The rapid progress in the construction of heavy-haul and high-speed railways has led to a surge in rail defects and unforeseen failures.Addressing this issue necessitates the implementation of more sophisticated rail ...The rapid progress in the construction of heavy-haul and high-speed railways has led to a surge in rail defects and unforeseen failures.Addressing this issue necessitates the implementation of more sophisticated rail inspection methods,specifically involving real-time,precise detection,and assessment of rail defects.Current applications fail to address the evolving requirements,prompting the need for advancements.This paper provides a summary of various types of rail defects and outlines both traditional and innovative non-destructive inspection techniques,examining their fundamental features,benefits,drawbacks,and practical suitability for railway track inspection.It also explores potential enhancements to equipment and software.The comprehensive review draws upon pertinent international research and review papers.Furthermore,the paper introduces a fusion of inspection methods aimed at enhancing the overall reliability of defect detection.展开更多
T he residual stray magnetic fields present in ferromagnetic casting slabs were investigated in this work,which result from the magnetic fields generated during the steel casting process.Existing optical detection met...T he residual stray magnetic fields present in ferromagnetic casting slabs were investigated in this work,which result from the magnetic fields generated during the steel casting process.Existing optical detection methods face challenges owing to surface oxide scales,and conventional high-precision magnetic sensors are ineffective at high temperatures.To overcome these limitations,a small coil sensor was employed to measure the residual magnetism strength in oscillation traces,using metal magnetic memory and electromagnetic induction methods,which can carry out detection without an external excitation source.Using this technology,the proposed scheme successfully detects defects at high tempe-ratures(up to 670℃)without a cooling device.The key findings include the ability to detect both surface and near-surface defects,such as cracks and oscillation marks,with an enhanced signal-to-noise ratio(SNR)of 7.2 dB after signal processing.The method’s practicality was validated in a steel mill environment,where testing on casting slabs effectively detected defects,providing a foundation for improving industrial quality control.The proposed detection scheme offers a significant advancement in nondestructive testing(NDT)for high-temperature applications,contributing to more efficient and accurate monitoring of ferromagnetic material integrity.展开更多
The fundamental shear horizontal（SH0） wave has several unique features that are attractive for long-range nondestructive testing（NDT）. By a careful design of the geometric configuration, electromagnetic acoustic t...The fundamental shear horizontal（SH0） wave has several unique features that are attractive for long-range nondestructive testing（NDT）. By a careful design of the geometric configuration, electromagnetic acoustic transducers（EMATs） have the capability to generate a wide range of guided wave modes, such as Lamb waves and shear-horizontal（SH） waves in plates. However, the performance of EMATs is influenced by their parameters. To evaluate the performance of periodic permanent magnet（PPM） EMATs, a distributed-line-source model is developed to calculate the angular acoustic field cross-section in the far-field. Numerical analysis is conducted to investigate the performance of such EMATs with different geometric parameters, such as period and number of magnet arrays, and inner and outer coil widths. Such parameters have a great influence on the directivity of the generated SH0 waves that arises mainly in the amplitude and width of both main and side lobes. According to the numerical analysis, these parameters are optimized to obtain better directivity. Optimized PPM EMATs are designed and used for NDT of strip plates. Experimental results show that the lateral boundary of the strip plate has no perceivable influence on SHO-wave propagation, thus validating their used in NDT. The proposed model predicts the radiation pattern ofPPM EMATs, and can be used for their parameter optimization.展开更多
To study the distribution law and random characteristics of casting defects in steel castings,24 civil engineering structural cast steel joints were divided into two groups:simple cast steel joints and complex cast st...To study the distribution law and random characteristics of casting defects in steel castings,24 civil engineering structural cast steel joints were divided into two groups:simple cast steel joints and complex cast steel joints.Three kinds of nondestructive testing(NDT)methods,namely,visual,magnetic particle,and ultrasonic inspections,were used to detect the macroscopic defects in joints.The NDT results were then statistically analyzed.The results show that the unfused core support is a common defect of complex cast steel joints,and the defect can be seen visually,so excavation and repair welding should be carried out before castings leave factories.Casting cracks are extremely likely to occur in the intersection area of tubes,which is called the ultrasonic inspection blind zone.The occurrence probability of gas pores on simple cast steel joints is the largest,and the occurrence probability of core support incomplete fusions on complex cast steel joints is the largest.However,when cast steel joints are counted as a whole sample,the occurrence probability of gas pores is larger than that of core support incomplete fusions.Therefore,it is the most common defect in cast steel joints.展开更多
To address the difficulty in testing and calibrating the stress gradient in the depth direction of mechanical components, a new technology of nondestructive testing and characterization of the residual stress gradient...To address the difficulty in testing and calibrating the stress gradient in the depth direction of mechanical components, a new technology of nondestructive testing and characterization of the residual stress gradient field by ultrasonic method is proposed based on acoustoelasticity theory. By carrying out theoretical analysis, the sensitivity coefficients of different types of ultrasonic are obtained by taking the low carbon steel（12%C） as a research object. By fixing the interval distance between sending and receiving transducers, the mathematical expressions of the change of stress and the variation of time are established. To design one sending-one receiving and oblique incidence ultrasonic detection probes, according to Snell law, the critically refracted longitudinal wave（LCR wave） is excited at a certain depth of the fixed distance of the tested components. Then, the relationship between the depth of LCR wave detection and the center frequency of the probe in Q235 steel is obtained through experimental study. To detect the stress gradient in the depth direction, a stress gradient LCR wave detection model is established, through which the stress gradient formula is derived by the relationship between center frequency and detecting depth. A C-shaped stress specimen of Q235 steel is designed to conduct stress loading tests, and the stress is measured with the five group probes at different center frequencies. The accuracy of ultrasonic testing is verified by X-ray stress analyzer. The stress value of each specific depth is calculated using the stress gradient formula. Accordingly, the ultrasonic characterization of residual stress field is realized. Characterization results show that the stress gradient distribution is consistent with the simulation in ANSYS. The new technology can be widely applied in the detection of the residual stress gradient field caused by mechanical processing, such as welding and shot peening.展开更多
