Reflection Of Ultrasonic Waves Research Articles

Geophysical Monitoring Techniques for Underwater Landslide in 1g Models

Underwater landslides along coastal regions can be considerably large and yield many potential hazards. Many laboratory experiments have been carried out by modeling submerged landslides to understand their failure mechanisms and to develop useful design and construction concepts in an attempt to overcome these problems. This paper presents the implementations of three high resolution geophysical techniques including electrical resistance profile, ultrasonic compressional wave reflection imaging, shear wave geotomography, and a pressure-based method to investigate lab-scaled submerged mass movements of layered soil specimens. Electrical resistance profiles of a soil mass obtained by inserting an electrical resistance probe provide the spatial distribution of soil layers. Ultrasonic reflection images based on the acoustic impedance mismatch between materials are applied to detect layers and landslides with sub-millimeter resolution. Pixel-based images of underwater landslides are created by the inversion of the boundary information derived from the travel times of shear waves. The changes of vertical total stress caused by landslides are detected by using flexible stress sensors in the pressure-based method. The experimental results show that the electrical resistance, ultrasonic wave imaging, and total stress change can provide complementary information, and their associations with a shear wave velocity tomography image provide a better understanding of underwater landslides. This study suggests that these geophysical techniques may be effective tools for the investigation of underwater landslides simulated by a shaking table and centrifuge testing.

Observation of Cement Paste Microstructure Evolution

During early hydration in fresh concrete, the cement paste hardens and bonds the aggregates together to make a solid concrete mass. During this process, along with chemical reactions, physical changes in the cement paste at the microlevel and the nanolevel also play major roles in the development of the properties of the concrete. An attempt was made to study the microstructure of cement paste and the evolution of its corresponding elastic modulus during setting. For this purpose, two different in situ testing methods, scanning electron microscopy (SEM) with a Quantomix capsuling system and a nondestructive one-sided ultrasonic technique, ultrasonic wave reflection method, were used. The features in the SEM images were quantified by the use of image analysis techniques, and quantitative analysis was used to examine the relationship between the microstructure of the cement paste and the corresponding dynamic shear modulus during the initial and final setting times. Cement particle growth, motions, and rotations were observed during the evolution of the microstructure of the cement paste. A good correlation between solid-phase and elastic modulus developments was observed after 6 h of mixing for all three pastes tested. Finally, it has been concluded that in situ studies of the microstructures of fresh cement paste can greatly enhance knowledge of the development properties of concrete at an early age.

Ultrasonic Wave Reflection and Resonant Frequency Measurements for Monitoring Early-Age Concrete

Various methods of nondestructive testing offer the opportunity to understand hydration of cement-based materials. In particular, the ultrasonic wave reflection method does not require access to two sides of a structural member and can be performed continuously and on site. This advantage is very significant when estimating the in situ compressive strength of early-age concrete. However, it is also necessary to understand which properties are measured by the ultrasonic wave reflection method and compare the measurements with other testing methods. This paper demonstrates the nature of these measurements with the wave reflection method by comparing the results of the other nondestructive testing method using resonant frequencies.

Using ultrasonic wave reflection to measure solution properties

Ultrasonic wave reflection coefficients of aqueous solutions were measured using high-impact polystyrene as a buffer material to provide enhanced sensitivity over metal or ceramic buffer materials. The wave reflection values showed linear reduction when the concentration of chemical species in solution was increased, but a distinct relation between concentration and reflection coefficient was obtained for each solute species tested. However, more unified relationships were observed between reflection coefficient and other solution parameters – solution density, acoustic impedance, and P-wave velocity – that were consistent for all solution species. Based on this behavior an expression to compute solution density solely from reflection coefficient is derived, which can be applied to estimate solution density in solutions of unknown solute species and concentration when other measurements, such as wave velocity, are not possible.

