Ultrasonic Shear Wave Research Articles

Monitoring of Acidified Milk Gel Formation by Ultrasonic Shear Wave Measurements. High-Frequency Viscoelastic Moduli of Milk and Acidified Milk Gel

In the present paper we describe the application of the thickness shear mode resonator technique for the measurement of viscoelastic parameters of milk and acidified milk gels in the megahertz frequency range. The technique provides information on the viscoelasticity of milk and milk gels in the time scale of 10–8 to 10–7 s. The length scale of the measurements, determined by the depth of penetration and the wavelength of the shear wave, falls between the submicron and micron range. In milk acidified by glucono-δ-lactone we observed an increase in the high- and low-frequency loss modulus, G”, below pH 5.1, indicating aggregation of casein particles into clusters. There was a sharp rise in high- and low-frequency storage (G′) and loss (G″) moduli between pH 4.85 and 4.7, as a result of gel network formation in acidified milk. Both G″ and G′ of milk gel in the megahertz frequency range are several orders higher than those we obtained at low frequencies (0.02 to 10Hz) using dynamic rheology. The high-frequency (5 to 25MHz) viscosity of milk was found to be the same as at low frequencies. Overall, our results demonstrate the high sensitivity of the ultrasonic shear wave measurements to the changes in the rheological parameters in acidified milk during gelation.

Stress‐induced anisotropy of partially molten media inferred from experimental deformation of a simple binary system under acoustic monitoring

Microstructural changes of partially molten media under deviatoric stress were investigated in a newly developed apparatus by deforming a large sample (a 70‐mm cube) under a uniform pure shear stress. Borneol + melt system having a moderate dihedral angle and texturally equilibrated under hydrostatic stress was used as a partially molten rock analogue. The applied stress was small enough not to involve cataclastic‐plastic deformation of the solid grains. Shear strain rate was about 10−8 s−1, and a stress exponent indicative of diffusion creep was obtained. During the deformation, sample microstructure was observed in situ by means of ultrasonic shear waves. The development of stress‐induced anisotropy was successfully detected by shear wave splitting. The results obtained indicate that grain boundary contiguity in the direction of the least compressive stress (σ3) was reduced with respect to the equilibrium texture and also that the relative values of liquid pressure and σ3 play an essential role for development of anisotropy. The developed anisotropy persisted as long as deviatoric stress was applied, but the initial isotropic structure was recovered by releasing this stress. Several interesting phenomena were involved in the structural change; these include shear creep‐induced dilatancy, strong dependence of the timescale of structural recovery on the amount of deformation (memory effect), and relaxation creep after releasing stress. Scaling considerations using the Griffith theory shows that the structural changes observed in the present experimental system are expected to occur in the Earth as well.

Toward a Sensitive Detection and Sizing of Small Closed Cracks by Ultrasonic Shear Waves(NDE3)

Toward a Sensitive Detection and Sizing of Small Closed Cracks by Ultrasonic Shear Waves(NDE3)

A Condition Monitor For Liquid Lubricated Mechanical Seals

A recently developed condition monitor for liquid lubricated mechanical seals utilizes actively generated ultrasonic shear waves to determine conditions at the sealing interface. A shear wave transducer is mounted on the backside of the non-rotating seal face, and generates waves that propagate toward the sealing interface. The amplitude of the reflected waves indicates whether or not face contact occurs and, if there is contact, the severity of contact. Thus, this monitor is suitable for use with both non-contacting and partially contacting seals. Laboratory tests on a commercial, unbalanced seal demonstrate the effectiveness of the approach. Presented at the 56th Annual Meeting Orlando, Florida May 20–24, 2001

F-1112 超音波パルスエコー法によるき裂閉口圧の評価(J25-3 欠陥・き裂)(J25 機械力学,材料力学,エンジン関連の計測技術)

This paper describes a new methodology for evaluation of small cracks in steel plates together with their closure stresses. Surface connected back-wall cracks of size ranging 0.31 to 3.45 mm in steel specimens are considered here. Crack corner echo of ultrasonic shear wave beam of 50° incidence in material is used for this study. Firstly the ultrasonic echo response of open crack is determined as a function of crack size. The crack corner echo based on changing the crack closing stress is analyzed and a relation between them is determined. Based on these relations, crack size and crack closing stress of an unknown closed crack are determined by appropriate inverse analysis of the response of the crack. The method shows a good capability for the evaluation of crack size as well as crack closing stress quantitatively.