Photoacoustic(PA)imaging has been widely used in biomedical research and preclinical studies during the past two decades.It has also been explored for nondestructive testing and evaluation(NDT/E)and for industrial app...Photoacoustic(PA)imaging has been widely used in biomedical research and preclinical studies during the past two decades.It has also been explored for nondestructive testing and evaluation(NDT/E)and for industrial applications.This paper describes the basic principles of PA technology for NDT/E and its applications in recent years.PA technology for NDT/E includes the use of a modulated continuous-wave laser and a pulsed laser for PA wave excitation,PA-generated ultrasonic waves,and all-optical PA wave excitation and detection.PA technology for NDT/E has demonstrated broad applications,including the imaging of railway cracks and defects,the imaging of Li metal batteries,the measurements of the porosity and Young’s modulus,the detection of defects and damage in silicon wafers,and a visualization of underdrawings in paintings.展开更多
For our research, a new hybrid experimental-computational method is presented. We applied a least squares fitting method （LSFM） to reconstruct the wood moisture content （WMC） from the data measured with a planar c...For our research, a new hybrid experimental-computational method is presented. We applied a least squares fitting method （LSFM） to reconstruct the wood moisture content （WMC） from the data measured with a planar capacitance sensor. A boundary element method （BEM） was used to compute the relationship between capacitance and the dielectric constant. A functional relationship between MC and the dielectric constant was identified by LSFM. The agreement of this final computation result with the experimental data indicates that this method can be used to estimate the WMC quickly and effectively with engineering analysis. Compared with popular statistical methods, a large number of experiments are avoided, some costs of testing are reduced and the efficiency of testing is enhanced.展开更多
Based on quantitative microscopic examinations of welds and welding rate for different steels(40Cr and T10A) joint,which possess the ultra-fine microstructure after high frequency hardening(HFH) and salt-bath cyclic q...Based on quantitative microscopic examinations of welds and welding rate for different steels(40Cr and T10A) joint,which possess the ultra-fine microstructure after high frequency hardening(HFH) and salt-bath cyclic quenching(SCQ),the suitable defect grey scale threshold value was determined,and the welding rate of superplastic solid-state welding of different steels(40Cr and T10 A steel) was systematically inspected and analyzed by means of self-made ultrasonic imaging inspection system.The experimental results showed that the superplastic solid-state weld of different steels can be inspected more accurately,reliably and quickly by this system,and the results were in good accordance with that of metallographic observation.The welding rate of superplastic welding is in linear relation with tensile strength of joint.展开更多
CFRP （carbon fiber reinforced plastic） is used extensively in aircraft and spacecraft structures, because of its excellent mechanical properties. Ultrasonic testing, which is used as a non-destructive testing techni...CFRP （carbon fiber reinforced plastic） is used extensively in aircraft and spacecraft structures, because of its excellent mechanical properties. Ultrasonic testing, which is used as a non-destructive testing technique for CFRP, requires a contact medium. In contrast, eddy current testing does not require a contact medium, and when used for CFRP testing it has advantages not available with other techniques. CFRP is a laminate, with each layer being anisotropically conductive, and the distribution of the induced eddy current is yet to be determined. Here, to determine the eddy current distribution in the detection of flaws in cross-ply CFRP （0°/90°） by using a cross-point probe, we performed an FEM （finite element method） analysis of electromagnetic fields. We investigated the nature of the flaw signals and the differences in eddy current distributions between materials with and without flaws.展开更多
Due to the fact that rolling contact fatigue is not easily detected, and residual life is not easily evaluated in the early stage of bearing life, a nondestructive testing method based on initial permeability is propo...Due to the fact that rolling contact fatigue is not easily detected, and residual life is not easily evaluated in the early stage of bearing life, a nondestructive testing method based on initial permeability is proposed. By analyzing the crack propagation mechanism, a fatigue state detection system based on differential signals is designed. A simulation model of the detection of the inner ring of the pulse signal is established by using the electromagnetic field simulation software. The effects of the height of the coil, the inner and outer diameter, the number of coil turns, the diameter and the height of the ferrite core of the probe on the differential value of the detection signal are simulated. The parameter combination of the maximum difference value of the signal is used as the structural size of the sensor, and the detection sensor is designed and fabricated. Moreover, the bearing fatigue test system is designed, and the bearing is tested. The results show that the system has good detection ability for rolling contact fatigue and verifies the mechanism and trend of crack propagation in the inner ring of the bearing.展开更多
