Ultrasonic Pulse-echo Technique Research Articles

Error analysis of self-compensated ultrasound measurements of the thickness loss due to corrosion in pipe walls

The ultrasonic pulse-echo technique is widely employed to measure the wall thickness reduction due to corrosion in pipelines. Ultrasonic monitoring is noninvasive and can be performed online to evaluate the structural health of pipelines. Although ultrasound is a robust technique, it presents two main difficulties arising from the temperature variation in the medium being monitored: the mechanical assembly must have high stability and the ultrasonic propagation velocity must take into account the temperature variation. In this paper, a detailed strategy is presented to compensate for changes in the propagation velocity whenever the temperature changes. The method is considered self-compensated because the calibration data is obtained from the ultrasonic signals captured using the pipe under evaluation. The analysis of systematic errors in the temperature compensation is presented, first considering that a reference initial pipe thickness is given, and second when a reference sound velocity is given. The technique was evaluated under laboratory conditions using a closed loop with accelerated corrosion through the use of continuous flow saline water containing sand. In this test, the ultrasonic results were compared with the traditional coupon method used to determine corrosion loss. The results show that the self-compensated method was able to compensate for temperature fluctuations, and the total thickness loss measured by the ultrasound technique was close to the value measured by the coupons. Finally, the measurement system was tested in a production pipeline exposed to sunlight. The results show that the self-compensated method can reduce the oscillations in the thickness loss readings, caused by temperature swings, but large temperature variations cannot be completely compensated for. This experiment also shows the effects of low mechanical stability, which caused completely invalid results.

A study on elastic properties of CdO–B2O3 glasses by using ultrasonic pulse-echo technique

Binary xCdO–(100−x)B2O3 glasses (45 mol% ≤ x ≤ 90 mol%) were successfully prepared by the melt-quenching technique. The effect of CdO on structure and elastic properties of the borate network was studied by using ultrasonic pulse-echo technique. Density and molar volume of the glass show an increase with increasing CdO content, whereas, ultrasonic velocities, elastic moduli, micro-hardness and Debye temperature revealed a broad peaks around 75 mol% CdO. These findings were interpreted in terms the types of the basic structural units that composing the glass network. In the composition range 45 mol%≤x≤75 mol%, the addition of CdO, a network modifier, resulted in formation of extra bridging oxygens due to BO3ÆBO4 conversion and, which expands the borate network and stiffening the structure. Beyond x=75 mol%, some of CdO4 structural units and weaker B–O–Cd linkages are formed, besides the creation of NBOs. This opens the structure and decrease the rigidity of the glass. Correlations between elastic properties and compositional parameters are achieved by applying the ring deformation model and Abd El-Moneim’s approach.

Physical and elastic properties of Gd2O3-regulated gallate glasses

Novel glasses with high transmittance in 3–5 µm band and good mechanical/elastic properties are urgently needed in mid-infrared optical window. In this paper, the Gd2O3-regulated 31Ga2O3-(59-x)SrO-xGd2O3-10BaF2 (x = 4, 8, 12 and 16 mol%) gallate glasses with great potentiality in mid-infrared optical windows were synthesized and studied. With more introduction of Gd2O3, more non-bridging oxygen (NBO) was produced in glass network and longer infrared (IR) cut-off edges were obtained, which were demonstrated by Raman spectra and IR transmitting spectra respectively. With ultrasonic pulse-echo technique, the elastic properties of the glasses were obtained. The elastic modulus reached to a maximum with 8 mol% Gd2O3. By using a modified α with the value of 1.73, which is the slope of the linear-fitting of measured bulk modulus and the product of packing density and measured Young’s modulus, for the gallate glasses, Makishima-Mackenzie model and Rocherulle model were extended and a better agreement between experimental and calculated values of bulk modulus, shear modulus, longitudinal modulus and Poisson’s ratio has been achieved.

XRD, FTIR and ultrasonic investigations of cadmium lead bismuthate glasses

Cadmium lead bismuthate glasses in the system xCdO–(1−x)[0.5PbO + 0.5Bi2O3](40 mol% ≤ x ≤ 90 mol%) were successfully prepared by melt-quenching method. The structural and elastic properties have been investigated using XRD, FTIR and ultrasonic pulse–echo techniques. The XRD patterns confirmed the amorphous nature of the samples prepared. Density and ultrasonic velocity data were used to evaluate various elastic properties. Addition of CdO gave rise to decreased density and molar volume and increased elastic moduli, micro-hardness, and Debye temperature. The FTIR analysis revealed that increasing CdO content enhances the BiO6 octahedral sites at the expense of the BiO3 and PbO4 units. This results in the formation of Pb–O–Bi(6) and Bi(3)–O–Bi(6) linkages in the glass network, which stiffen the structure and improve the elastic properties. A correlation between elastic and compositional parameters was achieved on the basis of theories and approaches in the field.

