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121.
H.M. Ledbetter 《Ultrasonics》1985,23(1):9-13
For studying welds ultrasonically, the importance of knowing the material's single-crystal elastic constants, the Cijs, is explained. Where these constants are not known, some guidelines are given for estimating them from polycrystalline elastic constants such as Young's modulus and the shear modulus.The important case of [001] fibre texture is considered. Being transversely isotropic, this case exhibits five macroscopic elastic constants, which are related to the three cubic elastic constants: C11, C12, C44. From these five constants the angular variations of Young's modulus, the torsional modulus, and the sound velocities can be computed. For the same [001] fibre texture, results are given for a standard well-characterized material — copper, where the Cijs are well known. 相似文献
122.
Neutron diffraction has been used to measure the crystallite orientation distribution function for a sample of rolled aluminium plate. Based on this study an expression is given for the ultrasonic velocity of the fundamental horizontally polarized shear (SH) wave propagating in the plane of the plate at an angle θ to the rolling direction. This expression is correct to second order in the leading texture component and is compared with the exact numerical result and with measurements of the SH wave velocity for this plate. In textured materials the group and phase velocities are not, in general, parallel and an expression for the angle between them is derived. Inclusion of this effect leads to better agreement between experiment and theory. The results have application to the texture-independent determination of stress with ultrasonics recently proposed by MacDonald and Thompson et al. 相似文献
123.
A series of ternary lead-phosphate glasses doped with samarium trioxide, xSm2O3-(40−x)PbO-60 P2O5 (where x=0.1 to 0.5 mol%) have been prepared by using conventional melt quenching method and their elastic properties have been studied at room temperature. Results from the studies show that both longitudinal and transverse sound velocities decrease by increasing the Sm2O3 content. Elastic moduli, Poisson's ratios decrease with increase of Sm2O3 composition up to 0.3 mol% and then there is a slight increasing trend observed at 0.4 mol%. The densities of these glasses have been measured by using displacement method. The variations of these parameters have been discussed with respect to samarium trioxide concentration. 相似文献
124.
Summary: The use of PMMA as dental and osseous cement and also in the fabrication of intraocular lenses has been widely reported. The combination of its excellent properties with those of hydroxyapatite (HA) to form a composite material, can result in very interesting properties as a biomaterial. The key is to obtain a good filler dispersion and interface bonding. Ultrasonic radiation seems to be a very versatile method for the synthesis of these materials, since the use of conventional initiators can be avoided, the filler dispersion improved and the interface interaction can be promoted. In the present work PMMA/HA composite materials were prepared by three different synthesis routes using ultrasonic radiation, in order to study the effect of the synthesis method on the final microstructure. Method I : in situ synthesis of PMMA and HA, under ultrasonic radiation by emulsion polymerization of MMA and HA precursors. Method II : in situ synthesis of HA, (from its precursors) by high frequency ultrasound in commercial PMMA solution Method III : in situ polymerization of MMA under high frequency ultrasonic radiation and adding HA to the solution and Method IV Mixing of hydroxyapatite nanocrystals, in different proportions, in a solution of commercial PMMA, by different periods from 10 min to 7 h, under low frequency (conventional) ultrasonic radiation, to compare the effect of high frequency and conventional ultrasound radiation. The different materials were characterized by FTIR, SEM, TEM, DRX, 1H NMR and TGA. The results showed that, all the composites prepared by in situ synthesis showed an interaction between HA and PMMA, manifested by a bonding of the phosphate groups with the polar groups of the polymer matrix observed by FTIR. On the other hand, when the synthesis was carried out simultaneously adding HA and PMMA precursors a inhibition of the polymerization reaction of MMA was observed. 相似文献
125.
Sun-Kuk Kim Jeong Tai Kim Hee-Cheul Kim Kyong-Yop Rhee John Kathi 《Journal of Macromolecular Science: Physics》2013,52(4):750-756
Miscibility studies of unsaturated polyester resin (UPR) blends with two different thermoplastics—polystyrene (PS) and polycarbonate (PC), in a common solvent, chloroform, were carried out by viscosity, ultrasonic velocity, density, and refractive index methods. Two interaction parameters, μ and α were calculated using viscosity data for these blends. The positive interaction parameter values (μ and α > 0) obtained for the UPR/PS blend and the negative interaction parameter values (μ and α < 0) obtained for the UPR/PC blend indicate that the former is a miscible blend and the latter is an immiscible blend. These results were further confirmed by the ultrasonic velocity, density, and refractive index measurements. 相似文献
126.
Glasses in the 90Bi2O3–(10?x)Er2O3?xPbO (x = 3, 5, 7, 9 and 10 mol%) system have been prepared by the melt-quenching technique. Elastic properties and FT-IR spectroscopic studies have been employed to study the role of PbO in the structure of the investigated system. Elastic properties and Debye temperature were recorded using sound wave velocity measurements at 4 MHz at room temperature. The results showed that density increased and molar volume decreased, while both sound velocities increased with an increase in x. Infrared spectra of the glasses revealed that the bismuthate network is affected by an increase in PbO content. The results are interpreted in terms of the conversion of [BiO6] into [BiO3] structural units, indicating that Pb ions have been substituted for erbium ions as tetrahedral network formers. The elastic moduli increased with increasing PbO content due to the increased average bond strength and degree of connectivity, as a direct effect of the increase in [BiO3] structural units. 相似文献
127.
The longitudinal ultrasonic velocity (V) and attenuation at a frequency of 10?MHz, as well as magnetization and resistivity, have been measured in the single-phase polycrystalline La1– x Sr x FeO3 (x?=?1/3, 0.4, 0.45). Upon cooling down from high temperature, a slight softening in V and dramatic stiffening are observed in all samples, and this stiffening is coincided with a big attenuation peak. The relative increase of V is proportional to the Sr concentration, which implies that this anomaly is strongly correlated with Fe4+. However, no obvious changes in magnetic and electric properties are found at this temperature range. The analysis suggests that this feature may be caused by the Jahn–Teller effect of Fe4+ and correspond to the formation of short-range charge-ordering state. 相似文献
128.
T. V. Nikolaenko 《Journal of Applied Spectroscopy》2008,75(4):603-607
Diffraction of light by ultrasonic Gulyaev-Bleustein waves is studied under Fresnel reflection conditions. It is shown that
Gulyaev-Bleustein waves propagating in GaAs-AlGaAs structures can be detected by acousto-optic methods under conditions for
Fresnel reflection of diffracted waves. It has been established that the considered structures are promising for design of
multichannel acousto-optical deflectors and modulators.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 4, pp. 583–587, July–August, 2008. 相似文献
129.
Iodine release in potassium iodide solution has been investigated under the irradiations of ultrasound and visible light respectively and simultaneously. We have observed that the amount of iodine liberated under the combined irradiation of ultrasound and visible light is larger than the sum of that under the respective irradiations of ultrasound and visible light, indicating a synergistic effect of ultrasound and visible light irradiations. Based on the investigation of the reaction kinetics of iodine liberated, we have ascribed the synergistic effect to the perfect stirring of the photochemical reactor induced by the applying simultaneous ultrasound. The ideal stirring can result in the homogenization of the primary light effect in the whole reaction medium, which induces the acceleration of the photochemical reaction. On behavior of our knowledge, there are few reports on the investigations of utilizing the combination of ultrasonic energy and light energy to accelerate the reaction yield and rate as well as the kinetics of the reaction. 相似文献
130.