Nondestructive Characterization of Planar Defects Using Laser-Generated Ultrasonic Shear Waves

Nondestructive Characterization of Planar Defects Using Laser-Generated Ultrasonic Shear Waves

Hydration of cementitious materials by pulse echo USWR: Method, apparatus and application examples

In this paper, a novel nondestructive method based on a pulse echo ultrasonic shear waves reflection (USWR) technique is described. The method is implemented in a home-built field testing apparatus of which construction and operating principles are briefly explained. With the instrument, the time dependence of the reflection coefficient r due to the hydration of cementitious materials is measured automatically with the result continuously displayed and recorded. The changes of the reflection coefficient Δr with time are related to the changes of the viscoelastic properties, in particular to the dynamic shear modulus G of the material investigated. From the application examples on selected cementitious materials shown, the sensitivity of the method and of the apparatus to different parameters (composition, water/solid ratio, fineness, addition of additives, aging) is evident. Possible practical applications are nondestructive measurements of the shear rigidity of the fragile CHS structures with no external shearing applied and cement setting time determinations.

Measuring Newtonian viscosity from the phase of reflected ultrasonic shear wave

In this paper, an acoustic shear impedance model is employed to obtain a relation between the viscosity of a Newtonian fluid and phase characteristics of ultrasonic shear wave reflection from a solid–fluid interface. The phase and magnitude of the reflection coefficient can be decoupled in this model. The decoupling allows an independent relation between the acoustic shear impedance (viscosity–density product) and phase of the reflection coefficient. The model was experimentally verified for different fluid–solid combinations. Comparison of the results with the commonly used absolute reflection coefficient method demonstrates that phase measurement provides improved measurements.

Ultrasonic measurement of the elastic constants of sodiump-nitrophenolate dihydrate single crystals

Sodium p-nitrophenolate dihydrate single crystals possess excellent nonlinear optical properties such that they can be used for optical second-harmonic generation. It belongs to the orthorhombic system with the space group Ima2. Slow evaporation or slow cooling techniques can be used to grow good optical quality single crystals from supersaturated solution. All the nine elastic constants of this crystal have been measured using an ultrasonic technique. Samples for measurements have been cut along desired crystallographic axes and the pulse echo overlap technique has been used to measure longitudinal and shear ultrasonic wave velocities along appropriate symmetry directions in the crystal. The McSkimin Delta t criterion has been applied to determine the round trip travel time accurately, from which the nine elastic constants have been evaluated. Temperature variation of selected elastic constants in a limited range have also been measured and reported.

