Longitudinal Ultrasonic Waves Research Articles

Characterization of Microstructure of Fe-TiC and Fe-B4C Composites Using Ultrasonic Measurements

In this paper, an iron (Fe) matrix reinforced with boron carbide (B4C) and titanium carbide (TiC) was produced by conventional furnace sintering at the same compositions and temperatures. Experimental data on the change in ultrasonic velocity parameter, densities and porosity of these two different microstructure composites during microstructure development are reported. The microstructural phases were characterized by metallographic studies and hardness measurements. The velocities of ultrasonic longitudinal waves were measured by the pulse- echo method using the transmit/receive probe. In the Fe-TiC composite sample, ultrasound longitudinal wave velocity, hardness and porosity increased linearly depending on the increasing amount of TiC. In the Fe-B4C composite sample, on the other hand, there is a linear increase in general depending on the increasing amount of B4C, and there is a sharp decrease in the amount of 8,33% B4C. The reason for this decrease and other results are explained by taking into account SEM and XRD analyzes.

Identification of mineralogical ore varieties using ultrasonic measurement results

Purpose. To improve the measurement and information base of ultrasonic measurements rock characteristics to assess their mineralogical varieties. It is proposed to use a combination of measurement results of the acoustic quality factor of the test sample in relation to longitudinal and transverse ultrasonic waves, as well as the characteristic coefficient based on the dispersion and the average amplitude value of the received signal, for fuzzy identification of mineralogical and technological varieties of iron ore. Methods. As elastic waves propagate through the rock mass, they undergo attenuation due to absorption and dissipation of ultrasonic signal energy. The degree of attenuation, as well as the wave propagation velocity, is dependent on the physical-mechanical and chemical-mineralogical properties of the medium through which they travel. In this paper, we analyze a rock characterized by a complex structure comprising ore inclusions and surrounding matrix, each of which differs in its physical-mechanical and chemical-mineralogical properties. In particular, in iron ore samples, the distribution of mineral grains and aggregates exhibits significant heterogeneity in terms of both amount and size. Findings. An iterative method of fuzzy identification of mineralogical-technological iron ore varieties, based on the analysis of their properties in vector space of features, allows, by minimizing the sums of weighted distances between the analyzed and reference values of ultrasonic measurement results, to attribute them with a certain degree of belonging to the main technological types of ores mined at the deposit, and define them as magnetite quartzite with a confidence probability of 0.93. Originality. As an information base for identification of mineralogical iron ore varieties, the results of measuring the velocity and attenuation of longitudinal and transverse ultrasonic waves of appropriate frequency are used, on the basis of which the acoustic quality factor of the rock sample is calculated, as well as the characteristic parameter S, which is determined by the dispersion and average values of the received ultrasonic signal intensity, which has traveled a certain distance in the studied environment. Practical implications. The results of tests and practical approbation of the method for identifying mineralogical iron ore varieties based on the data of ultrasonic well logging testify to its high efficiency, which allows recommending the developed scientific-technical solutions for wide industrial application at mining enterprises.

Investigation of the Effects of Gamma Radiation and Y2O3 on the Elastic Properties of Al2024 Composites by Ultrasonic Method

In this study, the effect of Y2O3 contribution and γ-irradiation on the elastic properties of pure Al2024 and Al2024/Y2O3 composites was precisely investigated with the help of determined density and ultrasonic wave velocities. Ultrasonic longitudinal and shear wave velocity measurements of the samples were performed at room temperature using the ultrasonic pulse-echo method at 20 and 5 MHz frequencies, respectively. X-ray diffraction analysis and scanning electron microscopy examined the microstructural properties and phase characterizations of metal matrix composite (MMC) samples. A gamma cell type 60Co source was used to irradiate MMC samples in the air at room temperature. The absorbed dose rate was measured to be approximately 1.5 kGy/h, and the total delivered dose was 50 kGy. According to the findings obtained from the research, the contribution of Y2O3 to pure Al 2024 at 0.5, 1, and 5 wt.% ratios and exposure to gamma rays of 50 kGy caused a decrease in VL, L, K, and μ values and a significant increase in ρ, VS, G, HV, H, and E values. The highest Young’s modulus values compared with pure Al2024 were obtained in both unirradiated and irradiated Al2024/0.5Y2O3 composites.