How Ultrasonic Pulse-Echo Techniques and Numerical Simulations Can Work Together in the Evaluation of the Elastic Properties of Glasses

This paper presents the numerical simulation of the ultrasonic wave transmittance utilizing the elastodynamic finite integration technique (EFIT). With this methodology, it is possible to simulate the propagation of the ultrasound in a medium with a relatively low computational cost. The capability of this technique for determining the elastic properties of fluorophosphate and the aluminosilicate glasses is described in detail. The elastic constants of the glasses were calculated from the theoretically predicted longitudinal and transversal sound velocities and compared with the corresponding experimental data. Furthermore, the calculated and experimental elastic properties of the fluorophosphate and aluminosilicate glasses were correlated with the structural peculiarities of these glasses. This simulation technique is also suitable for unveiling the existence of possible defects in the glasses by comparing the experimental and simulation data. The EFIT technique is shown to be a very useful tool in order to provide fast and easy-to-acquire data regarding also the structural characteristics of various glassy systems. This can be used in conjunction with other spectroscopic techniques which can prove to be extremely useful for the non-destructive testing of vitreous materials. The latter can prove very important when vitreous materials used in optical or optoelectronic applications need continuous monitoring in order to ensure their optimum operation and functionality with limited intervention. The main contribution of this paper is the treatment of numerical time-domain modeling of 2D acoustic wave propagation in a viscoelastic medium by implementing the elastodynamic finite integration technique (EFIT).

A Correction Method for the Measurement of Frequency-Dependent Attenuation Coefficient With Curved Surface Specimens Using Normal Contact Transducer

The ultrasonic pulse-echo technique has been widely employed for the measurement of the frequency-dependent attenuation coefficient in polycrystalline metals. However, the nonuniform thickness of the coupling layer between the transducer piston and the curved surface is inevitable for curved specimens, resulting in a significant overestimation. In addition, the curved surface also affects the diffraction loss caused by the divergence and convergence of ultrasonic beams during the propagation path. In this study, a correction method is proposed for the experimental calculation of the frequency-dependent attenuation with the curved surface components using a contact transducer. First, with the analysis of the nonuniform coupling layer created by the curved surface and transducer piston, the integral over the effective cross-sectional area is introduced to determine the reflection coefficient. Second, an equivalent rectangular transducer sound field model is proposed to calculate the diffraction loss for different curvatures and propagation distances based on the multi-Gaussian beam (MGB) theory. Then, a correction model is established to compensate for the deviation caused by the curved surfaces. To verify the feasibility of the proposed method, two cylindrical bars and five blanks with different curvatures were designed. The experimental results show that the proposed correction method can effectively eliminate the deviation caused by the curved surface and improve the stability of measurement. With the correction, the variation of the attenuation spectrum for the curved specimens is reduced by approximately 5%. This facilitates researchers to better develop and use frequency-dependent attenuation coefficients of materials for further applications.

Assessment of surface/subsurface damage in early-stage fatigue: A new attempt based on LCR wave

To facilitate a surface/subsurface fatigue damage awareness in the early stage, a signal-steady, thickness-independent, nondestructive method is proposed based on a critically refracted longitudinal (LCR) wave, which is compared with the conventional pulse-echo ultrasonic technique. With the evolution of cyclic damage in microscale, a normalized amplitude difference of LCR wave,Adif, increases monotonically, but the attenuation coefficient of the pulse-echo method evolves non-monotonically. The effects of surface roughness on the propagation of LCR wave are studied. A discrete strategy is proposed to detach the coupling between surface roughness and dislocation damping, and the mechanism is discussed with dislocation density-based calculation.

Quantitative Measurement Method for Ice Roughness on an Aircraft Surface

When an aircraft passes through clouds containing supercooled water droplets, the leading edge’s surface will gradually accumulate ice. Ice surface roughness is an important parameter affecting the local convective heat transfer coefficient and the water collection coefficient, which in turn affect the ice’s shape. However, because the surface roughness of aircraft icing is a transient value varying in time and space, it is extremely difficult to measure with existing methods in real time. In this study, a noncontact ultrasonic pulse-echo (UPE) technique is applied to characterize the ice roughness of an airfoil model’s surface. A multilayer model with equivalent bead-like roughness profiles is established to study the effects of changes in ice roughness on ultrasonic echo signals. A series of simulations indicated that ice roughness can be measured quantitatively and effectively in the range of [11.6, 120] μm. Based on these simulations, an experimental UPE device was developed to measure echo signals on top of the ice corresponding to surface roughness. The results show that for both the regular and irregular surface roughness samples, the maximum relative error in the roughness is less than 15%. Meanwhile, we designed and supplemented the experiment with the NACA-0012 airfoil model to realize the online measurement of ice roughness in an icing research tunnel.

