Ultrasonic Experiments Research Articles

Simulation study of turning-ultrasonic rolling compound processing for 42CrMo steel

The ultrasonic rolling processing technology has been shown to significantly reduce surface roughness and enhance the residual stress of parts, thereby improving their surface properties and extending their service life. This technology is particularly effective for the precision machining and surface strengthening of ultra-high-strength steel 42CrMo. This study aims to investigate the impact of turning pre-processing on the distribution of residual stress during ultrasonic rolling, a simulation model incorporating turning pre-processing was developed and used to conduct ultrasonic rolling simulation experiments, enabling the analysis of residual stress distribution patterns. Concurrently, ultrasonic rolling strengthening experiments were performed to validate the accuracy of the simulation model. The results confirm that with increasing rotational speed and feed rate, residual stress decreases, whereas with increasing static pressure and amplitude, residual stress increases. The residual stress variation obtained from the simulation of combined turning and ultrasonic rolling closely matched the results of experimental ultrasonic rolling tests. This consistency validates the accuracy of the simulation model. This study offers a novel approach for simulating and experimentally validating ultrasonic rolling processes, particularly for shaft-like parts that undergo turning as a pre-processing step.

Ultrasonic Rough Crack Characterization Using Time-of-Flight Diffraction With Self-Attention Neural Network.

Time-of-flight diffraction (ToFD) is a widely used ultrasonic nondestructive evaluation (NDE) method for locating and characterizing rough defects, with high accuracy in sizing smooth cracks. However, naturally grown defects often have irregular surfaces, complicating the received tip diffraction waves and affecting the accuracy of defect characterization. This article proposes a self-attention (SA) deep learning method to interpret the ToFD A-scan signals for sizing rough defects. A high-fidelity finite-element (FE) simulation software Pogo is used to generate the synthetic datasets for training and testing the deep learning model. Besides, the transfer learning (TL) method is used to fine-tune the deep learning model trained by the Gaussian rough defects to boost the performance of characterizing realistic thermal fatigue rough defects. An ultrasonic experiment using 2-D rough crack samples made by additive manufacturing is conducted to validate the performance of the developed deep learning model. To demonstrate the accuracy of the proposed method, the crack characterization results are compared with those obtained using the conventional Hilbert peak-to-peak sizing method. The results indicate that the deep learning method achieves significantly reduced uncertainty and error in rough defect characterization, in comparison with traditional sizing approaches used in ToFD measurements.

Integrated detection for open and closed surface fatigue cracks utilizing scanning laser source-induced Rayleigh wave fields with self-reference peak-to-peak features

In this study, the integrated detection method for open and closed surface fatigue cracks is investigated. Firstly, the finite element simulation models are established to investigate the interaction between scanning laser source-induced Rayleigh waves and open and closed surface fatigue cracks, and the laser ultrasonic detection experiments are conducted for fatigue specimens containing fatigue cracks in different states. The simulation and experimental results indicate that the variation patterns in the peak-to-peak values of Rayleigh waves with horizontal scanning positions for open and closed cracks exhibit both similarities and differences. Subsequently, an integrated detection method based on self-referenced peak-to-peak features is proposed, which utilizes the similarities and differences to detect and distinguish open and closed cracks, respectively. Furthermore, this proposed method is experimentally validated, indicating that it can achieve accurate integrated imaging of open and closed cracks that have a high degree of agreement with the SEM images of the cracks. Additionally, the proposed method achieves a detection error of 2 % for the vertical lengths of the fatigue cracks. This study can provide guidance for integrated real-time detection of open and closed surface fatigue cracks of mechanical components in service.

Analysis and numerical simulation of different flowmeters based on an open channel in an irrigation area

ABSTRACT This study establishes an ultrasonic open channel flow measurement test and numerical simulation model and systematically compares the performance and reliability of the ultrasonic method and the traditional flowmeter in flow measurement in the irrigation area by observing and analysing the test data and combining it with the numerical simulation. In the indoor ultrasonic flowmeter flow measurement experiments in the trapezoidal nullah section, the flow rate measurement was carried out by using a high-precision variable slope flume and a variety of flow measurement tools. A numerical study was carried out using the VOF method to calculate the flow in the open channel flume under two-phase flow conditions. Combining experimental measurements and numerical simulations, this study aims to quantify the magnitude of flow measurement errors and water surface fluctuations in open channel flumes and to address the discrepancies between different flow measurement methods in open channels in irrigation areas.

