Ultrasonic Velocity Method Research Articles

Effect of heat pressing on the mechanical properties of a mica-based glass-ceramic.

Previous work has shown that heat pressing of mica-based glass-ceramics can lead to crystal alignment along the direction of pressing. The purpose of this study was to evaluate the effect of heat pressing on the fracture toughness of mica-based glass-ceramics. Glass rods (12 x 60 mm) were prepared by melting the glass composition at 1400 degrees C for 2 h. Ingots (12 x 12 mm; n = 5) and discs (12 x 1.5 mm; n = 10) were cut from the rods. The discs were heat treated to simulate heat pressing and served as controls. A machinable mica-based glass- ceramic (Dicor MGC) also served as control. Bar-shaped wax patterns (2 x 4 x 22 mm) were invested and heat pressed at 875 degrees C. The elastic constants were determined with the use of the pulsed ultrasonic velocity method. The fracture toughness was measured by the indentation strength technique. The degree of texture was assessed qualitatively by X-ray diffraction and quantitatively on digital SEM micrographs. The results showed that the mean fracture toughness of the heat-pressed specimens (1.96 +/- 0.19 MPa. m(0.5)) was significantly higher than that of the heat-treated controls (1.51 +/- 0.21 MPa. m(0.5)) or the proprietary mica glass-ceramic (Dicor MGC; 1.66 +/- 0.04 MPa. m(0.5)) (p <.001). It was concluded that heat pressing led to a significant increase in fracture toughness in mica glass-ceramics because of crystal alignment along the direction of pressing.

Miscibility studies of epoxy/unsaturated polyester resin blend in chloroform by viscosity, ultrasonic velocity, and refractive index methods

AbstractMiscibility studies of blends of epoxy with unsaturated polyester resin in chloroform were carried out by viscosity, ultrasonic velocity, and refractive methods at 30°C. By using viscosity data, the interaction parameters were computed, which indicated that epoxy/unsaturated polyester resin blends were miscible. The miscibility was further confirmed by the ultrasonic velocity and refractive index methods. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2970–2972, 2003

Aplicação de ondas ultra-sônicas na detecção das primeiras fissuras em vigas de concreto armado e na avaliação da resistência à compressão

The ultrasonic waves velocity method is a technique that is related to the propagation of the waves through the material that is being evaluated. It is considered a nondestructive test and can also be utilized to evaluate the quality of the concrete. Through this method it is possible, for example, to obtain the thickness of concrete slabs and to estimate the strength of concrete. This research aims to present results obtained though the application of ultrasonic waves propagation method in the detection of the first cracks in strengthened concrete beams (solicitadas à flexão simples). The method is also used to evaluate the strength of concrete during the first days. The results show that the method can be used to estimate the strength of concrete and, if correctly used, can be useful in strenghtened concrete beams tests to detect first cracks.

Density and ultrasonic velocity of undersaturated and supersaturated solutions of fluoranthene in trichloroethylene, and study of their metastable zone width

The density ( d) and ultrasonic velocity ( u) of undersaturated, saturated and supersaturated solutions of fluoranthene in trichloroethylene have been measured with the help of two microprocessor instruments. Moreover, the same instruments and an apparatus for measuring transparency and turbidity were used to investigate the metastable zone width, as well as the solubility of fluoranthene in this solvent. It was found that the temperature dependencies of both the density and ultrasonic velocity in the range of undersaturation and supersaturation may be described by first-order equations. In the undersaturation range, the density linearly decreases and the ultrasonic velocity linearly increases with an increase in solution concentration. The second-order equations relating these quantities to solution supersaturation can satisfactorily be used for describing the data. Moreover, the first precipitation temperatures ( T p) determined from the density, ultrasonic velocity and transparency measurements as well as the metastable zone widths (Δ Θ max) are strongly dependent on the detection manner of the onset of crystallisation. Their mean values are 12.58, 5.76 and 4.62 K for density, ultrasonic velocity and transparency methods, respectively. This parameter was assessed as a function of cooling rate ( b). Hence, the linear dependence between log b and log (Δ Θ max) was established. The solubility temperature of fluoranthene determined from the change in turbidity of solution is generally lower by about 3 K than those measured with the help of the synthetic–dynamic method.