Assessment of aging degradation in rubber using quasi-static components of ultrasonic longitudinal waves

Abstract Aging degradation is the main form of failure of rubber in service, leading to a decline in its physical and mechanical properties. This paper presents an efficient method for assessing the aging degradation of rubber using the quasi-static component (QSC) of ultrasonic longitudinal waves induced by acoustic radiation. The experiments quantitatively observe the response of the QSC pulse to different levels of ageing degradation. A pulse-echo ultrasonic transducer is employed to simultaneously capture the primary longitudinal wave (PLW) and QSC echoes, enabling the determination of the acoustic nonlinearity parameter of QSC with a single transducer excitation. The results suggest that, in comparison to traditional linear ultrasonic techniques based on attenuation coefficient and wave velocity measurements, the relative acoustic nonlinear parameter of QSC proves to be more sensitive to aging degradation in rubber. Particularly, the amplitude of the QSC pulse undergoes a significant change with increasing aging degradation, even when the PLW tone burst is completely attenuated. These findings confirm the effectiveness of QSC as a method for evaluating aging degradation in highly attenuative materials.

Measurement Method of Stress in High-Voltage Cable Accessories Based on Ultrasonic Longitudinal Wave Attenuation.

High-voltage cables are the main arteries of urban power supply. Cable accessories are connecting components between different sections of cables or between cables and other electrical equipment. The stress in the cold shrink tube of cable accessories is a key parameter to ensure the stable operation of the power system. This paper attempts to explore a method for measuring the stress in the cold shrink tube of high-voltage cable accessories based on ultrasonic longitudinal wave attenuation. Firstly, a pulse ultrasonic longitudinal wave testing system based on FPGA is designed, where the ultrasonic sensor operates in a single-transmit, single-receive mode with a frequency of 3 MHz, a repetition frequency of 50 Hz, and a data acquisition and transmission frequency of 40 MHz. Then, through experiments and theoretical calculations, the transmission and attenuation characteristics of ultrasonic longitudinal waves in multi-layer elastic media are studied, revealing an exponential relationship between ultrasonic wave attenuation and the thickness of the cold shrink tube. Finally, by establishing a theoretical model of the radial stress of the cold shrink tube, using the thickness of the cold shrink tube as an intermediate variable, an effective measurement of the stress of the cold shrink tube was achieved.

Evaluation of 3D printed 316L stainless steel microstructure and mechanical property by laser ultrasonics

ABSTRACT In this paper, the laser ultrasonic non-destructive testing technology was used to detect the microstructure and mechanical properties of selective laser melting (SLM) 316 L stainless steel after post-treatment. The microstructure and mechanical properties of additively manufactured 316 L stainless steel were measured by Scanning electron microscopy (SEM), Electron backscatter diffraction (EBSD), tensile testing, etc. The laser ultrasonic longitudinal wave signal characteristic values were coupled with the microstructure and mechanical properties of SLM 316 L stainless steel. The results show that: The yield strength has a good correlation with wave speed and attenuation. With the increase of holding temperature and holding time, the grain size increases, the low angle grain boundary decreases, the yield strength gradually decreases from 409 MPa to 359 MPa, the wave velocity increases from 5579 m/s to 5700 m/s, and the frequency domain attenuation coefficient increases from 0.13 dB/mm to 0.16 dB/mm, the central frequency domain is about 10 MHz. The ultimate tensile strength is related to the frequency domain attenuation. The ultimate tensile strength decreases with the increase of the frequency domain attenuation coefficient. It can provide a reference for the evaluation of mechanical properties by laser ultrasonic testing.

