjnano.5.114
- images of the tip used for the experiments. The simulation was executed by MSC.MARC FE code, and used a bilinear shear, Coulomb model for the friction. Contact conditions are defined only between the indenter tip and the TiO2 layer. During the simulation, the indenter is first pressed against the layer
Direct observation of microcavitation in underwater adhesion of mushroom-shaped adhesive microstructure
Beilstein J. Nanotechnol. 2014, 5, 903–909, doi:10.3762/bjnano.5.103
- -shaped contact geometry (see review [4]), which have been studied intensively under various loads (e.g., preload [5][6], shear [7][8], overload [9], and tilt [10][11]) and environmental conditions (e.g., dry in air [5][6][7][8][9][10][11][12], oil lubricated [13], on rough substrates [13][14][15], in
Fibrillar adhesion with no clusterisation: Functional significance of material gradient along adhesive setae of insects
Beilstein J. Nanotechnol. 2014, 5, 837–845, doi:10.3762/bjnano.5.95
- multiple contacts that contribute to an enhancement of overall length of the total peeling line [7]. We have recently shown that thin tape-like contact tips of hairs (setae) in combination with applied shear force lead to the formation of maximal real contact area without slippage within the contact [8
Scale effects of nanomechanical properties and deformation behavior of Au nanoparticle and thin film using depth sensing nanoindentation
Beilstein J. Nanotechnol. 2014, 5, 822–836, doi:10.3762/bjnano.5.94
- dependent on the indenter shape, the shear modulus and H0. The ISE contributes to increased hardness in bulk solid surfaces, thin films and nano-objects. Hall–Petch effect The generation of dislocations leads to the Hall–Petch effect through the dislocation pile up mechanism or the dislocation density
The optimal shape of elastomer mushroom-like fibers for high and robust adhesion
Beilstein J. Nanotechnol. 2014, 5, 630–638, doi:10.3762/bjnano.5.74
- these results are important for designing dry fibrillar adhesives, they are only concerned with the performance when the loading is axial. The effect of shear loading should also be considered along with the results of this study in designing fibrillar adhesives. Scanning electron microscope image of
Hairy suckers: the surface microstructure and its possible functional significance in the Octopus vulgaris sucker
Beilstein J. Nanotechnol. 2014, 5, 561–565, doi:10.3762/bjnano.5.66
- adhesion conditions, a system consisting of hairs, mucus, and water (just like octopus suckers) could improve attachment due to following mechanisms: (i) exploiting the presence of mucus and filaments to increase the viscosity coefficient at the interface and to resist to the shear forces; and (ii
Calibration of quartz tuning fork spring constants for non-contact atomic force microscopy: direct mechanical measurements and simulations
Beilstein J. Nanotechnol. 2014, 5, 507–516, doi:10.3762/bjnano.5.59
- beam length values, a deviation can be noticed. The contribution caused by the torsion can be calculated analytically by the following relation [21]: in which T is the torsional momentum, Φt is the angle of twist in radians, L the length at which the force is applied, G the shear momentum and IT the
Manipulation of nanoparticles of different shapes inside a scanning electron microscope
Beilstein J. Nanotechnol. 2014, 5, 133–140, doi:10.3762/bjnano.5.13
- voltage were 20–50 mV and the corresponding tip oscillation amplitude was in order of 100 nm. The tip oscillated parallel to the sample surface, i.e., in the shear mode [20]. The QTF force sensors were calibrated on a reference contact mode AFM cantilever (NT-MDT, CSG11), which was previously calibrated
- S5, Supporting Information File 1) the NP often moved aside affected by the tip oscillation (Figure 5). Moreover, the force necessary to displace a NP can be overestimated due to an unaccounted amount of energy dissipated in a shear interaction between the tip and the NP. For the parallel tip
- calculated the friction force values, Ffriction, by using a simple relation: where τ is the interfacial shear stress/strength and A is the contact area [26]. The shear strength is defined as an ultimate shear stress τ before the object is displaced, and can be estimated by using the relation τtheo = G*/Z
Static analysis of rectangular nanoplates using trigonometric shear deformation theory based on nonlocal elasticity theory
Beilstein J. Nanotechnol. 2013, 4, 968–973, doi:10.3762/bjnano.4.109