Ultrasonic characterization of Atlantic mackerel ( Scomber scombrus)

The influence of frequency (1–6 MHz), temperature (5–25°C) and composition on the ultrasonic velocity and attenuation coefficient of Atlantic mackerel (Scomber scombrus) was investigated. The ultrasonic velocity was insensitive to frequency, whereas the attenuation coefficient increased with frequency. The fat, water and solids-non-fat content of mackerel tissue was determined by analyzing the temperature dependence of the ultrasonic velocity in the tissue using a semi-empirical equation. There was good agreement between the fat, water and solids-non-fat content determined by ultrasonic velocity and proximate analysis methods. In particular, there was a high correlation between the two methods for the determination of fat content ( r 2 =0.949). There was no correlation between the composition of mackerel tissue determined by ultrasonic attenuation and proximate analysis methods. The increase in ultrasonic attenuation of mackerel with temperature, especially above about 20°C, was attributed to protein denaturation and tissue disruption.

Fiber packing and elastic properties of a transversely random unidirectional glass/epoxy composite

Image analysis was used to characterize the microstructure of a unidirectional glass/epoxy composite which was found to be transversely randomly packed. Starting from a measured distribution of fiber diameter, a Monte Carlo procedure was employed to generate periodic computer models with unit cells comprising of random dispersion of a hundred non-overlapping parallel fibers of different diameter. The morphology generated in this way showed excellent agreement with that of the actual composite studied. An ultrasonic velocity method was used to measure a complete set of composite elastic constants and those of the epoxy matrix. On the basis of periodic three-dimensional meshes, the composite elastic constants of the Monte Carlo models were calculated numerically. Numerical and measured elastic constants were in good agreement. It was shown numerically that the randomness of the composite microstructure had a significant influence on the transverse composite elastic constants while the effect of fiber diameter distribution was small and unimportant. The predictive potential of the Halpin-Tsai and some other models commonly employed for predicting the elastic behavior of unidirectional composites was also assessed.

Acoustic emission and ultrasonic-velocity methods used to characterise the excavation disturbance associated with deep tunnels in hard rock

Acoustic emission (AE) and ultrasonic-velocity monitoring studies have been undertaken at both the Atomic Energy of Canada Limited (AECL) Underground Research Laboratory (URL) and at the Swedish Nuclear Fuel Waste Management Company (SKB) Hard Rock Laboratory (HRL). At both locations the excavations were tunnels in granitic material at approximately 420 m depth. However, the stress regime was more severe at the URL Mine-by tunnel site than the HRL ZEDEX tunnel. Different parts of the ZEDEX tunnel were created using different excavation techniques. Using AE and ultrasonic techniques to study these tunnels we have been able to examine the nature of the excavation-disturbed zone around the tunnel, as well as examining the effects of different stress regimes and excavation techniques. Studies were undertaken both during and after the Mine-by tunnel excavation and during excavation in the ZEDEX tunnel. AE monitoring in the wall of the Mine-by tunnel during excavation showed that some activity occurred in the sidewall regions, but the spatial density of AE hypocentres increased toward the regions in the floor and roof of the tunnel where breakout notches formed. This sidewall activity was clustered primarily within 0.5 m of the tunnel wall. AE monitoring in the floor of the tunnel showed that small numbers of AE continued to occur in the notch region in the floor of the tunnel over 2 years after excavation was completed. This activity became more acute as the rock was heated, imposing thermally induced stresses on the volume. Ultrasonic-velocity studies both in the floor and the wall of the tunnel showed that the velocity is strongly anisotropic with the direction of slowest velocity orthogonal to the tunnel surface. The velocity increased with distance into the rock from the tunnel surface. In the floor, this effect was seen up to 2 m from the tunnel surface. Most of the change occurred within the first 0.5 m from the tunnel perimeter. At the lower-stress HRL, most of the AE again occur very close to the tunnel surface. The occurrence of AE under relatively low stress conditions suggests that the regions experiencing AE activity were damaged during the excavation process, thereby reducing their strength. The section of tunnel excavated by a tunnel-boring machine had fewer events, clustered much closer to the tunnel surface, than the sections excavated using drill and blast excavation techniques. P-wave velocity changes of only about 0.1% were experienced due to the tunnel excavation for ray paths within zero to 2 m from the tunnel surface indicating that crack damage was relatively low.