Numerical simulation and experimental study on nonlinear ultrasonic characterization of graphite size in nodular cast iron

Graphite morphology has a significant influence on mechanical properties such as tensile strength and hardness in nodular cast iron (NCI). Compared to the detection of graphite nodularity, there is relatively less ultrasonic simulation and detection experiment research on the graphite size. Therefore, it is of great importance to study rapid nondestructive testing methods for the internal graphite size of NCI. This study establishes a simulation model of nonlinear ultrasonic penetration longitudinal wave detection for graphite size. The acoustic nonlinearity parameter (ANP) is used to characterize the graphite size. Nonlinear ultrasonic detection experiments on the internal graphite size are conducted to verify the reliability of the nonlinear ultrasonic simulation model. The simulation and experimental results show that the ANP of penetrating longitudinal waves decreases with the increase of average graphite diameter. The relationship between ANP and internal graphite size is established. Moreover, the experimental results verified the accuracy of the numerical model. The decrease in ANP may be related to the decrease in the number of grain boundaries. Therefore, the nonlinear ultrasonic technique is an effective method for characterizing the internal graphite size. The establishment of a nonlinear ultrasonic simulation model for graphite size in NCI lays the research foundation for nonlinear ultrasonic microstructure characterization experiments.

Analysis of the Suitability of Ultrasonic Testing for Verification of Nonuniform Welded Joints of Austenitic-Ferritic Sheets.

The purpose of the presented research was to determine the suitability of using ultrasonic testing (UT) to inspect heterogeneous, from a material point of view, welded joints on the example of the joints of a ferritic steel element with elements made of an austenitic steel. The echo technique with transverse (SEK) and longitudinal wave heads (SEL) addressed this issue. Due to the widespread use of 13CrMo4-5 and X2CrNiMo17-12-2 steel grades in the energy industry, they were selected as the test materials for the study. The objects of the presented research were welded joint specimens with thicknesses of 8, 12, and 16 mm and dimensions of 300 × 300 mm, made using the 135 metal active gas (MAG) process with the use of the Lincoln 309LSi wire-a ferritic-austenitic filler material. The stages of the research task were (1) making distance-amplitude curve (DAC) patterns from the test materials; (2) preparation of specimens of welded joints with artificial discontinuities in the form of through-holes; (3) performing UT tests on welded joints with artificial discontinuities using heads with 60° and 70° angles for the transverse wave and angle heads for longitudinal waves with similar beam insertion angles; (4) selection, by radiographic testing (RT), of welded joint specimens with natural discontinuities in the form of a lack of sidewall fusion; (5) performing UT tests on welded joints with natural discontinuities, using heads as welded joints with artificial discontinuities. It was found that (1) the highest sensitivity of discontinuity detection was obtained by performing tests on the ferritic steel side, which is due to the lower attenuation of the ultrasonic wave propagating in ferritic steel compared to austenitic steel; (2) the best detection of discontinuities could be obtained using a longitudinal ultrasonic wave; (3) there is a relationship between the thickness of the welded elements, the angle of the ultrasonic beam introduction, and the effectiveness of discontinuity detection.

A numerical investigation of longitudinal wave for thermo-acoustoelastic effects on fluid-embedded in two viscoelastic layer plates at higher temperatures

Ultrasound has become indispensable for inspecting complex structures due to its efficient propagation in both liquids and solid materials. Extensive research has been conducted across various domains, encompassing wave behavior, structural interactions, material dispersion due to heterogeneity, propagation characteristics near boundaries, defect detection, and signal processing. In this context, longitudinal waves are particularly favored for examining thick components exhibiting surface defects or thermal gradients across their depth. In our current work, we employed a numerical approach based on the Transfer Matrix Method (TMM) to model ultrasound signals backscattered under normal incidence by a multilayer structure immersed in water. This method involves representing each layer using a quadrupole formalism that combines stresses and velocities. Simultaneously, we harnessed the thermodynamic equation for aqueous solutions and Fourier’s law to derive the expression for the thermo-acoustic coefficient of longitudinal waves within a fluid embedded between two parallel immersed plates, enabling precise control of the fluid temperature over a range from 0 °C to 700 °C. In the time domain, we evaluated the ultrasonic parameters of a fluid exposed to a temperature range from 0 to 700 °C. This evaluation was supported by a variety of multilayer structures designed to ensure the accurate processing of backscattered signals. These structures were excited by longitudinal waves, with a central frequency fixed at 5 MHz. The results obtained emphasize the sensitivity of longitudinal waves to temperature variations and reveal the presence of wave dispersion induced by temperature fluctuations. In order to investigate this dispersion, we conducted an extensive study of ultrasonic longitudinal wave propagation across a range of excitation frequencies from 2 to 12 MHz. This study encompassed the calculation of phase and group velocities, as well as the corresponding attenuation. The results confirm the relevance of our research to various applications and highlight the complex interaction between longitudinal wave dispersion and temperature variations.

