Characteristics Of Ultrasonic Waves Research Articles

Ultrasonic wave characteristics in multiscale cementitious materials at different stages of hydration

Monitoring the microstructural change in cementitious materials during hydration is an essential but challenging task. Therefore, a non-invasive and sophisticated technique is warranted to understand the microscopic behaviour of the multiphase cementitious materials (where the length scale of the constituents varies from centimeters to micrometers) in different stages of hydration. Due to exothermic hydration reactions, different hydration products start to evolve with individual mechanical properties. In concrete, an interface transition zone (ITZ) appears between the aggregate surface and paste matrix, which influences the overall properties of concrete material. In the present research, 1) several wave characteristics, such as wave velocity, energy distribution, and signal phase are found out using Ultrasonic Pulse Velocity (UPV), Wavelet Packet Energy (WPE) and Hilbert Transform (HT) methods, to monitor the hydration mechanism (1d-28d) in cement-based materials with two levels of heterogeneities (cement paste and concrete, representing microscale and mesoscale, respectively). Also, the unique nonlinear behaviour is studied in the frequency domain using the promising Sideband Energy Ratio (SER) and Sideband Peak Count Index (SPC-I) methods. 2) Numerical simulations are carried out to understand the wave interaction in the developing microstructure. A discretized microstructure of cement shows microscopic details of each phase at any instant of hydration (e.g., formation stage and after complete maturity level). The experimental and numerical investigations on the characteristics of the nonlinear ultrasonic wave propagation show the impact of microstructural development of multi-scale cementitious materials during hydration.

Modelling and simulation for the investigation on the ultrasonic propagation mechanism in advanced microelectronic packages

The miniaturisation, ultra-thinness and high-density multi-layer structure of advanced microelectronic packages complicate the propagation mechanism of ultrasonic waves. In this paper, a finite element model is used to simulate ultrasonic wave propagation in flip chip packages, investigating the laws of transmission and reflection at the lamination boundaries. The acoustic field of ultrasonic transducers is simulated using MATLAB and Abaqus software. The angular spectrum method (ASM) based on the Fourier transform is adopted to more precisely reveal the distribution characteristics and attenuation relationship of near‐field ultrasonic waves. The influence of the frequency and size of the ultrasonic transducer on the propagation characteristics of ultrasonic waves is analysed. Based on an acoustic field map generated by the detection model, the waveform conversions of acoustic waves in a multi-layer structure are analysed. The results show that ultrasonic waves are mainly presented in the form of reflected and transmitted waves at the layered interface and the model with a perfectly matched layer (PML) has higher accuracy. Therefore, this method is applied to ultrasonic testing in a flip chip package, which cannot only effectively exclude interference from boundary reflection but also greatly improve the reliability of waveform conversions analysis.

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.

Influence of surface roughness on laser ultrasonic detection for laser powder bed fusion manufactured 316L stainless steel

In view of the non-destructive and non-contact features, laser ultrasonic (LU) technology has long been the effective method to detect tiny defects for laser powder bed fusion (LPBF) additive manufactured specimens. Of larger concern is the variation and the corresponding mechanism on tested results of LU detection as the property of LPBF additive manufactured specimen is changed. Aiming at the property of surface roughness, this work investigated the propagation characteristics of excited ultrasonic waves in LPBF additive manufactured 316L stainless steel with different surface roughness, as well as the interaction between ultrasonic waves and artificial submillimeter holes. Both numerical simulated and experimental study were conducted. Simulated results revealed that the amplitudes of longitudinal wave (L wave) and its echo wave L1 at the holes exhibited a discernible increase as the surface was coarser. The increase in surface roughness was detrimental to the resolution of defect detection as was expected from the increased amount of noise. LPBF fabrication and the subsequent LU pulse-echo detection were conducted for 316L stainless steel. Both B-scan and C-scan were able to detect the holes with the diameter of 0.6 mm. The speckle phenomenon deriving from the increase in surface roughness emerged, corresponding to the increased ultrasonic signal energy but deteriorated resolution of detected images. It is feasible to optimize LU detected effect by minimize the surface roughness of tested specimens.

