Ultrasonic Testing Technology Research Articles

A modified synthetic aperture focusing algorithm used for transmission detection based on laser ultrasonics method

Compared with traditional ultrasonic nondestructive testing technology, the laser ultrasonics method (LU) has the advantages of high precision, non-contact, wide-band response, suitable for non-destructive testing (NDT) of materials having complex shapes or working in extreme environments such as the additive manufacturing (AM) process, etc. However, for a purely optical LU system, it is still limited by the poor reflection of rough/absorption surface of the material. In order to increase the signal-to-noise ratio (SNR) of the signal detected on the rough surface of a sample, and to overcome the limitation of the resolution restricted by half wavelength, a modified Synthetic Aperture Focusing Technique (SAFT) that can be used for internal defect detection of the material is proposed. The modified SAFT is based on LU centering transmission detection and it improves the resolution of the detection system by using the characteristics of ultrasonic propagation and its mode conversion. It is firstly studied in theory with a numerical model based on finite element method (FEM), and then it is applied in experiments to reconstruct the defect according to the signals detected by LU method. In our experiment, the artificial defects buried in an AM sample with diameter from 0.2 mm to 0.75 mm are successfully characterized by the SAFT imaging of ultrasonic signals. The results prove that the position of the defect in 3D and its size can be successfully obtained by the proposed SAFT.

Evaluation of corrosion resistance of 316L stainless steel by laser ultrasonic nondestructive testing technology

At present, the corrosion resistance of materials such as 316L stainless steel is mainly tested by electrochemical testing, which is time-consuming, laborious and environmentally unfriendly. In this paper, the laser ultrasonic detection technology, which is a rapid, non-destructive, pollution-free microstructure and corrosion resistance evaluation method is used for the detection of 316L stainless steel, and the ultrasonic signals are filtered by the wavelet threshold denoising method. The results show that the laser ultrasonic attenuation coefficient obtained by the wavelet threshold denoising signal processing method has a good correlation with the corrosion resistance of 316L stainless steel. A laser ultrasonic potential evaluation model was established based on the passivation film rupture potential and ultrasonic attenuation coefficient. The average relative error of the evaluation model for corrosion resistance of 316L stainless steel is less than 5.00%. The relative error of corrosion resistance evaluated by the laser-receiving method is lower than that by the probe-receiving method. It is feasible to nondestructive evaluation of the corrosion resistance of 316L stainless steel by laser ultrasonic technology.

Method of defining rock damage variable on the basis of wave impedance

AbstractA method of determining rock damage variable from wave impedance, which is suitable for the study of dynamics, is presented. The determined variable provides a more reasonable quantitative description of the degree of rock damage. First, the Taylor model of mesoscopic damage mechanics is used to derive the relationship between the velocity of longitudinal waves and the density of rock materials. Based on the measured data of rock samples with different lithology and the same lithology, the relationship between the longitudinal wave velocity and density of rock materials is studied. It is demonstrated that using the wave impedance to define the rock damage variable has advantages over using the P‐wave velocity. Second, the relationship between the wave impedance and degree of damage to the rock material is studied using an electron microscope and ultrasonic testing technology, and the microstructure of rock samples with a wave impedance gradient and time–frequency‐domain characteristics of the ultrasonic signals are compared and analyzed. It is found that it is feasible to determine the damage degree of the rock from the wave impedance. Finally, a method of defining rock damage variable with the wave impedance is further proposed and its rationality verified. The research results show that there is a good positive correlation between the longitudinal wave velocity and density of rock materials, and there is a strong correlation between the degree of rock damage and its wave impedance. The damage variable defined by wave impedance can better reflect the damage state and damage evolution process of rock.