A method for extracting sole mechanical properties of Bragg reflector by GHz ultrasonic pulse-echo technique

Solidly mounted resonators (SMRs) with an acoustic Bragg reflector should be more suitable for high power RF filters than a self-standing structure because heat can be transferred to the supporting substrate. Thus, even though the demand for SMRs is expected to increase, the evaluation of the properties of the Bragg reflector that comprise them cannot be separated from the properties of the resonator as a whole. A method to evaluate the mechanical reflection coefficient of the Bragg reflector alone before the piezoelectric layer is grown would, therefore, be attractive, as it would be useful in optimizing the Bragg reflector. In this study, a nondestructive evaluation method of the reflector using a GHz ultrasonic pulse-echo technique is proposed. The Sc0.40Al0.60N film ultrasonic transducers with electromechanical coupling coefficient kt2 of 15.8% and longitudinal wave insertion loss of 7.0 dB with 77% fractional bandwidth were employed for the measurement system. Mo/SiO2 Bragg reflector test samples with various number of pairs were evaluated. The experimental mechanical reflectance of the Bragg reflector agreed well with theoretical results simulated by a mechanical equivalent circuit model.

Ultrasonic Monitoring of Part’s Height and Layer Thickness in Powder Bed Fusion

This paper presents a preliminary study on an in-situ ultrasonic measurement technique applied to monitoring part’s height and defect occurrence during the Laser Powder Bed Fusion process. Firstly the ultrasonic wave speed is determined for LPBF manufactured 100Cr6 samples with a pulse echo configuration and a 10Mhz ultrasonic wave. A measured propagation speed value, of 5660 ±100m/s in every direction confirms the isotropy of the obtained LPBF samples. Secondly, the ultrasonic pulse echo technique is used to monitor the part’s height evolution during the process based on the measured propagation velocity. This new method provides in-situ measurements showing that the actual remelted layer thickness value oscillates in the range of ± 30% of the theoretical layer thickness.

Study on freezing characteristics of the surface water film over glaze ice by using an ultrasonic pulse-echo technique

This study proposes an ultrasonic pulse-echo technique to examine the freezing characteristics of a thin film of water over ice, and uses it to develop a method to measure the thickness of glaze ice. A multilayer model is first introduced to simulate ultrasonic transmission through multiple media. A transition layer is then inserted between the layers of ice and water, and its properties were in gradient form along the direction of thickness. Following this, a high-frequency ultrasonic experimental device is developed to dynamically measure variations in the thickness of the layers of ice and water. The accuracy of the proposed model of the transition layer was validated by showing that its numerical results agreed well with those of experiments. The results show that the amplitude of echo from the top of the ice layer was at its minimum when the thickness of the film of water was in the range of [40, 45] μm, and increased when the film of water was thinner than 40 μm. A delay in echo from the top of the layer of ice was observed when measuring its thickness because the film of water froze, which yielded a relative error of 3.34%. The proposed numerical model can thus efficiently measure the thickness of glaze ice.

Ultrasonic monitoring of the VVER-1000 FA form change

A procedure has been developed to determine the geometrical parameters of fuel assemblies (FA) by an ultrasonic pulse-echo technique used for all types of light-water reactor FAs. The measurement of geometrical parameters is achieved through the pairwise installation of ultrasonic transducers opposite the FA spacer grid faces at a distance of not more than a half of the transducer acoustic field near-region length such that the acoustic axes of the pairwise transducers are parallel to each other. The advantages of the presented technique is that it enables monitoring of any FA modifications, including the VVER reactor assemblies with a different number of spacer grids. The paper presents a mathematical model of the acoustic path developed in a geometrical acoustics approximation and its verification results. The model was used for computational and experimental studies of the ultrasonic test technique, and engineering formulas have been developed to calculate the errors of the transducer-measured distance to the FA surface. A code has been developed to simulate the FA form change monitoring and can be used to design new monitoring systems. The developed technique to determine the VVER-1000 FA geometrical parameters was introduced at units 1 and 2 of the Temelin NPP, the Czech Republic, for the TVSA-T FA form change monitoring. The successful use of the proposed technique makes it possible to recommend it for use in inspection benches at other NPPs.