Ultrasonic backscattering measurement of hardness gradient distribution in polycrystalline materials

It is crucial to obtain the internal hardness distribution in polycrystalline materials to evaluate the mechanical performance of components and monitor their service life. Current methods, however, fail to meet the non-destructive evaluation needs for materials with hardness gradient distributions. This paper, based on the principle of grain boundary scattering of ultrasound in polycrystalline materials, combined with the Transverse-to-Transverse Singly-Scattered Response (T-T SSR) theory, proposes an ultrasonic SSR model adapted to hardness gradient distributions. The model elucidates the influence of hardness gradient variations and grain dispersion on ultrasonic scattering. Using DREAM.3D, seven different-scale polycrystalline volumes were constructed to assess the relevance of volume-weighted average grain size and spatial correlation of hardness gradient materials. Finally, induction quenching was applied to 40Cr to induce a gradient hardness distribution internally, followed by ultrasonic backscatter experiments. The results indicate that the theoretical model and the spatial variance of measured signals align well over a relatively long time window. For the specimen with minor curvature, the theoretical hardness distribution obtained by the model is accurate, with an average error of 2.55 % compared to destructive testing data. However, the results for the larger curvature reveal limitations in the model.

Piezoelectric Ultrasonic Local Resonant Ultra-Precision Grinding for Hard-Brittle Materials.

Hard-brittle materials are widely used in the optics, electronics, and aviation industries, but their high hardness and brittleness make it challenging for traditional processing methods to achieve high efficiency and superior surface quality. This study aims to investigate the application of ultrasonic local resonant grinding to sapphire to improve the efficiency and meet the requirements for the optical window in the surface roughness of the material. The resonant frequency of a piezoelectric ultrasonic vibration system and the vibration amplitude of a grinding head's working face were simulated and tested, respectively. The results of ultrasonic grinding experiments showed that the local resonant system reduced the surface roughness parameter (Ra) of sapphire to 14 nm and improved its surface flatness to 44.2 nm, thus meeting the requirements for the ultra-precision grinding of sapphire. Compared with a conventional resonant system, the surface roughness of the sapphire ground with the local resonant system was reduced by 90.79%, its surface flatness was improved by 81.58%, and the material removal rate was increased by 31.35%. These experimental results showed that ultrasonic local resonant grinding has better effects than those of conventional ultrasonic grinding in improving surface quality and increasing the material removal rate.

A New Process of Chemical Plating Ni-P Electromagnetic Induction Heating Activation on the Surface of Aluminium Alloy Base Material

Nowadays, there are many surface treatment methods for aluminium alloys; the most commonly used of these is the chemical dip galvanizing process, which is complicated due to its use of large quantities of corrosive drugs. In order to simplify the process, this paper proposes a new electromagnetic induction heating activation method instead of the zinc dipping process. The method works as follows: The substrate is first degreased and then activated. The activation process starts by soaking the degreased substrate in an activation solution, taking it out after ten minutes, and placing it into an induction heating unit. The activation solution is sprayed onto the surface of the substrate while heating, using the energy generated by high temperatures to complete the activation reaction. The surface of the activated substrate forms a nanoscale film of nickel, which is finally utilised as a catalytic centre for ENP (an advanced surface treatment process that deposits a very uniform layer). The optimisation of important parameters of the non-destructive activation process was determined using the L9 Taguchi method. The main parameters ranged from 0.15 L/min to 0.25 L/min for spray rate, 200 °C to 400 °C for heat treatment temperature, and 1:4, 1:5, and 1:6 for Ni2+ and H2PO4− ion concentration ratios. The above data were derived from a single variable and were analysed using Minitab 20 software. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), energy spectrometry (EDS), and ultrasonic experiments were used to characterize and analyse the surface morphology, composition, and bond strength of the coatings. The results show that the nanoscale nickel particles can completely cover the surface of the substrate, forming a layer of nano-film. After activation and ultrasonic cleaning for 30 s at an ultrasonic frequency of 40 KHz and a power of 80 W, the surface nano-film was not destroyed, which proves that it had a high bonding strength. After the application of the plating, the plated surface had a compact microstructure, and the continuity was good. Therefore, compared with the currently commonly used zinc dipping process, this process has the advantages of being a low-cost, simple operation, and non-destructive and environmentally friendly activation process for the substrate.