Quality inspection is an important means to ensure that the construction quality of roads and bridges meets the standard requirements. In recent years, with the progress of science and technology, the road and bridge ...Quality inspection is an important means to ensure that the construction quality of roads and bridges meets the standard requirements. In recent years, with the progress of science and technology, the road and bridge quality detection technology began to develop in the direction of diversification and informatization, which greatly improved the accuracy of the detection results and effectively improved the damage caused to the road and bridge structure by the traditional detection technology. On the basis of not damaging the original structure, the efficiency and quality of quality detection are improved. Based on this, this paper will analyze the application of nondestructive testing technology in road and bridge testing.展开更多
In recent years, China's economic development is accelerating, the comprehensive national strength continues to improve, promote the development of China's pressure special equipment, pressure special equipmen...In recent years, China's economic development is accelerating, the comprehensive national strength continues to improve, promote the development of China's pressure special equipment, pressure special equipment is mainly used in petrochemical and other industrial production fields. Once the pressure special equipment is damaged, it will cause non-negligible harm. About the pressure equipment, this paper first introduces some testing technologies in the field of nondestructive testing technology, and then discusses the application of nondestructive testing technology in the testing process of special pressure equipment. The selection of reasonable testing time and the comprehensive application of nondestructive testing technology are introduced in detail in order to improve the testing accuracy and contribute to the development of nondestructive testing field.展开更多
For the chemical industry, the production of medium pressure vessels affects the development of the industry. Because the pressure vessel is prone to accidents if the internal pressure is too high in the production pr...For the chemical industry, the production of medium pressure vessels affects the development of the industry. Because the pressure vessel is prone to accidents if the internal pressure is too high in the production process, for a chemical enterprise, the production accident will bring the estimated loss of remedial classes. There are many reasons for accidents, most of which occur on pressure vessels. For example, the wear of pressure vessel components and improper operation of personnel will cause pressure leakage or explosion, resulting in safety accidents. Many industries need to know whether the performance of pressure vessels can meet the production standards. In this paper, various quality problems of pressure vessels on the market are analyzed and explored, hoping that some quality problems can be avoided in the production of pressure vessels, so as to reduce the occurrence of accidents and the loss of enterprises from the root. The main method discussed in this paper is to reduce the quality problems of pressure vessels with the help of nondestructive testing technology. Next, this paper introduces the distance and specific application of nondestructive testing technology in detail.展开更多
Lanzhou Institute of Physics, a subsidiary of CAST, conducted ground testing on its newly developed eddy current nondestructive testing equipment, demonstrating an important breakthrough had been made with the nondest...Lanzhou Institute of Physics, a subsidiary of CAST, conducted ground testing on its newly developed eddy current nondestructive testing equipment, demonstrating an important breakthrough had been made with the nondestructive testing of orbital spacecraft. The equipment works steadily and has met the design requirements for space applications. It was also announced by the Institute that the equipment would be used during the next lunar exploration mission to detect the status of展开更多
Energy-variable gamma-rays are produced in Laser Compton Slant-scattering mode at the Shanghai Laser Electron Gamma Source(SLEGS),a beamline of the Shanghai Synchrotron Radiation Facility(also called Shanghai Light So...Energy-variable gamma-rays are produced in Laser Compton Slant-scattering mode at the Shanghai Laser Electron Gamma Source(SLEGS),a beamline of the Shanghai Synchrotron Radiation Facility(also called Shanghai Light Source).Based on the SLEGS energy-variable gamma-ray beam,a positron generation system composed of a gamma-ray-driven section,positron-generated target,magnet separation section and positron experimental section was designed for SLEGS.Geant4 simulation results show that the energy tunable positron beam in the energy range of 1–12.9 MeV with a flux of 3.7×10^(4)–6.9×10^(5)e^(+)∕s can be produced in this positron generation system.The positron beam generation and separation provide favorable experimental conditions for conducting nondestructive positron testing on SLEGS in the future.The positron generation system is currently under construction and will be completed in 2025.展开更多
To scientifically evaluate the restoration performance of ancient city walls,Terahertz time-domain spectroscopy(THz-TDS)and infrared thermal imaging technology were applied to assess the Desheng Fortress(Ming Dynasty)...To scientifically evaluate the restoration performance of ancient city walls,Terahertz time-domain spectroscopy(THz-TDS)and infrared thermal imaging technology were applied to assess the Desheng Fortress(Ming Dynasty).Three representative sections were examined:adobe brick masonry repaired(Area 1),well-preserved original(Area 2),and layer-by-layer ramming repaired(Area 3).THz spectral data revealed significant differences between Area 1(time delay:3.72 ps;refractive index:2.224)and Area 2(time delay:3.02 ps;refractive index:2.107),while Area 3(time delay:3.12 ps;refractive index:2.098)demonstrated nearly identical THz spectral data to Area 2.Infrared thermal imaging also showed that the Area 3 restored by layer-by-layer ramming exhibited greater uniformity with fewer instances of cracks,capillary phenomena,or biological diseases.The proposed point-surface integrated evaluation methodology synergistically combines infrared thermography mapping of heritage surfaces with THz spectral datasets acquired through in-situ micro-sampling,enabling quantitative restoration assessment and providing a novel approach for scientifically validating traditional conservation techniques.展开更多
