ultrasonic shear wave study of the mechanical properties of a nematic liquid crystal.

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  • English
University Microfilms International , Ann Arbor, Mich, London
The Physical Object
Paginationviii, 163 leaves, plates
ID Numbers
Open LibraryOL21598698M

Ultrasonic shear wave study of the mechanical properties of a nematic liquid crystalCited by: 4. The ultrasonic shear wave method is a technique which encompasses angle beam ultrasonic testing to identify subsurface anomalies not found directly underneath the transducer itself.

Shear wave ultrasonic testing uses ultrasonic energy that is reflected back to the. The visible interaction of low‐intensity ultrasonic waves with a nematic liquid crystal may be explained simply by the hypothesis of a torque tending to orient LC molecules perpendicular to the vibrations.

It is shown how this torque can be related to anisotropic attenuation of ultrasound and minimization of propagation losses. First theoretical developments and optical measurements on a Cited by: Determinations of shear wave speeds of sound and attenuation coefficients are reported for soft tissues, a silicone rubber reference material, and a gel used in manufacturing ultrasonically tissue‐mimicking materials.

Description ultrasonic shear wave study of the mechanical properties of a nematic liquid crystal. FB2

Fresh bovine tissues were investigated, including calfskin, liver, cardiac muscle, and striated muscle. Because of the very large shear wave attenuation coefficients Cited by: thin nematic liquid-crystal layer by heat current has also been investigated for the above purpose.9–11) The texture induced under elastic wave propagation in the nematic liquid-crystal cell has not yet been investigated intensively.

A striped domain pattern appears under the existence of an elastic wave in a liquid-crystal cell containing a thin. The peculiarities of the orientational transition in a homeotropic layer of a nematic liquid crystal (NLC) under obliquely and normally incident shear waves have been investigated for the frequency range where the viscous wavelength in an NLC is smaller than the layer thickness, while the wavelengths of an elastic wave in the NLC and a shear wave in the solid substrate (plate) are larger.

FLEXIBLE POLYMERS IN A NEMATIC MEDIUM L Fig. - Schematic diagram of the acoustic system showing the 2 orientations in which the viscosity coefficients were measured. The shear vibration is parallel to the reflecting surface; 0 is the angle of incidence and k the wave vector of the shear wave in the nematic.

The shear wave propagates in the nematic practically. In the case of a nematic liquid crystal the order is the orientational order of the molecules. (19)]. This was the first observation of the predicted shear wave in smectics.

Many ultrasonic experiments have attempted to generate and observe the shear mode in smectics, but the experimental problems are severe; the velocity is very low (on.

Structural changes induced by electric and weak magnetic fields in the nematic liquid crystal (6CHBT) doped with low concentration (1 × 10 −3, 1 × 10 −4, 1 × 10 −5) of carbon nanotubes, including single-walled (SWCNT), multi-walled (MWCNT) and functionalized with Fe 3 O 4 nanoparticles are investigated using surface acoustic waves (SAW) and magneto-optical effect.

of material properties on ultrasonic wave propagation in cort ical bone: application to axial transmission,” J Acoust Soc Am. (6), – (). shear impedance of the liquid by the following formulae Zq is the shear mechanical impedance of the fused quartz bar and is a constant ( x dyn.

cm- 3), and 0 is the angle of incidence of the ultrasonic wave to the reflecting surface of the bar. (3) shows that R and X respectively, are deter. The reflection of ultrasonic shear waves from a solid‐liquid boundary When an ultrasonic shear polarized wave (whose propagation mode is represented in Figure 1(a)) strikes the boundary between a solid and a liquid, at normal incidence angle, part of the ultrasonic energy is.

The viscous and elastic properties of a ZhK nematic liquid crystal (NLC) were studied in a temperature interval from to K by method of ultrasonic spectroscopy in the 3–63 MHz.

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Properties of Ultrasonic waves. The human ear is sensitive to sound waves in the frequency range fromHz. This range is called Auduble range. Sound waves of frequency more tHz are called Ultrasonics. These frequencies are beyond the audible limit. These waves also travel with the speed of sound(m/s).

Ultrasonic waves propagated through a medium can be detected in a number of ways. Some of the methods employed are as follows: (1) Kundt’s tube method: Ultrasonic waves can be detected with the help of Kundt’s tube.

At the nodes, lycopodium powder collects in the form of heaps. crystals Article Shear-Thinning Characteristics of Nematic Liquid Crystals Doped with Nanoparticles Munehiro Kimura 1,*, Zur Ain Binti Hanafi 1, Tatsuya Takagi 1, Ryosuke Sawara 1 and Shuji Fujii 2 1 Department of Electrical Engineering, Graduate School of Engineering, Nagaoka University of Technology, Kamitomioka, Nagaoka, Niigata, Japan; [email protected]

Figure 2 shows snapshots of the ultrasonic wave displacement fields in the plate at several different time epochs after the elastic waves are launched. From these figures, we can see that a total of three waves, a Rayleigh wave (R), a shear wave (S), and a longitude wave (L) are generated.