Ultrasonic TFM imaging inspection of large complex rings using defect quantitative evaluation mappings

ABSTRACT Large complex rings are widely used in wind power energy, aerospace, large construction machinery. There are different scales of defects in the manufacturing process for large complex rings. Because of the complex cross-section and large thickness, it is difficult to quantitative evaluation of defects by conventional ultrasonic technology. Therefore, the ultrasonic total focusing method (TFM) defect quantitative inspection for large complex rings is proposed in this paper. First, the TFM inspection technology of large complex rings for simultaneous scanning of the end-face and side-face is designed. Then, the maximum amplitudes of defects are collected at each grid point of the imaging area by the TFM inspection of calibration specimens. The Φ1.5mm defect quantitative evaluation mappings are obtained by the interpolation fitting algorithm. Finally, the ultrasonic TFM and B-scan inspection experiments of the Φ3440mm large ring are carried out. The results show that the TFM quantitative evaluation mapping has higher accuracy compared to the conventional B-scan method. Especially for the Φ1.5mm defects, the average error of TFM quantitative evaluation is 2.92%. The proposed method can effectively identify defects of other sizes that exceed the calibration mapping. This work has industrial application value for developing ultrasonic TFM inspection of large complex components.

Interface stiffness identification of rough and weak bonded interface using developed ultrasonic reflection phase derivative spectrum

The thickness and interface roughness of coatings both affect the interface bonded quality. Existed ultrasonic testing methods based on traditional phase screen approximation or spring model assumption are difficult to simultaneously identify the interface roughness and stiffness of coating. This paper, a new method for integrated identifying coating thickness, interface roughness, and interface stiffness using developed ultrasonic reflection phase derivative spectrum (URPDS) is proposed. A phase-screen-approximated spring-model (PSASM) for ultrasound vertically propagating into rough and weak bonded interface is constructed. On basis of PSASM, a URPDS of coating/substrate structure is developed for identifying the interface stiffness and other parameters of coated parts. Cross-correlation analysis is used to eliminate the phase deviation of URPDS introduced by reference signal and initial phase of tested signal. Sensitivity analysis is used to determine the high-sensitivity regions of URPDS to interface roughness and interface stiffness. Genetic algorithm optimization is used to achieve integrated identification of coating thickness, interface roughness, and interface stiffness. The rationality of PSASM is verified through numerical simulation using a series of coating/substrate models with rough and weak bonded interface, and the relationship between the high-sensitivity regions and the high-precision measurement ranges of interface roughness Rq and interface stiffness Kn is clarified. Ultrasonic experiments are implemented on Nickel-coating samples and coated parts using plane wave probe. The coating thickness, interface roughness, and interface stiffness could be identified accurately, which shows that the proposed URPDS method can identify the interface stiffness of rough contacted dissimilar media or coated parts with rough interface.

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.

SM-GMVAE: an intelligent model for defect quantification evaluation based on few ultrasonic signals

The conventional defect quantification evaluation approaches based on machine learning requires massive amounts of labelled defect signals, which is expensive and time-consuming works. This paper proposed a novel Similarity Metric Gaussian Mixture Variational Auto-Encoder (SM-GMVAE) model, which enables quantify defect with few labelled defect signals. The SM-GMVAE model is designed based on few-shot learning, which includes two modules: feature extraction (FE) module and similarity metric (SM) module. The FE module is designed to extract the feature of defect signal via the Variational Auto-Encoder (VAE). The SM module is used to measure the similarity of two defect signals based on the Gaussian Mixture Model (GMM). Moreover, sparse filtering techniques are used to enhance the sparsity of the features in the SM module. To validate proposed model, some specimens with four various depth defects are designed and fabricated for ultrasonic non-destructive testing experiments. A dataset with defects of different depths is established to compare proposed model with other methods. Our method obtains state-of-the-art experimental results with few labelled defect signals. Different from many published papers, our model is trained with few labelled data, which is more close to engineering practical application than other evaluation model trained using large numbers of labelled data. In other words, the developed approach can realize more complex defect evaluation tasks (such as: size, location, shapes, etc) at very low data labelling cost.