Silicate perovskite analogue ScAlO 3: temperature dependence of elastic moduli

The elastic moduli of ScAlO 3 perovskite, a very close structural analogue for MgSiO 3 perovskite, have been measured between 300 and 600 K using high precision ultrasonic interferometry in an internally heated gas-charged pressure vessel. This new capability for high temperature measurement of elastic wave speeds has been demonstrated on polycrystalline alumina. The temperature derivatives of elastic moduli of Al 2O 3 measured in this study agree within 15% with expectations based on published single-crystal data. For ScAlO 3 perovskite, the value of (∂ K S/∂ T) P is −0.033 GPa K −1 and (∂ G/∂ T) P is −0.015 GPa K −1. The relative magnitudes of these derivatives agree with the observation in Duffy and Anderson [Duffy, T.S., Anderson, D.L., 1989. Seismic velocities in mantle minerals and the mineralogy of the upper mantle. J. Geophys. Res. 94, 1895–1912.] that |(∂ K S/∂ T) P| is typically about twice |(∂ G/∂ T) P|. The value of (∂ K S/∂ T) P for ScAlO 3 is intermediate between those inferred less directly from V( P, T) studies of Fe-free and Fe- and Al-bearing MgSiO 3 perovskites [Wang, Y., Weidner, D.J., Liebermann, R.C., Zhao, Y., 1994. P– V– T equation of state of (Mg,Fe)SiO 3 perovskite: constraints on composition of the lower mantle. Phys. Earth Planet. Inter. 83, 13–40; Mao, H.K., Hemley, R.J., Shu, J., Chen, L., Jephcoat, A.P., Wu, Y., Bassett, W.A., 1991. Effect of pressure, temperature and composition on the lattice parameters and density of (Mg,Fe) SiO 3 perovskite to 30 GPa. J. Geophys. Res. 91, 8069–8079; Zhang, Weidner, D., 1999. Thermal equation of state of aluminum-enriched silicate perovskite. Science 284, 782–784]. The value of |(∂ G/∂ T)| P for ScAlO 3 is similar to those of most other mantle silicate phases but lower than the recent determination for MgSiO 3 perovskite [Sinelnikov, Y., Chen, G., Neuville, D.R., Vaughan, M.T., Liebermann, R.C., 1998. Ultrasonic shear wave velocities of MgSiO 3 perovskite at 8 GPa and 800K and lower mantle composition. Science 281, 677–679]. Combining the results from the previous studies and current measurements on ScAlO 3 perovskite, we extracted the parameters ( q and γ 0) needed to fully specify its Mie–Grüneisen–Debye equation-of-state. In this study, we have demonstrated that acoustic measurements of K S( T), unlike V( P, T) data, tightly constrain the value of q. It is concluded that ScAlO 3 has ‘normal’ γ 0 (∼1.3) and high q (∼3.6). The high value of q indicates that ScAlO 3 has very strong intrinsic temperature dependence of the bulk modulus; similar behaviour has been observed in measurements on Fe- and Al-bearing silicate perovskites (Mao et al., 1991; Zhang and Weidner, 1999).

Liquid–vapor critical behavior of neon confined in aerogel

We have used an acoustic technique to study the critical behavior of neon confined in a 95% porosity silica aerogel grown in the 10 μm channels of a glass capillary array. Shear and longitudinal ultrasonic waves showed large velocity dips and attenuation peaks due to the diverging compressibility near the critical point. Confinement in the aerogel lowers the critical temperature slightly and appears to narrow the coexistence region.

Calculations of ultrasonic ray trajectories in the case of transverse testing of a pipe wall by shear waves

Analytical expressions for determining parameters of zigzag trajectories of ultrasonic shear waves propagating in a pipe wall taking account of the pipe curvature, slant angle of the emitter coupled through a prism, characteristics of the coupling prism material and those of the tested object have been derived. The expressions are necessary for engineering estimates of basic technological characteristics of ultrasonic systems for testing thick-wall pipes.

High frequency dynamic shear rheology of honey

Our objective was to measure the high-frequency dynamic shear rheology of honey using ultrasonic spectrometry. The complex shear reflection coefficient of honey was determined over a range of frequencies (5–15 MHz) by measuring the phase and amplitude of ultrasonic shear waves reflected from its surface. The dynamic shear modulus and dynamic viscosity of the honey were determined from the measured reflection coefficient and density. For honey samples diluted with different amounts of water there was a strong correlation between the viscosity measured at high shear-rate (10 MHz) using ultrasound and that measured at low shear rate (0.1 s −1) using a Couette viscometer. Nevertheless, the viscosity was significantly lower at high shear-rates than at low shear rates, which indicated the existence of one or more relaxation mechanisms. Our results show that ultrasonic spectrometry can be used to non-destructively and non-invasively measure the high frequency shear rheology of honey samples, which may be useful for quality control of honey and other viscous products.