- Mohammad Rahim Nami Maziar Janghorban School of Mechanical Engineering, Shiraz University, Shiraz, Iran 10.3762/bjnano.4.109 Abstract In this article, a new higher order shear deformation theory based on trigonometric shear deformation theory is developed. In order to consider the size effects
- , the nonlocal elasticity theory is used. An analytical method is adopted to solve the governing equations for static analysis of simply supported nanoplates. In the present theory, the transverse shear stresses satisfy the traction free boundary conditions of the rectangular plates and these stresses
- isotropic, orthotropic and anisotropic nanoplates. Keywords: nonlocal elasticity theory; rectangular nanoplate; static analysis; trigonometric shear deformation theory; Introduction In recent years, some new higher-order shear deformation theories have been adopted for studying macro structures such as
Dynamic nanoindentation by instrumented nanoindentation and force microscopy: a comparative review
Beilstein J. Nanotechnol. 2013, 4, 815–833, doi:10.3762/bjnano.4.93
- -dependent shear modulus can vary with the ultimate force applied because of a deviation from linear viscoelastic behavior [30]. Because of their small size and the fine control over force and displacement, the point probes are particularly amenable to dynamic loading, in which a small modulation of several
- indenter. It has been noted that these relations hold strictly only for shear between two parallel plates and the application to nanoindentation experiments should be used with caution [75]. By using the dynamic model shown in Figure 4c, an analytical solution for the resulting displacement amplitude, h0
Size-dependent characteristics of electrostatically actuated fluid-conveying carbon nanotubes based on modified couple stress theory
Beilstein J. Nanotechnol. 2013, 4, 771–780, doi:10.3762/bjnano.4.88
- Timoshenko beam model, which considers the rotational inertia and shear deformation, to investigate the effects of internal fluid flow on the transverse vibration [26]. They reported the natural frequencies of the system for different aspect ratios. Despite some studies concerning the effects of fluid flow
Deformation-induced grain growth and twinning in nanocrystalline palladium thin films
Beilstein J. Nanotechnol. 2013, 4, 554–566, doi:10.3762/bjnano.4.64
- twinning/detwinning processes, stress-driven grain boundary migration and the formation of shear bands [4][5][6][7]. When studying the mechanical properties of nc metals and the associated deformation mechanisms, it is important to consider the preparation technique for the corresponding bulk nc metal
- Schmid-factor (the highest resolved shear stress). Here, randomly oriented twin boundaries can act as barriers to dislocation motion. In nano-twinned Pd, however, partial dislocations nucleate preferentially at twin boundaries. The twin boundaries then act as nucleation site and do not hinder successive
- for the remaining strain that does not come from dislocation/twin activity. Lohmiller et al. has already reported other mechanisms, such as GB shear and slip, as well as GB migration resulting in grain growth [28][45]. Conclusion NcPd thin films with a grain size of about 35 nm (plane view) were
Nanoglasses: a new kind of noncrystalline materials
Beilstein J. Nanotechnol. 2013, 4, 517–533, doi:10.3762/bjnano.4.61
- enhanced free volume in shear bands [9][10], the average free volume content of a glass was found to increase [10][11] with increasing plastic deformation. However, despite the similarity between the microstructural features of a nanoglass produced by consolidating nanometer-sized glassy spheres and a
- nanoglass produced by introducing a high density of shear bands, the results of recent studies by molecular dynamics (MD) [12][13] and Mössbauer spectroscopy of a ball-milled melt-quenched Fe90Sc10 glassy ribbon and a Fe90Sc10 nanoglass suggest that the atomic structure of both kinds of nanoglass differ
- the nanoglass. In structurally homogenous ribbons, only one (or a few) shear bands are known to be nucleated under sufficiently high applied stresses. Plastic flow is limited to these shear bands and frequently results in fracture after an overall plastic deformation of less than 1%. However, in the
Molecular dynamics simulations of mechanical failure in polymorphic arrangements of amyloid fibrils containing structural defects
Beilstein J. Nanotechnol. 2013, 4, 429–440, doi:10.3762/bjnano.4.50