Phytochemical Study of Ethanol Extract of Gnaphalium uliginosum L. and Evaluation of Its Antimicrobial Activity.

This study evaluates the antibacterial and antifungal effects of ethanol extracts from Gnaphalium uliginosum L. derived from freshly harvested plant biomass, including stems, leaves, flowers, and roots. The extract was analyzed using gas chromatography-mass spectrometry (GC-MS) to determine its antimicrobial activity against phytopathogenic bacteria and fungi. Two methods were used in the experiments: agar well diffusion and double serial dilution. Extraction was carried out using the maceration method with different temperature regimes (25 °C, 45 °C, and 75 °C) and the ultrasonic method at various powers (63-352 W) for different durations (5 and 10 min). It was found that the 70% ethanol extract obtained through the ultrasonic experiment at 189 W power for 10 min and at 252 W power for 5 min had the highest antimicrobial activity compared to the maceration method. The most sensitive components of the extracts were the Gram-positive phytopathogenic bacteria Clavibacter michiganensis and the Gram-negative phytopathogenic bacteria Erwinia carotovora spp., with MIC values of 156 μg/mL. Among the fungi, the most sensitive were Rhizoctonia solani and Alternaria solani (MIC values in the range of 78-156 µg/mL). The evaluation of the antimicrobial activity of extracts using the diffusion method established the presence of a growth suppression zone in the case of C. michiganensis (15-17 mm for flowers, leaves, and total biomass), which corresponds to the average level of antimicrobial activity. These findings suggest that G. uliginosum has potential as a source of biologically active compounds for agricultural use, particularly for developing novel biopesticides.

Study on Denoising Method of Weld Defect Signal Based on SSA-VMD-WPD

Defects in welds can affect the structural safety and reliability of workpieces. Currently, the method of using phased array ultrasonic inspection technology for non-destructive testing of weld structures with high detection efficiency, good sensitivity, and good visualization of the results is widely used. However, the defective A-scan data collected by the ultrasonic phased array detector inevitably contain noise data, including the test piece material structure noise, equipment noise, and environmental noise, which undoubtedly affects the analysis of the A-scan signal. In addition, when defects are interpreted, the presence of noise also interferes with the process, which affects the accuracy of the interpretation. Therefore, to enhance the accuracy of defect identification based on phased array ultrasonic inspection technology, we must prevent the series of consequences caused by misjudgments. In this study, ultrasonic phased array inspection experiments were carried out, and the specific process flow of ultrasonic phased array inspection of flat plate butt welds was summarized. Utilizing pre-fabricated flat plate butt specimen blocks containing five types of typical defects, defect A-sweep signals based on ultrasonic phased array inspection were obtained. Combining the sparrow optimization algorithm (SSA), variational mode decomposition (VMD), and wavelet packet decomposition (WPD), a defect signal noise reduction method based on parameter optimization was studied. A noise reduction study was carried out using the noise-added simulated signal, and the results indicated that the noise reduction method proposed in this paper had a better noise reduction effect and the proposed method could effectively retain the detailed features of the ultrasonic phased array defective A-scan signal and realize the noise reduction processing of the defective A-scan signal.

Laser-excited surface acoustic wave method for detecting subsurface damage of processed silicon nitride ceramics

The non-destructive testing for subsurface damage of processed silicon nitride ceramics is significant to the improvement of processing technology and evaluation of product performance. A novel method for the measurement of subsurface damage based on dispersion of laser-excited surface acoustics wave is proposed in this paper. The subsurface damage distribution is quantified as the damage density and depth of the damage layer. The forward model of surface acoustics wave propagation in damage layer is derived by the stiffness matrix method. Bayesian inversion is applied to estimate model parameters and uncertainties of subsurface damage from the experimental dispersion data. Laser ultrasonic experiments are carried out on four samples with different substrate material parameters and surface qualities to demonstrate the feasibility of the method for detecting varying degrees of subsurface damage. The results prove that with reasonable use of prior information about damage depth predicted by surface roughness, subsurface damage with a depth ∼10 times smaller than the minimum wavelength of surface acoustics wave is accurately characterized. The reliability of the results is further verified by Vickers microhardness tester.