Comparison between two ultrasonic methods in their ability to monitor the setting process of cement pastes

This paper presents the comparison between ultrasonic wave transmission (USWT) method and ultrasonic wave reflection (USWR) method in their ability to monitor the setting process of cement pastes. The velocity of ultrasonic longitudinal waves and shear wave reflection coefficient were measured simultaneously on cement pastes with different hydration kinetics. Even though both methods are able to reliably monitor the hydration process and formation of structure of an arbitrary cement paste, they monitor the setting process in different ways. The relationship between the velocity of longitudinal waves and shear wave reflection coefficient can be simplified into three characteristic phases and the end of the first phase can be used to define the beginning of the setting process of cement paste.

Computing porosity of cancellous bone using ultrasonic waves, II: The muscle, cortical, cancellous bone system

Based on a model and an algorithm proposed previously by Buchanan, Gilbert, Wirgin and Xu [J.L. Buchanan, R.P. Gilbert, A. Wirgin, Y. Xu, Transient reflection and transmission of ultrasonic waves in cancellous bones, Appl. Math. Comp. 142 (2003), 561–573, R.P. Gilbert, Y. Xu, Shangyou Zhang, Computing porosity of cancellous bone using ultrasonic waves] we numerically computed the dependence of the porosity of cancellous bone encased in cortical bone and muscle on the measured ultrasonic wave. The computation shows the bone porosity can be recovered very accurately. The numerical data show that the ultrasonic wave of higher frequency would produce a more accurate bone porosity.

Discontinuity detection ahead of a tunnel face utilizing ultrasonic reflection: Laboratory scale application

Predicting ground conditions ahead of the tunnel face has been one of the most important requirements of tunnel construction. This study investigates the development and application of a high resolution ultrasonic wave imaging system, which captures the multiple reflections of ultrasonic waves at the interface, to detect discontinuities at laboratory scale rock mass model. Ultrasonic wave reflection imaging based on A- and B-modes is obtained through stacking, signal compensation, demodulation, and display. Experiments are carried out by using horizontal scanning and new rotational scanning devices. Experimental studies show that the rotational devices are able to identify horizontal and inclined discontinuities and the cavity on the plaster block at a fixed location. Furthermore, two discontinuities including horizontal and inclined discontinuity planes are detected. The rotating scanning technique produces images similar to those obtained by the typical horizontal scanning technique. This study suggests that the new rotational technique can be an economical and effective tool for the detection of discontinuity on a rock mass for the investigation of the ground condition in front of the tunnel face.

Simultaneous subsurface defect detection and contact parameter assessment in a wheel–rail system

In the last few years, a non-conventional ultrasonic approach has been proposed by the authors to experimentally assess the main contact parameters in wheel–rail systems. This technique, which is based on the analysis of the reflection of high frequency ultrasonic waves from the wheel–rail interface, makes it possible to obtain graphic maps from which we can observe the shape of the contact area, measure its size, and also collect qualitative information about contact pressure distribution. Furthermore, ultrasonic waves are quite well known as one of the primary non-destructive testing techniques useful in checking the presence of cracks in wheels, rails and axles. Thus, it was thought to combine these two approaches to obtain a single tool capable of supplying at the same time information about wheel–rail contact and the possible presence of subsurface cracks, which are typically located a few millimeters below the surface. This study reports the results of a series of experiments, performed on realistic wheel–rail couplings, in which the wheel was characterized by the presence of subsurface defects of known geometry. For each case tested, the whole ultrasonic waveform (which contains information about both the contact interface and a certain thickness of the wheel to investigate) was acquired and analyzed with dedicated software. The original data, expressed in terms of amplitude of reflected peaks, have been processed to obtain a number of graphic maps which, layer by layer, starting from the surface, give an idea first of all of contact conditions and, at the same time, of what kind of anomalies are present below it. These data are potentially useful in supporting numerical studies on the propagation of rolling contact fatigue (RCF) subsurface cracks by providing both actual contact pressure distribution and geometry of the cracks.