- 5. All three fibril polymorphs demonstrate an anisotropic response to mechanical probing. Similar mean peak forces are required to break the fibrils when the hydrogen-bond networks are probed (“shear” and “stretch”). There are however, very distinct responses in the SMD simulations that probe the
- demonstrates how the details imposed by polymorphic arrangements of the peptides in the fibril can determine the mechanical characteristics when a force is applied in a particular direction. Hydrogen-bond-network response: In the two pulling geometries (“shear” and “stretch”) that primarily interrogate the
- hydrogen-bond networks, similar mean peak forces were recorded for all three polymorphs. The stretch and shear simulations probe the interpeptide hydrogen networks in directions parallel and perpendicular to the fibril axis respectively. Figure 4 shows that pulling parallel to the hydrogen bond network
Optimal geometry for a quartz multipurpose SPM sensor
Beilstein J. Nanotechnol. 2013, 4, 370–376, doi:10.3762/bjnano.4.43
- through an angle θ is given by where J and G are the torsion constant and shear modulus of the beam. In the case of a cantilever beam with a tip of length Ltip (measured from the central axis of the beam), the lateral displacement of the tip apex, Alat, is Ltipθ. Replacing the torque with the lateral tip
Plasticity of Cu nanoparticles: Dislocation-dendrite-induced strain hardening and a limit for displacive plasticity
Beilstein J. Nanotechnol. 2013, 4, 173–179, doi:10.3762/bjnano.4.17
- high tensile strain rates by amorphisation [2] attributed to the kinetic energy of atoms exceeding the enthalpy of fusion [3]. Also, a near-surface nanodisturbance path, where, instead of conventional displacive plasticity, nanoscopic areas of plastic shear accommodate the stress, was reported for Ag
- File 2). We start our analysis by presenting the details of the displacive case. The maximum shear component (the maximum eigenvalue of the atomic stress tensor) in the initial system and at the onset of plasticity for different orientations for a 15.6 Å orifice is illustrated in Figure 2a–Figure 2c
- . For all the orientations, larger than average values of maximum shear are roughly localised on inverted spherical caps joining the edge of the circular orifice. The most extreme values of the atomic shear (parallel 2.4 MPa, orthogonal 2.3 MPa, and tilted 2.3 MPa) are almost the same and are located at
Functionalization of vertically aligned carbon nanotubes
Beilstein J. Nanotechnol. 2013, 4, 129–152, doi:10.3762/bjnano.4.14
- remarkable self-cleaning abilities and the same properties, i.e., high shear and peeling forces (Figure 5) [64][65][66]. A further step in patterning VA-CNTs is the engineering of 3D-architectures. The formation of 3D-aligned carbon nanotube patterns is obtained by growing VA-MWCNTs with different lengths
Plasmonic oligomers in cylindrical vector light beams
Beilstein J. Nanotechnol. 2013, 4, 57–65, doi:10.3762/bjnano.4.6
- microscopes, in combination with a home-built shear force AFM system and the use of sharp gold or glass-fiber tips, we operate a versatile scanning near-field optical microscope (SNOM) system. To measure the near field generated from the plasmonic oligomers, one single oligomer is placed inside the radially
- spatial arrangements imaginable. Schematic of two optical microscopic configurations using a parabolic mirror for focusing (a, adapted from [27]) and an objective lens for focusing (b). Shear-force SNOM configurations can be obtained by integrating a glass fiber (c) or a gold tip (d) to the confocal
Growth behaviour and mechanical properties of PLL/HA multilayer films studied by AFM
Beilstein J. Nanotechnol. 2012, 3, 778–788, doi:10.3762/bjnano.3.87
- exposed to a faster initial load and gives a hint about a non-Newtonian, shear-thinning behaviour [50]. Conclusion Mechanical properties of layer-by-layer assembled PLL/HA films with varied bilayer number were studied by scanning- and colloidal-probe atomic force microscopy. Detailed measurement and data
- . Both relaxation times decrease with increasing initial indentation velocity, suggesting a non-Newtonian, shear-thinning fluid character. Frequency-dependent AFM force [41] and quartz crystal microbalance measurements are planned for a better understanding of shear and friction effects on the mechanical
Effect of spherical Au nanoparticles on nanofriction and wear reduction in dry and liquid environments
Beilstein J. Nanotechnol. 2012, 3, 759–772, doi:10.3762/bjnano.3.85