Debye temperatures and nanostructuring of polyurethane auxetics

Based on experimental values of longitudinal and transverse ultrasonic wave propagation velocities and surface Rayleigh wave velocities were calculated phonon energies and Debye limiting frequencies and temperatures were determined of metal-filled polyurethane auxetics samples. Modeling the structural formations of such systems and obtaining the value of the lattice and Grüneisen acoustic parameter made it possible to find the root-mean-square displacement of the atomic groups of the macromolecule, as well as the limits of forced elasticity, shear deformation, and deformation of the interstructural bond. The relationship between Debye frequencies (temperatures) and Poisson's ratio, Grüneisen parameter, was established. A quantum-mechanical approach to the movement of electrons, atomic groups of macromolecules, thermal and sound phonons made it possible to estimate the size of nanoformations in the composition. The theoretical values of Poisson's ratio obtained based on models of polymer auxetics and processes of propagation of ultrasonic waves in such systems are analyzed.

Quantitative analysis of laser-generated ultrasonic wave characteristics and their correlation with grain size in polycrystalline materials

Abstract The quantitative relationship between nanosecond pulsed laser parameters and the characteristics of laser-generated ultrasonic waves in polycrystalline materials was evaluated. The high energy of the pulsed laser with a large irradiation spot simultaneously generated ultrasonic longitudinal and shear waves at the epicenter under the slight ablation regime. An optimized denoising technique based on wavelet thresholding and variational mode decomposition was applied to reduce noise in shear waves with a low signal-to-noise ratio. An approach for characterizing grain size was proposed using spectral center frequency ratio (SCFR) based on time-frequency analysis. The results have demonstrated that the generation regime of ultrasonic waves is not solely determined by the laser power density; even at high power densities, a high energy with a large spot can generate an ultrasonic waveform dominated by the thermoelastic effect. It is ascribed to the intensification of the thermoelastic effect with the proportional increase in laser irradiation spot area for a given laser power density. Furthermore, both longitudinal and shear wave SCFRs are linearly related to grain size in polycrystalline materials; however, the shear wave SCFR is more sensitive to finer-grained materials. This study holds great significance for evaluating metal material properties using laser ultrasound.

A novel laser-EMAT ultrasonic longitudinal wave resonance method for wall thickness measurement at high temperatures

In this paper we propose a novel ultrasonic longitudinal wave resonance method for measuring the thickness of metal walls using a laser-electromagnetic acoustic transducer (Laser-EMAT). The method is based on the surface constraint mechanism (SCM) of the material and is expected to be capable of accurately detecting local thinning of metal walls in a non-contact manner and at high temperatures. Based on finite element analysis of laser-EMAT ultrasonic resonance measurement of aluminum alloy thickness, we investigated the effects of such key factors as SCM, irradiation parameters of laser source, and the size of EMAT receiving coil on the accuracy of thickness measurement (resonance frequency position) and on the amplitude of the resonance wave. Both numerical simulations and experiments are conducted to demonstrate that the measurement accuracy of the proposed method is not affected by SCM, irradiation laser source parameters, and EMAT receiving coil size, and that accurate detection of stepped aluminum plates with thickness thinning from 3.0 mm to 0.5 mm is achieved. Furthermore, we were able to perform rapid detection of aluminum thin plate thickness at 500 °C temperature with an EMAT lift-off of 5.0 mm and achieved a relative experimental error as small as 3.40 %. The results obtained in this study showed that the proposed method performed well in non-contact measurement of metal thinning in harsh environment of high temperature.