Detecting internal defects,particularly voids behind linings,is critical for ensuring the structural integrity of aging high-speed rail(HSR)tunnel networks.While ground-penetrating radar(GPR)is widely employed,systema...Detecting internal defects,particularly voids behind linings,is critical for ensuring the structural integrity of aging high-speed rail(HSR)tunnel networks.While ground-penetrating radar(GPR)is widely employed,systematic quantification of performance boundaries for air-coupled(A-CGPR)and ground-coupled(G-CGPR)systems within the complex electromagnetic environment of multilayer reinforced HSR tunnels remains limited.This study establishes physics-based quantitative performance limits for A-CGPR and G-CGPR through rigorously validated GPRMax finite-difference time-domain(FDTD)simulations and comprehensive field validation over a 300 m operational HSR tunnel section.Key performance metrics were quantified as functions of:(a)detection distance(A-CGPR:2.0–4.5 m;G-CGPR:≤0.1 m),(b)antenna frequency(A-CGPR:300 MHz;G-CGPR:400/900 MHz),(c)reinforcement configuration(unreinforced,single-layer,multilayer rebar),and(d)void geometry(axial length:0.1–1.0 m;radial depth:0.1–0.5 m).Key findings demonstrate:a.A-CGPR(300 MHz):Reliably detects axial voids≥0.3 m at distances≤3 m in minimally reinforced(single-layer rebar)linings(field R2=0.89).Performance degrades significantly at distances>3 m(>60%signal attenuation at 4.5 m)or under multilayer rebar interference,causing 25%–40%accuracy loss for voids<0.3 m.Optimal distance:2.0–2.5 m.b.G-CGPR(900 MHz):Achieves<5%size measurement error for axial voids≥0.1 m and radial voids≥0.2 m in unreinforced linings.Resolution degrades under multilayer reinforcement due to severe signal attenuation,increasing axial void detection error to 10%–20%for voids≥0.3 m and constraining radial size measurement.c.Synergistic Framework:A hybrid inspection protocol is proposed,integrating A-CGPR(20 km/h)for rapid large-area screening and targeted G-CGPR(3 km/h)for high-resolution verification of identified anomalies.This framework enhances NDT efficiency while reducing estimated lifecycle inspection costs by 34%compared to G-CGPR alone.This research provides the first physics-derived quantitative detection thresholds for A-CGPR and G-CGPR in multi-rebar HSR tunnels,validated through field-correlated simulations.Future work will focus on multi-frequency antenna arrays and deep learning algorithms to mitigate reinforcement interference.The established performance boundaries and hybrid framework offer critical guidance for optimizing tunnel lining inspection strategies in extensive HSR networks.展开更多
Robots are used to conduct non-destructive defect detection on wind turbine blades(WTBs)and to monitor their integrity over time.However,current inspection robots are often bulky and heavy,and struggle to detect defec...Robots are used to conduct non-destructive defect detection on wind turbine blades(WTBs)and to monitor their integrity over time.However,current inspection robots are often bulky and heavy,and struggle to detect defects in the blade's main beam,thus presenting difficulties in portability and effectiveness.To address these issues,we designed a wheel-wing composite robot equipped with a curved surface-adaptive phased array ultrasonic detection device for the detection of defects in the WTB's main beam.We determined the pose equation under different section characteristics and identified the robot's stable range of motion,thus developing a model of its kinematics.A detection device adapted for variable curvature surfaces was designed to ensure tight coupling between the robot's probe and the blade.Additionally,element differential and least-square ellipse-fitting methods were employed to analyze blades with irregular sections.The simulation results demonstrated that the prototype can stably traverse an area with a vertical angle of±14.06°at a speed of 0.25 m/s,fully covering the main beam area of the blade during walking operations.Moreover,the robot can scan the main beam area at a speed of 0.10 m/s,enabling the accurate detection of defects.展开更多
In high-risk industrial environments like nuclear power plants,precise defect identification and localization are essential for maintaining production stability and safety.However,the complexity of such a harsh enviro...In high-risk industrial environments like nuclear power plants,precise defect identification and localization are essential for maintaining production stability and safety.However,the complexity of such a harsh environment leads to significant variations in the shape and size of the defects.To address this challenge,we propose the multivariate time series segmentation network(MSSN),which adopts a multiscale convolutional network with multi-stage and depth-separable convolutions for efficient feature extraction through variable-length templates.To tackle the classification difficulty caused by structural signal variance,MSSN employs logarithmic normalization to adjust instance distributions.Furthermore,it integrates classification with smoothing loss functions to accurately identify defect segments amid similar structural and defect signal subsequences.Our algorithm evaluated on both the Mackey-Glass dataset and industrial dataset achieves over 95%localization and demonstrates the capture capability on the synthetic dataset.In a nuclear plant's heat transfer tube dataset,it captures 90%of defect instances with75%middle localization F1 score.展开更多
Residual stress is one of the main factors affecting the mechanical properties of materials, such as their strength, plasticity and surface integrity. For instance, tensile stress conditions can adversely affect mater...Residual stress is one of the main factors affecting the mechanical properties of materials, such as their strength, plasticity and surface integrity. For instance, tensile stress conditions can adversely affect material performance or component life, while compressive stress conditions can improve material fatigue strength. During the processing of integrated aviation structures, machining deformation caused by residual stress has become one of the most prominent manufacturing problems. Therefore, it is very important to measure and evaluate the stress for real applications.This paper reviews the research of residual stress measurement methods over the past five years by classifying them according to the measurement methods appearing in each stage. The existing problems and difficulties of each measurement technology are summarized, and future trends are forecasted. This paper provides a reference for further in-depth study of residual stress measurement technologies.展开更多
文摘The rapid progress in the construction of heavy-haul and high-speed railways has led to a surge in rail defects and unforeseen failures.Addressing this issue necessitates the implementation of more sophisticated rail inspection methods,specifically involving real-time,precise detection,and assessment of rail defects.Current applications fail to address the evolving requirements,prompting the need for advancements.This paper provides a summary of various types of rail defects and outlines both traditional and innovative non-destructive inspection techniques,examining their fundamental features,benefits,drawbacks,and practical suitability for railway track inspection.It also explores potential enhancements to equipment and software.The comprehensive review draws upon pertinent international research and review papers.Furthermore,the paper introduces a fusion of inspection methods aimed at enhancing the overall reliability of defect detection.