Physical Methods for Characterizing Wood Composite Panel Products

Physical methods have been used to compare the mechanical properties of wood based panel products in relation to their microstructure. Three types of composites were considered: medium density fiberboard (MDF), oriented strandboard (OSB) and chipboard (CB). The overall elastic properties of panels were assumed to be orthotropic. The diagonal terms of stiffness matrix were determined with ultrasonic velocity method. The properties of the skin and the core of the panel were characterized using X-ray microdensitometry, ultrasonic velocity measurements, dynamic thermo-mechanical analysis (DMTA) and low voltage scanning electron microscopy (LVESEM). Clear differences have been established in the physical properties of the three panel products. Average mechanical properties have shown that the highest anisotropy is in OSB and the lowest in CB. Always the mechanical characteristics of the skin are higher than average characteristics of the panels while that of the core are inferior to average characteristics. E elastic modulus is much more higher (2 to 5 times) in the skin than in the core. X-ray microdensitometric technique has shown that the heterogeneity in the skin and core is the highest in OSB.

On‐Line Particle Size Analysis Using Ultrasonic Velocity Spectrometry

A new method is described for the determination of particle size distribution of slurries based on ultrasonic velocity spectrometry combined with gamma‐ray transmission. This method shares the advantages of ultrasonic attenuation spectroscopy of being capable of analyzing highly concentrated samples without dilution. However the ultrasonic velocity method is better suited to fine particles of diameter from about 0.1 to 30 μm, a greater volume of slurry is analysed and therefore sampling errors are reduced, and precise theoretical models are readily available to permit the accurate determination of size distribution by inversion of ultrasonic velocity measurements. The method can also be used to accurately determine particle size cut points by linear correlation. Using either inversion or correlation methods, the accuracy of particle size information from ultrasonic velocity spectroscopy is significantly enhanced by the independent measurement of solids loading by gamma‐ray transmission. In addition, larger sizes can be measured by combining the ultrasonic velocity method with ultrasonic attenuation measurements. The method has been tested in the laboratory on a wide variety of mineral and paint slurries. The method determined the size distribution of single component silica and alumina samples in water in agreement with laser diffraction measurements and the method successfully distinguished well and poorly dispersed TiO2 suspensions. For composite samples the method discriminated separate TiO2 and CaCO3, components and determined their proportions to within 0.25% volume. In addition the method, in combination with ultrasonic attenuation measurements, determined the size fractions of iron ore slurries below 10 and 30 μm to within 1.3% and 1.0% relative respectively, when compared with laser diffraction measurement of particle size. The CSIRO is presently designing an industrial gauge which will be manufactured and installed in an industrial slurry stream in 1997.

Measuring the fibre orientation and modelling the elastic properties of injection-moulded long-glass-fibre-reinforced nylon

This paper describes the characterisation of the 3D fibre orientation of a single-gated injection-moulded plaque of short-glass-fibre-reinforced Nylon by image analysis, and the use of this orientation data for the theoretical prediction of the composite elastic properties. Fibre orientations were measured by using a purpose built image analysis facility, which allows 3D data to be obtained. Composite elastic properties were measured by an ultrasonic velocity method and compared with theoretical predictions obtained from the modelling techniques of Wilczynski and Ward.