An Ultrasonic Rock Bolt Sensing Technology (I): Methodology and Laboratory Studies

Rock bolts play a critical role in ground support in mining, tunneling and construction. Being able to obtain timely information on rock bolt load condition and deformation could help immensely in safeguarding workers’ safety, optimization of ground support system, and ensuring stability and longevity of underground structures. The objective of this work was to develop a practical ultrasonic rock bolt sensing technology for monitoring axial load and deformation of a full-bodied rock bolt in both elastic and plastic deformation regimes. To this end, empirical mathematical models involving simultaneous use of times of flight of longitudinal and shear ultrasonic waves propagating along the axial direction of the rock bolt were developed, sensors were designed and fabricated, and laboratory studies were conducted. The results showed that the technology was able to measure load change, provide early detection of yield, and measure both plastic and total elongations of the rock bolt undergoing a pull test. Additionally, sectional load and elongation information could be obtained by applying the technology to rock bolts divided into sections by drilled holes along their shanks, therefore, providing the capability to assess the condition of grouted bolts at different depths within a rock mass. This work has laid the groundwork for the deployment of the technology in the field.

Numerical study on ultrasonic detection of cracks in metallic structures with variable cross-sectional thickness

The metal structures are widely used in aerospace engineering, especially in joints and spars. The safety of these parts is important to ensure the safe service of the whole structures. The ultrasonic wave is a traditional technique to detect cracks in metals. However, it is usually difficult to find all the cracks because of its difficulty in variable directions of the crack and the irregular shapes of the metals. This paper aims to address the challenge of detecting cracks in metallic structures with varying cross-sectional thicknesses using ultrasonic methods. The research investigates the behavior of ultrasonic longitudinal and transverse waves as they propagate through aluminum plates with variable cross sections. Additionally, it examines how cracks in different orientations influence these wave types. The theoretical analyses are performed which explore the reflection of oblique incidence waves and the diffraction of ultrasonic waves when they encounter semi-infinite cracks. Subsequently, numerical simulations are performed to validate the theoretical findings and to detect both horizontal and vertical cracks within metal plates of varying cross-sectional thicknesses. The findings indicate that both longitudinal and transverse waves are effective in identifying the location of damage caused by horizontal cracks. However, when it comes to vertical cracks, only transverse waves are successful in detecting their precise location. From the research of this paper, transverse ultrasonic wave is suggested to detect cracks in metal structures with irregular cross sections.

RESEARCH, DEVELOPMENT AND IMPLEMENTATION OF METHODS AND TECHNOLOGIES OF ACOUSTIC STRAIN GAUGING OF SPLIT JOINTS OF LIQUID ROCKET ENGINES FOR SPACE LAUNCH VEHICLES

A review of the results of research, development and implementation of methods and technologies of acoustic strain measurement of split joints of liquid rocket engines for space launch vehicles is presented. A brief description of methods for measuring the incremental time of propagation of ultrasonic longitudinal waves and the ratio of longitudinal and shear wave velocities is given. The description of the developed and enacted GOST R 52889‒2007 “Non-destructive testing. Acoustic method of control of tightening force of threaded joints. General requirements”. Acoustic strain gauges, including those in regular operation at NPO Energomash, are described. A brief description of the specialized program “Acoustic Tensometer” is given, as well as a set of standard samples for performance control and preliminary adjustment of devices and calibration bench. The method of acoustic tensometry based on the ratio of longitudinal and shear wave velocities proposed by the specialists of NPO “Energomash” is described. The application of the method of acoustic strain gauge tightening of detachable joints, along with the improvement of the LPRD production technology, made it possible to completely eliminate leakage and leakage failure.

Determination of plastic deformation with variable ultrasonic excitation positions

For highly stressed mechanical components, information regarding the beginning of plastic deformation is of enormous importance. Therefore, nondestructive testing and structural health monitoring techniques are essential to examine said components and to make statements concerning the mechanical integrity. In this work, dislocation theory was extended and combined with ultrasonic wave excitation to obtain dislocations in isotropic materials. In the analytical derivation, the ultrasonic longitudinal waves were sent in different propagation directions relative to the uniaxial tensile load. The derived nonlinearity coefficients enabled the investigation as a function of these angles. The evaluated coefficient behaviour allows for statements about the position of the ultrasonic excitation relative to the tensile load to be made. Furthermore, a signature could be derived from which the degree of plasticity can be determined if a reference measurement is available. The newly derived coefficients and their behaviour make it possible to efficiently detect the beginning of plastic deformation and to predict the position of the applied load vector.