State estimation of lithium-ion batteries based on the initial rise time feature of ultrasonic signals

Lithium-ion batteries have become one of the most critical energy storage systems due to their long cycle life and high energy density. Ultrasonic testing technology has been applied to the battery state estimation for the assurance of durability, safety and performance, however, the accuracy and reliability still need to be improved. In this paper, a new signal feature of the ultrasonic signal is proposed for the state of charge (SOC) estimation of batteries. The signal-shear effect is observed during charge/discharge cycles and is explained by the ultrasonic resonance phenomenon, based on which a SOC estimation method is proposed by using damped sine waves as excitations. This signal feature is characterized by the initial rise time (IRT), which is calculated by an algorithm based on the temporal moment and the adaptive moving root mean square. The optimal frequency and damping ratio parameters of the damped sine waves are found by a parameter-sweep study. Based on the experiment results, the proposed IRT feature is highly correlated to the SOC status with satisfying accuracy, monotonicity and linearity. The IRT feature has the additional advantage to be calculated by only a single data acquisition channel, providing a more convenient mean of battery status estimation.

Laser ultrasonic inspection for mechanical properties of materials at high temperature

The measurement of mechanical properties of high-temperature resistant materials at high temperatures is particularly critical, and laser ultrasonic non-destructive testing technology is a prospective approach for measuring mechanical properties in high-temperature environments. Laser ultrasonic propagation models are constructed by finite element analysis, which reveals the effects of different excitation mechanisms on acoustic velocity measurements. It is found that the shear wave in the main propagation direction is hardly detected, and the distinction between shear waves and surface waves in the time domain signal is difficult. Based on the conclusions, the relationships between surface waves, longitudinal waves, and mechanical properties of materials are established by theoretical derivation. According to the propagation characteristics of surface waves and longitudinal waves, the eccentricity detection scheme of the same side and the concentricity detection scheme of the opposite side are, respectively, designed. The velocities of surface waves and longitudinal waves are measured, considering the thermal expansion coefficient and density changes with temperature. The mechanical properties of materials at different temperatures (25–1000 °C) are successfully calculated, and the experimental results are well in accordance with the reference values. It gives a reliable basis for efficient measurement of mechanical properties of materials at high temperatures.

Comparative study on the similarity between ancient white bricks and the self-developed imitative white bricks

Many architectural heritages in China are built with ancient white bricks (AWB), which behave very differently from traditional blue and red bricks. Indeed, AWB buildings have undergone centuries of historical changes and weathering with time, and require urgent repair. Since replacing ancient bricks with imitative bricks when restoring heritage buildings has become a consensus, it is necessary to develop imitative white bricks (IWB) similar to AWB in many respects to be used for restoring ancient buildings. Therefore, this paper develops a novel IWB and analyses its similarity with the AWB by means of X-ray diffraction, X-ray fluorescence, mercury intrusion test, scanning electron microscopy, and ultrasonic pulse velocity. The results reveal that the self-developed IWB is highly similar to AWB in mineral and chemical composition, micro-morphology, internal appearance, apparent densities, water absorption rate, saturation coefficient, porosity, and these bricks are concentrated in micropores with similar radii. Besides, the durability is somewhat similar in terms of salt crystallization and resistance to freeze-thaw cycles. The IWB and AWB are classified as susceptible to salt crystallization, while good resistance to these white bricks' freeze-thaw cycles. The ultrasonic pulse velocity of the self-developed IWB along the height direction is close to the ultrasonic pulse velocity along other AWB directions. Besides, ultrasonic pulse velocity along the height direction is linearly correlated to the compressive strength of and the IWB and AWB, which has important reference significance for evaluating the mechanical properties of architectural heritages by ultrasonic non-destructive testing technology. These results can provide theoretical and technical support for the in-situ repair of damaged AWB and are significant for restoring and conserving brick masonry architectural heritages.