Feasibility of using ultrasonic-based prediction for hydrogen embrittlement susceptibility of high-strength heat-resistant steel 2.25Cr-1Mo-0.25V

Nondestructive evaluation for the mechanical properties loss of equipment materials serviced in the hydrogen environment is particularly vital for monitoring the equipment operating conditions. In this study, the quantitative relationship between the introduced hydrogen content and the mechanical property degradation of 2.25Cr-1Mo-0.25V steel was investigated using electrochemical hydrogen charging technique and tensile testing, and a nondestructive testing method based on pulse-echo ultrasonic measurement technique, combined with the results of mechanical assessment for hydrogen embrittlement (HE) susceptibility, was proposed to indirectly estimate the degree of hydrogen-induced plasticity loss of the steel. Moreover, signal reconstruction technique was also used to improve the measurement accuracy of ultrasonic echo signal. The results of the study showed that hydrogen present in the metal lattice intensifies the energy attenuation of ultrasonic echo, verifying the feasibility and validity of the measurement method in the effective online prediction of HE susceptibility of the tested steel.

Measurement of the Anisotropic Dynamic Elastic Constants of Additive Manufactured and Wrought Ti6Al4V Alloys.

Additively manufactured (AM) materials and hot rolled materials are typically orthotropic, and exhibit anisotropic elastic properties. This paper elucidates the anisotropic elastic properties (Young’s modulus, shear modulus, and Poisson’s ratio) of Ti6Al4V alloy in four different conditions: three AM (by selective laser melting, SLM, electron beam melting, EBM, and directed energy deposition, DED, processes) and one wrought alloy (for comparison). A specially designed polygon sample allowed measurement of 12 sound wave velocities (SWVs), employing the dynamic pulse-echo ultrasonic technique. In conjunction with the measured density values, these SWVs enabled deriving of the tensor of elastic constants (Cij) and the three-dimensional (3D) Young’s moduli maps. Electron backscatter diffraction (EBSD) and micro-computed tomography (μCT) were employed to characterize the grain size and orientation as well as porosity and other defects which could explain the difference in the measured elastic constants of the four materials. All three types of AM materials showed only minor anisotropy. The wrought (hot rolled) alloy exhibited the highest density, virtually pore-free μCT images, and the highest ultrasonic anisotropy and polarity behavior. EBSD analysis revealed that a thin β-phase layer that formed along the elongated grain boundaries caused the ultrasonic polarity behavior. The finding that the elastic properties depend on the manufacturing process and on the angle relative to either the rolling direction or the AM build direction should be taken into account in the design of products. The data reported herein is valuable for materials selection and finite element analyses in mechanical design. The pulse-echo measurement procedure employed in this study may be further adapted and used for quality control of AM materials and parts.

Aluminum Matrix Composites with Weak Particle Matrix Interfaces: Effective Elastic Properties Investigated Using Micromechanical Modeling.

The impact of weak particle-matrix interfaces in aluminum matrix composites (AMCs) on effective elastic properties was studied using micromechanical finite-element analysis. Both simplified unit cell representations (i.e., representative area or volume elements) and “real” microstructure-based unit cells were considered. It is demonstrated that a 2D unit cell representation provides accurate effective properties only for strong particle-matrix bond conditions, and underpredicts the effective properties (compared to 3D unit cell computations) for weak interfaces. The computations based on real microstructure of an Al–TiB2 composite fabricated using spark plasma sintering (SPS) show that, for weak interfaces, the effective elastic properties under tension are different from those obtained under compression. Computations show that differences are the result of the local stress and strain fields, and contact mechanics between particles and the matrix. Preliminary measurements of the effective elastic properties using the ultrasonic pulse-echo technique and compression experiments support the trends observed in computational analysis.

Detection of overlapping ultrasonic echoes with deep neural networks

Ultrasonic Pulse-Echo techniques have a significant role in monitoring the integrity of layered structures and adhesive joints along their service life. However, when acoustically measuring thin layers, the resulting echoes from two successive interfaces overlap in time, limiting the resolution that can be resolved using conventional pulse-echo techniques. Deep convolutional networks have arisen as a promising framework, providing state-of-the-art performance for various signal processing tasks. In this paper, we explore the applicability of deep networks for detection of overlapping ultrasonic echoes. The network is shown to outperform traditional algorithms in simulations for a significant range of echo overlaps, echo pattern variance and noise levels. In addition, experiments on two physical phantoms are conducted, demonstrating superiority of the network over traditional methods for layer thickness estimation.