Miniaturized acoustic concentrators for ultrafast 3D ultrasound imaging

Ultrafast 3D ultrasound imaging is a rapidly growing research field that enables real-time imaging at a high frame rate and in a non-invasive manner. Currently, to achieve ultrafast 3D ultrasound, plane or diverging waves from virtual sources are used. These virtual sources can be considered as focal points during emission, allowing for improved transmission of ultrasonic energy. However, they have limitations in terms of transmitted energy, complex electronics, and timing issues, which impact the quality of the resulting images. To address this, a study was conducted to design and experiment with new miniaturized ultrasound transmitters based on cylindrical waveguides with tapered sections. These transmitters, with a diameter of approximately 100 μm, can replace the virtual sources. A numerical study based on 2D axisymmetric Finite Element Modeling (FEM) is first performed to model the transmission and reflection of longitudinal ultrasonic waves through various cylindrical rods. The results demonstrated that the transmission depends on the diameter ratio, frequency and longitudinal mode order (L0, L1, L2, etc.). An experimental study is then conducted on a stainless steel waveguide instrumented with 6mm piezo discs. The mechanical energy, estimated using Laser Doppler Vibrometer is transmitted through a 150 μm diameter rod, allowing mechananical focusing in the frequency range between 0.5 and 5 MHz. The application of this method to separate emission/reception transducers is then demonstrated for 3D ultrafast imaging.

A novel pulse-echo piezoelectric transducer for detecting quasi-static component induced by an ultrasonic longitudinal wave

For effectively detecting the quasi-static component (QSC) of an ultrasonic longitudinal wave, which is closely related to the elastic nonlinearity of material, we proposed a novel pulse-echo piezoelectric transducer consisting of a high-frequency piezoelectric wafer, a frequency selective isolation layer, a low-frequency piezoelectric wafer, and an acoustic backing. The high-frequency wafer generates the primary longitudinal wave (PLW) tone burst, while the high- and low-frequency wafers receive the pulse echo containing both the PLW component and QSC, respectively. We analyze the pulse-echo formation of the high-frequency PLW tone burst in a specimen, and conduct numerical simulations and experiments to validate the effectiveness of the proposed transducer. The results demonstrate that the low-frequency receiver is more efficient at detecting the QSC, even though the high-frequency wafer can also receive the echo of the QSC pulse. Specifically, the QSC pulse can still be detected by the low-frequency receiver when the high-frequency PLW tone burst is completely attenuated. The novel pulse-echo transducer proposed in this paper expands the design perspectives for transducers used in ultrasonic non-destructive testing.

Nondestructive testing of local microcracking in laboratory mineral samples using an acoustic technique with a laser source of ultrasound and its verification with x-ray computer tomorgaphy

An acoustic technique of nondestructive testing of a local microcracking degree in laboratory mineral samples is proposed based on laser generation of ultrasound. A spectral power of broadband signals of longitudinal ultrasonic waves is measured, which are generated by absorption of pulsed laser radiation in a special material served as a laser source of ultrasound and further scattered on microcracks in samples (the so called structural noise power). The direct relationship between an increase in microcracking and a growth in the structural noise power in scanning regions of the samples has been obtained for feldspars of two types. For the first time, an independent method of X-ray computer tomography of the complex-shaped samples confirmed the reliability of the results of acoustic measurements. The established relationship between the local microcracking and structural noise power can be used in the monitoring systems for observing the crack formation in rocks and minerals under different external loadings.

Efficiency enhancement and application of laser ultrasonic longitudinal wave based on glass constraint

Due to the weak longitudinal signals generated by laser ultrasound in the thermoelastic mechanism, the characteristic echoes are weak when evaluating the interior of solids, thus limiting its application to internal defect detection. A glass confinement layer is introduced to enhance the longitudinal excitation effectiveness. Specially, a thermoelastic model of laser ultrasound with a glass confinement is established to explain the mechanism of the enhancement of the longitudinal wave effectiveness, and the effect of the glass width on the longitudinal wave generated by the base ultrasound is investigated. The effect of the glass confinement layer on the enhancement of the effectiveness of the internal defects detection is studied. The simulation and experimental results show that the longitudinal waves with high signal-to-noise ratio induced from thermoelastic effect are excited similar to the ablation mechanism, which greatly improves the excitation efficiency of the longitudinal waves. The deep detection defects and the accurate localization of depth information are realized with an error of no more than 1.2%.