Effect of stresses on the ultrasonic pulse velocity in concrete

Since the stress-strain curve of a concrete is not linear, at least under the first loading, one would expect that the presence of stresses would reduce the velocity of ultrasonic pulses in the concrete. The experimental investigation of this expectation is the topic of this paper. Mature concrete cylinders of different compositions were subjected to various types of compression loading (gradually increasing load, repeated loading, etc.), and pulse velocities were measured in various manners (with different frequencies and various paths) both in the loaded and unloaded states. The experimental results clearly indicate that the pulse velocity in concrete is independent of the stress level to a surprisingly large extent, that is, up to about 70% of the compressive strength. This means, in practical terms, that stresses prevailing in the concrete of a structure do not have to be taken into account when pulse velocity data are used for the evaluation of the quality of concrete.

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Résumé Etant donné que la courbe contrainte/déformation d'un béton n'est pas linéaire, tout au moins lors du premier chargement, on pourrait s'attendre à ce que la présence de contraintes réduise la vitesse des ultrasons dans le béton. Cet article décrit une étude expérimentale de cette supposition. On a soumis des cylindres de béton durci de compositions diverses à différents types de chargement en compression (charge en augmentation croissante, chargement répété etc.) et on a mesuré les vitesses d'impulsion de différentes manières (fréquences différentes et tracés variés) à la fois en état de chargement et de déchargement. Les résultats expérimentaux montrent clairement que la vitesse d'impulsion dans le béton est indépendante du niveau de contrainte à un degré étonnamment important, soit jusqu'à environ 70% de la résistance à la compression, ce qui signifie dans la pratique qu'il n'y a pas lieu de tenir compte des contraintes exercées dans une structure en béton quamd on se sert de l'auscultation dynamique pour évaluer la qualité du béton.

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A portion of this paper was presented in the Research in Progress session at the Annual Convention of ACI. Atlanta, Georgia, February 1989.     

Investigations of the equilibrium properties of liquid bromoalkanes on the saturation curve

Results are given of measurements of ultrasonic velocity and density of the liquid phase of bromoalkanes on the saturation curve in the temperature range from 243.15 to 423.15 K. The experimental data are used for studying the structure and pattern of intermolecular forces of the foregoing substances.     

多元有机混合液体声速温度系数的预测方法

根据Jacobson理论及液体声速与分子自由程的关系 ,导出了多元有机混合液体声速与各组分声速之间的关系 ;推导出多元有机混合液体声速温度特性的预测公式 ,并根据组成多元有机混合液各组分特性参量 (摩尔分数、密度、自由程、等压膨胀系数等 ) ,利用文中给出的多元有机混合液声速的温度特性预测公式 ,对由丙酮、四氯化碳、苯、甲醇组成的三元系、四元系有机混合液体的声速温度特性进行了理论值的预测 ,理论预测结果与实验测量结果符合较好     

Stress dependency on ultrasonic wave propagation velocity

The velocity of an ultrasonic wave propagating in the uniformly deformed isotropic solid was analysed by the Eulerian viewpoint. The pseudo elastic coefficient (PEC) was used to solve the equation of motion of the elastic wave under finite deformation. The infinitesimal displacement gradients are connected to the stress increments by thePEC. Using thePEC and the partial differential equation of motion, the velocity of ultrasonic wave was quantitatively related to applied stress, moreover, the stress dependence on longitudinal and transverse wave velocities propagating in the direction parallel or perpendicular to the uniaxial tensile direction could be cleared. Consequently, the Murnaghan's third order elastic constants can be calculated by precisely measuring the uniaxial tensile stress and ultrasonic wave velocity.     

有关全液体空分设备开车操作的探讨

介绍了华东气体公司的KDONAr 2 0 0 0Y/ 370 0Y/ 70Y型空气分离设备流程特点 ,总结分析该设备开车中出现的问题 ,并以此为例探讨全液体空分设备开车的操作特点     

Thermal conductivity of organic liquids

A new instrument and technique for determining the thermal conductivity of liquids by the coaxial cylinder method are described. Experimental values of the thermal conductivity, obtained over a broad temperature interval, are compared with the results of other investigators.     

Dispersions of oxide powders in organic liquids

Thirteen oxide powders, all of which are important in the making of capacitors, were dispersed in nineteen pure organic liquids and water. The dispersions were characterized according to sediment volume results. Further experiments were performed to qualify the effects of moisture, particle concentration, and particle size distribution. Scanning electron micrographs of centrifuge casts of each powder in their best and worst dispersing medium were used to characterize further the dispersions. Results showed that alcohols and aldehydes were the best pure liquid dispersing mediums and hydrocarbons, ketones, and ethers were poor. The best results were obtained for a narrow-sized zirconia powder dispersed in methanol.     