Laser ultrasonic detection of submillimeter artificial holes in laser powder bed fusion manufactured alloys

In the development of additive manufacturing (AM) technology, laser powder bed fusion (LPBF) is one of the important processing methods. However, the hole defects in the fabricated samples limit the development. Laser ultrasonic (LU) technology plays a major role in the detection of LPBF parts with tiny defects, which has the advantages of non-contact and non-destructive. In this work, the detection of submillimeter internal defects in four typical LPBF alloys by LU technology is studied numerically and experimentally. A multiphysics simulation model of LU detection is established to investigate the propagation characteristics of excited ultrasonic waves in different LPBF alloys and their interaction with submillimeter artificial defects. Simulation results show that the amplitude of longitudinal (L) wave at the defect is the largest in AlSi10Mg alloy, and the amplitude of L wave in the 316L alloy, Ti6Al4V alloy and In718 alloy are very close, but their phases are slightly different. The amplitude of L wave tends to decrease nearly linearly with the increase in defect diameter. Then, four typical LPBF alloys are fabricated and measured by the LU through-transmission detection. The geometric information of artificial holes with a diameter larger than 0.2 mm are clearly characterized by the LU C-scan results, indicating the prominent applicability and feasibility of LU detection on different materials fabricated by LPBF.

Propagation characteristics of ultrasonic in SLM manufactured AlSi10Mg

Porosity is a crucial quality evaluation criterion in metal additive manufacturing. To investigate the propagation characteristics of ultrasonic longitudinal waves with different incident frequencies in AlSi10Mg prepared by selective laser melting, specimens with varying porosity were created using printing process adjustments. Ultrasonic longitudinal wave tests and COMSOL simulations based on 2.5 MHz, 3.5 MHz, 5 MHz, and 7.5 MHz incident frequencies were carried out to establish a linear relationship between average wave velocity, average attenuation coefficient, and porosity at different frequencies. Results indicate that sound velocity and porosity are inversely proportional for each frequency longitudinal wave, while the attenuation coefficient is proportional to the porosity. Linear fitting expressions suggest that the best fit for both sound velocity and attenuation coefficient occurs at 5 MHz. Simulation results demonstrate that using 5 MHz as the incident frequency can better balance detection sensitivity and linearity. These findings provide more data support for establishing the intrinsic connection between acoustic parameters and porosity of AlSi10Mg prepared by selective laser melting in the selected area and serve as a reference for selecting ultrasonic incident frequencies in practical inspection.

Simulation of wave propagation in austenitic stainless steel welds with solidification structure predicted by Cellular Automaton method

Austenitic stainless steel is widely used in nuclear power plants (NPPs) and a variety of occurrences of stress corrosion cracking (SCC) near its weld have been reported among NPPs. Ultrasonic testing is a critical technique for the detection and depth sizing of SCCs. However, such welds' anisotropic and heterogeneous properties cause difficulties in ultrasonic testing when ultrasonic waves propagate through welds. Deeply understanding the characteristics of ultrasonic waves with wave propagation simulation is effective to improve the accuracy of ultrasonic testing. To this end, it is necessary to take crystal orientation and grain boundary into account simultaneously in the numerical model. In this study, a model was developed so that the Cellular Automaton (CA) method can simulate the solidification structure from multilayer and multipass welding process, then the solidification structure of a 7-layer and 7-pass weld of austenitic stainless steel was predicted based on welding conditions. Finally, the finite element method was used to compute wave propagation in austenitic stainless steel weld with the solidification structure predicted. Numerical results of wave propagation in austenitic stainless steel weld were compared to those obtained by experiment.

Propagation Characteristics of Ultrasonic Waves Generated by Phased Array Laser in Coating/Substrate Structure

Propagation Characteristics of Ultrasonic Waves Generated by Phased Array Laser in Coating/Substrate Structure

Electromagnetic Ultrasonic Shear-Horizontal Wave to Detect Corrosion Defect of Flat Steel for Grounding Device of Transmission Pole Tower