3D Internal Visualization of Concrete Structure Using Multifaceted Data for Ultrasonic Array Pulse-Echo Tomography.

This research proposes a 3D internal visualization using ultrasonic pulse-echo tomography technique to evaluate accurately the state of concrete structures for their efficient maintenance within a limited budget. Synthetic aperture focusing technique (SAFT) is used as a post-processing algorithm to manipulate the data measured by the ultrasonic pulse-echo technique. Multifaceted measurements improve the weakness of the existing ultrasonic pulse-echo tomography technique that cannot identify the area beyond a reflector as well as the area located far away from measuring surfaces. The application of apodization factor, pulse peak delay calibration and elimination of trivial response not only complements the weaknesses of the SAFT algorithm but also improves the accuracy of the SAFT algorithm. The results show that the proposed method reduces the unnecessary surface noise and improves the expressiveness of the reflector’s boundaries on the resulting images. It is expected that the proposed 3D internal visualization technique will provide a useful non-destructive evaluation tool in combination with another structure evaluation method.

DEVELOPED LIQUID FILMS FALLING AROUND TAYLOR BUBBLES INSIDE VERTICAL STAGNANT COLUMNS

The present work reports an experimental study of developed liquid films falling around single Taylor bubbles inside vertical tubes containing stagnant liquids. Experiments were carried out in acrylic tubes with 2.0 m length and inner diameters of 0.019, 0.024 and 0.034 m. Five water-glycerin mixtures were used, corresponding to film Reynolds number（Ref）ranging from 2 to 7650. A pulse-echo ultrasonic technique was applied to measure the rise velocity of the bubble and the equilibrium thickness of the liquid film. These parameters together with the calculated standard deviation of the equilibrium film thickness provided information about the development of waves on the gas-liquid interfaces, which could be related with the laminar-turbulent transition of liquid films falling around Taylor bubbles. The results indicated that the wave amplitudes increased sharply for Ref> 1000. This value of Ref is in agreement with literature concerning the laminar-turbulent transition for free falling films on vertical surfaces.

Smart two-tank water quality and level detection system via IoT

The two-tank water system is common practice for the storage and distribution of water in many homes. Water is transported via a pipeline network from the storage tank (lower tank) to the distribution tank (overhead tank) using an electric pumping machine. Due to limited control in the existing pumping system, water wastage becomes inevitable. Determining the quality of water in the overhead tank before supply in the home is still unaddressed. In this work, an integrated Android mobile App and a control system were developed to assess the water quality, perform level check in the overhead tank, and activate intelligent pumping control. An ultrasonic pulse-echo technique was used for water level checks, while the water turbidity and pH signals were used for water quality checks. Three-level control conditions (LC_1, LC_2, LC_3) and two water quality check conditions (QC_1 and QC_2) were devised and used in the intelligent control algorithm of the system. Control valve1 regulates the flushable poor water quality while valve2 regulates the house's supply of good water quality. The absolute relative error between the expected time and the system time of filling the tank level was observed to be less than 10% when the water volume is less than 81%. Hence, distortion in the sensory signals increases and worsen as the water level approaches the ultrasonic sensor position. The poor internet signal network was observed to affect the real-time monitoring and automation of the system control through delay in system responses to commands. However, the average recorded response time of the system is 3 s, and it could be less in the situation of good internet network services.

Evaluating the elastic properties of Al2O3–Al FGMs by longitudinal and transverse ultrasonic bulk waves velocity features

The present study aimed to investigate the elastic properties of functionally graded materials using ultrasonic bulk wave velocity features. To this end, three Al2O3–Al FGM samples were fabricated by spark plasma sintering method at three different temperatures (1050 °C, 1400 °C, and 1450 °C). In addition, two homogenous aluminum and alumina samples were fabricated to evaluate the properties of the initial materials using the initial powders. Ultrasonic pulse-echo technique was applied on fabricated samples in order to measure the longitudinal and transverse wave velocities. The elastic properties of the graded samples were obtained by wave velocity features and Archimedes density. The alumina and aluminum elastic modulus were measured as 394 and 70 GPa, respectively. The results indicated that increasing the sintering temperature from 1050 °C to 1400 °C and 1450 °C leads to considerable improvement in the average elastic modulus. The average elastic modulus of the graded bundle sintered at 1450 °C (308 GPa) was about 8.5% higher than that of the one sintered at 1400 °C (284 GPa). The microstructure analogies of samples illustrated micro-voids and phases agglomeration in all samples. The highest wave attenuation was observed in the graded sample with the lowest sintering temperature, i.e., the largest number of micro-voids caused the highest energy absorption in the graded bundle sintered at 1050 °C.