文摘T he residual stray magnetic fields present in ferromagnetic casting slabs were investigated in this work,which result from the magnetic fields generated during the steel casting process.Existing optical detection methods face challenges owing to surface oxide scales,and conventional high-precision magnetic sensors are ineffective at high temperatures.To overcome these limitations,a small coil sensor was employed to measure the residual magnetism strength in oscillation traces,using metal magnetic memory and electromagnetic induction methods,which can carry out detection without an external excitation source.Using this technology,the proposed scheme successfully detects defects at high tempe-ratures(up to 670℃)without a cooling device.The key findings include the ability to detect both surface and near-surface defects,such as cracks and oscillation marks,with an enhanced signal-to-noise ratio(SNR)of 7.2 dB after signal processing.The method’s practicality was validated in a steel mill environment,where testing on casting slabs effectively detected defects,providing a foundation for improving industrial quality control.The proposed detection scheme offers a significant advancement in nondestructive testing(NDT)for high-temperature applications,contributing to more efficient and accurate monitoring of ferromagnetic material integrity.
基金supported by National Natural Science Foundation of China(Grant Nos.51075012,10772008)Beijing Municipal Natural Science Foundation of China(Grant No.1122005)
文摘The fundamental shear horizontal（SH0） wave has several unique features that are attractive for long-range nondestructive testing（NDT）. By a careful design of the geometric configuration, electromagnetic acoustic transducers（EMATs） have the capability to generate a wide range of guided wave modes, such as Lamb waves and shear-horizontal（SH） waves in plates. However, the performance of EMATs is influenced by their parameters. To evaluate the performance of periodic permanent magnet（PPM） EMATs, a distributed-line-source model is developed to calculate the angular acoustic field cross-section in the far-field. Numerical analysis is conducted to investigate the performance of such EMATs with different geometric parameters, such as period and number of magnet arrays, and inner and outer coil widths. Such parameters have a great influence on the directivity of the generated SH0 waves that arises mainly in the amplitude and width of both main and side lobes. According to the numerical analysis, these parameters are optimized to obtain better directivity. Optimized PPM EMATs are designed and used for NDT of strip plates. Experimental results show that the lateral boundary of the strip plate has no perceivable influence on SHO-wave propagation, thus validating their used in NDT. The proposed model predicts the radiation pattern ofPPM EMATs, and can be used for their parameter optimization.
基金The National Key R&D Program of China(No.2017YFC0805100)the National Natural Science Foundation of China(No.51578137)+1 种基金the Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutionsthe Open Research Fund Program of Jiangsu Key Laboratory of Engineering Mechanics。
文摘To study the distribution law and random characteristics of casting defects in steel castings,24 civil engineering structural cast steel joints were divided into two groups:simple cast steel joints and complex cast steel joints.Three kinds of nondestructive testing(NDT)methods,namely,visual,magnetic particle,and ultrasonic inspections,were used to detect the macroscopic defects in joints.The NDT results were then statistically analyzed.The results show that the unfused core support is a common defect of complex cast steel joints,and the defect can be seen visually,so excavation and repair welding should be carried out before castings leave factories.Casting cracks are extremely likely to occur in the intersection area of tubes,which is called the ultrasonic inspection blind zone.The occurrence probability of gas pores on simple cast steel joints is the largest,and the occurrence probability of core support incomplete fusions on complex cast steel joints is the largest.However,when cast steel joints are counted as a whole sample,the occurrence probability of gas pores is larger than that of core support incomplete fusions.Therefore,it is the most common defect in cast steel joints.