High-resolution longitudinal and shear wave spectroscopy for analysis of complex colloids

In the present paper we describe the applications of the high-resolution ultrasonic longitudinal and shear wave resonator techniques for food and bio-colloids. Our longitudinal wave technique allows us to measure the velocity and attenuation of ultrasonic waves with a resolution of 0.0001% for ultrasonic velocity and 0.1% for the ultrasonic attenuation in small volumes (0.1 to 1 ml) in the frequency range 4–20 MHz. The shear wave technique provides information on viscoelastic parameters of liquids and gels in the frequency range 4–25 MHz. Both techniques allow continuous, temperature ramp and automatic titration measurements for analysis of various processes in complex colloids. Examples of the application of both techniques for studying heat-induced milk coagulation, phase transitions in milk fats, acid milk gelation, and the detection of food pathogens are described. Combination of both techniques shows a high sensitivity to various processes, e.g., pregelation and gelation, in food colloids and provides the unique ability to evaluate simultaneously the changes in volume and shear viscoelastic moduli. Overall our ultrasonic measurements demonstrate their high potential for nondestructive analysis of complex food and bio-colloids.

Line source representation for laser-generated ultrasound in aluminum

Modeling the ultrasound generated by a laser source is critical for using noncontact laser-generated ultrasonic systems for the characterization of material properties. In this work, a laser line source was modeled and verified experimentally by measuring the ultrasonic shear wave signal generated in aluminum with a broadband laser generation/electromagnetic acoustic transducer (EMAT)-detection system. Results of calculations and experiments show that the amplitude directivity of a laser line source is identical to that of a point source in the plane perpendicular to the line axis while the temporal dependence differs.

Ultrasonic measurements related to evolution of structure in curing epoxy resins

The tracking of the cure of epoxy adhesives and the assessment of the cure state of adhesive bondlines joining engineering components are important for quality assurance during manufacture and for the safe functioning of manufactured assemblies in the field. Ultrasound can be used to give estimates of the compression modulus of curing and cured materials and thereby provide a means to assess non-destructively the cure state of adhered joints during manufacture and in service. These techniques are at present difficult to apply and are predominantly empirical in that little is known about the relationships between the measured ultrasound data and the evolving molecular structure of the adhesive as it cures. The present paper describes the application of a group of physical techniques that can be used to characterise the polymer structure during cure, with the aim of relating these to phenomena measurable by ultrasound. Wide angle X-ray scattering (WAXS) provides a basic measure of polymer chain formation, which is seen to correlate closely with the compression modulus as it develops during cure. Low resolution nuclear magnetic resonance (NMR) provides a means to observe the mobility of bound hydrogen nuclei and thereby to track the change in state of a resin– hardener system from a viscous liquid to a crosslinked solid. The NMR data obtained during cure correlated well with compression modulus development. Ultrasonic shear wave spectrometry indicates when a curing material can first support shear motions and this agrees well with NMR data and with specifications of gel point given by manufacturers. Ultrasonic compression wave absorption data provide frequency dependent patterns that change during the cure cycle and that can be explained on the basis of the results of the WAXS, NMR, and shear wave experiments. These changing patterns have potential for tracking cure using low cost ultrasonic techniques, the results of which can be related to phenomena taking place on a molecular scale.

Acoustic Vibrational Properties and Fractal Bond Connectivity of Praseodymium Doped Glasses