Dynamic-scaling theory of critical ultrasonic attenuation in binary liquids

The critical slowing down that sets in near the critical point of a second-order phase transition is manifested in fluids by a diverging relaxation time for the long-wavelength order-parameter fluctuations. This divergence has a profound effect on all of the transport properties. In sound propagation, the adiabatic compressions and dilations produce temperature swings which the order-parameter fluctuations can follow fully only if the sound frequency is smaller than the relaxation rates in the fluid. As the critical point is approached this condition is violated and a lagging, or hysteretic, response results. As demonstrated by Clerkeet al., the known amplitude of the temperature swings leads to a prediction of ultrasonic attenuation at the critical point that agrees, in magnitude, exactly with that found by Harada et al. The theoretically predicted scaling function that describes how the attenuation and dispersion vary as the critical point is approached is in good agreement with the experimental findings of Garland and Sanchez.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.     

Dependence of the transport properties of liquids on the sound velocity and density

Linear relations expressing the transport properties of liquids as a function of the sound velocity and the density are derived according to the Shirokov dimensionless group, Rao's rule, and the author's formula =m+n.Deceased.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 43, No. 1, pp. 81–83, July, 1982.     

Molecular thermal conductivity of organic liquids

The molecular thermal conductivity of a number of organic liquids is measured using a nonstationary method in an optically thin layer.     

Effect of heat treatment on ultrasonic velocity in ductile cast iron

Abstract

The measurement of the ultrasonic velocity is a common method in the foundry industry for the evaluation of the nodularity in ductile iron castings. Practical experience has shown that heat treatment can reduce the ultrasonic velocity compared to the as cast condition. Using ductile iron samples with different heat treatments in order to vary the ferrite and pearlite content respectively confirmed this decrease in the ultrasonic velocity compared to the as cast state. Further investigations showed that with all the heat treatments applied, irrespective of their effect on the microstructure, the density was decreased. The decrease in density correlated with the decrease in ultrasonic velocity for all heat treatments. The mechanisms involved in the reduction in the density are discussed.     

Dynamic nonlinear properties of viscoelastic liquids from the rheological flow curve

A method is developed for prediction and calculation of nonlinear properties of viscoelastic liquids solely by measurement of tangent stresses during flow in a rheometer.Translated from Inzhenerno-Fizicheskii Zhurnal. Vol. 57, No. 5, pp. 786–788, November, 1989.     

A relation between interfacial and bulk properties along the saturation curve

A liquid-vapor interface in thermal equilibrium was considered, where the pressure tensor depends upon the density (z) and the position z. The surface tension coefficient results are parametrized with the bulk compressibility, liquid-vapor density difference, and interfacial width along the saturation curve. Previous results at the triple and critical points reported by other investigators are verified. Also included is a plot of the computed results using the parametric equation and experimental data for different substances.     

Prediction of ultrasonic wave velocity in particleboard and fiberboard

Ultrasonic wave velocities were determined at parallel and perpendicular to manufacturing direction and at the interval angles of 15° in clockwise and counterclockwise directions of particleboard and fiberboard. The experimental results were compared with the predicted values using some empirical formulae such as Hankinson and Jacoby equations. The results showed that the ultrasonic wave velocity were the highest in parallel direction in particleboard and fiberboard and decreases with increase of angle and the lowest values occurred in perpendicular direction. The predicted ultrasonic velocity using Hankinson and Jacoby equations are in close agreement with the measured values. Relationship between ultrasonic wave velocities and particles and fibers angle could be successfully presented by cubic and quadratic regression equations as well.     

Dynamic saturation curve measurement for resin flow in glass fibre reinforcement

A methodology is presented to determine the saturation curve of a resin/glass fabric system, during infiltration in a transparent mould under constant flow rate. Video acquisitions are transformed by image analysis into saturation level versus position and time, and coupled to inlet pressure measurements. A numerical multiphase flow model is then used to simulate the infiltration for various combinations of drainage curve parameters. The numerical parameters to describe the saturation and relative permeability are determined by response surface optimization. The drainage curve and relative permeability equations determined at one time are shown to adequately describe the entire injection process, and to be flow-rate dependent.     

Relative measurements of the velocity and attenuation of ultrasound in highly absorbing liquids

It is shown that it is possible to use a continuous sinusoidal signal to make relative measurements of the velocity and absorption coefficient of ultrasound in highly absorbing liquids such as liquid crystals. Compared with the traditional variable-frequency pulse-phase method, the technique described has the advantage of giving a direct reading of the results under dynamic measurement conditions. A block diagram and the characteristics of the equipment for measuring the anisotropy of acoustic parameters by both pulse and continuous methods are presented.Translated from Izmeritel'naya Tekhnika, No. 1, pp. 66–67, January, 1995.