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81.
Dimitris Tsiourvas Dimitra Kardassi Constantinos M. Paleos Antoine Skoulios 《Liquid crystals》2013,40(9):1213-1217
Alkaline-earth-metal dihexadecyl phosphate salts were synthesized, and their thermal stability was evaluated by thermogravimetry. Their thermotropic liquid crystal behaviour was investigated by differential scanning calorimetry, polarizing optical microscopy, dilatometry, and X-ray diffraction. On heating, the calcium, strontium, and barium salts exhibit columnar liquid crystal phases, whereas the less ionic beryllium and magnesium salts melt directly into isotropic liquids. 相似文献
82.
The results of a comprehensive mechanical analysis of five silicone-based elastomers are presented. Large strain monotonic tests were performed under uniaxial, strip biaxial and equi-biaxial stress states. Based on the multiaxial experimental data, hyperelastic constitutive models were determined for each material. The small strain elastic modulus ranges from 49 kPa to 1.5 MPa, and the materials show different degrees of non-linearity of their stress-strain response. Data on the time and history dependence allow determining the deviation from the behavior predicted using a non-dissipative hyperelastic constitutive model. Next to representing a guideline for a comprehensive characterization of highly deformable materials, the present results provide data which can be used for the selection of an appropriate material, depending on the specific application. The corresponding models can be used to simulate the performance of each elastomer in applications involving large strains and multiaxial loading states. 相似文献
83.
Myong In Oh 《Molecular physics》2019,117(20):2889-2899
ABSTRACTWe explore the solvation patterns of a charged rigid and semi-rigid linear macroion in an aqueous droplet. The solvation patterns are summarised in an empirical ‘phase diagram’ on the parameter space defined by the length of the macroion and its charge density. In the study, we employ molecular dynamics and atomistic modelling. The macroion is represented by a positively charged carbon nanotube. Linear macroion-solvent interactions in droplets are distinct from those of spherical ions because of the interplay among several factors such as the tendency of the solvent to form spherical droplets in order to minimise the surface energy, the constraint on the charge of a spherical droplet imposed by the Rayleigh limit, the solvation energy of the macroion and its length. The combination of all these factors may lead to a variety of solvent distributions along the rigid rod such as asymmetric solvation of the linear macroion, formation of spiky ‘star’-like distribution of solvent, partial wetting of the rod by a droplet. The study provides insight into the solvation of macroions in droplets with applications in electrosprayed macroions and atmospheric aerosols. We also propose a possible path of generating a sequence of nanoparticles of different shapes (spheres, multi-point stars) along a linear macromolecule by exploiting the various solvation patterns. 相似文献
84.
ABSTRACTMolecular simulations have shown that when a nano-drop comprising a single spherical central ion and a dielectric solvent is charged above a well-defined threshold, it acquires a stable star morphology. A linear continuum model of the ‘star’-shapes comprised electrostatic and surface energy is not sufficient to describe these shapes. We employ combined molecular dynamics, continuum electrostatics and macroscopic modelling in order to construct a unified free energy functional that describes the observed star-shaped droplets. We demonstrate that the Landau free energy coupled to the third-order Steinhardt invariant mimics the shapes of droplets detected in molecular simulations. Using the maximum likelihood technique we build a universal free energy functional that describes droplets for a range of Rayleigh fissility parameter. The analysis of the macroscopic free energy demonstrates the origin of the finite amplitude perturbations just above the Rayleigh limit. We argue that the presence of the finite amplitude perturbations precludes the use of the small parameter perturbation method for the analysis of the shapes above the Rayleigh limit of the corresponding spherical shape. 相似文献
85.
Yu. V. Nemirovskii 《Mechanics of Composite Materials》2001,37(5-6):421-430
New formulations and methods for the solution of the inverse problems of thin-walled layered and reinforced shells and plates are discussed. Rational projects with regard for the requirements of nonflexural deformations in layered structural members, the given deformability of particular surfaces, the realization of a strictly momentless state, an equally stressed reinforcement, and the breaking strength of the binder at the interfaces are investigated. A brief review of the known solutions to these problems is given, and solutions to some new problems are described. 相似文献
86.
A. B. Mitkevich 《Mechanics of Composite Materials》2006,42(4):297-302
The deformation of pressure vessel domes in asymmetric winding with the use of two families of yarns is accompanied by shear
deformations and torsion. For the case of large deformations, a system of equations for describing the stress-strain state
of an asymmetrically reinforced netlike shell of revolution loaded with an internal pressure is obtained. It is shown that
the shear deformations depend on the deformations of both the yarn families and the deformations of meridians and parallels
of the shell. As an example, the dome of a pressure vessel in a deformed state is calculated for an initial equilibrium shape
determined on the assumption that the yarns are inextensible.
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 4, pp. 425–432, July–August, 2006. 相似文献
87.
M. M. Carroll 《Journal of Elasticity》2007,88(2):141-149
In an earlier paper, the broadest classes of compressible isotropic strain energies that support irrotational universal deformations
were identified and the problems of cylindrical and spherical inflation or compaction were solved in closed form for all of
these strain energies. Similar closed form solutions of the problem of azimuthal shear are presented here.
相似文献
88.
Experimental data for simple tension suggest that there is a power–law kinematic relationship between the stretches for large
classes of slightly compressible (or almost incompressible) non-linearly elastic materials that are homogeneous and isotropic.
Here we confine attention to a particular constitutive model for such materials that is of generalized Varga type. The corresponding
incompressible model has been shown to be particularly tractable analytically. We examine the response of the slightly compressible material
to some nonhomogeneous deformations and compare the results with those for the corresponding incompressible model. Thus the effects of slight compressibility
for some basic nonhomogeneous deformations are explicitly assessed. The results are fundamental to the analytical modeling
of almost incompressible hyperelastic materials and are of importance in the context of finite element methods where slight
compressibility is usually introduced to avoid element locking due to the incompressibility constraint. It is also shown that
even for slightly compressible materials, the volume change can be significant in certain situations.
相似文献
89.
E. V. Korobko Prof. V. E. Dreval Z. P. Shulman V. G. Kulichikhin 《Rheologica Acta》1994,33(2):117-124
Studies have been made of concentrated (up to 60%) diatomite suspensions in transformer oil, the structure and theological properties of which depend on an applied electric field. Studies have been conducted of steady-state and transient regimes of straining involving continuous and periodic shear. The structure in such suspensions is formed in the presence of an electric field of 10–3 –102 duration. The suspensions under continuous stationary strain behave as non-Newtonian fluids with a yield stress dependent on electric intensity. Under periodic deformation conditions the test suspensions exhibit elasticity which abruptly diminishes with increasing deformation amplitude. 相似文献
90.
Differential conditions are derived for a smooth deformation to be universal for a class of isotropic hyperelastic materials
that we regard as a compressible variant (a notion we make precise) of Mooney–Rivlin’s class, and that includes the materials studied originally by Tolotti in 1943
and later, independently, by Blatz. The collection of all universal deformations for an incompressible material class is shown
to contain, modulo a uniform dilation, all the universal deformations for its compressible variants. As an application of this result, by searching
the known families of universal deformations for all incompressible isotropic materials, a nontrivial universal deformation
for Tolotti materials is found.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献