The velocities of longitudinal and shear ultrasonic waves propagated in the (Pr2O3)x(P2O5)1-x glass system, where x is the mole fraction of Pr2O3 and (1 - x) is the mole fraction of P2O5, have been measured as functions of temperature and hydrostatic pressure. The temperature dependencies of the second order elastic stiffness tensor components (SOEC) CS IJ , which have been determined from the velocitydata between 10 and 300 K, show no evidence of phonon mode softening throughout the whole temperature range. The elastic stiffnesses increased monotonically, the usual behaviour associated with the effect of the phonon anharmonicityof atomic vibration. At low temperatures, strong phonon interactions with two-level systems have been observed. The ultrasonic wave attenuation of longitudinal and shear waves is dominated bya broad acoustic loss peak whose height and peak position are frequencydependent. This behaviour is consistent with the presence of thermally activated structural relaxation of the two-level systems in these glasses. The fractal bond connectivity of these glasses, obtained from the elastic stiffnesses determined from ultrasonic wave velocities, has a value between 2.32 to 2.55, indicating that their connectivitytends towards having a threedimensional character. The hydrostatic pressure dependencies of longitudinal ultrasonic waves show a slight increase with pressure. As a consequence, the hydrostatic pressure derivatives ( CS11/ P)P=0 of the elastic stiffness CS11/ and (BS/P)P=0 of the bulk modulus BS of (Pr2O3)x(P2O5)1-x glasses are positive. The bulk modulus increases with pressure, and thus these glasses stiffen under pressure, which is associated with the normal elastic behaviour. The GrÜneisen parameter approach has been used to quantifythe vibrational anharmonicityof the long-wavelength acoustic phonons in these glasses.

Applications of ultrasonic reflection mode conversion transducers in NDE

Linearly polarized ultrasonic shear waves constitute a privileged tool for investigation in the field of mechanical behavior of materials and metallic structures as well as for the determination of acoustical properties of porous materials. These waves are often generated by a piezoelectric plate vibrating in a direction perpendicular to its thickness. However, this way of production presents some difficulties to obtain a perfectly linear polarization. To palliate to this inconvenience, shear waves can be generated by the mode-conversion of a longitudinal wave. This paper deals with the principle and some applications of two types of mode conversion transducers which permit transmitting and receiving shear waves obtained by reflection mode-conversion. These transducers are made up with straight ultrasonic probes coupled, by contact, to acoustic delay lines (or relays) of different geometry. The first type of transducer uses an acoustic relay or delay line of big length. When it is buried in a recipient containing dry sand, it permits the detection of external mechanical disturbances as vibrations and transient shocks. The second type of transducer, for which the delay line has a reduced length, is used for the detection of material anisotropy and for the study of the polarization direction of conventional normal incidence shear wave transducers.

Ultrasonic measurement of stress in railroad wheels

The equipment described here generates ultrasonic shear waves using an electromagnetic-acoustic transducer. Precise measurement of the velocity of two orthogonally polarized signals determines the birefringence and allows the calculation of stress. It is necessary to account for the effect of metallurgical texture which can contribute to the birefringence and appear as moderate stress. This system sends a signal through the thickness of a railroad wheel rim, digitizes the first echo, locks onto a cycle, and calculates the time when it crosses zero amplitude. Signal averaging yields the arrival time of a signal at about 90 μs with a standard deviation of 2–4 ns. In screening the residual stress in the rims of cast-steel railroad wheels, this system has a total error of ≈±60 MPa; most of this is due to variability of the texture measured in several stress-relieved blocks cut from wheels. The initial measurements were on wheels in which the manufacture had induced known levels of thermal damage. Results from destructive radial saw cuts through the rims allowed qualitative evaluation of the nondestructive measurements. Most components in this equipment are commercially available.

TOMOGRAPHY OF STRESS TENSOR FIELD BY ACOUSTIC ELASTICITY

The algebraical tomographic reconstruction algorithm of the stress tensor field for the inhomogeneous stress-strain state is presented. This problem is more complicated than traditional scalar fields tomography and it has not been solved yet.The phenomenological linear dependences between relative variation of velocity of ultrasonic shear-waves and stress tensor components in the case of small effects of acoustic elasticity have been chosen as initial correlations. Finally, the determination of spatial distribution of the stress tensor field for inhomogeneous stress-strain state is reduced to a solution of linear algebraical equations for the stress tensor components in each cell. The important advantage of the presented algorithm is its simplicity of its application.