Detecting defects in grounded flat steel is essential for ensuring the safety and reliability of transmission tower grounding devices. However, traditional inspection methods, such as physical excavation and verification, are costly and time-consuming. This paper proposes a corrosion defect detection method for flat steel transmission tower grounding devices based on electromagnetic ultrasonic SH waves. In addition, using commercial software, a three-dimensional finite element simulation model of grounded flat steel with simulated pitting corrosion defects is constructed. The specified displacements applied to multiple surface sources mimic the horizontal shear vibrations generated by the electromagnetic ultrasonic transducer on the surface of the grounded flat steel during actual inspection. A simulation was used to investigate the propagation and attenuation characteristics of shear-horizontal ultrasonic SH0guided waves for simulated corrosion defects with various geometric configurations in grounded flat steel. The simulation investigated the propagation and attenuation characteristics of the SH0 wave in grounded flat steel and the detection of various defects for linear analysis of the results. The simulation results show that the attenuation of the electromagnetic ultrasonic guided wave is small, at only 0.0016 dB/mm, and the displacement amplitude of the echo signal decreases with the increase of the SH0 wave propagation distance. Increasing the depth and length of corrosion defects increases the echo signal amplitude. At the same time, the width of corrosion defects has little effect on the echo amplitude. Finally, a flat steel defect detection experiment was conducted, and the experimental results fit with the simulation to verify the accuracy of the simulation model. This detection method introduces a new idea for the on-site detection and quantitative identification of corrosion defects in grounded flat steel, which has significant reference value and can provide a more effective and economical method for ensuring the safety and dependability of transmission tower grounding devices.

Research on Partial Discharge Detection of Switchgear Based on Ultrasonic Signal Characteristic

With the rapid development of power systems, the switchgear, which is widely used, plays an increasingly important role. Partial discharge is one of the main causes of insulation failure of the switchgear, which is a serious threat to personal and equipment safety. In this paper, the partial discharge of the switchgear is detected based on the ultrasonic method. According to the characteristics of ultrasonic waves generated by partial discharge, a partial discharge detection method for the switchgear based on the characteristics of ultrasonic wave signal is designed. The wavelet threshold denoising algorithm is used to denoise the ultrasonic signal and draw the partial discharge phase distribution map by using the characteristics of low amplitude and wide frequency distribution of the interference signal. Finally, the improved support vector machine algorithm is used to identify and diagnose four types of discharge based on 280 groups of experimental data. By adjusting the kernel function and optimizing the support vector machine algorithm, the final recognition accuracy is more than 90%.

Using nonlinear ultrasonic measurements to estimate parameters of the sedimentation of slurry solid phase in thickener

Purpose. Improvement of the method for estimating sedimentation process parameters of the slurry solid phase particles in thickener on the basis of measurements of the nonlinear characteristics of ultrasonic waves propagating in a controlled medium. Methodology. The following methods were used: analysis of scientific results and practical developments; methods of mathematical statistics for evaluating the results of experiments; methods of analytical synthesis; methods of numerical modeling for the synthesis and analysis of a mathematical model. Findings. It was established that the nonlinearity of the process of propagation of ultrasonic waves in ore slurry, which is determined by the number and size of crushed ore particles in it, can be estimated by determining the amplitudes of several harmonics of the measured acoustic signal. This approach allows maintaining the productivity of the desliming process in accordance with the characteristics of the ore suspension, without allowing the loss of valuable components. Obtaining real-time information about the characteristics of the particle sedimentation process in the ore suspension at the initial stage enables reducing the duration of transitional processes in the control system. Originality. The method for estimating the parameters of the deposition of the solid phase of the pulp in the thickener has been improved, which is based on the fact that the nonlinearity of the process of propagation of a controlled ultrasonic signal in the thickener; this leads to modulation of the generated ultrasonic packet and, consequently, the appearance of higher harmonics. To obtain a more accurate estimate of the nonlinearity of this process, all the values obtained must be normalized to represent only the relative changes in the acoustic nonlinear response. Practical value. A system for automatic control of the thickener operation is proposed, which uses nonlinear ultrasonic measurements to estimate the parameters of the sedimentation of the solid phase of the pulp in the thickener. According to the results of industrial tests of the system of automatic control of the thickener based on ultrasonic control devices, it was established that its use as part of the automated control system for the technological processes of beneficiation of iron ore raw materials at the ore beneficiation factory of the Northern mining works will allow reducing water consumption by 3.5 % and iron-magnetite losses by 0.6–0.7 %.

An Interface Pressure Detection Method of Cable Silicone Rubber-XLPE Based on Nonlinear Ultrasound

The interface pressure between the cable attachment and the body is crucial for the stable long-term operation of the cable. To solve the issue of interface insulation characteristics’ damage caused by the pressure transducer measurement method, a non-destructive testing method of silicone rubber interface pressure using nonlinear ultrasound is presented. Initially, the study analyzes the propagation characteristics of ultrasonic waves at the interface of cross-linked polyethylene and silicone rubber. The study also establishes the relationship between the nonlinear coefficient and the interface pressure. Subsequently, a nonlinear ultrasonic test platform is constructed using the pulse reflection method to measure the interface pressure of flat silicone rubber and cross-linked polyethylene through nonlinear ultrasonic testing. Theoretical and experimental results indicate that the fundamental amplitude of the frequency domain of the interface reflection wave decreases, and the second harmonic amplitude and nonlinear coefficient both increase as pressure increases. These results demonstrate that the nonlinear ultrasound, non-destructive testing method can accurately evaluate the interfacial pressure state of the cable accessories.