Formation of linear momentum in a rod during a laser pulse–matter interaction

Recently, we developed an optodynamic experimental technique that makes it possible to measure the linear momentum obtained by a metal target sample in the shape of a rod during a nanosecond laser pulse interaction in the ablative regime. The height of the rod’s rear end axial step-like displacement, caused by the first reflection of the laser-generated ultrasonic wave, is proportional to the linear momentum acquired by the rod. In comparison with commonly used ballistic methods, we can determine the acquired momentum on a much shorter time scale corresponding to the wave transition time, from the front to the rear end of the rod. Using this method we investigated the ambient air pressure dependence on the formation of linear momentum over a laser intensity range, from the ablation threshold to values about ten times higher. Steel rods of various diameters were used to demonstrate the effect of an expanding blast wave which delivers additional momentum to the target, when the laser beam on the target surface is smaller than the target itself. The typical value of the acquired target momentum is on the order of μN s and 10 μN s/J for the momentum coupling coefficient.

Optodynamic description of a linear momentum transfer from a laser induced ultrasonic wave to a rod

We present a new optodynamic experimental technique to measure the linear momentum obtained by a rod during a nanosecond laser pulse ablation of the rod’s front face on the basis of the displacement due to an ultrasonic wave reflection at its rear end. With the help of a simple theory, we explained the step-like motion of the rod’s free end. This theory conforms well with the general shape of the measured displacement history curve. The acquired momentum can be directly estimated by measuring the height of a step from the step-like motion of the rod’s end. Measurements based on an arm-compensated Michelson interferometer also enabled us to follow the attenuation of an ultrasonic wave and so to determine the characteristic attenuation time. This quantity plays a major role in the transfer of linear momentum from within the initial ultrasonic wave to the final net uniform motion of the specimen.

Ultrasonic Wave Reflection Approach to Evaluation of Fresh Concrete Friction

The friction of fresh concrete and granular materials against a metallic plate was investigated using ultrasonic wave reflection. Two complementary experimental devices, one a global device using a tribometer, the other a device based on an ultrasonic reflectometer giving a local approach at the formwork/fresh concrete interface. This approach is based on the evaluation of the density variation of the interface between the metallic wall and the material during the casting process. The authors propose a method to maintain a high impedance contrast by using a water layer interleaved between the transducer and the studied material. Good agreement between the ultrasonic parameter and the friction parameter was observed.

Characterization Methodology of the Interface in Multilayer Composites

The quality of the interfaces in multilayer composites is a critical issue in the reliability testing of the composite product during the manufacturing process and in-service. Weak interfaces have often gone undetected and may become potentially defective at a later stage. One example is the interface between mold compound and silicon (MC/Si) in IC packaging. There is a desire to study the interface quality quantitatively, so the potential defective area can be evaluated and identified early. In this paper, a nondestructive evaluation methodology is proposed to measure the available strength of the interface by using ultrasonic reflection coefficients. It is known that interface degradation can be either due to poor manufacturing process and stress loading. Characterization of the interface quality of the MC/Si interface is first conducted by measuring longitudinal ultrasonic wave reflections from the interface samples fabricated under varying conditioning processes that simulate the degradation. A combined test that measures the reflection coefficient of the interface under stress load has also been conducted to quantify the effect of the load. Finally, it is shown that the overall effect on the reflection coefficient and available strength of the interface is derived and can be used as a quantitative indicator.

Utilization of ultrasonic wave reflection technique to detect corrosion of rebar in concrete

Utilization of ultrasonic wave reflection technique to detect corrosion of rebar in concrete

A theoretical analysis in the time-domain of wave reflection on a bone plate

This paper presents an original method for simulating ultrasonic wave reflection on a fluid-loaded plate. Geometrical and material parameters used are relevant to the “axial transmission technique” (ATT) setup. Devices based on the ATT are used for the assessment of cortical bone strength (estimate of a fracture risk). In this work, the cortical bone layer is represented as a plate of infinite extent surrounded by fluid (soft tissues). A line source and a receiver are placed in the fluid. Transient waves generated upon reflection at the plate–fluid interfaces are addressed. Analytic Green's functions are derived with the generalized ray/Cagniard-de Hoop method. The acoustic response is obtained upon convolution of Green's functions with a given source pulse. The method associates each wave amplitude in the time-domain (lateral waves, reflected body waves, etc.) to a specific term of the final solution. The method is ideally suited to a detailed analysis of the ultrasonic signal for various geometrical and mechanical parameters. The results presented highlight the potential of the method for the understanding of wave phenomena involved in the ATT and similar setups. They also bring new elements that reinforce our theoretical knowledge of the ATT.