基金Supported by National Natural Science Foundation of China(Grant No.51275042)
文摘To address the difficulty in testing and calibrating the stress gradient in the depth direction of mechanical components, a new technology of nondestructive testing and characterization of the residual stress gradient field by ultrasonic method is proposed based on acoustoelasticity theory. By carrying out theoretical analysis, the sensitivity coefficients of different types of ultrasonic are obtained by taking the low carbon steel（12%C） as a research object. By fixing the interval distance between sending and receiving transducers, the mathematical expressions of the change of stress and the variation of time are established. To design one sending-one receiving and oblique incidence ultrasonic detection probes, according to Snell law, the critically refracted longitudinal wave（LCR wave） is excited at a certain depth of the fixed distance of the tested components. Then, the relationship between the depth of LCR wave detection and the center frequency of the probe in Q235 steel is obtained through experimental study. To detect the stress gradient in the depth direction, a stress gradient LCR wave detection model is established, through which the stress gradient formula is derived by the relationship between center frequency and detecting depth. A C-shaped stress specimen of Q235 steel is designed to conduct stress loading tests, and the stress is measured with the five group probes at different center frequencies. The accuracy of ultrasonic testing is verified by X-ray stress analyzer. The stress value of each specific depth is calculated using the stress gradient formula. Accordingly, the ultrasonic characterization of residual stress field is realized. Characterization results show that the stress gradient distribution is consistent with the simulation in ANSYS. The new technology can be widely applied in the detection of the residual stress gradient field caused by mechanical processing, such as welding and shot peening.
基金S.-L.Chen acknowledges funding from the National Natural Science Foundation of China,No.61775134C.Tian acknowledges funding from the National Natural Science Foundation of China,No.61705216the Anhui Science and Technology Department,No.18030801138.
文摘Photoacoustic(PA)imaging has been widely used in biomedical research and preclinical studies during the past two decades.It has also been explored for nondestructive testing and evaluation(NDT/E)and for industrial applications.This paper describes the basic principles of PA technology for NDT/E and its applications in recent years.PA technology for NDT/E includes the use of a modulated continuous-wave laser and a pulsed laser for PA wave excitation,PA-generated ultrasonic waves,and all-optical PA wave excitation and detection.PA technology for NDT/E has demonstrated broad applications,including the imaging of railway cracks and defects,the imaging of Li metal batteries,the measurements of the porosity and Young’s modulus,the detection of defects and damage in silicon wafers,and a visualization of underdrawings in paintings.
基金supported by the Central University Basic Research Professional Expenses Special Foundation of Harbin Engineering University (Grant No. HEUCFL10101109)
文摘For our research, a new hybrid experimental-computational method is presented. We applied a least squares fitting method （LSFM） to reconstruct the wood moisture content （WMC） from the data measured with a planar capacitance sensor. A boundary element method （BEM） was used to compute the relationship between capacitance and the dielectric constant. A functional relationship between MC and the dielectric constant was identified by LSFM. The agreement of this final computation result with the experimental data indicates that this method can be used to estimate the WMC quickly and effectively with engineering analysis. Compared with popular statistical methods, a large number of experiments are avoided, some costs of testing are reduced and the efficiency of testing is enhanced.
基金Item Sponsored by Provincial Natural Science Foundation of Henan(984040900)State Key Laboratory of Laser Technology([2001]0110)
文摘Based on quantitative microscopic examinations of welds and welding rate for different steels(40Cr and T10A) joint,which possess the ultra-fine microstructure after high frequency hardening(HFH) and salt-bath cyclic quenching(SCQ),the suitable defect grey scale threshold value was determined,and the welding rate of superplastic solid-state welding of different steels(40Cr and T10 A steel) was systematically inspected and analyzed by means of self-made ultrasonic imaging inspection system.The experimental results showed that the superplastic solid-state weld of different steels can be inspected more accurately,reliably and quickly by this system,and the results were in good accordance with that of metallographic observation.The welding rate of superplastic welding is in linear relation with tensile strength of joint.
文摘CFRP （carbon fiber reinforced plastic） is used extensively in aircraft and spacecraft structures, because of its excellent mechanical properties. Ultrasonic testing, which is used as a non-destructive testing technique for CFRP, requires a contact medium. In contrast, eddy current testing does not require a contact medium, and when used for CFRP testing it has advantages not available with other techniques. CFRP is a laminate, with each layer being anisotropically conductive, and the distribution of the induced eddy current is yet to be determined. Here, to determine the eddy current distribution in the detection of flaws in cross-ply CFRP （0°/90°） by using a cross-point probe, we performed an FEM （finite element method） analysis of electromagnetic fields. We investigated the nature of the flaw signals and the differences in eddy current distributions between materials with and without flaws.
基金The Science and Technology Innovation Committee(STIC)of Shenzhen(No.JCYJ20180306174455080)
文摘Due to the fact that rolling contact fatigue is not easily detected, and residual life is not easily evaluated in the early stage of bearing life, a nondestructive testing method based on initial permeability is proposed. By analyzing the crack propagation mechanism, a fatigue state detection system based on differential signals is designed. A simulation model of the detection of the inner ring of the pulse signal is established by using the electromagnetic field simulation software. The effects of the height of the coil, the inner and outer diameter, the number of coil turns, the diameter and the height of the ferrite core of the probe on the differential value of the detection signal are simulated. The parameter combination of the maximum difference value of the signal is used as the structural size of the sensor, and the detection sensor is designed and fabricated. Moreover, the bearing fatigue test system is designed, and the bearing is tested. The results show that the system has good detection ability for rolling contact fatigue and verifies the mechanism and trend of crack propagation in the inner ring of the bearing.