Hydrophobic C60-modified PVDF membrane with micro-nano structures for mitigating CaSO4 scaling in direct contact membrane distillation (DCMD)

Membrane scaling is a non-negligible problem for membrane distillation (MD) in the treatment of high-salinity wastewater (e.g., calcium sulfate and calcium carbonate). In this study, fullerene (C60) was adhered to a polyvinylidene fluoride (PVDF) membrane using a polydimethylsiloxane (PDMS) solution to create a micro-nano structure, fabricating the C60/PDMS-PVDF membrane. This membrane was then re-immersed in a PDMS solution to further reinforce the C60 nanoparticles on the surface, forming the PDMS/C60/PDMS-PVDF membrane. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to characterize the membrane surface morphology. Fourier transform infrared (FT-IR) was used to explore the membrane chemical composition. Liquid entry pressure (LEP) and water contact angle (WCA) measurements were employed to assess the membrane wettability. The results showed that C60-modification created the micro-nano structure on the membrane surface. The WCA of the PVDF membrane was 112.7 ± 2.4°, with a sliding angle far greater than 90°, whereas the PDMS/C60/PDMS-PVDF membrane exhibited a WCA of 147.9 ± 3.2° and a sliding angle of 6.3°. Compared to the virgin PVDF membrane, the LEP value of the PDMS/C60/PDMS-PVDF membrane increased from 68.4 ± 2.7 kPa to 87.2 ± 3.3 kPa. In direct contact membrane distillation (DCMD), a CaSO4 solution (2 g/L) was used to test the membrane performance. After 48 hours of operation, the flux of the PDMS/C60/PDMS-PVDF membrane remained at approximately 3.57 kg/(m2·h), and the salt rejection rate was over 99.96 %. This could be attributed to the C60 modification forming a micro-nano structure on the membrane surface, which trapped an air layer. This air layer could reduce the contact area between the crystal and the membrane, decrease nucleation probability, and shorten the residence time of liquid on the membrane surface. Additionally, the PDMS/C60/PDMS-PVDF membrane exhibited superior stability during the ultrasonic destruction experiment due to the encapsulation of PDMS. In summary, a novel hydrophobic membrane with a micro-nano structure was fabricated through C60 modification, offering superior anti-scaling properties and stability in treating high-salinity wastewater.

EBS status of the large-volume press at beamline ID06-LVP

ABSTRACT The European Synchrotron Radiation Facility (ESRF)'s large-volume press (LVP) instrument, at beamline ID06-LVP, is in constant evolution and made a significant step-change at the Extremely Brilliant Source upgrade; with improved beam characteristics (stability and focussing) and detection capabilities, with the installation of a custom-built Dectris 900 kW CdTe device. Over the same time-frame, higher pressure regimes have been reached through use of improved 6/6 compression, with the incorporation of a Drickamer device, and through the use of harder carbide grades in 6/8. The combined use of in-situ X-ray diffraction, imaging and pulse-echo ultrasonic high-pressure experiments has been enhanced. Temperature generation and measurement methods have been upgraded. User interaction is improved with live data inspection and treatment possible. Data calibration and integration have been thoroughly revised. Here, we describe the current status and highlight recent upgrades at ID06-LVP, with examples drawn from user measurements and in-house testing.

The influence of stress on the fracture and elastic properties of carbonate rocks controlled by strike-slip faults: a novel rock-physics modelling perspective

SUMMARY The fine-scale fractures within strike-slip faults substantially impact the flowing capacity. However, effective methods for their characterization are still lacking, making it challenging to predict hydrocarbon accumulation patterns. In this study, we conducted microscopic statistics, ultrasonic experiments and theoretical modelling to analyse the fracture density and elastic characteristics within the strike-slip fault and investigated the impact of stress. Our findings reveal that the fracture density in the fault core is 3–4 times higher than that in the damage zone, and the acoustic velocity is 13–18 per cent lower under atmospheric pressure. With the rising confining pressure, the fracture density initially decreases rapidly and then slowly, while the acoustic velocity follows the same increasing trend. The gradually slowing trend indicates that the majority of fractures close within the range of 0–20 MPa. Moreover, the stress sensitivity of the bulk modulus is higher than that of the shear modulus. The stress sensitivity is higher in the fault core than in the damage zone, which correlates strongly with the variation in fracture density. These indicate that the stress sensitivity in the fault-controlled rock is attributed to stress-induced fracture deformation, predominantly manifested as volumetric compression deformation. During the geological evolution, differences in tectonic faulting, fluid filling and compaction within the fault zone contribute to present heterogeneity in fracture density. Finally, our research demonstrates a strong correlation between theoretical prediction results and underground logging, drilling and core data. These findings can help predict the underground fracture distribution and elastic response of carbonate reservoirs controlled by strike-slip faults.