Comparison of ultrasonic wave reflection method and maturity method in evaluating early-age compressive strength of mortar

Abstract This paper focuses on the comparison between the ultrasonic wave reflection method and the widely known maturity method in their ability to evaluate compressive strength development of portland cement mortars. The experiments were conducted under laboratory conditions on cement mortars with different water–cement ratios (0.35, 0.5, 0.6) cured under different isothermal and non-isothermal conditions (15 °C, 25 °C, 35 °C, 15–35 °C). The results show that the application of the maturity method for accurate strength estimation requires the knowledge of the limiting strength of the mixture for the specific curing condition that is considered. It is not sufficient to base this estimation on the values of the limiting strength obtained from the calibration tests. The relationship between reflection loss and compressive strength was found to be independent of curing temperature. This finding is an important step towards establishing the wave reflection method as a non-destructive method for estimating early-age strength in cement-based materials.

Ultrasonic detection of subsurface flaws

New experimental relationships of coefficients of reflection and transmission of ultrasonic waves in artificial surface and subsurface models of cracks have been obtained in a wide range of parameters.

Ultrasound attenuation behind coronary atheroma without calcification: Mechanism revealed by autopsy

When performing intravascular ultrasound studies, the backward echo image can show marked attenuation, although there are no calcified deposits and it may be impossible to detect the intraplaque architecture. The pathology underlying this phenomenon was investigated in autopsy specimens. We hypothesize that the mechanism responsible for the attenuation involves micro-calcification and lipid in unstable plaques causing ultrasonic wave reflection and dispersion.

Improved ultrasonic wave reflection technique to monitor the setting of cement-based materials

A test setup using the ultrasonic wave reflection technique is used to monitor the hydration process of early-age cement-based materials throughout their setting and hardening. The focus of the investigation presented here is the monitoring of the stiffening behavior of cement pastes. Specimens are produced and kept under constant curing conditions. Immediately after placing the cement paste the data collection starts and continues throughout the setting process. The obtained ultrasonic data are correlated to mechanical and chemical properties of the specimens. The results illustrate that the applied experimental wave reflection technique is suitable to monitor the stiffening of cement pastes accurately.

Reflection and time-reversal of ultrasonic waves in the vicinity of the Rayleigh angle at a fluid-solid interface

When sending a plane ultrasonic wave toward a fluid-solid interface, the reflected wave is affected, depending on the incident angle. Around the Rayleigh angle the reflection coefficient has a strong and rapidly varying imaginary part. This has the effect of distorting the reflected wave front. If this reflected wave is time-reversed and sent back toward the interface, the reflected wave of this time-reversed wave should not present any distortion, as the time-reversal process restores the original phases. A theoretical and experimental study of these phenomena has been done. The distortion of the reflected waves around the Rayleigh angle is observed and as expected this distortion is canceled by the time-reversal process. However a significant loss of energy in the time-reversed signal is observed for incident angles around the Rayleigh angle, as part of the energy contained in the Rayleigh wave escapes the time-reversal mirror and is lost for the time-reversal process. In a second part, it is shown by simulations and experiments how this signal distortion by reflection around Rayleigh angle influences spatial focusing of waves by time-reversal or simple time-delay methods.

Rheometric and ultrasonic investigations of viscoelastic properties of fresh Portland cement pastes

The paper investigates the possibility of using a shear wave reflection technique to monitor the viscoelastic behavior (represented by storage shear modulus and viscosity) of Portland cement paste at very early age. Three cement pastes with water/cement ratios equal to 0.4, 0.5 and 0.6 cured under water at a constant temperature of 25 °C were studied. By measuring the wave reflection coefficients and the phase angles of reflected ultrasonic waves, the dynamic storage shear moduli and the viscosity of the cement paste can be calculated. The calculated results of the storage modulus were compared with the results obtained directly from the oscillatory rheometric measurement. In addition, the viscosity calculated from the wave reflection measurements was compared with results obtained directly from the step rheometric method and a qualitative agreement was found. The results show that as a non-destructive method, the ultrasonic wave reflection method provides useful information about both the elastic and viscous behavior of cement pastes at very early age.