Research on ultrasonic phased array detection algorithm for TA15/Ti2AlNb multi-layer gradient material structure

Conventional ultrasonic detection methods can detect a TA15/Ti2AlNb gradient material multi-layer structure with many layers; the reflection and refraction phenomena of ultrasonic waves at the partition interface result in considerable attenuation of ultrasonic energy. It is difficult to achieve accurate focusing control of multi-array element synthetic beams, and internal defects cannot be detected. We explored the ‘ultrasonic velocity scale coefficient K’ algorithm to determine the ultrasonic beam propagation refraction path of a multi-layer gradient material structure. The algorithm makes full use of the refraction characteristics of ultrasonic waves on each material layer interface, establishes the acoustic ray-tracing model, analyzes the acoustic ray-tracing propagation path of each array element, and quickly obtains the focusing law. A TA15/Ti2AlNb gradient material specimen was prepared using laser melting deposition (LMD) technology, and a multi-layer structure model was established based on the finite difference time domain (FDTD) method to verify the focusing law. The experimental results of the ultrasonic phased array showed that the proposed algorithm effectively improved the defect detection signal-to-noise ratio (SNR) and imaging quality of the TA15/Ti2AlNb gradient material.

Method for Recognizing Pressing Position and Shear Force Using Active Acoustic Sensing on Gel Plates

A touch interface is an important technology used in many devices, including touch panels in smartphones. Many touch panels only detect the contact position. If devices can detect shear force in addition to the contact position, various touch interactions are possible. We propose a two-step recognition method for recognizing the pressing position and shear force using active acoustic sensing, which transmits acoustic signals to an object and recognizes the state of the object by analyzing its response. Specifically, we attach a contact speaker transmitting an ultrasonic sweep signal and a contact microphone receiving ultrasonic waves to a plate of gel. The propagation characteristics of ultrasonic waves differ due to changes in the shape of the gel caused by the user's actions on the gel. This system recognizes the pressing position and shear force on the basis of the difference in acoustic characteristics. An evaluation of our method involving a user-independent model confirmed that four pressing positions were recognized with an F1 score of 85.4%, and four shear-force directions were recognized with an F1 score of 69.4%.

Neutral Temperature Estimation of Continuous Welded Rails using Group Velocity of Ultrasonic Waves

This study proposes a neutral temperature estimation technique of continuous welded rails using group velocity of ultrasonic waves. In case of boundary-confined metallic structures, especially civil infrastructures exposed to harsh environmental conditions such as continuous welded rail, thermal stress is one of the critical control factors to avoid structural breakage and buckling. It has been known that the ultrasonic wave propagation is sensitive to target structure’s stress variation, so that the neutral temperature can be determined based on the propagation characteristics of stress-dependent ultrasonic wave. To numerically investigate the stress-dependent ultrasonic wave behavior, a 3D rail model with 1 mm mesh size was constructed using actual material property and dimensions of KR60 rail. Here, the two boundary conditions, i.e., Fix-Free and Fix-Fix boundary conditions, applied to the 3D model so that neutral temperature is extracted. The simulation results showed that the group velocity of ultrasonic waves was consistently decreased on the Fix-Free boundary condition according to temperature increase. Similarly, the group velocity on the Fix-Fix boundary condition was also decreased, but the decrement of group velocity was less than the Fix-Free boundary one due to thermal stress. Based on the observation, the stress-dependent group velocity trends can be estimated using the difference between the Fix-Free and Fix-Fix boundary resultants. Finally, the neutral temperature can be estimated by picking up the cross point of two group velocity trend graphs.