Evaluating interfacial bonding quality of multilayered structure based on ultrasonic testing technology

An ultrasonic evaluation method of interfacial bonding quality from layered structures is proposed for enhancing the testing accuracy. The ultrasonic reflection and transmission characteristic is theoretically analyzed, which focus on the different quality of the single and double bonding interface with spring-type. The reflection coefficient and transmission coefficient mathematic models, which include multiple parameters, are derived from the transfer matrix. Taking the first, second, and the double bonding interface as the research objects, respectively, two types of resonant frequencies have been presented by numerical solving the model, namely, the first type resonance frequency (RFI) and the second type resonance frequency (RFII). The results show that the interval of the RFⅠ is related to medium thickness of the maximum acoustic impedance. Similarly, the interval of the RFⅡ depends on other layers’ thickness. In addition, the transmission coefficient shows a change in different trends with the bonding interface gradually tending to rigid. When the adhesive layer thickness is sufficiently small compared with the wavelength, the reflection coefficient shows many local minima points at a certain frequencies range, the frequency of local minimum point increases with the increase of the stiffness coefficient. The experimental results are in good agreement with the numerical solution results and finite element analysis results.

Study on intelligent and visualization method of ultrasonic testing of composite materials based on deep learning

Intelligent ultrasonic testing technology of composite materials can greatly reduce the dependence on people and improve the efficiency of ultrasonic testing. The combination of ultrasonic testing and visual positioning technology can realize strong robust visual interpretation of ultrasonic testing results. In this paper, the DiMP tracking model is improved by using the Wasserstein distance, and the intelligent tracking and positioning of ultrasonic probe is realized. At the same time, an ultrasonic signal classification network based on 1DCNN depth neural network is built to realize the intelligent detection of ultrasonic signals, and an effective data connection mode is designed to make the two networks work together, so that the intelligent interpretation and visual display of internal defects of composite materials can be realized. The experimental results show that the interpretation accuracy of the method proposed in this paper reaches 98.74%, and the Kappa coefficient reaches 0.97. The comparison results with other models show that the improved model in this paper is more excellent, and the AUC and Precision values are increased by 6.4% and 8.32% respectively compared with the benchmark.

Ultrasonic Transducer-based Rebar Damage Monitoring Technology

In order to improve the accuracy of mechanical damage monitoring of steel bars, this paper proposes a method of mechanical damage monitoring of steel bars based on ultrasonic nondestructive testing technology. The influence of damage depth on ultrasonic was studied and analyzed, and the corresponding relationship between mechanical damage and ultrasonic characteristics was established. The test results show that the mechanical damage monitoring of steel bars based on ultrasonic nondestructive testing technology has higher accuracy and lower energy consumption and flexible installation.

Energy Transfer Efficiency Based Nonlinear Ultrasonic Testing Technique for Debonding Defects of Aluminum Alloy Foam Sandwich Panels

In order to improve the accuracy of detection results of debonding defects of aluminum alloy thin plate, the nonlinear ultrasonic technology is used to detect the simulated defect samples, aiming at problems such as near surface blind region caused by the interaction of incident wave, reflected wave and even second harmonic wave in a short time due to the small thickness of thin plates. An integral method based on energy transfer efficiency is proposed to calculate the nonlinear ultrasonic coefficient to characterize the debonding defects of thin plates. A series of simulated debonding defects of different sizes were made using aluminum alloy plates with four thicknesses of 1 mm, 2 mm, 3 mm and 10 mm. By comparing the traditional nonlinear coefficient with the integral nonlinear coefficient proposed in this paper, it is verified that both methods can quantitatively characterize the size of debonding defects. The nonlinear ultrasonic testing technology based on energy transfer efficiency has higher testing accuracy for thin plates.

Research Progress in Nonlinear Ultrasonic Testing for Early Damage in Metal Materials

There are some limitations when conventional ultrasonic testing methods are used for testing early damage in metal parts. With the continuous development of acoustics and materials science, nonlinear ultrasonic nondestructive testing technology has been used for testing of early damage in metal materials. In order to better understand the basic theory and research progress of the nonlinear ultrasonic testing technology, the classical nonlinear ultrasonic theoretical models, including the dislocation monopole model, dislocation dipole model, precipitate-dislocation pinning model, and contact nonlinear ultrasonic theory-microcrack model, are analyzed in depth. This paper introduces the application and research progress of nonlinear ultrasonic detection technology, which is derived from different acoustic nonlinear effects, such as higher harmonic, wave mixing and modulation, sub-harmonic, resonance frequency spectrum analysis, and non-linear ultrasonic phased array imaging. The key technologies and problems are summarized to provide a reference for the further development and promotion of nonlinear ultrasonic non-destructive testing technology.