文摘Quality inspection is an important means to ensure that the construction quality of roads and bridges meets the standard requirements. In recent years, with the progress of science and technology, the road and bridge quality detection technology began to develop in the direction of diversification and informatization, which greatly improved the accuracy of the detection results and effectively improved the damage caused to the road and bridge structure by the traditional detection technology. On the basis of not damaging the original structure, the efficiency and quality of quality detection are improved. Based on this, this paper will analyze the application of nondestructive testing technology in road and bridge testing.
文摘In recent years, China's economic development is accelerating, the comprehensive national strength continues to improve, promote the development of China's pressure special equipment, pressure special equipment is mainly used in petrochemical and other industrial production fields. Once the pressure special equipment is damaged, it will cause non-negligible harm. About the pressure equipment, this paper first introduces some testing technologies in the field of nondestructive testing technology, and then discusses the application of nondestructive testing technology in the testing process of special pressure equipment. The selection of reasonable testing time and the comprehensive application of nondestructive testing technology are introduced in detail in order to improve the testing accuracy and contribute to the development of nondestructive testing field.
文摘For the chemical industry, the production of medium pressure vessels affects the development of the industry. Because the pressure vessel is prone to accidents if the internal pressure is too high in the production process, for a chemical enterprise, the production accident will bring the estimated loss of remedial classes. There are many reasons for accidents, most of which occur on pressure vessels. For example, the wear of pressure vessel components and improper operation of personnel will cause pressure leakage or explosion, resulting in safety accidents. Many industries need to know whether the performance of pressure vessels can meet the production standards. In this paper, various quality problems of pressure vessels on the market are analyzed and explored, hoping that some quality problems can be avoided in the production of pressure vessels, so as to reduce the occurrence of accidents and the loss of enterprises from the root. The main method discussed in this paper is to reduce the quality problems of pressure vessels with the help of nondestructive testing technology. Next, this paper introduces the distance and specific application of nondestructive testing technology in detail.
文摘Lanzhou Institute of Physics, a subsidiary of CAST, conducted ground testing on its newly developed eddy current nondestructive testing equipment, demonstrating an important breakthrough had been made with the nondestructive testing of orbital spacecraft. The equipment works steadily and has met the design requirements for space applications. It was also announced by the Institute that the equipment would be used during the next lunar exploration mission to detect the status of
基金supported by the National Key Research and Development program(Nos.2022YFA1602404,2023YFA1606901)the National Natural Science Foundation of China(Nos.12275338,12388102,and U2441221)the Key Laboratory of Nuclear Data foundation(JCKY2022201C152)xm。
文摘Energy-variable gamma-rays are produced in Laser Compton Slant-scattering mode at the Shanghai Laser Electron Gamma Source(SLEGS),a beamline of the Shanghai Synchrotron Radiation Facility(also called Shanghai Light Source).Based on the SLEGS energy-variable gamma-ray beam,a positron generation system composed of a gamma-ray-driven section,positron-generated target,magnet separation section and positron experimental section was designed for SLEGS.Geant4 simulation results show that the energy tunable positron beam in the energy range of 1–12.9 MeV with a flux of 3.7×10^(4)–6.9×10^(5)e^(+)∕s can be produced in this positron generation system.The positron beam generation and separation provide favorable experimental conditions for conducting nondestructive positron testing on SLEGS in the future.The positron generation system is currently under construction and will be completed in 2025.
文摘To scientifically evaluate the restoration performance of ancient city walls,Terahertz time-domain spectroscopy(THz-TDS)and infrared thermal imaging technology were applied to assess the Desheng Fortress(Ming Dynasty).Three representative sections were examined:adobe brick masonry repaired(Area 1),well-preserved original(Area 2),and layer-by-layer ramming repaired(Area 3).THz spectral data revealed significant differences between Area 1(time delay:3.72 ps;refractive index:2.224)and Area 2(time delay:3.02 ps;refractive index:2.107),while Area 3(time delay:3.12 ps;refractive index:2.098)demonstrated nearly identical THz spectral data to Area 2.Infrared thermal imaging also showed that the Area 3 restored by layer-by-layer ramming exhibited greater uniformity with fewer instances of cracks,capillary phenomena,or biological diseases.The proposed point-surface integrated evaluation methodology synergistically combines infrared thermography mapping of heritage surfaces with THz spectral datasets acquired through in-situ micro-sampling,enabling quantitative restoration assessment and providing a novel approach for scientifically validating traditional conservation techniques.
基金funded by the Key Project of Science&Technology Research ofChina Academy of Railway Sciences,grant number 2023YJ022.