Determination of the moduli of elasticity of rocks. Comparison of the ultrasonic velocity and mechanical resonance frequency methods with direct static methods

In the present investigation, dynamic methods for the determination of moduli of elasticity were compared with direct static methods. The dynamic moduli of rocks, such as Young's modulus (E) and Poisson's ratio (v) were determined, using both mechanical resonance frequency and classic P and S wave ultrasonic velocity techniques. For this purpose rock samples from different areas of France, covering a wide range of velocity values, were used. The mechanical resonance frequencies were investigated using a Grindo-Sonic machine while the P and S wave ultrasonic velocities were measured using a Pundit ultrasonic machine, connected to an oscilloscope. The static moduli were determined using deformation gauges. Statistical interpretation of the test results indicated significant correlation between these dynamic and static methods. Accordingly, the above non-destructive dynamic methods are suitable for the determination of static moduli of elasticity.

46876 The pulsed ultrasonic velocity method for determining material dynamic elastic moduli : Blessing, G.V. Dynamic Elastic Modulus Measurements in Materials, ASTM STP 1045. Edited by A. Wolfenden. pp. 47–57. American Society for Testing and Materials, Philadelphia, Pennsylvania (United States)

46876 The pulsed ultrasonic velocity method for determining material dynamic elastic moduli : Blessing, G.V. Dynamic Elastic Modulus Measurements in Materials, ASTM STP 1045. Edited by A. Wolfenden. pp. 47–57. American Society for Testing and Materials, Philadelphia, Pennsylvania (United States)

45601 Pulsed ultrasonic velocity method for determining material dynamic elastic moduli : Blessing, G.V. National Institute of Standards, and Technology (NEL), Gaithersburg, Maryland (United States), PB90-241290, 11 pp. (1990)

45601 Pulsed ultrasonic velocity method for determining material dynamic elastic moduli : Blessing, G.V. National Institute of Standards, and Technology (NEL), Gaithersburg, Maryland (United States), PB90-241290, 11 pp. (1990)

Characterization of anisotropy in wood composites

The aim of this report is to study the anisotropic behavior of wood composites using the ultrasonic velocity method and acoustic emission method. Velocities of ultrasonic longitudinal and transversal waves were used for the estimation of five elastic constants. Complementary, stimulated acoustic emission, induced by breaking 0.5-ram pencil lead on the surface of the specimen, was employed to measure five parameters of the acoustic emission signal (duration, counts number, energy, amplitude, and rise time). The anisotropy was estimated as the ratio of velocities, of acoustic invariants, and acoustic emission parameters.

Review of ultrasonic velocity methods of determining residual stress : Rumble, S.J.; Sparrow, J.G. Aeronautical research laboratories, Melbourne (Australia), AD-A160-769, vp (May 1985)

Abstract : Residual stress is the stress remaining in a body when all external forces have been removed. Residual stresses can occur as a result of fabrication, assembly, load history, heat treatment or welding. They may be compressive or tensile, and often contribute to the occurrence of component failure. The contribution of these stresses to premature structural failure has long been recognized. However their measurement has usually been difficult and in many cases not possible. Recognition of the benefits of knowing the value of residual stresses has led to recent efforts to improve the capability of known methods of measuring them and to the development of new techniques. The residual stresses in a body can be divided into two classes depending on the extent of the stress. In typical engineering materials, residual microstresses extend over a few grains, whereas residual macrostresses which are most amenable to the practical measurement methods discussed in this paper. It notes that while velocity methods have not been refined to the stage of practical use, they show considerable promise. The theoretical basis, and the experimental techniques of the ultrasonic methods are reviewed with emphasis on the separation of the competing effects of texture and stress on ultrasonic velocity. Keyword: Australia.