Numerical analysis of ultrasonic wave propagation and scattering in oligo-crystalline materials

Oligo-crystals contain only a few crystalline grains and are often used in the fields of micro-electromechanics, turbine blades and shape memory alloys. To date, there has not been any study on the ultrasonic evaluation of oligo-crystals. In this work, we modeled the microstructure of oligo-crystalline copper foil using the phase field method, and carried out a finite element analysis of the oligo-crystal. Data were generated through multiple simulations and the data were analyzed statistically to assess the effects of ultrasonic testing configuration, the size of the transducer aperture, the types of texture, and the internal flaws on the propagation and scattering characteristics of ultrasonic waves. The results showed that the majority of conventional ultrasonic evaluation techniques failed to work for oligo-crystals. Firstly, ultrasonic velocity and attenuation coefficient in a given oligo-crystal are not constant when measured in different ultrasonic configurations and with different aperture sizes. Secondly, oligo-crystals are characterized by a rather low level of grain noise, possibly due to the low density of grain boundary. Thirdly, for a side drilled hole of a given size and depth in an oligo-crystal, the simulated amplitude and time-of-flight of flaw echoes are highly variable, which makes flaw location and flaw sizing very difficult. More in-depth research on physical modeling and experimental verification of ultrasonic testing are clearly needed for oligo-crystals in the future.

Research on the defect detection of carbon fiber reinforced polymer based on pulse laser ultrasound

The accumulation of micro damage such as matrix crack and fiber fracture in carbon fiber reinforced polymer (CFRP) under cyclic loading will seriously affect the mechanical properties of CFRP. The size of micro damage is small and the location is scattered, so it is difficult to identify accurately by traditional nondestructive testing methods. Laser ultrasonic testing technology has the advantages of non-contact, fast detection speed and wide measurement range, especially combining the advantages of long-distance excitation and large angle incidence of laser, it has great potential in the damage detection of large-scale and curved structure materials. In this paper, based on the laser thermos-elastic effect, the generation process and propagation characteristics of ultrasonic wave in CFRP are systematically studied on the basis of analyzing the distribution of temperature, stress and displacement fields after laser acting on CFRP. By analyzing and comparing the ultrasonic echo signals of different defects characteristics in CFRP, the defect depth and length are calculated based on the time when the longitudinal wave scattering wave (Lr) reaches the detector. The calculation results show that the errors of this method are about 7 % and 5 % for the detection of the depth and length of the CFRP.

Laser ultrasonic nondestructive evaluation of sub-millimeter-level crack growth in the rail foot weld.

Laser-generated ultrasonic wave characteristics in the rail foot weld were simulated and reported for qualitative analysis and evaluation of sub-millimeter-level crack growth. Numerical analyses using the finite element method (FEM), the propagation characteristics, and displacement field distribution of a laser-generated ultrasonic wave after the interaction with cracks were fully demonstrated. By calculating displacement amplitude distribution, the optimal sensing position and area were the laser incident point and the upper surface, respectively. Crack growth degree toward the rail bottom and axial direction can be confirmed by analyzing time and amplitude of the echoes originating from the rail bottom and crack surface reflection. By combining time with peak intensity of the echo reflection from the rail bottom, the sub-millimeter-level crack growth process inside the rail foot weld is capable of acquiring and evaluating. The results justify that the laser ultrasonic technique, characterized by laser excitation and laser detection, is a competitive nondestructive testing technique for sub-millimeter-level crack growth evaluation and detection inside the rail foot weld.

Designing a Conversation Support Tool for Quiet Environments by Focusing on the Characteristics of Ultrasonic Waves

AbstractIn a quiet environment, even a small noise attracts the attention of the people around. In order to reduce the stress of speakers, listeners, and other people around them, we devised a tool to support conversation by converting voice into ultrasonic waves and outputting them from parametric speakers to deliver the sound to the conversation partner. Since light materials can be used for soundproofing ultrasonic waves, we used cardboard and newspaper as soundproofing materials. We confirmed that the sound converted by the tool can be used for conversation and soundproofed.

Ultrasonic Coda Wave Experiment and Simulation of Concrete Damage Process under Uniaxial Compression

Using the coda wave interferometry (CWI) method to obtain the ultrasonic coda wave characteristics of loaded concrete is an important method to evaluate the mechanical response of concrete. In this paper, the ultrasonic coda wave characteristics of C40–C70 concrete specimens (four strengths of concrete) under uniaxial compression were tested by laboratory experiments. Furthermore, to clarify the relationship between the internal damage process of concrete and the change rate of coda wave velocity, an ultrasonic coda wave discrete element simulation model combined with digital image processing technology was established. The results show that the coda wave is very sensitive to small changes in the compressive damage to concrete, and the change in coda wave velocity can correspond to the development process of concrete damage. This research is conducive to a better understanding of the complex material behavior of compressive concrete and proves the feasibility of ultrasonic field simulation and processing by using numerical simulation images of concrete damage.