Application of Ultrasonic Phased Array Technology in the Inspection of Small Diameter Pipe Welds on the Heating Surface of Circulating Fluidized Bed Boilers

As a new type of testing technology, ultrasonic phased array testing technology can achieve the efficiency and quality that other testing methods cannot achieve. This paper gives a comprehensive overview of the application of ultrasonic phased array technology in the inspection of small diameter pipe welds of circulating fluidized bed boiler, analyzes the difficulties in the inspection process, and summarizes the possible non-relevant indications generated by the ultrasonic phased array. This paper can provide a reference for the application of ultrasonic phased array testing technology in the detection of small diameter pipe welds of circulating fluidized bed boilers and has practical significance for the relevant research of ultrasonic phased array testing technology.

On propagation characteristics of ultrasonic guided waves in helical strands

Steel strands have been widely used in industrial fields as a reliable load-bearing component. Under the influence of environmental erosion and fatigue stress, different types of damage, such as corrosion and fracture, will occur in the in-service steel strands, which will cause unpredictable loss of personnel and property. Ultrasonic nondestructive testing technology has become an ideal testing method for long-distance metal structures in recent years due to the advantages of long detection distance and high efficiency. The detection effect of ultrasonic nondestructive testing technology largely depends on the propagation characteristics of the selected guided wave modes. However, due to the influence of the helical structure of the steel strands and the contact between the wires, the propagation characteristics of the guided waves in the steel strands are very complicated. In this paper, a method for analyzing the dispersion characteristics of steel strands based on the Floquet boundary conditions (Floquet BCs) is proposed. The essence of this method is the mutual transformation principle of wave solution and vibration solution. To adapt to the helical structure of steel strands, this paper proposes a helical coordinate system and twisted coordinate system and deduces the corresponding wavenumber conversion formula. The results of Floquet BCs are consistent with the semi-analytical finite element method and sweep frequency finite element modeling method, which proves the correctness of the Floquet BC method from both theoretical and experimental perspectives. This paper provides a new idea for analyzing the dispersion characteristics of complex waveguides such as steel strands.

State estimation of a lithium-ion battery based on multi-feature indicators of ultrasonic guided waves

Ultrasonic non-destructive testing technology has been applied to battery state estimation applications to ensure the safety of the energy storage system. However, the accuracy and robustness of battery state estimation should be improved. In this paper, the state estimation of a lithium-ion battery based on multi-feature indicators of ultrasonic guided waves is studied. Piezoelectric ceramic ultrasonic probes with a fixed angle are used as the transducers. Eleven feature indicators of ultrasonic signals are analyzed. The appropriate feature indicators for battery state estimation are determined based on sensitivity analysis and correlation analysis. Considering the frequency response characteristics of the probe and the battery, the multi-frequency response characteristics of the battery are analyzed. Finally, seven feature indicators with multi-frequency excitation are selected. Subsequently, an adaptive machine learning model is designed to estimate the battery state. Based on the experimental results, the root mean square error (RMSE) of the battery state of charge (SOC) estimation result is less than 2.36 %. The applicability of the proposed method is verified by battery fully charged and non-fully charged experiments. Meanwhile, the method can quickly diagnose the side reaction process under abuse conditions such as overcharge and overdischarge, which provides a new method for non-destructive battery state evaluation.