Elastic constants of a graphite-magnesium composite

This study contains three components: measurement, modeling, and inverse modeling to get the fiber elastic constants. The studied composite consisted of 70 vol % continuous uniaxial graphite fibers in a magnesium matrix. By ultrasonic-velocity methods, we measured the composite’s complete orthotropic-symmetry (nine-independent-component) elastic-constant tensor: Cij in Voigt contracted notation. Approximately, the composite shows transverse-isotropic symmetry. For a model, we used a wave-scattering method in the long-wavelength limit. The model requires two inputs: the two isotropic matrix elastic constants and the five anisotropic fiber elastic constants. We measured the first and guessed the second based on graphite-fiber elastic constants reported by others. This guess gave good measurement-model agreement only for C11, C22, and C33. Especially, the shear moduli Cii (i=4,5,6) agreed poorly (a 20% difference). Using inverse modeling—calculating fiber properties from measured matrix properties and measured composite properties—we estimated the anisotropic fiber elastic constants. For the fiber we predict a Young-modulus anisotropy of 12 and a principal Poisson ratio range of 0.03–0.37.

Non-destructive approach for analysing the germinability of acorns

A novel application of the ultrasonic velocity method is proposed to separate germinated and non-viable acorns and in this way to predict their germinability, based on morphological (dimensions of two axes) and physical criteria (density, ultrasonic velocity, impedance and acoustic stiffness). All specimens were 6 months old. They had an average trading quality, and were characterized by a high ratio (50%) of non-viable acorns. Relationships between morphological and physical characteristics were established. Experimental advances have been accomplished in the understanding of acoustical parameters able to predict the germinability, using statistical principal-component analysis. Germinability is related to density and ultrasonic velocity. A high density and a high velocity characterize a viable acorn.

繊維配向の新しい測定法

For a check of the quality of fiber sheets it is essentially to determine the orientation of molecules. The molecular orientation of fiber sheets is usually investigated by such techniques as X-ray diffraction, birefringence, mechanical breaking strength, Young's modulus, and ultrasonic velocity methods. These methods, however, require a long time for the determination of orientation.We have developed a New Type of Apparatus Microwave Molecular Orientation Analyzer for determining the molecular orientation of fiber sheets in such a short time as ca. 60sec and for determining complex dielectric constant at microwave frequencies. The new type of apparatus by use of microwaves was applied for determining molecular orientation of the paper sheets and plastic films. The results obtained by the present microwave method are supported by those from the mechanical breakling strength and infrared mothods. This new method has characteristics of non-contact, non-destruction and quick measurements, and lends itself most readily to the measurements of a number of samples.

An ultrasonic method for measuring the elastic constants of wood increment cores bored from living trees

Three stiffness moduli and three shear moduli were determined using an ultrasonic velocity method for 5 mm diameter increment cores bored from living beech trees. The validity of the method was assessed by comparing the results for the increment cores with those for standard specimens loaded in static bending and on cubes tested with ultrasonic transverse waves. Good correlation was found between the elastic constants of the cores and standard specimens. It was noted that the regression equation between the modulus of rupture and the longitudinal stiffness modulus for cores, or between the modulus of rupture for standard specimens and longitudinal velocity in cores, permits one to predict the strength of living tree wood through a simple ultrasonic test. The technique is capable of rapidly detecting the differences between individual characteristics of living trees.

Ultrasonic Studies in N-(p-n-butoxybenzylidene)-p-n-butylaniline

Abstract The ultrasonic velocity in the SG(SH), SB, SA, Nc , N0 and isotropic liquid phases of N-(p-n-butoxybenzylidene)-p-n-butylaniline (BBBA) has been measured as a function of temperature. A transition in the nematic phase seems to indicate the existence of an ordinary nematic and a cybotactic nematic phase. The transition SG-SB has been found for the first time with the ultra-sonic velocity method. The adiabatic compressibility βad and the molar sound velocity Rn (Rao number) have been determined using the experimental density and ultrasonic velocity.