An automatic technique for measuring the surface tension of liquid metals

A methodology for automatic measurement of surface tension of liquid metals is presented. The procedure involves the digitization of a television image of a drop of the liquid metal, image processing to obtain the real coordinates of the drop profile, and a final computation of the drop surface tension by a nonlinear regression technique. The method is faster and more reliable than other classical methods, and yields results that are reproducible and as precise as those obtainable by non-automatic procedures. An important feature of this approach is that it can be used for metallurgical tests to check the quality of an alloy during its production, or to provide surface tension data in non-equilibrium processes.     

Automatic technique for measuring the Polder resonance in ferritespheres

An automatic technique for measuring the parameters of Polder resonance in polycrystalline ferrite spheres is proposed. The diagonal elements of the external susceptibility tensor versus DC magnetic field are calculated from the changes in resonance frequency and unloaded Q factor of a microwave cavity by perturbation theory. From these diagonal elements, all the elements of the intrinsic permeability tensor can be obtained. By fitting the theoretical curves to experimental data, the parameters of Polder resonance, ΔH M_s, and the g factor, are simultaneously calculated. The whole measurement procedure is controlled by a desktop computer. An accuracy of 5% is obtained in ΔH and M _s, and of 0.1% in the g factor     

Continuous micro-indenter push-through technique for measuring interfacial shear strength of fiber composites

This paper describes a continuous push-through, micro-indentation technique for measuring the fiber-matrix interfacial shear strength. E-glass fibers embedded perpendicular to the plane of thin polished specimens of epoxy matrix, with and without coupling agents, were indented with a micro-indenter until failure of the interface occurred and the fibers were pushed through the epoxy. The results show over 60% higher interfacial shear strength for fibers with coupling agent than for fibers without coupling agent. Average shear strength values obtained via the indentation technique are in good agreement with those obtained from the single-fiber-composite test. Absence of acoustic emission signals for debonding of the fibers coupled with no sudden drops in load vs indentation depth suggest that in this geometry the debonding is a slow, continuous process for both fiber surface treatments.     

微波陶瓷介电性能自动测试系统

介绍了平行板介质谐振器法测试微波介质陶瓷的基本原理,建立一套基于该方法的自动测试系统并对测试结果进行分析.使用表明该自动测试系统稳定、重复性好、测试效率高.测试系统的建立为微波介质陶瓷的研究提供了有效测试手段.     

Investigation of technique for measuring liquid volume under micro-gravity conditions

Measurement of liquid volume under the micro-gravity condition is an important aspect of space technology. In an attempt to create an effective and low-cost measurement system, a Helmholtz resonance technique was applied. Two different liquids were tested. We used water and liquid nitrogen as test liquids, the latter to confirm the applicability of this measurement technique to cryogens. It was found that the measurement technique using Helmholtz resonance is applicable under micro-gravity conditions. However, it was also found that obtaining accurate velocity of sound is important for the measurement. The measurement of spatial temperature distribution in the container is necessary to apply this measurement technique to cryogens because the velocity of sound has strong temperature dependency.     

A pulsed spacecharge technique for measuring ionic mobilities in liquid

By measuring the spacecharge-limited field emission and field ionization characteristics, ionic mobilities in cryogenic liquids including helium can be easily determined.The technique developed uses a simple diode electrode structure similar to that used previously to study dc characteristics.     

Helmholtz resonance technique for measuring liquid volumes under micro-gravity conditions

The Helmholtz resonance technique has been investigated for measuring liquid volumes under micro-gravity conditions. We proposed a theoretical model of the Helmholtz resonance phenomenon induced in a closed container, and carried out a micro-gravity experiment to confirm the applicability of the measurement technique using water as a test liquid. A swept frequency signal was added to a loudspeaker, and together, a microphone and the loudspeaker picked up the sound of the Helmholtz resonance. The liquid volume was calculated from the Helmholtz resonance frequency using an equation derived from the theoretical model. The liquid volume obtained from the micro-gravity experiment agreed well with the liquid volume obtained under terrestrial conditions. Thus, it was confirmed that the Helmholtz resonance technique was applicable for measuring liquid volume under micro-gravity conditions.     

New evaluation technique of interfacial properties in GFRP

A new method was proposed to evaluate the mechanical properties at the interface between the fibres and the matrix in composites using an embedded single fibre coupon test. A mechanical parameter at the interface (called the interfacial transmissibility, ) was derived from the fibre strength and the apparent stress of the fibre immediately before the first fracture of embedded fibre, _fa. This parameter indicated the degree of the mechanical transmission from the matrix to the fibre through the interface. This avoided some complicated problems such as the stress distribution along fibre fragments and the critical fragment state in a typical single-fibre test. This new method was tried to determine the -values for a fibre glass/epoxy resin with different amounts of a coupling agent at the interface. In order to measure the stress at the first fracture, the fracture process was monitored with a video camera during the single fibre test. The stress values at the first fracture for many coupons were analysed as a function of the three-parameter Weibull distribution. The resulting average stress and its coefficient of variation indicated that the reliability of the measurement for the stress at the first fracture was not less than that obtained by the usual single-fibre test. The change of interfacial transmissibility with amount of the coupling agent revealed the existence of an optimal interface.     