Shear Wave Generation. Shear waves have an inherent polarization direction depending on how they are generated. Pictured below are horizontally polarized shear waves propagating along the length of a plate.

Electromagnetic-acoustic transducers (EMAT) designed to generate shear waves actually vibrate the atoms within the material being investigated. Keywords: Shear Modulus, Polymer Concrete, Modulus of Elasticity, Poissons's ratio,Ultrasonic wave. Introduction The work in this investigation was planned in order to obtain further information about the effect of addition of Silica sand to the Unsaturated polyester resin on the some mechanical properties of PC such as modulus of.

Principle: The velocity of ultrasonic waves in a liquid medium is determined using the eq. V QO1 where Q is the frequency of the ultrasonic waves and 1 O is its wavelength in liquid.

Ultrasonic waves are mechanical waves Hence their propagation through a medium assists the study of mechanical properties of the medium. adshelp[at] The ADS is operated by the Smithsonian Astrophysical Observatory under NASA Cooperative Agreement NNX16AC86A.

Shear waves travel at about half the speed of compressional waves (e.g., in iron, 3, metres per second compared with 5, metres per second). The shear-wave velocity in a crystal varies according to the direction of propagation and the plane of polarization (i.e., plane of vibration) because of the variation of shear modulus in a crystal.

In solids, sound waves can propagate in four principle modes that are based on the way the particles oscillate.

Sound can propagate as longitudinal waves, shear waves, surface waves, and in thin materials as plate waves. Longitudinal and shear waves are the two modes of propagation most widely used in ultrasonic testing.

Ultrasonic Wave Frequency. occur at a frequency of >20, Hz (20 kHz) – Combine the motion of both longitudinal and shear waves – Follow the surface around curves and therefore are sensitive to surface defects Properties of Waves (wavelength, frequency, and velocity).

Martinoty, P., Candau, S.: Determination of viscosity coefficients of a nematic liquid crystal using a shear waves reflectance technique. Mol.

Shear flow reveals splendid and unforeseen shear induced nematic phases away from the equilibrium N-I temperature in the isotropic phase of Side-Chain Liquid Crystal Polymers. Ultrasonic refers to any study or application of sound waves that are higher frequency than the human audible range.

Ultrasonic waves consist of frequencies greater than 20 kHz and exist in excess of 25 MHz. Ultrasonic waves are used in many applications including plastic welding, medicine, jewelry cleaning, pipe inspection, and nondestructive.

An Ultrasonic Shear Wave Study of the Mechanical Properties of a Nematic Liquid Crystal: Y. Lee: Glenn Brown: Chemistry Crystal Structure Analysis of X-Ray of 2,2'-Dibromo-4,4'-bis-(p-methoxybenzylideneamino) Biphenyl: David, Lesser: Glenn Brown: Chemistry Mossbauer Effect in a Smectic Liquid Crystal: Jack Wilson: David.

Ultrasonic velocities of the dilatational and shear waves in water‐saturated frozen soils were measured as a function of temperature by both pulse first arrival and critical angle methods. A strong correlation exists between the dilatational wave velocities and the unfrozen water content.

The first goal of this study is to identify the ideal piezoelectric material for the manufacturing of rheological reflectance ultrasonic sensors.

The second goal is to integrate the ultrasonic rheometer within a gas absorption reactor and to measure viscosity changes in an ionic liquid (IL) caused by gas absorption. To achieve the objectives, bismuth titanate, lead titanate, lead metaniobate.

We have investigated the linear response of shear stress to ac electric fields under shear flow in a nematic liquid crystal. The experimental results were compared with the theoretical results derived from the Ericksen-Leslie theory.

Although close agreement was obtained at low shear rates, discrepancies were observed at high shear rates.

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By introducing a two-mode coupling model the.The response of a nematic liquid crystal to oscillating shear flow has been calculated. In both low and high frequency limits, the macroscopic response is dominated by viscous effects, under the influence of dominant boundary‐induced and hydrodynamic torques, respectively.

At intermediate frequencies, distortional (Frank) elasticity lends the macroscopic response viscoelastic character.Step strain experiments on 5CB and 8CB provide an independent measurement of viscoelastic properties. Aside from confirming the flow classification of these model nematics, these new experimental methods establish a framework for the study of director dynamics in polymeric nematic liquid .