- use with Au nanoparticles suspended in DI water. In addition to the fact that Au nanoparticles are provided already suspended in DI water, the low viscosity of water and its ability to provide a surface of low shear strength [35] for sliding, makes it a good candidate as an operating fluid. Water is
- contact pressure is reduced, leading to undeformed nanoparticles, which may roll between the surfaces. In water, the presence of a liquid film between the glass sphere and the silicon substrate provides an interface of low shear strength resulting in a lower coefficient of friction [35]. In addition
- contact pressure is reduced. This increases the chances of rolling for the undeformed nanoparticles as part of the friction-reduction mechanism. In the case of DI water without Au nanoparticles, a surface of low shear strength is obtained, which makes it easier for the sapphire ball to slide [35
Friction and durability of virgin and damaged skin with and without skin cream treatment using atomic force microscopy
Beilstein J. Nanotechnol. 2012, 3, 731–746, doi:10.3762/bjnano.3.83
- . Liquid films (lipid and condensed water vapor) present on the skin surface reduce the interfacial shear strength leading to lower friction; however, a thicker film forms meniscus bridges at asperity contacts leading to higher friction [34][35][40]. Cream treatment moistens and softens the skin, which
- reformation of meniscus bridges. As the velocity increases, the meniscus bridges cannot be fully reformed, resulting in a drop in adhesive force and coefficient of friction. In the case of cream-treated skin, the skin cream is typically a shear-thinning fluid, and the viscosity decreases with the increasing
- shear rate leading to a decrease in the coefficient of friction [6][36]. Figure 6b shows the coefficient of friction as a function of normal load. The data shows that the friction for untreated skin samples first decreases then levels off, whereas, for the treated skin samples, it first decreased then
Assessing the plasmonics of gold nano-triangles with higher order laser modes
Beilstein J. Nanotechnol. 2012, 3, 674–683, doi:10.3762/bjnano.3.77
- sample surface or parallel to it. The parameters varied in the Fischer patterns were the size of the triangles, their height and the substrate material (which was either silicon or glass). Using integrated shear-force microscope, we can collect the topography from the sample surface and compare the
- denominations). Not all combinations of sphere size and film thickness could be produced since the film thickness has to be distinctly smaller than the polystyrene spheres in order to obtain flat triangles. Thicker triangles would have the form of a truncated pyramid [26]. By shear-force topographical
- . Plenty of water was used to rinse the surface in order to get rid of the physically adsorbed multilayers. Results and Discussion 1. Topography Investigating the triangle arrays with the shear-force topographical method implemented in our setup [22] and SEM characterisations, we find well aligned
Repulsive bimodal atomic force microscopy on polymers
Beilstein J. Nanotechnol. 2012, 3, 456–463, doi:10.3762/bjnano.3.52
- reported for the same sample based on the results of a resonant shear force experiment [29]. Thus, when imaging flat samples that present such varying elastic properties, topographic contrast is enhanced by the repulsive-imaging process. At a given setpoint, the softer component is substantially deformed
Conducting composite materials from the biopolymer kappa-carrageenan and carbon nanotubes
Beilstein J. Nanotechnol. 2012, 3, 415–427, doi:10.3762/bjnano.3.48
- flow-curve analysis. The viscosity was measured as a function of shear rate for KC solutions over a concentration range of 0.2–1.2% w/v at 21 °C (Figure 1a). All KC solutions displayed shear-thinning behaviour, i.e., decreasing viscosity (η) with increasing shear rate (). These flow curves were fitted
- to the well-known power-law model [44]: where K and n indicate the “consistency” and power-law index, respectively. Figure 1a shows that the viscosity of KC solutions increased with increasing concentration. For example, the apparent viscosity of the KC solution (at shear rate 21 s−1) increased from
- general [47]. Table 1 shows that KC solutions with a concentration <0.5% w/v have power-index values of ~0.8. However, for higher concentrations the solutions become more shear-thinning (n decreases), and thicker (K increases). Figure 1c shows a sharp increase in the apparent viscosity of the KC solution
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