Effects of microwave radiation on dynamic compressive properties of basalt

The dynamic mechanical properties of basalt affected by microwave were investigated by performing dynamic compressive tests using the SHPB system. Meanwhile, the thermal damage of the treated basalt was characterized by ultrasonic non-destructive testing and nuclear magnetic resonance technology. The results show that with the increase of microwave power and exposure time, the P-wave velocity, dynamic compressive strength and elastic modulus decrease continuously, and the dynamic failure mode tends to be a more complex fracturing. The increase in microwave power and exposure time can enhance the temperature difference and transfer coefficient among minerals, hence intensifying the rock damage induced by thermal shock.

Application of Ultrasonic Nondestructive Testing Technology of Hydraulic Structure Concrete

Application of Ultrasonic Nondestructive Testing Technology of Hydraulic Structure Concrete

A Fast Signal-Processing Method for Electromagnetic Ultrasonic Thickness Measurement of Pipelines Based on UKF and SMO

Electromagnetic ultrasonic testing technology has advantages in measuring the thickness of pipelines in service. However, the ultrasonic signal is susceptible to corrosions on the internal and external surfaces of the pipeline. Since the electromagnetic ultrasonic signal is nonlinear, and a dynamic model is difficult to establish accurately, in this paper, a new unscented Kalman filter (UKF) method based on a sliding mode observer (SMO) is proposed. The experiments, conducted on five different testing samples, validate that the proposed method can effectively process the signals drowned in noise and accurately measure the wall thickness. Compared with FFT and UKF, the signal-to-noise ratio of the signals processed by SMO–UKF shows a maximum increase of 155% and 171%. Meanwhile, a random assignment method is proposed for the self-regulation of hyper parameters in the process of Kalman filtering. Experimental results show that the automatic adjustment of hyper parameters can be accomplished in finite cycle numbers and greatly shortens the overall filtering time.

Experimental research on ultrasonic A-scan testing technology of composite solid propellant

To explore the application and development of ultrasonic non-destructive testing technology in composite solid propellant materials, the theory is combined with the principle and method of ultrasonic non-destructive testing technology and the material characteristics of composite solid propellant; Based on ultrasonic A-scan, the experimental testing of propellant grain with multiphase structure, complex properties and high attenuation was carried out using pulse reflection method and penetration method. For the testing system with probe emission frequency of 1 MHz and gain adjustable range of 60 dB, the thickness of propellant grain is recommended to be 10 ~ 50 mm for the pulse reflection method to effectively observe the first bottom echo and the second bottom echo, and the thickness of propellant grain is recommended to be less than or equal to 100 mm for the penetration method to effectively observe the transmission waveform. The coupling modes of ultrasonic testing technology are further analyzed, and the effect test is carried out. In addition, based on the pulse reflection method of direct contact coupling, the sound velocity of propellant grain is measured with probes with different frequencies. The results show that the higher the probe frequency is, the smaller the sound velocity of propellant grain is.

State Characterization of Lithium-Ion Battery Based on Ultrasonic Guided Wave Scanning

Accurate state characterization of batteries is conducive to ensuring the safety, reliability, and efficiency of their work. In recent years, ultrasonic non-destructive testing technology has been gradually applied to battery state estimation. In this paper, research on the state characterization of lithium-ion batteries based on ultrasonic guided wave (UGW) scanning is carried out. The laser Doppler vibrometer (LDV) and the X-Y stage are used to obtain the surface scanning UGW signal and the line scanning UGW signal of lithium-ion batteries under different states of charge and different aging degrees. The propagation law of UGWs in the battery is analyzed by surface scanning signals, then the energy spectrum of the signals is calculated, showing that the aging of the battery attenuates the transmission energy of UGWs. The “point” parameters are extracted from the scanning point signals. On this basis, the “line” parameters composed of line scanning multi-point signals are extracted. By analyzing the changing law of parameters during the charge–discharge process of batteries, several characteristic parameters that can be used to characterize the battery state of charge and state of health are obtained. The method has good consistency in the state characterization of the three batteries and provides a new approach for non-destructive testing and evaluation of battery states.

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.