A transient (subsecond) technique for measuring heat of fusion of metals

A transient technique is described for measuring the heats of fusion of metals with melting temperatures above 1500 K. The specimen configuration consists of a strip of the metal under study sandwiched between two strips of another metal with a higher melting temperature. The basic method consists of rapidly heating the composite specimen by passing a subsecond-duration electrical current pulse through it and simultaneously measuring the radiance temperature of the containment metal surface, as well as the current through and voltage drop across the specimen. The melting of the metal under study is manifested by a plateau in the temperature versus time function for the containing metal surface. The time integral of the power absorbed by the specimen during melting yields the heat of fusion. Measurements on several tantalum-niobium-tantalum specimens yield a value of 31.5 kJ · mor^–1 for the heat of fusion of niobium, with an estimated maximum inaccuracy of ± 5%.     

Electrical transport properties of some liquid metals

In the present article, we report the electrical transport properties, namely, the electrical resistivity ( ρ), the thermoelectric power (TEP) ( α), and the thermal conductivity (σ) of several monovalent, divalent and polyvalent liquid metals of the different groups of the periodic table on the basis of model potential formalism. The well known empty core model (EMC) potential of Ashcroft is used for the first time with seven local field correction functions proposed by Hartree (H), Hubbard-Sham (HS), Vashishta-Singwi (VS), Taylor (T), Ichimaru-Utsumi (IU), Farid et al. (F) and Sarkar et al. (S) in the present computation and found suitable for such study. In the calculation of these properties, we have used the values of the theoretical structure factors due to hard core fluid theory. It is concluded that the comparisons of present and theoretical or experimental findings, wherever they exist, are highly encouraging. Published in Russian in Teplofizika Vysokikh Temperatur, vol. 46, No. 6, 2008, pp. 870–880.     

Thermodynamic properties of liquid metals and alloys

A modified cellular model of liquids is used to develop a method for calculating thermodynamic properties of liquid metals and their alloys, which are widely used in compact modern heat exchange equipment operating at high thermal flux densities. The approach presented herein permits calculation of the properties of metals from various groups by a single consistent technique. Good agreement was found with experimental data for a significant number of liquid metals and their alloys.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 59, No. 5, pp. 832–840, November, 1990.     

Thermal properties of liquid and solid metals

New generalized expressions for compressibility and thermal expansion of liquid and solid metals are presented.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 50, No. 6, pp. 979–983, June, 1986.     

A technique for the determination of interfacial properties from debond length measurement

Fiber-matrix interfacial debonding is observed and the debond length is directly measured during flexure tests performed on transparent SiC fiber-reinforced borosilicate glass composites. The relationship among the debond length, applied stress, and interfacial properties is investigated both experimentally and theoretically. A new technique based on debond length measurement is introduced for measuring fiber-matrix interfacial properties such as interfacial shear strength, frictional shear stress, and interfacial debond energy. Analytical models are employed for the new technique to interpret the experimental data. Fiber pushout technique is also employed to measure the interfacial properties independently. It is shown that these two different techniques of debond length measurement and fiber pushout test for measuring the interfacial properties can provide comparable results.     

A new experimental technique for studying mass transport in liquid metals

A new experimental technique was developed having general applicability to the study of a variety of mass transport effects in liquid metal alloys. This technique is based on the real-time monitoring of compositional changes at the outer diameter of a horizontally rotating bilayer melt tube through the use of isotope-excited X-ray fluorescence methods. The apparatus is described and applications to the measurement of interdiffusion coefficients as well as anomalous transport, involving the Rayleigh-Taylor instability, are discussed. Unlike prior methods for studying diffusion in liquid metals, the present technique eliminates uncertainties associated with solute redistribution during solidification. Another advantage is the ability to detect non-diffusive contributions to mass transport, in real time.     

A microsecond-resolution transient technique for measuring the heat of fusion of metals: Niobium

A microsecond-resolution pulse-heating technique is described for the measurement of the heat of fusion of refractory metals. The method is based on rapid resistive self-heating of the specimen by a high-current pulse from a capacitor discharge system and measurement of the current through the specimen, the voltage across the specimen, and the radiance temperature of the specimen as a function of time. Melting of the specimen is manifested by a plateau in the temperature versus time function. The time integral of the power absorbed by the specimen during melting yields the heat of fusion. Measurements gave a value of 31.1 kj · mol^–1 for the heat of fusion of niobium, with an estimated maximum uncertainty of ±5%. Electrical resistivity of solid and liquid niobium at its melting temperature was also measured.     

A transmission line technique for measuring the properties of magnetic films

A novel technique is described to use the magnetic-loading effect of a film on a strip transmission line as a means for measuring the magnetic properties (anisotropy and coercivity) of a thin film. This technique is easy to implement and is particularly useful for film arrays where strip transmission lines are of sufficient length to permit a clear resolution of the film-loading effect.     

Electrical conductivity measurements in liquid metals by rotational technique

The rotational contactless inductive measurement technique has been developed to measure the electrical conductivity of liquid metals. This method is based on the phenomena when a conductor material rotates in a magnetic field, circulating eddy currents are induced and generate a damping torque proportional to the electrical resistivity of the material. The technique was tested to measure the conductivity of five conductors and one low melting composite (LMA-158).