Acoustic wave velocities and effective Debye temperature in potassium alum KAl(SO4)2·12H2O crystal

The acoustic wave velocity along principal propagation directions and polarization orientations was computed for potassium alum KAl(SO4)2·12H2O crystals at 295 K, using elastic constants derived from ultrasonic resonance experiments. The mean elastic Debye temperature was subsequently determined. The temperature dependency of elastic Debye temperature was assessed, based on Brillouin scattering measurements of the longitudinal acoustic (LA) phonon propagating in the [100] direction. Comparison between the elastic Debye temperature extrapolated to T → 0 from the high-temperature phase and the calorimetric Debye temperature determined below the transition temperature (Tc = 59.7 K) revealed an 18 % disparity, primarily attributed to insufficient experimental data of velocity above and below Tc.

Revealing crack initiation and extension of brittle rock via time-lapse acoustic attenuation: Insights from active ultrasonic experiments

Predicting brittle rock failure is essential for rock mechanics research and early disaster alerts in deep rock engineering. Successful prediction relies on identifying crack initiation and extension. However, currently, there is no universally accepted method for accurately identifying and tracking crack evolution to predict brittle failure of the surrounding rock. In this study, the propagation parameters of transmission ultrasonic waves were used to characterize crack behaviors at the laboratory scale. The differential acoustic attenuation term was proposed by modifying the spectral ratio method to evaluate the dissipation capability of the corresponding medium to the transmitted ultrasonic waves. In addition to acoustic attenuation, velocity and amplitude attenuation were introduced to characterize the damage evolution during brittle failure. The indicators were analyzed by conducting a uniaxial compression test on a sandstone sample with a single flaw. During compression, active ultrasonic surveys were conducted to attain the propagation parameters. The two-dimensional digital image correlation method was simultaneously applied to capture the full-field strain on the front surface of the sample. The shear and tensile strain profiles indicated that the shear damage initially accumulated at the tips of the flaw, causing a reduction in the velocity and amplitude of the transmitted ultrasonic waves. The acoustic attenuation indicator in the flaw-tip regions increased before the shear strain began. As the damage developed further, the acoustic attenuation increased overall, with numerous local fluctuations in the flaw-tip regions due to stress rearrangement and damage development, while the velocity and amplitude remained consistently low. In contrast, intact regions that were far away from the tips of the flaw exhibited different characteristics. The velocity and amplitude variations were more staged, while the acoustic attenuation changed gradually. The results indicated that the variations in the propagation parameters exhibited specific patterns before the damage was initiated, offering a potential for predicting crack initiation. The variations in the acoustic attenuation, velocity, and amplitude attenuation allow for tracking the crack propagation.

Ultrasonic immersion testing of residual stress in plates using collinear Lamb wave mixing technique

Nondestructive estimation of residual stresses has been a major challenge in engineering. Herein, the collinear Lamb wave mixing method is proposed for residual stress measurement in metal plates under immersion ultrasonic testing. Numerical simulations have been conducted to investigate the influences of excitation parameters on the performance of the wave mixing method. The results showed that the receiver position and cycle numbers of primary waves affect the amplitude of the method, and optimal excitation parameters recommended. Ultrasonic immersion experiments are conducted on two types of plate-like specimens using the collinear Lamb wave mixing method. Experimental results showed that the proposed method is effective for measuring the residual stress in metal plates. The immersion ultrasonic testing can significantly reduce the influence of inconsistent coupling conditions between the transmitters and the specimen on experimental results, therefore it is more reliable than conventional contact testing.