文摘Detecting internal defects,particularly voids behind linings,is critical for ensuring the structural integrity of aging high-speed rail(HSR)tunnel networks.While ground-penetrating radar(GPR)is widely employed,systematic quantification of performance boundaries for air-coupled(A-CGPR)and ground-coupled(G-CGPR)systems within the complex electromagnetic environment of multilayer reinforced HSR tunnels remains limited.This study establishes physics-based quantitative performance limits for A-CGPR and G-CGPR through rigorously validated GPRMax finite-difference time-domain(FDTD)simulations and comprehensive field validation over a 300 m operational HSR tunnel section.Key performance metrics were quantified as functions of:(a)detection distance(A-CGPR:2.0–4.5 m;G-CGPR:≤0.1 m),(b)antenna frequency(A-CGPR:300 MHz;G-CGPR:400/900 MHz),(c)reinforcement configuration(unreinforced,single-layer,multilayer rebar),and(d)void geometry(axial length:0.1–1.0 m;radial depth:0.1–0.5 m).Key findings demonstrate:a.A-CGPR(300 MHz):Reliably detects axial voids≥0.3 m at distances≤3 m in minimally reinforced(single-layer rebar)linings(field R2=0.89).Performance degrades significantly at distances>3 m(>60%signal attenuation at 4.5 m)or under multilayer rebar interference,causing 25%–40%accuracy loss for voids<0.3 m.Optimal distance:2.0–2.5 m.b.G-CGPR(900 MHz):Achieves<5%size measurement error for axial voids≥0.1 m and radial voids≥0.2 m in unreinforced linings.Resolution degrades under multilayer reinforcement due to severe signal attenuation,increasing axial void detection error to 10%–20%for voids≥0.3 m and constraining radial size measurement.c.Synergistic Framework:A hybrid inspection protocol is proposed,integrating A-CGPR(20 km/h)for rapid large-area screening and targeted G-CGPR(3 km/h)for high-resolution verification of identified anomalies.This framework enhances NDT efficiency while reducing estimated lifecycle inspection costs by 34%compared to G-CGPR alone.This research provides the first physics-derived quantitative detection thresholds for A-CGPR and G-CGPR in multi-rebar HSR tunnels,validated through field-correlated simulations.Future work will focus on multi-frequency antenna arrays and deep learning algorithms to mitigate reinforcement interference.The established performance boundaries and hybrid framework offer critical guidance for optimizing tunnel lining inspection strategies in extensive HSR networks.
基金supported by the Zhejiang Lab Open Research Project(No.121001-AB2212)the Zhejiang Provincial Key Research and Development Program(No.2023C03186),China。
文摘Robots are used to conduct non-destructive defect detection on wind turbine blades(WTBs)and to monitor their integrity over time.However,current inspection robots are often bulky and heavy,and struggle to detect defects in the blade's main beam,thus presenting difficulties in portability and effectiveness.To address these issues,we designed a wheel-wing composite robot equipped with a curved surface-adaptive phased array ultrasonic detection device for the detection of defects in the WTB's main beam.We determined the pose equation under different section characteristics and identified the robot's stable range of motion,thus developing a model of its kinematics.A detection device adapted for variable curvature surfaces was designed to ensure tight coupling between the robot's probe and the blade.Additionally,element differential and least-square ellipse-fitting methods were employed to analyze blades with irregular sections.The simulation results demonstrated that the prototype can stably traverse an area with a vertical angle of±14.06°at a speed of 0.25 m/s,fully covering the main beam area of the blade during walking operations.Moreover,the robot can scan the main beam area at a speed of 0.10 m/s,enabling the accurate detection of defects.
基金supported by the National Science and Technology Major Project of the Ministry of Science and Technology of China(2024ZD0608100)the National Natural Science Foundation of China(62332017,U22A2022)
文摘In high-risk industrial environments like nuclear power plants,precise defect identification and localization are essential for maintaining production stability and safety.However,the complexity of such a harsh environment leads to significant variations in the shape and size of the defects.To address this challenge,we propose the multivariate time series segmentation network(MSSN),which adopts a multiscale convolutional network with multi-stage and depth-separable convolutions for efficient feature extraction through variable-length templates.To tackle the classification difficulty caused by structural signal variance,MSSN employs logarithmic normalization to adjust instance distributions.Furthermore,it integrates classification with smoothing loss functions to accurately identify defect segments amid similar structural and defect signal subsequences.Our algorithm evaluated on both the Mackey-Glass dataset and industrial dataset achieves over 95%localization and demonstrates the capture capability on the synthetic dataset.In a nuclear plant's heat transfer tube dataset,it captures 90%of defect instances with75%middle localization F1 score.
基金the financial support from Science Challenge Project of China (No. TZ2016006-0103 and No.TZ2016006-0107-02)Liao Ning Revitalization Talents Program of China (No. XLYC1807230)+2 种基金Science Fund for Creative Research Groups of NSFC (No. 51621064)the Fundamental Research Funds for the Central Universities of China (No. DUT17RC(3)105)National Natural Science Foundation of China (No. 51975096)。
文摘Residual stress is one of the main factors affecting the mechanical properties of materials, such as their strength, plasticity and surface integrity. For instance, tensile stress conditions can adversely affect material performance or component life, while compressive stress conditions can improve material fatigue strength. During the processing of integrated aviation structures, machining deformation caused by residual stress has become one of the most prominent manufacturing problems. Therefore, it is very important to measure and evaluate the stress for real applications.This paper reviews the research of residual stress measurement methods over the past five years by classifying them according to the measurement methods appearing in each stage. The existing problems and difficulties of each measurement technology are summarized, and future trends are forecasted. This paper provides a reference for further in-depth study of residual stress measurement technologies.
